JPS60219041A - Coating film for polarizing plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a coating film for polarizing plates.

Polarizing plates are used in display devices, television filters, 3D movies, sunglasses, etc., and their structure is such that the polarizing film is coated with a coating film to protect it.

Conventionally, triacetate film has been used as this coating film because it has low optical anisotropy, but triacetate film has poor moisture resistance and the polarizing film deteriorates due to moisture absorption, so triacetate film has better moisture resistance. There is a desire for a coating film for polarizing plates with less optical anisotropy.

As a result of intensive studies to obtain a coating film for polarizing plates with excellent moisture resistance and low optical anisotropy, the inventors of the present invention, Nagisa et al., found that if a specific thermoplastic resin is formed by a specific manufacturing method, the above-mentioned We have discovered that a custom-made coating film for polarizing plates can be obtained, and have arrived at the present invention.

That is, the present invention reduces forged optical anisotropy (and The coating film for polarizing plates of the present invention has a moisture permeability of 200.j9/m·24. The coating film for polarizing plates of the present invention is an extruded thermoplastic resin film with low optical anisotropy and good moisture resistance, and its retardation value (hereinafter referred to as R value) is 20 m, a or less, more preferably 107 nμ or less. Note that the R value is a unit expressing the birefringence of the film, and the R value is a unit that expresses the birefringence of the film and the two refraction values perpendicular to the film. The absolute value of the difference in rates is expressed as the product of 1 n, -7'L21.

几='d + , , -7L21 However, nl is a refractive index in an arbitrary direction, and 7L2 is a refractive index in a direction orthogonal to 7L1.

If the R value exceeds 204μ, use a polarizing plate saw.
If it is used in a printing film, it is not preferable because it will cause streaks.

Also, its moisture permeability! 200jj/m.24Jl or less, more preferably 1009/rd.24 production or less.

If the moisture permeability exceeds 200 i/m·24 JL, it is not preferable because when used as a coating film for a polarizing plate, the polarizing film may change in quality or bulges may occur between the film and the coating film.

Here, moisture permeability refers to the amount of water vapor that passes through a unit area of a membrane material in a certain period of time, and is measured according to JIS Z0208.

The manufacturing method for this film is based on Japanese Patent Application No. 58-148140, and its percentage characteristics are as follows: A thermoplastic resin for polarizing plate coating film (hereinafter referred to as Resin A) is used as the core layer, and Resin A is non-adherent. thermoplastic south side (hereinafter referred to as resin B)
This is achieved by coextruding at least three layers with the outer layer, and a thermoplastic resin film having the desired density value h''-lower as the core layer is obtained.

The thermoplastic resin used as resin A in the present invention is a thermoplastic resin with excellent moisture resistance and good transparency, such as polyvinyl chloride open-face composition, polyamide, polyester, polycarbonate Examples include methyl methacrylate, methyl pentene resin, ionomer, JL polyether sulfone, and polyphenylene sulfide. Among these, vinyl chloride resin compositions and polycarbonates are preferred.

In addition, resin B is a resin that can be easily peeled off after multi-layer coextrusion with resin A. As a combination of resin A and resin B, for example, when resin A is a vinyl chloride side composition, resin and resin For example, combinations with low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, cellulose resin, etc. can be used. In this case, the combination with low-density polyethylene is particularly advantageous in obtaining the coating film for a polarizing plate of the present invention, since the extrusion temperatures of both resins are close to each other, making coextrusion easier. Other general combinations of resins can be found, for example, in the literature such as Plastic World, January 1980 issue, page 58.

The ratio of the resin A layer to the total thickness of the coextruded film is preferably 90 or less. If the ratio exceeds 90%, optical anisotropy may occur in the film of resin A, which is not desirable.

It is not necessary that only one type of resin B be used for both surface layers, and different resins may be selected for the surface layers of both images.

Furthermore, the number of layers may be increased instead of six. For example, 0BA
Combinations such as B(0) or BABAB are also possible.

In addition, the film thickness of resin A depends on its moisture permeability in order to be used as a coating film for polarizing plates.
A suitable thickness is 10 to 1000 μm, preferably 15 to 200 μm.

The film of the present invention thus produced is used as a polarizing film (C pasted, polarizing plate) as a coating film.

Taking advantage of this feature, it can be used in various fields such as display devices, television filters, 3D movies, and sunglasses.

Hereinafter, the present invention will be explained with reference to Examples.

Implementation 111 Using a 65m-14CHa 1m extrusion rock, two types of 6-layer feed blocks, a coat hanger type T-die, a cooling roll, and a take-up machine, 65m → vinyl chloride resin composition (Mitsui Vinicron 4000) was poured from the extruder side. LL (trademark) mixed with a stabilizer (hereinafter abbreviated as PVO)], low density polyethylene (Shiraishi Lexron F
-41 (trademark). Hereinafter, it will be abbreviated as LDPR. ), LDP a/p va/LDPE=20/40
/20 pm multilayer film was extruded. The conditions were that the resin temperature was 170° C. for both PVO and LDPE, and the sheet take-up speed was im/mlrn.

Next, the LDPE film was peeled off from the multilayer sheet, and the R value of the obtained film was measured using a polar microscope equipped with a Berenok convencator manufactured by Olympus Optical Co., Ltd., and found to be 8 mμ.

Further, its moisture permeability was measured according to JIS Z0208 and was found to be 559/rrl·24 JL.

Next, the above film was pasted on the 1If11 side of the polarizing film, and the polarizing plate was installed.The performance of the film was evaluated by incorporating it into a display device. It was confirmed.

Comparison 11 The vinyl chloride resin composition of Example 1 was extruded from a 65 mmφ extruder to obtain a film with a thickness of 40 μm.

The density value of this product was 35 mμ. Furthermore, when a polarizing plate was pasted onto both sides of the polarizing film and its performance was evaluated by incorporating it into a display, it was found to be unusable due to the presence of streaks.

patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Scope of Claims] 1) Co-extrusion of a thermoplastic resin with a non-adhesive thermoplastic resin in a state in which both sides are exposed, resulting in less optical anisotropy and Moisture permeability is 200g/
This coating film for polarizing plates is characterized by being a thermoplastic resin extrusion film with a size of 24 JL or less. 2) Thermoplastic resin extruded film has a retardation value of 2
The coating film for IJiii plate according to item 1 of the q1 requirement, which has a particle diameter of 0-μ or less. The coating film for a polarizing plate according to claim 1 or 2, wherein the thermoplastic resin is a vinyl chloride resin composition.