JPS595208A - Manufacture of polarizing plate - Google Patents

Abstract

PURPOSE:To obtain a polarizing plate having high initial adhesive strength by simple adhesion by adhering a polarizing film to a polyacrylic resin film with a specified liq. substance in-between in the presence of a polymn. initiator and a decomposition accelerator. CONSTITUTION:When a polarizing film is adhered to a polyacrylic resin film which is used as a surface protective layer, a liq. substance contg. a vinyl monomer and/or oligomer as the principal component and making the surface part of the resin film sticky by dissolution or swelling is used. A polymn. initiator is added beforehand to one of the resin film and the liq. substance, and a decomposition accelerator to the other. The polarizing film is, e.g., obtd. by allowing iodine and/or a digenetic dye to be adsorbed on a hydrophilic polymer film and by carrying out orientation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a polarizing plate used in liquid crystal display devices and the like.

In recent years, liquid crystal display devices in which a liquid crystal display cell and a polarizing plate are combined have been widely used in desktop electronic computers, playback clocks, and the like.

Such a polarizing plate is generally composed of a polarizing film and a plastic film such as an acetate film or a polyacrylic resin film as a surface protective layer.

However, polyurethane adhesives are mostly used to bond polarizing films and glass films from the viewpoint of optical properties and durability as polarizing plates.

However, polyurethane adhesives have problems such as relatively low initial adhesive strength and cumbersome adhesive work.

Accordingly, an object of the present invention is to provide a method for manufacturing a polarizing plate that has strong initial adhesive strength and requires less adhesive work.

Another object of the present invention is that when bonding a polarizing film and a polyacrylic resin film as a surface protective layer of the film, a vinyl monomer that melts or swells the surface layer of the resin film to make it sticky. The polarizing film is prepared by using a liquid material containing polymers and/or oligomers as main components, containing a polymerization initiator in either the resin film or the liquid material, and containing a decomposition accelerator in the other. and a resin film, the liquid substance is present between the resin film and the liquid substance is polymerized,
This is achieved by adhering the polarizing film and the resin film.

According to the present invention, the surface layer portion of the polyacrylic resin film to be adhered to the polarizing film becomes sticky by being dissolved or swollen with a liquid material mainly composed of vinyl monomers and/or oligomers. It contacts the polarizing film surface reliably and with a large adhesive area, and the interface with the polarizing film is formed by the polyacrylic resin component and the polymer of the liquid material. It has the characteristics of being strong and can be bonded in a short time.

The polarizing film used in carrying out the present invention (1) is a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene-vinyl acetate copolymer film, or a dichroic dye. Examples include iodine and/or dye-based polarizing films, polyene-based polarizing films in which polyene is oriented by dehydrating a polyvinyl alcohol film or dehydrochlorinating a polyvinyl chloride film, and these films usually have a U10 A material having a thickness of ~80t1m is used.

The polyacrylic resin film used as the surface protective layer of the polarized light 7 (lume) includes (meth)acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, etc. ``Functional monomers such as acrylic acid, maleic anhydride, itaconic acid, 2-hydroxyethyl (meth)acrylate, acrylamide, styrene, vinyl acetate, (
A polymer or copolymer obtained by polymerizing an unsaturated compound such as meth)acrylonitrile, preferably in a ratio of 100 to 50:O to 20:o to 3O (weight ratio), or the copolymer is further added to a polyisocyanate compound. A cross-linked copolymer cross-linked with a reagent such as
00 μm) is used.

Further, the vinyl monomer and/or oligomer is not particularly limited as long as it dissolves or swells the surface layer portion of the polyacrylic resin film to make it sticky, and examples thereof include the following.

- Functional vinyl monomers: for example methyl (meth)acrylate, ethyl (methanoacrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl ( Alkyl or cycloalkyl acrylates or methacrylates such as meth)acrylate, lauryl (meth)acrylate, vinyl acetate, vinyl propionate, (meth)acrylonitrile, styrene, vinyltoluene, (meth)acrylic acid, 2
- and polyfunctional vinyl monomers such as hydroxy esters of (meth)acrylic acid such as droxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, diethylamine ethyl (meth)acrylate, etc., e.g. ethylene Glycol di(methacrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate,
Functional oligomers such as ethylene glycol or globylene glycol diester of (meth)acrylic acid, trimethylolpropane tri(meth)acrylate, tetramethylolpropane tetra(meth)acrylate, such as meth)acrylate: For example, polyester resin and (
Polyfunctional oligomers such as polyester 1000(meth)acrylate obtained by reaction with meth)acrylic acid
: For example, polyethylene glycol di(meth)acrylate, epoxy(meth)acrylate obtained by reaction of epoxy resin and (meth)-acrylic acid, polyisocyanate compound and hydroxyalkyl(meth)'7
17 Urethane (meth)acrylate obtained by reaction with L/-5, polyester resin and (meth)acrylate
Liquid materials containing these vinyl monomers and/or oligomers as main components, such as polyester di(meth)acrylate or polyether di(meth)acrylate obtained by reaction with acrylic acid, are It is composed of one or more types of oligomers and/or oligomers, and its viscosity is preferably adjusted to a range of 0.01 to 100 poise, and practically 50 poise or less, considering coating workability. The liquid substance is applied to the interface between the polyacrylic resin film and the polarizing film with a polyacrylic resin film thickness lo
1 to 5009β based on oμm, preferably 100
It is applied in the range of ~3009/d.

The combinations of these vinyl monomers and/or oligomers and the polyacrylic resin film are the same,
However, according to repeated experiments conducted by the inventors,
It has been found that combinations with slightly poor compatibility, such that the system becomes slightly cloudy when the surface layer portion of the film dissolves or swells, provide stronger adhesive strength. In addition, an acrylic copolymer with good compatibility may be added to the above vinyl monomer and/or oligomer in an amount of 30% by weight or less for the purpose of improving coating workability. Alternatively, a polymerization initiator that generates active radicals by the action of a decomposition accelerator, which will be described later, is blended into either the liquid material mainly composed of oligomers or the polyacrylic resin film.

Examples of polymerization initiators include organic peroxides such as benzoyl peroxide, methyl ethyl ketone peroxide, lauroyl peroxide, and cumene hydroxy peroxide, as well as hydrogen peroxide and ammonium persulfate, which have a reaction initiation temperature of 20=H1O°C. are used and these are 0
．． It is blended in an amount of 0.01 to 10% by weight, practically 0.1 to 4% by weight.

Further, a decomposition accelerator is blended in the other one of the polyacrylic resin film or liquid material that is not blended with a polymerization initiator.

As a decomposition accelerator, N-N-dimethylaniline, N.
Examples include N-dimethyl para-toluidine, cobalt naphthenate, copper naphthenate, thiourea, acetylthiourea, and a condensate of n-butyraldehyde and aniline, and the number of blended parts is 0.01 to 10 parts by weight, preferably 0.1 ~2 parts by weight. If the number of blended parts is less than 0 or 11 parts by weight, a sufficient effect of promoting decomposition of the polymerization initiator cannot be obtained, and if it is more than 10 parts by weight, the adhesive strength may decrease or the optical properties of the polarizing plate may be adversely affected, so it is preferable. do not have.

In the production method of the present invention, a liquid material mainly composed of vinyl monomers and/or oligomers containing the other one is added to a polyacrylic resin film containing either a polymerization initiator or a decomposition accelerator. Apply at a thickness of 0.1 to 1009/d,
The surface of the film is melted or swollen to become sticky, a polarizing film is superimposed on the coated adhesive surface, and the liquid is left to stand at room temperature for 12 hours or more, thereby polymerizing the liquid and forming a polyacrylic resin film and a polarizing film. Provides a polarizing plate with strong adhesion. Moreover, when it is desired to further promote the polymerization reaction, heat treatment at 50°C to 80°C is effective.

In the above method, the surface of the polarizing film is preliminarily coated with a 1.6-
Polyincyanate compounds such as hexane diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and modified products thereof, or vinyltriethoxysilane, γ
-glycidoxypropyltrimethoxysilane, N-β(
Surface treatment using a silane compound such as (aminoethyl) γ-aminopropyltrimethoxysilane or γ-aminopropyltriethoxysilane can effectively yield a polarizing plate with stronger adhesive strength.

Examples of the present invention will be shown below. The term ``bunchubu'' refers to the middle part of the text.

Example 1 100 parts of methyl methacrylate, 10 parts of glycidyl methacrylate, and 1 part of benzoyl peroxide were applied to one side of a 30 μm thick polyacrylic resin film mainly composed of methyl methacrylate (containing 0.2 parts of dimethylaniline). 1 (lβ) of the liquid mixture was applied, and this was applied to both sides of the polarizing film using the method described above and pressure bonded.
A polarizing plate was obtained by standing at 30° C. for 48 hours.

Two-piece optical film> Polyvinyl alcohol film 11.7. The iodine concentration is 1×, the potassium iodide concentration is 2×, and the boric acid concentration is 4.
Crush it in an aqueous solution adjusted to a certain temperature, and boil it at 5 (]℃ for 3 to 4 hours.
xj (stretched to produce a polarizing film with a transmittance of 41% and a degree of polarization of 92 (thickness 30 μrr + "l) 1. rc -1
Example 2 One side of a polyacrylic resin film (containing 411 parts of methyl methacrylate) having a thickness of 501 parts and mainly composed of methyl methacrylate was coated with 1 part of butyl methacrylate.
00 parts, styrene 10 parts and cobalt naphthenate () 5
Apply 5 q/vl of the liquid mixture of 100 ml and apply the coating shim on both sides of the polarized V (- film) used in Example 1.
: A polarizing plate was obtained by leaving it at room temperature for 92 hours.

Example 3 101 parts of methyl methacrylate was coated on one side of a 20 part m thick film (mainly composed of methyl methacrylate, containing 01 parts of luidine).
) parts, 5 parts of nitroquinoethyl methacrylate, 1.3 parts of tolylene dicyane, methyl methacrylate acid °-
A liquid mixture consisting of 10 parts of a copolymer of ethyl acrylate = 70:3 (+) and 02 parts of benzoyl peroxide was applied to 209β, and this was attached and pressure-bonded to both sides of the image star polarizing film in the following manner. , and left at 50° C. for 24 hours to obtain a polarizing plate.

(Polarizing film 5) Using a polyvinyl alcohol film as a dehydration catalyst, the polyvinyl alcohol film was immersed in an aqueous solution containing 0161 branching molecules using hydrochloric acid as a dehydration catalyst, and then stretched to 2 times, and then further stretched to 2.5 times at 50° C. and heat treated. The film on which the zero-order polyene has been formed is immersed for 10 minutes in an aqueous solution (liquid temperature 30° C.) containing a dichroic dye with a weight of O1%, the dye is adsorbed and oriented, and the film is dried. Transmittance 43%, t, with neutral hue
II A polyene-dichroic dye polarizing film (thickness 25 μ=n 2 ) with a luminous intensity of 94% is obtained.

Example 5 2 parts of methyl ethyl ketone peroxide was mixed with 100 parts of a resin solution consisting of methyl methacrylate-ethyl acrylate copolymer, and this was cast onto a release liner so that the thickness after drying was 3011 m. A polyacrylic resin film is obtained. On one side of this film, 10 g or more of a mixture consisting of 100 parts of methyl methacrylate, 10 parts of methacrylic acid, and 05 parts of cobalt naphthenate was added.
Coating and pasting on both sides of the polarizing film of Example 1, 4
The polarizing plate was left for 24 hours at 0°C.

Table 1 shows the test results of Examples 1 to 5.

Test method in Table 1 of Table 1 Adhesion: A cut is made at the interface between the polyacrylic resin film and the polarizing film of the sample, and it is measured whether the two can be peeled off. Those that could not be peeled off were judged to be unremovable.

Polarization degree: Average parallel transmittance (YO) by overlapping two samples cut at a 45 degree angle to the polarization axis of the polarizing plate.
and the average orthogonal transmittance (Y2O) were measured, and these transmittances were drawn and fitted into the above equation.

As is clear from the above examples, the polarizing plate produced by the manufacturing method of the present invention has excellent adhesion between the polyacrylic resin film and the polarizing film, and is notable for its durability and thermal stability. be.

patent applicant Nitto Electric Industry Co., Ltd. Representative Sanbe Hijikata

Claims (1)

[Claims] When adhering a polarizing film and a polyacrylic resin film as a surface protective layer of the film, the main component is a vinyl monomer and/or oligomer that dissolves or swells the surface layer of the resin film to make it stick. Using a liquid material, either the resin film or the liquid material contains a polymerization initiator and the other contains a decomposition accelerator,
A method for manufacturing a polarizing plate, characterized in that the liquid substance is present between the polarizing film and the resin film to polymerize and bond the polarizing film and the resin film.