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the Court of Appeal of the republic of singapore
 SGCA 5
Civil Appeal No 41 of 2020
IIa Technologies Pte Ltd
Element Six Technologies Ltd
In the matter of HC/S 26/2016
Element Six Technologies Ltd
IIa Technologies Pte Ltd
[Intellectual Property — Patents and Inventions — Claim Construction]
[Intellectual Property — Patents and Inventions — Invalidity — Insufficiency]
[Intellectual Property — Patents and Inventions — Patent specification]
[Intellectual Property — Patents and Inventions — Revocation]
This judgment is subject to final editorial corrections approved by the court and/or redaction pursuant to the publisher’s duty in compliance with the law, for publication in LawNet and/or the Singapore Law Reports.
IIa Technologies Pte Ltd
Element Six Technologies Ltd
 SGCA 5
Court of Appeal — Civil Appeal No 41 of 2020 Sundaresh Menon CJ, Judith Prakash JA, Steven Chong JA 2–4 August 2021, 20, 24–25 January 2022
17 February 2023 Judgment reserved.
Sundaresh Menon CJ (delivering the judgment of the court):
1 The parties are competitors in the production of synthetic diamonds grown using chemical vapour deposition (“CVD”). At its simplest, under this process, a substrate (which is also known as a diamond seed) is placed in a reactor containing a mixture of gases, including methane (CH4) and hydrogen (H2). Upon exposure to high energy, the gaseous molecules break up into plasma containing carbon (or “C”) atoms. The C atoms are then deposited on the substrate, growing the synthetic diamond layer by layer.
Foot Note 1
Primer at para 3(b).
2 The appellant, a company incorporated in Singapore, claims to be a major manufacturer of CVD diamonds and has a diamond-growing facility in Singapore.
Foot Note 2
See Appellant’s Case (“AC”) at para 2; Mr Meta Visha Jatin’s AEIC at para 17 (III(B01) ROA 7).
The respondent, a company incorporated in the United Kingdom, is part of the Element Six Group. The Element Six Group is a member of the De Beers Group, which is itself a subsidiary of the Anglo American PLC.
Foot Note 3
Ms Susan Jane Fletcher Watts’ AEIC at paras 4–5 (III(A1) ROA 7–8).
The De Beers Group is an international diamond business and a diamond producer, while the Anglo American PLC is a global mining company. According to the respondent, the Element Six Group is a global leader in the design, development and production of “synthetic diamond supermaterials”.
Foot Note 4
Ms Susan Jane Fletcher Watts’ AEIC at para 5 (III(A1) ROA 8).
The respondent claims that its CVD diamonds have potential technical applications in various industries, including optics, semiconductors and sensors.
Foot Note 5
Ms Susan Jane Fletcher Watts’ AEIC at para 7(b) (III(A1) ROA 9).
3 In HC/S 26/2016 (“Suit 26”), the respondent claimed that the appellant had infringed two of its patents registered in Singapore, Singapore Patent No 115872 (“SG 872”) and Singapore Patent No 110508 (“SG 508”). To prove infringement, the respondent relied on three samples of diamonds, which were labelled Sample 2, Sample 3 and Sample 4 (collectively, the “Samples”), allegedly purchased from the appellant or the appellant’s related entities or distributors. It claimed that the Samples were made from CVD diamond material synthesised by the appellant and that the appellant must have used the method of growth taught in Claims 62 to 71 of SG 872.
Foot Note 6
Particulars of Infringement (Amendment No 2) at para 4 (II(1) ROA 35–44).
In its defence, the appellant denied infringing the patents and, in any case, disputed their validity.
Foot Note 7
Defence & Counterclaim (Amendment No 6) at paras 5–6 (II(1) ROA 26 and 69).
The appellant also sought the revocation of both patents by way of a counterclaim.
Foot Note 8
Defence & Counterclaim (Amendment No 6) at (3) and (7) (II(1) ROA 73).
On 7 February 2020, the trial judge (the “Judge”) declared that SG 508 was invalid and revoked it on the basis that it was neither novel nor inventive (Element Six Technologies Ltd v IIa Technologies Pte Ltd  SGHC 26 (“Judgment”) at  and [478(d)]–[478(e)]). This was a complete defence to the respondent’s claim for infringement in so far as SG 508 was concerned (Judgment at ). However, the Judge found that SG 872 was valid and declined to revoke it. She further found that the appellant had infringed specific claims in SG 872. In this appeal, although both parties proceeded on the basis that Claims 1ii), 1iii), 57, 58 and 62 of SG 872 were infringed,
Foot Note 9
AC at para 3; Respondent’s Case (“RC”) at para 5(e).
it is not entirely clear whether the Judge confined her finding of infringement to specific limbs of Claim 1 (Judgment at , , , ,  and [478(a)]). But this difficulty need not detain us. Even taking Claims 1ii) and 1iii) as the point of departure for our analysis on invalidity, our conclusions affect the entirety of Claim 1 and the outcome of the appeal will not change even if the Judge had found the whole of Claim 1 to be infringed.
4 On 6 March 2020, the appellant filed CA/CA 41/2020 (“CA 41”) appealing against the Judge’s rejection of its defence that SG 872 is invalid and its counterclaim to revoke the entirety of SG 872. It also challenged the Judge’s finding that Claims 1ii), 1iii), 57, 58 and 62 in SG 872 had been infringed.
Foot Note 10
See Notice of Appeal in CA/CA 41/2020 dated 6 March 2020; AC at para 3.
The respondent has not cross-appealed against the Judge’s findings in respect of SG 508.
5 The Judge delivered her decision on costs (the “Judge’s Costs Decision”) on 30 March 2020, holding that the respondent was entitled to the costs of Suit 26 on a standard basis as well as costs of $3,000 (all in) for the costs hearing which took place on 30 March 2020. On 25 June 2020, the appellant filed CA/CA 96/2020 (“CA 96”) appealing against the entirety of the Judge’s Costs Decision.
6 This judgment deals only with CA 41.
Procedural history and case management on appeal
7 On 17 August 2020, the appellant filed CA/SUM 87/2020 (“SUM 87”), seeking leave to admit further evidence from Dr Werner Kaminsky (“Dr Kaminsky”, the appellant’s expert) for the purpose of challenging the evidence of Dr Anthony Michael Glazer (“Dr Glazer”, the respondent’s expert) on his gap theory (“Gap Theory”) (see  below for relevance of the Gap Theory in this appeal). We dismissed SUM 87 on 16 September 2020.
8 As appears below, the technical background to SG 872 – including the physical properties of diamonds, how SG 872 seeks to enhance the quality of CVD diamonds grown and the measurement or evaluation of the improvement brought about by SG 872 – is highly complex. The following steps greatly assisted us in coming to grips with the difficult material:
(a) On 19 April 2021, we directed the parties to prepare a “Primer” (with a 50-page limit) setting out their points of agreement and divergence on topics including the common general knowledge (such as different methods of growing diamonds and types of defects in diamonds), the state of the art (including other patents) and the inventive concept of SG 872.
(b) We also convened a “Technology Tutorial” that was conducted on 2, 3 and 4 August 2021. Each party was allowed to nominate up to two presenters from among their expert witnesses to address these topics as well as provide an introduction to SG 872 and the Metripol system.
Foot Note 11
Court’s letter dated 19 April 2021 at para 5, read with Appellant’s letter dated 13 April 2021, p 4 s/n 4.
The parties filed and exchanged Powerpoint slide decks prepared by their presenters seven days before the Technology Tutorial.
In the section that follows, we outline the salient aspects of the background to SG 872 as presented in the Primer and Technical Tutorial, which will set the context for our analysis of its validity.
9 Following the Technology Tutorial, CA 41 was heard over three half-day hearings on 20, 24 and 25 January 2022.
10 Subsequently, on 14 September 2022, we wrote to the parties to clarify whether each product claim in SG 872 covers a class of products as opposed to an individual product. The significance of this point, as well as of the parties’ responses on 21 September 2022, will become clear when we analyse whether SG 872 should be revoked in its entirety.
11 We first set out the technical background to SG 872. As we later elaborate, SG 872 discloses a new single crystal CVD diamond material, at least 0.5mm in thickness, which possesses one or more properties stated in the patent. One such property is low “optical birefringence” (henceforth referred to as “birefringence”). It is the respondent’s case that without the new CVD growth process taught within SG 872, the single crystal CVD diamond material manufactured would not display the properties defined in the product claims of SG 872. It is said that these properties are indicative of a high-quality diamond.
Foot Note 12
RC at para 12.
Synthetic diamonds and CVD
12 Diamonds are a form of solid C (meaning carbon) in which each C atom is bonded to four neighbouring C atoms to form a tetrahedral structure. Many of these tetrahedral structures come together to form a diamond lattice. A “single crystal” diamond, which is claimed in SG 872, is one in which the crystal lattice of the entire sample is continuous and unbroken. In contrast, a polycrystalline diamond consists of many single crystals.
Foot Note 13
RC at para 13; Dr Mark Edward Newton’s 1st Report (“Newton-1”) at p 34 (I RSCB 133); Primer at para 80; Transcript, 3 August 2021, p 20:26-27 (Dr Newton).
13 Diamonds may form naturally within the Earth’s crust or be manufactured in a laboratory.
Foot Note 14
Primer at paras 2–3.
CVD is one of the main ways of manufacturing diamonds, the other of which involves applying high-pressure-high-temperature (“HPHT”) on a C source mixed with a catalyst.
Foot Note 15
Primer at para 3(a).
Impurities, defects and strain in diamonds
14 In reality, no diamond (natural or man-made) is an array of equally spaced atoms which are purely C. Diamonds will contain impurities and defects. We make this point to provide context to what the respondent/patentee sought to achieve through the new growth processes taught in SG 872. As will become clear, the type and extent of defects in a diamond bear on its physical properties, such as its strength,
Foot Note 16
See, eg, Primer at para 52.
and hence its potential industrial use(s) and application(s). The respondent sought to produce CVD single crystal diamonds with certain qualities which were required for specific industrial applications. Allegedly, such diamonds could only be produced using the processes claimed in SG 872. What follows elaborates on the nature of defects or impurities arising in diamonds and the relationship between these imperfections and a diamond’s physical properties.
15 Impurities refer to non-C atoms bonded into the diamond’s lattice structure. Common impurities include nitrogen (N2) and boron. The concentration of nitrogen and boron is expressed in parts per million (“ppm”) or parts per billion (“ppb”).
Foot Note 17
Primer at para 4.
Based on its purity, a diamond can be categorised into two main types: Type I and Type II. These can be further sub-divided into Types Ia, Ib, IIa and IIb. Type I diamonds contain relatively large amounts of nitrogen – up to 0.3% (5ppm to ~ 3000ppm). Most of the nitrogen atoms in Type Ia diamonds are found in clusters, but this is not the case in Type Ib diamonds.
Foot Note 18
Primer at para 7.
Type II diamonds contain nitrogen below 5ppm. The only impurity in Type IIa diamonds is nitrogen, whereas impurities in Type IIb diamonds consist of nitrogen and boron.
Foot Note 19
Primer at para 8.
16 When impurities (meaning non-C atoms) enter the diamond’s structure, a point defect is created in the lattice structure.
Foot Note 20
Primer at para 18.
Extended defects, on the other hand, are structural defects caused by disruptions to the diamond lattice that extend across the crystal.
Foot Note 21
Primer at para 19.
One example of an extended defect is a stacking fault, which occurs where the relative positioning of two adjacent layers (or planes) of crystal structure does not conform with the rest of the crystal:
Figure 1: Diagram depicting stacking faults
Another type of extended defect is a dislocation. Dislocations occur where there are atoms out of position in the crystal structure that, among other things, form an extra line of atoms within the structure (that is, an edge dislocation):
Foot Note 22
Primer at para 19.
Figure 2: Diagram depicting dislocations
17 Extended defects can be visualised using X-ray topography images where stacking faults appear as dark planes (Figure 3) and dislocations appear as dark lines (Figure 4). Thicker and relatively darker lines show bundles of dislocations:
Foot Note 23
IV ACB 164.
Figure 3: 2-D X-ray topography of IIa HPHT diamond showing stacking faults (black areas) (from H Sumiya et al, “Crystalline perfection of high purity synthetic diamond crystal” (1997) 178 Journal of Crystal Growth 485 at 490)
Figure 4: X-ray topography of CVD diamond showing dislocations as black lines (from I Friel et al, “Control of surface and bulk crystalline quality in single crystal diamond grown by chemical vapour deposition” (2009) 18 Diamond & Related Materials 808 at 812)
18 Dislocations cause strain, or distortion to the position of atoms, in the diamond structure.
Foot Note 24
See Transcript, 2 August 2021, p 12:6–7.
The strain extends across the full length of the dislocation, which typically runs all the way across the diamond.
Foot Note 25
Primer at paras 22 and 40.
Strain weakens the chemical bonds, which then can be broken with lower energy. This reduces the strength of the diamond to withstand external pressure.
Foot Note 26
Primer at para 22.
According to Dr Christoph Erwin Nebel (“Dr Nebel”), the appellant’s principal expert,
Foot Note 27
AC at para 11.
if there is strain, electrons between the atoms are no longer homogenously distributed, resulting in an electric field that may interact with light and increase birefringence in the diamond (a property we explore in some detail at – below).
Foot Note 28
Transcript, 2 August 2021, p 12:3–11.
19 Dislocation density refers to the number of dislocations per square cm or mm of surface. Dislocations extend across the diamond like a line (hence, “line defects”) and terminate only on the surface:
Foot Note 29
Primer at para 29.
Figure 5: Dislocations originate from the substrate surface and propagate into the diamond. They can multiply during growth and become decorated with nitrogen.
Dislocation termination points reveal themselves as etch pits. An optical evaluation of the number of etch pits across the surface area of the diamond will reveal its dislocation density:
Figure 6: Etch pits on diamond with dislocation density of 3300/mm2
Figure 7: Cross-section of an etch pit
20 Birefringence is a physical property of diamonds relevant to the key claims in SG 872. We shall therefore explore this concept in some detail.
21 Birefringence, stated generally, is related to how light interacts with a certain object. Light is made of waves of electric and magnetic fields. These waves oscillate in all directions perpendicular to the direction of the transmission of light. The distance travelled when an electromagnetic wave goes through one full oscillation cycle is called wavelength, which is denoted by λ. The wavelength of light determines its colour.
Foot Note 30
Primer at para 33.
Figure 8: Diagram of a light wave in terms of its electro-magnetic field
22 While normal light consists of electric fields oscillating in all directions in the plane perpendicular to the direction of propagation, a polariser filter may be used to only allow light containing electric fields oscillating in a single direction to pass through. “Polarised light” therefore has only one direction of oscillation.
Foot Note 31
Primer at para 35.
23 The atomic arrangement in a material affects the speed at which light travels through it. The speed of light in an optical material is determined by the material’s refractive index. The denser the material, the higher its refractive index and the slower that light travels through it.
Foot Note 32
Primer at para 36.
24 Where the internal structure of the crystalline material is perfect, in that it has no impurities or defects, the crystalline material is highly symmetrical. Such material is referred to as isotropic. In isotropic materials, the refractive index is the same in all directions. This means that light passes through an isotropic crystal at a single velocity.
25 But for anisotropic materials, the refractive index may vary in different directions. Although a diamond may theoretically be isotropic due to its highly symmetrical uniform lattice of C atoms, in reality, diamonds are anisotropic due to strain caused by dislocations.
Foot Note 33
Primer at para 37.
When polarised light is passed through a diamond with strain, the light splits into two relevant components which travel at different velocities. One component travels faster along the path in the material with the smallest refractive index (n”) and the other travels slower along the path in the material with the largest refractive index (n’). The difference between the smallest and largest available refractive index is called birefringence (Δn = |n’ – n’’|).
Foot Note 34
Primer at para 38.
In other words, strain in diamonds results in birefringence.
Foot Note 35
Primer at para 40; Transcript, 3 August 2021, p 29 (Dr Newton).
26 The gap between the faster and slower components of light when they emerge out of the material is defined as the optical retardation (also referred to as “retardation” or “path difference”). Light of any wavelength which passes through a sample of an anisotropic material having birefringence Δn, where the sample has a thickness of “L”, will display retardation of L·Δn. Dr Nebel depicted birefringence and retardation as follows:
Foot Note 36
Dr Christoph Erwin Nebel’s technical tutorial (“Dr Nebel’s technical tutorial”), slide 15.
Figure 9: Diagram showing how the variation in the refractive index causes birefringence
27 For light of a particular wavelength (or λ), retardation can also be represented as phase shift “δ”:
Foot Note 37
Primer at para 39.
Dr Nebel represented the components of the above equation, using the following diagrams of light components that have split up when passing through an object:
Foot Note 38
Dr Nebel’s technical tutorial, slide 17.
Figure 10: Diagrammatic representation of retardation as a “phase shift”
Salient features of SG 872
28 This appeal concerns SG 872, which was filed on 20 November 2003. In essence, the patent covers a new optical quality synthetic single crystal CVD diamond material and the method for its production.
Foot Note 39
Statement of Claim (Amendment No 2) at para 2 (II(1) ROA 27).
The patent contains both product and process claims. A product claim is one which “asserts exclusive rights over a new thing, such as new machines, items or articles of manufacture and composition of matter”. Although the patentee may describe only one use of his invention, he has the right to stop others from using it for other purposes (Susanna H S Leong, Intellectual Property Law of Singapore (Academy Publishing, 2013) (“Susanna Leong”) at para 18.002). We will henceforth refer to a diamond falling within any of the product claims in SG 872 as an “SG 872 Diamond”. On the other hand, “a process claim covers a new activity such as a process or method of manufacturing and logically, in a method or process claim, it is the process used and not the end result which must be new to justify patentability.” (Susanna Leong at para 18.003).
29 The pivotal product claim, which all subsequent claims refer back to, is Claim 1:
1. A CVD single crystal diamond material which shows at least one of the following characteristics, when measured at room temperature (nominally 20oC):
i) a high optical homogeneity, with the transmitted wavefront differing from the expected geometrical wavefront during transmission through diamond of a specified thickness of at least 0.5 mm, processed to an appropriate flatness and measured over a specified area of at least 1.3 mm x 1.3 mm, by less than 2 fringes, where 1 fringe corresponds to a difference in optical path length equal to ½ of the measurement wavelength of 633 nm;
ii) a low optical birefringence, indicative of low strain, such that in a sample of a specified thickness of at least 0.5 mm and measured in a manner described herein over a specified area of at least 1.3 mm x 1.3 mm, the modulus of the sine of the phase shift, |sin δ|, for at least 98% of the analysed area of the sample remains in first order (δ does not exceed π/2) and the |sin δ| does not exceed 0.9;
iii) a low optical birefringence, indicative of low strain, such that in a sample of a specified thickness of at least 0.5 mm and measured in a manner described herein over a specified area of at least 1.3 mm x 1.3 mm, for 100% of the area analysed, the sample remains in first order (δ does not exceed π/2), and the maximum value of Δn[average], the average value of the difference between the refractive index for light polarised parallel to the slow and fast axes averaged over the sample thickness, does not exceed 1.5 x 10-4;
iv) an effective refractive index in a sample of specified thickness of at least 0.5 mm, measured in a manner described herein over a specified area of at least 1.3 mm x 1.3 mm, which has a value of 2.3964 to within an accuracy of +/-0.002;
v) combination of optical properties such that when the diamond material is prepared as a diamond plate in the form of an etalon of a specified thickness of at least 0.5 mm and measured using a laser beam with a wavelength near 1.55 μm and a nominal diameter of 1.2 mm over a specified area of at least 1.3 mm x 1.3 mm, it exhibits a free spectral range (FSR) which, when measured at different positions over the plate, varies by less than 5 x 10-3 cm-1;
vi) a combination of optical properties such that when the diamond material is prepared as a diamond plate in the form of a Fabry-Perot solid etalon of a specified thickness of at least 0.5 mm, and measured using a laser beam with a wavelength near 1.55 μm and a nominal diameter of 1.2 mm over a specified area of at least 1.3 mm x 1.3 mm, and which has no coatings applied to the optically prepared surfaces, it exhibits when measured at different positions over the plate a contrast ratio exceeding 1.5;
vii) a combination of optical properties such that when the diamond material is prepared as a diamond plate in the form of an etalon of a specified thickness of at least 0.5 mm, and measured using a laser beam with a wavelength near 1.55 μm and a diameter of 1.2 mm over a specified area of at least 1.3 mm x 1.3 mm, it exhibits an insertion loss not exceeding 3 dB;
viii) a variation in refractive index over a volume of interest, said volume comprising a layer of a specified thickness of at least 0.5 mm, measured in a manner described herein over a specified area of at least 1.3 mm x 1.3 mm, which is less than 0.002.
30 Single crystal CVD diamond material falling within Claim 1 has low strain and exhibits at least one of the optical properties defined in the eight limbs of Claim 1.
Foot Note 40
Primer at para 140.
Two of these limbs, limbs ii) and iii), assume significance in this dispute. Following the terminology used by the parties and the Judge, we will refer to these two limbs as “Claim 1ii)” and “Claim 1iii)” respectively. As the respondent pleads that Claims 1ii) and 1iii) were infringed (see Judgment at ),
Foot Note 41
Particulars of Infringement (Amendment No 2) dated 26 October 2018 at para 1 (II(1) ROA 31–32).
we elaborate on these. Claims 1ii) and 1iii) assert a monopoly over single crystal CVD diamond material with low birefringence. Low birefringence is quantified in Claim 1ii) as a sample (a) remaining in the first order (δ does not exceed ); and (b) with the modulus of the sine of the phase shift (that is, |sin δ|) not exceeding 0.9. Low birefringence is quantified in Claim 1iii) as a sample (a) remaining in the first order (δ does not exceed ); and (b) with the maximum value of Δn[average] (that is, the average birefringence across the thickness of the sample) not exceeding 1.5 x 10-4.
31 We highlight four key points pertaining to Claims 1ii) and 1iii) which the parties do not dispute. First, the term “first order” for the purposes of SG 872 (and Claims 1ii) and 1iii) in particular) has been defined in a specific way. The parties’ experts, when explaining certain technical concepts (see above at  and below at ),
Foot Note 42
See also Primer at para 47.
referred to each “order” as a multiple of 2π, with “first order” covering a range of values where δ does not exceed 2π (or again, expressed as an equation, δ ≤ 2π). However, SG 872 defines “first order” in a much more limited sense, namely, where δ does notexceed (or again, expressed as an equation, δ ≤ ) (the “SG 872 First Order”).
Foot Note 43
Primer at paras 155–156; see Bundle of Materials dated 28 June 2021 (“BOM”) at p 363.
32 Second, it is undisputed that SG 872 directs the person skilled in the art (“PSA”) to use a Deltascan (which has been renamed as the Metripol since 2001)
Foot Note 44
Primer at para 146; Dr Nebel’s technical tutorial, slide 66.
or a “similar instrument with similar resolution” to determine the value of |sin δ| and Δn[average].
Foot Note 45
BOM at pp 302 and 308. Primer at para 146.
The Metripol is an optical microscope-based imaging system,
Foot Note 46
Primer at para 146.
which was developed by Dr Glazer (the respondent’s expert), Dr Kaminsky (the appellant’s expert), and Dr Morten Geday (“Dr Geday”) (the appellant’s witness) in or around 1995. The Metripol has a polariser that rotates in fixed multiples of different angles (for example, by 30o, 60o, 90o) (“Rotation Angles”). At each angle, polarised light passes through the specimen and is captured by a camera. The Metripol calculates the intensities of light received by the camera at different Rotation Angles, and thereafter computes |sin δ|, which is a function of δ.
33 It will be recalled that δ is the optical retardation of light of a particular wavelength that passes through a material, and is related to the birefringence of the material by the formula set out at  above.
Foot Note 47
Primer at para 150.
As appears from the three graphs below (in particular, the green arrows in graphs (b) and (c)), |sin δ| is the amplitude of a sinusoidal curve (meaning half the distance from the highest point of the curve to its lowest point). This sinusoidal curve is derived by plotting the intensity of polarised light that passes through the diamond specimen on the y-axis, against the polariser’s Rotation Angle on the x-axis.
Foot Note 48
Primer at para 151.
Depending on whether and the extent to which the intensity of light varies when the polariser is angled differently, |sin δ| will assume a different value:
Foot Note 49
Dr Nebel’s technical tutorial, slide 68; see also Primer at para 151.
Figure 11: Graphs depicting the variation of intensities of light against the polariser’s Rotation Angle
34 Third, after computing |sin δ|, the Metripol produces colour-coded images of the material, where the different colours represent different |sin δ| values at any place within the image (the “Metripol |sin δ| Map”).
Foot Note 50
Primer at para 147.
The Metripol is capable of refining the |sin δ| value at each pixel position in the Metripol |sin δ| Map.
Foot Note 51
Primer at para 157.
An illustration of the Metripol |sin δ| Map can be found in the following diagram, taken from the respondent’s Technology Tutorial slides:
Figure 12: Illustration of a colour-coded image produced by the Metripol (that is, the Metripol |sin δ| Map)
The same Metripol |sin δ| Map can also be represented in greyscale. The patent specification of SG 872 states that the spatial variation of |sin δ| can be appreciated from these images.
Foot Note 52
See BOM at p 330.
The patent specification also states that for each sample, sets of |sin δ| images are to be recorded for analysis.
Foot Note 53
BOM at p 331.
35 Fourth, it is agreed between the parties that the Metripol data on its own does not tell the PSA whether the δ value of a diamond falls within the SG 872 First Order (the “Metripol Uncertainty Problem”).
Foot Note 54
Primer at paras 154–155.
The Metripol does not calculate δ. As mentioned, it generates the value of |sin δ|.
Foot Note 55
Primer at para 152.
However, each |sin δ| value corresponds to many δ values, and only one of these δ values lies within the SG 872 First Order.
Foot Note 56
Primer at para 153 and Figure 44.
From the |sin δ| value alone, the PSA cannot derive a corresponding δ value and will not know whether the δ value of a diamond is within or outside the SG 872 First Order. This point can be illustrated in Figure 13 below, where δ1 is the value that lies within the SG 872 First Order:
Foot Note 57
Primer at para 152.
Figure 13: Graph showing that |sin 𝛿| of 0.9 may indicate multiple possible values of 𝛿
If the Metripol shows that the |sin δ| value of the diamond is 0.9, the corresponding δ value can be 1.12, 2.02, 4.26, 5.16, or any other higher value not reflected in Figure 13 above.
Foot Note 58
Primer at para 153 and Figure 44.
δ will only be within the SG 872 First Order if it has a value of 1.12, as that is the only value that does not exceed (see above at ). The rest of the values lie outside the SG 872 First Order. From this range of possible δ values, the PSA relying solely on the Metripol reading cannot determine the δ value of the diamond, and accordingly, cannot ascertain whether δ is within the SG 872 First Order.
36 In this appeal, as they did in the proceedings below, the parties diverge on the issue of whether the PSA knew of solutions to overcome the Metripol Uncertainty Problem at the relevant time. The thrust of the appellant’s contention is that the PSA, faced with the Metripol Uncertainty Problem and with no knowledge of any workable solution at the relevant time, would not be able to determine whether the δ value of the diamond was within the SG 872 First Order and hence within the scope of the asserted monopoly. For this reason, the appellant contends that SG 872 is insufficient.
Foot Note 59
AC at paras 151–211; Defendant’s Closing Submissions in Second Tranche of Trial (“DCS2”) at paras 307 and 311–347 (III(G5) ROA 149–151 and 152–169).
In turn, the respondent’s case is that the PSA would have no difficulty ascertaining that the δ value of the diamond was within the SG 872 First Order by using various methods, such as the Gap Theory proposed by Dr Glazer.
Foot Note 60
RC at paras 175–194; Plaintiff’s Closing Submissions in Second Tranche of Trial (“PCS2”) at paras 898–906 (III(G3) ROA 130–134).
We will deal with this issue in our analysis later.
37 We now turn to Claim 62, the main process claim in SG 872 to which all other process claims in SG 872 refer. Claim 62 specifies a method of producing low-strain single crystal CVD diamond material that exhibits optical properties defined in the product claims in SG 872. Claim 62 states as follows:
62 A method of producing a CVD diamond material suitable for optical applications and according to any one of the preceding claims, which method includes the steps of:
- providing a substrate substantially free of crystal defects,
- providing a source gas,
- dissociating the source gas to produce a synthesis atmosphere which contains 300 ppb to 5 ppm nitrogen, calculated as molecular nitrogen, and allowing homoepitaxial diamond growth on the surface which is substantially free of crystal defects
wherein the surface damage of the substrate is minimised by including a plasma etch on the surface on which homoepitaxial diamond growth is to occur, whereby a density of defects at the surface of the substrate is such that surface etch features related to the defects is below 5 x 103/mm2,
wherein the level of nitrogen is controlled with an error of less than 300 ppb (as a molecular fraction of the total gas volume) or 10% of the target value in the case phase, whichever is the larger, and
wherein the level of nitrogen is selected to be sufficient to prevent or reduce strain generating defects whilst being low enough to prevent or reduce deleterious absorptions and crystal quality degradation, thereby producing a CVD single crystal diamond material meeting the requirements of one or more of claims 1 to 61.
38 Certain terms relating to the growth process, which are referred to subsequently, call for further explanation. The “source gas” in the CVD chamber comprises several gases, including a “C” source which is typically methane (CH4) and a source of atomic hydrogen which is typically hydrogen (H2). The parties agree that other gases, such as an inert gas (like argon) and a dopant gas (like nitrogen, boron or phosphorous), a source of impurities which is used to affect the electrical or optical properties of a diamond, are also used dependingon the desired characteristics of the CVD diamond.
Foot Note 61
Newton-1 at para 236 (IIIA(24) ROA 171); Dr Newton’s 2nd Report (“Newton-2”) at para 155 (IIIA(56) ROA 74); Dr Nebel’s 2nd Report (“Nebel-2”) at para 117 (IIIB(62) ROA 63); Primer at para 96.
Each input gas is controlled by a mass flow controller (“MFC”). The flow of gases across MFCs is measured as cubic centimetres of gas flowing through the MFC per minute (expressed as standard cubic centimetres per minute or “sccm”). The concentration of each gas is represented as a percentage, ppm or ppb.
Foot Note 62
Primer at para 97.
As for the “plasma etch” performed on the substrate prior to the commencement of the CVD process, this involves “exposing the substrate to a plasma formed by hydrogen (H2) and/or oxygen (O2) at high temperature in a CVD chamber.”
Foot Note 63
Primer at para 92.
The specification of SG 872 states that such in situ plasma etching minimises the surface damage of the substrate.
Foot Note 64
BOM at p 317.
We note, however, that the respondent disputes
Foot Note 65
RC at para 150.
whether the use of a plasma etch to achieve this effect is common general knowledge to a PSA (we will explain the concepts of common general knowledge and the PSA at – below).
39 The respondent claims that the production of low-strain single crystal CVD diamond material disclosed in Claims 1 to 61 and 72 to 78 was not possible prior to the discovery of the process in Claim 62.
Foot Note 66
Transcript, 4 August 2021, p 38:11–20.
The respondent argues that the growth process in Claim 62, specifically, the addition of 300ppb to 5ppm nitrogen to the synthesis atmosphere (the “Claim 62 Nitrogen Range”), is novel because it runs contrary to previous thinking that adding nitrogen to the synthesis atmosphere would have a deleterious effect on the quality of the diamond produced; nitrogen was regarded as an impurity.
Foot Note 67
RC at para 18.
As the Judge noted, the common general knowledge at the material time was that the addition of nitrogen would increase birefringence. The Claim 62 Nitrogen Range is therefore the inventive concept asserted in Claim 62 (see Judgment at ). We agree. According to the specification of SG 872, the Claim 62 Nitrogen Range is not too high because it accomplishes the aim of “prevent[ing] or reduc[ing] local strain generating defects whilst being low enough to prevent or reduce deleterious absorptions and crystal quality degradation.”
Foot Note 68
BOM at p 310.
Nor is the range too low, because, according to SG 872, “material grown under conditions with essentially no nitrogen, or less than 300ppb nitrogen has a comparatively higher level of local strain generating defects”.
Foot Note 69
BOM at p 312.
Dr Philippe Bergonzo (“Dr Bergonzo”), one of the respondent’s experts, depicted the benefits of operating within the Claim 62 Nitrogen Range as follows (see the curve in black):
Foot Note 70
Dr Philippe Bergonzo’s technical tutorial slides, slide 41.
40 As against this, the appellant regards the purported benefits of using the Claim 62 Nitrogen Range as “illusory” and “false”.
Foot Note 71
AC at paras 131–132.
It questions why, in the 17 or so years since SG 872, not a single paper has been published discussing or evidencing this discovery. However, as we shall explain, even assuming that the purported benefits of the Claim 62 Nitrogen Range are scientifically true, there are other issues undermining the validity of the patent.
41 Against the appellant’s arguments to the contrary, the Judge held that Claims 1 and 62 of SG 872 were valid. For brevity, we will only summarise the Judge’s reasons for rejecting the appellant’s contentions on insufficiency, and only in so far as they are relevant to the determination of this appeal.
42 The Judge observed that the appellant had relied on s 25(5) of the Patents Act (Cap 221, 2005 Rev Ed) (“Patents Act (2005 Rev Ed)”),
Foot Note 72
The version as at 30 April 2014.
which provided that claims shall be “clear and concise” in s 25(5)(b). Citing this court’s decision in First Currency Choice Pte Ltd v Main-Line Corporate Holdings Ltd and another appeal  1 SLR(R) 335 (“First Currency Choice”)at , the Judge held that the requirement of clarity was not a ground for revocation under the Patents Act (2005 Rev Ed). She emphasised that what was important was whether the invention has been disclosed sufficiently for a PSA to perform it (Judgment at –), and proceeded to consider the appellant’s contentions on why Claim 1 was insufficient. One of these contentions was that Claim 1 of SG 872 was insufficient because the Metripol could not identify whether δ was within the SG 872 First Order (Judgment at –). She eventually rejected that contention because she accepted Dr Glazer’s evidence that the PSA would know how to determine whether δ was within the SG 872 First Order using the Gap Theory (Judgment at –).
43 The Judge also found that Claim 62 had sufficiently disclosed the claimed invention. The appellant argued that the PSA would not know how to calibrate the other growth conditions to the chosen nitrogen concentration to grow an SG 872 Diamond.
Foot Note 73
DCS2 at para 428 (III(G6) ROA 10).
The Judge rejected this submission given Dr Bergonzo’s evidence that the missing details would be known to a PSA with a working knowledge of the research and development of CVD diamond synthesis (Judgment at ).
44 Another of the appellant’s submissions was that the insufficiency of Claim 62 was demonstrated by how the single crystal CVD diamond material grown in Examples 1 and 14 of SG 872 as well as Examples 4 and 6 of SG 508 had different qualities, even though these examples disclosed a growth process where the synthesis atmosphere had 300ppb to 5ppm nitrogen. The Judge rejected this submission, noting that the respondent had explained that the difference in other parameters of the growth process (such as gas flow and methane concentration in the synthesis atmosphere) between SG 508 and SG 872 resulted in a diamond with different qualities being grown. She also observed that these other parameters did not, in any event, constitute the inventive concept of SG 872 (Judgment at –).
45 Given her finding that Claims 1 and 62 of SG 872 were valid, the Judge did not revoke SG 872 and proceeded to find that both Claims 1 and 62 had been infringed (Judgment at ). In particular, she found that the Samples infringed Claim 1 on the basis that they fulfilled limbs ii) and iii) of Claim 1 (Judgment at –). The Judge therefore made the following orders, amongst others (Judgment at [478(a)]–[478(c)]):
(a) a declaration that SG 872 is valid and has been infringed;
(b) an injunction to restrain the defendant, whether by themselves, their directors, officers, servants, agents from (a) making, disposing of, offering to dispose of, using, importing and/or keeping products which infringe SG 872, and/or (b) using or offering for use in Singapore processes which infringe SG 872; and
(c) an order for the delivery up and/or destruction, to be verified upon oath, of all products or articles which infringe SG 872.
The parties’ cases
46 The appellant’s attack on the Judge’s decision cuts across many areas of patent law, such as novelty, inventive step, and sufficiency. Much reliance has also been placed on concepts recognised in English law which have not been recognised locally, such as “Biogen insufficiency”. For the purposes of the present appeal, we only need to focus on two parts of the appellant’s case, both of which concern the non-fulfilment of the sufficiency requirement and are determinative of this appeal.
47 The first relates to the insufficiency of Claim 62 on the basis that the patent specification fails to teach the “novel” growth process clearly and completely enough for it to be performed by a PSA. In particular, the appellant faults Claim 62 for not disclosing “what ranges of temperature, gas flow rate or methane concentration will give diamond material within claim 1iii) or any other product claims for that matter.”
Foot Note 74
Appellant’s Reply (“AR”) at paras 44 and 52.
We shall refer to these variables, and any other variables in the patented CVD growth process (other than the concentration of nitrogen), as the “Other Growth Conditions”. The appellant argues that it is not enough to point to the examples in SG 872 because these “do not support a claim of the breadth of claim 62.”
Foot Note 75
AR at paras 46 and 50.
As a result, the PSA is “left with a long and extensive research project to find out what ranges of these other process parameters are required to obtain claim 1iii) or 1ii) diamond material” and that, therefore, SG 872, is insufficient.
Foot Note 76
AR at para 52; Appellant’s Counsel’s Note (“ACN”) at para 11(e).
48 The appellant contends that the respondent’s own arguments under novelty establish insufficiency. Relevantly, the respondent argues that Examples 4 and 6 of SG 508, which teach the use of 2.5ppm and 3.8ppm of nitrogen in the synthesis gas mixture respectively, do not anticipate SG 872 because there are “a lot of differences” in terms of gas flow, temperature and methane concentration between those examples and Claim 62.
Foot Note 77
RC at paras 95–97.
The respondent asserts on this basis that Examples 4 and 6 in SG 508 do not anticipate Claim 62 because following those examples will not inevitably lead to the production of an SG 872 Diamond.
Foot Note 78
RC at para 98.
But if this is correct, the appellant points out that it must mean “there are other ranges of essential parameters for the process in SG 872 to ‘work’” and that their omission from Claim 62 or the specification of SG 872 means that the invention is insufficiently disclosed.
Foot Note 79
AR at para 46.
49 Before proceeding further, we note the respondent’s submission that pursuant to O 57 r 9A(5B) of the Rules of Court (2014 Rev Ed), the appellant cannot impugn the clarity and completeness of SG 872 as this ground of insufficiency is not particularised in the Appellant’s Case (the “O 57 Objection”).
Foot Note 80
Respondent’s skeletal arguments (“RSA”) at para 38.
Notwithstanding the respondent’s contentions, we are inclined to consider the appellant’s arguments on this issue (see Oxley Consortium Pte Ltd v Geetex Enterprises Singapore (Ptd) Ltd and another matter  2 SLR 782 at ; Global Yellow Pages Ltd v Promedia Directories Pte Ltd and another matter  2 SLR 185 at ). Although the Appellant’s Case focused on another type of insufficiency that we will turn to next, it foreshadowed the possibility of other insufficiency arguments arising “depending on how the Respondent trie[d] to avoid invalidity.”
Foot Note 81
AC at para 148.
And in its Reply, the appellant developed its submissions on this point in direct response to the Respondent’s Case. The respondent also did not press the O 57 Objection in oral submissions and instead dealt substantively with the appellant’s arguments in question.
Foot Note 82
See, eg, Transcript, 24 January 2022, p 50:9–19.
There is therefore no procedural impropriety afoot and/or prejudice to the respondent that precludes the appellant from relying on this ground of insufficiency.
50 The second part of the appellant’s case which we will focus on concerns the insufficiency of Claim 1 arising from ambiguity or uncertainty. The appellant argues that the Judge erred in failing to consider this type of insufficiency, which arises where the PSA does not know whether he is inside or outside the claim.
Foot Note 83
AC at para 150.
On the facts, it argues that the Claim 1 and SG 872 are insufficient because the PSA cannot tell whether the δ value of a particular single crystal CVD diamond was within the SG 872 First Order and hence within the scope of the asserted monopoly.
51 The respondent supports the Judge’s findings that SG 872 is not anticipated, obvious or insufficiently disclosed.
52 Its case is that SG 872 claims a new single crystal CVD diamond material with exceptionally low strain and a new method of producing said diamond material.
Foot Note 84
RSA at paras 1–4.
By way of a letter dated 21 September 2022, which was sent in response to our query (see above at ), the respondent accepts that each product claim in SG 872 covers a class of products. The distinction between a single product and a class of products is relevant to the issue of insufficiency. If the claim is to a single product, then it is sufficient if it enables the making of that one product. If, on the other hand, the claim is to a class of products, that class of products is sufficiently enabled only if the skilled man can work the invention in respect of all members of the class (Regeneron Pharmaceuticals Inc v Kymab Ltd and another  EWHC 87 (Pat) at ). We return to these principles at – and  below.
53 In response to the appellant’s submission that the patent is insufficient because it fails to teach the Claim 62 growth process clearly and completely enough, the respondent argues that the correct test is whether the patent’s specification as a whole discloses the invention sufficiently.
Foot Note 85
Respondent’s Counsel’s Note (“RCN”) at para 51(b).
It argues that the specification of SG 872 (in particular Example 1 read with Example 9) gives full disclosure of the Other Growth Conditions, including temperature, pressure and gas flow rates. It stresses that the burden is on the appellant to show that the invention is unworkable by the PSA who is “trying to give practical meaning to the patent specification.”
Foot Note 86
RCN at para 51(d).
54 Next, as to the appellant’s submission that the Judge erred in failing to consider a further type of insufficiency brought about by ambiguity or uncertainty, the respondent submits that the Judge rejected the appellant’s argument on insufficiency arising from “ambiguity”, on the basis that in First Currency Choice we held that lack of clarity under s 25(5)(b) of the Patents Act (2005 Rev Ed) is not a ground for revocation.
Foot Note 87
RC at para 173.
It further submits that the appellant has not explained how the Judge erred in following First Currency Choice, or why the court should depart from the position at law that lack of clarity is not a basis for revocation.
Foot Note 88
RC at para 174.
On the facts, the respondent submits that the PSA can determine that δ is within the SG 872 First Order by using four different methods.
Foot Note 89
RC at para 175.
Issues to be determined
55 In light of the foregoing, the issues we shall address in this decision are as follows:
(a) Whether the product claims in SG 872 cover a single product or a range of products?
(b) Whether any or all of the claims in SG 872 are invalid due to insufficiency?
(c) Whether SG 872 should be revoked in its entirety?
Patents in general
56 To set the context for the analysis that follows, we first touch on some foundational principles that guide us, beginning with the objectives of the patent regime and how these are advanced. Where relevant, we also explain principles of patent law which are engaged in the reasoning of this judgment, or which provide context to our analysis.
57 The patent regime has two main aims. First, it seeks to encourage innovation by granting the patentee a monopoly over the patented invention for a limited period (meaning the right to exclude others from using that invention). In this regard, each patent demarcates the monopoly which the patentee asserts. Apart from incentivising innovation with the promise of a monopoly right, the patent regime also seeks to disseminate knowledge. This second objective, the dissemination of knowledge, is as important as the first and is achieved by requiring the patentee to teach, in the patent specification, how to work or make the asserted invention. This is so that the public, following the expiry of the limited-term monopoly, may freely use or build on the invention in light of the teachings in the patent (see Ng-Loy Wee Loon, Law of Intellectual Property of Singapore (Sweet & Maxwell, Revised 3rd Ed, 2022) (“Ng-Loy”) at paras 29.1.2–29.1.3 and Colin Birss et al, Terrell on the Law of Patents (Sweet & Maxwell, 19th Ed, 2022) (“Terrell”) at para 1-01).
58 To ensure that patents effectively incentivise innovation in furtherance of the first aim, the patent regime only grants monopolies over deserving inventions. An invention must be novel, contain an inventive step and be capable of industrial application, before it will be patentable (ss 13–16 of the Patents Act (2005 Rev Ed)). If any one of these requirements is not met, the patent may be revoked (s 80(1)(a) of the Patents Act (2005 Rev Ed)). We briefly introduce the concepts of novelty and inventive step as the parties have made submissions on them (although, as foreshadowed at  above, we will not analyse the parties’ submissions on these requirements in this judgment).
59 Novelty requires the invention to be new, in that it does not form part of the state of the art (s 14(1) of the Patents Act (2005 Rev Ed)). If directions forming part of the state of the art (meaning a piece of prior art) lead inevitably to something that would infringe the patent, the invention lacks novelty and the patent can be revoked(Mühlbauer AG v Manufacturing Integration Technology Ltd  2 SLR 724 (“Mühlbauer”) at ). The state of the art comprises all matter (whether a product, a process, information about either, or anything else) which has at any time before the priority date of that invention been made available to the public (whether in Singapore or elsewhere) by written or oral description, by use or in any other way (s 14(2) of the Patents Act (2005 Rev Ed)). By default, the “priority date” of an invention is the filing date of the patent application (s 17(1) of the Patents Act (2005 Rev Ed)). Under certain conditions, a patentee can depart from this default position by claiming that the priority date of the invention takes reference from the date of filing of an earlier patent application or applications (see s 17(2) of the Patents Act (2005 Rev Ed)), which has the effect of limiting the state of the art to what it was at that earlier date. On the other hand, a later priority date may widen the pool of material which may anticipate the invention.
60 An invention shall be taken to involve an inventive step if it is not obvious to a PSA, having regard to any matter which forms part of the state of the art as at the priority date of the invention (s 15 of the Patents Act (2005 Rev Ed)). When considering the issue of obviousness, it is assumed that the invention is novel and differs in some identifiable respect from the prior art. The key question then is whether these differences constitute steps that would have been obvious (Ng-Loy at para 30.2.48; Mühlbauerat  citing Windsurfing International Inc v Tabur Marine (Great Britain) Ltd  RPC 59 (“Windsurfing”)). This is a question of degree.
61 Separately, the second aim of the patent regime, namely knowledge dissemination, is advanced by the “sufficiency” or “enabling disclosure” requirement, which provides that the patent specification must disclose the invention in a clear and complete manner for it to be performed by a PSA. This requirement is statutorily embodied in ss 25(4) and 80(1)(c) of the Patents Act (2005 Rev Ed), with the latter providing for the revocation of the patent if the patent specification is insufficient.
62 Underlying the novelty, obviousness and sufficiency inquiries is the need for the court to first construe the patent claims before undertaking the substantive analyses (Ng-Loy at paras 30.2.34 and 30.2.52; Terrell at para 13-15). Claim construction identifies the invention that is said to be novel, non-obvious and sufficiently disclosed, and in respect of which the monopoly is claimed. It is therefore a pivotal exercise that frames the substantive analyses which follow thereafter.
63 Another point of commonality is that the court, when undertaking the novelty, obviousness and sufficiency inquiries, as well as in construing the claims, dons the mantle of the PSA, that is, someone in the field of technology relevant to the invention in question and who possesses, amongst other characteristics, common general knowledge in the art (Mühlbauerat  (novelty); ASM Technology Singapore Pte Ltd v Towa Corp  1 SLR 211 at  (obviousness); First Currency Choice at – (sufficiency); Lee Tat Cheng v Maka GPS Technologies Pte Ltd  1 SLR 856 (“Lee Tat Cheng (CA)”) at  (claim construction)). Common general knowledge is information which, at the relevant date, is common knowledge in the art to which the alleged invention relates, so as to be known to duly qualified persons engaged in that art (British Thomson-Houston Co Ltd v Stonebridge Electrical Co Ltd (1916) 33 RPC 166 at 171; Terrell at para 8-61).
64 Whilst the PSA and his common general knowledge are important concepts which feature in multiple areas of patent law, they assume relevance in different ways. When determining whether the patented invention is novel or contains an inventive step, the PSA employs his common general knowledge to interpret prior art, amongst other purposes (see Mühlbauer AG at , citing Windsurfing; Synthon BV v SmithKline Beecham plc  UKHL 59 at ; Terrell at paras 8-62, 11-55, 12-10 and 12-19). Interpreting the prior art is crucial to determining what information is conveyed to the PSA at the priority date of the patent in suit or the date on which the piece of prior art (such as a book or journal) was published and whether that information renders the invention obvious and/or anticipates the invention (see Terrell at paras 11-55–11-60 and 12-10). However, this is not the case where claim construction and sufficiency are concerned. In these contexts, the PSA mainly directs his common general knowledge towards interpreting the patent claims and working the invention disclosed therein (see Lee Tat Cheng v Maka GPS Technologies Pte Ltd  3 SLR 1334 (“Lee Tat Cheng (HC)”) at ; Genelabs Diagnostics Pte Ltd v Institut Pasteur and another  3 SLR(R) 530 (“Genelabs (CA)”) at –).
65 Further, the precise assumptions applicable to the PSA are not identical in all areas of patent law. For instance, in matters of claim construction and sufficiency, the PSA is assumed to have the patent specification in his hands whereas when considering the issue of obviousness, the PSA is deemed only to be considering the prior art without the patentee’s invention in front of him (Terrell at para 8-19).
66 The central issues concerned in our decision relate to claim construction and insufficiency. To reiterate, the former identifies the invention that is the subject of the claims, whilst the latter entails a consideration of whether the patent specification sufficiently enables a PSA to perform that invention. It is in this context that we now turn to examine the characteristics of the PSA relevant to our reasoning in the present judgment, and the common general knowledge he (or, the notional team comprising the PSA) would possess.
The person skilled in the art
67 The PSA, apart from possessing common general knowledge in the art, also has a practical interest in the subject matter of the patent and is likely to act on the directions given in it with the desire to make the directions in the patent work. He is a reasonably intelligent but unimaginative workman or technician who has the skill to make routine workshop developments, but not to exercise inventive ingenuity or think laterally (Ng Kok Cheng v Chua Say Tiong  2 SLR(R) 326 (“Ng Kok Cheng”) at ; First Currency Choice at ; Ng-Loy at para 30.1.12).
68 The PSA may be an individual person or a notional team of people. The need for a notional team may arise where it is clear that the patent specification engages more than one set of skills which in the real world would be possessed by more than one person. This may be the case where the art is one that concerns a highly developed technology. In such circumstances, the specification can be said to be addressed to a team, with each member contributing his or her individual skill which would in turn be employed in combination in interpreting and carrying into effect the instructions in the patent (Terrellat paras 8-35–8-36; The General Tire & Rubber Company v The Firestone Tyre and Rubber Company Limited and others  RPC 457 (“General Tire”) at 483; Schlumberger Holdings Ltd v Electromagnetic Geoservices AS  EWCA Civ 819 at ; Halliburton Energy Services, Inc v Smith International (North Sea) Ltd  RPC 2 at 46; see also Institut Pasteur and another v Genelabs Diagnostics Pte Ltd and another  SGHC 53 (“Genelabs (HC)”) at ). For the avoidance of doubt, the formation of such a notional team does not mean that the common general knowledge of the PSA is only that which is common to persons with these different backgrounds(Inhale Therapeutic Systems Inc v Quadrant Healthcare Plc  All ER (D) 211 (Jun) at –; First Currency Choice at ).
69 As noted at  above, when considering the issues of claim construction and sufficiency, the PSA is assumed to have the patent specification in his hands and have the same attributes for both inquiries (see Terrell at para 8-19). The PSA, for the purposes of the insufficiency inquiry, is “trying to carry out the invention and achieve success” (Zipher Ltd v Markem Systems Ltd and another  EWHC 1379 (Pat) (“Zipher”) at ). It is through the eyes of the PSA that the patent will fall to be interpreted, and the PSA must know how to perform the invention upon reading the specification in light of his common general knowledge.
70 Moving now to the PSA in the present case, the Judge found that the PSA, for the purpose of claim construction, would be a notional team of persons working in the field of growing CVD diamonds, with expertise in diamonds (including natural, HPHT and CVD diamonds) and the sciences (including applied physics, optical engineering and material sciences) (Judgment at ):
In the present case the defendant’s PSA is a composite person having a Master’s degree in mechanical or chemical engineering and having a doctorate in applied physics, electrical engineering, optical engineering or a closely related field, aided by an engineer/technician with skills in mechanical polishing, laser cutting and correlated measurements. The plaintiff disputes this, and contends that the PSA is a team of people collectively having a Bachelor of Science in physics, chemistry or material sciences, and knowledge of diamond properties in all its forms at the material time (natural, high-pressure high-temperature (‘HPHT’) and CVD diamonds) as well as working knowledge of CVD diamond synthesis and commercial production. This disagreement has no practical significance, as no finding in the case turns upon this fine distinction. The present case would require consideration of a team of persons working in the field of growing CVD diamonds. In my judgment, the relevant PSA in such a field would include a team of individuals with expertise in diamonds and science generally, with access to individuals possessing doctorate qualifications.
71 The parties have not challenged the Judge’s finding in that passage of the composition and qualifications of the notional team of persons. Further, as already mentioned at  above, the PSA for the purposes of claim construction and sufficiency will be the same. However, before us, the appellant seeks to impute the PSA with the specific purpose of growing single crystal CVD diamond material for use in the most demanding optical applications – “etalons and anvils”.
Foot Note 90
Appellant’s Skeletal Arguments (“ASA”) at para 21; AR at para 12; Transcript, 20 January 2022, p 15:24–26.
The respondent rejects this imputation.
Foot Note 91
RC at paras 44, 68, 148 and 165.
Although this dispute between the parties mainly arises in the course of their submissions on novelty and obviousness, a proper identification of the PSA’s practical interest is also important in the context of claim construction and sufficiency.
72 As earlier stated, the PSA is trying to carry out the invention (see  above) and has a practical interest in the “subject matter of the patent” (see  above). What the subject matter of the patent is should be determined by reference to the patent specification. Having regard to the specification of SG 872, we are satisfied that the PSA’s interest would not be limited to producing etalons and anvils. The patent specification describes the invention in SG 872 in more general terms – a single crystal CVD diamond material which possesses certain desirable characteristics, and which can be used in connection with a wide range of optical applications which “include but are not limited to” optical windows, laser windows, optical reflectors, optical refractors and lenses, diffractive optical elements, etalons, ornamental use and anvils [emphasis added].
Foot Note 92
BOM at p 322.
Accordingly, the PSA’s practical interest lies in using the growth process taught in SG 872 to grow low-strain diamonds for a range of optical applications.
The common general knowledge
73 As already noted, the PSA is imputed with common general knowledge in the art. He draws upon such knowledge to understand a patent and in his attempts to carry it into effect. As mentioned at  above, common general knowledge is information which, at the relevant date, is common knowledge in the art to which the alleged invention relates, so as to be known to duly qualified persons engaged in that art. The relevant art to which the alleged invention is to be gathered from the patent specification itself (First Currency Choice at ).
74 Common general knowledge is ordinarily established, where not agreed, by expert evidence which is usually supported by reference to textbooks or other reference works which the PSA would be expected to have access to and acquire his information from. The publication at or before the relevant date of such documents may be prima facie evidence tending to show that the statements contained in them were part of the common general knowledge, but that is far from complete proof as those statements may well have been discredited, forgotten or ignored (Terrell at paras 8-75–8-77). It is also not sufficient just to point out that it was said in a scientific paper that has been well circulated. A particular disclosure does not become common general knowledge merely because it is widely read, and still less because it is widely circulated. To prove that a particular disclosure in scientific paper has become common general knowledge, it must be shown that it is generally known and generally regarded as a good basis for further action by the bulk of those who are engaged in the particular art to which the disclosure relates (General Tire at 480–481).
75 In the present case, as identified by the Judge, the art relates to the growth of CVD diamonds (Judgment at ). In our view, this includes methods of measuring the physical properties of the CVD diamonds grown. Based on the Primer,
Foot Note 93
See Primer at p 1 et seq.
the parties are agreed that the information set out at –, – and  above constituted common general knowledge in the art of growing CVD diamonds at the relevant time. There are further points of agreement on what was part of the common general knowledge and they will be mentioned, where relevant, when we apply the principles of sufficiency to the facts of this case. But before going into the issue of sufficiency, it is pertinent for us to first consider how the claims, in particular the product claims, ought to be construed. It is to this issue that we now turn.
Patent construction: do the product claims in SG 872 cover a single product or a class of products?
76 The question here is whether the product claims in SG 872 cover a single product or a class of products. As we shall see, this affects what, in law, must be enabled by the specification of SG 872 (see – below), and whether the claims in SG 872 are in fact insufficient (see, eg, – below).
77 Whether the patent claims a single product or a range of products is a question of construction of the claim(s) in the patent (Regeneron Pharmaceuticals Inc v Kymab Ltd  1 All ER 475 (“Regeneron (SC)”) at . Before setting out the principles on claim construction in detail, we touch on the relevance of the priority date(s) of the product claims in SG 872 to their interpretation.
78 In Lee Tat Cheng (CA) at  and , we held that the relevant date for claim construction is the date of the patent application (meaning its filing date) (see also Lee Tat Cheng (HC) at ). However, it does not appear that the patentee there claimed that its invention took priority from an earlier filing. If the patentee therehad claimed priority, a conundrum noted by the authors of Terrell would have arisen. That conundrum arises from the fact that the English cases are divided over whether the relevant date for patent construction is the priority date or filing date of the patent application, or the publication date of the patent (see Terrell at paras 9-08–9-014). At present, the respondent does claim priority from GB Patent Application No 0227261.5 (“GB 261”), which was filed on 21 November 2002. The parties agree that Claim 1ii) takes priority from 21 November 2002 but disagree on whether Claims 1iii) and 62 enjoy the same priority.
Foot Note 94
AC at paras 26 (Claim 1iii)) and 31 (Claim 62).
This specific complication did not present in Lee Tat Cheng (CA). However, nothing in this case turns on which of the three dates should be adopted in law and the parties do not submit otherwise. We therefore prefer to leave this issue for an appropriate case and proceed on the basis that the relevant date for patent construction is the filing date of SG 872 (that is, 20 November 2003). Consequently, any common general knowledge which may be relevant to patent construction must be shown to exist by this date. In addition, whether the asserted priority date is granted only assumes significance in this case in relation to the issues of novelty and obviousness. However, as stated at , we need not reach or address the latter issues in this judgment.
79 Turning to the substantive principles on claim construction, in Lee Tat Cheng (CA), we reaffirmed the correctness of construing a patent’s claims purposively (at  and ). This entails, among other things, viewing the claims through the lens of the PSA (at ):
(a) In ascertaining the true construction of a patent specification, the claims themselves are the principal determinant. What is not claimed is deemed to be disclaimed.
(b) The description and other parts of the patent specification form the context for, and may assist in, the construction of the claims.
(c) The claims are to be construed purposively, and not literally. This would give the patentee the full extent, but no more than the full extent, of the monopoly which a person skilled in the art, reading the claims in context, would think the patentee was intending to claim. In this regard, the starting point is to ask the threshold question: What would the notional skilled person have understood the patentee to mean by the use of the language of the claims? The Improver questions (see  above), which were derived from Catnic ( supra), have also been used as guidance in construing patent claims.
(d) As a general rule, the notional skilled person should be taken to be a workman or technician who is aware of everything encompassed in the state of the art and who has the skill to make routine workshop developments, but not to exercise inventive ingenuity or think laterally.
(e) Purposive construction does not entitle the court to disregard clear and unambiguous words in a patent claim, and the court is not entitled to rewrite or amend the claim under the guise of construction. In construing a claim purposively, the language that the patentee has adopted is more often than not of utmost importance. It is not permissible to put a gloss on or expand a claim by relying on a statement in the patent specification.
(f) If an allegedly infringing article falls within the words of one of the claims of a patent properly construed, the patent would have been infringed. To constitute infringement, the article concerned must usurp each and every one of the essential elements of the claim in question.
80 The patent “specification”, referred to in the passage above, comprises the description of the invention, drawings (if any) and the claims (Halsbury’s Laws of Singapore vol 13(3) (LexisNexis, 2020 reissue)(“Halsbury’s Singapore IP”) at para 160.321). Examples illustrating how to carry out the invention also form part of the patent’s specification (see rr 19(3) and 19(5)(e) of the Patents Rules (1996 Rev Ed)). However, the claims serve a different purpose from the rest of the patent’s specification, as explained by Floyd LJ in Adaptive Spectrum & Signal Alignment Inc v British Telecommunications PLC  EWCA Civ 1462 at :
... The specification describes and illustrates the invention, the claims set out the limits of the monopoly which the patentee claims. As with the interpretation of any document, it is conceivable that a certain, limited, meaning may be implicit in the language of a claim, if that is the meaning that it would convey to a skilled person, even if that meaning is not spelled out expressly in the language. However it is not appropriate to read limitations into the claim solely on the ground that examples in the body of the specification have this or that feature. The reason is that the patentee may have deliberately chosen to claim more broadly than the specific examples, as he is fully entitled to do.
[emphasis in original]
81 The parties initially appear to have approached this appeal on the basis that each product claim is a claim to a single product – a new CVD diamond material. For instance, the Appellant’s Case states that “Claim 1 is a product claim, so the eight alternates in Claim 1 disclose the same physical thing – a particular CVD diamond material, characterised in eight different ways”.
Foot Note 95
AC at para 19.
The Respondent’s Case states that “SG 872 claims a new diamond material” [emphasis in original omitted; emphasis added in italics].
Foot Note 96
RC at para 11.
Both parties took similar positions in their written closing submissions in the second tranche of the trial.
Foot Note 97
PCS2 at para 871 (III(G3) ROA 122–123); DCS2 at para 56 (III(G6) ROA 36).
82 We wrote to the parties on 14 September 2022 seeking clarification on this issue. The appellant confirmed its view that SG 872 teaches the PSA a new method to “grow one product, i.e. a CVD single crystal diamond material having one or more of the specified parameters.” It argued that the “different ranges and combination of properties in each product claims [were] therefore variations of the same product grown from the one process described in SG 872” [emphasis added].
Foot Note 98
Respondent’s letter dated 21 September 2022 at para 5.
In contrast, the respondent took the view that each product claim could be said to cover a class of products. In particular, the respondent noted that “given that the product claims of SG 872 claim, inter alia, a range of values (or depend on a claim which does), these would cover a class of products meeting the values within that range as opposed to an individual product.”
Foot Note 99
Appellant’s letter dated 21 September 2022 at para 2(b).
83 We agree with the respondent. Properly construed, each claim asserts a monopoly over a class of single crystal CVD diamond materials.
84 We turn first to Claim 1, which, as noted above, is the claim that all the other product claims refer back to. In our judgment, Claim 1 can be infringed by various types of single crystal CVD diamond materials, each with a different combination of the physical properties defined in the limbs of Claim 1. That the diamond materials falling within Claim 1 may possess different combinations of physical properties is clear from the words in the chapeau of Claim 1: “A CVD single crystal diamond material which shows at least one of the following characteristics” [emphasis added]. Our reading of the plain language of Claim 1 is fortified by the description of the invention in the specification of SG 872. The relevant portion of the description reads as follows:
Foot Note 100
BOM at p 309.
The diamond material of the invention can be tailored to specific applications, and although it may not be endowed with all of the above properties in all cases, in many applications it is the ability of the diamond material to show a substantial set or particular combination of the above properties which makes its use particularly beneficial. For example, for use as an etalon, the material may require optical homogeneity, low absorption, high thermal conductivity and the ability to be processed flat and parallel, but laser damage thresholds and mechanical strength may be less important.
[emphasis added in bold italics]
The “above properties” referred to in the passage include optical homogeneity, effective refractive index, birefringence, optical absorption, optical scatter, laser damage threshold, thermal conductivity, parallelism, flatness and mechanical design strength.
Foot Note 101
BOM at pp 301–308.
Thus, the description indicates that the invention covers a range of single crystal CVD diamonds possessing different combinations of physical properties.
85 Further, as noted in Lee Tat Cheng (CA) at [41(c)], the language of the claim must be construed through the eyes of a PSA. In this regard, we found the evidence of Dr Mark Edward Newton (“Dr Newton”), the respondent’s expert witness, to be instructive. As the respondent alluded to in its letter of 21 September 2022,
Foot Note 102
Respondent’s letter dated 21 September 2022 at para 2(a).
Dr Newton testified that the various limbs in Claim 1 cover optical properties which “may be related but remain different” [emphasis added in bold italics].
Foot Note 103
Newton-2 at paras 79, 83 (I RSCB 173).
He added that “[m]any are not directly derivable one from another”.
Foot Note 104
Newton-2 at para 76 (1 RSCB 171).
It is not clear if these observations also apply to Claims 1ii) and 1iii), which both relate to birefringence. Dr Newton’s evidence nevertheless reinforces our understanding that diamonds which fulfil different combinations of limbs in Claim 1 are in fact different diamonds. Our conclusion would be different if the measurements in each limb of Claim 1 were different ways of quantifying the same property.
86 Although Dr Nebel’s first report dated 13 May 2019 (“Dr Nebel’s 1st Report”) stated that a diamond satisfying one limb of Claim 1 will also satisfy all remaining limbs, and that the properties mentioned in Claim 1 are “merely ... different measurement techniques for a common aspect of the diamond” [emphasis added in bold italics], we reject this.
Foot Note 105
Dr Nebel’s 1st Report (“Nebel-1”) at para 69 (III(B13) ROA 90).
For one, he offered no credible evidence in his Reply Report dated 26 June 2019 or oral testimony to support this assertion. In his reply report, Dr Nebel asserted that measurements like “dislocation density, Raman peak width, X-ray rocking curve width and birefringence” measure “strain in diamond ... and any change in strain in a diamond reflects a proportional change in these measurement parameters.”
Foot Note 106
III(B62) ROA 93 (para 223); see also III(D5) ROA 119:3–6.
But Dr Nebel did not explain nor has the appellant otherwise shown that the optical properties or measurements described in each limb of Claim 1, including optical homogeneity, free spectral range, contrast ratio, insertion loss and variation in refractive index, merely measure a common property or will necessarily be present if one limb of Claim 1 is fulfilled. Crucially, Dr Nebel’s evidence does not square with the specification of SG 872. The “Summary of the Invention” states clearly that the CVD single crystal diamond material invented “may not be endowed with all of the above properties in all cases”, but should show “at least one, preferably at least two, more preferably at least three, and even more preferably at least four” characteristics which are listed. The listed characteristics in the Summary of the Invention correspond to properties defined under the limbs in Claim 1, and include optical homogeneity (see Claim 1i)), birefringence (see Claims 1ii) and 1iii)), effective refractive index (see Claim 1iv)), free spectral range (“FSR”) (see Claim 1v)) and contrast ratio (see Claim 1vi)).
Foot Note 107
See BOM at pp 301–308, 363–365.
Moreover, in its submissions below, the appellant did not appear to dispute the correctness of the portion of Dr Newton’s evidence that we have accepted at  above.
Foot Note 108
See Defendant’s skeletal oral reply at para 26 (III(G6) ROA 227), read with PCS2 at para 288 (III(G2) ROA 129–131).
87 Turning now to the subsequent product claims, these likewise cover a range of diamonds. These claims may be placed into three categories based on their phraseology, all of which incorporate Claim 1. The first category of claims incorporates all preceding claims, including Claim 1. An example is Claim 6, which states: “A CVD single crystal diamond material according to any one of the preceding claims, which has a value of effective refractive index of 2.3964 to within an accuracy of +/-0.001” [emphasis added].
Foot Note 109
BOM at p 309.
The second category of claims expressly incorporates a preceding claim, the latter of which incorporates Claim 1. An example is Claim 7, which states: “A CVD single crystal diamond material according to claim 6, which has a value of effective refractive index of 2.39695 to within an accuracy of +/-0.0005.” By referring back to Claim 6, Claim 7 likewise incorporates Claim 1. The third category consists only of Claim 72. It reads: “A CVD single crystal diamond material produced by a method according to any one of claims 62 to 71.” Claims 62 to 71 disclose a process that purportedly enables a PSA to produce a CVD diamond in one or more of Claims 1 to 61. By referencing all of these process claims, Claim 72 includes the range of diamonds defined under Claim 1.
88 Once a subsequent product claim incorporates Claim 1, it asserts a monopoly over a range of products. This is because any diamond within the class of products in Claim 1, which also fulfils the additional parameter expressed in the subsequent claim, will fall within that subsequent claim. It is irrelevant that the additional parameter in the subsequent claim is a specific or single value of a particular physical property (for instance, Claim 6, in so far as the additional parameter, “effective refractive index of 2.3964 within an accuracy of +/-0.001”, expresses a single value of an effective refractive index) or a binary condition that is or is not satisfied (for instance, Claim 50, which has an additional requirement that the CVD diamond be formed into a polished gemstone). For reference, these claims state as follows:
6. A CVD single crystal diamond material according to any one of the preceding claims, which has a value of effective refractive index of 2.3964 to within an accuracy of +/-0.001.
50. A CVD single crystal diamond material according to claim 49, which is formed into a polished gemstone.
In these instances, the PSA would be satisfied that the patentee contemplated multiple diamonds in the Claim 1 range fulfilling the additional parameter in Claims 6 and 50. This is because the claim incorporates the entire range of diamonds in Claim 1 and there is nothing in the language of Claims 6 and 50, or for that matter in any other similar claim, to justify limiting the monopoly to a single product. We approach this on the basis that the respondent should be afforded the full extent of the monopoly that is supported by the language it has adopted.
89 It is even more the case that where the additional parameter in the subsequent claim is itself expressed as a range of values, the claim covers a range of products. One example of this is Claim 4, which states: “A CVD single crystal diamond material according to any one of the preceding claims, wherein the modulus of the sine of the phase shift, |sin δ|, for at least 98% of the analysed area remains in first order and does not exceed 0.4” [emphasis added in bold italics]. The phrase “does not exceed 0.4” indicates that Claim 4 monopolises a class of CVD single crystal diamond materials which have different |sin δ| values falling within the range of less than or equal to 0.4 (and which fulfil any preceding claim). By way of example, a CVD single crystal diamond material for which |sin δ| is equal to 0.2 as well as a CVD single crystal diamond material for which |sin δ| is equal to 0.3 could fall within the scope of Claim 4, subject to the diamond material also satisfying a preceding claim.
90 We find support for our construction of the product claims in the court’s analysis in Anan Kasei Co. Ltd and another company v Neo Chemicals and Oxides Ltd (formerly Molycorp Chemicals and Oxides (Europe) Ltd) and another company  EWCA Civ 1646 (“Anan”). The patent contained a product claim for ceric oxide, which stated as follows: “A ceric oxide consisting essentially of a ceric oxide, and wherein said ceric oxide has a specific surface area of not smaller than 30.0 m2/g when subjected to calcination at 900˚C for 5 hours.” (at ). One issue which arose was whether a claim limited by reference to a desirable physical characteristic, namely high specific surface area, and specifying that it remained the same after being subjected to a high temperature, insufficiently described the invention and was invalid. In analysing this issue, Floyd LJ (with whom Lewison and Peter Jackson LJJ agreed) noted that the claim covered a class of products (at ):
The claim in the present case is to a class of products identified by their composition (consisting essentially of ceric oxide), their physical characteristics (their [specific surface area or] SSA), and their performance in the calcining test. That it is a class of products is plain from the fact that the claim can be satisfied by a range of degrees of purity, and SSA, and from the fact that performance in the calcining test may vary from pass to distinction.
91 Regeneron (SC) is also illuminating. The patent in the suit contained a product claim which read as follows:
A transgenic mouse that produces hybrid antibodies containing human variable regions and mouse constant regions, wherein said mouse comprises an in situ replacement of mouse VDJ regions with human VDJ regions at a murine chromosomal immunoglobulin heavy chain locus and an in situ replacement of mouse VJ regions with human VJ regions at a murine chromosomal immunoglobulin light chain locus.
Lord Briggs summarised the claim in these terms (at ):
This is of course a product claim, seeking a monopoly for the 'making' (at first sight a strange but serviceable word to use of an animal) of a genetically engineered mouse having the characteristics described in the claim. The characteristics related both to what such a mouse does (namely produce the hybrid antibodies described) and to what is contained in its genome, namely the Reverse Chimeric Locus, achieved by a process of 'in situ replacement' of the murine variable regions in both the light and heavy chain gene loci with the corresponding but of course different human variable regions. The claim seeks protection for the making and exploitation of any type of mouse having those characteristics. Since the description of what the mouse does is more loosely worded than the description of what lies within its genome, it is the latter description which mainly controls the breadth of the claim.
[emphasis added in italics and bold italics]
92 Relevantly, the appeal in Regeneron (SC) proceeded on the basis that the claim covered a range of transgenic mice, which differed based on the amount of human antibody genes implanted into the genome of the mouse (see , – and ). However, it bears highlighting that this issue of claim construction was resolved by the courts below and was not an issue in the appeal before the UK Supreme Court (“UKSC”).
93 In the present case, by defining parameters using ranges of values or incorporating claims which do so, each product claim in substance claims or asserts a monopoly over a range of single crystal CVD diamonds, each with a different combination of physical properties.
94 Before leaving this issue, we note that while Dr Newton’s evidence assisted us in construing the product claims, the expert evidence is not entirely clear as to whether each product claim covers a class of products or not. Be that as it may, claim construction is ultimately a task for the court. In particular, while expert evidence is useful in explaining the technical terms and technical features of the invention, the nature of the invention for which a patent is granted must be ascertained by the judge and not an expert (Brooks v Steele and Currie (1896) 13 RPC 46 at 73 and Dyson Appliances Ltd v Hoover Ltd  RPC 22 at , cited in Terrell at paras 9-182 and 9-184). For the reasons given above, we hold that each of the product claims in SG 872 covers a range of products.
The law of insufficiency
95 The sufficiency or enabling disclosure requirement finds statutory expression in ss 25(4) and 80(1)(c) of the Patents Act (2005 Rev Ed). Section 25(4) of the Patents Act (2005 Rev Ed), in the context of prescribing the requirements of a patent application, states that:
The specification of an application shall disclose the invention in a manner which is clear and complete for the invention to be performed by a person skilled in the art.
96 Non-compliance with s 25(4) of the Patents Act (2005 Rev Ed) is a ground for revoking the patent, as provided for in s 80(1)(c) of the Patents Act (2005 Rev Ed):
Subject to the provisions of this Act, the Registrar may, on the application of any person, by order revoke a patent for an invention on (but only on) any of the following grounds:
(c) the specification of the patent does not disclose the invention clearly and completely for it to be performed by a person skilled in the art;
97 It is this requirement that compels the inventor to tell the world how his invention works so that, after the expiry of the patent when his invention falls into the public domain, a PSA will have sufficient information to work the invention and build on it (see Ng-Loyat paras 29.1.3 and 30.3.1).
98 English case law may be instructive when interpreting the scope of the sufficiency requirement under our Patents Act (2005 Rev Ed). Section 25(4) of the Patents Act (2005 Rev Ed) is in materially similar terms as s 14(3) of the UK Patents Act 1977 (c 37) (“UK Patents Act 1977”), which reads:
The specification of an application shall disclose the invention in a manner which is clear enough and complete enough for the invention to be performed by a person skilled in the art.
[emphasis added in italics]
99 Section 80(1)(c) of the Patents Act (2005 Rev Ed) is also materially similar to s 72(1)(c) of the UK Patents Act 1977, which states:
Subject to the following provisions of this Act, the court or the comptroller may by order revoke a patent for an invention on (but only on) any of the following grounds, that is to say—
(c) the specification of the patent does not disclose the invention clearly enough and completely enough for it to be performed by a person skilled in the art;
[emphasis added in italics and bold italics]
100 Although the word “enough” is omitted in ss 25(4) and 80(1)(c) of the Patents Act (2005 Rev Ed) (and, for that matter, the same provisions in the Patents Act 1994 (2020 Rev Ed)), the sufficiency requirement in Singapore is not stricter. Our courts have held that a patent specification suffices if it is “clear enough” and “complete enough”; absolute clarity and completeness are not uncompromisingly required. This is because under ss 25(4) and 80(1)(c) of the Patents Act (2005 Rev Ed), as long as the specification is sufficiently clear “for [the invention] to be performed by a person skilled in the art”, it does not matter that the specification does not state every single step required for performance. After all, the PSA does not have to be told what is self-evident or what is part of his common general knowledge (First Currency Choice at ; Ng Kok Cheng at  and ). In this regard, the local position is in line with the ss 14(3) and 72(1)(c) of the UK Patents Act 1977.
101 That said, not every aspect of English law on insufficiency is applicable in our context. The UK Patents Act 1977 was passed to give effect to the Convention on the Grant of European Patents, 5 October 1973, 1065 UNTS 199 (“European Patent Convention”). Section 130(7) of the UK Patents Act 1977 provides that certain provisions, including ss 14(3) and 72(1)(c) of the UK Patents Act 1977, were “so framed as to have, as nearly as practicable, the same effects in the United Kingdom as the corresponding provisions of the European Patent Convention”. The English courts have thus approached the law in these respects with the objective of striving for consistency between European and English patent law (Regeneron (SC) at ; Generics (UK) Ltd and others v H Lundbeck A/S  2 All ER 955 (“Generics v Lundbeck (HL)”) at  per Lord Neuberger; Merrell Dow Pharmaceuticals Inc and another v H N Norton & Co Ltd and another; Merrell Dow Pharmaceuticals Inc and another v Penn Pharmaceuticals Ltd and another (1997) 33 BMLR 201 at 205). In interpreting and developing the jurisprudence under ss 14(3) and 72(1)(c) of the UK Patents Act 1977, the English courts have therefore introduced certain concepts into English law from European patent law to give effect to this harmonising objective. Such concepts, however, are not necessarily applicable to ss 80(1)(c) and 25(4) of the Patents Act (2005 Rev Ed), and their applicability falls to be determined with reference to the text and legislative objective of ss 80(1)(c) and 25(4) as well as the Patents Act (2005 Rev Ed) as a whole.
102 We begin by noting the policy that undergirds the sufficiency requirement. Both English and local case law have recognised that the sufficiency requirement lies at the heart of what is sometimes called the “patent bargain”. As already alluded to above at , the inventor/patentee is rewarded with a limited-term monopoly over the claimed invention, in exchange for enabling a PSA to work the claimed invention and dedicating it to public use after the monopoly has expired (Rohm and Haas Electronic Materials CMP Holdings, Inc (formerly known as Rodel Holdings, Inc) v NexPlanar Corp and another  5 SLR 180 (“Rohm”)at ; Warner-Lambert Company LLC v Generics (UK) Ltd t/a Mylan and another  3 All ER 95 at ). The patent bargain breaks down if the patent does not sufficiently teach a PSA how to perform the invention, in which case it makes little sense to reward the inventor/patentee with a monopoly. It is for this reason that the failure to satisfy the sufficiency requirement is a ground for patent revocation.
103 We now turn to set out general principles applicable to the legal requirement of sufficiency in Singapore. References to English jurisprudence will be made where appropriate.
104 It is well-settled under Singapore law that the burden of proving insufficiency rests on the party challenging the validity of a registered patent (Ng Kok Cheng at ).
105 The assessment of whether the legal requirement of sufficiency is met proceeds in two steps. The first step involves identifying the invention and deciding what it claims to enable the PSA to do. The second steps asks whether the specification enables him to do it (Kirin-Amgen Inc and others v Hoechst Marion Roussel Ltd and others; Hoechst Marion Roussel Ltd and others v Kirin-Amgen and others  RPC 169 (“Kirin-Amgen”) at  per Lord Hoffmann, cited with approval in First Currency Choice at ). Indeed, the court can only ascertain whether the disclosure has been sufficient after ascertaining what needs to be disclosed (meaning the invention).
106 Both steps of the inquiry require the court to don the mantle of a PSA possessing common general knowledge of the art. The first step involves the construction of the patent claims from the perspective of the PSA. Claim construction principles as set above at – are applied (see Towa Corp v ASM Technology Singapore Pte Ltd and another  3 SLR 771at  and Main-Line Corporate Holdings Ltd v United Overseas Bank Ltd and another (First Currency Choice Pte Ltd, third party)  1 SLR(R) 1021 at ). At the second step, the PSA uses his common general knowledge to supplement the information contained in the specification in order to perform the invention (see Genelabs (CA) at –). The sufficiency inquiry at the second stage is undertaken with reference to the date of filing of the patent application (Biogen Inc v Medeva PLC  RPC 1 (“Biogen”) at 54 per Lord Hoffmann, followed in Kirin-Amgen Inc v Transkaryotic Therapies Inc  RPC 3 at 70). This is sensible, since s 25(4) of the Patents Act (2005 Rev Ed) imposes the requirement of sufficiency at the time the patent application is made (see also Genelabs (HC) at ; Susanna Leong at para 16.266). As an aside, since we are regarding the relevant date for construing the patent claims (see at  above) and assessing insufficiency as the date of filing of SG 872, and we do not intend to discuss the issues of novelty and obviousness, we need not rule on the respondent’s claim for priority from GB 261.
107 Where the invention is a process, enablement at the second step requires that process to be carried out by the PSA; where the invention is a product, enablement requires the PSA to be able to make that product (Generics v Lundbeck (HL) at ; Roughton, Johnson & Cook, The Modern Law of Patents (LexisNexis, 5th Ed, 2022) (“The Modern Law of Patents”) at para 4.37).
108 Regardless of the nature of the invention, the patent specification must enable the invention to be performed by the PSA over the full breadth of the monopoly claimed, as we explain further below. Lord Hoffmann, who delivered the leading decision in the House of Lords in Biogen, observed that this is a long-established principle in English law (at 48) (see also Idenix Pharmaceuticals, Inc v Gilead Sciences, Inc and others  EWHC 3916 (Pat) (“Idenix (HC)”) at ; Regeneron (SC) at  and ). Later in Kirin-Amgen at , Lord Hoffmann expressly applied this principle to s 72(1)(c) of the UK Patents Act 1977, which embodies the concept of sufficiency in the context of patent revocation:
… The law on this point is contained in s. 72(1)(c) of the [UK Patents Act 1977]. A patent may be revoked if the specification does not disclose the invention 'clearly enough and completely enough for it to be performed by a person skilled in the art’. That means that the disclosure must enable the invention to be performed to the full extent of the monopoly claimed: see Biogen Inc v Medeva plc  RPC 1, 48.
This court in First Currency Choice at  cited Kirin-Amgen at  with approval when setting out the applicable principles in relation to s 80(1)(c) of the Patents Act (2005 Rev Ed).
109 To illustrate what it means for a specification to enable the invention to be performed to the full extent of the monopoly claimed, Lord Hoffmann gave the following illustrations in Biogen at 48:
… If the invention discloses a principle capable of general application, the claims may be in correspondingly general terms. The patentee need not show that he has proved its application in every individual instance. On the other hand, if the claims include a number of discrete methods or products, the patentee must enable the invention to be performed in respect of each of them.
[emphasis added in italics]
Subsequently, in H Lundbeck A/S v Generics (UK) Ltd and others  RPC 437 at , Lord Hoffmann re-iterated that where a claim is to a class of products, the class of products is enabled only if the PSA can work the invention in respect of all members of the class. The specification can show that this is empirically demonstrated or disclose a principle which can reasonably be expected to apply across the class.
110 However, the patent need not set out every detail necessary for the performance of the invention across its entire scope. As mentioned at  above, the patentee can leave the PSA to employ his skill and common general knowledge to work out what needs to be done. But the PSA must not be expected or required to exercise inventive ingenuity or exert undue effort in order to perform the invention across its entire breadth.
111 The requirement of enablement across the full breadth of the claim can be understood with reference to the patent bargain. The inventor/patentee should only be entitled to the full extent of the monopoly claimed if he has fulfilled his end of the bargain by disclosing the full scope of the invention clearly and completely enough. Only if this is done can the second aim of the patent regime, knowledge dissemination, be achieved by way of allowing the public to benefit from the invention after it falls into the public domain. A patent system which allows the inventor/patentee to monopolise more than that which he has sufficiently enabled may unduly stifle research, contrary to its primary aim of encouraging innovation (see Regeneron (SC) at ; Lionel Bently et al, Intellectual Property Law (Oxford University Press, 6th Ed, 2022) at pp 607–608). Hence, even where a patent specification is clear and complete enough to teach a PSA how to perform part of the claimed invention, that does not justify a monopoly over the entire breadth of the invention and the patent may be revoked pursuant to s 80(1)(c) of the Patents Act (2005 Rev Ed).
112 Before leaving this point, we note in passing that the majority of the UKSC in Regeneron (SC) held that it is enough if the patent enables the PSA to make “substantially all the types or embodiments of products within the scope of the claim” (at [56(iv)]) [emphasis added]. This threshold appears to be satisfied where there remain a “tiny or inconsequential number of embodiments which are not enabled” such that the scope of non-enablement is de minimis (at  and [56(v)]). The standard of substantiality was endorsed by the majority because it was the position in EU law (at – and ), and s 130(7) of the UK Patents Act 1977 requires interpretative consistency between European and UK patent law. We are not bound by a similar obligation. Without the benefit of submissions, we shall defer consideration of this aspect of Regeneron (SC) to an appropriate case. In any event, as we shall see, the threshold of substantiality does not have a material bearing on this case.
113 Next, although insufficiency is a single ground of objection to the validity of a patent contained in s 80(1)(c) of the Patents Act (2005 Rev Ed), there are distinct ways in which a patent may be insufficient (see Zipherat ; Anan at ). As will become clear, the appellant’s case engages different aspects of the rule on patent sufficiency, two of which are determinative of this appeal. We now turn to consider the different ways a patent may be insufficient under English and/or Singapore law.
114 The first way in which a patent may be insufficient is where the patent specification is not clear and complete enough to enable the PSA to perform the invention across the whole breadth of the claim(s) without an undue burden (see Terrell at para 13-31). This objection, termed “classical insufficiency”, is well-established in English and local jurisprudence (see First Currency Choice at –). In evaluating the merits of this allegation, the court has to assess the steps which would be necessary for the PSA to take under the patent’s specification to carry out the invention (see Zipherat ).
115 Under English law, a patent specification which enables a PSA to perform the full breadth of the claim without undue effort (meaning that it is not classically insufficient), may nonetheless suffer from another type of insufficiency, known as “Biogen insufficiency”. This form of insufficiency arises where the scope of the claim exceeds the technical contribution to the art made by the invention (see Terrell at para 13-09), whereas classical insufficiency is concerned with the mismatch between the scope of the claim and the method of performance taught in the patent specification. The “technical contribution to the art” does not refer to the technicalities of performing the claimed invention, but, more generally, to how the invention has in a practical sense added to or advanced the state of the art (that said, we note that the precise concept of “technical contribution to the art” has been articulated in various ways (see Generics v Lundbeck (HL) at  per Lord Neuberger, at  per Lord Mance and at  per Lord Walker)).
116 Consider, for example, a claim to “a heavier than air flying machine” in a patent which only discloses how to make an airplane. Assume for the moment that an airplane is a new and non-obvious invention, and the patent specification is clear and complete enough for a PSA to make an airplane. The airplane is a machine that is (a) capable of flight and (b) heavier than air, and by teaching the PSA how to make an airplane, the patent specification has enabled performance of every integer (or “element”, see Rohm at  and ) of the claim. In other words, the patent specification has sufficiently enabled the full breadth of the claim and can avoid a classical insufficiency attack. Yet, because the language of the claim has defined the invention in such general terms, the monopoly asserted by the claim is capable of extending to all other forms of heavier than air flying machines that are not airplanes and which may be manufactured by a wholly different process. The breadth of the claim thus exceeds what the patentee has contributed to the state of the art, in this example, how to make an airplane. This gives rise to Biogen insufficiency (see Anan at , citing Biogen at 52).
117 At present, Singapore patent law has not recognised the concept of Biogen insufficiency under s 80(1)(c) of the Patents Act (2005 Rev Ed), and it is unclear whether it should. We observe that Biogen insufficiency was first recognised by Lord Hoffmann in Biogen at 54, in the light of the jurisprudence under the European Patent Convention:
In my view, however, there is an important difference between the 1949 and 1977 Acts which make decisions on the earlier Acts an unsafe guide. Section 72(1)(c) of the [UK Patents Act 1977] is not only intended to ensure that the public can work the invention after expiration of the monopoly. It isalso intended to give the court in revocation proceedings a jurisdiction which mirrors that of the Patent Office under section 14(3) o[f] the E.P.O. under article 83 of the EPC, namely, to hold a patent invalid on the substantive ground that, as the E.P.O. said in Exxon/Fuel Oils (T 409/91)  O.J. E.P.O. 653, paragraph 3.3., the extent of the monopoly claimed exceeds the technical contribution to the art made by the invention as described in the specification. In the 1949 Act, this function was performed by another ground for revocation, namely that the claim was not ‘fairly based on the matter disclosed in the specification’ (section 32(1)(i)). The requirement of sufficiency was there