JP3511111B2 - Polarizing plate for liquid crystal display device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate for a liquid crystal display device used in a liquid crystal display device for the purpose of displaying in the field of optoelectronics by utilizing the response of liquid crystal molecules by an electric field.

[0002]

2. Description of the Related Art Conventionally, the alignment layers of two substrates having a transparent electrode and an alignment layer formed on one surface thereof are opposed to each other, and a liquid crystal layer is interposed therebetween, and A liquid crystal display (LCD) having a polarizing plate bonded to the other surface of the substrate is widely used. In this case, as the polarizing plate, as shown in FIG. 1, a polarizing plate having a structure in which protective films 2 and 2 are adhered to both surfaces of the polarizing film 1 with adhesives 3 is often used. A technique of using a pressure-sensitive adhesive as an adhesive for bonding a film and its protective film (JP-A-57-195208, JP-A-3-12471) and a liquid containing a vinyl monomer or an oligomer as a main component Techniques used (Japanese Patent Laid-Open No. 58-171007, Nitto Denko Corporation) are known.

However, when a pressure sensitive adhesive (adhesive) is used, the durability of the polarizing plate such as heat resistance and moisture heat resistance is extremely low,
Moreover, there is a problem that the adhesive strength is low.

On the other hand, when a liquid material containing a vinyl monomer or an oligomer as a main component is used, the vinyl monomer or the oligomer swells the polarizing film layer or its protective film, which is a constituent element of the polarizing plate, and optically distorts. Since the vinyl monomer is acrylic, the cured film (adhesive layer) is hard, brittle, and easily cracked. Liquid crystal display devices used for mobile terminals are required to have impact resistance (when dropped), which is not suitable for this application, and its application is extremely limited. Adhesion with polarizing film or protective film is extremely limited. Low, since the adhesive is a liquid, there is a problem that it has no function of improving the polarization degree of the polarizing film.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a polarizing plate for a liquid crystal display device, which is excellent in adhesion and various durability and has high reliability.

[0006]

Means and Actions for Solving the Problems The present inventors have
As a result of earnest studies to achieve the above object, a photocurable adhesive containing ethylene, vinyl acetate and a copolymer of acrylate and / or methacrylate monomers as a main component for adhesion between the polarizing film and the protective film. When used, it firmly adheres the polarizing film and the protective layer, is excellent in various durability such as heat resistance, moisture heat resistance, cold heat resistance cycle, and adheres without affecting the optical function of the polarizing film and the protective layer. It has the function of improving the polarization degree of the polarizing film, and because the cured film is flexible and rich in elasticity, it has the excellent effect of being resistant to external impact and deformation, and is highly reliable. It was found that a polarizing plate having a property is obtained,
The present invention has been completed.

Therefore, according to the present invention, in a polarizing plate which is obtained by adhering and covering a protective film on a polarizing film and laminated on a liquid crystal cell surface substrate of a liquid crystal display device, the polarizing film and the protective film are made of ethylene or vinyl acetate. Also provided is a polarizing plate for a liquid crystal display device, wherein the polarizing plate is bonded by a photocurable adhesive containing a copolymer of an acrylate-based and / or a methacrylate-based monomer as a main component.

The present invention will be described in more detail below. The polarizing plate of the present invention is, for example, a polarizing plate having a structure as shown in FIG. 1 described above, which is used as an adhesive for bonding the polarizing film 1 and the protective film 2 to each other. It is characterized in that a photo-curable adhesive containing a copolymer of ethylene, vinyl acetate and an acrylate-based and / or methacrylate-based monomer as a main component is used. Here, the content of vinyl acetate units in this copolymer is preferably 5 to 50% by weight, and more preferably 14 to 45% by weight. When the content of the vinyl acetate unit is lower than 5% by weight, the transparency and optical uniformity of the photocured adhesive layer are not sufficient, while the content of 50% by weight is high.
If it exceeds, transparency and optical uniformity will be good, but the strength and durability of the adhesive layer will tend to be significantly reduced.

Examples of the acrylate-based monomer and the methacrylate-based monomer include acrylic acid, methacrylic acid and their esters. Specifically, (meth) acrylate, ethyl (meth) acrylate and the like ( In addition to (meth) acrylic acid lower alkyl ester, glycidyl (meth) acrylic acid and the like are exemplified. These may be used alone or in combination of two or more, but the content of the acrylate-based and methacrylate-based units in the copolymer is 0.01 to 10% by weight, particularly It is preferably 0.05 to 5% by weight. If this content exceeds 10% by weight, workability may decrease.

A photosensitizer is blended for curing the photocurable adhesive according to the present invention. Examples of usable photosensitizers include benzoin, benzophenone, benzoin methyl ether, benzoin ethyl ether, Benzoin isopropyl ether, benzoin isobutyl ether, dibenzyl, 5-nitroacenaphthene, hexachlorocyclopentadiene, paranitrodiphenyl, paranitroaniline, 2,4,6-trinitroaniline, 1,
Examples thereof include 2-benzanthraquinone, 3-methyl-1,3-diaza-1,9-benzanthrone, and these may be used alone or in combination of two or more.

The addition amount of the photosensitizer in the present invention is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the above copolymer.

A silane coupling agent can be added to the adhesive of the present invention as an adhesion promoter. As this silane coupling agent, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane,
γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl)
There are ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, etc. , These 1 type can be used individually or in mixture of 2 or more types. The addition amount of these silane coupling agents is the same as that of the copolymer 1 above.
Usually 0.01 to 5 parts by weight is sufficient with respect to 00 parts by weight.

Furthermore, in order to improve or adjust the physical properties (mechanical strength, optical properties, adhesiveness, heat resistance, moist heat resistance, weather resistance, crosslinking rate) and the like of the photocurable adhesive of the present invention, the present invention In, a compound containing an acryloxy group, a methacryloxy group or an allyl group can be added.

Most commonly used compounds for this purpose are acrylic acid or methacrylic acid derivatives such as their esters and amides. In this case, as the ester residue, in addition to alkyl groups such as methyl, ethyl, dodecyl, stearyl and lauryl, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2
-Hydroethyl group, 3-hydroxypropyl group, 3-chloro-2-hydroxypropyl group and the like. Further, esters of acrylic acid or methacrylic acid with polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, pentaerythritol and the like are also used. Acrylamide is a typical amide. Examples of the allyl group-containing compound include triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, diallyl maleate, and the like. It is used by adding 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight to 100 parts by weight of the combined product. If it is less than 0.1 part by weight, the improving effect of improving the mechanical strength may be deteriorated, and if it exceeds 50 parts by weight, workability and film-forming property during preparation of the adhesive may be deteriorated.

A hydrocarbon resin may be added to the adhesive of the present invention for the purpose of improving workability and workability such as bonding. In this case, the added hydrocarbon resin may be a natural resin type or a synthetic resin type. As the natural resin type, rosin, rosin derivative and terpene type resin are preferably used. For rosin, gum resins, tall oil resins and wood resins can be used. As the rosin derivative, rosin is hydrogenated, heterogenized, polymerized,
Esterified or metal chloride can be used.
As the terpene-based resin, a terpene-based resin such as α-pinene and β-pinene, and a terpene-phenolic resin can be used. Also, as other natural resins, dammar,
It does not matter if you use corbal or shellac. On the other hand, petroleum-based resins, phenol-based resins, and xylene-based resins are preferably used in the synthetic resin system. In petroleum resin, aliphatic petroleum resin, aromatic petroleum resin, alicyclic petroleum resin, copolymer petroleum resin, hydrogenated petroleum resin, pure monomer petroleum resin,
A coumarone indene resin can be used. As the phenol resin, an alkylphenol resin or a modified phenol resin can be used. As the xylene-based resin, a xylene resin or a modified xylene resin can be used.

The amount of the above-mentioned hydrocarbon resin added is appropriately selected, but it is preferably 1 to 200 parts by weight, more preferably 5 to 150 parts by weight, based on 100 parts by weight of the copolymer.

In addition to the above additives, the photocurable adhesive of the present invention may contain a small amount of an ultraviolet absorber, an antiaging agent, a dye, a processing aid and the like. In addition, in some cases, a small amount of additives such as silica gel, calcium carbonate, and fine particles of silicon copolymer may be included.

In the photocurable adhesive of the present invention, the above copolymer and the above additives are uniformly mixed and kneaded by an extruder, a roll or the like, and then calender, roll, T-die extrusion, inflation or the like. It can be used by forming a film into a predetermined shape by a film forming method. In film formation, embossing may be performed in order to prevent blocking and facilitate deaeration during pressure bonding with a polarizing film or a protective film. Further, the above copolymer and the above additives are uniformly dissolved in a solvent that does not affect the protective film or the polarizing film, and can be used as a solution-type adhesive, which is evenly applied to the surface of the film. After the temporary pressure bonding, the adhesive can be cured.

The polarizing film used for the polarizing plate of the present invention is not limited at all, and iodine and / or dichroic dyes are adsorbed and aligned on a hydrophilic polymer containing a hydroxy group such as polyvinyl alcohol and saponified EVA. A stretched general polarizing film is used. The protective film is not limited at all, and commercially available cellulose-based, polyester-based, polycarbonate-based films and the like are preferably used.

The photo-curable adhesive may be cured by irradiating the laminated body with ultraviolet rays using an ordinary mercury lamp or the like. Further, in order to accelerate the curing, the laminate may be heated in advance to about 40 to 120 ° C. and then irradiated with ultraviolet rays.

In this case, first, the adhesive of the present invention is interposed between the polarizing film and the protective film, and 50 to 120
0.01 to 20 kg / c at 70 ° C, especially 70 to 100 ° C
m ^2, especially 2 at a pressure of 0.1 to 10 / cm ²
It is recommended to carry out photo-curing after heating and pressing for -20 minutes, especially 5-10 minutes.

[0022]

EFFECT OF THE INVENTION In the polarizing plate according to the present invention, the photocurable adhesive layer is rich in flexibility, elasticity and impact resistance, and has a high adhesive force, so that the strength and reliability of the polarizing plate as a whole are significantly improved. It is a thing. Further, since the processing can be carried out at a low temperature, the bonding processing can be carried out without adversely affecting the polarizing film layer having a low heat resistance limit. Moreover, unlike a conventional liquid adhesive containing a large amount of an acrylic monomer, it does not swell the surface of a polarizing film or a protective film and does not damage it, so that the function as a polarizing plate is reduced at all. It is possible to perform the bonding without the need. Furthermore, in terms of durability such as heat resistance, moisture heat resistance, and cold heat resistance cycle, the above-mentioned copolymer crosslinked by photocuring is rich in heat resistance and heat cycle resistance, and in particular, it is possible to prevent entry of moisture and humidity. , The deterioration of the polarizing film, which is sensitive to moisture, can be sufficiently prevented. This is not observed in the conventional liquid adhesive containing an acrylic monomer or oligomer as a main component and is a particularly preferable point. Further, when the photocurable adhesive of the present invention is formed into a film by using a T-die, a calender roll or the like, the molecular axes of the copolymer tend to be evenly aligned in the film forming direction. In addition to the polarization degree of the polarizing film, it also has the effect of improving the polarization degree of the entire polarizing plate.

[0023]

EXAMPLES Hereinafter, the present invention will be specifically described by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following examples, parts indicate parts by weight.

[0024]

[0025]

[Example] Ethylene-vinyl acetate-glycidyl methacrylate copolymer (Bond First 2B, manufactured by Sumitomo Chemical Co., Ltd .: vinyl acetate content 5%, glycidyl methacrylate content 12)
%) 100 parts, 5 parts of 1,2-benzanthraquinone and 5 parts of γ-methacryloxypropylmethoxysilane.
Parts, 30 parts of alicyclic hydrocarbon resin Alcon M-100 (manufactured by Arakawa Chemical Industry Co., Ltd.) and 5 parts of neopentyl glycol diacrylate are kneaded with a roll mill set at 70 ° C.,
80 ° C x 15 minutes, 50 kg / cm ² by electrothermal press
Was applied to produce an adhesive film A having a thickness of 100 μm. Then, as shown in FIG. 1, a polarizing film and a protective film made of a triacetate film having a thickness of 50 μm were superposed on each other via the adhesive film A. This laminated body is set between electrothermal presses, and at 90 ° C. for 15 minutes,
Heat and pressurize at a pressure of 0.5 kg / cm ² , then 4 k
The high pressure mercury lamp was irradiated with ultraviolet rays for 30 minutes on each side for a total of 1 minute to obtain a polarizing plate A.

Comparative Example 100 parts of ethyl methacrylate and 10 parts of glycidyl methacrylate were added to one side of the triacetyl cellulose protective film.
Apply a mixed liquid material consisting of 1 part of azobisisobutyrylonitrile, stick it on both sides of the polarizing film and press-bond it,
Leave it in the oven for 60 minutes while keeping it at 90 ° C,
A polarizing plate B was obtained.

With respect to the polarizing plates of Examples and Comparative Examples, heat resistance and moist heat resistance tests were carried out to examine whether or not there was abnormal appearance such as peeling, misalignment or foaming. The results are summarized in Table 1. In addition, if the above-mentioned abnormality is not recognized, pass,
If not, it was judged as a failure.

[0029]

[Table 1] (Test size: 150 mm square) * 1: 90 ° C x 1000 hours * 2: 70 ° C, 95% RH x 1000 hours

The polarizing plate A of the examples was a flat laminate having no distortion or unevenness in any visual inspection after production. On the other hand, in the polarizing plate B of the comparative example, there is a problem that an optical fluctuation occurs in the boundary layer of the bonding surface due to dissolution or swelling on the surface of the constituent member, which is considered to be caused by the acrylic monomer, and thus the transmitted image looks distorted. Was observed.

Further, as is clear from the results in Table 1, the polarizing plate according to the present invention has high adhesiveness to the constituent members and high durability due to the crosslinked structure formed in the ethylene-vinyl acetate- (meth) acrylate copolymer. As a result, it was found that no abnormalities were found in both the heat resistance test and the moisture heat resistance test, and that it has high reliability in practical use. However, in the case of the comparative example, a shift of about 0.5 to 1.0 mm was observed between the polarizing film and the protective layer in both tests, and a peeling of adhesion of about 5 mm from the edge portion was observed in the moisture and heat resistance test.

From the above, according to the present invention, it is possible to provide a highly reliable polarizing plate having excellent adhesion and various durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a polarizing plate.

[Explanation of symbols]

1 Polarizing film 2 protective film 3 adhesive 4 Polarizer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09J 123/08 C09J 123/08 131/04 131/04 G02B 5/30 G02B 5/30 G02F 1/1335 510 G02F 1/1335 510 (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C09J 1/00-201/10 G02B 5/30 G02F 1/1335

Claims (3)

(57) [Claims] 1. A polarizing plate comprising a polarizing film and a protective film adhered and coated thereon and laminated on a liquid crystal cell surface substrate of a liquid crystal display device, wherein the polarizing film and the protective film are made of ethylene, vinyl acetate or acrylate. And / or a polarizing plate for a liquid crystal display device, which is adhered with a photo-curable adhesive containing a copolymer of a methacrylate-based monomer as a main component, wherein the ethylene, vinyl acetate and acrylate-based and / or
Alternatively, a photo-curable adhesive containing a copolymer of a methacrylate-based monomer as a main component is added to 100 parts by weight of the copolymer,
0.1 to 10 parts by weight of a photosensitizer, 0.01 to 5 parts by weight of a silane coupling agent, 0.1 to at least one of an acryloxy group-containing compound, a methacryloxy group-containing compound and an allyl group-containing compound. 50 parts by weight, 1 to 200 parts by weight of a hydrocarbon resin are added, the content of vinyl acetate units in the copolymer is 5 to 50% by weight, and the content of acrylate-based and / or methacrylate-based units is 0. .0
A polarizing plate for a liquid crystal display device, which is 1 to 10% by weight. 2. An adhesive film in which the photo-curable adhesive containing the ethylene, vinyl acetate and a copolymer of acrylate and / or methacrylate monomers as a main component is formed by using a T-die or a calendar roll. The polarizing plate for a liquid crystal display device according to claim 1, which is used as. 3. A polarizing plate comprising a polarizing film and a protective film adhered and coated thereon and laminated on a liquid crystal cell surface substrate of a liquid crystal display device, wherein the polarizing film and the protective film are made of ethylene, vinyl acetate or acrylate. And / or a method for producing a polarizing plate for a liquid crystal display, which is adhered with a photocurable adhesive containing a copolymer of a methacrylate monomer as a main component, wherein
Alternatively, a photo-curable adhesive containing a copolymer of a methacrylate-based monomer as a main component is added to 100 parts by weight of the copolymer,
0.1 to 10 parts by weight of a photosensitizer, 0.01 to 5 parts by weight of a silane coupling agent, 0.1 to at least one of an acryloxy group-containing compound, a methacryloxy group-containing compound and an allyl group-containing compound. 50 parts by weight, 1 to 200 parts by weight of a hydrocarbon resin are added, the content of vinyl acetate units in the copolymer is 5 to 50% by weight, and the content of acrylate-based and / or methacrylate-based units is 0. .0
1 to 10% by weight, characterized in that an adhesive film is prepared from the photocurable adhesive using a T-die or a calendar roll, and then a polarizing film and a protective film are superposed on each other via the adhesive film. A method for manufacturing a polarizing plate for a liquid crystal display device.