DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on January 21, 2026 has been entered.
Summary
The Applicant’s arguments and claim amendments received on January 21, 2026 have been entered into the file. Currently, claims 1-2 and 8 are amended; claims 4-6 are cancelled; and claims 12-17 are withdrawn; resulting in claims 1-3 and 7-11 pending for examination.
Claim Objections
Claim 1 is objected to because of the following informalities:
Regarding claim 1, the limitation in line 14 recites that “a base weight amount of the sheet is less than or equal to 350 g/m2,” and the limitations in lines 15-16 limit the variation in “base weight amount of the sheet” however, the language “base weight amount of the sheet” does not appear to be used in the specification. Paragraphs [0073]-[0075] of the specification discuss the quantity per unit area amount of the sheet, including the range greater than 50 g/m2 and less than 350 g/m2, which was included in claim 6 of the claim set filed August 12, 2025 using the language “weight per unit area amount of the sheet.” It is recommended to use the language included in the previously filed claim set, such that the limitation in claim 1 recites that “a weight per unit area amount of the sheet is less than or equal to 350 g/m2, a first variation in the weight per unit area amount of the sheet is less than or equal to 11%, a second variation in the weight per unit area amount of the sheet is less than or equal to 47 g/m2.”
Regarding claim 1, the limitation in line 18 recites that “a density of the sheet is 1.5 g/cm2 or more,” however, the units for density included in paragraph [0033] of the specification and in dependent claim 8 are provided in g/cm3. Given the disclosure in the specification and claim 8, and the standard units for density, it seems the claim is intended to provide the limitation in g/cm3. For the purposes of examination, the limitation is interpreted as “a density of the sheet is 1.5 g/cm3 or more.”
Appropriate correction is required.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claim 1, and by dependency claims 2-3 and 7-11 are rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Regarding claim 1, the claim recites that “a density of the sheet is 1.5 g/cm3 or more,” in line 18. This limitation is indefinite as it is not clear if the density is referring to the sheet as a whole, or the density of the plurality of carbon fibers, similar to the limitation in claim 8. In looking to the specification, paragraph [0033] discloses that the density of the plurality of the carbon fibers may be greater than or equal to 1.5 g/cm3 and less than or equal to 2.2 g/cm3. Based on this disclosure and the amendment to claim 8 in the claim set filed January 21, 2026, this limitation is interpreted as the density of the plurality of carbon fibers.
Regarding claims 2-3 and 7-11, these claims are rejected based on their dependency on claim 1.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-3 and 8-11 are rejected under 35 U.S.C. 103 as being unpatentable over Woehner, et al. (US 2018/0127906 A1) in view of Kanada, et al. (US 2024/0376616 A1).
Regarding claims 1, 3, and 8, Woehner teaches a thin carbon fiber non-woven fabric (¶ [0010], Ln. 1-7) used as an electrode material for battery applications, such as redox flow batteries (¶ [0027], Ln. 1-5). The carbon fiber non-woven sheet is subjected to a horizontal splitting process, which includes splitting a flat fabric over the entire area thereof between the surfaces thereof, such that two flat fabrics are obtained (a sheet including a first and second surface that face each other in a thickness direction; the cut section corresponding to the first or second surface) (¶ [0018], Ln. 8-12). The cutting process results in an accumulation of terminal carbon fibers (first carbon fiber) on the surface of the non-woven fabric layer (first carbon fiber includes at least one of a cut section facing the first surface and a cut section facing the second surface) (¶ [0026], Ln. 13-15). Woehner further teaches that the thickness of the separated layer is from 0.2 mm to 2 mm, within the claimed range of less than 2.2 mm. Woehner does not expressly teach that the width of the carbon fiber non-woven fabric is less than or equal to 900 mm and the length is within 500-2000 mm.
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to modify the size of the carbon fiber non-woven fabric to have a width less than 1000 mm and a length within 500 and 2000 mm based on the application of the fabric. One of ordinary skill in the art would recognize that the horizontal splitting process taught by Woehner could be applied to carbon fiber non-woven fabrics of varying sizes, and would find it obvious to use the process to split any of those fabrics. The scaling-up or scaling-down of the carbon fiber non-woven fabric subjected to the horizontal splitting process does not establish patentability over the prior art (MPEP 2144.04 (IV)(A)).
Woehner teaches that the layer is separated with a constant tensile force that allows thin layers less than 5 mm to be removed (¶ [0024], Ln. 1-5), further teaching that under the tensile force of a mechanical winder, the carbon fiber non-woven fabric is split into two split felts with consistent thicknesses (¶ [0025], Ln. 1-8). Woehner also teaches that the split surface is optically smooth and uniform (¶ [0037], Ln. 1-2). Woehner does not expressly teach that a first variation of thickness of the sheet is less than or equal to 11%, a second variation of thickness of the sheet is less than or equal to 16%, a first variation in the weight per unit area amount of the sheet is less than or equal to 11%, or a second variation in the weight per unit area amount of the sheet is less than or equal to 47 g/m2.
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to target the lowest variation in thickness and base weight amount of the sheet as possible. The reference teaches a process of splitting the carbon fiber non-woven fabric into two split felts with consistent thicknesses due to the tensile force applied to the fabric, further teaching that this process results in thicknesses that are consistent and a split surface that is smooth and uniform. Based on these teachings, one of ordinary skill in the art would find it obvious that the purpose of the splitting process is to split the carbon fiber non-woven fabric such that the split surfaces are uniform, and therefore have as little variation as possible. Thus, one of ordinary skill in the art would find it obvious to include a first variation of thickness of the sheet of less than or equal to 11%, a second variation of thickness of the sheet of less than or equal to 16%, a first variation in the weight per unit area amount of the sheet of less than or equal to 11%, and a second variation in the weight per unit area amount of the sheet of less than or equal to 47 g/m2, as one would be targeting the lowest variation possible.
Woehner teaches that the layers made of the carbon fiber non-woven fabric can be used as electrode material for battery applications (¶ [0027], Ln. 1-4), specifically teaching that the layers produced by the splitting method can be used for gas diffusion layers in fuel cells (¶ [0028], Ln. 1-4). Woehner does not expressly teach a weight per unit area of the sheet, porosity of the sheet, or density of the sheet, and therefore does not teach a weight per unit area of the sheet of less than or equal to 350 g/m2, a porosity of 75% or more, and a density of carbon fibers of 1.5 g/cm3 or more and 2.2 g/cm3 or less.
Kanada teaches a cathode diffusion layer for an electrolytic cell (¶ [0015], Ln. 1-6). Kanada teaches an example wherein carbon fiber paper is used as the cathode diffusion layer (¶ [0369], Ln. 1-3). Kanada teaches that the carbon fiber paper has a base weight of 63 g/m2, a real density of 1.75 g/cm3, and a porosity of 88.0% (Table 1, Example 13). As the carbon fiber paper used in Example 13 is a carbon fiber paper without any substrate or surface treatment, the real density is considered the density of the carbon fibers.
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to use a carbon fiber non-woven fabric a base weight of 63 g/m2, a real density of 1.75 g/cm3, and a porosity of 88.0% for the application of an electrode substrate based on the teachings of Kanada. It would be obvious to one of ordinary skill in the art that carbon fiber non-woven fabrics can have different properties based on their applications. Although Woehner does not expressly teach a weight per unit area amount of the sheet, density, or porosity, one of ordinary skill in the art would find it obvious to use a carbon fiber non-woven fabric having the same properties used in similar applications, in this case, an electrode substrate. Thus, one of ordinary skill in the art would be motivated to use a weight per unit area amount of the sheet of 63 g/m2, within the claimed range of less than 350 g/m2; a density of carbon fibers of 1.75 g/cm3, within the claimed range of 1.5 g/cm3 or more and 2.2 g/cm3 or less; and a porosity of 88%, within the claimed range of 75% or more.
Regarding claim 2, Woehner in view of Kanada teaches all of the limitations of claim 1 above. Woehner further teaches that the thickness of the separated layer is from 0.2 mm to 2 mm, overlapping the claimed range of greater than or equal to 0.5 mm. In the case where the claimed ranges "overlap or lie inside ranges disclosed by the prior art" a prima facie case of obviousness exists (MPEP 2144.05 (I)).
Regarding claims 9-11, Woehner in view of Kanada teaches an electrode meeting the limitations of claim 1 above. Woehner further teaches the carbon fiber non-woven fabric layers can be used to produce an electrode for a redox flow battery (battery system) (¶ [0027], Ln. 1-5). In order to produce a redox flow battery, the electrodes would be used to produce battery cells, which would be stacked to create cell stacks.
Claim 7 is rejected under 35 U.S.C. 103 as being unpatentable over Woehner, et al. (US 2018/0127906 A1) in view of Kanada, et al. (US 2024/0376616 A1) as applied to claim 1 above, and further in view of Shiraki, et al. (US 2019/0273264 A1), cited on IDS.
Regarding claim 7, Woehner in view of Kanada teaches all of the limitations of claim 1 above. Woehner does not expressly recite that the plurality of carbon fibers includes a carbon fiber having a plurality of pleats on a surface of the carbon fiber.
Shiraki teaches an electrode for a redox flow battery formed by modified cross-section fibers, each having a plurality of pleats in the surface thereof (¶ [0020], Ln. 1-4). Shiraki teaches that using carbon fibers with pleats in the surface thereof increase the specific surface area of the fibers, and therefore the reaction area of the electrode at which the electrolyte comes into contact with the electrode, reducing reaction resistance and increasing battery performance (¶ [0020], Ln. 5-10).
It would have been obvious to one of ordinary skill in the art, before the effective filing date of the claimed invention, to modify the carbon fiber non-woven fabric of Woehner in view of Kanada to include carbon fibers with pleats as taught by Shiraki. One of ordinary skill in the art would be motivated to make this change in order to increase the specific surface area of the fibers, reducing reaction resistance and increasing battery performance.
Response to Arguments
Response-Claim Rejections – 35 U.S.C. 103
In light of the Applicant’s amendment to claim 1 to specify properties of the electrode sheet and cancellation of claims 4-5, the previous rejections of claims 1-5 and 9-11 under 35 U.S.C. 103 over Woehner, et al. (US 2018/0127906 A1) are withdrawn. However, upon further consideration, the reference is applicable under 35 U.S.C. 103 and used in combination with Kanada, et al. (US 2024/0376616 A1) in the rejections above. Any arguments with respect to the reference that are still deemed valid will be addressed herein.
The Applicant argues, see pages 6-8 of the remarks filed January 21, 2026, that as the data presented shows evidence of criticality, it would not be obvious to modify the length and width of the carbon fiber non-woven fabric of Woehner.
This argument is not persuasive. It is acknowledged that the data provided shows significant increases in variation of thickness and variation of weight per unit area with an increase in electrode material length and width, however, the Applicant has not made it clear if these are the intended critical parameters and why they are critical. Further, in the case that the increased variation of thickness and weight are the intended unexpected results, it is not clear how a reduced sheet size resulting in less variation across the sheet is unexpected, as the area for variation is smaller with a reduced size. The Applicant points to Tables 1-3 of the instant specification to demonstrate evidence of criticality of the length and width of the electrode sheet, however, it is not clear which results are being used to demonstrate criticality. The Applicant has the burden of explaining the data in any declaration they proffer as evidence of non-obviousness (MPEP 716.02(b)(II)).
Additionally, as presented, the data in Tables 1-3 is insufficient to overcome the prima facie case of obviousness. It is noted that data is not presented at the upper end point for the length of the electrode sheet, as the first comparative example includes a length of 5000 mm compared to the claimed upper limit of 2000 mm, and data is not presented for electrode sheets below the claimed length of 500 mm. Similarly, the claimed upper limit for the width of the electrode sheet is 900 mm, however, the comparative examples include a lowest width of 1200 mm, which is combined with a length of 10,000 mm, well above the claimed upper limit of length. To establish unexpected results over a claimed range, applicants should compare a sufficient number of tests both inside and outside the claimed range to show the criticality of the claimed range (MPEP 716.02 (d)).
Lastly, it is noted that for the data in Table 3, the electrodes of Samples 1, 2, 101, and 102 are cut to a set width of 350 mm and length of 500 mm and do not reflect the dimensions provided in Tables 1 and 2. In the case that these results are relied upon, it is further noted that the current efficiency and cell resistivity results are obtained from a unit cell battery including a positive electrode, membrane, negative electrode, and electrolytic solution. Thus, in the case that these results are relied upon, it is noted that the claims are not commensurate in scope with the results.
Conclusion
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/SARAH J JACOBSON/Examiner, Art Unit 1785
/MARK RUTHKOSKY/Supervisory Patent Examiner, Art Unit 1785