PTAB

IPR2019-00709

CambRios Film Solutions Corp v. C3Nano Inc

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Metal Nanowire Inks
  • Brief Description: The ’301 patent discloses silver nanowire-based conductive inks used for making transparent conductive films. The claimed inks comprise an aqueous solvent, metal nanowires, a solid hydrophilic polymer binder (specifically a polymeric polyol), and a specific concentration range of soluble metal ions.

3. Grounds for Unpatentability

Ground 1: Anticipation by Chung - Claims 1-3, 10, and 16-17 are anticipated by Chung under 35 U.S.C. §102.

  • Prior Art Relied Upon: Chung (Application # 2014/0004371).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued Chung discloses every element of the independent claims. Specifically, Chung’s Example 6 describes mixing a silver ion solution (“Ag Ink-0.05”) with a silver nanowire solution (“Ag-0.5-NWs”) at a 1:1 weight ratio. Petitioner asserted this combination results in an ink meeting all limitations of claim 1: an aqueous solvent (Chung teaches water/ethanol), metal nanowires at 0.25 wt% (within the claimed 0.001-4 wt% range), a hydrophilic polymer binder of ethyl hydroxyethyl cellulose, which is a polymeric polyol (within the 0.05-5 wt% range), and soluble metal ions at 0.025 wt% (within the claimed 0.00025-0.5 wt% range). For claim 16, Petitioner argued Chung’s disclosure of UV-curable binder resins meets the "curable binder" limitation. Dependent claims 2 and 3 are met because Chung’s binder is a polysaccharide and cellulose-based.

Ground 2: Obviousness over Yamakawa - Claims 1-5, 7-10, 16-18, and 20 are obvious over Yamakawa under 35 U.S.C. §103.

  • Prior Art Relied Upon: Yamakawa (Japanese Application Publication No. 2012-216535).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Yamakawa discloses an ink containing an aqueous solvent, silver nanowires (0.17 wt% in an example), and a hydrophilic polymer binder (hydroxyethyl cellulose, a polymeric polyol). While Yamakawa does not disclose an explicit weight percent of soluble metal ions, it teaches adding soluble silver salts (e.g., silver nitrate) to the ink for the same purpose as the ’301 patent: to "promote fusion" of nanowires and increase conductivity.
    • Motivation to Combine: This ground is based on a single reference, with the motivation for the final limitation (the amount of soluble ions) being routine optimization. Petitioner argued that determining an operative amount of silver salt to add would have been a matter of routine experimentation for a person of ordinary skill in the art (POSITA).
    • Expectation of Success: A POSITA would have had a reasonable expectation of success, as adding salts to fuse nanowires was a known technique. Petitioner asserted that reasonable starting points for experimentation, such as a 1:1 weight ratio of ions to nanowires (resulting in 0.17 wt% ions) or preserving preferred component ranges, would lead to a concentration falling squarely within the claimed range.

Ground 3: Anticipation by Allemand ’478 - Claims 1-5 are anticipated by Allemand ’478 under 35 U.S.C. §102.

  • Prior Art Relied Upon: Allemand ’478 (Application # 2013/0001478).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued that this reference, which was overcome during prosecution, does in fact anticipate the claims. The patent owner allegedly prevailed during prosecution by submitting calculations for soluble silver ions that were based on the false assumption that only low-solubility silver chloride was present, while ignoring Allemand ’478’s express disclosure of significant levels of highly soluble silver nitrate.
    • Key Aspects: The core of this ground is a corrected calculation. Petitioner applied the patent owner's own calculation methodology to the nitrate levels disclosed in Allemand ’478's Table 2 (60 ppm of nitrate ions in an unpurified nanowire concentrate). This calculation yields a soluble silver ion concentration of 0.01044 wt%, which is over 40 times the claimed lower limit of 0.00025 wt% and well within the claimed range. Petitioner argued this correction demonstrates that Allemand ’478, when read properly, teaches every element of the claims.

  • Additional Grounds: Petitioner asserted additional obviousness challenges based on Chung alone (for pH and settling limitations in claims 7-9 and 20), Chung in view of Allemand ’059 (for solvent ratios in claims 4-6, 11-15, and 18-19), and Yamakawa in view of Allemand ’059.

4. Relief Requested

  • Petitioner requests institution of IPR and cancellation of claims 1-20 as unpatentable.