Method for producing optical film, optical film, polarizing plate and display

Abstract

A method for producing an optical film by a solution spreading film deposition method, in which a poor stripping region of a metal support can be eliminated by spreading dope on the surface of the metal support after a surface treatment film is formed on the surface of the metal support by atmospheric pressure plasma processing or excimer UV processing. Consequently, limitation on the conditions of film production is reduced and productivity is enhanced. Furthermore, since stripping of the film is enhanced, lateral variation in stripping position is reduced and variation in retardation value is reduced sharply, and thereby an optical film having optical characteristics excellent in transparency and planarity can be produced. Consequently, a method for producing an optical film, an opticalfilm, a polarizing plate and a display which can meet the demands of a high quality thin and wide protective film for polarizing plate can be provided.

Description

technical field [0001] The present invention relates to a method for producing an optical film, an optical film, a polarizer, and a display device, and the optical film can be used for various functional films, etc., and the functional film is a protective film for a polarizer used in a liquid crystal display device (LCD), Retardation films, viewing angle expansion films, anti-reflection films used in plasma displays, etc. Background technique [0002] In recent years, liquid crystal display devices have been gradually used in televisions or large monitors due to the improvement of their image quality and the improvement of high-definition technology. The cost and the like place strong demands on the material of the liquid crystal display device, and at the same time, widening of the optical film is also required. [0003] In addition, in recent years, in order to adapt to the rapid growth of LCD TVs, the demand for optical films has also increased rapidly, and there is a s...

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Problems solved by technology

[0004] Generally, the solution casting film-making method includes casting a resin solution (hereinafter referred to as a slurry) containing a thermoplastic resin and an additive on a support made of a rotary-driven stainless steel endless belt, a drum or a roller, In this film-forming method, although it varies somewhat depending on the type of resin, the proportion of poor solvent, etc., the mass ratio of the total solvent amount to the solid content of the film is about 60% by mass, and there is a possibility that the film is supported from the metal. Areas where the exfoliation force on the body is increased resulting in exacerbated exfoliation

[0005] In this region, the film cannot be peeled off from the metal support smoothly, accompanied by severe peeling unevenness and peeling sound, and at the same time, due to the unevenness, the film produces obvious step-like deformation extending in the width direction, so , had to adopt the conditions of avoiding this area in production, and was restricted in membrane production

[0006] The poor peeling area varies due to the type of slurry raw material, such as the type of resin, the addition ratio of poor solvent, and the temperature of the film during peeling. Both have the above-mentioned poor peeling area

[0007] In order to avoid such a poor peeling area, for example, the film production is selected on the so-called high residual solvent (area where the amount of residual solvent is higher than the above-mentioned area where the peeling force increases) of the cast film (hereinafter referred to as wet film). During conditions, especially when the film thickness of the product is manufactured as a film below 40 μm, there is a problem that even if the temperature of the drying air blown in order to dry the cast film on the support is lowered, the evaporation rate of the solvent dichloromethane Large, drying will continue, unable to achieve high residual solvent stripping conditions

[0008] Therefore, in order to achieve high residual solvent stripping, the production speed of the film can only be increased. In this case, there are problems such as the need to increase the capacity of the solvent recovery equipment, or to extend the post-drying step in order to reduce the amount of residual solvent in the product film to a limit value, etc. Carry out large-scale equipment renovation

However, when a low residual solvent stripping condition is formed, the drying of the casting film enters the deceleration drying period. Therefore, if the drying time on the metal support is not significantly prolonged, the residual solvent cannot be reduced, and thus the production has to be greatly reduced. The problem of production speed

[0010] In this way, the conventional production had the following problem: due to the existence of poor peeling and residual solvent regions of the metal support, the film production had to be performed at a production rate that was significantly lower than the capacity of the equipment.

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