PTAB

IPR2019-00709

Cambrios Film Solutions Corporation v. C3NANO INC.

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1. Case Identification

2. Patent Overview

  • Title: Metal Nanowire Inks
  • Brief Description: The ’301 patent is directed to stable, silver nanowire-based conductive inks used for making transparent conductive films. The claimed inks comprise an aqueous solvent, metal nanowires, a hydrophilic polymer binder that is a polymeric polyol, and a specific concentration of soluble metal ions ranging from about 0.00025 wt% to about 0.5 wt%.

3. Grounds for Unpatentability

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

  • Prior Art Relied Upon: Chung (Application # 2014/0004371).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Chung discloses every element of the independent claims. Chung's Example 6 describes mixing two solutions: an "Ag Ink-0.05" solution (Table 1) and an "Ag-0.5-NWs" solution (Table 2). Petitioner’s calculations showed the resulting ink contains 0.25 wt% silver nanowires and 0.025 wt% soluble silver ions (from silver nitrate), both falling within the claimed ranges. Chung also discloses ethyl hydroxyethyl cellulose as a binder, which Petitioner asserted is a polysaccharide and therefore a polymeric polyol, meeting the binder limitation. Dependent claims reciting a polysaccharide binder (claim 2), a cellulose-based binder (claims 3 and 17), and a curable binder (claim 10) were also allegedly disclosed.

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

  • Prior Art Relied Upon: Yamakawa (Japanese Patent Application Publication No. 2012-216535).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that Yamakawa teaches conductive inks with silver nanowires and a hydrophilic polymer binder (hydroxyethyl cellulose, a polymeric polyol). Yamakawa explicitly teaches adding soluble silver salts, such as silver nitrate, to the ink to "promote fusion" of the nanowires. While Yamakawa does not disclose a specific weight percent for the soluble metal ions, Petitioner argued that determining an effective amount would have been a matter of routine optimization for a person of ordinary skill in the art (POSITA). Yamakawa's preferred ranges for solid components also allegedly overlap with the claimed ranges.
    • Motivation to Combine (for §103 grounds): This ground is based on a single reference. The motivation was to optimize a known variable (soluble salt concentration) for its known purpose (nanowire fusion).
    • Expectation of Success: A POSITA would have a reasonable expectation of success because adding salts to fuse nanowires was a known technique. Experimenting with different concentrations to find an optimal value that falls within the broadly claimed range was a standard and predictable practice in the field.

Ground 3: Anticipation of Claims 1-5 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 the ’301 patent was only granted because the applicant overcame an anticipation rejection over Allemand ’478 by submitting erroneous calculations to the examiner. During prosecution, the applicant allegedly calculated the soluble silver ion concentration in Allemand ’478 based only on silver chloride, ignoring Allemand ’478’s express disclosure of significant levels of highly soluble silver nitrate.
    • Key Aspects: Petitioner asserted that a correct calculation based on Allemand ’478’s disclosure of 60 ppm of nitrate ions (from silver nitrate) in its unpurified nanowire concentrate yields a soluble silver ion concentration of 0.01044 wt%. This value falls squarely within the ’301 patent's claimed range of 0.00025 wt% to 0.5 wt%. As Allemand ’478 also discloses all other claim elements—including silver nanowires, an aqueous solvent, and a hydrophilic polymer binder (HPMC, which is a polymeric polyol)—Petitioner concluded that Allemand ’478 anticipates the claims.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including grounds that claims 7-9 and 20 are obvious over Chung alone and that various claims are obvious over Chung or Yamakawa in view of Allemand ’059 (Application # 2012/0097059). These combinations were primarily used to teach specific solvent ratios, pH ranges, and stability characteristics not explicitly enumerated in the primary references.

4. Relief Requested

  • Petitioner requests institution of an inter partes review and cancellation of claims 1-20 of the ’301 patent as unpatentable.