JPH09159829A - Polarizing plate for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase adhesion and various kinds of durability, to simplify the structure and to manufacture at a low cost with excellent productivity by forming a adhesive layer, composed of a specific photosetting adhesive, to a substrate on one surface of a polarizing film SOLUTION: This polarizing plate is manufactured by forming the adhesive layer 4, which is composed of the photosetting adhesive consisting essentially of an ionomer resin produced by combining the molecules of an ethylene- methacrylic acid copolymer with each other by a metallic ion and is bonded directly to the liquid crystal cell surface substrate, on one surface of the polarizing film 1 (the surface of the side bonded to the liquid crystal surface substrate). In such a case, the photosetting adhesive consists essentially of the ionomer resin produced by combining the molecules of the ethylene-methacrylic acid copolymer with each other by the metallic ion and the content of the methacrylic acid in the ionomer resin is 1-30wt.%, particularly preferably 5-25wt.%. And a photosensitizer is blended to cure the photosetting adhesive.

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, which is used in a liquid crystal display device in the field of optoelectronics for display utilizing the response of liquid crystal molecules to 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. 3, 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 liquid, there is a problem that it has no function of improving the polarization degree of the polarizing film.

Further, in each of the conventional polarizing plates, a protective film is adhered to both sides of the polarizing film, so that the number of laminated layers is large, the manufacturing is complicated, the productivity is low, and the cost is required. It was

The present invention has been made in order to solve the above-mentioned conventional drawbacks. It is excellent in adhesion and various durability, has high reliability, has a simple structure, and is manufactured at low cost and with high productivity. It is an object of the present invention to provide a polarizing plate for a liquid crystal display device to be obtained.

[0007]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies to achieve the above-mentioned objects, the present inventors have found that one surface of a polarizing film to be bonded to a liquid crystal cell surface substrate is When a photo-curable adhesive layer having an ionomer resin as a main component in which ethylene-methacrylic acid copolymers are bound to each other with metal ions, the adhesive is glass, a polycarbonate plate, an acrylic resin plate, or a polyester. Excellent adhesion to substrate materials commonly used as liquid crystal cell surface substrates, such as films, polyether sulfone films, and polyarylene films. Therefore, in addition to firmly adhering directly to the substrates, heat resistance, moisture heat resistance, and heat resistance It excels in various durability such as cooling and heating cycles, and does not affect the optical function of the polarizing film at all, but rather improves the polarization degree of the polarizing film. The cured film is flexible and rich in elasticity, so it has resistance to external impact and deformation. The polarizing film can be directly attached to the substrate by the adhesive layer without the protective film being attached to the substrate, and the strength and reliability of the liquid crystal display element can be obtained not only as the entire polarizing plate. It was found that it is possible to remarkably improve the sex.

Further, the adhesive layer has excellent performance as described above, and when the cured layer is compared with a conventionally used protective layer for a polarizing film of acetyl cellulose (protective film), Since it has a protective function equal to or more than, and the protective film of acetyl cellulose type is hydrophilic and has almost no moisture resistance, the adhesive layer is hydrophobic, so that the durability of the polarizing film is improved. Therefore, not only the protective film laminated on one surface of the polarizing film and adhered to the liquid crystal cell surface substrate as described above can be omitted, but the protective film on the other surface of the polarizing film can be omitted. It has been found that it is effective to form a protective layer made of the above photocurable adhesive on the other surface of the film.

Since it is possible to omit the provision of the protective film in this way, the structure of the polarizing plate is simplified, and it has been found that the polarizing plate can be manufactured more efficiently and at low cost. Invented.

Therefore, according to the present invention, (1) in a polarizing plate adhered to a liquid crystal cell surface substrate of a liquid crystal display device, one molecule of an ethylene-methacrylic acid copolymer is bonded to one surface of a polarizing film by a metal ion. A polarizing plate for a liquid crystal display device, characterized by comprising forming an adhesive layer with the substrate, which is made of a photocurable adhesive containing an ionomer resin as a main component,
And (2) a protective layer formed on the other surface of the polarizing film, the protective layer including a photocurable adhesive containing an ionomer resin as a main component in which intermolecular ethylene-methacrylic acid copolymers are bonded with metal ions. A polarizing plate for a liquid crystal display device is provided.

The present invention will be described in more detail below. As shown in FIGS. 1 and 2, the polarizing plate of the present invention has one surface of the polarizing film 1 (the surface on the side bonded to the surface substrate of the liquid crystal cell) of ethylene. It is composed of a photo-curable adhesive containing an ionomer resin as a main component in which methacrylic acid copolymers are bound to each other by metal ions, and an adhesive layer 4 which is directly adhered to a liquid crystal cell surface substrate is formed. . In this case, as shown in FIG. 2, a protective layer 5 made of the same photo-curable adhesive may be formed on the other surface of the polarizing film 1, and the lamination of the protective film 2 as shown in FIG. 3 may be omitted. Although preferable, in some cases, as shown in FIG. 2, the protective film 2 may be attached to the other surface of the polarizing film 1 via an adhesive 3. In the case of the embodiment shown in FIG. 2, the protective film 2 and the adhesive 3 may have a known structure, but the adhesive 3 is preferably formed of the same photocurable adhesive as described above.

Here, as described above, the photocurable adhesive is mainly composed of an ionomer resin in which the intermolecular molecules of the ethylene-methacrylic acid copolymer are bonded with metal ions. In the resin, the content of methacrylic acid in the ethylene-methacrylic acid copolymer is preferably 1 to 30% by weight, particularly preferably 5 to 25% by weight. If the content is less than 1% by weight, the ionic cross-linking effect may decrease, which may lead to a decrease in adhesive strength.
If it exceeds 30% by weight, the workability may deteriorate.
Examples of the metal ions include metal cations such as sodium, zinc, magnesium, and lithium. The degree of ionization by these metal ions is preferably from 5 to 80%, more preferably from 7 to 70%. If the ionization degree is less than 5%, the transparency is lowered, and 8
If it exceeds 0%, the workability may decrease.

A photosensitizer is added to cure 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 as a mixture 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 ionomer resin.

Further, a silane coupling agent can be added to the adhesive of the present invention as an adhesion promoter. Examples of the silane coupling agent include 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 usually 0.01 to 5 parts by weight with respect to 100 parts by weight of the above ionomer resin.

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

As the compound to be used for this purpose, acrylic acid or methacrylic acid derivatives, for example, esters and amides thereof are the most common. In this case, as the ester residue, in addition to an alkyl group such as methyl, ethyl, dodecyl, stearyl, and lauryl, a cyclohexyl group, a tetrahydrofurfuryl group, an aminoethyl group,
-Hydroethyl group, 3-hydroxypropyl group, 3-chloro-2-hydroxypropyl group and the like. Esters of acrylic acid or methacrylic acid with polyfunctional alcohols such as ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, and pentaerythritol are also used. A typical amide is acrylamide. Examples of the allyl group-containing compound include triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, diallyl maleate, and the like. One kind or a mixture of two or more kinds of the above ionomer resins 0.1 to 100 parts by weight
It is used by adding 50 parts by weight, preferably 0.5 to 30 parts by weight. If the amount is less than 0.1 part by weight, the effect of improving the mechanical strength may be reduced, and if the amount is more than 50 parts by weight, workability and film forming property during preparation of the adhesive may be reduced.

Further, a hydrocarbon resin can be added to the adhesive of the present invention for the purpose of improving processability such as processability and bonding. In this case, the hydrocarbon resin to be added may be either a natural resin or a synthetic resin. Rosin, rosin derivatives, and terpene resins are preferably used in the natural resin system. For rosin, gum-based resins, tall oil-based resins, and wood-based 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, terpene-based resins such as α-pinene and β-pinene, as well as terpene phenol resins can be used. Also, as other natural resins, dammar,
It does not matter if you use corbal or shellac. On the other hand, in the case of synthetic resins, petroleum resins, phenol resins, and xylene resins are preferably used. Petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, hydrogenated petroleum resins, pure monomer petroleum resins,
Coumarone indene resin can be used. As the phenolic resin, an alkylphenol resin and a modified phenol resin can be used. As the xylene-based resin, a xylene resin or a modified xylene resin can be used.

The addition amount of the above-mentioned hydrocarbon resin is appropriately selected, but is 1 to 100 parts by weight of the above ionomer resin.
The amount is preferably 200 parts by weight, more preferably 5 to 150 parts by weight.

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 some cases, additives such as silica gel, calcium carbonate, silicon copolymer fine particles and the like may be contained in a small amount.

In the present invention, the method for forming the adhesive layer made of the above adhesive on one surface of the polarizing film is not particularly limited, but the ionomer resin and the above additives are kneaded by a roll mill, a kneader or the like, and then this is kneaded. calendar,
A film having a desired width and film thickness is formed by a film forming apparatus such as a roll, a T-die extruder, and inflation, and then this film is laminated by, for example, a hot press, an extruder, a direct laminating method by a calender, and heated by a film laminator. It can be laminated on one surface of the polarizing film using a method such as a pressure bonding method.

In forming the film, embossing may be performed in order to prevent blocking and facilitate deaeration during pressure bonding with the polarizing film or the liquid crystal cell surface substrate. The width of the film-forming film is selected according to the width of the polarizing film, but the film thickness is preferably 5 to 1000 μm, particularly preferably 10 to 800 μm. If the film thickness is less than 5 μm, the moisture permeability may be poor, and conversely, if it exceeds 1000 μm, the light transmittance may be reduced.

Further, the components of the adhesive layer are uniformly mixed and dissolved in a suitable solvent, the solution is directly applied on one surface of the polarizing film, and the solvent is dried to form an adhesive layer on one surface of the polarizing film. It is also possible to adopt a method in which the above solution is coated on a release paper or the like, the solvent is dried, and the resulting film is transferred and laminated on one surface of the polarizing film.

The same method can be adopted when forming a protective layer made of the above adhesive on the other surface of the polarizing film.

The polarizing film used in 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 can be cured by irradiating the laminated body with ultraviolet rays using a normal 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 polarizing film is laminated with the adhesive film of the present invention, and the temperature is 50 to 120 ° C., especially 70 to 1
0.01 to 20 kg / cm ² at 00 ° C., especially 0.1 to 1
2 to 20 minutes under a pressure of 0 kg / cm ² , especially 5
It is recommended to perform photocuring after heating and pressing for 10 minutes.

[0028]

The polarizing plate for liquid crystal display device according to the present invention comprises:
The curable adhesive layer is not only excellent in flexibility, elasticity, and impact resistance, and also has excellent adhesiveness with a polarizing film, and is often used as a substrate for liquid crystal cells such as glass, polycarbonate plate, acrylic resin plate, polyester film, and poly film. Excellent adhesion to ether sulfone film, polyarylene film, etc.
The strength and reliability of the liquid crystal display device are extremely improved.

Further, since the processing can be carried out at a low temperature, there is no adverse effect on the polarizing film layer having a low heat resistance limit.
It can be bonded to a polarizing film or a liquid crystal cell surface substrate. Moreover, like conventional liquid adhesives containing a large amount of acrylic monomers, swelling the surface of the polarizing film, or because it does not scratch it, without any reduction in the function as a polarizing plate, Lamination can be performed. Furthermore, in terms of durability such as heat resistance, moisture heat resistance, and cold heat resistance cycle, the adhesive layer crosslinked by photocuring has a high durability as described above, and in particular moisture, humidity, and various gases can be prevented from entering, so that durability is improved. Low polarization film and deterioration of liquid crystal layer can be sufficiently prevented. This is not observed in conventional liquid adhesives containing an acrylic monomer or oligomer as a main component and is a particularly preferable point.

Moreover, the curable adhesive layer in the polarizing plate of the present invention does not have the five-layer structure of protective layer / adhesive layer / polarizing film / adhesive layer / protective layer as in the conventional polarizing plate, but has the function of adhesion and protection. Since it also serves as a polarizing plate, the number of constituent members can be greatly reduced, and the labor for bonding can be greatly reduced, so that the polarizing plate can be provided at a low cost. In addition, if a protective layer made of an adhesive similar to the curable adhesive layer is formed on the other surface of the polarizing film, the above effect can be more effectively exhibited.

[0031]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] Formulation No. shown in Table 1 After uniformly kneading the mixture of A in a roll mill set at 70 ° C., an adhesive having a thickness of about 50 μm was used at a pressure of 0.5 kg / cm ² at 70 ° C. for 10 minutes using a heating and pressurizing machine. Two films were prepared.

On the other hand, polyvinyl alcohol prepared in advance
The polarizing film in which iodine is adsorbed and stretched and oriented on the above 2
It is sandwiched by a sheet of adhesive film and laminated, and this laminated body is
0kg / cm^Twoof Pressurized at 100 ° C for 5 minutes
For 30 seconds on each side of the 4 kW high pressure mercury lamp.
Ultraviolet irradiation was performed for a total of 1 minute to obtain polarizing plate A shown in FIG.
Was.

Next, this polarizing plate was subjected to 10 ° C. at 10 ° C.
Heat resistance test for 00 hours and 100 at 80 ° C, 95% RH
A 0-hour moist heat resistance test was carried out, and the presence or absence of abnormalities in appearance such as yellowing, peeling, shift, and foaming was examined, and if abnormalities were found, it was determined to be unacceptable, and if not, it was determined to be acceptable. Table 2 shows the results.

Further, a polyester film, a polycarbonate plate, and a glass plate are laminated on one surface of the above-mentioned laminated body as adherends, respectively, and subjected to heating and pressurization and ultraviolet irradiation in the same manner as above to complete curing, The adhesive force between the adhered body and the adhesive film (adhesive layer) was measured.
Table 3 shows the results.

[Example 2] In Example 1, the composition N
o. Compound No. instead of A. A polarizing plate B was produced in the same manner as in Example 1 except that the mixture of B was used, and the same evaluation as in Example 1 was performed.

[Example 3] Formulation No. shown in Table 1 20 g of the mixture of C was dissolved in 80 g of toluene at 70 ° C., and the obtained uniform solution was applied on one surface of the same polarizing film as in Example 1 and uniformly spread by a bar coating method.
The solvent was dried by placing it in an oven at 0 ° C. for 1 hour to form a dry adhesive layer having a dry thickness of 30 μm. Further, on the other surface of the polarizing film, a laminate obtained by forming a dry protective layer having the same thickness in the same manner was cured in the same manner as in Example 1 to obtain a polarizing plate C.

The polarizing plate C was subjected to a heat resistance test and a moist heat resistance test in the same manner as above.

Further, a polyester film, a polycarbonate plate and a glass plate are respectively laminated on one surface of the above-mentioned laminated body, placed in a rubber bag, and the air inside is deaerated by a vacuum pump in an oven at 120 ° C. for 30 minutes. After heating for 1 minute, the product was taken out from the oven and the rubber bag, and Example 1 was used.
Ultraviolet irradiation was carried out in the same manner as in, and the adhesive strength was measured in the same manner as above.

Comparative Example Methyl methacrylate 10 was applied to one side of each of the two triacetyl cellulose protective films.
0 parts by weight, 20 parts by weight of glycidyl methacrylate, and 3 parts by weight of azobisisobutyrylonitrile are applied as a mixed liquid material, which is attached to both sides of the polarizing film and pressure-bonded.
Polarizing plate D was obtained by leaving it in an oven kept at 00 ° C. for 30 minutes. An evaluation test was performed on this polarizing plate D in the same manner as in Example 1.

[0041]

[Table 1]

[0042]

[Table 2]

The polarizing plates of Examples A to C were all smooth polarizing plates having no distortion or unevenness by visual inspection after production. On the other hand, in the polarizing plate D of the comparative example, it was observed that the transmission image looks distorted due to optical fluctuations in the boundary layer of the bonding surface due to dissolution and swelling of the adherend surface by the acrylic monomer. It was

As is clear from the results shown in Table 2, the polarizing plates of the examples were formed in the cured adhesive layer and the protective layer with high adhesive force between the cured adhesive layer and the protective layer and the polarizing film. Due to the high durability due to the cross-linked structure, heat resistance,
No abnormality was found in both of the humidity and heat resistance tests, and it was confirmed to have high reliability. On the other hand, the polarizing plate D of the comparative example
In the heat resistance test, a yellowing phenomenon was observed, and in the heat and humidity resistance test, adhesive peeling was observed in a portion of about 2 mm from the peripheral portion.

[0045]

[Table 3]

From the results shown in Table 3, regarding the adhesive strength of the polarizing plate of the embodiment, the adhesiveness of 3 which is currently highly versatile as a substrate of a liquid crystal cell.
It was confirmed that each of the adherends showed a high adhesive force of 2.0 kgf / cm or more.

From the above, in the polarizing plate of the example, the curable adhesive layer and the protective layer provided on both sides of the polarizing film have the function of the protective film of the polarizing film, and the liquid crystal cell and other liquid crystal peripheral members. It was confirmed to be a highly reliable polarizing plate that also has an adhesive function for assembly with. Also, like the conventional polarizing plate, two adhesive layers,
Unlike a five-layer structure polarizing plate with two protective layers added, only three layers exhibit the functions of five layers, so that it is possible to provide a polarizing plate that is inexpensive and has excellent productivity. Was recognized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a conventional polarizing film.

[Explanation of symbols]

 1 Polarizing Film 2 Protective Film 3 Adhesive 4 Adhesive Layer 5 Protective Layer

Claims (7)

[Claims] 1. A polarizing plate which is adhered to a liquid crystal cell surface substrate of a liquid crystal display device, wherein an ionomer resin having an ethylene-methacrylic acid copolymer intermolecularly bound by metal ions is used as a main component on one surface of the polarizing film. A polarizing plate for a liquid crystal display device, which is formed by forming an adhesive layer made of a photocurable adhesive with the substrate. 2. An ethylene-containing resin is provided on the other surface of the polarizing film.
The polarizing plate for a liquid crystal display device according to claim 1, wherein a protective layer made of a photo-curable adhesive containing an ionomer resin as a main component in which methacrylic acid copolymers are bound to each other by metal ions. 3. The photo-curable adhesive is obtained by adding 0.1 to 10 parts by weight of a photosensitizer and 0.01 to 5 parts by weight of a silane coupling agent to 100 parts by weight of the above ionomer resin. The polarizing plate for a liquid crystal display device according to claim 1 or 2. 4. A photocurable adhesive is prepared by adding 0.1 to 50 parts by weight of at least one of an acryloxy group-containing compound, a methacryloxy group-containing compound and an allyl group-containing compound to 100 parts by weight of the above ionomer resin. The polarizing plate for a liquid crystal display device according to claim 1, wherein 5. The photocurable adhesive is obtained by adding 1 to 200 parts by weight of a hydrocarbon resin to 100 parts by weight of the ionomer resin. Polarizing plate for liquid crystal display device. 6. The methacrylic acid content of the ethylene-methacrylic acid copolymer in the ionomer resin is from 1 to 1.
30% by weight, and the degree of ionization due to metal ions is 5
It is 80%, The polarizing plate for liquid crystal display devices of any one of Claim 1 thru | or 5 characterized by the above-mentioned. 7. The polarizing film is obtained by adsorbing iodine and / or a dichroic dye on a hydrophilic polymer containing a hydroxy group, and stretching and orienting the adsorbed iodine and / or dichroic dye. Polarizing plate for liquid crystal display device.