Claims
- 1. A crystalline vinylidene fluoride copolymer film, having a parallel light transmittance of 85% or higher when measured at a film thickness of 30 microns and a coefficient of absorption of 2.35.times.10.sup.3 /m or below according to Lambert's law for determining a parallel light transmittance for variable film thickness; said vinylidene fluoride copolymer film being a film of a vinylidene fluoride copolymer having a crystalline melting point of 140.degree. C. or higher obtained from a mixture of the vinylidene fluoride copolymer with a solvent, said copolymer having an inherent viscosity of 3.0 dl/g or higher, when measured as a solution dissolved in a solvent with a greater solubility selected from dimethylacetamide and dimethylformamide at a concentration of 0.4 g/dl and a temperature of 30.degree. C., and consisting essentially of the .beta.-phase crystalline structure.
- 2. A vinylidene fluoride copolymer film as claimed in claim 1, wherein said vinylidene fluoride copolymer is non-crosslinked.
- 3. A vinylidene fluoride copolymer as claimed in claim 1, wherein said vinylidene fluoride copolymer film has been obtained by polymerization at -50.degree. to 80.degree. C.
- 4. A vinylidene fluoride copolymer film as claimed in claim 1, wherein said copolymer comprises 30 to 95 mole % of vinylidene fluoride and the remainder of a monomer copolymerizable with vinylidene fluoride.
- 5. A vinylidene fluoride copolymer film as claimed in claim 1, wherein said copolymer comprises 50 to 90 mole % of vinylidene fluoride and the remainder of a monomer copolymerizable with vinylidene fluoride.
- 6. A vinylidene fluoride copolymer film as claimed in claim 4, wherein said monomer copolymerizable with vinylidene fluoride is selected from the group consisting of vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and ethylene.
- 7. A vinylidene fluoride copolymer film as claimed in claim 1, which has a parallel light transmittance of 87% or higher at a film thickness of 30 microns.
- 8. A vinylidene fluoride copolymer film as claimed in claim 1, which is in the form of an isolated film independent of a substrate.
- 9. A vinylidene fluoride copolymer film as claimed in claim 1, which is in the form of a coating.
- 10. A vinylidene fluoride copolymer film as claimed in claim 1, which is a cast film.
- 11. A process for producing a vinylidene fluoride copolymer film, which comprises the steps of: providing a vinylidene fluoride copolymer having an inherent viscosity of 3.0 dl/g or higher, when measured as a solution dissolved in a solvent with a greater solubility selected from dimethylacetamide and dimethylformamide at a concentration of 0.4 g/dl and a temperature of 30.degree. C. and consisting essentially of the .beta.-phase crystalline structure,
- mixing said vinylidene fluoride copolymer with a polar solvent,
- forming the resultant mixture in a film on a substrate, and
- evaporating off the solvent to form a dry film of the vinylidene fluoride copolymer.
- 12. A process for producing a vinylidene fluoride copolymer film as claimed in claim 11, wherein said polar solvent is selected from the group consisting of dimethylacetamide, dimethylformamide, methyl ethyl ketone, dimethyl sulfoxide, cyclohexanone and acetone.
- 13. A process for producing a vinylidene fluoride copolymer film as claimed in claim 11, wherein the mixture is formed into a film by casting.
- 14. A process for producing a vinylidene fluoride copolymer film as claimed in claim 13, wherein the mixture contains the vinylidene fluoride copolymer at a concentration of 0.3 to 20% by weight.
- 15. A process for producing a vinylidene fluoride copolymer film as claimed in claim 11, wherein said vinylidene copolymer is a non-crosslinked polymer formed by polymerization at a temperature of -50.degree. to 80.degree. C.
Priority Claims (1)
Number |
Date |
Country |
Kind |
58-148019 |
Aug 1983 |
JPX |
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Parent Case Info
This application is a continuation-in-part of now abandoned application Ser. No. 640,596 filed Aug. 14, 1984.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4335238 |
Moore |
Jun 1982 |
|
4435475 |
Sasaki et al. |
Mar 1984 |
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Foreign Referenced Citations (1)
Number |
Date |
Country |
1173552 |
Dec 1969 |
GBX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
640596 |
Aug 1984 |
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