JP2001350019A - Pressure-sensitive adhesive polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive polarizing plate, having a pressure-sensitive adhesive layer on a polarizing plate in which the residual stress generating in the polarizing plate can be decreased, the pressure-sensitive adhesive gives high yield and the amount of the pressure-sensitive adhesive protrude from the cut face is small. SOLUTION: In the pressure-sensitive adhesive polarizing plate prepared by applying a pressure-sensitive adhesive layer on a polarizing plate, the pressure-sensitive adhesive layer shows a creep of <=50 μm at 23 deg.C and >=0.04 slope for the linear expression, which is an approximation of the relation obtained by plotting temperature as abscissa and the value represented by (creep of the pressure-sensitive adhesive at each temperature)/(creep of the pressure-sensitive adhesive at 23 deg.C) as ordinate in the temperature range from 23 deg.C to 90 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive polarizing plate and a liquid crystal display. The adhesive polarizing plate forms a liquid crystal display device with less display unevenness.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) uses a liquid crystal panel in which a polarizing plate is bonded to a liquid crystal cell via an adhesive. In using such a liquid crystal display device,
Since the liquid crystal panel is lit by a backlight or the like, the polarizing plate is heated to 40 to 60 ° C. by heat generated from the backlight or the like. In such a warmed state, the polarizing plate expands linearly or attempts to change its dimensions due to evaporation of water.However, the polarizing plate is fixed to the liquid crystal cell with an adhesive and cannot change its size. Remain. Due to the residual stress of the polarizing plate, the stress is concentrated on the outside of the polarizing plate (for example, the transparent protective layer), causing optical distortion, and there is a problem that display unevenness occurs in the LCD.

In order to reduce the display unevenness of the LCD,
As the pressure-sensitive adhesive layer for fixing the polarizing plate to the liquid crystal cell, there is a method using a material having a large displacement (creep) and being easily deformed. According to this pressure-sensitive adhesive layer, the polarizing plate easily changes its dimensions, and the residual stress of the polarizing plate can be reduced,
LCD unevenness can be reduced.

However, when the pressure-sensitive adhesive layer has a large displacement (creep) and is easily deformed even at room temperature, if the pressure-sensitive adhesive layer is cut in a manufacturing process, the cut pressure-sensitive adhesive polarizing plate is cut. The adhesive protrudes from the end face of the adhesive polarizing plate, causing a portion having no adhesive layer on a part of the adhesive polarizing plate, or causing the protruding adhesive to stain the polarizing plate.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a pressure-sensitive adhesive polarizing plate comprising a polarizing plate and an adhesive layer provided thereon, which can reduce residual stress that can be generated in the polarizing plate and reduce the yield of the pressure-sensitive adhesive. It is an object of the present invention to provide an adhesive which has a small amount of pressure-sensitive adhesive protruding from a cut surface.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that the above object can be achieved by the following adhesive polarizing plate, and have completed the present invention. Was.

That is, the present invention relates to an adhesive polarizing plate comprising a polarizing plate provided with an adhesive layer, wherein the adhesive layer comprises
Creep in the following test at 50 ° C. is 50 μm or less,
In the temperature range from 23 ° C. to 90 ° C., the value represented by (creep of adhesive at each temperature) / (creep of adhesive at 23 ° C.) is plotted on the vertical axis against the temperature on the horizontal axis. When the plotted relationship is approximated by a linear expression, the gradient of the linear expression is 0.04 or more.

Test: Adhesive tape adhered to test plate with an area of 10
The adhesive tape was applied at a size of 10 mm × 10 mm, and the amount of displacement (creep) of the pressure-sensitive adhesive tape when a load of 200 g was applied for 1 hour was measured.

As described above, since the pressure-sensitive adhesive layer of the pressure-sensitive adhesive polarizing plate of the present invention has a small creep at room temperature, that is, 50 μm or less at 23 ° C., the yield of the pressure-sensitive adhesive at room temperature is good, and the pressure-sensitive adhesive polarizing plate is produced. Extrusion of the adhesive in the process can be prevented. From such a viewpoint, the creep at 23 ° C. is preferably 40 μm or less.

On the other hand, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive polarizing plate of the present invention comprises:
In the temperature range from 23 ° C. to 90 ° C., the temperature on the horizontal axis is plotted on the vertical axis (creep of the adhesive at each temperature) /
When the relationship plotting the value represented by (creep of the adhesive at 23 ° C.) is approximated by a linear expression, the gradient of the linear expression is 0.04 or more. That is,
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive polarizing plate of the present invention has such a property that the creep increases at a high temperature, thereby preventing display unevenness due to residual stress generated in the polarizing plate. From such a viewpoint, it is preferable that the gradient of the linear expression be 0.045 or more. If the slope of the linear equation is too large, it becomes excessively sensitive to temperature.
It is preferable that the inclination is 0.07 or less from the viewpoint of handleability during the manufacturing process.

The term "creep" as used in the present invention is a value measured by the above test. More specifically, as shown in FIG. 1, a pressure-sensitive adhesive layer (20 μm) is formed on a substrate (polarizing plate, 190 μm).
Adhesive tape (30 mm x 10 m)
m) to the test plate (SUS304 plate)
The amount of displacement (μm) of the adhesive tape when applied at 10 mm and a load of 200 g is applied for 1 hour.

The gradient of the linear expression can be, for example, a gradient in a linear expression derived from applying the plot value to the least squares method.

In the pressure-sensitive adhesive polarizing plate, it is preferable that a transparent protective layer is provided on the polarizing plate.

As described above, the pressure-sensitive adhesive polarizing plate of the present invention has a large creep of the pressure-sensitive adhesive at a high temperature, reduces stress concentration on the transparent protective layer provided on the polarizing plate, and causes uneven display of the LCD due to optical distortion. Generation can be suppressed.

Further, the present invention relates to a liquid crystal display device using a liquid crystal panel in which the adhesive polarizing plate is attached to at least one side of a liquid crystal cell.

The liquid crystal display device using the pressure-sensitive adhesive polarizing plate of the present invention has little display unevenness.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizer constituting the adhesive polarizing plate of the present invention is not particularly limited, and various types can be used. Examples of the polarizer include dichroic dyes such as iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene / vinyl acetate copolymer-based partially saponified films. A polarizing film such as a film obtained by adsorbing a substance and stretched, or a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride can be used. The thickness of the polarizer is not particularly limited.
It is generally about 80 μm.

On one or both sides of the polarizer, a transparent protective layer may be provided as a coating layer of a polymer or a laminate layer of a film for the purpose of water resistance or the like. As the transparent polymer or film material for forming the transparent protective layer, an appropriate transparent material can be used, but a material having excellent transparency, mechanical strength, heat stability, moisture barrier property and the like is preferably used. Although the thickness of the transparent protective layer is not particularly limited, it is generally about 10 to 300 μm.

Materials for forming the transparent protective layer include:
For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulosic polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin) Polymers, polycarbonate polymers and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Blends of polymers and the like are also examples of the polymer forming the transparent protective layer.

The pressure-sensitive adhesive used in the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive polarizing plate of the present invention has a creep at 23 ° C. of 50 μm or less as described above, and a gradient of the linear equation of 0.1. Those having a value of 04 or more can be used without particular limitation. Examples of the pressure-sensitive adhesive include various types such as a rubber-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive. Among these, an acrylic-based pressure-sensitive adhesive is preferable, and the weight-average molecular weight of the base polymer is 30.
It is preferably about 10,000 to 2.5 million.

The monomers used for the acrylic polymer which is the base polymer of the acrylic pressure-sensitive adhesive include various (meth) acrylates ｛(meth) acrylates are acrylates and / or methacrylates. The term “ester” refers to the term “(meth)” hereinafter. You can use｝. Specific examples of such (meth) acrylates include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Can be used alone or in combination. Further, a small amount of (meth) acrylic acid may be used in place of part of the (meth) acrylic acid ester in order to impart polarity to the obtained acrylic polymer. Further, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, or the like may be used in combination as a crosslinkable monomer. Further, if desired, other copolymerizable monomers such as vinyl acetate and styrene can be used in combination to such an extent that the adhesive properties of the (meth) acrylate polymer are not impaired.

As the base polymer of the rubber-based pressure-sensitive adhesive,
For example, natural rubber, isoprene rubber, styrene-butadiene rubber, recycled rubber, polyisobutylene rubber,
Further, styrene-isoprene-styrene-based rubber, styrene-butadiene-styrene-based rubber and the like can be mentioned. Examples of the base polymer of the silicone-based pressure-sensitive adhesive include dimethylpolysiloxane and diphenylpolysiloxane.

The pressure-sensitive adhesive can be realized, for example, by blending the compound (b) having a molecular weight of 100,000 or less with the base polymer (a). The ratio (weight ratio) of (a) :( b) is more preferably 90:10 to 20:80.

The compound (b) having a molecular weight of 100,000 or less has good compatibility when blended with the base polymer (a), is optically transparent, and has a glass transition point (Tg) of 3
Those at 0 ° C. or higher are preferred. For example, a polymer similar to the base polymer having a weight-average molecular weight of 100,000 or less and using many components having a high Tg as a monomer component may be used.

Further, the pressure-sensitive adhesive may contain a crosslinking agent. Examples of the crosslinking agent include a polyisocyanate compound, a polyamine compound, a melamine resin, a urea resin, and an epoxy resin. Further, the pressure-sensitive adhesive, if necessary, a tackifier, a plasticizer, a filler, an antioxidant, an ultraviolet absorber, and the like, and each may be appropriately used without departing from the object of the present invention. it can.

The method of forming the pressure-sensitive adhesive layer on the polarizing plate is not particularly limited, and a method of applying a pressure-sensitive adhesive (solution) to the polarizing plate and drying the same, and transferring the film using a release sheet provided with the pressure-sensitive adhesive layer. Method and the like.

The thickness of the pressure-sensitive adhesive layer (dry film thickness) is not particularly limited, but is preferably about 10 to 40 μm.

[0028]

EXAMPLES The present invention will be described in detail with reference to examples and the like, but the present invention is not limited to these examples.

EXAMPLE 80 parts by weight of butyl acrylate, 20 parts by weight of methyl acrylate, 1 part by weight of acrylate, and 0.5 part by weight of benzoyl peroxide were dissolved in ethyl acetate so as to have a monomer concentration of 40% by weight. Polymerized at 60 ° C for 8 hours and polymer solution 1
(Weight average molecular weight 1.2 million) was obtained.

Also, 40 parts by weight of butyl acrylate, 60 parts by weight of methyl methacrylate, 1 part by weight of acrylic acid, and 0.5 parts by weight of benzoyl peroxide are dissolved in toluene so that the monomer concentration becomes 20% by weight. Polymerization was performed at 8 ° C. for 8 hours to obtain a polymer solution 2 (weight average molecular weight: 50,000).

An adhesive syrup was prepared by mixing 70 parts by weight of the solid content of the polymer solution 1, 30 parts by weight of the solid content of the polymer solution 2 and 1 part by weight of an epoxy-based crosslinking agent (trade name: Tetrad C manufactured by Mitsubishi Chemical Corporation). .

An 80 μm-thick polyvinyl alcohol film stretched 5 times in an aqueous iodine solution and then dried (polarizer) is coated with an 80 μm-thick triacetyl cellulose film (transparent protective film) on both sides with an adhesive. And a polarizing plate having a transparent protective layer was obtained. On one surface of the polarizing plate having the transparent protective layer, the above-mentioned pressure-sensitive adhesive syrup was applied so that the thickness after drying became 25 μm, and release paper was adhered to obtain a pressure-sensitive adhesive polarizing plate.

COMPARATIVE EXAMPLE 1 100 parts by weight of butyl acrylate, 5 parts by weight of acrylate and 0.5 parts by weight of benzoyl peroxide were prepared at a monomer concentration of 60.
% By weight, and polymerized at 60 ° C. for 8 hours to obtain a polymer solution 3 (weight average molecular weight: 180%).
10,000). 1 part by weight of an isocyanate-based cross-linking agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 parts by weight of the solid content of Polymer 3 to obtain an adhesive syrup. Thereafter, an adhesive polarizing plate was obtained according to Example 1.

Comparative Example 2 100 parts by weight of isononyl acrylate, 0.1 part by weight of 2-hydroxyethyl acrylate and 0.5 part by weight of azobisisobutyronitrile were dissolved in ethyl acetate so that the monomer concentration became 60%. Thereafter, polymerization was performed at 60 ° C. for 8 hours to obtain a polymer solution 4 (weight average molecular weight: 1.6 million). 1 part by weight of an isocyanate-based cross-linking agent (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 parts by weight of the solid content of the polymer 4 to obtain an adhesive syrup. Thereafter, an adhesive polarizing plate was obtained according to Example 1.

Table 1 shows the results of the following evaluation of the pressure-sensitive adhesive syrup and the pressure-sensitive adhesive polarizing plate obtained in the above Examples and Comparative Examples.

(Measurement of Creep) The pressure-sensitive adhesive syrups prepared in Examples and Comparative Examples were measured at 23 ° C., 50 ° C., and 7 ° C.
Creep in an atmosphere of 0 ° C. and 90 ° C. was measured.
The measurement of creep is as described above.

(Slope of linear expression) The above-mentioned temperatures are plotted on the horizontal axis, and the value (α) of (creep of adhesive at each temperature) / (creep of adhesive at 23 ° C.) is plotted on the vertical axis. Was derived into a linear expression (least square method), and the slope of the linear expression was obtained.
FIG. 2 shows the plot values and straight lines represented by linear expressions in each example.

(Display unevenness) The pressure-sensitive adhesive polarizing plates obtained in Examples and Comparative Examples were cut at 45 ° with respect to the flow direction.
It was bonded to a 5-inch TFT-LCD panel. This was turned on to display black, and after standing for 1 hour, display unevenness was visually observed. The evaluation was performed in the following five stages from 1 to 5, and the larger the number, the smaller the unevenness. The evaluation was performed by five persons, and the average was evaluated excluding the highest point and the lowest point.

The evaluation criteria are as follows. 5: No unevenness was seen in a dark room. 4: Slight unevenness is seen in a dark room. 3: Unevenness is visible in a dark room, but is not visible under a 100 W fluorescent lamp. 2: The unevenness is slightly visible under a 100 W fluorescent lamp. 1: Unevenness is visible under a 100 W fluorescent lamp.

(Extrusion of Adhesive) The adhesive polarizing plates obtained in Examples and Comparative Examples were punched out with a Thompson, and the ends were observed with a microscope to confirm whether the adhesive had extruded.

[0041]

[Table 1] In the examples, the creep of the pressure-sensitive adhesive layer at room temperature is 50 μm or less, and the gradient in the above-mentioned linear equation is 0.04 or more, there is little display unevenness, and there is little protrusion of the pressure-sensitive adhesive. On the other hand, in Comparative Example 1, the pressure-sensitive adhesive layer had a creep at room temperature of 50 μm or less, and there was little protrusion of the pressure-sensitive adhesive. However, since the slope in the above-mentioned linear expression was smaller than 0.04, there were many display irregularities. In Comparative Example 2, creep at 23 ° C. was 50
Although it exceeds μm and the display unevenness is good, the slope in the above-mentioned linear expression is smaller than 0.04, and the protrusion of the adhesive is increased.

[Brief description of the drawings]

FIG. 1 is a front view and a side view showing a creep measurement test of an adhesive.

FIG. 2 is a diagram in which pressure-sensitive adhesives of Examples and Comparative Examples are approximated by a linear expression of the present invention.

Continuing from the front page (72) Inventor Nei Takahashi 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Co., Ltd. F term in the company (reference) 2H049 BA02 BA27 BB19 BB33 BB51 BC03 BC14 BC22 2H091 FA08X FA08Z FB02 FB13 FC07 FC29 FC30 FD06 FD14 FD21 GA13 HA07 LA02 LA04 LA11 LA12

Claims (3)

[Claims] 1. A pressure-sensitive adhesive polarizing plate having a pressure-sensitive adhesive layer provided on a polarizing plate, wherein the pressure-sensitive adhesive layer has a creep of 50 μm or less in the following test at 23 ° C. and a temperature of 23 to 9 ° C.
In the temperature range up to 0 ° C., the relationship between the temperature on the horizontal axis and the value represented by (creep of the adhesive at each temperature) / (creep of the adhesive at 23 ° C.) is plotted on the vertical axis. When approximated by the following equation, the gradient of the linear equation is 0.04 or more. Test: An adhesive tape was stuck on a test plate with an adhesive area of 10 mm x 10 mm,
The displacement (creep) of the pressure-sensitive adhesive tape when a load of 200 g was applied for one hour was measured. 2. The pressure-sensitive adhesive polarizing plate according to claim 1, wherein a transparent protective layer is provided on the polarizing plate. 3. The adhesive polarizing plate according to claim 1 or 2,
A liquid crystal display device using a liquid crystal panel attached to at least one side of a liquid crystal cell.