An object is to provide a polyvinyl acetal film which has excellent transparency and can suppress a thermal cracking phenomenon.
The above object is achieved by providing a polyvinyl acetal film in which a ratio between a composite modulus (GPa) of the highest part in a convex part and a composite modulus (GPa) of the lowest part in a concave part on a surface of a film on a side in contact with glass, calculated by a nanoindentation measurement using a scanning probe microscope, is 0.90 or less, when a laminated glass is formed. In addition, the above object is achieved by providing a polyvinyl acetal film in which a ratio between a hardness (GPa) of the highest part in the convex part and a hardness (GPa) of the lowest part in the concave part, calculated by the SPM nanoindentation measurement, is 0.90 or less.
目的是提供一种聚
乙烯醇缩醛薄膜,它具有优异的透明度,并能抑制热裂纹现象。
实现上述目的的方法是提供一种聚
乙烯醇缩醛薄膜,当形成层压
玻璃时,通过使用扫描探针显微镜进行纳米压痕测量,计算出薄膜与
玻璃接触一侧表面上凸部最高部分的复合模量(GPa)与凹部最低部分的复合模量(GPa)之比为 0.90 或以下。此外,通过提供一种聚
乙烯醇缩醛薄膜,其中通过
SPM 纳米压痕测量法计算出的凸面部分最高部分的硬度(GPa)与凹面部分最低部分的硬度(GPa)之比为 0.90 或更小,从而达到上述目的。