JP2003207630A - Elliptically polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elliptically polarizing plate which widens a viewing angle (in particular a viewing angle toward a downward direction) without increasing thickness of a liquid crystal panel, realizes a liquid crystal display device scarcely generating lowering of contrast caused by viewing angle variation, gray scale reversal or black and white reversal and hue variation and further is excellent in durability (maintaining a polarization degree of a polarizing element). <P>SOLUTION: In the elliptically polarizing plate provided with an optically compensating sheet consisting of an optically anisotropic layer formed of a transparent supporting body and a liquid crystalline compound, the polarizing element and a light scattering layer, moisture permeability of the optically compensating sheet is in the range of 100-1,000 g/m<SP>2</SP>/24 hr and the light scattering layer is a layer comprising a translucent resin in which a translucent diffusing agent with a refractive index different from that of the resin is dispersed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an elliptically polarizing plate having a transparent support, an optically anisotropic layer, a polarizing element and a light scattering layer, and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device comprises a polarizing plate and a liquid crystal cell. TN mode TF, which is currently mainstream
In the T liquid crystal display device, an optically anisotropic layer is inserted between a polarizing plate and a liquid crystal cell as described in JP-A-8-50206 to realize a liquid crystal display device with high display quality. However, this method has a problem that the liquid crystal display device itself becomes thick. Japanese Patent Application Laid-Open No. 1-68940 uses a elliptically polarizing plate having a retardation film on one surface of a polarizing element and a protective film on the other surface to increase front contrast without increasing the thickness of a liquid crystal display device. There is a statement that it is possible. However, it has been found that the retardation plate described in this publication easily causes a retardation due to strain such as heat.

To solve the problem of phase difference caused by distortion, Japanese Patent Laid-Open No. 7-191217 and European Patent 0911
In the specification of 656A2, a film in which an optically anisotropic layer made of a discotic liquid crystal is coated on a transparent support is directly used as a protective film for a polarizing plate, so that the liquid crystal display device is not thickened. Solved the problem of phase difference. However, the above liquid crystal display device has a problem that gray scale inversion occurs in the downward direction of the panel, and a liquid crystal display device using a polarizing plate in which a film coated with an optically anisotropic layer and a polarizing element are integrated has a wide viewing angle. However, there is a problem that the degree of polarization of the polarizing element decreases with the passage of time, the black brightness of the liquid crystal display increases, and the contrast decreases.

[0004]

The object of the present invention is to provide excellent optical compensation characteristics (especially, the downward viewing angle is increased) without increasing the thickness of the liquid crystal panel, to reduce the contrast due to the change of the viewing angle, to reduce the gradation or It is an object of the present invention to provide an elliptically polarizing plate which can provide a liquid crystal display device in which black-and-white inversion and hue change hardly occur and which is excellent in durability (maintaining the polarization degree of a polarizing element). Another object of the present invention is to provide a liquid crystal display device having an elliptically polarizing plate excellent in the above performance.

[0005]

The object of the present invention has been achieved by an elliptically polarizing plate having the following constitution and a liquid crystal display device using the same. 1. In an optical compensation sheet having an optically anisotropic layer formed of a transparent support and a liquid crystalline compound, a polarizing element, and an elliptically polarizing plate having a light scattering layer, the optical compensation sheet has a water vapor transmission rate of 100 to 1000 g / m ² / The elliptically polarizing plate having a range of 24 hours, wherein the light scattering layer is a layer in which a light transmissive diffusing agent having a refractive index different from that of the resin is dispersed in a light transmissive resin. 2. The internal haze value hi due to internal diffusion of the light scattering layer is 0 to
95. The elliptically polarizing plate as described in 1 above, which is 95. 3. The surface haze value hs on the surface irregularities of the light scattering layer is more than 0.5 and less than 30.
2. The elliptically polarizing plate according to any one of 2. 4. The sum of the surface haze value hs on the surface irregularities of the light scattering layer and the internal haze value hi due to internal diffusion of the light scattering layer is 30.
The elliptically polarizing plate as described in 3 above, which is the above. 5. The elliptically polarizing plate according to any one of the above 1 to 4, wherein the surface roughness Ra of the surface irregularities of the light scattering layer is 1.2 μm or less. 6. The difference Δn in refractive index between the transparent resin and the transparent diffusing agent in the light scattering layer is 0.01 to 0.8, and the average particle diameter d of the transparent diffusing agent is 0.1 to 5 μm. 6. The elliptically polarizing plate according to any one of 1 to 5 above, which is characterized in that. 7. 7. The elliptically polarizing plate according to any one of 1 to 6 above, wherein the liquid crystal compound is a discotic liquid crystal compound. 8. The transparent support contains cellulose acetate having an acetylation degree of 59.0 to 61.5%, and 0.01 to 20 aromatic compounds having at least two aromatic rings with respect to 100 parts by mass of cellulose acetate. The elliptically polarizing plate according to any one of 1 to 7 above, which comprises a mass part. 9. 9. The elliptically polarizing plate according to any one of 1 to 8 above, which has at least one transparent support between the optically anisotropic layer and the polarizing element and between the polarizing element and the light scattering layer. 10. 10. A liquid crystal display device, wherein the elliptically polarizing plate described in any one of 1 to 9 above is arranged on the liquid crystal cell surface on the side of the optically anisotropic layer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The elliptically polarizing plate of the present invention has a transparent support and an optically anisotropic layer containing a liquid crystalline compound, a polarizing element, and a light scattering layer as constituent layers. FIG. 1 schematically shows a schematic cross-sectional view of the layer structure of a preferable elliptically polarizing plate of the present invention. The light scattering layer 5 is formed on one surface (upper surface in the figure) of the transparent support 2.
On the opposite side of the transparent support (bottom surface in the figure)
The polarizing element 6, the transparent support 7 and the optically anisotropic layer 8 are laminated on the above. An alignment film 9 may be provided between the transparent support 7 and the optically anisotropic layer 8. The layer structure of the elliptically polarizing plate of the present invention is not limited to that shown in FIG. 1, and it goes without saying that there are many variations. Hereinafter, each layer constituting the elliptically polarizing plate of the present invention will be described based on FIG.

The optically anisotropic layer 8 constituting the elliptically polarizing plate of the present invention will be described. [Optically Anisotropic Layer] The optically anisotropic layer 8 is formed of a liquid crystal compound. (Liquid Crystal Compound) As the liquid crystal compound used in the elliptically polarizing plate of the present invention, a discotic liquid crystal compound is preferably used. Examples of the discotic liquid crystal compound include C.I. Report of Destrade et al., Mol.
Cryst. 71, page 111 (1981), benzene derivatives, C.I. Report of Destrade et al., Mol. Cryst. Volume 122, page 141 (1
1985), Physics lett, A, Vol. 78,
82 (1990), a truxene derivative described in B. Kohne et al., Angew. Che
m. 96, 70 (1984), and cyclohexane derivatives described in J. M. Lehn et al.'S research report,
J. Chem. Commun. , Pp. 1794 (1985
Year), J. Research report by Zhang et al. Am. Che
m. Soc. 116, pp. 2655 (1994), such as azacrown type and phenylacetylene type macrocycles. Discotic liquid crystalline compounds generally have a structure in which linear alkyl groups, alkoxy groups, substituted benzoyloxy groups, and the like are radially substituted as linear chains with these as the mother nucleus of the molecular center, and liquid crystalline Indicates. However, it is not limited to the above description as long as the molecule itself has negative uniaxiality and can impart a certain orientation.

Further, in the present invention, the "liquid crystalline compound" of the optically anisotropic layer formed of the liquid crystalline compound is required to be liquid crystalline in the optically anisotropic layer constituting the elliptically polarizing plate of the present invention. However, for example, the low molecular weight discotic liquid crystal compound has a group that reacts with heat, light, etc.,
As a result, an optically anisotropic layer may be formed by polymerizing or crosslinking by reaction with heat, light, etc., and having a high molecular weight to lose liquid crystallinity. A preferred example of the discotic liquid crystal is described in JP-A-8-50206.

In the optically anisotropic layer constituting the elliptically polarizing plate of the present invention, the disc surface of the discotic liquid crystal compound is preferably inclined with respect to the transparent support surface and the angle formed by the transparent support surface is It is preferred that the depth is changed in the optically anisotropic layer.

The disc surface angle (tilt angle) of the discotic liquid crystalline compound generally increases or decreases in the depth direction of the optically anisotropic layer and as the distance from the bottom surface of the optically anisotropic layer increases. ing. The tilt angle preferably increases with increasing distance. Further, examples of the change in the tilt angle include continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and decrease, and intermittent change including increase and decrease. it can. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. The tilt angle includes a region that does not change,
It is preferably increased or decreased as a whole. Furthermore, it is preferable that the inclination angle is increased as a whole,
It is particularly preferable that the change is continuous.

The above-mentioned optically anisotropic layer is generally prepared by applying a solution of a discotic liquid crystal compound and another compound dissolved in a solvent onto the alignment film, drying and then heating to a discotic nematic phase forming temperature, and then It is obtained by cooling while maintaining the orientation state (discotic nematic phase). Alternatively, the optically anisotropic layer may be prepared by applying a solution of a discotic liquid crystal compound and another compound (further, for example, a polymerizable monomer or a photopolymerization initiator) dissolved in a solvent onto the alignment film, followed by drying, After heating to the discotic nematic phase formation temperature, polymerize (U
(For example, irradiation with V light) and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C., and particularly 70 to 170.
C is preferred.

The tilt angle of the optically anisotropic layer on the transparent support 7 side can be adjusted by generally selecting the discotic liquid crystal compound or the material of the alignment film, or by selecting the rubbing treatment method. it can. In addition, for the tilt angle on the opposite surface side (air side), generally select a discotic liquid crystal compound or another compound used together with the discotic liquid crystal (eg, plasticizer, surfactant, polymerizable monomer and polymer). Can be adjusted by. Further, the degree of change in the tilt angle can be adjusted by the above selection.

As the plasticizer, the surfactant and the polymerizable monomer, any compound can be used as long as it is compatible with the discotic liquid crystal compound and does not hinder the alignment of the discotic liquid crystal compound. it can. Of these, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) are preferable. The above compound is generally contained in an amount of 1 to 50% by mass (preferably 5 to 3%) based on the discotic liquid crystal.
0% by weight).

As the above-mentioned polymer used together with the discotic liquid crystal compound, any polymer can be used as long as it is compatible with the discotic liquid crystal compound and does not hinder the alignment. Cellulose ester can be mentioned as an example of a polymer.
Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The polymer is generally 0.1 to 10% by mass with respect to the discotic liquid crystal.
(Preferably 0.1 to 8% by mass, particularly preferably 0.1
~ 5% by weight).

The optically anisotropic layer formed of the liquid crystalline compound used in the present invention is disposed on the cellulose acetate film as the transparent support 7 and the alignment film provided thereon. The alignment film is a rubbing-processed film made of a crosslinked polymer. Preferable examples of the alignment film 9 used in the present invention include the structure shown in FIG.
The alignment film described in JP-A-152509 may be mentioned.

[Transparent Support] As the transparent support of the present invention, it is preferable to use a polymer film having a light transmittance of 80% or more. As the polymer film, a cellulose-based polymer film such as cellulose acetate or acetate butyrate cellulose, a norbornene-based polymer film (eg, Arton, manufactured by JSR Co., Ltd.); ZEONOR, manufactured by ZEON CORPORATION; ZEONEX, ZEON CORPORATION )) And polyacrylic resin film such as polymethylmethacrylate, polyurethane resin film, polyethersulfone film, polyester film, polycarbonate film polysulfone film, polyether film, polymethylpentene film polyetherketone film, etc. . Among the above polymer films, a cellulosic polymer is preferable, a cellulose ester is more preferable, and a lower fatty acid ester of cellulose is further preferable. The lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). The cellulose ester is preferably cellulose acetate, and examples thereof include diacetyl cellulose and triacetyl cellulose. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Generally, cellulose acetate 2,
The hydroxyl groups of 3 and 6 are not evenly distributed in 1/3 of the entire substitution degree, and the substitution degree of the 6-position hydroxyl group tends to be small. In the present invention, it is preferable that the substitution degree of the 6-position hydroxyl group of cellulose acetate is higher than those of the 2- and 3-position hydroxyl groups. 30% or more of the 6-position hydroxyl groups relative to the total degree of substitution 4
It is preferably 0% or less and substituted with an acyl group, more preferably 31% or more, and particularly preferably 32% or more. Further, the substitution degree of the 6-position acyl group of cellulose acetate is preferably 0.88 or more. The 6-position hydroxyl group may be substituted with an acyl group having 3 or more carbon atoms, such as a propionyl group, a butyroyl group, a valeroyl group, a benzoyl group, and an acryloyl group, in addition to the acetyl group. The substitution degree at each position can be measured by NMR. As the cellulose acetate of the present invention, JP-A-11
No. 5851-Synthesis Example 1 described in paragraphs 0043 to 0044, Synthesis No. 2 described in paragraphs 0048 to 0049, and paragraphs 0051 to 00
The cellulose acetate obtained by the synthesis method of Synthesis Example 3 described in 52 can be used.

[Production of Transparent Support] The case where a cellulose acetate film is used will be specifically described below. It is preferable to produce the cellulose acetate film by the solvent casting method. In the solvent cast method, a film is manufactured using a solution (dope) in which cellulose acetate is dissolved in an organic solvent. It is common to use a halogenated hydrocarbon such as methylene chloride as the organic solvent, but the Technical Report of the Invention Society of Japan (Jpn. Pat. No. 2001-1745, published on Mar. 15, 2001; (Abbreviated as No. 1745) No. 12
The organic solvents described on pages 15 to 15 can be used. Although halogenated hydrocarbons such as methylene chloride can be used without any technical problems, it is preferable that the organic solvent does not substantially contain halogenated hydrocarbons from the viewpoint of the global environment and working environment. "Substantially free" means that the proportion of halogenated hydrocarbon in the organic solvent is less than 5% by mass (preferably less than 2% by mass). Further, it is preferable that halogenated hydrocarbons are not detected in the produced cellulose acetate film. Also, when halogenated hydrocarbons such as methylene chloride are used, it is common to recover the solvent from the manufacturing process. "Plastic Reader" Osaka Municipal Industrial Research Institute Plastic Reader Editorial Committee, Plastic Technology Association It is described in many textbooks such as the co-editing (1992).

The preparation and filtration method of the cellulose acetate solution is disclosed in JP-A-2001-1745, No. 22.
The methods described on pages 25 to 25 can be used.

A cellulose acetate film is produced from the prepared cellulose acetate solution (dope) by a solvent casting method, and it is preferable to add a retardation increasing agent described later to the dope. The manufacturing process includes processes such as casting, drying, and stretching. These processes are specifically described in pages 25 to 29 of Kokai Giho 2001-1745.

Further, the cellulose acetate solution of the present invention is disclosed in Published Technical Report 2001-1745, pages 25 to 29.
Other functional layers (eg adhesive layers, dye layers, antistatic layers, antihalation layers, UV, etc.
Casting (co-casting) absorption layer, polarizing layer, etc. simultaneously.
Things can also be done.

The cellulose acetate film of the present invention can be used in the open technical report 2001-1745, pages 15 to 22.
Various additives as described on the page (for example, a plasticizer, a UV inhibitor, a deterioration inhibitor, fine particles, an optical property adjusting agent, etc.) can be added. As the optical property adjusting agent, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent in order to adjust the retardation of the polymer film. Specific examples of the retardation increasing agent include JP-A-2000-11 in addition to JP-A-2001-1745.
1914, 2000-275434, P.
It is described in the specification of CT / JP00 / 02619 and the like.

[Surface Treatment of Transparent Support] The cellulose acetate film of the present invention is preferably surface-treated in advance. As the surface treatment, corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment or ultraviolet irradiation treatment is carried out. Particularly, it is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment for the transparent support in order to enhance the adhesion to the alignment film described later. Regarding these surface treatments, open technical report 200
The method described in No. 1-1745, pages 29 to 30 can be used.

[Undercoating of transparent support] The cellulose acetate film of the present invention may be undercoated in advance. For the undercoat, the method described in JP-A No. 2001-1745, pages 30 to 31 can be used.

[Moisture Permeability Control] The deterioration of the display performance of the liquid crystal display device is caused by the entry of water into the polarizing element of the elliptically polarizing plate described later used in the liquid crystal display device. This water may remain after manufacturing the elliptically polarizing plate, or may be water in the atmosphere existing in the usage environment of the liquid crystal display device. In elliptically polarizing plate integrated optical compensation sheet and a polarizing element of the present invention, the moisture permeability of the optical compensation sheet 100 to 1000g / m ² / 24hr
Is preferably, 300 to 700g / m ^2/2
More preferably, it is 4 hours. In order to integrate the optical compensation sheet and the polarizing element when manufacturing an elliptically polarizing plate,
It is general that the solvent is fixed by an adhesive (including an adhesive) containing water as a main component. After integrating the two via an adhesive, the water contained in the adhesive passes through the transparent support and is released to the outside of the elliptically polarizing plate.
Adhesive force is developed, and the transparent support and the polarizing element are bonded together.
Therefore, if the moisture permeability of the transparent support is too low, the water contained in the adhesive remains between the transparent support and the polarizing element.
Moisture remaining in the elliptically polarizing plate enters the polarizing element and reduces the polarizing ability of the polarizing element. On the other hand, if the moisture permeability of the transparent support is too high, moisture in the environment where the elliptically polarizing plate is placed enters the elliptically polarizing plate. The moisture enters the polarizing element and reduces the polarizing ability of the polarizing element. Further, in terms of manufacturing the elliptically polarizing plate, it is more productive that the moisture contained in the adhesive quickly permeates through the transparent support.

The water vapor permeability can be adjusted by the thickness of the transparent support (and the liquid crystalline compound), the free volume, and the amount of the additive (hydrophilicity / hydrophobicity) added to the transparent support. Since the water vapor transmission rate varies depending on the type of the transparent support, it is possible to adjust the water vapor transmission rate to a preferable range by adjusting these. The method of adjusting the moisture permeability by adding an additive to the transparent support is a preferable method because the moisture permeability can be adjusted while maintaining the thickness and mechanical properties of the transparent support. The thickness of the transparent support can be easily adjusted by the production conditions (for example, in the case of the solvent casting method, lip flow rate, line speed, solid content concentration of dope, etc.). Further, the thickness of the transparent support can be adjusted by mechanically stretching or compressing the transparent support after it is formed. Since the water vapor transmission rate varies depending on the material of the transparent support, the water vapor transmission rate can be set within a preferable range by adjusting the thickness. The free volume of the transparent support can be adjusted by the production conditions (for example, in the case of the solvent cast method, the dope drying temperature or the drying time). Also in this case, the water vapor transmission rate varies depending on the material of the transparent support, so that the water vapor transmission rate can be set within a preferable range by adjusting the free volume. The moisture permeability can be adjusted by adding a hydrophilic / hydrophobic additive to the transparent support. The moisture permeability can be adjusted high by adding a hydrophilic additive, while the moisture permeability can be adjusted low by adding a hydrophobic additive. Further, the retardation increasing agent described above also functions as an additive for adjusting the moisture permeability.
An aromatic heterocycle is preferably used as the retardation increasing agent. Further, the aromatic heterocycle is 1,
It is preferably a 3,5-triazine ring. The method of measuring the moisture vapor transmission rate is described in "Physical Properties of Polymers II" (Polymer Experiment Course 4 Kyoritsu Shuppan), pages 285 to 294: Measurement of vapor permeation amount (gravimetric method, thermometer method, vapor pressure method, adsorption method) The method described in can be applied. In the examples herein, J
According to IS standard JISZ0208, B condition, the temperature is 40
The measurement was performed at 90 ° C. and humidity of 90% RH.

[Light-Scattering Layer] The light-scattering layer 5 provided in the elliptically polarizing plate of the present invention diffuses light and is combined with the following optically anisotropic layer to expand the downward viewing angle of a liquid crystal display. It is a layer for. As described above, the light-scattering layer 5 is a light-scattering layer in which a light-transmitting diffuser having a refractive index different from that of the resin is dispersed in a light-transmitting resin, which is a so-called internal light-scattering layer. With such a structure, it may have a refractive index distribution inside. Such a light-scattering layer 5 is described, for example, in JP-A-11-305010. The method of using the internal scattering layer in the elliptically polarizing plate of the present invention will be specifically described.

The internal haze value hi of the light scattering layer 5 is preferably 0 to 95, whereby the downward viewing angle of the liquid crystal display device can be improved and the glare can be reduced. Here, the “glare” is so-called scintillation, and refers to a phenomenon in which a glittering shine occurs. The lower the haze value hs on the surface of the light scattering layer 5, the smaller the blurring of the display, and the clearer the display can be obtained. However, if the haze value is too low, glare and surface glare occur. On the other hand, if it is too high, it becomes whitish; whitening decreases). The surface haze value hs is preferably 0.5 or more and less than 30, more preferably 7 to 20, and most preferably 7 to 15. Further, even if the surface haze value hs is optimized, surface glare tends to occur when the internal haze value hi is low. From the viewpoint of reducing the occurrence of surface glare, the internal haze value hi of the light scattering layer 5 is
Is more preferably 30 to 95, still more preferably 35 to 9
It is 0.

Further, in the elliptically polarizing plate of the present invention, the light scattering layer 5 is formed so that the sum of the surface haze value hs and the internal haze value hi in the light scattering layer 5 becomes 30 or more, thereby causing surface glare. In terms of suppressing the above, a further great effect can be obtained.

The surface haze value hs can usually be set to a desired value by providing appropriate irregularities on the resin layer surface by the fine particles contained in the light scattering layer 5, and this is the preferred form.

Further, a coating solution comprising a mixture of a light transmissive diffusing agent 3 and a light transmissive resin 4 is applied to the transparent support 2, and the surface roughness is applied to the surface of the applied coating layer. Ra is a patterning film having fine irregularities of 1.2 μm or less,
When the light-transmissive resin 4 is an electron beam or ultraviolet curable resin, it is laminated so that the surface is in contact with the coating layer, and is cured by irradiating it with an electron beam or an ultraviolet ray through a patterning film. When the volatile resin 4 is a solvent-drying resin, the light-scattering layer 5 is obtained by heating and drying and then curing the patterning film.
By peeling from the surface, unevenness is formed on the surface of the light scattering layer, and the surface haze value hs can be set to a desired value. That is, by such a method, the surface roughness Ra previously formed on the patterning film on the surface of the light scattering layer 5 is 1.2 μ.
Fine irregularities of m or less are transferred.

In order to set the internal haze value hi, the surface haze value hs, and the sum of these values as described above, the refractive index of the light-transmissive resin 4 and the light-transmissive diffusing agent 3 constituting the light-scattering layer 5 are set.
It is preferable that the refractive index difference Δn is 0.01 to 0.8 and the average particle diameter d of the diffusing agent is 0.1 to 5 μm.

When the refractive index difference Δn is less than 0.01, a large amount of diffusing agent must be contained in the light-transmitting resin in order to exhibit the light diffusing property in the light scattering layer 5. By doing so, the adhesiveness of the light scattering layer 5 to the transparent support 2 and the coating suitability deteriorate. On the other hand, when Δn is larger than 0.8, the content of the translucent diffusion agent 3 in the translucent resin 4 becomes small, and the light scattering layer 5 having uniform and appropriate unevenness cannot be obtained. In any case, it is not preferable. When the average particle diameter d of the light transmissive diffusing agent 3 is less than 0.1 μm, it becomes difficult to disperse the light transmissive diffusing agent 3 in the light transmissive resin 4, and agglomeration occurs to cause uniform and appropriate surface unevenness It is not preferable because the light-scattering layer 5 having the structure cannot be formed. On the other hand, when d exceeds 5 μm, the diffusion effect inside the light scattering layer 5 decreases, the internal haze value decreases, surface glare occurs, and the film thickness further increases, so that in the manufacturing process of the light-transmitting resin 4. Curing shrinkage increases, causing troubles such as cracking and curling,
Not preferable.

As a method of adjusting the internal haze value hi, the surface haze value hs and the sum of these values as described above, for example, a filler (a ratio of the translucent diffusing agent 3 and the translucent resin 4) is used. Examples thereof include a method of adjusting the P) / binder (V) ratio, a method of adjusting the refractive index difference between P and V, and a method of adjusting the type of solvent.

The light-transmissive resin 4 constituting the light-scattering layer 5 is a resin which is cured mainly by ultraviolet rays or electron beams, that is, an ionizing radiation-curable resin, an ionizing radiation-curable resin, and a thermoplastic resin and a solvent. Three types of thermosetting resin are used. Here, the ionizing radiation curable resin, the ionizing radiation curable resin and the thermosetting resin mean a resin composition containing a monomer before curing as a film forming component, an oligomeric compound or a prepolymer. .

The film forming component of the ionizing radiation curable resin is
Preferably, those having an acrylate-based functional group, for example, a relatively low molecular weight polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd resin, spiro acetal resin, polybutadiene resin, polythiol polyene resin, polyvalent Oligomers or prepolymers such as (meth) arylates of polyfunctional compounds such as alcohols; and monofunctional monomers such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone as a reactive diluent. And polyfunctional monomers such as poly (methylolpropane) tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) actic acid. Used with a relatively large amount of rate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, etc. it can.

Further, in order to use the above ionizing radiation curable resin as an ultraviolet curable resin, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethylthiuram are used as photopolymerization initiators therein. Monosulfide, thioxanthone, and n-butylamine, triethylamine, poly-n-butylphosphine, or the like as a photosensitizer may be mixed.
Particularly in the present invention, it is preferable to mix urethane acrylate as the oligomer and dipentaerythritol hexa (meth) acrylate as the monomer.

Further, as the translucent resin 4 for forming the light scattering layer 5, the above ionizing radiation curable resin may contain a solvent dry type resin. A thermoplastic resin is mainly used as the solvent drying type resin. The type of the solvent-drying thermoplastic resin added to the ionizing radiation-curable resin is not particularly limited, but the TAC described below as the transparent support 2 is used.
When using a cellulosic resin such as, the solvent drying type resin contained in the ionizing radiation-curable resin is a cellulosic resin such as nitrocellulose, acetylcellulose, cellulose acetate propionate, ethyl hydroxyethyl cellulose, etc. It is advantageous in terms of transparency and transparency.

The reason is that, for example, when toluene, which is a preferred solvent for the above-mentioned cellulose resin, is used, it is transparent despite the use of toluene, which is a non-soluble solvent for the polyacetyl cellulose which is the transparent support 2. Support 2
Adhesion between the transparent support 2 and the coating resin can be improved even when a coating material containing this solvent-drying resin is applied to the toluene. This is because it does not dissolve, so the surface of the transparent support 2 does not whiten, and the transparency is maintained.

Further, there is an advantage that the ionizing radiation curable resin contains a solvent dry type resin as follows. When the ionizing radiation curable resin is applied to the transparent support 2 with a roll coater having a metering roll, the liquid residual resin film on the surface of the metering roll flows and becomes streaks or unevenness over time, and these are applied to the coated surface. Re-transferring causes defects such as streaks and unevenness on the coated surface, but by including a solvent drying type resin in the ionizing radiation curable resin composition as described above, such coating film defects on the coated surface can be prevented. You can

As a method for curing the ionizing radiation-curable resin as described above, the ionizing radiation-curable resin curing method can be an ordinary curing method, that is, an electron beam or an ultraviolet ray can be used for curing. Specifically, an electron beam having an energy of several tens of KeV is used, and in the case of ultraviolet curing, ultraviolet rays emitted from light rays of an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, carbon arc, xenon arc, a metal halide lamp, etc. Is available.

The thermoplastic resin mixed with the ionizing radiation curable resin includes phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin and melamine. -Urea co-condensation resin, silicon resin, polysiloxane resin, etc. are used, and if necessary, a crosslinking agent, a curing agent such as a polymerization initiator, a polymerization accelerator, a solvent, a viscosity modifier, etc. are used. To do.

As the translucent diffusing agent 3 to be contained in the light scattering layer 5, plastic beads are suitable, and particularly, the transparency is high, and the difference in the refractive index from the translucent resin 4 is the above-mentioned numerical value. Is preferred. As plastic beads,
Styrene beads (refractive index 1.59), melamine beads (refractive index 1.57), acrylic beads (refractive index 1.4)
9), acrylic-styrene beads (refractive index 1.54),
Polycarbonate beads, polyethylene beads, vinyl chloride beads, etc. are used. The particle size of these plastic beads is appropriately selected and used as described above. Of the above plastic beads, styrene beads are particularly preferably used.

When the translucent diffusing agent 3 as the organic filler as described above is added, the organic filler easily precipitates in the resin before curing, so an inorganic filler such as silica is added to prevent the precipitation. You may. It should be noted that the more the inorganic filler is added, the more effective it is in preventing the sedimentation of the organic filler, but it adversely affects the transparency of the coating film. Therefore, it is preferable to prevent the sedimentation by adding an inorganic filler having a particle diameter of 0.5 μm or less to the translucent resin 4 in an amount of less than 0.1% by mass so as not to impair the transparency of the coating film. You can
When the inorganic filler, which is an anti-settling agent for preventing the sedimentation of the organic filler, is not added, the organic filler is deposited on the bottom during the application to the transparent support 2, so it is necessary to stir it well and use it uniformly. Good.

Generally, the cured resin of the ionizing radiation curable resin has a refractive index of about 1.5, which is about the same as that of glass, but is used in comparison with the refractive index of the translucent diffusing agent 3. When the resin has a low refractive index, the light-transmitting resin 4 has TiO ₂ (refractive index: 2.3-
2.7), Y ₂ O ₃ (refractive index; 1.87), La ₂ O ₃ (refractive index; 1.95), ZrO ₂ (refractive index; 2.05), A
L ₂ O ₃ (refractive index: 1.63) or the like can be added to the extent that the diffusivity of the coating film can be maintained, and the refractive index can be increased and adjusted.

Examples of the material of the transparent support 2 on which the light scattering layer 5 is formed include transparent resin films, transparent resin plates, transparent resin sheets and transparent glass. As the transparent resin film, triacetate cellulose (TAC) film, polyethylene terephthalate (PET) film,
Diacetyl cellulose film, acetate butyrate cellulose film, polyether sulfone film,
Polyacrylic resin film, polyurethane resin film, polyester film, polycarbonate film, polysulfone film, polyether film, polymethylpentene film, polyetherketone film, (meth) acrylonitrile film and the like can be used. The thickness is usually about 25 to 1000 μm.

[Polarizing Element] Next, a polarizing element constituting the elliptically polarizing plate of the present invention will be described. Examples of the polarization element include an iodine polarization element, a dye polarization element using a dichroic dye, and a polyene polarization element. The iodine type polarizing element and the dye type polarizing element can be generally manufactured using a polyvinyl alcohol type film.

[Other Layers Constituting Elliptical Polarizing Plate] As the elliptically polarizing plate, it is preferable to dispose two transparent protective films on both sides of the polarizing element. One of these protective films is the above-mentioned cellulose acetate film which is preferably used as the transparent support 7 of the optically anisotropic layer 8, and the other protective film is preferably used as the transparent support 2 of the light scattering layer 5. It is preferably a cellulose acetate film used. The slow axis of the cellulose acetate film as the protective film and the transmission axis of the polarizing element are arranged so as to be substantially parallel to each other.

[Liquid Crystal Display Device] The elliptically polarizing plate of the present invention is
It is advantageously used for liquid crystal display devices, particularly transmissive liquid crystal display devices. The transmissive liquid crystal display device includes a liquid crystal cell and two elliptically polarizing plates arranged on both sides of the liquid crystal cell. The liquid crystal cell is
A liquid crystal is carried between the two electrode substrates. The elliptically polarizing plate of the present invention is preferably used with its optically anisotropic layer disposed on the liquid crystal cell surface side. There are various modes in the liquid crystal cell. In the STN mode liquid crystal cell, rod-shaped liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and
It is twisted and oriented from 0 to 270 °. In the TN mode liquid crystal cell, rod-shaped liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and further twisted and aligned at 60 to 120 °. The STN mode and TN mode liquid crystal cells are most frequently used as black and white and color liquid crystal display devices, and are described in many documents. In a VA mode liquid crystal cell, rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied. For VA mode liquid crystal cells,
(1) In addition to a VA mode liquid crystal cell in the narrow sense (described in JP-A-2-176625) in which rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied and are aligned substantially horizontally when voltage is applied. , (2) Liquid crystal cell (SID97, Digest of tech. Papers (preliminary collection)) in which VA mode is multi-domain (MVA mode) to widen the viewing angle 28
(1997) 845), and (3) a liquid crystal cell of a mode (n-ASM mode) (n-ASM mode) in which rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied, and twisted in a multi-domain alignment when a voltage is applied. Proceedings 58-59
(1998)) and (4) SURVAIVAL mode liquid crystal cell (announced at LCD International 98). The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-shaped liquid crystal molecules are aligned in substantially opposite directions (symmetrically) in an upper portion and a lower portion of the liquid crystal cell. Patent 4583825
No. 5,410,422.
Since the rod-shaped liquid crystalline molecules are symmetrically aligned in the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is
It is also called OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed. In the ECB mode liquid crystal cell, rod-shaped liquid crystal molecules are substantially horizontally aligned when no voltage is applied. It is most widely used as a color TFT liquid crystal display device and is described in many documents. For example, "EL,
"PDP, LCD display" issued by Toray Search Center (2
001) and the like.

[0049]

The present invention will be specifically described below based on examples, but the present invention is not construed as being limited to the examples.

Example 1 Preparation of Optical Compensation Sheet (Preparation of Cellulose Acetate Film for Transparent Support)
As a transparent support of the present invention, open technical report 2001-174
No. 5. Page 63. Example 2. Sample 201 (abbreviation FF-2
01), and p. 56. Example 1. The cellulose acetate film of Sample 101 (abbreviation FF-101) was used.

Comparative Example 1 The following composition was put into a mixing tank and stirred with heating to dissolve each component to prepare a cycloolefin solution.

Cycloolefin solution composition ARTON (manufactured by JSR) 100 parts by mass Methylene chloride 400 parts by mass The obtained dope was cast using a band casting machine, and the thickness of the cycloolefin film was 50 μm (abbreviated as CY).
O) was produced.

(Preparation of Alignment Film Layer) (FF-201),
The (FF-101) and (CYO) films were immersed in a 1.5 N potassium hydroxide solution (40 ° C.) for 5 minutes, then neutralized with 0.5 N sulfuric acid at 30 ° C. for 30 seconds, and then pure at 30 ° C. It was washed with water for 5 minutes and dried at 100 ° C. for 2 minutes. Then, an alignment film coating solution having the following composition was applied at 28 ml / m ² with a # 16 wire bar coater. 6 with hot air at 60 ° C
It was dried for 0 seconds and further for 90 seconds with warm air of 90 ° C. next,
The formed film was rubbed in the longitudinal direction of the film.

[0054] Alignment film coating liquid composition -Modified polyvinyl alcohol having the following structure 8 parts by mass ・ PVA217 (made by Kuraray) 2 parts by mass ・ Water 371 parts by mass ・ Methanol 119 parts by mass ・ Glutaraldehyde (crosslinking agent) 0.5 parts by mass

[0055]

[Chemical 1]

(Formation of Optically Anisotropic Layer) 41.01 g of a discotic liquid crystal compound having the following structure, ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) was formed on the alignment film. 2.0
3 g, dipentaerythritol acrylate (KYARA
D DPHA Nippon Kayaku) 2.03 g, cellulose acetate butyrate (CAB551-0.2, Eastman Chemical Co.) 0.90 g, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co.) 0.23 g , A photopolymerization initiator (IRGACURE 90
7. Ciba Geigy Co., Ltd.) 1.35 g, sensitizer (Kayakyu DETX, Nippon Kayaku Co., Ltd.) 0.45 g 10
The coating solution dissolved in 2 g of methyl ethyl ketone was applied with a # 4 wire bar. This was heated in a constant temperature bath at 130 ° C. for 2 minutes to orient the discotic compound. Then 80
Under a ℃ atmosphere, the film surface temperature is about 100 ℃ 1
The discotic liquid crystal compound was polymerized by UV irradiation for 0.4 seconds using a 20 W / cm high pressure mercury lamp. Then, it stood to cool to room temperature. In this way, the optically anisotropic layer was formed. The cellulose acetate film obtained by laminating the optically anisotropic layer containing a liquid crystalline compound thus obtained was subjected to JIS Z0208 conditions (40 ° C., 90% RH).
Water vapor permeability was measured at (FF-201), (F
F-101), (CYO) resulting moisture permeability of the optical compensation sheet from the film, respectively 460g / m ² / 24h
^{r, 200g / m 2 / 24hr} , 2g / m 2 / 24hr
Met.

[0057]

[Chemical 2]

(Preparation of Elliptical Polarizing Plate) Iodine was adsorbed to a stretched polyvinyl alcohol film to prepare a polarizing element, and a polyvinyl alcohol adhesive was used to prepare (FF-201) and (FF-101). ), (CY
O) was attached to one side of the polarizing element, and to the other side, Fujitac TD80UF (manufactured by Fuji Photo Film Co., Ltd.) saponified as a transparent support was attached and dried at 80 ° C. for 10 minutes. The transmission axis of the polarizing element and the slow axis of the optically anisotropic layer produced above were arranged in parallel. The transmission axis of the polarizing element and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal to each other. In this way, the elliptically polarizing plates (Pol-A), (Pol-B), (Pol-A)
-C) was prepared.

(Production of Light-Scattering Layer Liquid) The light-scattering layer coating liquid (I) was prepared under the following conditions. Composition of light-scattering layer coating liquid (I) -PETA (product name PET30; Nippon Kayaku) 3.04 g-Styrene bead paste (product name SX-130; Soken Chemical Co., Ltd.) 1 g-10% CAP (diluted with ethyl acetate) 3. 64 g-Solvent (toluene, butyl acetate, isobutyl alcohol) 7.21 g-Photo-curing initiator (trade name: Irgacure acetate 651; Ciba Geigy) 0.11 g-P / V ratio 10/100

Here, PETA is pentaerythritol triacrylate, CAP is cellulose acetate propionate, and 10% CAP is ethyl acetate as a solvent, and the polymer content is 10%. DPHA is dipentaerythritol hexaacrylate, and the solvent MIBK for diluting it is methyl isobutyl ketone. P / V represents the mass ratio of filler / binder, and is styrene bead paste (trade name S
X-130H) is styrene beads and PETA 4: 6.
And the content of beads is 40% by mass. The internal haze value hi is 7, and the surface haze value hs is 1.
The average particle size of the beads was 3 μm, and the refractive index of the translucent resin was 1.57. Elliptic polarizing plates (Pol-A), (Pol-B), (P
ol-C) was applied to the TD80UF side and dried at 60 ° C. for 1 minute, and then 90 mJ of UV light (ultraviolet light) was applied to perform half cure to form a light scattering layer B having a film thickness of 3 to 4 μm / m ² . The surface roughness Ra of the surface irregularities was 1.0 μm. In this way, the elliptically polarizing plate with a light scattering layer (Pol-A
I), (Pol-BI), and (Pol-CI) were produced.

The light-scattering layer coating solution (II) was prepared under the following conditions. Light-scattering layer coating liquid (II) -PETA (product name PET30; Nippon Kayaku) 1.10 g-Styrene bead paste (product name SX-130; Soken Chemical) 2 g-10% CAP (diluted with ethyl acetate) 3.64 g- Solvent (toluene, butyl acetate, isobutyl alcohol) 7.21 g-Photocuring initiator (trade name Irgacure 651; Ciba Geigy) 0.11 g-P / V ratio 30/100

The internal haze value hi is 40, and the surface haze value h
s was 13, the average particle diameter of the beads was 3 μm, and the refractive index of the translucent resin was 1.57. The same procedure as (Pol-AI) except that the light-scattering layer coating solution (I) was replaced with the light-scattering layer coating solution (II) was performed (Pol-AII).
Was produced. The surface roughness Ra of the surface irregularities was 1.5 μm.

(Production of Liquid Crystal Display Device) Liquid crystal display device using TN type liquid crystal cell (Aquos, manufactured by Sharp Corporation)
Peel off the pair of polarizing plates provided in, and instead of the elliptic polarizing plates (Pol-AI), (Pol-BI), and (P
ol-AII) on the viewer side, and an elliptical polarizing plate (Pol-A)
Were adhered to the backlight side one by one via an adhesive so that the optically anisotropic layer was on the liquid crystal cell side, to prepare liquid crystal display devices AI, BI and AII of the present invention. The transmission axis of the elliptically polarizing plate on the observer side and the transmission axis of the elliptically polarizing plate on the backlight side were arranged so as to be in the O mode. On the other hand, the elliptically polarizing plates (Pol-CI) and (Pol-A) are attached to the viewer side, the elliptically polarizing plate (Pol-A) is attached to the backlight side, and the optical anisotropic layer is attached to the liquid crystal cell side. Liquid crystal display devices CI and A as attachment comparative examples were produced.

For the elliptically polarizing plate, (Pol-AI), (Pol-AI)
-BI), (Pol-AII), (Pol-CI), (P
ol-A), a durability test was performed at 60 ° C. and 90% RH for 1000 hours.

Elliptic polarizing plate (Pol-
AI), (Pol-BI), (Pol-AII), (Po
1-CI) and (Pol-A), the liquid crystal display devices AI, BI, AII, CI, and A were displayed in black (L1) using a measuring machine (EZ-Contrast160D, manufactured by ELDIM). From 8 to white display (L8), the viewing angle was measured. In addition, the front of the liquid crystal display device and 45
The luminance in the degree direction is measured by a color luminance meter (BM-7, TOPCON
Manufactured). The measurement results are shown in Table 1.

[0066]

[Table 1]

From the results shown in Table 1, the liquid crystal display devices AI, BI, AII, and A having moisture permeability of the present invention did not show a decrease in black luminance due to the durability test as compared with CI having poor moisture permeability,
Good contrast. Further, in AI, BI, and AII in which the light scattering layer is provided on the upper layer of the elliptically polarizing plate on the observer side, a region without gradation inversion spreads and the viewing angle is good as compared with A of Comparative Example. In particular, it is clear that the downward viewing angle is enlarged.

[0068]

In the liquid crystal display device in which the elliptically polarizing plate of the present invention is arranged, the viewing angle (especially the downward viewing angle) is expanded without increasing the thickness of the liquid crystal panel, and the contrast is lowered due to the change in the viewing angle. Tones or black and white reversals, hue changes, and the like hardly occur. Further, the elliptically polarizing plate of the present invention has excellent durability.

[Brief description of drawings]

FIG. 1 is a schematic sectional view schematically showing a layer structure of a preferable elliptically polarizing plate of the present invention.

[Explanation of symbols]

2 transparent support 3 Translucent diffuser 4 Translucent resin 5 Light scattering layer 6 Polarizing element 7 Transparent support 8 Optically anisotropic layer

Claims (2)

[Claims] 1. An optical compensation sheet having an optically anisotropic layer formed of a transparent support and a liquid crystalline compound, a polarizing element, and an elliptically polarizing plate having a light scattering layer, wherein the optical compensation sheet has a moisture permeability of 100 to 100. 1000g / m ² / 24hr
And the light scattering layer is a layer in which a light transmissive diffusing agent having a refractive index different from that of the resin is dispersed in a light transmissive resin. 2. A liquid crystal display device in which the optically anisotropic layer side of the elliptically polarizing plate according to claim 1 is disposed on the liquid crystal cell surface.