JPS595209A - Manufacture of polarizing plate - Google Patents

Abstract

PURPOSE:To obtain a polarizing plate with superior durability and heat stability adhering a polarizing film to a soluble polyester resin film with a specified liq. substance in-between in the presence of a polymn. initiator and a polymn. accelerator. CONSTITUTION:When a polarizing film is adhered to a soluble polyester resin film, 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 polymn. accelerator to the other. The liq. substance is held between the films and polymerized by pressing to adhere the films to each other. A uniaxially stretched polyester resin film obtd. by stretching an insoluble polyester resin film only in one direction is preferably used as the soluble polyester resin film in consideration of the use of the resulting polarizing plate independent of the front and rear sides.

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 have been widely used in inorganic desktop electronic meters, °1 electronic clocks, instruments, etc., and the demand for polarizing plates has accordingly increased.

In particular, their use in instruments, such as automobiles, which are used under harsh conditions, is being considered, and the polarizing plates used in these instruments need to have higher durability and thermal stability than ever before. It is required.

Most conventional polarizing plates have been provided with a surface protective layer made of optically transparent plastics such as acetates and polyacrylic resins on the surface of a polarizing film.

These polarizing plates can be used without any problems when used under relatively gentle conditions, such as in desk-top electronic computers, but when used under harsh conditions, such as in instruments such as those mentioned above, There are problems with its durability and thermal stability, and improvements are desired.

In response to such demands, a method has been proposed in which the problems of durability and thermal stability are solved by using a polyester resin film as a surface protective layer on the surface of a polarizing film.

However, the polyester resin film itself has durability and thermal stability, but when viewed as a polarizing plate, the adhesive strength between the polarizing film and the polyester resin film is strong, and the polarizing properties of the polarizing film are The conditions for taking advantage of the properties of polyester resin films include not inhibiting the properties of polyester resin films.

However, conventionally used adhesives made of a mixture of a polarizing film, a borated polyester resin, and a polyisocyanate compound are widely used, but although the adhesive strength is sufficient, there are problems due to the polyisocyanate compound blended. However, the bonding operation is extremely complicated, and there is a problem that the polarizing properties of the polarizing film are often deteriorated.

The present invention provides a novel method for manufacturing a polarizing plate that solves the problems of the prior art, and its gist is as follows:
When bonding a polarizing film and a soluble polyester resin film, a liquid material mainly composed of vinyl monomers and/or oligomers that dissolves or swells the surface layer of the resin film to make it sticky is used to bond the polarizing film and the soluble polyester resin film. Alternatively, either one of the liquid materials contains a polymerization initiator and the other one contains a polymerization accelerator, and the liquid material is placed between the polarizing film and the resin film and pressed together to form the liquid material. The method involves polymerizing and bonding the polarizing film and the resin film.

Another aspect of the present invention is that when bonding a polarizing film and an insoluble polyester resin film provided with a soluble polyester resin layer via the resin layer, at least a surface layer portion of the resin layer is melted or swollen to become adhesive. A liquid material containing a vinyl monomer and/or oligomer as a main component is used, one of the resin layer or the liquid material contains a polymerization initiator, and the other contains a polymerization accelerator, and the polarized light The liquid material is made to exist between the film and the resin layer, and the liquid material is polymerized by press-bonding the film and the resin layer, thereby bonding the polarizing film and the insoluble polyester resin film.

According to the first aspect of the present invention, the resin film and the polarizing film are brought into sufficient contact with each other so that the liquid material brought into contact with the soluble polyester resin film dissolves or swells the surface layer of the film to make it sticky. Strong adhesive strength is obtained due to the fact that the polyester that has been dissolved or swollen and the liquid polymer form a microscopically non-uniform sea-island structure at the interface. Moreover, since volatile substances such as solvents are not used, a good polarizing plate can be obtained that is free from factors such as bubbles that impede polarization characteristics.

In the second invention as well, the soluble polyester resin layer provided on the bonding surface VC of the insoluble polyester resin film dissolves or swells with a liquid substance and becomes sticky. A polarizing plate with strong adhesive strength and excellent polarizing properties can be obtained.

The polarizing film used in carrying out the present invention includes a wood-loving polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and a saponified ethylene-vinyl acetate copolymer film. Iodine and/or dichroic dye-based polarizing film on which dichroic dyes are adsorbed and distributed, polyene-based polarizing film on which polyene is oriented by dehydrating polyvinyl alcohol film, and dehydrochloric acid on polyvinyl chloride film. Examples include polyene-based polarizing films that have been treated to orient polyene, and these are usually 1O~5
A material having a thickness of APS is used.

The polyester resin film used as a surface protective layer on one or both sides of the polarizing film is a soluble polyester resin film having a thickness of about 1θ to 500μ and made of polyester such as polyethylene terephthalate, polyethylene inphthalate, polyethylene ethylene phthalate, etc. Or an insoluble polyester resin film.

Therefore, from the viewpoint of light tube characteristics as a polarizing plate, it is preferable to use a uniaxially stretched soluble or insoluble polyester resin film stretched only in the vertical or horizontal axis direction, or a biaxially stretched soluble or insoluble polyester resin film stretched in the vertical and horizontal directions. A polyester resin film is preferable, and a uniaxially stretched film is more preferable since it can be used as a polarizing plate without distinguishing between the front and the back.

A preferable uniaxially stretched soluble or insoluble polyester resin film is stretched for at least 5 times, practically 50 to 800 times, only in the vertical or horizontal direction, and then stretched at 100° C. for 60 minutes or more.
It is directional heat set at 230°C for 5 minutes.

Therefore, unstretched material made of insoluble polyester resin, -
The axially stretched and biaxially stretched films do not dissolve or swell and become sticky in the liquid material mainly composed of vinyl monomers and/or oligomers, which will be described later, so that the adhesive strength targeted by the present invention can be obtained. It is something that cannot be done. For this purpose, the surface of the insoluble polyester resin film is laminated with a soluble polyester resin film or coated with a soluble saturated polyester resin to a thickness of approximately 3 to 50 μm.
It is necessary to form a soluble polyester resin layer of m.

The vinyl monomer and/or oligomer used in the practice of the present invention 1-1 is a vinyl monomer and/or oligomer that dissolves or expands the surface layer portion of the soluble unstretched, axially stretched film or at least the surface layer portion of the resin layer. There is no restriction as long as it does not cause stickiness and inhibit the polarizing properties of the polarizing film. Specific examples thereof are as follows.

- Functional vinyl monomers: for example methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, alkyl or cycloalkyl acrylate or methacrylate such as lacryl (meth)acrylate, vinyl acetate, vinyl propionate, (meth)acrylonitrile, styrene, vinyltoluene, (meth)acrylic acid, 2
-Hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate: Like rylate (meth)
Polyfunctional vinyl monomers such as hydroxy esters of acrylic acid: (meth)acrylic acids such as ethylene glycol, di(meth)acrylate, diethylene glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. -Functional oligomers such as ethylene glycol or propylene glycol diester, trimethylol propanetopanetate, (meth)acrylate, etc.: For example, polyester resin and (
Polyfunctional oligomers such as polyester mono(meth)acrylate obtained by reaction with meth)acrylic acid
:For example, polyethylene glycol di(meth)acrylate, epoxy(meth)acrylate obtained by the reaction of an epoxy resin and (meth)acrylic acid, urethane(meth)acrylate obtained by the reaction of a polyisocyanate compound and a hydroxyalkyl(meth)acrylate. ) acrylate, polyester di(meth)acrylate or polyester di(meth)acrylate obtained by the reaction of polyester resin and (meth)acrylic acid, etc., liquid materials whose main components are vinyl monomers and/or oligomers are is composed of one or more of the above vinyl monomers and/or oligomers, but its viscosity is preferably adjusted to a range of 0.01 to 100 voids in consideration of coating workability. Further, the polymerization initiator contained in either the soluble polyester resin film or the liquid material is one that is decomposed by redox anti-Ff5 as a polymerization accelerator to generate active radicals and polymerize the liquid material. For example, organic peroxides such as methyl ethyl ketone peroxide, benzoyl peroxide, lafuroyl peroxide, and cumene hydroperoxide are used.

The polymerization initiator is added to either the soluble polyester resin film, the soluble saturated polyester resin layer, or the liquid material containing the vinyl monomer and/or oligomer as a main component, from 0.01 to 10% by weight. H, preferably 0.
It is blended in a range of 1 to 4 servings.

If the amount is less than o or o1 weight percent, the polymerization of the liquid will be insufficient and the desired adhesive strength will not be obtained, and if it is more than 10% by weight, the polymerization will be excessive and the adhesive strength will decrease, which is not preferred.

Either the soluble polyester resin film or the liquid material, which does not contain a polymerization initiator, contains a polymerization accelerator that decomposes the polymerization initiator by redox reaction and facilitates generation of active radicals, such as , N-N-dimethylaniline, N-N-dimethylvalatoluidine, cobalt naphthenate, copper naphthenate, thiourea, acetylthiourea, condensate of n-butyraldehyde and aniline, etc., in an amount of 0.01 to IO% by weight, Preferably o, 1-4
It is blended within the range of heavy forging%. (If the amount is less than 1.01% by weight, there is no effect of adding the liquid material, and if it is more than 10% by weight, the adhesive strength may decrease and the optical properties may be adversely affected, which is not suitable.

In the manufacturing method of the present invention, a liquid material mainly composed of the vinyl monomer and/or oligomer is applied to the surface of the soluble polyester resin film or the soluble saturated polyester resin layer at a rate of 0.1
It is coated to a thickness of ~100 f/d, the film or layer surface is dissolved or swollen to become sticky, a polarizing film is superimposed on the coated sticky surface, and the liquid material is polymerized to form a soluble polyester resin film or an insoluble polyester resin film. To provide a polarizing plate having excellent durability and thermal stability by firmly adhering a resin film and a polarizing film.

Examples of the present invention will be shown below. The ``chu'' or ``chi'' in the text each refer to a unit of weight.

Example 1 Unstretched nf containing 1 part of benzoyl peroxide
A liquid material having the following composition was applied to one side of a polyethylene terephthalate film (thickness: 100μ#l), and the mixture was bonded to both sides of the iodine-based polarizing film described below for 24 hours at 20°C. A polarizing plate was obtained by reacting for a period of time.

2-Ethylhexyl acrylate 2-hydroxyethyl acrylate 10 parts Condensate of n-butyraldehyde and aniline 1 part [Iodine-based polarizing film] A polyvinyl alcohol-based film was mixed with an iodine concentration of 1%, a potassium iodide concentration of 2%, and boric acid. It was immersed in an aqueous solution adjusted to 4% and stretched 3 to 4 times at 50°C to produce a polarizing film (30 μm thick) with a transmittance of 41% and a degree of polarization of 92%.

Example 2 An unstretched soluble polyethylene terephthalate film containing 1 part of methyl ethyl ketone peroxide (thickness 1
00 μm), apply a liquid material having the following composition.C5f/? 〆) I-7, it was attached to both sides of the polarizing film of Example 1, and it was made to react at 20 degreeC for 24 hours, and the polarizing plate was obtained.

[Blend composition of liquid product]

Methyl methacrylate 80 parts Butyl acrylate 20 parts Zinc naphthenate
1 part Example 3 A liquid substance having the following composition was applied to one side of unstretched soluble polyethylene terephthalate (thickness 100μWI) containing 2 parts of zinc naphthenate (3F/door) to form the polarizing film of Example 1. Both surfaces were bonded and reacted at 20° C. for 36 hours to obtain a polarizing plate.

[Blend composition of liquid product]

50 parts of ethyl methacrylate 50 parts of mepur ethyl ketone peroxide 3 parts of Example
Apply a liquid material having the following composition on one side of C4.
f/d) I, was pasted on both sides of the polarizing film of Example 1 and reacted at 20° C. for 36 hours to obtain a polarizing plate.

[Blend composition of liquid product]

Ethyl acrylate 80 parts Methacrylic acid 15 parts Trimethylolpropane triacrylate 5 parts Benzoyl peroxide 3 parts Example 5 Cumene hydroperoxide was applied to one side of an insoluble polyethylene terephthalate film (thickness 75 μm) stretched only in the longitudinal direction. A soluble saturated polyester resin layer (20 μ#1) containing 2 parts was provided, and the following liquid material was applied to the surface of the saturated polyester resin layer (6 fields).
A polarizing plate was obtained by reacting for a period of time.

[Blend composition of liquid product]

Polyester dimethacrylate 40 parts (average molecular weight 420) Ethyl acrylate 60 parts Cobalt naphthenate 2 parts [Polarizing film] A polyvinyl alcohol film was immersed in an aqueous solution containing 0.1% by weight of hydrochloric acid as a dehydration catalyst, and was doubled in size. After stretching, the polyene is further stretched to 2.5 times and heat treated at 150° C. to form a polyene.

Next, the kernel film is immersed for 10 minutes in an aqueous solution (liquid temperature 30°C) containing 0.1 weight of a dichroic dye, and the dye is adsorbed and oriented and dried, resulting in a neutral hue. A polyene-dichroic dye-based polarizing film (thickness: 25 μm) having a transmittance of 43 inches and a polarization degree of 94 inches is obtained.

Example 6 An insoluble polyethylene terephthalate film stretched only in the vertical axis direction (1!j length 75 μm) σ) A soluble saturated polyester resin layer (20 μm) containing 2 parts of Nipenzoyl peroxide on one side was provided, and the saturated polyester resin Coat the following liquid material on the layer surface. T5C5f/Door) 1-1 Paste on both sides of the polarizing film of Example 5 and heat at 25℃ for 8
A polarizing plate was obtained by reacting for a period of time.

[Blend composition of liquid product]

Butyl acrylate 70 parts 40 parts 2-hydroxyethyl acrylate and 60 parts 2.4-
Tolylene diisocyanate and...reaction/proboscis
30 parts dimethylaniline
2 parts Example 7 On one side of an insoluble polyethylene terephthalate film (thickness 75 μm) stretched only in the longitudinal direction, a soluble saturated polyester resin layer (20μ #I) containing 2 parts of cobalt naphthenate was provided, Apply the following liquid #A to the surface of the saturated polyester resin layer (4fl/nf) l,
,, laminated on both sides of the polarizing film of Example 5 at 25°C
After reacting for 24 hours, a polarizing plate was obtained.

[Liquid material σ) composition]

Ethyl methacrylate 8 (1 part glycidyl methacrylate 20 parts methyl ethyl ketone peroxide 2 parts Example 8 Stretched in the vertical axis direction σ)! A soluble saturated polyester resin layer (20 μm) containing 2 parts of dimethyl-para-toluidine was provided on one side of an insoluble polyethylene terephthalate film (75 μIFI), and the following liquid material was applied to the surface of the saturated polyester resin layer (41/ n?)+,,
It was attached to both sides of the polarizing film of Example 5, and reacted at 30° C. for 24 hours to obtain a polarizing plate.

[Blend composition of liquid product]

Butyl acrylate) 50 parts 2-ethylhexyl acrylate 20B Methyl meccrylate) 30 parts Penzoyl peroxide 2 parts The test results of Examples 1 to 8 are shown in Table @1.

Table 1 Test method in Table 1 Adhesion: A cut is made at the interface between the polyester resin film and the polarizing film of the sample.1 Measure whether the two can be peeled off. Those that could not be peeled were determined to be impossible to peel, and those that peeled off were determined to be peeled.

Degree of polarization: Two samples cut at an angle of 45 degrees with respect to the polarization axis of the polarizing plate are superimposed to obtain the average parallel transmittance (YO
') and average orthogonal transmittance (YO0) were measured, and these transmittances were applied to the following formula.

As is clear from the above examples, the polarizing plate produced by the manufacturing method of the present invention was made of polyester resin film and i
The fact that it has excellent adhesion with optical films, durability and thermal stability is remarkable.

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

Claims (1)

[Claims] l) Polarizing film and soluble polyester #1lli
When adhering to the film, a liquid material containing a vinyl monomer and/or oligomer as a main component is used to melt or swell the surface layer of the resin 74 lum to make it sticky. one of them contains a polymerization initiator and the other one contains a polymerization accelerator, a liquid substance is present between the polarizing film and the resin film, and the liquid substance is polymerized by press-bonding the polarizing film and the resin film. A method for manufacturing a polarizing plate characterized by bonding a polarizing film and a resin film. 2) Polarizing film and soluble polyester resin layer '5c
When adhering the provided insoluble polyester resin frame 4p via the resin layer, the main component is a vinyl monomer and/or olibore that dissolves or swells at least the surface layer of the resin layer to make it sticky. Using a liquid material, either the resin layer or the liquid material contains a polymerization initiator and the other contains a polymerization accelerator, and the liquid material is present between the polarizing film and the resin layer. 1. A method for producing a polarizing plate, comprising: bonding the polarizing film and an insoluble polyester resin film by polymerizing the liquid material by pressing the polarizing film. 3) The method for producing a polarizing plate according to claim 2, wherein the insoluble polyester resin film is a uniaxially stretched polyester resin film obtained by stretching only in one direction.