JPS62240905A - Polarizing film - Google Patents

Abstract

PURPOSE:To provide high durability and high degree of polarization by adsorbing a dichromatic dye on a PVA film, orienting the same in substantially one direction and subjecting the film to an impregnation treatment of metallic ions and boric acid and subsequent heating treatment in a tense state. CONSTITUTION:The PVA film subjected to the adsorption of the dichromatic dye and orientation is impregnated with the metallic ions and boric acid and is then subjected to the heating treatment in the tense state. A method for immersing the film into a treating soln. is preferable as the method to adsorb the metallic ions and boric acid on the film and is executed at the timing of uniaxially stretching the film after the adsorption of the dichromatic dye and orientation and immersing the film in the tense state into the treating soln. The heating treatment is executed in the tense state for 1-120min at >=90 deg.C. The amts. of the impregnation of the metallic ions and boric acid in the polarizing film are specified to 0.2-20mg in terms of metal per g of the film and 0.3-30mg in terms of boron per g of the film. The polarizing performance, dimensional stability and wet heat resistance are thereby remarkably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polarizing film that has excellent durability and polarizing ability.

In recent years, the demand for polarizing films has increased significantly as the range of use of liquid crystal display devices has expanded.

In particular, in-vehicle liquid crystal display devices have a very large potential demand, and polarizing films used therefor are required to have higher durability and a higher degree of polarization than ever before.

[Conventional technology]

As polarizing films based on conventionally known polyvinyl alcohol films, the following are known.

(1) Polyene formed by dehydration treatment and oriented in substantially one direction (2) Iodine adsorbed and oriented (3) Dichroic dye adsorbed and oriented [solved by the invention] [Problems to be Solved] Among these, the one in (1) is inferior to the other two in polarization performance and inferior to (3) in heat resistance.

Although the material (2) has excellent polarization performance, it has extremely low heat resistance and is difficult to adjust the hue.

Although the polarizing performance of (3) is lower than that of (2), it has the advantage of excellent heat resistance and easy adjustment of hue. However, this product has low moisture resistance and needs to be laminated with a protective film, etc. However, it still does not have sufficient moisture and heat resistance, and if exposed to high temperatures for a long time, optical performance may deteriorate, peeling, and bubbles may occur. There are drawbacks such as the occurrence of warping and the like.

Therefore, the object of the present invention is to eliminate the drawbacks of these conventionally known techniques and to obtain a polarizing film having high durability and a high degree of polarization.

[Means to solve the problem]

In view of these drawbacks of the conventional methods, the present inventors conducted intensive research and found that the material described in (3) above was impregnated with metal ions and boric acid, and then heated under tension to improve polarization performance and dimensional stability. We succeeded in significantly improving the heat and humidity resistance.

Accordingly, the present invention is a polarizing film obtained by impregnating a polyvinyl alcohol film on which a dichroic dye is adsorbed and oriented with metal ions and boric acid, and then heat-treated under tension.

Examples of the polyvinyl alcohol film used in the present invention include polyvinyl alcohol film and polyvinyl alcohol derivative films such as polyvinyl formal film, polyvinyl acecool film, and saponified poly(ethylene-vinyl acetate) copolymer film. I can do it.

As a method for adsorbing and orienting dichroic dyes on these polyvinyl alcohol films, normal methods can be applied, and as the dichroic dyes, dichroic direct dyes, disperse dyes, acid dyes, etc. can be used. I can do it.

The metal ions used in the present invention include magnesium,
Ions such as calcium, chromium, manganese, iron, cobalt, nickel, zirconium, 41m, III, tR, barium, and aluminum are preferable, and salts of these metals such as hydrochloride, sulfate, nitrate, acetate, etc. An aqueous solution containing an appropriate concentration of acid is used as the treatment solution.

As a method for adsorbing metal ions and boric acid, it is preferable to immerse the film in a processing solution, but this is done after the dichroic dye has been adsorbed and oriented, that is, the dyeing solution containing the dichroic dye is used. The most preferable method is to dye the film with , and then stretch it in a substantially uniaxial direction.If the film is immersed in a treatment solution in a tensioned state after stretching, the subsequent heat treatment can be carried out while maintaining that tension. I can do it.

The heat treatment after adsorbing the metal ions and boric acid is performed with the film under tension at 90°C or higher, preferably at 100°C or higher.
At a temperature of 120°C for 1 to 120 minutes, preferably 5 to 4
It consists of heating for 0 minutes.

The amount of metal ions and boric acid impregnated in the polarizing film is 0.2111g to 2.0g per 1g of film as metal.
0 mg, in particular 1-5II 1 g, as boron per gram of fillem, 0.3 mg to 30 mg, especially 1-10 m
g is appropriate.

In the present invention, the film may be stretched not only in one direction but also slightly in another (perpendicular) direction in order to increase the strength. In this case, the stretching in the other axis direction may be performed simultaneously or after the stretching in the l-axis direction, and the stretching ratio is preferably 1/2 or less of the stretching ratio in the uniaxial direction.

[Action and effect]

The polarizing film obtained by the present invention has excellent optical properties as well as high heat resistance and moisture resistance, so it can be used in various fields such as various optical devices such as liquid crystal display devices, sunglasses, automobile windshields, and windows. can.

〔Example〕

The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

In the Examples and Comparative Examples, the transmittance was measured using a spectrophotometer (manufactured by Hitachi, Ltd., trade name: HITACHI330). Single plate transmittance, parallel transmittance (Ho: light transmittance when two films are stacked so that their molecular orientations are parallel to each other), orthogonal transmittance (H9°; two films, The light transmittance (light transmittance when superimposed so that the molecular orientations are perpendicular to each other) is the value at its maximum absorption wavelength in the case of a color polarizing film, and the value in the visible region of 400 to 700 nm in the case of a neutral color polarizing film. This is the average value for .

The degree of polarization was determined using the following formula.

Hue was measured using a color difference meter (manufactured by Tokyo Juishokusha, product name TC-1500M)
C). The meanings of parallel value and orthogonal position in hue measurement are the same as in the case of transmittance.

Example 1 A polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., trade name: Kuraray Vinylon #7500) was coated with Congo Red 0.
33g/l, Brilliant Blue 6B 1.87g/l and Direct Fast Yellow 50L 0.56g#! After dyeing for 15 minutes in an aqueous solution (staining solution) containing
Dry.

This film was stretched 4 times in the uniaxial direction at a temperature of 95 to 100°C, and while maintaining the tension, chromium nitrate nonahydrate 3
．． An aqueous solution containing 38 g/l and boric acid 6.64 g/l (
treatment solution) for 5 minutes.

Thereafter, while maintaining the tension state, it was washed with water, dried, and then heat-treated at 110° C. for 20 minutes.

This film contained 1.22 mg of boron and 1.10 μg of chromium per gram.

By laminating a 70 μm thick polycarbonate film on both sides of the obtained film using a urethane adhesive, a neutral color film having the performance shown in Table 1 was obtained.

In addition, after this film was exposed to an atmosphere at a temperature of 100°C for 100 hours (heat resistance test) and at a temperature of 80°C and a relative humidity of 8.
The performance after 100 hours of exposure to 0% atmosphere (humidity test) was as listed in Table 1.

Example 2 Chloranthine Fast Red 5B0.8 as staining solution
1g/l, Brilliant Blue 6B 1.85g/l and Chrysophenine 0.81g#! Example 1 except that an aqueous solution containing 3.30 g/l of zinc acetate trihydrate and 6.57 g/ffi of boric acid was used as the treatment solution.
It was carried out in the same manner as above, and on both sides of the obtained film (containing 1.30μ of boron and 1.15μ of zinc per Ig),
A polycarbonate film with a thickness of 70 μm was bonded together using a urethane adhesive.

The performance of this film was as listed in Table 1.

Examples 3 to 13 As a treatment solution, magnesium acetate, calcium acetate,
3 to 4 g/2 of manganese acetate, ferrous sulfate, cobalt chloride, zirconyl sulfate, copper sulfate (■), silver nitrate, stannic chloride, barium sulfate, or aluminum sulfate and 6 g/2 of boric acid.
Example 2 was carried out in the same manner as in Example 2 except that an aqueous solution containing ~7 g/l was used, and the ΔL of the obtained film was 46 or more in all cases.

Example 14 A blue polarizing film was obtained in the same manner as in Example 1 except that an aqueous solution containing 1.91 g/l of Direct Blue was used as the staining solution.

The single plate transmittance of this film at 600 nm is 35.
2%, the degree of polarization was 99.1%, and the film had the same heat and humidity resistance as the film obtained in Example 1.

Comparative Example 1 A commercially available neutral color polarizing film (polyvinyl alcohol film adsorbed and oriented with iodine and triacetyl cellulose laminated as a protective film) and this film were exposed to an atmosphere at a temperature of 100°C for 60 hours. The performance after (heat resistance test) was as shown in Table 1. still,
In this case, the film became severely discolored within 60 hours.

Further, when this film was exposed to an atmosphere at a temperature of 80° C. and a relative humidity of 80%, the color progressed and became substantially transparent within 40 hours, exhibiting no polarizing ability at all.

Comparative Example 2 The same procedure as in Example 1 was carried out except that an aqueous solution containing only 6.23 g/β of boric acid was used as the treatment solution.

The properties of the obtained film were as listed in Table 1.

Furthermore, when this film was exposed to an atmosphere at 100°C for 100 hours, the generation of bubbles was observed.

Comparative Example 3 The same procedure as in Example 2 was carried out except that the treatment with the treatment solution was not performed.

The performance of the obtained film was as shown in Table 1. When this film was exposed to an atmosphere at 100° C. for 100 hours, generation of bubbles was observed.

Comparative Example 4 A blue polarizing film was obtained in the same manner as Comparative Example 2, except that an aqueous solution containing 1.90 g/l of Direct Blue was used as the staining solution.

The single plate transmittance of this film at 600 nm is 27.
0%, and the degree of polarization was 98.0%.

When this film was exposed to an atmosphere at 100°C for 100 hours, peeling was observed, and when exposed to an atmosphere at a temperature of 80°C and relative humidity of 80%, no bubbles or peeling was observed. However, after 100 hours, the polarization power was 88.
It decreased to 0%.

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Claims (1)

[Claims] A polarizing film obtained by adsorbing a dichroic dye onto a polyvinyl alcohol film, oriented substantially in one direction, impregnating it with metal ions and boric acid, and then subjecting it to heat treatment under tension.