DETAILED ACTION
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claims 1-10 are pending as filed on 7/2/2024.
Election/Restrictions
Applicant's election with traverse of species wherein the polyimide is formed from 6FDA as tetracarboxylic dianhydride, TFMB as diamine and wherein the inorganic particle is strontium carbonate in the reply filed on 2/2/2026 is acknowledged. The traversal is on the ground(s) that the species are sufficiently related such that there would be no search burden. This is not found persuasive for the reasons set forth in paragraph 5 of the requirement mailed on 12/1/2025. The requirement is still deemed proper and is therefore made FINAL.
Claim Rejections - 35 USC § 103
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.
Claim(s) 1-10 is/are rejected under 35 U.S.C. 103 as being unpatentable over Jung et al (US 2011/0311796) in view of Sato (WO 2016/147997; English equivalent US 2017/0275425 cited herein) and Koike et al (JP 2004/035347; included machine translation cited herein).
As to claims 1-6, 9 and 10, Jung discloses a polyimide film that is colorless and transparent, has a low birefringence, and is suitable to be utilized for flexible display substrates [0024, 0036]. Jung teaches that the aromatic dianhydride and diamine components of the polyimide are not particularly limited, and names both 6FDA and 2,2’-TFDB among monomers to be included [0038-9]. Jung exemplifies a polyimide formed from 6FDA and 2,2’-TFDB in Example 3 [0062], meeting the elected species (and having a structure encompassed by instant General formulas 1 and 3 recited in claims 2 and 5). A polyimide from 6FDA and TFDB is entirely aromatic, i.e., 100% of hydrogen atoms are directly bound to an aromatic ring, meeting instant claim 3.
Jung teaches that the polyimide film has an average transmittance of 85% or more at 380-780 nm for a film thickness of 25-100 microns [0034], which meets the presently recited range of 80% or more total light transmittance at a thickness of 10 micron.
Jung further teaches that a polyimide film may be manufactured using a polyamic acid solution, and a filler may be added to the polyamic acid solution. Jung names several examples of suitable inorganic fillers [0044]. Jung further teaches that when a film has a low birefringence, the distortion of an image is reduced [0032], and therefore a film for application to LCDs preferably has a birefringence as close to zero as possible [0033].
However, Jung fails to specifically teach inorganic particles having refractive indices as presently recited, and fails to teach a size shrinkage ratio and a birefringence index of 0.020 or less as presently recited.
Sato teaches that polyimide is being applied to a wide range of fields [0002], and teaches that a stretched film is preferred over a non-stretched film in consideration of enhancement of mechanical strength and heat resistance of the film [0141]. Sato describes methods for stretching a pre-formed polyimide film in [0146-152] for enhancement of physical properties by stretching [0149], and teaches that biaxial stretching is preferable in consideration of reduction in anisotropy (i.e., birefringence) [0145].
Koike discloses that an optical material made of a polymer resin is generally lighter weight and lower in cost and superior in processability and productivity compared to optical glass [0003], but that conventional polymeric materials exhibit birefringence [0004]. Koike teaches that in various processes for forming optical resins into optical devices in which a force is exerted to orient a main chain, such as stretching, a birefringence occurs, and there is an increasing need to avoid such problems [0014-15]. Koike teaches a method for producing strontium carbonate having an orientation birefringence, and using it to provide non-birefringent optical material containing the particulate strontium carbonate [0001]. In particular, Koike teaches utilizing a technique known as crystal doping in which the orientation birefringence of a polymer resin and inorganic fine particle cancel each other out [0020-21]. The long axis (major axis) of the strontium carbonate has a refractive index of 1.520 [0056], which is smaller than the refractive indices of each of the other optical axis directions (i.e., directions perpendicular to the major axis) [0055, 0080].
Considering Koike’s disclosure ([0014-15]) as discussed above, it was known in the art to orient optical resins by stretching. In view of Sato’s disclosure ([0141, 0149]) discussed above, it was known in the art that stretching a polyimide film results in enhancement of physical properties, such as mechanical strength and heat resistance. Both Koike ([0014-15]) and Sato ([0145]) further recognize that stretching a polymer resin can result in an undesired increase in birefringence/anisotropy. Therefore, in view of both Koike and Sato, the person having ordinary skill in the art would have been motivated to stretch a polyimide optical film in order to enhance physical properties of the film. Additionally, the person having ordinary skill in the art would have been motivated to add Koike’s strontium carbonate particles to a polymer (crystal doping technique) in order to reduce birefringence caused by orienting a polymer intended to be used as an optical substrate.
It would have been obvious to the person having ordinary skill in the art, therefore, to have prepared a polyimide film comprising inorganic particles and having low birefringence suitable for a flexible display substrate, as disclosed by Jung, by including a step of stretching Jung’s polyimide film, as disclosed by Sato, in order to improve physical properties (such as strength and heat resistance) of the film. It would have been additionally obvious to the person having ordinary skill in the art to have prepared a stretched polyimide film intended for applications requiring low birefringence, as disclosed by modified Jung, by utilizing Koike’s strontium carbonate inorganic particles as the inorganic filler disclosed by Jung, in order to reduce any birefringence in the polyimide film caused by the step of stretching/orientation to a value as close to zero as possible, as desired by Jung (including to within the range or 0.020 or less or 0.010 or less, as recited in instant claims 1 and 6).
As to the presently recited size shrinkage ratio:
According to the instant specification, in general, size shrinkage is observed in the in-plane direction of polyimide films, and in a polyimide film having a size shrinkage of 0.1% or more, it is clear that the polyimide film is a stretched film [0027].
Sato teaches a stretching ratio which is preferably 1.1 times or more and 2.5 times or less in both directions in order to achieve sufficient stretch orientation and enhancement of mechanical strength and heat resistance, while also avoiding breaking, defects and variation in orientation due to stretching [0147]. Sato further teaches performing heat fixation in order to suppress thermal shrinkage of the film in reheating [0152], and teaches heating within particular temperatures and durations in order to suppress shrinkage while also maintaining stretch orientation of the film [0153].
Considering Sato’s disclosure, the person having ordinary skill in the art would have been motivated to select an appropriate stretching ratio within a range of 1.1 to 2.5 in order to enhance properties of a polyimide film, while also avoiding defects and breaking due to stretching. Additionally, the person having ordinary skill in the art would have been motivated to select an appropriate temperature and duration within the ranges disclosed by Sato for thermally fixing a stretched film in order to suppress shrinkage, yet also maintain stretch orientation and minimize thermal history/deterioration. Therefore, it would have been obvious to the person having ordinary skill in the art to have formed a polyimide film, as suggested by modified Jung, by selecting any appropriate stretching ratio within the range taught by Sato, and, to have selected appropriate heat fixation conditions as taught by Sato, including selecting a stretching ratio and heat fixation conditions corresponding to a size shrinkage ratio within a range of 0.1% or more (or within a range of 0.1-40%, or 0.1 to 9.7%, as recited in claims 9 and 10, respectively).
As to claim 7, modified Jung suggests a film according to claim 1, as set forth above, wherein the film comprises strontium carbonate particles as disclosed by Koike. Koike further teaches that a high transparency is maintained at a particle addition concentration of 5 wt% or less [0054]. It would have been obvious to the person having ordinary skill in the art, therefore, to have selected any appropriate concentration of strontium carbonate particles within Koike’s range of 5 wt% or less in order to reduce birefringence while also maintaining sufficient transparency, including a concentration within the presently claimed range of 0.01 to 1.1 mass%.
As to claim 8, modified Jung suggests a film according to claims 1-7, 9 and 10, as set forth above. Modified Jung is silent as to the flex resistance recited in claim 8. However, every exemplified polyimide film in the instant specification has a flex resistance of 2 mm (Table 5). Modified Jung suggests a polyimide film formed from the same monomers, having the same inorganic particles, and formed via substantially the same method (imidization, stretching) as utilized to form the exemplified polyimide films. There is reasonable basis to conclude, therefore, that modified Jung suggests a polyimide film having substantially the same flex resistance property as the polyimide films shown in instant table 5 (which falls within the presently claimed range of 5 or less).
Conclusion
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/RACHEL KAHN/Primary Examiner, Art Unit 1766