JPH0990124A - Reflection type polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a reflection type polarizing plate capable of being adhered to a liquid crystal cell without causing contamination of the reflection plate or other members of a liquid crystal display device or without causing adhesion defects such as blisters and peeling between members even in a severe environment of high temp. or high temp. and high humidity for use, and capable of being peeled off when the liquid crystal cell is regenerated, without damaging the function of the liquid crystal cell. SOLUTION: This reflection type polarizing plate consists of a polarizing plate having a cellulose-based protective film and a reflection metal foil with an acryl adhesive layer. The acryl adhesive is prepared by compounding a silane compd. having epoxy groups into an acryl copolymer which is produced by radical copolymn. of a (meth)acrylate component and 1-20wt.% tertiary amine having vinyl groups and does not contain a carboxylic acid (anhydride) component.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a reflective polarizing plate.

[0002]

2. Description of the Related Art With the spread of liquid crystal display devices, polarizing plates have a wide range of applications from small items such as watches and calculators to office automation equipment such as personal computers and word processors, liquid crystal televisions, in-vehicle navigation systems and portable information equipment. Shows. Of the above applications, especially for equipment used in environments where the temperature inside the vehicle is extremely high during a summer stop, such as outdoor use and in-vehicle navigation systems, durability that can withstand these severe usage environments , Reliability is required.

These polarizing plates generally have a structure in which both surfaces of a polyvinyl alcohol film having a polarizing property are covered with a protective layer such as a cellulose triacetate film, and the polarizing layer is provided on the protective layer. It is attached to the liquid crystal cell via the adhesive layer. As the pressure-sensitive adhesive, those mainly composed of an acrylic resin having excellent transparency are often used, but as described above, when it is used for a long period of time in a high temperature and high humidity environment, cellulose is used. The system film is decomposed and deteriorated, and the reflective metal foil in contact with the pressure-sensitive adhesive layer in the liquid crystal display device is corroded and deteriorated, and the pressure-sensitive adhesive layer itself also deteriorates and yellows to deteriorate or eliminate the display function of the liquid crystal display device. Cause problems such as.

The acrylic resin used in the pressure-sensitive adhesive layer is generally 15% by weight or less of a (meth) acrylic acid component, 85% by weight or more of a (meth) acrylic acid ester and a vinyl monomer component which can be polymerized with the (meth) acrylic acid ester. And has a composition of The (meth) acrylic acid component improves the adhesive force and cohesive force of the pressure-sensitive adhesive by forming a cross-linked structure in the acrylic resin by using a carboxyl group as a cross-linking point.

On the other hand, the carboxyl group such as (meth) acrylic acid contained in the pressure-sensitive adhesive is kept in constant contact with the easily hydrolyzed cellulose triacetate film which is a reinforcing material of the polarizing plate, and the above-mentioned is mentioned above. Under such a severe environment, and in the presence of water, the cellulose triacetate film is hydrolyzed, and the phenomenon that the display function of the liquid crystal display device is deteriorated or lost is well known. is there.

As an attempt to solve the above-mentioned problems, for example, Japanese Patent Laid-Open No. 59-111114 discloses that:
There has been proposed an acrylic pressure-sensitive adhesive that does not contain (meth) acrylic acid and that contains, as a main component, a copolymer of butyl acrylate, benzyl methacrylate, and 2-hydroxyethyl methacrylate. However, although the acrylic pressure-sensitive adhesive having the above composition has a function of suppressing hydrolysis of the cellulose triacetate film which is easily hydrolyzed, it is difficult to satisfy both the internal cohesive force and the pressure-sensitive adhesive force. When it is placed in a severe environment of high temperature and high humidity as described above, it causes problems such as displacement, foaming and peeling of the pressure-sensitive adhesive layer and cannot be used for applications requiring high reliability.

Further, in Japanese Patent Laid-Open No. 2-3481, the adhesive strength, cohesive strength and heat resistance are excellent, and it firmly adheres to an adherend such as a glass cell to hydrolyze a cellulose triacetate film which is a reinforcing material. As a pressure-sensitive adhesive having an action of suppressing methacrylic acid, an acrylic pressure-sensitive adhesive formed by radical copolymerization of a methacrylic acid ester, a carboxyl group-containing compound copolymerizable therewith and a tertiary amine having a vinyl group has been proposed. .

[0008] However, the acrylic pressure-sensitive adhesive exhibits excellent heat resistance in equipment such as an in-vehicle navigation system used in an environment where the temperature is extremely high as seen in a stopped vehicle in the summer, Although it can be used effectively, the adhesion progresses due to heating etc. performed to align the alignment of the liquid crystal, so when regenerating the liquid crystal cell, it is difficult to peel off the polarizing plate etc. from the liquid crystal cell, and sometimes the uneven load at the time of peeling Therefore, there is a problem in that the liquid crystal cells become misaligned and cannot be reused.

Further, Japanese Patent Laid-Open No. 4-223493 discloses a polarizing plate having good durability by using a specific pressure-sensitive adhesive in the cellulose-based protective film layer coated to protect the polarizing film. For obtaining, a polarizing plate having an adhesive layer is disclosed. JP-A-4-2234
As the above-mentioned specific (acrylic resin) pressure-sensitive adhesive disclosed in Japanese Patent Publication No. 93, 45 to 50 parts by weight of 2-ethylhexyl acrylate and 39 to 46 parts by weight of n-butyl acrylate as a main monomer component, and a small amount of hydroxy as a comonomer component. 0.1 to 0.2 parts by weight of ethyl methacrylate and 5 to 7 parts by weight of vinyl acetate, acrylic acid or methacrylic acid as a functional group-containing monomer component 3.9 to
100 parts by weight of acrylic resin consisting of 4.8 parts by weight,
15 to 18 parts by weight of a tackifier comprising pentaerythritol ester of disproportionated rosin or pentaerythritol ester of polymerized rosin and 0.5 to 1.5 of 3-glycidoxypropyltrimethoxysilane or 3-glycidoxytriethoxysilane. In addition, 75 parts by weight of an ethyl acetate solution of a trimethylolpropane (1 mole) adduct of tolylene diisocyanate (3 moles), 60% by weight of cyclohexanediisocyanate in ethyl acetate, and 60% by weight of isophorone diisocyanate in acetic acid. An adhesive containing 0.2 to 2.0 parts by weight of a cross-linking agent composed of an ethyl solution is used, and it is claimed that the use of a carboxyl group-containing monomer is particularly preferable among the above functional group-containing monomer components. .

However, the acrylic resin pressure-sensitive adhesive used in the polarizing plate disclosed in the above-mentioned Japanese Patent Laid-Open No. 4-223493 has a carboxyl group such as acrylic acid or methacrylic acid as the functional group-containing monomer component as described above. Since it contains the contained monomer component, as described above, by heating or the like for aligning the liquid crystal, adhesion is promoted, so that when the liquid crystal cell is regenerated, it is difficult to peel the polarizing plate or the like from the liquid crystal cell, There is a problem in that the distance between the liquid crystal cells becomes irregular due to an unequal load during peeling, and reuse becomes impossible.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object of the present invention is to provide a reflective plate and other liquid crystal displays even in severe operating environments of high temperature and high humidity. A polarizing plate is attached to the liquid crystal cell without soiling the members of the device or causing adhesion failure such as floating or peeling between the members, and the polarization of the liquid crystal cell is not impaired during reproduction of the liquid crystal cell. An object is to provide a pressure-sensitive adhesive sheet for a polarizing plate, which is capable of peeling a plate.

[0012]

According to a third aspect of the present invention, a (meth) acrylic acid ester component is mainly contained and a vinyl group is provided on one surface of a polarizing plate provided with a cellulose-based protective film.
Radical copolymerization of 1 to 20% by weight of primary amine,
(Anhydrous) Reflection, characterized in that a reflection metal foil is laminated through an acrylic pressure-sensitive adhesive layer obtained by blending an acrylic copolymer containing no carboxylic acid component with a silane compound having an epoxy group. The type polarizing plate is the gist of the invention.

The polarizing plate comprises a polarizing film laminated and covered with a cellulose-based protective layer. The polarizing film is not particularly limited, for example, polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, polyvinyl alcohol resin film such as saponified ethylene-vinyl acetate copolymer iodine, dichroic dyes, etc. The polarizing element can be produced by impregnating and adsorbing the polarizing element and stretching the film.

As the cellulose-based protective layer, cellulose triacetate and other cellulose-based transparent films having little optical anisotropy are used. When the above polarizing plate is used as a reflection type polarizing plate, the reflection plate laminated on the polarizing plate is a metal foil for reflection laminated on a base film such as a polyethylene terephthalate film with an adhesive or the like. To be

The above-mentioned (meth) acrylic acid ester is an acrylic acid ester or a methacrylic acid ester and is not particularly limited, but for example, ethyl (meth) acrylate, isopropyl (meth) acrylate, (meth ) N-Butyl acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n- (meth) acrylate
Octyl, isononyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate and other (meth) acrylic acid alkyl esters, benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and the like Examples thereof include (meth) acrylic acid-substituted alkyl esters.

The blending amount of the (meth) acrylic acid ester component is 50% by weight or more based on the total monomer components constituting the acrylic copolymer. Examples of the (meth) acrylic acid ester comonomer include vinyl acetate and styrene. The blending amount of the comonomer component of the (meth) acrylic acid ester is 30% by weight or less based on all the monomer components constituting the acrylic copolymer.

Although the tertiary amine having a vinyl group is not particularly limited, for example, (meth)
Examples thereof include dimethylaminomethyl acrylate, dimethylaminoethyl (meth) acrylate, and dimethylaminopropyl (meth) acrylamide.

The blending amount of the tertiary amine having a vinyl group is 1 to 20% by weight based on all the monomer components constituting the acrylic copolymer. When the blending amount of the tertiary amine having a vinyl group is less than 1% by weight, the action of suppressing the hydrolysis of cellulose ester such as cellulose triacetate constituting the protective layer is lowered, and the blending amount is 20%.
When the content is more than weight%, the pressure-sensitive adhesive layer is softened to reduce the adhesive force and the cohesive force, neither of which is preferable.

The silane compound having an epoxy group is not particularly limited, but methyltri (glycidyl) silane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- Examples thereof include glycidoxypropyltriethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and 3-glycidoxypropyltrimethoxysilane is particularly preferably used. The addition amount of the silane compound having an epoxy group is 0.01 to 10 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the acrylic copolymer. When the addition amount of the silane compound having an epoxy group is less than 0.01 parts by weight, foaming and peeling of the pressure-sensitive adhesive layer in a hot and humid environment cannot be suppressed, and the addition amount is 10 parts by weight. When it exceeds the amount, the adhesive property at high temperature is deteriorated.

When the (meth) acrylic acid ester component of the acrylic copolymer contains a monomer having a crosslinkable functional group such as 2-hydroxyethyl (meth) acrylate, the above acrylic copolymer is used. To 3% by weight or less of a curing agent, for example, a trimethylolpropane tolylene diisocyanate adduct, a trimethylolpropane hexamethylene diisocyanate adduct, etc. are added to adjust the pressure-sensitive adhesive. For example, at the time of coating and drying the pressure-sensitive adhesive layer,
The cohesive force of the pressure-sensitive adhesive layer can be adjusted by partially crosslinking the acrylic copolymer.

Since the reflective polarizing plate of the present invention is constructed as described above, even when used in a hot and humid environment, a cellulose ester component such as cellulose triacetate constituting the protective layer. Suppresses hydrolysis of the base material, corrodes and contaminates the surface of the reflection plate with the metal foil laminated on the base material, peels the polarizing plate due to deterioration of the protective layer, foams the adhesive layer, and causes deterioration. The function of the liquid crystal display device is not lost by coloring, and the range of use of the reflective polarizing plate can be expanded to a hot and humid environment which has been considered difficult in the past. Furthermore, even when heating is performed to align the liquid crystal, the adhesion of the pressure-sensitive adhesive hardly progresses, so that the polarizing plate can be peeled off without impairing the function of the liquid crystal cell when the liquid crystal cell is regenerated. Can be increased.

[0022]

Next, embodiments of the present invention will be described.

(Example 1) (Preparation of acrylic pressure-sensitive adhesive) 94 parts by weight of butyl acrylate and 5 parts by weight of dimethylaminoethyl acrylate were placed in a polymerization vessel equipped with a reflux tube, a thermometer and a nitrogen gas introducing tube.
-Hydroxyethyl methacrylate (1 part by weight), ethyl acetate (100 parts by weight) and benzoyl peroxide (0.05 parts by weight) were charged, and after purging with nitrogen gas in the vessel, the temperature was raised to 70 ° C to start the reaction, and after 3 hours, acetic acid was added. 0.003 parts by weight of benzoyl peroxide mixed with 50 parts by weight of ethyl is additionally added, and after 5 hours, 0.1 part by weight of benzoyl peroxide mixed with 100 parts by weight of ethyl acetate is added, and the reflux temperature of ethyl acetate is added. The temperature was raised to (about 77 ° C.) and the reaction was continued for 4 hours. After the reaction was completed, 200 parts by weight of ethyl acetate was added to obtain an acrylic copolymer solution. The polymerization rate of the above polymerization reaction is 9
It was 9.9%. Obtained acrylic copolymer solution 1
To 100 parts by weight, as shown in Table 1, 0.1 part by weight of a 75% by weight ethyl acetate solution of trimethylolpropane xylylene diisocyanate as a curing agent and 0.6 part by weight of 3-glycidoxypropyltrimethoxysilane were added, The mixture was uniformly mixed to prepare an acrylic pressure-sensitive adhesive.

170 g of a 38 μm thick polyester film obtained by subjecting the above acrylic adhesive to a silicone release treatment.
/ M ² and then heat-dried at 80 ° C. for 10 minutes to prepare an adhesive sheet. The pressure-sensitive adhesive sheet was pressed with a roller on the back surface of a polarizing plate having a reflection plate having an aluminum foil laminated on one surface of a polyethylene terephthalate film, to produce a reflective polarizing plate.

(Example 2) A reflection plate having an aluminum foil laminated on one surface of a polyethylene terephthalate film is attached to a polarizing plate with the pressure-sensitive adhesive sheet obtained in Example 1, and also on the opposite surface of the polarizing plate. The pressure-sensitive adhesive sheet obtained in Example 1 was processed in the same manner as in Example 1 to prepare a reflective polarizing plate.

(Example 3) An acrylic pressure-sensitive adhesive was prepared in the same manner as in Example 1 with the compounding composition shown in Table 1. A reflective polarizing plate was produced in the same manner as in Example 1 using the obtained acrylic pressure-sensitive adhesive.

(Comparative Examples 1 to 3) Acrylic pressure-sensitive adhesives were prepared in the same manner as in Example 1 with the composition shown in Table 1.
A reflective polarizing plate was produced in the same manner as in Example 1 using the obtained acrylic pressure-sensitive adhesive. Comparative Example 1 is an acrylic adhesive that is very commonly used, and Comparative Example 2 is JP-A-5
The acrylic pressure-sensitive adhesive described in JP-A No. 9-111114 and Comparative Example 3 are reflective polarizing plates using the acrylic pressure-sensitive adhesive described in JP-A-4-223403.

[0028]

[Table 1]

In Table 1, some compound substance names are abbreviated, and the respective abbreviations are as follows. 1.2-EHA: 2-ethylhexyl acrylate 2. DMAEA: dimethylaminoethyl acrylate 3.2-HEMA: 2-hydroxyethyl methacrylate 4. AIBN: Azobisisobutyronitrile

(Preparation of Test Pieces) In order to evaluate the performance of the reflective polarizing plates obtained in the above Examples and Comparative Examples, the reflective polarizing plates were placed on a glass plate for a liquid crystal cell by contacting their adhesive sheet surfaces. Place it on the table, reciprocate the 1kg roller once, and
After sticking under the sticking conditions of 50 ° C, 5 atmospheres, 20 minutes,
A test piece was prepared by heating at 80 ° C. for 20 minutes to align the liquid crystal, allowing to cool, and conditioning at 23 ° C. and 65% RH for 1 hour.

With respect to the obtained test piece, a heat resistance test,
The humidity resistance test and the 180 ° peeling test with respect to the glass plate were tested by the following methods. The test results are also shown in Table 3. Heat resistance test: The above test piece was heated in a constant temperature bath at 100 ° C. × 240 hours and 100 ° C. × 500 hours, cooled, and then visually observed with a focus on the properties and adhesion state of the reflective polarizing plate on the glass plate for a liquid crystal cell. The evaluation was made by the five-point method shown in Table 2 (provided that the criteria intended by the present invention have not been cleared except for those evaluated by ◯).

Moisture resistance test: For the above test piece, in the same manner as the heat resistance test in the preceding paragraph, 80 ° C. × 90% RH × 240
After heating in a constant temperature bath for 80 hours and 80 ° C. × 90% RH × 500 hours and cooling, the properties and adhesion state of the reflective polarizing plate on the glass plate for liquid crystal cell were visually observed, and shown in Table 2. In addition, the evaluation was carried out by the evaluation points by the 5-point method (however, the criteria intended in the present invention have not been cleared except for those evaluated by ◯).

180 ° peel test against glass plate: width 25 m
A 180 ° peeling test was performed on the above test piece of m to evaluate the adhesive strength to the glass plate.

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

Since the reflective polarizing plate of the present invention is constructed as described above, cellulose triacetate constituting the protective layer even when used in a hot and humid environment. Suppresses the hydrolysis of cellulose ester components such as, and corrodes the surface of the reflection plate with a metal foil laminated on the substrate to stain it, peels the polarizing plate due to deterioration of the protective layer, and foams the adhesive layer. Therefore, the function of the liquid crystal display device is not lost by coloring due to deterioration or deterioration, and the range of use of the reflective polarizing plate can be expanded to a hot and humid environment, which has been conventionally difficult. Furthermore, since the adhesion progress of the adhesive hardly occurs due to the heating performed for aligning the alignment of the liquid crystal, the polarizing plate can be peeled off without impairing the function of the liquid crystal cell at the time of reproducing the liquid crystal cell, thus improving the use efficiency of the liquid crystal cell. be able to.

Claims (1)

[Claims] 1. A surface of a polarizing plate provided with a cellulose-based protective film is radically copolymerized with 1 to 20% by weight of a tertiary amine having a vinyl group, which is mainly composed of a (meth) acrylic acid ester component. And a metal foil for reflection is laminated via an acrylic pressure-sensitive adhesive layer obtained by blending a silane compound having an epoxy group with an acrylic copolymer containing no (anhydrous) carboxylic acid component. Reflective polarizing plate.