Optical compensating sheet , polarizing plate and liquid crystal display device

Abstract

The invention provides an optical compensative sheet for modifying display quality of a liquid crystal display device. An optical compensative sheet using a cellulose acylate, of which the in-plane retardation value (Re) is 0 nm ≤ Re < 20 nm, the thickness (d) is 10 &mgr;m < d < 85 &mgr;m, the average ((Vmin+Vmax)/2) of minimum value (Vmin) and maximum value (Vmax) of the sonic velocity measured in plane of film is 2.2 km/sec < (Vmin+Vmax)/2 < 2.5 km/sec, and the proportion (Vmin/Vmax) of minimum value of the sonic velocity measured in plane of film as compared to the maximum value is 1.01 < Vmin/Vmax/2 < 1.02. An optical compensative sheet made by laminating an aligned membrane and an optically anisotropic layer in this order onto a transparent support comprising at least a micro particle having an average primary particle diameter of less than 80 nm and thickness of more than 20 &mgr;m but less than 80 &mgr;m, wherein the arithmetic average roughness (Ra) of surface unevenness related to a surface at the aligned membrane side of transparent support is more than 0.0002 &mgr;m but less than 0.1 &mgr;m measured according to JIS B0601-1994, the ten-points average roughness (Rz) is more than 0.0002 &mgr;m but less than 0.3&mgr;m, as well as the maximum height (Ry) is more than 0.002 &mgr;m but less than 0.5 &mgr;m, Re value of transparent support is more than 2 nm but less than 200 nm and the Rth value is more than 50 nm but less than 400nm. An optical compensative sheet using a cellulose acylate film comprising a cellulose acylate film having an acylation index of 59.0 to 61.5%, of which the surface is treated by soapnification and contact angle with water of the surface is more than 30 DEG but less than 70 DEG.

Description

technical field [0001] The present invention relates to an optical compensation sheet for improving the viewing angle (also referred to as viewing angle) of a liquid crystal display device, a polarizing plate (also referred to as a polarizer) using the optical compensation sheet, and a liquid crystal display device. Background technique [0002] A liquid crystal display device usually consists of a liquid crystal cell, a polarizing plate, and an optical compensation film (retardation plate). In a transmissive liquid crystal display device, two polarizers are installed on both sides of the liquid crystal unit, and one or two optical compensation sheets are disposed between the liquid crystal unit and the polarizer. For a reflective liquid crystal display device, a reflective plate, a liquid crystal unit, an optical compensation sheet, and a polarizing plate are sequentially arranged. [0003] As a general example, a liquid crystal cell is composed of rod-shaped liquid crysta...

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Problems solved by technology

[0016] In order to respond to the demand for cost reduction due to weight reduction and improvement in productivity, thinning of the transparent support is also strongly desired, but the strength is reduced due to thinning, and it is practically used especially when used in a large liquid crystal display device. question on

Such a problem cannot be fully solved according to the current proposal, and it is strongly desired to increase the strength of the support, but if the strength of the support is only increased, the problems of poor optical properties and reduced visibility will arise.

[0017] In addition, in a liquid crystal display device composed of a large display panel of 20 inches or more, it will be found that there are problems that have not been fully studied in the prior art.

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