KR20130074559A - Liquid crystal display device without nonuniform display - Google Patents

Abstract

PURPOSE: A liquid crystal display without display unevenness is provided to reduce bending of a liquid crystal panel even when the liquid crystal display is put under moist heat environment. CONSTITUTION: A front polarizing plate (20) is laminated on the visual recognition side of a liquid crystal cell (10) through an adhesive layer (51). A rear polarizing plate (30) is laminated on the opposite side of the visual recognition side through an adhesive layer (52). A backlight unit (70) is arranged in the outside of the rear polarizing plate. The front polarizing plate and rear polarizing plate respectively include a polarizing film (21,31) and transparent protection films (23,24,33,34). The ratio between water evaporation speed of the front polarizing plate with the adhesive layer and the rear polarizing plate with the adhesive layer is in a range of 0 to 1.

Description

Liquid crystal display without display stains {LIQUID CRYSTAL DISPLAY DEVICE WITHOUT NONUNIFORM DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having less leakage of light generated at the periphery of a screen even after being placed in a moist heat environment, a small difference in luminance of the panel surface, and less display unevenness.

Recently, liquid crystal displays are rapidly spreading as information display devices such as mobile phones, portable information terminals, computer monitors, TVs, etc., using low power consumption, operating at low voltage, and using light and thin features. With the development of liquid crystal technology, various modes of liquid crystal displays have been proposed, and problems of liquid crystal displays such as response speed, contrast, and narrow viewing angle have been solved. However, since the liquid crystal display uses a polarizing plate, when the liquid is placed in a moist heat environment during transportation and the polarizing plate is absorbed, the heat generated when the backlight is turned on causes moisture to evaporate and warpage occurs in the liquid crystal panel. It is a problem that display unevenness arises in a liquid crystal panel by the curvature of such a liquid crystal panel.

Japanese Patent Application Laid-Open No. 2007-292966 (Patent Document 1) proposes to improve the warpage of a liquid crystal panel under high temperature and high humidity by adjusting the dimensional change rate of a polarizing plate bonded to both surfaces of a liquid crystal cell. Moreover, Unexamined-Japanese-Patent No. 2003-50313 (patent document 2) is proposed to improve the curvature of a liquid crystal panel in a wet heat environment using the polarizing plate in which the adhesive layer which shows a specific creep characteristic was formed. However, such improvement requires pretreatment such as heat treatment to the polarizing plate, and in some cases, improvement in display unevenness due to warpage of the liquid crystal panel after being placed in a moist heat environment is insufficient.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2007-292966

[Patent Document 2] Japanese Patent Application Laid-Open No. 2003-050313

An object of the present invention is to provide a liquid crystal display device having less warpage and less display unevenness even after being placed in a moist heat environment. The present inventors have made intensive studies to achieve such an object. As a result, when the backlight is turned on after being put under a moist heat environment, the inventors have found that the angle of the backlight is maintained between the front polarizer positioned on the viewing side of the liquid crystal cell and the rear polarizer positioned on the opposite side. It was found that the water evaporation rate of the polarizing plate was adjusted to control the warpage of the liquid crystal panel to be effective for improving display unevenness. The present invention is based on this knowledge.

According to the present invention, a liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween, a front side polarizing plate laminated through a pressure-sensitive adhesive layer on a viewing side of the liquid crystal cell, and an adhesive on a side opposite to the viewing side of the liquid crystal cell A back side polarizing plate laminated through a layer, and a backlight unit disposed outside the back side polarizing plate, wherein the front side polarizing plate and the back side polarizing plate each have a polarizing film and a transparent protective film disposed on both sides thereof, and The ratio of the water evaporation rate (V _f ) of the front side polarizing plate with the pressure-sensitive adhesive layer and the water evaporation rate (V _r ) of the back side polarizing plate with the pressure-sensitive adhesive layer, V _f / V _r is in the range of more than 0 and less than 1 A liquid crystal display device is provided.

In this liquid crystal display device, it is preferable that the transparent protective film located in the side far from the liquid crystal cell of a front side polarizing plate is comprised with polypropylene resin, polyethylene terephthalate resin, or acrylic resin. Moreover, it is preferable to comprise the transparent protective film located in the side far from the liquid crystal cell of a back side polarizing plate with a cellulose resin.

In this liquid crystal display device, the thickness direction retardation of the transparent protective film located in each liquid crystal cell side of a front side polarizing plate and a back side polarizing plate is in the range of -10-+10 nm. In a 2nd preferable aspect, one of the transparent protective films located in each liquid crystal cell side of a front side polarizing plate and a back side polarizing plate has thickness direction retardation in the range of -10- + 10 nm, and the other is an in-plane reta Dation is in the range of 100 to 300 nm, when the refractive index in the slow axis direction in the film plane is n _x , the refractive index in the fast axis direction in the film plane is n _y , and the refractive index in the film thickness direction is n _z . _The Nz coefficient defined by _x -n _z ) / (n _x -n _y ) is in the range of 0.1 to 0.7.

Moreover, the 3rd preferable aspect of the transparent protective film located in each liquid crystal cell side of a front side polarizing plate and a back side polarizing plate has a thickness direction retardation in the range of -10-+10 nm, and the other Located in the polarizing film side which comprises a polarizing plate, and is located in the adhesive layer side rather than the 1st retardation film which consists of polyolefin resin, and this 1st retardation film, The core layer which consists of styrene resin, and the rubber particle laminated | stacked on both surfaces of the core layer It is a laminated body of the 2nd phase difference film which has a 3-layered structure which consists of a skin layer which consists of a (meth) acrylic-type resin composition containing the. In this third preferred aspect, the first retardation film has an in-plane retardation in the range of 30 to 150 nm, the Nz coefficient defined in the above formula is in the range of more than 1 and less than 2, and the second retardation film has in-plane retardation. It is more preferable that it exists in the range of 20-120 nm, and the Nz coefficient defined by the said formula exists in the range more than -2 and less than -0.5.

Moreover, in such a liquid crystal display device, one preferable aspect from the viewpoint of adhesion of the polarizing film which comprises a polarizing plate and the transparent protective film arrange | positioned at both surfaces is at least one of a front side polarizing plate and a back side polarizing plate, and a polarizing film and its both surfaces. The transparent protective film arrange | positioned at is bonded through the water-based adhesive containing a polyvinyl alcohol-type resin and a water-soluble epoxy resin. Moreover, from a viewpoint of adhesion of the polarizing film which comprises the same polarizing plate, and the transparent protective film arrange | positioned at both surfaces, at least 1 of a front side polarizing plate and a back side polarizing plate is a polarizing film and the transparent protective film arrange | positioned at both surfaces Adhesive bonding is performed through the curable adhesive composition containing the epoxy compound which hardens | cures by irradiation of this active energy ray. In the latter form, the epoxy compound which is cured by irradiation of active energy rays preferably contains an epoxy compound having at least one epoxy group in the molecule bonded to an alicyclic ring.

According to the present invention, it is possible to provide a liquid crystal display device having a small warpage of the liquid crystal panel even after being placed in a moist heat environment, and having less light leakage of the light and luminance unevenness on the surface, that is, less display unevenness.

1 is a schematic cross-sectional view showing the layer structure of a liquid crystal display device according to the present invention.
It is a cross-sectional schematic diagram which shows the laminated constitution example of one preferable form of the liquid crystal display device which concerns on this invention.
3: is a figure which shows typically the state which measures the curvature amount of a liquid crystal panel in an Example, (A) is a top view, (B) is a side view.

Referring to FIG. 1, the liquid crystal display device of the present invention includes a liquid crystal cell 10, a front side polarizing plate 20 laminated on the viewing side of the liquid crystal cell via an adhesive layer 51, and a viewing side of the liquid crystal cell. The back side polarizing plate 30 laminated | stacked through the adhesive layer 52 on the opposite side, and the backlight unit 70 arrange | positioned outside the back side polarizing plate (namely, the opposite side to the liquid crystal cell 10) are provided. Liquid crystal cell 10, the front side polarizing plate 20 laminated through the pressure-sensitive adhesive layer 51 on the viewing side of the liquid crystal cell, the back side polarizing plate 30 laminated through the pressure-sensitive adhesive layer 52 on the opposite side of the liquid crystal cell The panel 60 is formed.

The front polarizing plate 20 disposed on the viewing side of the liquid crystal cell 10 has a polarizing film 21 and transparent protective films 23 and 24 laminated on both surfaces thereof with an adhesive (not shown). Similarly, the back side polarizing plate 30 disposed on the side opposite to the viewing side of the liquid crystal cell 10 (that is, the backlight unit 70 side) is similarly laminated on the polarizing film 31 and both surfaces thereof through an adhesive (not shown). Transparent protective films 33 and 34.

The liquid crystal display device is constructed by combining the liquid crystal panel 60 and the backlight unit 70. However, when the liquid crystal display device is placed in a moist heat environment and the backlight is turned on, the moisture of the absorbing polarizing plate evaporates and the polarizing plate shrinks. Warping occurs in the panel 60. At this time, a portion of the liquid crystal panel 60 may abnormally approach the backlight unit 70 or, in extreme cases, may come into contact with each other to generate display unevenness. In addition, although the liquid crystal panel 60 is fixed with a case or a metal frame so as not to fall to the viewer side, when the backlight is turned on after the liquid crystal display device is placed in a moist heat environment, warpage occurs in the liquid crystal panel 60, and the liquid crystal panel 60 Some of the parts could come into contact with the case or the metal frame to fix it, causing marking stains.

Therefore, in the present invention, when the water evaporation rate of the front side polarizing plate 20 with the pressure-sensitive adhesive layer 51 is V _f , and the water evaporation rate of the back side polarizing plate 30 with the pressure-sensitive adhesive layer 52 is V _r . , So that the ratio V _f / V _{r of both} is in the range of more than 0 and less than 1. In addition, in this specification, the temperature at the time of measuring the moisture evaporation rate shall be 50 degreeC fundamentally. The relationship between the water evaporation rate V _f of the front side polarizing plate 20 and the water evaporation rate V _r of the back side polarizing plate 30 corresponds to the following equation (1).

0 <V _f / V _r <1 (1)

Here, the water evaporation rate is measured as follows. That is, the polarizing plate on which the pressure-sensitive adhesive layer is formed is cut in advance to a predetermined size (the area is called Am ² ), and is bonded to the glass plate having an area slightly larger than that so that the polarizing plate does not deviate from the glass plate on the pressure-sensitive adhesive layer side. In this state, moisture is absorbed under predetermined conditions and the weight W ₁ (unit: g) is measured. After leaving this for 1 hour in an environment of a temperature of 50 ° C. and a relative humidity of 0%, the weight W ₂ (unit: g) immediately after taking out to room temperature and taking out is measured. From these values, the water evaporation rate C (g / m ² · hr) is obtained by the following equation (2).

C = (W ₁ -W ₂ ) / A (2)

The conditions at the time of moisture absorption to determine the moisture evaporation rate are arbitrary, but, for example, a treatment that is allowed to stand for 96 hours in an environment having a temperature of 40 ° C. and a relative humidity of 95% can be employed as in the examples described later.

Therefore, the water evaporation rate V _f of the front side polarizing plate 20 is set to a smaller value than the water evaporation rate V _r of the back side polarizing plate 30, and the back side polarizing plate 30 is moisturized compared to the front side polarizing plate 20. It is important to configure that the evaporation rate is large. Thereby, the curvature of the liquid crystal panel 60 can be suppressed even after a liquid crystal display device is placed in a moist heat environment, and it was discovered that the display unevenness was not recognized and the liquid crystal display device excellent in display quality was obtained.

Hereinafter, each member which comprises the liquid crystal display device of this invention is demonstrated in detail, referring reference numeral shown in FIG.

[Liquid crystal cell]

The liquid crystal cell 10 has two cell substrates 11 and 12 and a liquid crystal layer 15 sandwiched between those substrates. The cell substrates 11 and 12 are generally made of glass, but may be a plastic substrate. In addition, in the liquid crystal display device of the present invention, the liquid crystal cell 10 itself can be configured with various ones employed in this field.

[Polarizing Film]

The polarizing films 21 and 31 which comprise the front side polarizing plate 20 and the back side polarizing plate 30 are the process of uniaxially stretching a polyvinyl alcohol-type resin film, and dyeing a polyvinyl alcohol-type resin film with a dichroic dye. It is manufactured through the process of adsorb | sucking a dichroic dye, the process of processing the polyvinyl alcohol-type resin film to which the dichroic dye was adsorbed by boric acid aqueous solution, and the process of washing with water after the process by aqueous boric acid solution.

Polyvinyl alcohol-type resin can be manufactured by saponifying polyvinyl acetate type resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and other monomers copolymerizable thereto, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamide which has an ammonium group, etc. are mentioned, for example.

The saponification degree of polyvinyl alcohol-type resin is about 85-100 mol% normally, Preferably it is 98 mol% or more. The polyvinyl alcohol-based resin may be modified. For example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method of forming a polyvinyl alcohol-type resin into a film is not specifically limited, It can form into a film by a well-known method. The thickness of the polyvinyl alcohol-based resin master film is, for example, about 10 to 150 μm, preferably about 10 to 100 μm.

Uniaxial stretching of a polyvinyl alcohol-type resin film can be performed before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or may be performed during boric acid treatment. Of course, you may uniaxially stretch in several steps shown here. As uniaxial stretching, the method of extending | stretching uniaxially between the rolls from which a circumferential speed differs, the method of extending | stretching uniaxially using a heat roll, etc. can be employ | adopted. In addition, uniaxial stretching may be performed by dry extending | stretching extending | stretching in air | atmosphere, and may be performed by wet extending | stretching extending | stretching in the state which expanded the polyvinyl alcohol-type resin film using solvents, such as water. The draw ratio is usually about 3 to 8 times.

Dyeing with the dichroic dye of a polyvinyl alcohol-type resin film can be performed by the method of immersing a polyvinyl alcohol-type resin film in the aqueous solution containing a dichroic dye, for example. Specifically as an dichroic dye, iodine or a dichroic organic dye is used. Moreover, it is preferable to perform the process which swells by immersing in a polyvinyl alcohol-type resin film in water before a dyeing process.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally. The iodine content in this solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is about 20-40 degreeC normally. The immersion time (dyeing time) in the aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when using a dichroic organic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing water-soluble dichroic organic dye is employ | adopted normally. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The dye aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dichroic organic dye aqueous solution used for dyeing is about 20-80 degreeC normally. Moreover, the immersion time (dyeing time) in aqueous solution is about 10 to 1,800 second normally.

The boric acid treatment after dyeing with a dichroic dye can be performed by the method of immersing the dyed polyvinyl alcohol-type resin film in boric acid containing aqueous solution. The content of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When using iodine as a dichroic dye, it is preferable that this boric acid containing aqueous solution contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. Immersion time in boric acid containing aqueous solution is about 60 to 1,200 second normally, Preferably it is 150 to 600 second, More preferably, it is 200 to 400 second. The temperature of the boric acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50-85 degreeC, More preferably, it is 60-80 degreeC.

After the boric acid treatment, the polyvinyl alcohol-based resin film is usually washed with water. A water washing process can be made into the method of immersing the polyvinyl alcohol-type resin film treated with boric acid, for example in water. The temperature of the water of a water washing process is about 5-40 degreeC normally. In addition, immersion time is about 1 to 120 second normally.

After washing with water, it is dried to obtain a polarizing film. The drying treatment can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is reduced to the practical level. The moisture content is about 5 to 20 weight% normally, Preferably it is 8 to 15 weight%. If the moisture content is less than 5% by weight, the effectiveness of the polarizing film may be lost, resulting in damage or destruction after drying. In addition, when the moisture content exceeds 20% by weight, thermal stability tends to be insufficient.

As described above, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be produced. The obtained polarizing film can make the thickness about 5-40 micrometers, for example.

[View-side transparent protective film of front side polarizing plate]

The transparent protective film 23 located on the side far from the liquid crystal cell 10 of the front side polarizing plate 20, that is, the viewing side, may suitably be composed of polypropylene resin, polyethylene terephthalate resin or acrylic resin. . Such resin films include a film formed by melt extrusion of raw material resin, a uniaxially stretched film obtained by transverse stretching after film formation, a biaxially stretched film obtained by longitudinal stretching after film formation, and then transverse stretching.

<Polypropylene resin film>

Polypropylene resin is a linear olefin resin in which at least 80% by weight of the repeating unit obtained by polymerizing a linear olefin monomer whose main component is propylene using a polymerization catalyst is composed of propylene. The polypropylene resin may be a propylene homopolymer, or may be a copolymer obtained by copolymerizing a propylene as a main copolymerizable comonomer in a proportion of 1 to 20% by weight, preferably 3 to 10% by weight.

In the case of a propylene-based copolymer, the comonomer copolymerizable with propylene is preferably ethylene or an α-olefin including 1-butene and 1-hexene. Especially, since resin which is comparatively excellent in transparency is obtained, it is preferable to copolymerize ethylene in the ratio of 1 to 20 weight%, Preferably it is the ratio of 3 to 10 weight%. The effect of improving transparency by making ethylene copolymerization ratio 1 weight% or more appears. On the other hand, when the ratio exceeds 20% by weight, the melting point of the resin is low, the heat resistance required for the transparent protective film may be impaired.

The polypropylene resin preferably has a content of a component dissolved in xylene at 20 ° C., that is, a cold xylene soluble (CXS) component of 1 wt% or less, particularly 0.5 wt% or less. Propylene homopolymers are easy to reduce the CXS component, so propylene homopolymers having a CXS component of 1 wt% or less, in particular 0.5 wt% or less, are also suitable polypropylene resins.

Polypropylene resin can obtain a commercial item easily. Examples of commercially available products include "Prime Polyprop" sold by Prime Polymer under each trade name, "Novatech" and "Wintech" sold by Nippon Polypro, and Sumitomo Chemical Co., Ltd. There are "Sumitomonoburen" sold and "San Aroma" sold by San Aroma Co., Ltd., etc.

<Polyethylene terephthalate resin film>

Polyethylene terephthalate-based resin means a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and other dicarboxylic acid components or diol components may be copolymerized. As other dicarboxylic acid components, for example, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 1, 4- dicarboxy cyclohexane etc. are mentioned. As another diol component, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane diol, ethylene oxide addition product of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. are mentioned, for example. .

These other dicarboxylic acid components and diol components can also be used in combination of 2 or more type as needed. It is also possible to use hydroxy carboxylic acids such as p-hydroxy benzoic acid and p-β-hydroxy ethoxy benzoic acid in combination. As another copolymerization component, a dicarboxylic acid component or a diol component containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used.

As a method for producing a polyethylene terephthalate resin, a method of directly polycondensing terephthalic acid and ethylene glycol (and other dicarboxylic acid or other diol if necessary), a dialkyl ester of terephthalic acid and ethylene glycol (and other dicarboxylic acid as necessary) The method of polycondensation after the transesterification of a dialkyl ester or other diol), and the method of polycondensing the ethylene glycol ester (and other diol ester as needed) of terephthalic acid (and other dicarboxylic acid as needed) can be adopted.

For each polymerization reaction, a polymerization catalyst composed of an antimony-based, titanium-based, germanium-based or aluminum-based compound, or a polymerization catalyst composed of a composite compound thereof can be used.

What is necessary is just to select these polymerization reaction conditions suitably according to the monomer to be used, a catalyst, a reaction apparatus, and desired resin physical properties. For example, the reaction temperature is usually in the range of about 150 to 300 ° C, preferably in the range of about 200 to 300 ° C, and more preferably in the range of about 260 to 300 ° C. The pressure is usually in the range of about 2.7 Pa at atmospheric pressure, but in the latter half of the reaction, the pressure is preferably reduced. The polymerization reaction proceeds by stirring under such high temperature and high pressure conditions to devolatilize desorption reaction products such as alcohol and water.

Moreover, the polymerization apparatus may be completed by one reaction tank, and may connect several reactors. In the latter case, depending on the degree of polymerization, the reactant is polymerized while being transferred between the reaction tanks. Moreover, the method of devolatilizing while heat-kneading can be employ | adopted by equipping a horizontal reaction apparatus in the latter stage of superposition | polymerization.

After the end of the polymerization, the resin is taken out of the reaction tank or the horizontal reactor in the molten state, cooled with a cooling drum or a cooling belt, extruded in the form of crushed flakes or knots introduced into the extruder, and then obtained in the form of cut pellets. have.

If necessary, the solid phase polymerization may be carried out to improve the molecular weight and reduce the low molecular weight component. Although the low molecular weight component obtained by being contained in polyethylene terephthalate type resin contains a cyclic trimer component etc., especially content in resin of a cyclic trimer component is preferably 5,000 ppm or less, and more preferably 3,000 ppm or less. If the cyclic trimer component exceeds 5000 ppm in the resin, it may adversely affect the optical properties of the film.

The molecular weight of the polyethylene terephthalate resin is usually in the range of 0.45 to 1 dL / g, preferably 0.5, when the resin is dissolved in a mixed solvent having a weight ratio of 50/50 of phenol and tetrachloroethane and is represented by an intrinsic viscosity measured at 30 ° C. ˜1 dL / g, more preferably 0.52 to 0.8 dL / g. When this intrinsic viscosity is less than 0.45 dL / g, productivity may fall at the time of film manufacture, or the mechanical strength of a film may fall. Moreover, when this intrinsic viscosity exceeds 1 dL / g, melt extrusion stability of a polymer can be reduced in film manufacture.

Polyethylene terephthalate resin may contain an additive as needed. Examples of the additive include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance improvers and the like. It is preferable that the addition amount is a range which does not adversely affect optical physical property.

Polyethylene terephthalate-based resins are used in the form of pellets assembled by an extruder, for the purpose of blending these additives, for film molding described below. The size or shape of the pellets can be, for example, cylindrical, spherical or flat spherical, both in height and diameter of 5 mm or less.

The polyethylene terephthalate resin thus obtained can be formed into a film having high transparent and uniform mechanical strength by molding into a film shape and stretching. The manufacturing method can employ | adopt the following method, for example.

First, a pellet made of dried polyethylene terephthalate resin is supplied to a melt extrusion apparatus and heated and melted above the melting point. The molten resin is then extruded from the die and solidified rapidly to a temperature below the glass transition temperature on a rotary cooling drum to obtain a substantially unstretched film in a substantially amorphous state. This melting temperature is determined depending on the melting point and the extruder of the polyethylene terephthalate resin to be used, and is usually about 250 to 350 ° C.

Moreover, in order to improve the planarity of a film, it is preferable to improve the adhesiveness of a film and a rotary cooling drum, and the electrostatic application adhesion method or the liquid coating adhesion method is used preferably. Here, the electrostatically applied adhesion method spreads the linear electrodes on the upper surface side of the film in a direction orthogonal to the flow of the film, and applies static electricity to the film by applying a DC voltage of, for example, about 5 to 10 kV, thereby rotating cooling drums. It is a method of improving the adhesive force of a film. In addition, the liquid coating adhesion method is a method of improving the adhesiveness of a rotating cooling drum and a film by apply | coating a liquid uniformly to the whole or part (for example, only the part which contacts both ends of a film) on the surface of a rotating cooling drum. You may use both together as needed.

Polyethylene terephthalate-type resin to be used may mix 2 or more types of resin from which resin structure and composition differ as needed. For example, a pellet in which a granular filler, an ultraviolet absorber, an antistatic agent, etc. are mix | blended with an antiblocking agent, and a non-blended pellet can also be mixed and used.

In addition, a single layer may be sufficient as the film extruded and a multilayer film of two or more layers may be sufficient as needed. For example, a pellet composed of granulated filler and a non-mixed pellet are prepared as an anti-blocking agent, and each of them is fed into the same die by a different extruder, and a film composed of two or three layers of filler compounded resin / unmixed resin / filler compounded resin. May be extruded.

The melt-extruded polyethylene terephthalate resin film is usually longitudinally stretched in the extrusion direction at a temperature above the glass transition temperature. Longitudinal stretching temperature is 70-150 degreeC normally, Preferably it is the range of 80-130 degreeC, More preferably, it is the range of 90-120 degreeC. Moreover, a longitudinal stretch magnification is 1.1-6 times normally, Preferably it is 2-5.5 times. This is because when the draw ratio is less than 1.1 times, the mechanical strength of the stretched polyethylene terephthalate film tends to be insufficient. In addition, when this draw ratio exceeds 6 times, the lateral strength may actually be insufficient. This extending | stretching may be complete | finished once, and may be divided into multiple times as needed. Even when extending | stretching several times, it is preferable to make total draw ratio into the said range.

The longitudinally stretched film thus obtained can be subjected to heat treatment thereafter. Subsequently, a relaxation process may be performed as needed. In this case, heat processing temperature is 150-250 degreeC normally, Preferably it is 180-245 degreeC, More preferably, it is 200-230 degreeC. The heat treatment time is usually 1 to 600 seconds, preferably 1 to 300 seconds, more preferably 1 to 60 seconds. Subsequently, when performing a relaxation process, temperature is 90-200 degreeC normally, Preferably it is 120-180 degreeC. The amount of relaxation is usually 0.1 to 20%, preferably 2 to 5%. It is more preferable that the relaxation treatment temperature and the relaxation amount are set such that the thermal contraction rate is 2% or less at 150 ° C of the polyethylene terephthalate resin film which has been relaxed.

It is preferable that the polyethylene terephthalate resin film is laterally stretched by a tenter after the longitudinal stretching treatment, or further subjected to further heat treatment if necessary, or further subjected to further relaxation treatment. When transverse stretching is carried out, the temperature is usually in the range of 70 to 150 ° C, preferably 80 to 130 ° C, more preferably in the range of 90 to 120 ° C. Moreover, a lateral stretch magnification is 1.1-6 times normally, Preferably it is 2-5.5 times. When the draw ratio of lateral stretch is less than 1.1 times, sufficient improvement of the film strength by orientation may not be desired, while the draw ratio exceeding 6 times is unrealistic in manufacturing technology.

After lateral stretching, heat treatment and relaxation treatment may be performed as necessary. The heat treatment temperature at this time is 150-250 degreeC normally, Preferably it is 180-245 degreeC, More preferably, it is 200-230 degreeC. The heat treatment time is usually 1 to 600 seconds, preferably 1 to 300 seconds, more preferably 1 to 60 seconds. Moreover, when performing a relaxation process, temperature is 100-230 degreeC normally, Preferably it is 110-210 degreeC, More preferably, it is 120-180 degreeC. The relaxation amount is usually 0.1 to 20%, preferably 1 to 10%, more preferably 2 to 5%. It is more preferable that the relaxation treatment temperature and the relaxation amount are set such that the thermal contraction rate is 2% or less at 150 ° C. of the relaxed polyethylene terephthalate resin film.

When the stretching treatment temperature exceeds 150 ° C. in uniaxial stretching and biaxial stretching, optical performance may be deteriorated because deterioration occurs or crystallization proceeds in the polyethylene terephthalate resin. On the other hand, when an extending | stretching process temperature is less than 70 degreeC, excessive stress may be extended or extending | stretching itself may be impossible.

Moreover, about uniaxial stretching and biaxial stretching processes, it is preferable to perform reheat processing or a relaxation process in order to alleviate the distortion of the orientation main axis which is represented by the bowing after lateral stretching. Although the maximum value of the distortion with respect to the extending | stretching direction of the orientation main axis by bowing is generally 45 degrees or less, it is preferable to relax to 30 degrees or less, and it is more preferable to set it as 15 degrees or less. If the maximum value of the distortion of the orientation major axis exceeds 45 °, the optical properties may become nonuniform between the sheets when the polarizing plates are formed and sheeted in the next step.

In addition, a extending | stretching direction means the big direction of the draw ratio among longitudinal stretch and lateral stretch here. In the biaxial stretching of the polyethylene terephthalate resin film, since the lateral stretching ratio is usually slightly larger than the longitudinal stretching ratio, the stretching direction in this case refers to the direction orthogonal to the long axis direction of the film, that is, the width direction. Since uniaxial stretching is usually extended in the transverse direction, the stretching direction in this case likewise refers to the direction orthogonal to the long axis direction of the film, that is, the width direction.

The orientation main axis means the molecular orientation direction at any point on the stretched polyethylene terephthalate resin film. The distortion with respect to the stretching direction of the orientation major axis refers to the angle between the orientation major axis and the stretching direction. In addition, the distortion maximum value of an orientation main axis means the maximum value of a value in the direction orthogonal to a long axis direction.

The said orientation main axis is measured using the retardation film material inspection apparatus "RETS" (brand name) sold by Otsuka Electronics Co., Ltd., or the molecular orientation meter "MOA" (brand name) sold by Prince Instrument Co., Ltd., for example. can do.

The stretched polyethylene terephthalate resin film can be easily obtained commercially available products, for example, "Dia foil", "Host Star" and "Fusion", Teijin sold by Mitsubishi Resin Co., Ltd. under the trade names. "Teijin Tetron Film", "Mernex", "Miler" and "Teplex" sold by Dupont Film Co., Ltd., "Oriental ester film" sold by Dongyang Spinning Co., Ltd. Aspect Films "Cosmo Shine" and "Crispa", "Rumira" sold by Toray Film Processing Co., Ltd. "Enbron" and "Enbret" sold by Unichika Co., Ltd. "Skyul" sold by the company, "Kohir" sold by Co., Ltd., "Songtong polyester film" sold by Seotong Co., Ltd., "Tapoly poly sold by Futamura Chemical Co., Ltd. Ester film "and the like. Especially in a polyethylene terephthalate resin film, a biaxially stretched product is used preferably.

<Acrylic resin film>

Acrylic resin is generally a polymer mainly composed of methyl methacrylate, and is also called methyl methacrylate resin. In this resin, the methyl methacrylate unit is usually 50% by weight or more, preferably 70% by weight or more, and may be 100% by weight. A polymer having 100% by weight of methyl methacrylate units is a methyl methacrylate homopolymer obtained by polymerizing methyl methacrylate alone.

This acrylic resin can be normally obtained by superposing | polymerizing the monofunctional monomer which has methyl methacrylate as a main component in the coexistence of a radical polymerization initiator and a chain transfer agent. Moreover, there exist some which copolymerized a small amount of polyfunctional monomer as needed.

As a monofunctional monomer obtained by copolymerization with methyl methacrylate, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate And methacrylic acid esters other than methyl methacrylate such as 2-hydroxyethyl methacrylic acid; Acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate; Hydroxyalkyl acrylates such as methyl 2- (hydroxymethyl) acrylate, methyl 3- (hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate and butyl 2- (hydroxymethyl) acrylate; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; Styrenes such as styrene, vinyltoluene and α-methylstyrene; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; And unsaturated imides such as phenyl maleimide and cyclohexyl maleimide. These monomers may be used independently, respectively and may be used in combination of 2 or more type.

When copolymerizing a polyfunctional monomer, examples thereof include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, Esterification of both terminal hydroxyl groups of ethylene glycol or its oligomers such as nonaethylene glycol di (meth) late and tetradecaethylene glycol di (meth) acrylate with acrylic acid or methacrylic acid; Esterification of both terminal hydroxyl groups of propylene glycol or its oligomers with acrylic acid or methacrylic acid; Esterifying hydroxyl groups of dihydric alcohols such as neopentyl glycol di (meth) acrylate, hexanedioldi (meth) acrylate and butanedioldi (meth) acrylate with acrylic acid or methacrylic acid; Esterifying both terminal hydroxyl groups of bisphenol A, alkylene oxide adducts of bisphenol A or their halogen substituents with acrylic acid or methacrylic acid; Esters of polyhydric alcohols such as trimethylol propane and pentathitol with acrylic acid or methacrylic acid; Ring-opening addition of the epoxy group of glycidyl acrylate or glycidyl methacrylate to the terminal hydroxyl group of the same polyhydric alcohol; Dicyclic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, halogen substituents thereof, and alkylene oxide adducts thereof by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate; Allyl (meth) acrylate; Aromatic divinyl compounds, such as divinyl benzene, etc. are mentioned. When copolymerizing a polyfunctional monomer, among these, ethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and neopentyl glycol di (meth) acrylate are used preferably.

The acrylic resin containing methyl methacrylate as a main component may further be modified by performing a reaction between functional groups due to monomers. As the reaction, for example, the methanol chain condensation reaction of the methyl ester group of methyl acrylate and the hydroxyl group of 2- (hydroxymethyl) methyl acrylate, the polymer chain of the carboxyl group of acrylic acid and the hydroxyl group of 2- (hydroxymethyl) acrylate Dehydration condensation reaction;

Acrylic resins containing methyl methacrylate as a main component can be easily obtained from commercially available products. For example, "Sumipex" sold by Sumitomo Chemical Co., Ltd. and Mitsubishi Rayon Co., Ltd. are sold under the trade names. "Acrylic Pet", "Delpet" sold by Asahi Kasei Co., Ltd., "Parapet" sold by Kuraray Co., Ltd., and "Aquarie" sold by Nippon Catalyst.

<Other description about the visual side transparent protective film of a front side polarizing plate>

Anti-glare to polypropylene-based resin film, polyethylene terephthalate-based resin film or acrylic resin film used as transparent protective film 23 located on the side away from the liquid crystal cell 10 of the front side polarizing plate 20, that is, the viewer side (Haze) can be given. In order to impart anti-glare property, for example, a method of mixing inorganic films or organic particles in the above-mentioned raw material resin and forming a film, when forming a film, consists of a resin layer in which particles are mixed by multilayer extrusion and the other A method of forming a two-layer film of an unmixed resin layer, or forming a three-layer film with the resin layer mixed with fine particles outward, or a coating liquid obtained by mixing inorganic fine particles or organic fine particles on one side of the film with the curable binder resin. Is coated, and the binder resin is cured to form an antiglare layer.

Examples of the inorganic fine particles for imparting anti-glare properties include silica, colloidal silica, alumina, alumina sol, aluminosilicate, alumina-silica composite oxide, kaolin, talc, mica, calcium carbonate, calcium phosphate and the like. Examples of the organic fine particles include crosslinked polyacrylic acid particles, methyl methacrylate / styrene copolymer resin particles, crosslinked polystyrene particles, crosslinked polymethylmethacrylate particles, silicone resin particles, polyimide particles, and the like.

It is preferable that the protective film provided with anti-glare property has the haze value in 6 to 45% of range. If the haze value of this film is less than 6%, sufficient anti-glare effect may not be expressed. On the other hand, if the haze value exceeds 45%, the white or image quality of the screen when the polarizing plate to which the film is bonded is applied to the liquid crystal display device. May result in deterioration.

The haze value can be measured using a commercially available haze measuring instrument based on JIS K 7136. Examples of the haze meter include a haze-transmittance meter "HM-150" (trade name) sold by Murakami Color Research Institute. At the time of a haze value measurement, in order to prevent curvature of a film, it is preferable to use the measurement sample which bonded the film to the glass substrate so that the surface which provided anti-glare property, for example using an optically transparent adhesive may become a surface.

Such a protective film may have a functional layer such as a conductive layer, a hard coat layer, and a low reflection layer. It is also possible to select a resin composition having such a function as the binder resin constituting the transparent protective film and to allow the film itself to have one and a plurality of functions. In addition, it may have a smoothing layer, an unsaturation layer, a blocking prevention layer, an easily bonding layer, and the like. Since this protective film is laminated | stacked on a polarizing film through an adhesive bond layer, it is preferable to provide an easily bonding layer especially in the bonding surface to a polarizing film.

The component constituting the easily adhesive layer may be, for example, a polyester resin having a polar group in a skeleton, a relatively low molecular weight, low glass transition temperature, a urethane resin, an acrylic resin, or the like. If necessary, a crosslinking agent, an organic or inorganic filler, a surfactant, a lubricant, and the like may be contained.

If the said functional layer is a polypropylene resin film or an acrylic resin film, it can form directly in the film formed into a film, for example. On the other hand, if it is an extending | stretching polyethylene terephthalate type resin film, the method of forming in the film which completed all the extending processes, the method of forming between longitudinal stretch and a lateral stretch process, for example, during extending | stretching of a resin film, a polarizing film, and adhesiveness The method of forming immediately before or after bonding can be adopted. In particular, in the case of polyethylene terephthalate-based resin, a method of forming a functional layer after longitudinal stretching and then transverse stretching is preferably employed from the viewpoint of productivity.

[Transparent protective film located in the side far from liquid crystal cell of back side polarizing plate]

It is preferable to comprise the transparent protective film 33 located in the side far from the liquid crystal cell 10 of the back side polarizing plate 30 with a cellulose resin film. The cellulose resin film is a film composed of a partial or total ester compound of cellulose. For example, the film which consists of acetic acid ester of cellulose, propionic acid ester, butyric acid ester, their mixed ester, etc. is mentioned. Especially, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, etc. are used preferably.

A cellulose resin film can obtain a commercial item easily, for example, "Fuji-Tak TD" sold by Fujifilm Co., Ltd. under each brand name, "Konica Minolta TAC film sold by Konica Minolta Opt Co., Ltd." KC ".

[Transparent protective film located on the liquid crystal cell side]

The transparent protective film located on the side far from the liquid crystal cell 10 includes a resin material constituting the transparent protective films 24 and 34 positioned on the liquid crystal cell 10 side in the front side polarizing plate 20 and the back side polarizing plate 30. The same thing as what was demonstrated about (23,33) can be used, and another resin film can also be used. In particular, since the control of retardation value is easy and it is easy to obtain, the polyolefin resin containing a cellulose resin, linear polyolefin resin, or cyclic polyolefin resin is used preferably.

Although cyclic polyolefin resin here is obtained by superposing | polymerizing cyclic olefin monomers, such as norbornene and other cyclopentadiene derivatives in catalyst presence, if it is resin which ring-opened metathesis polymerization of the cyclic olefin monomer, it is continuous to this It is preferable that the unsaturated bond is substantially lost by the hydrogenation reaction. When such cyclic polyolefin type resin is used, it is easy to obtain the transparent protective film which has a predetermined retardation value mentioned later.

As cyclic polyolefin type resin, the ring-opening metathesis polymerization is carried out as a monomer, for example, norbornene obtained by Diels-Alder reaction from cyclopentadiene, olefins, or (meth) acrylic acid, or ester thereof as a monomer, Resin obtained by continuous hydrogenation; Tetracyclododecene and derivatives thereof obtained by Diels-Alder reaction from dicyclopentadiene and olefins or (meth) acrylic acid or esters thereof are subjected to ring-opening metathesis polymerization as monomers, followed by continuous hydrogenation. Resin obtained; Resins obtained by ring-opening metathesis copolymerization of at least two monomers selected from norbornene, tetracyclododecene, derivatives thereof and other cyclic olefin monomers in the same manner, and subsequent hydrogenation thereof; The resin etc. which are obtained by addition-copolymerizing the aromatic compound which has a linear olefin and / or a vinyl group to cyclic olefins, such as norbornene, tetracyclo dodecene, or its derivative (s), etc. are mentioned.

Cyclic polyolefin resin can obtain a commercial item easily. Examples of commercially available products include "TOPAS" produced by TOPAS ADVANCED POLYMERS GmbH under each brand name and sold by Polyplastics Co., Ltd., and "Aton" sold by JSR Co., Ltd., Japan Xeon Co., Ltd. "Zeonoa" and "Xeonex" sold, "Apel" sold by Mitsui Chemicals Co., Ltd., etc. are mentioned.

Typical examples of linear polyolefin resins are polyethylene resins and polypropylene resins. Among them, propylene homopolymers or copolymers mainly composed of propylene and copolymerizable therewith, such as copolymers copolymerized with ethylene at a ratio of 1 to 20% by weight, preferably 3 to 10% by weight, are preferably used.

What is necessary is just to select suitably the method of forming a film into a film with cellulose resin, polyolefin resin, etc. according to each resin. For example, a solvent cast method in which a resin dissolved in a solvent is rolled onto a metal band or drum, and the solvent is dried to remove a film to obtain a film, and the resin is heated above its melting temperature, kneaded, extruded from a die, and cooled by a cooling drum. The melt extrusion method etc. which obtain a film by doing it can be used. Among them, the melt extrusion method is preferably employed from the viewpoint of productivity of the polyolefin resin. On the other hand, it is common for cellulose resin to be formed into a film by the solvent casting method.

When the liquid crystal cell 10 is in the In-Plane Switching (IPS) mode, the transparent protective film 24 located on the liquid crystal cell 10 side may be used so as not to impair the wide viewing angle characteristic inherent in the IPS mode liquid crystal cell. (34) enumerates that the first form in which the retardation Rth in the thickness direction is in the range of -10 to +10 nm is preferred. The retardation Rth in the thickness direction is a value obtained by multiplying the thickness of the film by a value obtained by subtracting the refractive index in the thickness direction from the in-plane average refractive index, and is represented by the following formula (3). In addition, in-plane retardation Re is a value obtained by multiplying the thickness of a film by the in-plane refractive index difference, and is represented by following formula (4).

Rth = [(n _x + n _y ) / 2-n _z ] × d (3)

Re = (n _x -n _y ) × d (4)

Where n _x is the refractive index in the slow axis direction (x-axis direction) in the film plane, n _y is the refractive index in the fast axis direction (y-axis direction orthogonal to the x axis in a side surface) in a film plane, and n _z is film thickness Is the refractive index in the direction (z-axis direction perpendicular to the film plane), and d is the thickness of the film.

Here, the retardation value may be a value at any wavelength in the range of about 500 to 650 nm in the vicinity of the center of visible light, but in this specification, the retardation value is assumed as a standard at a wavelength of 590 nm. The retardation Rth in the thickness direction and the in-plane retardation Re can be measured using various commercially available retarders.

As a method of controlling the retardation Rth of the thickness direction of a resin film in the range of -10-+10 nm, the method of reducing residual distortion to a maximum in the thickness direction at the time of manufacturing a film is mentioned. For example, in the said solvent casting method, the method etc. which reduce the residual shrinkage distortion of the thickness direction which generate | occur | produce when drying this flexible resin solution by heat processing can be employ | adopted. On the other hand, in the melt extrusion method, the resin film is extruded from the die, the distance from the die to the cooling drum is shortened as much as possible in order to prevent stretching between the cooling, and the extrusion amount and the rotational speed of the cooling drum are prevented from stretching the film. The control method etc. can be employ | adopted. In addition, similarly to the solvent casting method, a method of alleviating the distortion remaining in the obtained film by heat treatment may be employed.

When the liquid crystal cell 10 is in the same IPS mode, one of the transparent protective films 24 and 34 positioned on the side of the liquid crystal cell 10 has a retardation Rth in the thickness direction in the range of -10 to +10 nm and the other One is that the second form in which the in-plane retardation Re is in the range of 100 to 300 nm and the Nz coefficient in the range of 0.1 to 0.7 is also preferable to realize higher viewing angle characteristics. Here, the Nz coefficient is defined in the following formula (5), and n _x , n _y and n _z in the formula have the same meaning as defined above.

Nz factor = (n _x -n _z ) / (n _x -n _y ) (5)

Therefore, the liquid crystal display obtained by constructing one of the transparent protective films 24 and 34 positioned on the liquid crystal cell 10 side with a small retardation in the thickness direction and the other as a retardation film having specific refractive index anisotropy has a wide angle. The display characteristics can be suitably maintained over time. In this case, the same description as that of the first embodiment is applied to the film having the retardation Rth in the thickness direction in the range of -10 to +10 nm. The retardation film having an in-plane retardation Re in the range of 100 to 300 nm and having a Nz coefficient of 0.1 to 0.7 is more preferably in the thickness direction retardation Rth in the range of -40 to +40 nm.

The retardation film having in-plane retardation in the range of 100 to 300 nm and Nz coefficient in the range of 0.1 to 0.7 may be composed of, for example, a polyolefin resin, preferably a cyclic polyolefin resin. Moreover, the retardation film which has a refractive index characteristic is the method of extending | stretching a polyolefin resin film, bonding a shrinkable film which has a predetermined shrinkage rate to it, and heating it, and shrink | contracting in the direction orthogonal in a plane extending | stretching in front, A stretching treatment is performed while further heating the stretched polyolefin resin film to which the shrinkable film is bonded, and shrinking in the direction perpendicular to the stretching direction and in-plane, and bonding the shrinkable film having a predetermined shrinkage rate to the polyolefin resin film and in that state. Stretching is carried out while heating, and the relationship of n _x > n _z > n _y can be realized by a method such as stretching and shrinking in the direction perpendicular to the stretching direction and in-plane.

In addition, when the liquid crystal cell 10 is in the same IPS mode, one of the transparent protective films 24 and 34 positioned on the side of the liquid crystal cell 10 has a retardation Rth in the thickness direction in a range of -10 to +10 nm. The other is located in the polarizing film side which comprises the polarizing plate, and is located in the adhesive layer side rather than the 1st phase difference film which consists of polyolefin resin, and this 1st phase difference film, The core layer which consists of styrene resin, and the both surfaces of the core layer The 3rd aspect which is a laminated body of the 2nd phase difference film which has a 3-layered structure which consists of a skin layer which consists of a (meth) acrylic-type resin composition containing the laminated rubber particle is also preferable in order to implement | achieve a higher viewing angle characteristic.

The laminated constitution example of this 3rd form is shown in a cross-sectional schematic diagram in FIG. In this example, the transparent protective film 24 located on the liquid crystal cell 10 side of the front side polarizing plate 20 is configured such that the retardation Rth in the thickness direction is in the range of -10 to +10 nm, and the back side polarizing plate 30 The transparent protective film 34 located at the liquid crystal cell 10 side of the ()) is composed of the laminate of the first retardation film 36 and the second retardation film 37 described above. In FIG. 2, the other part is the same as that of FIG. 1, and the same code | symbol is attached | subjected to the same part as FIG. Of course, in FIG. 2, the positions of the protective film 24 and the protective film 34 are reversed with the liquid crystal cell 10 interposed therebetween, that is, the transparent protective film positioned on the liquid crystal cell 10 side of the front polarizing plate 20. The transparent protective film (24) which consists of a laminated body of the 1st retardation film which consists of said polyolefin resin, and the 2nd retardation film which has a 3-layered structure, and is located in the liquid crystal cell 10 side of the back side polarizing plate 30 ( The structure which comprised 34) with the said retardation Rth of the thickness direction in the range of -10-+10 nm is also contained in the 3rd form mentioned here.

In a third embodiment having a representative example as shown in FIG. 2, a film in which the retardation Rth in the thickness direction is in the range of −10 to +10 nm (located on the liquid crystal cell 10 side of the front polarizing plate 20 in FIG. 2). For the protective film 24, the same description as that described in the first embodiment is applied.

Next, in the third aspect, a film composed of a laminate of the first retardation film 36 made of polyolefin resin and the second retardation film 37 having a three-layer structure (in FIG. 2, the liquid crystal of the back side polarizing plate 30). The protective film 34 located on the cell 10 side will be described. The polyolefin resin constituting the first retardation film 36 includes a cyclic olefin resin or a linear olefin resin as described above. Especially cyclic olefin resin is used preferably.

Further, the first retardation film 36 preferably has refractive index anisotropy in which the in-plane retardation Re is in the range of 30 to 150 nm, and the Nz coefficient defined by the formula (9) is in the range of more than 1 and less than 2. . On the other hand, it is preferable that the second retardation film 37 has in-plane retardation Re in the range of 20 to 120 nm, and the refractive index anisotropy in which the Nz coefficient defined by the formula (9) is greater than -2 and less than -0.5. Do.

The first retardation film 36 made of a polyolefin resin having refractive index anisotropy as described above can be produced by known all-day uniaxial stretching, tenter lateral uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, and the like. In addition to appropriately adjusting the draw ratio and the draw speed so as to obtain, various temperatures such as preheating temperature, stretching temperature, heat set temperature, cooling temperature, and the like may be appropriately selected.

It is preferable that the thickness of the 1st retardation film 36 exists in the range of 20-80 micrometers, and 40-80 micrometers. When the thickness of this film is less than 20 micrometers, it will become difficult to handle a film, and a predetermined phase difference value will become difficult to express, On the other hand, when the thickness exceeds 80 micrometers, workability will fall and transparency will fall, The weight of the laminated polarizing plate may be large.

On the opposite side (liquid crystal cell 10 side) with the polarizing film 31 of the 1st retardation film 36, the core layer 38 which consists of styrene resins, and the rubber particle laminated | stacked on both surfaces (meta) A second retardation film 37 having a three-layer structure composed of skin layers 39 and 39 made of an acrylic resin composition is disposed.

The styrenic resin constituting the core layer 38 may be a homopolymer of styrene and its derivatives, and may be a binary or more copolymer of styrene or its derivatives and other copolymerizable monomers. The styrene derivative is a compound in which another group is bonded to styrene, for example, alkyl styrene such as o-methyl styrene, m-methyl styrene, p-methyl styrene, 2,4-dimethyl styrene, o-ethyl styrene and p-ethyl styrene. Or substituted styrene having a hydroxyl group, an alkoxy group, a carboxyl group or a halogen group introduced into the benzene nucleus of styrene such as hydroxy styrene, tert-butoxystyrene, vinyl benzoic acid, o-chlorostyrene and p-chlorostyrene. have. Terpolymers as disclosed in Japanese Patent Laid-Open No. 2003-50316 or Japanese Patent Laid-Open No. 2003-207640 can also be used. The styrene resin is preferably a copolymer of styrene or a styrene derivative and at least one monomer selected from the group consisting of acrylonitrile, maleic anhydride, methyl methacrylate and butadiene. It is preferable that the styrene resin which comprises the core layer 38 is heat resistant, and generally the glass transition temperature ("Tg") is 100 degreeC or more. Tg more preferable than styrene resin is 120 degreeC or more.

It is preferable to set the core layer 38 made of styrene resin so that the thickness thereof becomes 10 to 100 µm. When the thickness is less than 10 micrometers, it may be difficult to express sufficient retardation value by extending | stretching. On the other hand, when the thickness exceeds 100 μm, the impact strength of the film tends to be weakened, the change in retardation due to external stress tends to be large, and when it is applied to a liquid crystal display device, white omission is likely to occur and display performance is degraded. Easy to be

The skin layers 39 and 39 disposed on both surfaces of the core layer 38 made of the styrene resin are composed of a (meth) acrylic resin composition in which rubber particles are blended with the (meth) acrylic resin. Here, as (meth) acrylic-type resin, the homopolymer of methacrylic acid alkyl ester or acrylic acid alkyl ester, the copolymer of methacrylic acid alkyl ester, and acrylic acid alkyl ester, etc. are mentioned, for example. Specific examples of the methacrylic acid alkyl esters include methyl methacrylate, ethyl methacrylate, methacrylate propyl, and the like. Specific examples of the acrylic acid alkyl esters include methyl acrylate, ethyl acrylate, and propyl acrylate. As such (meth) acrylic-type resin, what is marketed as general purpose (meth) acrylic-type resin can be used. In addition, the (meth) acrylic resins include those called impact-resistant (meth) acrylic resins, and those called high heat-resistant (meth) acrylic resins having a glutaric anhydride structure and a lactone ring structure in the main chain.

As for the rubber particle mix | blended with (meth) acrylic-type resin, an acryl-type thing is preferable. Acrylic rubber particles are particles having rubber elasticity obtained by polymerizing an acrylic acid alkyl ester such as butyl acrylate or 2-ethylhexyl acrylate as a main component and polymerizing in the presence of a polyfunctional monomer. Such rubber elastic particles may be formed in a single layer, or a multilayer structure having at least one rubber elastic layer. As the acrylic rubber particles having a multi-layered structure, the particles having rubber elasticity as described above are taken as the nucleus and the surroundings are covered with a hard methacrylic acid alkyl ester polymer, and the hard methacrylic acid alkyl ester copolymer is used as the nucleus. The surroundings are covered with an acrylic copolymer having rubber elasticity as described above, the hard core is covered with a rubber elastic acrylic copolymer, and the surroundings are covered with a hard methacrylic acid alkyl ester polymer. do. Such rubber particles are usually in the range of 50-400 nm in average diameter of the particles formed in the elastic layer.

In the (meth) acrylic resin composition constituting the skin layer 39, the content of the rubber particles is usually about 5 to 50 parts by weight per 100 parts by weight of the (meth) acrylic resin. Since (meth) acrylic-type resin and acrylic rubber particle are marketed in the state which mixed them, the commercial item can be used. As an example of the commercial item of the (meth) acrylic-type resin in which the acrylic rubber particle was mix | blended, "HT55X", "Technoloy S001", etc. which are sold by Sumitomo Chemical Co., Ltd. are mentioned. Such a (meth) acrylic resin composition generally has a Tg of 160 ° C or lower, but the preferable Tg is 120 ° C or lower, and 110 ° C or lower.

It is preferable that the skin layers 39 and 39 made of the (meth) acrylic resin composition in which rubber particles and preferred acrylic rubber particles are blended have a thickness of 10 to 100 µm. If the thickness is made less than 10 m, the film forming tends to be difficult. On the other hand, when thickness exceeds 100 micrometers, there exists a tendency for the retardation of this (meth) acrylic-type resin layer to be negligible.

As described above, the core layer 38 made of styrene resin in the second retardation film 37 preferably has a Tg of 120 ° C. or higher, and a skin layer made of a (meth) acrylic resin composition containing rubber particles. It is preferable that the Tg of (39) is 120 degrees C or less, and 110 degrees C or less. It is preferable that the core layer 38 made of a styrene resin without both Tg overlapping have a higher Tg than the skin layer 39 made of the (meth) acrylic resin composition in which rubber particles are blended.

The manufacture of the 2nd phase difference film 37 which has a 3-layered structure coextrudes the (meth) acrylic-type resin composition which the styrene resin and rubber particle were mix | blended, for example, forms a film of a 3-layered structure, and it extends | stretches after that Just do it. In addition, after manufacturing a single | mono layer film, respectively, the method of heat-sealing by heat lamination and extending | stretching it is also possible.

The second retardation film 37 has a three-layer structure in which skin layers 39 and 39 made of a (meth) acrylic resin composition in which rubber particles are blended are formed on both surfaces of the core layer 38 made of styrene resin. In this three-layer structure, the skin layers 39 and 39 disposed on both sides are generally about the same thickness. In this manner, the three-layer structure allows the skin layers 39 and 39 made of the (meth) acrylic resin composition in which the rubber particles are blended to act as a protective layer, thereby providing excellent mechanical strength and chemical resistance.

In-plane retardation is given to the 2nd phase difference film 37 comprised as mentioned above by extending | stretching. Stretching can be performed by known all-day stretching, tenter transverse stretching, simultaneous biaxial stretching, sequential biaxial stretching, or the like, and stretching may be performed to obtain a desired retardation value.

The second retardation film 37 is laminated on the first retardation film 36 through the interlayer adhesive 40. Although the method of laminating | stacking the 2nd phase difference film 37 on the 1st phase difference film 36 is not specifically limited, In general, it is an interlayer adhesive on the surface of the 1st phase difference film 36 or the surface of the 2nd phase difference film 37 generally. 40 is formed. Such an interlayer adhesive 40 can be formed by applying and drying an adhesive solution, and the adhesive layer is formed in the release process surface of the indication film (separator) in which the release process was performed (the adhesive with a separator added). ) Can also be formed by a method of bonding it to the adhesive surface of the first retardation film 26 or the second retardation film 37 on the pressure-sensitive adhesive layer side. As another method, the separator provision adhesive which provided the adhesive layer on the above-mentioned separator is prepared, and the adhesive surface of the 1st phase difference film 36 bonded to the polarizing film 31, or the adhesion of the 2nd phase difference film 37 was carried out. You may employ | adopt the method etc. which transfer to a surface. The separator is peeled off from the pressure-sensitive adhesive layer immediately before bonding to another film.

In addition, when forming the interlayer adhesive 40 on the surface of the 1st phase difference film 36 or the surface of the 2nd phase difference film 37, the adhesive layer forming surface or 2nd phase difference of the 1st phase difference film 36 as needed. Treatment to improve the adhesiveness on the pressure-sensitive adhesive layer-forming surface of the film 37 may be performed, for example, corona treatment or the like, and the same treatment may be performed on the surface of the interlayer pressure-sensitive adhesive 40 bonded to the first retardation film 36, or You may carry out on the surface of the interlayer adhesive 40 bonded to the 2nd phase difference film 37. FIG.

Bonding of the 1st phase difference film 36 and the 2nd phase difference film 37, and bonding of the polarizing film 31 and the 1st phase difference film 36 can be performed by the technique known conventionally. For example, the slow axis of the retardation film in the state where the 1st retardation film 36 and the 2nd retardation film 37 were laminated | stacked with respect to the polarization transmission axis of the polarizing film 31 using the bonding roll etc. is orthogonal or parallel. It is performed by the method of bonding so that it may become so, or the method of bonding so that the slow axis of the retardation film of the state laminated | stacked with respect to the polarization transmission axis of the polarizing film 31 may become a predetermined angle.

[Common explanation on the protective film located on the side far from the liquid crystal cell and the side of the liquid crystal cell]

The transparent protective films 23 and 33 positioned far from the liquid crystal cell and the transparent protective films 24 and 34 positioned on the liquid crystal cell side have easy adhesion such as saponification treatment, corona treatment, and plasma treatment prior to adhesion to the polarizing film. The process can be performed.

The thickness of this transparent protective film 23, 24, 33, 34 is usually about 20-300 micrometers from a viewpoint of strength, handleability, etc., Preferably it is the range of 20-100 micrometers. When the thickness is within this range, the polarizing film can be mechanically protected and exposed to high temperature, high humidity, and thus the polarizing film can be maintained without stable shrinkage.

[Adhesion of Polarizing Film and Protective Film]

The bonding of the polarizing film 21 and the transparent protective films 23 and 24 on the front side polarizing plate 20 and the bonding of the polarizing film 31 and the transparent protective films 33 and 34 on the back side polarizing plate 30 is usually performed. Adhesive is used. The thickness of the adhesive bond layer which bonds a polarizing film and a transparent protective film can be about 0.01-30 micrometers, Preferably it is 0.01-10 micrometers, More preferably, it is 0.05-5 micrometers. When the thickness of an adhesive bond layer exists in this range, the lifting force and peeling do not arise between the transparent protective film laminated | stacked and a polarizing film, and the adhesive force which is satisfactory practically is obtained.

In formation of an adhesive bond layer, a suitable adhesive agent can be used normally according to the kind and objective of a to-be-adhered body, and anchor coating agent can also be used as needed. Examples of the adhesive include a solvent adhesive, an emulsion adhesive, a pressure sensitive adhesive, a rehumidifying adhesive, a polycondensation adhesive, a solventless adhesive, a film adhesive, a hot melt adhesive, and the like.

One of the preferred adhesives includes an aqueous adhesive, ie, an adhesive component dissolved or dispersed in water. Examples of the adhesive component soluble in water include polyvinyl alcohol-based resins. Examples of the adhesive component that can be dispersed in water include a urethane resin having a hydrophilic group. Water-based adhesives can be prepared by mixing these adhesive components with water with additional additives formulated as needed. Examples of commercially available polyvinyl alcohol-based resins that can be aqueous adhesives include "KL-318" (trade name), which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.

The aqueous adhesive may contain a crosslinking agent as necessary. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts, and the like. When the polyvinyl alcohol-based resin is used as the adhesive component, aldehyde compounds including glyoxal, methylol compounds including methylolmelamine, water-soluble epoxy resins, and the like are preferably used as the crosslinking agent. The water-soluble epoxy resin can be obtained by, for example, reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with dicarboxylic acid such as adipic acid. Polyamide epoxy resin. Examples of commercially available products of water-soluble epoxy resins include "Sumirez resin 650 (30)" (trade name) sold by Sumikake Mutex Co., Ltd.

Among the aqueous adhesives, suitable ones include polyvinyl alcohol-based resins and water-soluble epoxy resins.

A water-based adhesive agent is apply | coated to the adhesive surface of a polarizing film and / or a transparent protective film, and after bonding both, a drying process can be performed and a polarizing plate can be obtained. Prior to the adhesion, it is also effective to increase the wettability by subjecting the transparent protective film to an easy adhesion treatment such as saponification treatment, corona discharge treatment, or plasma treatment. Drying temperature can be made into about 60-100 degreeC, for example. Curing for about 1 to 10 days at a temperature slightly higher than room temperature after drying, for example, at a temperature of about 30 to 50 ° C., is preferable to further increase the adhesive force.

Other preferred adhesives include curable adhesive compositions containing epoxy compounds that cure by active energy ray irradiation or heating. Here, the curable epoxy compound is one having at least two epoxy groups in a molecule. In this case, adhesion | attachment of a polarizing film and a transparent protective film can be made into the method of hardening | curing the curable epoxy compound contained in an adhesive agent by irradiating or heating an active energy ray with respect to the application layer of the said adhesive composition. Curing of an epoxy compound is generally performed by cationic polymerization of an epoxy compound. Moreover, it is preferable to perform this hardening by active energy ray irradiation from a productivity viewpoint.

It is preferable that the epoxy compound contained in a curable adhesive composition does not contain an aromatic ring in a molecule | numerator from a viewpoint of weather resistance, refractive index, cationically polymerizable, etc. As an epoxy compound which does not contain an aromatic ring in a molecule | numerator, a hydrogenated epoxy compound, an alicyclic epoxy compound, an aliphatic epoxy compound, etc. can be illustrated. Epoxy compounds suitably used in such curable adhesive compositions are described in detail, for example, in Japanese Patent Application Laid-Open No. 2004-245925, but will be briefly described herein.

The hydrogenated epoxy compound may be obtained by glycidyl etherification of a nuclear hydrogenated polyhydroxy compound obtained by selectively performing a nuclear hydrogenation reaction in an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound in the presence of a catalyst and under pressure. . As an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound, For example, bisphenols, such as bisphenol A, bisphenol F, and bisphenol S; Novolak-type resins such as phenol novolak resin, cresol novolak resin and hydroxy benzaldehyde phenol novolak resin; Polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone and polyvinylphenol. Glycidyl ether can be obtained by performing a nuclear hydrogenation reaction with such an aromatic polyhydroxy compound and making epichlorohydrin react with the obtained nucleated hydrogenated polyhydroxy compound. Examples of suitable hydrogenated epoxy compounds include glycidyl ethers of hydrogenated bisphenol A.

The alicyclic epoxy compound is a compound having at least one epoxy group in the molecule bonded to the alicyclic ring. "Epoxy group bonded to an alicyclic ring" means a bridged oxygen atom -O- in the structure represented by the following formula, wherein m is an integer from 2 to 5.

[Formula 1]

In this formula, a compound in which one or more hydrogen atoms in (CH ₂ ) _m are bonded to different chemical structures may be an alicyclic epoxy compound. In addition, one or a plurality of hydrogen atoms in (CH ₂ ) _m forming an alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, epoxy compounds having an oxabicyclohexane ring (in the formula above, m = 3) and an oxabicycloheptane ring (in the above formula (m = 4)) are preferably used because they exhibit excellent adhesion. The specific example of an alicyclic epoxy compound is shown below. Here, the compound names are listed first, and then the corresponding chemical formulas are shown, and the compound names and the chemical formulas corresponding thereto are denoted by the same symbols.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,

B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,

C: Ethylene bis (3,4-epoxycyclohexanecarboxylate),

D: bis (3,4-epoxycyclohexylmethyl) adipate,

E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,

F: diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),

G: ethylene glycol bis (3,4-epoxycyclohexylmethyl ether),

H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrisspiro [5.2.2.5.2.2] henic acid,

I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,

J: 4-vinylcyclohexene dioxide,

K: limonene dioxide,

L: bis (2,3-epoxycyclopentyl) ether,

M: dicyclopentadiene dioxide, and the like.

[Formula 2]

The aliphatic epoxy compound may be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, diglycidyl ether of propylene glycol; Diglycidyl ether of 1,4-butanediol; Diglycidyl ether of 1,6-hexanediol; Triglycidyl ether of glycerin; Triglycidyl ether of trimethylol propane; Polyglycidyl ethers of polyether polyols obtained by adding alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin (e.g., diglycidyl ether of polyethylene glycol) This is listed.

In curable adhesive composition, an epoxy compound may be used individually by 1 type, and may use 2 or more types together. Especially, it is preferable that this epoxy compound contains the alicyclic epoxy compound which has at least one epoxy group couple | bonded with an alicyclic ring in a molecule | numerator.

The epoxy compound used in the curable adhesive composition usually has an epoxy equivalent in the range of 30 to 3,000 g / equivalent, and the epoxy equivalent is preferably in the range of 50 to 1,500 g / equivalent. In the case where the epoxy compound having an epoxy equivalent of less than 30 g / equivalent is used, the effectiveness of the polarizing plate after curing may decrease or the adhesive strength may decrease. On the other hand, the compound which has an epoxy equivalent exceeding 3,000 g / equivalent may fall compatibility with the other component contained in an adhesive composition.

From the viewpoint of the reaction, cationic polymerization is preferably used as the curing reaction of the epoxy compound. For that purpose, it is preferable to mix | blend a cationic polymerization initiator with the curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates cationic species or Lewis acids by active energy ray irradiation or heating such as visible light, ultraviolet ray, X-ray, and electron beam and starts the polymerization reaction of the epoxy group. From the viewpoint of workability, it is preferable that a potential be imparted to the cationic polymerization initiator. Hereinafter, the cationic species which generate | occur | produce a cationic species or Lewis acid by irradiation of an active energy ray, and start the polymerization reaction of an epoxy group is called "photocationic polymerization initiator", and generate | occur | produce a cationic species or Lewis acid by heat, and superpose | polymerize an epoxy group The cationic polymerization initiator that starts the reaction is referred to as "thermal cationic polymerization initiator".

The method of using the photocationic polymerization initiator and curing the adhesive composition by active energy ray irradiation can be cured at room temperature and reduces the need to consider deformation due to heat resistance or expansion of the polarizing film, and the transparent protective film and the polarizing film It is advantageous in that it can adhere well. Moreover, since a photocationic polymerization initiator acts catalytically with light, even if it mixes with an epoxy compound, it is excellent in storage stability and workability.

As a photocationic polymerization initiator, For example, Aromatic diazonium salt; Onium salts, such as an aromatic iodonium salt and an aromatic sulfonium salt, an iron- allene single substance, etc. can be mentioned. The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably it is 15 weight part or less. When the compounding quantity of a photocationic polymerization initiator is less than 0.5 weight part with respect to 100 weight part of epoxy compounds, hardening will become inadequate and there exists a tendency for the mechanical strength and adhesive strength of hardened | cured material to fall. On the other hand, when the compounding quantity of a photocationic polymerization initiator exceeds 20 weight part with respect to 100 weight part of epoxy compounds, since the ionic substance of hardened | cured material increases, the hygroscopicity in hardened | cured material may become high and durability performance may fall.

When using a photocationic polymerization initiator, curable adhesive composition can contain a photosensitizer further as needed. The photosensitizer can be used to improve the reactivity of the cationic polymerization and to improve the mechanical strength or adhesive strength of the cured product. As a photosensitizer, a carbonyl compound, an organic sulfur compound, a persulfide, a redox type compound, an azo compound, a diazo compound, a halogen compound, a photoreducing dye etc. are mentioned, for example. When mix | blending a photosensitizer, it is preferable to make the quantity into the range of 0.1-20 weight part with respect to 100 weight part of curable adhesive compositions.

On the other hand, as a thermal cation polymerization initiator, a benzyl sulfonium salt, a thiophenium salt, a thiornium salt, benzyl ammonium, a pyridium salt, a hydradinium salt, a carboxylic acid ester, a sulfonic acid ester, an amine imide, etc. are mentioned.

The curable adhesive composition containing the epoxy compound is preferably cured by photocationic polymerization as described above, but may also be cured by thermal cationic polymerization by the presence of the above thermal cationic polymerization initiator, or photocationic polymerization and thermocationic polymerization. It is also possible to use together. When using together photocationic polymerization and thermocationic polymerization, it is preferable to contain both a photocationic polymerization initiator and a thermocationic polymerization initiator in a curable adhesive composition.

Moreover, curable adhesive composition may further contain compounds which accelerate cationic polymerization, such as an oxetane compound and a polyol compound. Oxetane compounds are compounds having a four-membered ring ether in the molecule. When it contains an oxetane compound, the amount is 5 to 95 weight% normally in curable adhesive composition, Preferably it is 5 to 50 weight%. The polyol compound may also be an alkylene glycol or oligomer thereof, including ethylene glycol, hexamethylene glycol, polyethylene glycol, and the like, polyester polyol, polycaprolactone polyol, polycarbonate polyol, and the like. When blending a polyol compound, the amount is usually 50% by weight or less, preferably 30% by weight or less in the curable adhesive composition.

In addition, the curable adhesive composition may contain other additives such as ion traps, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoams, and the like so long as they do not impair the adhesion thereof. have. As the ion trapping agent, inorganic compounds including, for example, powdery bismuth based, antimony based, magnesium based, aluminum based, calcium based, titanium based, mixed based thereof, and the like are exemplified. Dud phenolic antioxidants etc. are mentioned.

The curable adhesive composition containing the epoxy compound is coated on the adhesive side or both sides of the polarizing film or the transparent protective film, and then bonded at the adhesive coated side, and the uncured adhesive layer is irradiated by heating or heating the active energy ray. By hardening | curing, a polarizing film and a transparent protective film can be adhere | attached. As a coating method of an adhesive agent, various coating methods, such as a doctor blade, a wire bar, a die coater, a Kanma coater, a gravure coater, can be used, for example.

Although this curable adhesive composition can be basically used as a solvent-free adhesive which does not contain a solvent substantially, each coating system may contain a solvent for viscosity adjustment because each coating system has an optimum viscosity range. The solvent is preferably an organic solvent that dissolves each component including an epoxy compound well without degrading the optical performance of the polarizing film. For example, hydrocarbons represented by toluene, esters represented by ethyl acetate, or the like can be used. Can be.

When hardening an adhesive composition by irradiation of an active energy ray, although the above-mentioned various things can be used as an active energy ray, an ultraviolet-ray is used preferably at the point which is easy to handle and the control of irradiation amount etc. is also possible. Irradiation intensity or irradiation amount of the active energy ray, for example ultraviolet rays, is suitably maintained so as to maintain proper productivity within a range that does not affect various optical performances including polarization degree of the polarizing film and various optical performances including transparency and retardation characteristics of the transparent protective film. Is determined.

When the adhesive composition is cured by heat, it can be heated in a generally known manner. Usually, the heating proceeds above the temperature at which the cationic polymerization initiator contained in the curable adhesive composition generates cationic species or Lewis acid, and the specific heating temperature is, for example, about 50 to 200 ° C.

Bonding of the polarizing film 21 and the transparent protective films 23 and 24 on the front side polarizing plate 20, and bonding of the polarizing film 31 and the transparent protective films 33 and 34 on the back side polarizing plate 30, respectively. The curable adhesive composition containing the epoxy compound which hardens by the water-based adhesive agent or active energy ray irradiation demonstrated so far about can be used. The adhesive used for the front side polarizing plate 20 and the adhesive used for the back side polarizing plate 30 may be the same or different. For example, in one polarizing plate, an aqueous adhesive is used to bond the polarizing film and the transparent protective film on both sides thereof, and in the other polarizing plate, the polarizing film and its composition are formed using a curable adhesive composition containing an epoxy compound cured by active energy ray irradiation. It is also possible to form an aspect such as bonding both transparent protective films. Although the adhesive agent which bonds a polarizing film and the transparent protective film of both surfaces in one polarizing plate may be same or different, it is preferable to use the same adhesive agent in one polarizing plate in simplifying a manufacturing process.

[Pressure sensitive adhesive layer]

1 and 2 in the present invention, in the front side polarizing plate 20, on the opposite side to the polarizing film 21 of the transparent protective film 24 bonded to the liquid crystal cell 10, and also the back side polarizing plate 30. In the above, pressure-sensitive adhesive layers 51 and 52 are formed on the opposite side to the polarizing film 31 of the transparent protective film 34 bonded to the liquid crystal cell 10, respectively. The pressure-sensitive adhesive layers 51 and 52 may be those that are excellent in optical transparency and exhibit adhesive characteristics including appropriate wettability, cohesion, adhesiveness, and the like, and particularly those having excellent durability and the like are preferably used. As an adhesive suitable for forming the adhesive layers 51 and 52, the pressure-sensitive adhesive (also called acrylic adhesive) which consists of acrylic resin is mentioned, for example. When using the form shown in FIG. 2, the acrylic adhesive is similarly used also for the interlayer adhesive 40 similarly.

Examples of the acrylic pressure-sensitive adhesive include resins containing (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, and these (meth) The copolymer resin which used 2 or more types of acrylic acid esters is used preferably. In addition, a polar monomer is copolymerized with this resin. As a polar monomer, it is (meth) acrylic acid, (meth) acrylic acid 2-hydroxypropyl, (meth) acrylic acid 2-hydroxyethyl, (meth) acrylamide, 2-N, N-dimethyl amino ethyl (meth), for example. The polymerizable compound which has polar functional groups, such as a carboxyl group, a hydroxyl group, an amide group, an amino group, and an epoxy group, such as an acrylate and glycidyl (meth) acrylate, is used. Moreover, the crosslinking agent is mix | blended with an acrylic resin normally in an adhesive.

In addition, various additives may be mix | blended with an adhesive. Suitable additives include silane coupling agents and antistatic agents. The silane coupling agent is effective for enhancing the adhesion with glass. Antistatic agents are effective for reducing or preventing the generation of static electricity. That is, when the polarizing plate is attached to the liquid crystal cell through the pressure sensitive adhesive layer, the surface protective film (also referred to as a separator) that covers the pressure sensitive adhesive layer is peeled off and bonded to the liquid crystal cell, but occurs when the surface protective film is peeled off. The static electricity may cause the liquid crystal alignment of the cell to be poor, which may cause display failure of the IPS mode liquid crystal display. The combination of antistatic agents is effective to reduce or prevent the occurrence of such static electricity.

[Moisture Evaporation Rate of Polarizer Plate]

1 and 2, the water evaporation rate V _f of the front side polarizing plate 20 having the pressure sensitive adhesive layer 51 and the back side polarizing plate 30 having the pressure sensitive adhesive layer 52 are provided. and the ratio V _f / V _r of V _r in the range of more than 0 to less than 1. Preferably, V _f / V _r may be in a range of 0.01 or more and less than 1. By setting the relationship between the moisture evaporation rates of both to this range, when the backlight unit 70 is turned on, the liquid crystal panel 60 rapidly rises in temperature due to the light supplied therefrom, and moisture is absorbed from the polarizing plates 20 and 30. The balance during shrinkage due to evaporation is good, and deformation of the liquid crystal panel 60 is suppressed.

Adjustment of the moisture evaporation rate of a polarizing plate can be performed by selecting the protective films 23 and 33 located in the side far from the liquid crystal cell 10 of the polarizing plates 20 and 30. FIG. Moisture evaporation rate by using a polypropylene resin film, a polyethylene terephthalate resin film or an acrylic resin film having a low moisture permeability on the front side polarizing plate 20, and a cellulose resin film having a high moisture permeability on the back side polarizing plate 30. A liquid crystal display device satisfying the relationship of is obtained.

[Backlight unit]

The backlight unit 70 includes a light source member for supplying light for display to at least the liquid crystal cell 10. This light source member has a form called a side light type composed of a light guide plate and a light source disposed on one side or an opposite side of the light guide plate, but includes a plurality of light sources and light diffusing disposed on the upper side (the side facing the liquid crystal cell 10). It may be in the form of a direct type consisting of plates. In any form, a light reflection layer is usually formed in the form of a sheet or an application layer on the rear surface of the light source member (side away from the liquid crystal cell 10). Further, one or more layers of optical members such as a light collecting sheet and a diffusion film may be arranged on the light exit side (side toward the liquid crystal cell 10) of the light source member. The backlight unit 70 itself has each member described herein, and can be any configuration employed in the field.

[Example]

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited by these examples. In the examples, parts and percentages indicating content to amount used are based on weight unless otherwise specified. In addition, in the following example, each physical property was measured by the following method.

(1) thickness measurement:

The thickness was measured using the digital micrometer "MH-15M" by Nikon Corporation.

(2) Measurement of in-plane retardation and thickness direction retardation:

In-plane retardation and thickness direction retardation at wavelength of 590 nm were measured at 23 degreeC temperature using the retarder "KOBRA-21ADH" based on the parallel Nicole rotation method by Prince Instrument Co., Ltd.

(3) Measurement of moisture evaporation rate:

The adhesive imparting polarizing plate cut to 95 mm x 95 mm was bonded to the 100 mm x 100 mm soda glass board by the adhesive side. Then, the polarizing plate bonded to the glass plate was allowed to stand for 96 hours in an environment having a temperature of 40 ° C. and a relative humidity of 95%, and then absorbed. The weight W ₁ (unit: g) immediately after taking out and taking out to room temperature was measured. In addition, the weight W ₂ (unit: g) immediately after the polarizing plate after bonding to a glass plate in the humid heat environment and making it moisture-absorbed was left to stand in the environment of temperature 50 degreeC and 0% of relative humidity for 1 hour, was taken out to room temperature environment, and taken out. From these values, the water evaporation rate C (g / m ² · hr) was obtained by the following equation.

C = (W ₁ -W ₂ ) / (0.095) ²

(4) Measurement of warpage amount of liquid crystal panel

The liquid crystal display device comprised by combining the liquid crystal panel 60 and the backlight unit 70 was left to stand in a 40 degreeC temperature and 95% of relative humidity environment for 96 hours, then taken out to room temperature environment, and the backlight was left to stand for 1 hour. After that, as shown in FIG. 3, a thread 65 connecting from one corner of the case constituting the liquid crystal panel 60 to the corner in the diagonal direction is connected, and the other thread 66 is also in the other diagonal direction. ). Using the seals 65 and 66 as a reference line, the vertical distance L from the center of the liquid crystal panel 60 to the reference line from the center portion of the liquid crystal panel 60 was measured and set as the amount of warpage.

(5) Measurement of in-plane luminance difference of liquid crystal panel:

The liquid crystal display device configured by combining the liquid crystal panel 60 and the backlight unit 70 was placed in an environment having a temperature of 40 ° C. and a relative humidity of 95% for 96 hours, then taken out to a room temperature environment, and the backlight was turned on for 1 hour. Thereafter, the in-plane of the liquid crystal panel 60 was divided into a lattice shape to measure 17 points in the short side direction and 31 points in the long side direction, and a total of 527 points were measured by the luminance-color spectrometer "EyeScale" manufactured by ISystem. The luminance measurement was performed using -3W ", and the difference between the maximum value and the minimum value was made into the in-plane luminance difference.

Reference Example 1 (Preparation of Aqueous Adhesive)

3 parts of "KL-318" (brand name) which is a carboxyl group-modified polyvinyl alcohol obtained from Curare Co., Ltd. were dissolved with respect to 100 parts of water, and the aqueous solution obtained from Sumitomo Chemtex Co., Ltd. was dissolved in the aqueous solution. 1.5 parts of "Sumirez resin 650 (30)" (brand name, aqueous solution of 30% of solid content concentration) which is a polyamide epoxy resin was added, and the water-based adhesive agent was prepared.

Reference Example 2 (Preparation of an Adhesive Made of a Curable Epoxy Resin Composition)

100 parts of bis (3,4-epoxycyclohexylmethyl) azipeto, 25 parts of diglycyl ether of water-added bisphenol A, and 4,4'-bis (difaxulfone) diphenylsulfonebis (as photocationic polymerization initiator After 2.2 parts of hexafluorophosphate) were mixed, it was defoamed and the adhesive agent which becomes a curable epoxy resin composition was prepared. In addition, the photocationic polymerization initiator was mix | blended as a 50% fluropyrene carbonone solution. 2.2 parts of compounding quantities shown here are the quantity of solid content (photocationic polymerization initiator itself) except a fluoropyrene carboneto.

Reference Example 3 (Preparation of Polarizing Plate 1 with Adhesive)

An adhesive made of a curable epoxy resin composition prepared in Reference Example 2 was applied to one side of a 28 μm-thick polarizing film in which urea was adsorbed and oriented to polyvinyl alcohol, and 38 μm of corona treated with an irradiation dose of 16.8 kJ / m ² . "Conica Minolta" is a 40-μm-triacetyl cellulose film that is corona-treated at an irradiation dose of 16.8 kJ / m ² with an adhesive made of the same curable epoxy resin composition on the other side by bonding a monoaxially stretched polyethylene terephthalate film of The film which is a brand name "KC4UEW" of "Opter Co., Ltd.", in-plane retardation 0.7 nm, and thickness direction retardation -0.1 nm was bonded. Subsequently, ultraviolet rays were irradiated with an integrated light quantity of 1,000 mJ / cm ² using an ultraviolet irradiation device (lamp is a "Fusion D lamp") on the triacetyl cellulose film side, and left at room temperature for 1 hour to produce a polarizing plate. . And after performing the corona treatment with the irradiation amount of 16.8kJ / m <^2> on the surface of the said triacetyl cellulose film, the acrylic adhesive sheet was bonded to the corona treatment surface, and the polarizing plate 1 with an adhesive was produced. The polarizing plate 1 with pressure-sensitive adhesive showed a good appearance without the lifting of the film, bubbles or the like. The water vaporization rate C of the pressure sensitive adhesive polarizing plate 1 was 1.69 g / m ² · hr.

Reference Example 4 (Preparation of Polarizing Plate 2 with Adhesive)

On one side of the polarizing film as used in Reference Example 3, a water-based adhesive prepared in Reference Example 1 was applied, and the product name "KC8UX" of "Konica Minolta Opter", a triacetyl cellulose film having a thickness of 80 μm, was subjected to saponification treatment. "KC4UEW" of "Konica Minolta Opter Co., Ltd." which is a triacetyl cellulose film having a thickness of 40 µm subjected to saponification by applying the same water-based adhesive on the other side, and in-plane retardation 0.7 nm, thickness After bonding direction retardation -0.1 nm, it dried for 80 minutes for 80 minutes, and produced the polarizing plate. Next, after performing a corona treatment with the irradiation amount of 16.8kJ / m < ² > on the surface of 40 micrometer triacetyl cellulose film side, the adhesive sheet like what was employ | adopted in the reference example 3 was bonded to the corona treatment surface, and the polarizing plate 2 with an adhesive was made into Made. The polarizing plate 1 with pressure-sensitive adhesive showed a good appearance without the lifting of the film, bubbles or the like. The water vaporization rate C of the pressure sensitive adhesive polarizing plate 2 was 9.72 g / m ² · hr.

EXAMPLE 1

(Cutting of polarizing plate with adhesive)

The polarizing plate 1 with pressure-sensitive adhesive produced in Reference Example 3 was cut into a 32 type size (32 inches diagonally (about 81 cm), approximately 71 cm wide x approximately 40 cm long] so that the absorption axis was parallel to the long side, and the liquid crystal cell 10 The front side (viewing side) of the polarizing plate 20 was set. Moreover, the polarizing plate 2 with an adhesive produced in Reference Example 4 was cut to the above 32 type size so that the absorption axis was parallel to the short side, and the back side (backlight side) polarizing plate 30 of the liquid crystal cell 10 was used. This polarizing plate showed favorable handling property at the time of handling.

(Production of LCD)

Panasonic IPS mode wide 32 type [32 inches diagonal (approx. 81 cm), width 71 cm x width 40 cm] LCD TV "VIERA" (model number: VIERA TH-L32X1) is disassembled and the upper and lower polarizers of the liquid crystal cell The polarizing plate 1 with the adhesive layer peeled off and cut | disconnected above was arrange | positioned so that it might be parallel to the orientation direction at the time of voltage-free (black display) of the liquid crystal molecule in the liquid crystal cell 10 as the front side (viewing side) polarizing plate 20. Moreover, the polarizing plate 2 with an adhesive layer cut out above is the back side (backlight side) polarizing plate 30 of the liquid crystal cell 10, The absorption axis is bonded orthogonally to the absorption axis of the front side polarizing plate 20, and a liquid crystal is carried out. The panel 60 was produced. At this time, the ratio between the water evaporation rate V _f of the front side polarizing plate 20 and the water evaporation rate V _r of the back side polarizing plate 30, V _f / V _r is 1.69 / 9.72 = 0.17. The liquid crystal panel 60 was combined with the original backlight unit 70 to assemble the liquid crystal display device. After leaving the liquid crystal display device for 96 hours in an environment of 40 ° C and 95% relative humidity, the liquid crystal display device is taken out at room temperature, and the backlight 70 is turned on to measure the in-plane luminance difference of the liquid crystal panel 60 after 1 hour. As a result, the in-plane luminance difference was 2.20 cd / cm ² , and no visible stains were observed on the naked eye.

[Comparative Example 1]

As the front side polarizing plate 20 and the back side polarizing plate 30, the liquid crystal panel 60 was produced by the method similar to Example 1 except having employ | adopted the polarizing plate 2 with an adhesive produced by the reference example 4 altogether. At this time, the ratio between the water evaporation rate V _f of the front side polarizing plate 20 and the water evaporation rate V _r of the back side polarizing plate 30 is Vf / Vr. This liquid crystal panel 60 was combined with the original backlight unit 70, and the liquid crystal display device was assembled. After leaving the liquid crystal display device for 96 hours in an environment of 40 ° C and 95% relative humidity, the liquid crystal display device is taken out at room temperature, and the backlight 70 is turned on to measure the in-plane luminance difference of the liquid crystal panel 60 after 1 hour. As a result, the in-plane luminance difference was 6.55 cd / cm ² , and the stain was visually confirmed.

Comparative Example 2

Example 1 except having comprised the front side polarizing plate 20 from the polarizing plate 2 with an adhesive produced in the reference example 4, and the back side polarizing plate 30 from the polarizing plate 1 with the adhesive layer produced in the reference example 3. The liquid crystal panel 60 was produced by the method similar to the above. At this time, the ratio between the water evaporation rate V _f of the front side polarizing plate 20 and the water evaporation rate V _r of the rear side polarizing plate 30, V _f / V _r is 5.75. This liquid crystal panel 60 was combined with the original backlight unit 70, and the liquid crystal display device was assembled. After leaving the liquid crystal display device for 96 hours in an environment of 40 degrees temperature and 95% relative humidity, the liquid crystal display device was taken out at room temperature, the backlight was turned on, and after 1 hour, the in-plane luminance difference of the liquid crystal panel 60 was measured. The in-plane luminance difference was 5.90 cd / cm ² , and visible stains were observed by the naked eye.

Table 1 summarizes the water evaporation rate of the pressure-sensitive adhesive polarizing plate and its comparison and evaluation results in the above Examples and Comparative Examples.

No. Water evaporation rate of polarizer
(g / m ² · hr) V _f / V _r Amount of warpage
(mm) In-plane luminance difference
(cd / cm ² ) Splat stain V _f V _r Example 1 1.69 9.72 0.17 0.2 2.20 radish Comparative Example 1 9.72 9.72 One 2.5 6.55 U Comparative Example 2 9.72 1.69 5.75 2.3 5.90 U

10: liquid crystal cell
11,12: cell substrate
15: liquid crystal layer
20: front side polarizer
21: polarizing film
23,24: transparent protective film
30: back side polarizing plate
31: polarizing film
33,34: transparent protective film
36: first retardation film
37: second retardation film
38: core layer
39: skin layer
40: interlayer adhesive
51,52: pressure-sensitive adhesive layer
60: liquid crystal panel
70: backlight unit
65,66: Diagonal lines to measure the deflection of the liquid crystal panel
L: amount of warpage of the liquid crystal panel

Claims (10)

A liquid crystal cell having two cell substrates and a liquid crystal layer sandwiched therebetween,
The front side polarizing plate laminated | stacked through the adhesive layer in the visual recognition side of the said liquid crystal cell,
Back side polarizing plate laminated | stacked through the adhesive layer on the opposite side to the visual recognition side of the said liquid crystal cell, And
A backlight unit disposed outside the rear polarizer;
The front side polarizing plate and the back side polarizing plate each have a polarizing film and a transparent protective film disposed on both sides thereof, and
The ratio between the water evaporation rate (V _f ) of the front side polarizing plate having the pressure-sensitive adhesive layer and the water evaporation rate (V _r ) of the back side polarizing plate having the pressure-sensitive adhesive layer, V _f / V _r is in the range of more than 0 and less than 1 A liquid crystal display device, characterized in that. The liquid crystal display device according to claim 1, wherein the transparent protective film located on a side far from the liquid crystal cell of the front side polarizing plate is made of polypropylene resin, polyethylene terephthalate resin or acrylic resin. The liquid crystal display device according to claim 1 or 2, wherein the transparent protective film located on a side far from the liquid crystal cell of the back side polarizing plate is made of cellulose resin. The transparent protective film of Claim 1 or 2 located in the liquid crystal cell side of each said front side polarizing plate and said back side polarizing plate has the thickness direction retardation (Rth) in the range of -10- + 10 nm. A liquid crystal display device, characterized in that. The transparent protective film positioned on the liquid crystal cell side of each of the front side polarizing plate and the back side polarizing plate, one of which has a thickness direction retardation (Rth) in a range of -10 to +10 nm. On the other hand, the in-plane retardation (Ro) is in the range of 100 to 300 nm, the refractive index in the slow axis direction in the film plane is n _x , the refractive index in the fast axis direction in the film plane is n _y , and the film thickness direction When the refractive index is set to n _z , the N _z coefficient defined by the formula (n _x -n _z ) / (n _x -n _y ) is in the range of 0.1 to 0.7. The thickness direction retardation (Rth) of the transparent protective film which is located in the liquid crystal cell side of each said front side polarizing plate and said back side polarizing plate, The thickness direction retardation (Rth) is a range of -10- + 10 nm. In the
The other is located in the polarizing film side which comprises the polarizing plate, and is located in the said adhesive layer side rather than the 1st retardation film which consists of polyolefin resin, and the said 1st retardation film, The core layer which consists of styrene resin, and the core layer of It is a laminated body of the 2nd phase difference film which has a 3-layered structure which consists of a skin layer which consists of a (meth) acrylic-type resin composition containing the rubber particle laminated | stacked on both surfaces, The liquid crystal display device characterized by the above-mentioned. The in-plane retardation (Ro) is in the range of 30 to 150 nm, and the refractive index in the slow axis direction in the film plane is n _x , and the refractive index in the fast axis direction in the film plane is n. _y, and when the refractive index of the film thickness direction as n _z, n _z is the coefficient to be defined by the equation _{(n x -n z) / (} n x -n y) is in the range of less than 1 second,
The second retardation film has an in-plane retardation (Ro) in the range of 20 to 120 nm, and the N _z coefficient defined by the above formula is in the range of more than -2 to less than -0.5. At least one of the said front side polarizing plate and the said back side polarizing plate is a polarizing film and the transparent protective film arrange | positioned at both surfaces, The polyvinyl alcohol-type resin and water-soluble epoxy resin of Claim 1 or 2 contain it. A liquid crystal display device, which is bonded through an aqueous adhesive. The at least one of the said front side polarizing plate and the said back side polarizing plate contains the epoxy compound of Claim 1 or 2 in which a polarizing film and the transparent protective film arrange | positioned at both surfaces harden | cure by irradiation of an active energy ray. A liquid crystal display device, which is bonded through a curable adhesive composition. The liquid crystal display device according to claim 9, wherein the epoxy compound includes an epoxy compound having at least one epoxy group bonded to an alicyclic ring in a molecule thereof.

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