JPS6045401B2 - Polarizer - Google Patents

Description

[Detailed description of the invention] This invention relates to improving the durability of polarizing plates.

In recent years, as electronic watches, electronic desktop calculators, and the like have become smaller and lighter, their display devices are also being replaced with conventional light emitting diodes by liquid crystal display devices, which are thinner and consume less power. The polarizing plate currently used in such display devices is a polarizing film made of a porvinyl alcohol film that is oriented by adsorbing iodine or the like. A cellulose film such as cellulose diacetate or cellulose triacetate is attached to the surface of the film.
However, since this polarizing plate uses a cellulose film as a surface protection film, it has poor water resistance and moisture resistance, and also lacks dimensional stability due to its high water absorption rate. These problems become more serious when a polarizing plate is attached to a liquid crystal panel using a pressure-sensitive adhesive. That is, a liquid crystal display device in which a polarizing plate is pasted and attached to a liquid crystal panel using a pressure-sensitive adhesive was subjected to a heating and humidification test at 65° C. for 5 days (95% R.H.) and a 50% R.H. H.
Accelerated tests such as dimensional changes when changing the temperature (40℃) and adhesion tests by immersion in water (7 days at 20℃) revealed that water absorption in the cellulose film at the interface between the adhesive and the polarizing plate When the polarization degree decreases as a result of the release of a foaming phenomenon, the degree of polarization decreases, and interfacial peeling occurs. On the other hand, urethane resin is known to have optical transparency equivalent to that of cellulose film, but when this resin is used as a surface protection film for a polarizing plate, it has a high water absorption rate (1% or more), and The disadvantage of this resin is that it causes severe discoloration, and because the resin has a high crosslinking density and a low molecular weight, it has poor processability into polarizing plates.In other words, when a polarizing plate is punched out, burrs and cracks occur on the cut edges. There is a drawback in the work that occurs when
It cannot be said that it is sufficient.

This invention was developed as a result of various studies in view of the state of the prior art.

That is, this invention provides a structure represented by the general formula (a) and/or (in the formula, R1: or (CH2)NOHR2:H or CH3 R3:H1(CH2)NOH or where n is an integer of 1 to 2). A copolymer having an average molecular weight of at least 10,000 obtained by copolymerizing one or more monomers (4) selected from the units and a vinyl monomer (B) represented by the general formula (c), The functional group or the functional group that can react with active hydrogen is 2
Acrylic polymer tree 4 reacted with a compound having 4 or more
The present invention provides a polarizing plate in which a layer of fat is formed on at least one side of a polarizing film, either directly or via an undercoat layer.

The polarizing plate of the present invention is obtained by copolymerizing the monomers represented by the general formula (A) and/or (I) with the vinyl monomer (B) represented by the general formula (C). By providing a specific acrylic polymer resin made by reacting a copolymer with a compound having two or more functional groups on at least one side of the polarizing film, various properties such as solvent resistance, mechanical strength, and adhesive strength are improved. There are products with improved properties and workability such as cutting workability and dimensional stability.

As the monomer represented by the general formula (a) used in this invention, acrylic acid amide, N-methylol acrylic amide, methacrylic amide, N-methylol methacrylic amide, etc. are suitable.

Monomers represented by the general formula (2) include acrylic acid,
Methacrylic acid, acrylic acid 2-hydroxyethyl ester, acrylic acid 2-hydroxypropyl ester,
Preferred examples include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl acrylate, and glycidyl methacrylate.

Examples of the vinyl monomer represented by the general formula (c) include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, pentyl acrylate, benzyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-methylcyclohexyl acrylate, tripromophenyl acrylate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylate t-butyl acid, 2-methacrylic acid
Ethylhexyl, cyclohexyl methacrylate, ethoxyethyl methacrylate, or styrene are preferably used.

One or more monomers (4) selected from the structural units represented by these general formulas (a) and/or (x) and general formula (c)
As for the copolymer formed by copolymerizing with the vinyl monomer (B) shown below, as a result of examining the cutting processability of a polarizing plate with an acrylic polymer resin layer formed using the copolymer, at least 10,000, more preferably from 20,000
It has been found that it is preferable to use a copolymer having an average molecular weight of 500,000. It is best to add the monomer to the copolymer in an amount of 1 to 2% by weight; if this range is exceeded, a suitable degree of crosslinking, sufficient mechanical strength, and solvent resistance cannot be obtained. I don't like it because there isn't. The copolymer is optically transparent and unoriented, with a 95% R.I. H. ×24
It has a water absorption rate of 3% or less at I-Terama. An appropriate amount of a compound having two or more functional groups capable of reacting with the functional group or active hydrogen in the copolymer is added to the copolymer having the average molecular weight specified in this way, and the copolymer and the compound are combined. An acrylic polymer resin is produced by reacting with. As the compound having two or more functional groups or functional groups capable of reacting with active hydrogen in the copolymer, one or more of the following are preferably used! be done.

(1) Examples of polyisocyanate compounds include aliphatic diisocyanates such as ethylene diisocyanate and 1,4-butane diisocyanate; aliphatic diisocyanates such as dicyclohexylmethane diisocyanate and cyclohexane diisocyanate; 2,6-tolylene diisocyanate; Aromatic diisocyanates such as 4''-cyphenylmethane diisocyanate, aromatic 4-triisocyanates such as triphenylmethane triisocyanate, and modified products thereof.

(2) Examples of melamine compounds include butyl etherified styrene melamine, trimethylol melamine, hexamethylol melamine, butyl etherified hexamethylol melamine, butyl etherified dimethylol guanamine, and the like. (3) Glycol compounds such as polyethylene glycol and trimethylolpropane.

(4) Examples of diamine compounds include hexamethylenediamine, metaphenyldiamine, diethylenetriamine, and tetramethylenediamine. (5) Other phenolic resin compounds such as resol type phenol, epoxy resin compounds, urea resin compounds, polyaldehyde compounds, polycarboxylic acids, and the like. These compounds are used in appropriate combinations depending on the type of functional group or active hydrogen contained in the above-mentioned copolymer.

The acrylic polymer resin obtained by mixing and reacting the above copolymer with a compound can be prepared using a solvent that does not inhibit the polarization properties of the polarizing film, such as ethyl acetate, butyl acetate, cellosolve acetate, methyl glycol acetate, ethyl glycol acetate, and methoxy. Consists of a polyvinyl alcohol film diluted with butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, methylene chloride, toluene, xylene, etc. to the desired viscosity and imparted polarization by adsorbing and orienting polarizers such as iodine and dyes. It is coated on at least one side of the polarizing film directly or through an undercoat layer made of a substance such as a silane coupling agent so that the thickness after drying is 10 to 300μ, preferably 50 to 150μ, and heated at 75 to 95°C. 1
0 to 3 powders are dried to volatilize the solvent, and then heated at 60 to 90°C for 30 to 100 hours to harden, forming a resin layer firmly adhered to the polarizing film surface directly or via an undercoat layer. .

The presence of the undercoat layer not only increases the adhesive strength between the polarizing film and the resin layer, but also has an insulating effect that prevents the diffusion of iodine from the polarizing film to the resin layer, and controls the surface tension of the polarizing film surface, thereby creating a small layer at the adhesive interface. It has the effect of effectively preventing air bubbles from being trapped, and is particularly preferred in the production of the polarizing plate of the present invention. In order to prevent deterioration of the polarizing properties of the polarizing film, the resin layer contains an ultraviolet absorber such as benzophenone, benzotriazole, or metal chelate having an absorption wavelength range of about 300 to 500n1μ for coloring. It is possible to contain an appropriate amount of transparent (including colored transparent) or opaque colorant, or fine particle powder such as metal powder such as aluminum powder, gold powder, or silver powder in order to reflect the light that has passed through the polarizing plate. can.

These ultraviolet absorbers and the like are preferably added at the same time as diluting the acrylic polymer resin with a solvent, and used in a state where they are uniformly dispersed in the resin solution. Since the polarizing plate of the present invention has a layer made of a specific acrylic polymer resin formed as a surface protective layer on the polarizing film surface as described above,
The adhesion between the polarizing film and the resin layer is strong, so phenomena such as lifting, peeling, and foaming are extremely rare, and it also has excellent solvent resistance, dimensional stability, and cutting workability. has.

Examples of this invention will be shown below.

The middle part of the text indicates the weight unit. Note that the polarizing film (H1) in Examples was produced by the following manufacturing method.

Polarizing film (H1) A polyvinyl alcohol film (trade name, Kuraray Vinylon Film #7500) was immersed in an aqueous solution adjusted to an iodine concentration/weight%, a potassium iodide concentration of 2% by weight, and a boric acid concentration of 4% by weight. A polarizing film with a transmittance of 41% and a degree of polarization of 92% (
A thickness of 25 μm) was prepared.

Example 1 Methyl methacrylate (Corporation) part, acrylic acid w part, butyl acetate 1 (1) part, benzoyl peroxide (BPO)
0.3 part of the mixture was reacted by heating at 65°C for 1 ctf to obtain a copolymer solution (20°C1 viscosity 95 poise, average molecular weight 280,000).

To 4 parts of the solution, 4 parts of butyl etherified methylolmelamine and 17 parts of toluene are added to obtain an acrylic polymer resin solution having a viscosity of 2.3 poise.

The above polarizing film (H1) was immersed in this resin solution bath, and one drop was placed in an open tank kept at 80°C, and this operation was repeated until the film thickness was increased on both sides of the polarizing film (H1). An acrylic polymer resin layer having a thickness of 42.5 μm was formed, and this was further heated in an open air tank maintained at 80° C. to obtain a polarizing plate of the present invention.

Its properties are shown in Table 1. Examples 2 to 9 Acrylic polymer resins were produced with the following formulations, and polarizing plates were obtained in the same manner as in Examples.

Its properties are shown in Table 1.

Comparative Example 1 Cellulose triacetate films with a thickness of 40 μm were attached to both sides of a polarizing film (H1) via an acrylic adhesive (manufactured by Daicel Corporation, trade name: Cevian A) (thickness: 5 μm) to obtain a polarizing plate.

Comparative Example 2 A urethane resin solution consisting of the following composition was applied to both sides of a polarizing film (H1) so that the thickness after drying was 40μ, and two coats were dried at 80°C to obtain 7 polarizing plates. .

combination

Claims (1)

[Scope of Claims] 1. One or more monomers (A) selected from the structural units represented by the following general formula (a) and/or (b) and a vinyl monomer represented by the following general formula (c) An acrylic polymer resin obtained by reacting a copolymer with an average molecular weight of at least 10,000 obtained by copolymerizing (B) with a compound having two or more functional groups capable of reacting with the functional group or active hydrogen. A polarizing plate formed by forming a layer on at least one side of a polarizing film (not including a polarizing film made of an ethylene-vinyl alcohol film) either directly or via an undercoat layer. General formula (a) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (b) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [R_1 in the formula: or (CH_2)_nOHR_2: H
or CH_3R_3:H, (CH_2)_nOH or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, n is an integer of 1 to 2] General formula (c) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [X in the formula: H or CH_3 (i) COOR_4 Y: [R_4: Alkyl group of C_1 to C_1_2 ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼] (ii) ▲ Mathematical formulas, chemical formulas, tables, etc. ▼2 The polarizing plate according to claim 1, wherein the polarizing film is made by adsorbing and orienting iodine to a polyvinyl alcohol film. 3. The polarizing plate according to claim 1, wherein the underlayer is a coating layer of a silane wrapping agent.