JPH11218611A - Dye system polarizing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing film of a neutral color having characteristics of excellent polarization performance, excellent moisture resistance and heat resistance. SOLUTION: This dye system polarizing film contains at least one water-soluble dye expressed by formula (1) (where A denotes a benzene ring which may have a methyl group and R denotes an amino group, methyl amino group, ethyl amino group or phenyl amino group, respectively) or the copper complex salt dye thereof and at least one or above other org. dye having an absorption characteristic in a wavelength region different from the absorption wavelength region of the dye.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dye-based polarizing film.

[0002]

2. Description of the Related Art A polarizing plate having a light transmitting / shielding function is a fundamental component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The field of application of this LCD is wide ranging from small devices such as calculators and watches in the early days to notebook computers, word processors, liquid crystal projectors, liquid crystal televisions, car navigation systems and indoor and outdoor measuring devices, and the operating conditions are low to high temperatures. Since it is used in a wide range of conditions from low humidity to high humidity, a polarizing plate having high polarization performance and excellent durability has been demanded.

At present, a polarizing film is a polarizing film such as a stretch-oriented film of polyvinyl alcohol or a derivative thereof, or a polyene film which is oriented by generating polyene by dehydrochlorination of a polyvinyl chloride film or dehydration of a polyvinyl alcohol film. It is manufactured by adding iodine or a dichroic dye as a polarizing element to a substrate. Of these, the iodine-based polarizing film using iodine as the polarizing element has excellent initial polarization performance, but is weak against water and heat, and has durability when used for a long time at high temperature and high humidity. There is a problem. In order to improve durability, a method of treating with an aqueous solution containing formalin or boric acid or a method of using a polymer film having low moisture permeability as a protective film has been considered, but it cannot be said that it is sufficient. On the other hand, a dye-based polarizing film using a dichroic dye as a polarizing element has better moisture resistance and heat resistance than an iodine-based polarizing film, but generally has insufficient initial polarization performance.

Further, in a neutral color polarizing film obtained by adsorbing and orienting several kinds of dichroic dyes on a polymer film, a state in which two polarizing films are overlapped so that their orientation directions are orthogonal to each other ( In the visible light range, especially 400-700n
If light leakage (color leakage) of a specific wavelength in the wavelength region of m occurs, the hue of the liquid crystal display may change in a dark state when the polarizing film is mounted on the liquid crystal panel. Therefore, when a polarizing film is mounted on a liquid crystal display device, in order to prevent discoloration of the liquid crystal display due to color leakage of a specific wavelength in a dark state, several types of dichroic dyes are adsorbed on the polymer film.
In the neutral color polarizing film that is oriented, visible light region,
In particular, the orthogonal position transmittance (orthogonal transmittance) in the wavelength region of 400 to 700 nm must be uniformly reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-performance neutral-color (gray) polarizing film having excellent polarization performance, moisture resistance and heat resistance.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, have found that a polarizing film having a specific dye has excellent polarizing performance, moisture resistance and heat resistance. Further, by having a specific selected dye for making a polarizing film having a neutral color together with such a specific dye, it is excellent in polarization performance and durability and color leakage in the visible light region. And completed the present invention.

That is, the present invention provides (1) the following formula (1) in the form of a free acid:

[0008]

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Wherein A represents a benzene ring which may have a methyl group, and R represents an amino group, a methylamino group, an ethylamino group or a phenylamino group, respectively. At least one copper complex dye
A dye-based polarizing film comprising: at least one species; and at least one other organic dye having absorption characteristics in a wavelength region different from the absorption wavelength region of the dye, (2) the polarizing film is polyvinyl alcohol or a derivative thereof. The polarizing film according to (1), which is a film comprising:

A polarizing film having at least one water-soluble dye represented by the above formula (1) or a copper complex salt dye thereof is excellent in polarization performance and excellent in moisture resistance and heat resistance. Further, the polarizing film having the water-soluble dye represented by the above formula (1) or its copper complex dye contains another organic dye, so that the polarizing film is excellent in polarization performance and also excellent in moisture resistance and heat resistance. It is intended to provide a neutral color polarizing film having the same.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The water-soluble dye represented by the formula (1) can be prepared by a known diazotization / coupling method according to a conventional azo dye production method as described in JP-A-3-12606. Can be easily manufactured. Among the dyes of the formula (1), a dye represented by the following formula (2) is mentioned as a particularly preferred example.

[0012]

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The water-soluble dye represented by the formula (1) or the other organic dye used in combination with at least one of the copper complex salt dyes is different from the absorption wavelength region of the dye of the formula (1) or the copper complex salt dye. Any material having absorption characteristics in the wavelength region and high dichroism may be used. Specifically, for example, C.I. Eye. direct. Yellow 12, sea. Eye. direct. Yellow 28, sea. Eye. direct. Yellow 44, sea. Eye. direct. Yellow 142, sea. Eye. direct. Orange 6,
C. Eye. direct. Orange 26, sea. Eye.
direct. Orange 39, sea. Eye. direct.
Orange 107, sea. Eye. direct. Red 2,
C. Eye. direct. Red 31, Sea. Eye. direct. Red 79, Sea. Eye. direct. Red 81, Sea. Eye. direct. Red 247, Sea. Eye. direct. Green 59, sea. Eye. direct. Green 85, a dye described in JP-A-59-145255, and JP-A-60-15675.
No. 9 and the like, and these dyes are used as a free acid or a salt of an alkali metal salt, an ammonium salt, or an amine.

As a more preferred compounding system, a dye-based polarizing film containing at least one dye represented by the above formula (1) and further containing at least one organic dye of orange, red and green is exemplified. Although the mixing ratio is not particularly limited, generally, the total of at least one of the organic dyes is 0.1 to 1 based on the weight of the dye represented by the formula (1).
Preferably, it is used in the range of 0 parts by weight. The polarizing film thus configured has a neutral color, and is in a visible light region, particularly 400 to
No color leakage at the orthogonal position in the wavelength region of 700 nm,
It has excellent polarization performance and does not cause discoloration or deterioration in polarization performance even in high temperature and high humidity conditions.

As the polymer film, for example, polyvinyl alcohol or a derivative thereof, and either of them may be used as an olefin such as ethylene or propylene, or an unsaturated carboxylic acid such as crotonic acid, acrylic acid, methacrylic acid or maleic acid. And those made of EVA (ethylene / vinyl acetate) resin, saponified EVA resin, nylon resin, polyester resin and the like. Above all, a film made of polyvinyl alcohol or a derivative thereof is suitably used from the viewpoint of dye adsorption and orientation.

In order to incorporate a dichroic dye into such a polymer film, a method of dyeing the polymer film is usually employed. Staining can be performed, for example, as follows. First, a dichroic dye is dissolved in water to adjust a dye bath. The dye concentration in the dye bath is not particularly limited, but is usually selected from the range of about 0.001 to 10% by weight. If necessary, a dyeing aid may be used. For example, it is preferable to use sodium sulfate in a concentration of about 1 to 10% by weight. The polymer film is immersed in the dyeing bath adjusted in this way to perform dyeing. The dyeing temperature is preferably 40
~ 80 ° C.

The dichroic dye is oriented by stretching a polymer film. As a method of stretching,
For example, any known method such as a wet method and a dry method may be used. Stretching of the polymer film may be performed before dyeing. The polymer film containing and orienting the dichroic dye is optionally subjected to post-treatment such as boric acid treatment by a known method. Such a post-treatment is performed for the purpose of improving the light transmittance and the degree of polarization of the polarizing film. The conditions of the boric acid treatment vary depending on the type of the polymer film to be used and the type of the dye to be used. Generally, the boric acid concentration of the aqueous boric acid solution is in the range of 1 to 15% by weight, preferably 3 to 10% by weight. , Treatment at 30-80 ° C, preferably 40 ° C
Performed in a temperature range of ~ 75 ° C.

Further, if necessary, a fix treatment may be performed together with an aqueous solution containing a cationic polymer compound. The dye-based polarizing film thus obtained can be used as a polarizing plate by laminating a protective film having excellent optical transparency and mechanical strength on one or both surfaces thereof. The material for forming the protective film may be a conventionally used material, for example, a cellulose acetate film, an acrylic film, or a fluorine film such as an ethylene tetrafluoride / propylene hexafluoride copolymer. And a film made of polyester resin, polyolefin resin or polyamide resin.

As described above, by using the dye represented by the formula (1) in combination with the above-mentioned other organic dye, excellent moisture resistance and heat resistance are obtained, and light leakage at the orthogonal position in the visible light region is achieved. A polarizing film with a small neutral color can be obtained.

[0020]

The present invention will be described in more detail with reference to the following examples, which are illustrative only and do not limit the present invention in any way. The percentages and parts in the examples are
Unless otherwise specified, it is based on weight.

Example 1 The sodium salt of the dye represented by the above formula (2) was 0.06
%,C. Eye. direct. Orange 39 to 0.04
%,C. Eye. direct. Red 81 to 0.02
%, The concentration of the sodium salt of the dye represented by the following formula (3) disclosed in JP-A-60-156759, Example 38 being 0.04% and that of sodium sulfate being 0.3%: 45 ° C. Was immersed in a 75 μm thick polyvinyl alcohol for 4 minutes. This film was stretched 5 times in a 3% aqueous solution of boric acid at 50 ° C., washed with water while keeping the tension, and dried to obtain a neutral color polarizing film. The obtained polarizing film had a polarizing ratio of 99.9% at a single-plate transmittance of 40%, and did not show discoloration for a long time even in a high temperature and high humidity state.

[0022]

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Example 2 The sodium salt of the dye represented by the above formula (2) was
%,C. Eye. direct. Orange 39 to 0.04
%,C. Eye. direct. Red 81 to 0.04
45.degree. C. at a concentration of 0.03% for the sodium salt of the dye represented by the following formula (4) and 0.3% for sodium sulfate, disclosed in JP-A-60-156759 and Example 23. Was immersed in a 75 μm thick polyvinyl alcohol for 4 minutes. This film was stretched 5 times in a 3% aqueous solution of boric acid at 50 ° C., washed with water while keeping the tension, and dried to obtain a neutral color polarizing film. The obtained polarizing film had a polarizing ratio of 99.9% at a single-plate transmittance of 40%, and did not show discoloration for a long time even in a high temperature and high humidity state.

[0024]

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Example 3 0.04% of the sodium salt of the dye represented by the formula (2)
C. Eye. direct. 0.03% of orange 39,
C. Eye. direct. 0.04% of Red 81, 0.04% of sodium salt of dye represented by the following formula (5) and 0.3% of Glauber's salt disclosed in Example 5 of JP-A-3-12606. The polyvinyl alcohol having a thickness of 75 μm was immersed in an aqueous solution at 45 ° C. with a concentration of 4 minutes for 4 minutes. This film is placed in a 3% aqueous solution of boric acid for 50 minutes.
The film was stretched 5 times at ℃, washed with water while keeping the tension, and dried to obtain a neutral color polarizing film. The obtained polarizing film had a polarizing factor of 99.5% at a single-plate transmittance of 40%, and did not show discoloration for a long time even in a high temperature and high humidity state.

[0026]

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Example 4 0.04% of a sodium salt of a dye represented by the following formula (6) disclosed in JP-A-3-12606 and Example 2 was prepared. Eye. direct. Orange 39
0.04%, C.I. Eye. direct. 0.03% of Red 81, 0.04% of the sodium salt of the dye represented by the formula (4) and 0.3% of sodium sulfate disclosed in Example 23 of JP-A-60-156759. %
The polyvinyl alcohol having a thickness of 75 μm was immersed in an aqueous solution at 45 ° C. with a concentration of 4 minutes for 4 minutes. 3% of this film
The film was stretched 5 times at 50 ° C. in a boric acid aqueous solution, washed with water while keeping the tension state, and dried to obtain a neutral color polarizing film. The polarizing film obtained had a polarizing factor of 99.% at a single-plate transmittance of 40%.
3%, and did not show discoloration over a long period of time even under high temperature and high humidity conditions.

[0028]

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Comparative Example 1 Instead of the dye represented by the formula (2) used in Example 1, it is represented by the following formula (7) disclosed in Example 1 of JP-A-5-295281. A neutral-color polarizing film was obtained in the same manner as in Example 1 except that a trisazo dye was used. The obtained polarizing film had a polarizing ratio of 98.7% at a single plate transmittance of 40%, which was inferior to the neutral color polarizing film of the present invention.

[0030]

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[0031]

The dye-based polarizing film of the present invention is comparable to a polarizing film using iodine by containing a specific dye and a specific selected dye for forming a polarizing film having a neutral color. High polarization performance and excellent durability. Further, color leakage in the visible light region can be reduced. That is, this polarizing film is a neutral-color polarizing film obtained by adsorbing and orienting two or more types of dichroic dyes on a polymer film, and is in a visible light region, particularly 400 to 700 nm.
Is a high-performance polarizing film having excellent polarization performance, moisture resistance, and heat resistance without color leakage at the orthogonal position in the wavelength region of For this reason, it is suitable for various liquid crystal displays, especially in-vehicle applications requiring high polarization performance and durability, and display applications of industrial instruments used in various environments.

Claims (2)

[Claims] (1) The following formula (1) in the form of a free acid: (Wherein A represents a benzene ring which may have a methyl group,
R represents an amino group, a methylamino group, an ethylamino group or a phenylamino group, respectively. Wherein the dye has at least one water-soluble dye or copper complex salt dye represented by the formula (1) and at least one other organic dye having an absorption characteristic in a wavelength region different from the absorption wavelength region of the dye. System polarizing film. 2. The polarizing film according to claim 1, wherein the polarizing film is a film made of polyvinyl alcohol or a derivative thereof.