Transparent conductive piezoelectric film and touch panel
To suppress change in a surface resistance value under a high-temperature or high-humidity environment in a transparent conductive piezoelectric film including a transparent piezoelectric film made of a fluororesin. A transparent conductive piezoelectric film includes a transparent piezoelectric film made of a fluororesin, a transparent coating layer, and a transparent electrode stacked in this order. The total thickness of the coating layer is 0.6 to 4.5 μm. When the transparent conductive piezoelectric film is left to stand in a specific high-temperature environment, the ratio of a resistance value after being left in the environment to a ratio of a resistance value before being left in the environment is 1.30 or less.
1 . A transparent conductive piezoelectric film comprising, by sequentially stacking:
a transparent piezoelectric film made of a fluororesin;
a transparent coating layer; and
a transparent electrode,
wherein a thickness of the transparent piezoelectric film is from 20 μm to 200 μm,
a total thickness of the transparent coating layer is 0.6 to 4.5 μm, and
when the transparent conductive piezoelectric film is left in an environment of 85° C. for 250 hours, a ratio of a surface resistance value after being left in the environment to a surface resistance value before being left in the environment is 1.30 or less.
2 . The transparent conductive piezoelectric film according to claim 1 ,
wherein a linear expansion coefficient determined by thermomechanical analysis is 310×10 −6 K −1 or less.
3 . The transparent conductive piezoelectric film according to claim 1 ,
wherein the transparent electrode is made of an indium-tin composite oxide, and a peak of the indium-tin composite oxide is not detected in X-ray diffraction.
4 . The transparent conductive piezoelectric film according to claim 1 ,
wherein the transparent coating layer is made of a (meth)acrylic acid ester resin.
5 . A touch panel comprising:
the transparent conductive piezoelectric film described in claim 1 .
6 . A method for manufacturing a transparent conductive piezoelectric film comprising:
a step of forming a transparent coating layer having a total thickness of 0.6 to 4.5 μm on at least one surface of a transparent piezoelectric film made of a fluororesin; and
a step of forming a transparent electrode,
wherein, when the transparent conductive piezoelectric film is left in an environment of 85° C. for 250 hours, a ratio of a surface resistance value of the transparent electrode after being left in the environment to a surface resistance value of the transparent electrode before being left in the environment is 1.30 or less.
7 . The method for manufacturing a transparent conductive piezoelectric film according to claim 6 ,
wherein in the step of forming the transparent electrode, a thin film of an indium-tin composite oxide is formed as the transparent electrode on the transparent coating layer by a reactive sputtering method using a sintered body containing indium oxide and tin oxide as a raw material.
8 . The method for manufacturing a transparent conductive piezoelectric film according to claim 7 ,
wherein in the step of forming the transparent electrode, reactive sputtering is performed at a temperature of 80° C. or less.
9 . The method for manufacturing a transparent conductive piezoelectric film according to claim 7 ,
wherein an annealing treatment for the transparent electrode formed in the step of forming the transparent electrode is not performed.
10 . The method for manufacturing a transparent conductive piezoelectric film according to claim 6 ,
wherein an annealing treatment for the transparent electrode formed in the step of forming the transparent electrode is not performed.