Cellulose acylate laminate film, method for producing same, polarizer and liquid crystal display device

Abstract

The present invention provides a cellulose acylate laminate film having high expressibility, little optical unevenness and good releasability from a support. The cellulose acylate laminate film is characterized in that the cellulose acylate laminate film is obtained by preparing a skin layer B containing the cellulose acylate satisfying the formula (2) and a core layer containing a cellulose acylate satisfying the formula (1) into film on the support according to the order, wherein at least one of the core layer or the skin layer B contains a retardation-controlling agent, and the cellulose acylate laminate film is formed by stretching. Formula (1), Z1 is more than 2.0 but less than 2.7, wherein Z1 represents a total degree of acyl substitution of cellulose acylate; formula (2) Z2 is morethan 2.7, wherein Z2 represents a total degree of acyl substitution of cellulose acylate.

Description

technical field [0001] The present invention relates to a cellulose acylate laminated film, a method for producing the same, a polarizing plate, and a liquid crystal display device. More specifically, it relates to a laminated film obtained by co-casting cellulose acylate with a low degree of substitution and cellulose acylate with a high degree of substitution, its manufacturing method, a polarizing plate, and a liquid crystal display device. Background technique [0002] In order to improve the viewing angle and color tone variation of liquid crystal display devices, retardation films having specific retardation values ​​and combinations thereof are currently used. [0003] As a main raw material of such a retardation film, it is known that cellulose acylate is advantageous, and that the optical characteristics of the film depend on the degree of substitution of acyl groups of the cellulose acylate. In particular, since cellulose acylate with a low degree of substitution ...

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Problems solved by technology

[0010] However, when the inventors of the present invention produced a retardation film by co-casting using cellulose acylate with a low degree of substitution and cellulose acylate with a high degree of substitution and excellent peelability from a support, they found that the optical Large variations in characteristics make it unsuitable for use as a retardation film

Furthermore, the inventors of the present invention conducted intensive research and found that it is extremely difficult to make the film thickness distribution of each layer uniform in the lateral direction in co-casting. sexual deviation

In particular, it was found that when there is a difference in the optical development rate due to the stretching ratio in the case of stretching, the deviation of the optical characteristics is further increased.

That is to say, when the retardation film is produced by co-casting using cellulose acylate with a low degree of substitution for the purpose of realizing optical visualization that cannot be achieved by conventional cellulose acylate optical films, although the peeling effect is improved, resistance, but the deviation of optical characteristics increases

[0011] In addition, it has also been tried to use cellulose acylate with a high degree of substitution in the core layer and the surface layer, and to add a retardation control agent to each layer, but the optical properties are still low. The performance of the optical compensation film is not sufficient

[0012] In this way, the actual situation is that it is impossible to manufacture a cellulose acylate film that has both good releasability from the support and good optical properties.

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