Laminated film

Abstract

Provided is a laminated film comprising at least three layers laminated in the thickness direction, wherein the in-plane retardation (Re) is 0-400 nm, the out-of-plane retardation (Rth) is 0-1500 nm, the Re variation in the width direction is 18% or less, the film thickness is 40 microns or less, and the film width is 400 mm or more. Thus, the laminated film is suitable for use as a polarizer for a liquid-crystal display, and exhibits high definition without color unevenness, especially when applied to a large-screen liquid-crystal display.

Description

technical field [0001] The present invention relates to a laminated film that can be suitably used as a polarizing plate protective film. Moreover, it is related with the polarizing plate which uses this laminated film as a polarizing plate protective film. Background technique [0002] Thermoplastic resin films, among which biaxially stretched polyester films have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance, so they are used as base materials in most applications such as magnetic recording materials and packaging materials Membranes are widely used. Especially in recent years, in the field of flat panel displays and touch panels, the demand for various optical films such as polarizing plate protective films and transparent conductive films has increased. Among them, for polarizing plate protective films, low moisture permeability, mechanical strength and The replacement of the conv...

AI Technical Summary

Problems solved by technology

[0008] However, the conventionally studied biaxially stretched polyester film has a higher retardation (Retardation: retardation) than the TAC film due to the orientation of the polymer during stretching. The interference color caused by the delay in the display is generated, and the quality of the displayed image is degraded

In order to solve this problem, a delay (sometimes expressed as a delay) control method has been proposed, but it is still not sufficient to satisfy both the degree of delay and the deviation.

For example, a retardation of 400 nm or less has been proposed for a laminated film, but since the thickness retardation is large, there is a problem that it cannot be used as a polarizing plate for a liquid crystal display (Patent Document 1)

In addition, a polyester film for polarizer protection has been proposed, but the phase difference is large, and suppression of interference color and iridescent unevenness is insufficient (Patent Document 2)

A polyester film for polarizer protection with UV cut performance and a phase difference of 400nm or less was proposed, but the film production conditions due to low transmittance and increased bowing were adopted, so it has The problem that the deviation of the phase difference is large (Patent Document 3)

That is, when a biaxially stretched film is produced, there is a difference in the orientation state of the polymer in the film width direction. Therefore, for example, even if a part of the film can achieve the target low retardation, it can be used for a large screen. For a large-area film of a display, a low-retardation film cannot be uniformly obtained, and the product yield is lowered, and problems such as high cost remain.

In addition, since the retardation is proportional to the film thickness, it can also be suppressed by reducing the film thickness at the level of several μm, but due to the extremely thin film, the handleability will be reduced, and it is not practical for the application of the polarizing plate protective film.

Further, the polarizing plate protective film used in the outermost layer needs to have high UV cutoff, and the cost increase caused by the addition of a large amount of ultraviolet absorbing materials, process pollution, color change, etc. have become problems

Images