JP2006058542A - Birefringent film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a birefringent film which contributes to improving the viewing angle characteristics of a liquid crystal display device. <P>SOLUTION: The birefringent film is made of a cellulose acylate or a norbornene-based polymer, and when principal refractive indexes in a plane and the principal refractive index in the thickness direction are defined respectively as nx, ny and nz, they satisfy ny<nx<nz or ny<nz<nx, and satisfies Rth(700)-Rth(400)>-20, when the thickness of the film and Rth (Rth=[ä(nx+ny)/2}-nz]×d) at wavelengths 700nm, 400nm are defined respectively as Rth(700), and Rth(400). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to an in-plane switching (IPS) mode liquid crystal display device that performs display by applying a horizontal electric field to nematic liquid crystal aligned in a horizontal direction. The present invention also relates to a birefringent film useful as a phase plate of a liquid crystal display device, particularly an IPS mode liquid crystal display device.

  As a liquid crystal display device, a so-called TN mode, in which a liquid crystal layer in which nematic liquid crystal is twisted and arranged between two orthogonal polarizing plates, and an electric field is applied in a direction perpendicular to the substrate is widely used. In this system, since the liquid crystal rises with respect to the substrate during black display, birefringence occurs due to liquid crystal molecules when viewed from an oblique direction, and light leakage occurs. To solve this problem, a system for optically compensating the liquid crystal cell and preventing this light leakage by using a film in which liquid crystal molecules are hybrid-aligned has been put into practical use. However, even if liquid crystal molecules are used, it is very difficult to completely optically compensate the liquid crystal cell without any problem, resulting in a problem that gradation reversal in the lower direction of the screen cannot be suppressed.

  In order to solve such a problem, a liquid crystal display device using a so-called in-plane switching (IPS) mode in which a lateral electric field is applied to the liquid crystal, or a liquid crystal having a negative dielectric anisotropy is vertically aligned in the panel. A vertical alignment (VA) mode in which alignment is divided by protrusions and slit electrodes has been proposed and put into practical use. In recent years, these panels have been developed not only for monitor applications but also for TV applications, and screen brightness has been greatly improved accordingly. For this reason, a slight light leakage in the diagonally oblique incident direction during black display, which has not been considered as a problem in these operation modes, has become apparent as a cause of a decrease in display quality.

  As one means for improving the color tone and the viewing angle of black display, the arrangement of an optical compensation material having birefringence characteristics between the liquid crystal layer and the polarizing plate is also studied in the IPS mode. For example, by arranging a birefringent medium having an optical axis orthogonal to each other to compensate for the increase / decrease in retardation of the liquid crystal layer during tilting, a white display or a halftone display is diagonally arranged between the substrate and the polarizing plate. It is disclosed that coloring can be improved when viewing directly from (see Patent Document 1). In addition, a method using an optical compensation film made of a styrenic polymer having a negative intrinsic birefringence or a discotic liquid crystalline compound (see Patent Documents 2, 3, and 4), or an optical axis having a positive birefringence as an optical compensation film. A film in which the film is in the plane of the film and a film having a positive birefringence and an optical axis in the normal direction of the film (see Patent Document 5), biaxial optical compensation with a retardation of half wavelength A method using a sheet (see Patent Document 6), a method using a film having a negative retardation as a protective film of a polarizing plate, and providing an optical compensation layer having a positive retardation on this surface (see Patent Document 7) Proposed.

Japanese Patent Laid-Open No. 9-80424 Japanese Patent Laid-Open No. 10-54982 JP-A-11-202323 Japanese Patent Laid-Open No. 9-292522 JP 11-133408 A JP-A-11-305217 JP-A-10-307291

  However, many of the proposed methods are methods that improve the viewing angle by canceling the birefringence anisotropy of the liquid crystal in the liquid crystal cell, so the polarization axis crossing angle when the orthogonal polarizing plate is viewed from an oblique direction. There is a problem that the light leakage based on the deviation from orthogonality cannot be solved sufficiently. Even in a system that can compensate for this light leakage, it is very difficult to completely optically compensate the liquid crystal cell without any problem. Furthermore, in the optical compensation sheet for an IPS mode liquid crystal cell that performs optical compensation with a stretched birefringent polymer film, it is necessary to use a plurality of films. As a result, the thickness of the optical compensation sheet is increased, and the display device is made thinner. It is disadvantageous. In addition, since an adhesive layer is used for laminating stretched films, the adhesive layer contracts due to changes in temperature and humidity, and defects such as peeling and warping between films may occur.

  The present invention has been made in view of the above-mentioned problems, and has an object to provide a liquid crystal display device, particularly an IPS liquid crystal display device, which has a simple structure and improved display angle characteristics as well as display quality. To do. Another object of the present invention is to provide a birefringent film that contributes to the improvement of display quality and viewing angle characteristics of a liquid crystal display device, particularly an IPS liquid crystal display device.

Means for solving the above problems are as follows.
[1] A cellulose acylate or a norbornene polymer,
When the main refractive index in the plane is nx and ny, and the main refractive index in the thickness direction is nz, ny <nx <nz or ny <nz <nx,
When the thickness of the film is d, and Rth (Rth = [{(nx + ny) / 2} -nz] × d) at wavelengths of 700 nm and 400 nm are Rth (700) and Rth (400), respectively.
Rth (700) -Rth (400)>-20 nm
A birefringent film that meets the requirements.
[2] The birefringent film of [1] produced by stretching in the thickness direction or contracting in the in-plane direction.
[3] A long retardation film-attached polarizing plate having the long birefringent film of [1] or [2] and a long polarizing film.

[4] A liquid crystal display device comprising the birefringent film of [1] or [2] disposed on at least one side of a liquid crystal cell.
[5] At least a first polarizing film, a first retardation region made of the birefringent film of [1] or [2], a liquid crystal cell comprising a liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer, A liquid crystal display device having a second polarizing film, wherein the liquid crystal molecules of the liquid crystal layer are aligned parallel to the surfaces of the pair of substrates during black display.
[6] The Nz value of the first retardation region defined by Nz = (nx−nz) / (nx−ny) is less than 1,
In-plane main refractive indexes nx and ny are substantially equal, and further has a second retardation region having a thickness direction retardation Rth of 10 nm to 140 nm,
The slow axis of the first retardation region is substantially perpendicular or parallel to the transmission axis of the first polarizing film, and the transmission axis of the first polarizing film is the slow axis of the liquid crystal layer during black display. The liquid crystal display device according to [5], which is parallel to the phase axis direction.
[7] The retardation Re of the first retardation region defined by Re = (nx−ny) × d using in-plane main refractive indexes nx and ny and film thickness d is 200 nm to 350 nm. Nz value defined by Nz = (nx−nz) / (nx−ny) is less than 1,
The slow axis of the first retardation region is substantially perpendicular or parallel to the transmission axis of the first polarizing film, and the transmission axis of the first polarizing film is the slow axis of the liquid crystal layer during black display. The liquid crystal display device according to [5], which is parallel to the phase axis direction.
[8] The first retardation region has a retardation Re of 200 to 350 nm and an Nz value of less than 1, and a retardation Re of 200 to 350 nm and an Nz value of 1. The first phase difference region b is less than two regions, and the Nz value a of the first phase difference region a and the Nz value b of the first phase difference region b are | a−b | Substantially equal to 0.5, the slow axes of the first retardation region a and the first retardation region b are parallel, and the transmission axis of the first polarizing film is that of the liquid crystal layer during black display. The liquid crystal display device according to [5], which is parallel to the slow axis direction.
[9] The retardation Re of the first retardation region is 50 nm to 400 nm, the Nz value is −0.5 or more and 0.5 or less,
A rod-like liquid crystal compound that is substantially vertically aligned, further having a third layer difference region in which Rth is −250 to −40 nm and nx = ny <nz, and is a slow phase of the first retardation region [5] The liquid crystal display device according to [5], wherein the axis is perpendicular to a slow axis direction of the liquid crystal layer during black display.
[10] A pair of protective films disposed between the first polarizing film and / or the second polarizing film, and the protective film on the side close to the liquid crystal layer of the pair of protective films has an Rth of 20 nm. The liquid crystal display device according to any one of [5] to [7], which is -20 nm.
[11] A pair of protective films disposed between the first polarizing film and / or the second polarizing film, and the thickness of the protective film on the side close to the liquid crystal layer of the pair of protective films is 60 μm. The liquid crystal display device according to any one of [5] to [8] below.

  By using the birefringent film of the present invention, the absorption axes of the two polarizing plates deviate from 90 degrees when viewed from an oblique azimuth direction without changing the frontal characteristics of the liquid crystal display device. Accordingly, it is possible to improve the contrast reduction caused by the above, particularly the contrast reduction from an oblique direction of 45 degrees and the change in the viewing angle of the color during black display. Therefore, according to the present invention, it is possible to provide a liquid crystal display device, particularly an IPS liquid crystal display device, which has a simple structure and improved display angle characteristics as well as display quality.

BEST MODE FOR CARRYING OUT THE INVENTION

  In the following, embodiments of the birefringent film and the liquid crystal display device of the present invention and components thereof will be described in order. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the present specification, “parallel” and “orthogonal” mean that the angle is within a range of strictly less than ± 10 °. In this range, an error from a strict angle is preferably less than ± 5 °, and more preferably less than ± 2 °. Further, the “slow axis” means a direction in which the refractive index is maximized. Further, the measurement wavelengths of the refractive index and the phase difference are values at λ = 550 nm in the visible light region unless otherwise specified.

  In this specification, “birefringent film”, “polarizing film”, and “polarizing plate” are cut into a size to be incorporated into a long polarizing plate and a liquid crystal device unless otherwise specified (this specification In the above description, “cutting” includes both “punching” and “cutting out”). In this specification, “polarizing film” and “polarizing plate” are distinguished from each other. “Polarizing plate” means a laminate having a transparent protective film for protecting the polarizing film on at least one side of the “polarizing film”. It shall be.

In the present specification, the in-plane retardation Re and the thickness direction retardation Rth and Nz values of the retardation region and the birefringent film are defined by the following equations, respectively.
(1) Re = (nx−ny) × d
(2) Rth = Rth = [{(nx + ny) / 2} -nz] × d
(3) Nz = (nx−nz) / (nx−ny)
In the formula, nx and ny are in-plane main refractive indexes (where ny ≦ nx), nz is the main refractive index in the thickness direction, and d is the thickness of the layer or film.

[Birefringent film]
The birefringent film of the present invention satisfies ny <nx <nz or ny <nz <nx, where in-plane main refractive indices are nx and ny, and the main refractive index in the thickness direction is nz. Further, when Rth wavelengths of 700 nm and 400 nm are Rth (700) and Rth (400), respectively, Rth (700) −Rth (400)> − 20 nm is satisfied. Rth (700) -Rth (400) is more preferably -10 nm or more, and further preferably 0 nm or more. Further, Rth (700) -Rth (400) is preferably 200 nm or less, and more preferably 100 nm or less.

The birefringent film of the present invention comprises a cellulose acylate or a norbornene polymer.
The cellulose acylate that can be used as a raw material for the birefringent film of the present invention is not particularly limited, and the acyl group may be an aliphatic group or an allyl group. They are, for example, alkyl carbonyl esters, alkenyl carbonyl esters, aromatic carbonyl esters, aromatic alkyl carbonyl esters, etc. of cellulose, each of which may further have a substituted group, and an ester having a total carbon number of 22 or less. Groups are preferred. These preferred cellulose acylates include acyl groups having a total carbon number of 22 or less in the ester moiety (for example, acetyl, propionyl, butyroyl, barrel, heptanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, hexadecanoyl, octadecanoyl, etc. ), Arylcarbonyl groups (acrylic, methacrylic, etc.), allylcarbonylkis (benzoyl, naphthaloyl etc.) and cinnamoyl groups. Among these, cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate stearate, cellulose acetate benzoate, and the like are not particularly limited in the case of mixed esters, but preferably acetate is the total ester. It is preferable that it is 30 mol% or more.

  Among these, cellulose acylate is preferred, and photographic grades are particularly preferred, and commercially available photographic grades can be obtained with satisfactory quality such as viscosity average degree of polymerization and substitution degree. As manufacturers of photographic grade cellulose triacetate, Daicel Chemical Industries, Ltd. (for example, LT-20, 30, 40, 50, 70, 35, 55, 105, etc.), Eastman Kodak Company (for example, CAB-551) 0.01, CAB-551-0.02, CAB-500-5, CAB-381-0.5, CAB-381-02, CAB-381-20, CAB-321-0.2, CAP-504 0.2, CAP-482-20, CA-398-3, etc.), Coatles, Hoechst, etc., any of which can use photographic grade cellulose acylate. In addition, a plasticizer, a surfactant, a retardation modifier, a UV absorber, and the like can be mixed for the purpose of controlling the mechanical properties and optical properties of the film (reference material: Japanese Patent Application Laid-Open No. 2002-277632). Publication, Unexamined-Japanese-Patent No. 2002-182215).

The norbornene-based polymer that can be used as a raw material for the birefringent film of the present invention includes norbornene-based monomers such as norbornene and its derivatives, tetracyclododecene and its derivatives, dicyclopentadiene and its derivatives, methanotetrahydrofluorene and its derivatives. The polymer can be selected from monomers having as a main component.
Specific examples of the norbornene-based polymer include (1) a ring-opening polymer of a norbornene-based monomer, and (2) a ring-opening copolymer of the norbornene-based monomer and other monomers copolymerizable therewith. (3) addition polymer of norbornene monomer, (4) addition polymer of norbornene monomer and other monomer copolymerizable therewith, and (1) to (4) A hydride etc. are mentioned.

  Examples of the norbornene-based monomer include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.12,5] deca-3,7-diene ( Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.12,5] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0.12, 5.17,10] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, an alkoxycarbonyl group, and a carboxyl group. Moreover, these substituents may be the same or different and a plurality may be bonded to the ring. Norbornene monomers can be used alone or in combination of two or more.

  Examples of other monomers copolymerizable with norbornene monomers include, for example, monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene and derivatives thereof And so on.

A ring-opening polymer of a norbornene monomer and a ring-opening copolymer with another monomer copolymerizable with the norbornene monomer are used in the presence of a ring-opening polymerization catalyst. It can be obtained by polymerization.
As the ring-opening polymerization catalyst to be used, for example, a catalyst comprising a metal halide such as ruthenium or osmium and a sulfate or acetylacetone compound and a reducing agent; or a metal halide such as titanium, zirconium, tungsten or molybdenum Or a catalyst comprising an acetylacetone compound and an organoaluminum compound;

  Norbornene monomer addition polymers and addition copolymers with other monomers copolymerizable with norbornene monomers can be obtained by polymerizing the monomers in the presence of an addition polymerization catalyst. Can do. As the addition polymerization catalyst, for example, a catalyst composed of a metal compound such as titanium, zirconium, vanadium and an organoaluminum compound can be used.

  Examples of other monomers that can be addition copolymerized with a norbornene monomer include ethylene, propylene, 1-butene, 1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1 Α-olefins having 2 to 20 carbon atoms such as hexadecene, 1-octadecene, 1-eicocene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4,7-methano Cycloolefins such as -1H-indene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene, etc. Is mentioned. These monomers can be used alone or in combination of two or more. Among these, α-olefin is preferable and ethylene is more preferable.

As a method for forming these polymers into a sheet or film, either a hot melt molding method or a solution casting method can be used. The heat-melt molding method can be further classified into an extrusion molding method, a press molding method, an inflation molding method, an injection molding method, a blow molding method, a stretch molding method, etc. Among these methods, mechanical strength, surface In order to obtain a film excellent in accuracy and the like, the extrusion molding method, the inflation molding method, and the press molding method are preferable, and the extrusion molding method is most preferable.
The molding conditions are appropriately selected depending on the purpose of use and the molding method. In the case of the heat-melt molding method, the cylinder temperature is preferably set in the range of preferably 100 to 600 ° C, more preferably 150 to 350 ° C. The thickness of the formed sheet or film is preferably 10 to 300 μm, more preferably 30 to 200 μm.

  In the solution casting method, first, a solution (dope) of the polymer is prepared. If desired, an additive such as a retardation increasing agent may be added to the dope. The prepared dope is cast on a drum or band, and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  Moreover, when manufacturing a film, another additive can be added in the range which does not inhibit the objective of this invention. Examples of other additives include a retardation adjusting agent, a plasticizer, and a deterioration preventing agent. The retardation adjusting agent is used for increasing or decreasing the retardation of the film. The plasticizer is added to improve the mechanical properties of the film or to increase the drying speed. Examples of the plasticizer to be used include phosphoric acid esters and carboxylic acid esters. These other additives can be contained in the molding film by dissolving in the polymer when the polymer is melted in the hot melt molding method, or by dissolving in the dope in the solution casting method. .

Examples of the retardation adjusting agent that can be used include a retardation increasing agent composed of an aromatic compound having at least two aromatic rings. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.
The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, More preferred are a benzene ring and a 1,3,5-triazine ring. It is particularly preferred that the aromatic compound has at least one 1,3,5-triazine ring.

  The number of aromatic rings contained in the aromatic compound is preferably 2 to 20, more preferably 2 to 12, further preferably 2 to 8, and most preferably 2 to 6. . The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c). Such retardation increasing agents are described in WO01 / 88574A1, WO00 / 2619A1, JP-A Nos. 2000-1111914, 2000-275434, and Japanese Patent Application No. 2002-70009.

  Examples of plasticizers that can be used include plasticizers composed of phosphate esters. Examples thereof include triphenyl phosphate and tricresyl phosphate. Examples of the carboxylic acid ester include phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and diphenyl phthalate; citrate esters such as triethyl O-acetylcitrate and tributyl O-acetylcitrate; butyl oleate Higher fatty acid esters such as methylacetyl ricinoleate and dibutyl sebacate; trimetic acid esters; and the like.

  Examples of the deterioration inhibitor that can be used include an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, and amines. The deterioration preventing agents are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. There is something.

  These other additives are usually 0 to 20% by mass, preferably 0 to 10% by mass, and more preferably 0 to 5% by mass with respect to the polymer.

A molded film (for example, a film peeled off from a belt or a drum when prepared by a solution casting method, or a film which has been dried if desired to remove the solvent) has the above-mentioned birefringence. Therefore, it is preferable to carry out a stretching process. The stretching treatment may be uniaxial stretching or biaxial stretching. Regarding the stretching conditions such as the stretching ratio, a preferable range is determined according to the use of the birefringent film, more specifically, according to the optical characteristics required for the use. In particular, the birefringent film of the present invention is characterized in that the main refractive index nz in the thickness direction is larger than at least one of the in-plane main refractive indexes nx and ny. In order to impart such birefringence, it is preferable to stretch in the thickness direction or shrink in the in-plane direction. As a method of shrinking in the in-plane direction, a method using a heat shrinkable film can be used. For example, a heat-shrinkable film is adhered to both or one side of the film, held in a stretch processing machine in that state, heated while being stretched in a uniaxial or biaxial direction, and at least in-plane by the shrinkage force of the heat-shrinkable film It is preferable to contract in one direction. The heat-shrinkable film is a film that exhibits shrinkage under heating, and the material thereof is not particularly limited. In general, a uniaxial or biaxially stretched film made of a thermoplastic resin such as polyester is used. The method for adhering the molded film and the heat-shrinkable film, stretching conditions, and the like can be performed with reference to the method described in JP-A-7-230007. Further, when a heat-shrinkable film is used, not only the film is shrunk in the in-plane direction but also substantially stretched in the thickness direction.
In order to produce a birefringent film having desired optical properties, normal uniaxial or biaxial stretching without using a heat-shrinkable film is performed before or after the stretching process with the heat-shrinkable film adhered. The stretching process using a heat-shrinkable film may be performed in multiple stages.

The birefringent film of the present invention may be produced in a long shape. The long birefringent film can be wound up in a roll and collected / stored. A long polarizing plate can be produced by laminating a long birefringent film with a long polarizing film. Rather than cutting each of them into a predetermined size and aligning and sticking them together, the occurrence of misalignment can be reduced, which contributes to the improvement of productivity. For example, by using a long polarizing film whose transmission axis is orthogonal or parallel to the longitudinal direction and a long birefringent film having a slow axis in the direction orthogonal or parallel to the longitudinal direction, By bonding with an adhesive or a pressure-sensitive adhesive, a long laminate can be obtained, and then the laminate can be cut into a predetermined size and incorporated into a liquid crystal display device as a laminated polarizing plate. By performing the laminating process in a long state, it is easy to laminate the polarizing film with the transmission axis of the polarizing film and the slow axis of the birefringent film being orthogonal or parallel. As a result, extremely accurate bonding is possible, and productivity is improved.
The protective film may be laminated on the polarizing film and then laminated with the birefringent film, or the birefringent film may be laminated directly on the surface of the polarizing film. In such an embodiment, the birefringent film also functions as a protective film for the polarizing film.

The birefringent film of the present invention can be used for various applications. It is preferably used as an optical member for improving the viewing angle characteristics of a liquid crystal display device. For example, viewing angle characteristics can be improved by disposing the birefringent film of the present invention on the display surface side and / or on the back surface side with the liquid crystal cell as the center. The birefringent film of the present invention is more preferably used for an IPS liquid crystal display device. For example, in an IPS liquid crystal display device having a liquid crystal cell in which liquid crystal molecules of a liquid crystal layer are aligned parallel to the surfaces of the pair of substrates during black display, the liquid crystal cell and the polarizing film and / or the liquid crystal cell on the display surface side Viewing angle characteristics can be improved by disposing the birefringent film of the present invention between the polarizing film and the polarizing film on the back side. Furthermore, since the birefringent film of the present invention has the above optical characteristics, particularly when observed from an oblique direction, light leakage at the time of black display caused by deviation of the transmission axes of the pair of polarizing films from the crossed Nicols state and Color shift can be remarkably reduced. In addition, since the birefringent film of the present invention has improved wavelength dispersion, when used as an optical compensation sheet for a liquid crystal display device, the image may be colored due to the birefringent film. Few. Furthermore, since it can also be manufactured integrally with other members of the liquid crystal display device by roll-to-roll, this case also contributes to improvement of productivity.
Hereinafter, various aspects of the liquid crystal display device provided with the birefringent film of the present invention will be described.

[Liquid Crystal Display]
One embodiment of the liquid crystal display device of the present invention is shown in FIG. The liquid crystal display device shown in FIG. 2 includes polarizing films 8 and 20, a first retardation region 10, a second retardation region 12, substrates 13 and 17, and a liquid crystal layer 15. The polarizing films 8 and 20 are sandwiched between protective films 7a and 7b and 19a and 19b, respectively.

  In the liquid crystal display device of FIG. 2, the liquid crystal cell includes substrates 13 and 17 and a liquid crystal layer 15 sandwiched between them. The product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is optimal in the range of 0.2 to 0.4 μm for the IPS type having no twisted structure in the transmission mode. In this range, the white display luminance is high and the black display luminance is small, so that a bright and high-contrast display device can be obtained. An alignment film (not shown) is formed on the surfaces of the substrates 13 and 17 that are in contact with the liquid crystal layer 15 to align liquid crystal molecules substantially parallel to the surface of the substrate and to be rubbed on the alignment film. The liquid crystal molecule alignment direction in the voltage non-application state or the low application state is controlled by the processing directions 14 and 18 and the like. Further, an electrode (not shown in FIG. 2) capable of applying a voltage to the liquid crystal molecules is formed on the inner surface of the substrate 13 or 17.

  FIG. 1 schematically shows the alignment of liquid crystal molecules in one pixel region of the liquid crystal layer 15. FIG. 1 shows the alignment of liquid crystal molecules in a very small area corresponding to one pixel of the liquid crystal layer 15 in the rubbing direction 4 of the alignment film formed on the inner surfaces of the substrates 13 and 17 and the substrates 13 and 17. It is the schematic diagram shown with the electrodes 2 and 3 which can apply a voltage to the liquid crystal molecule formed in the inner surface. When active driving is performed using a nematic liquid crystal having positive dielectric anisotropy as a field effect liquid crystal, the liquid crystal molecule alignment directions in a no voltage application state or a low application state are 5a and 5b. A display is obtained. When applied between the electrodes 2 and 3, the liquid crystal molecules change their alignment direction in the directions of 6 a and 6 b in accordance with the voltage. Usually, bright display is performed in this state.

  In FIG. 2 again, the transmission axis 9 of the polarizing film 8 and the transmission axis 21 of the polarizing film 20 are arranged orthogonally. In the liquid crystal display device shown in FIG. 2, the configuration in which the polarizing film 8 is sandwiched between the two protective films 7a and 7b is shown, but the protective film 7b may be omitted. When the protective film 7b is disposed, the thickness direction retardation Rth of the protective film is preferably 25 nm or less, and more preferably -20 to 20 nm or less. Moreover, it is preferable that the thickness of the protective film 7b is 60 micrometers or less. Further, although the polarizing film 20 is also sandwiched between the two protective films 19a and 19b, the protective film 19a on the side close to the liquid crystal layer 15 may be omitted. When the protective film 19a is disposed, the thickness direction retardation Rth of the protective film is preferably 25 nm or less, and more preferably -20 to 20 nm or less. The thickness of the protective film 19a is preferably 60 μm or less. In the case where the protective film 7b or 19a is not provided, the first retardation region 10 also functions as a protective film for the polarizing film 8 or the polarizing film 20, but in this case, the first retardation region, that is, the birefringence of the present invention. A polarizing film with a retardation layer can be formed by laminating a functional film and a polarizing film, and then incorporated into a liquid crystal display device.

  The first retardation region 10 and the second retardation region 12 may be disposed between the liquid crystal cell and the viewing-side polarizing film with reference to the position of the liquid crystal cell, or may be disposed between the liquid crystal cell and the back side. You may arrange | position between polarizing films. The first phase region 10 is made of the birefringent film of the present invention, exhibits the above optical characteristics, and has an Nz value of less than 1. In the second retardation region 12, the in-plane main refractive indexes nx and ny are substantially equal, and the thickness direction retardation Rth is 10 nm to 140 nm.

  The slow axis 11 of the first retardation region 10 is substantially perpendicular to the transmission axis 9 of the first polarizing film 8, and the transmission axis 9 of the first polarizing film 8 is the liquid crystal layer 5 at the time of black display. It is parallel to the slow axis 16 direction. Although the slow axis 11 of the first retardation region 10 may be substantially parallel to the transmission axis 9 of the first polarizing film 8, the transmission axis 9 of the first polarizing film 8 is also in this aspect. The liquid crystal layer 5 is arranged in parallel with the slow axis 16 direction during black display.

  Details of this embodiment are described in the specification of Japanese Patent Application No. 2004-037835, and the contents thereof can be applied to this embodiment.

Another embodiment of the liquid crystal display device of the present invention is shown in FIG. In FIG. 3, the same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. The liquid crystal display device of FIG. 3 has a first retardation region 10 ′ that contributes to optical compensation of the liquid crystal cell between the liquid crystal cell and the polarizing film 8. The first retardation region 10 ′ is composed of a first retardation region 10′a and a first retardation region 10′b, and both regions are each composed of the birefringent film of the present invention. The first retardation region 10′a has a retardation Re of 200 to 350 nm and an Nz value of less than 1. The first retardation region 10′b has a retardation Re of 200 to 350 nm, and Nz value is less than 1. The value of | a−b | of the Nz value a of the first phase difference region 10′a and the Nz value b of the first phase difference region 10′b is substantially equal to 0.5, preferably 0. 0.5 ± 0.5, more preferably 0.5 ± 0.3, and still more preferably 0.5 ± 0.1. The first phase difference region 10′a and the first phase difference region 10′b are arranged with their slow axes 11′a and 11′b parallel to each other. As in the embodiment shown in FIG. 2, in this embodiment, the transmission axis 9 of the first polarizing film 8 is parallel to the slow axis 16 direction of the liquid crystal layer 5 during black display.
Details of this embodiment are described in Japanese Patent Application Laid-Open No. 11-305217 and Japanese Patent Application Laid-Open No. 2001-0350022, and the contents thereof can be applied to this embodiment.

Another embodiment of the present invention is shown in FIG. In FIG. 3, the same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. The liquid crystal display device of FIG. 4 has a first retardation region 10 ″ contributing to optical compensation of the liquid crystal cell between the liquid crystal cell and the polarizing film 8, and a third retardation region 22 between the liquid crystal cell and the polarizing film 20. The first retardation region 10 ″ is made of the birefringent film of the present invention, has a retardation Re of 50 nm to 400 nm, and an Nz value of −0.5 or more and 0.5 or less. Further, the third retardation region 22 contains a substantially vertically aligned rod-like liquid crystal compound, Rth is −250 to −40 nm, and nx = ny <nz. The slow axis 11 of the first retardation region 10 ″ is a direction orthogonal to the slow axis 16 direction of the liquid crystal layer 15 during black display.
Details of this embodiment are described in the specification of Japanese Patent Application No. 2004-037836, and the contents thereof can be applied to this embodiment.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Preparation of IPS mode liquid crystal cell 1>
As shown in FIG. 1, electrodes (2 and 3 in FIG. 1) are arranged on one glass substrate so that the distance between adjacent electrodes is 20 μm, and a polyimide film is used as an alignment film on it. A rubbing process was performed. The rubbing process was performed in the direction 4 shown in FIG. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. The two glass substrates are stacked and bonded so that the alignment films face each other, the distance between the substrates (gap; d) is 3.9 μm, and the rubbing directions of the two glass substrates are parallel. A nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric anisotropy (Δε) of 4.5 was enclosed. The value of d · Δn of the liquid crystal layer was 300 nm.

[Examples 1 to 5]
(Production of retardation plate)
At room temperature, 120 parts by weight of cellulose acetate having an average degree of acetylation of 59.0%, 9.36 parts by weight of triphenyl phosphate, 4.68 parts by weight of biphenyl diphenyl phosphate, 1.00 parts by weight of the following retardation increasing agent, tribenge A solution (dope) was prepared by mixing 2.00 parts by weight of ruamine, 543.14 parts by weight of methylene chloride, 99.35 parts by weight of methanol and 19.87 parts by weight of n-butanol.

The obtained dope was cast on a film-forming band, dried at room temperature for 1 minute, and then dried at 45 ° C. for 5 minutes. The residual amount of solvent after drying was 30% by weight. The cellulose acetate film was peeled from the band, dried at 120 ° C. for 10 minutes, and then stretched at 130 ° C. in a direction parallel to the casting direction. The direction perpendicular to the stretching direction was allowed to shrink freely. After stretching, the stretched film was taken out after drying at 120 ° C. for 30 minutes. The residual solvent amount after stretching was 0.1% by weight. The thickness of the obtained polymer film (PF-1) was 101 μm, and the retardation value (Re) at wavelengths of 450 nm, 550 nm, and 590 nm was measured using an ellipsometer (M-150, manufactured by JASCO Corporation). ) Were measured to be 119.3 nm, 137.2 nm and 142.7 nm, respectively.
Retardation films 2 and 3 were obtained by changing the stretching ratio to Re = 150 nm and 140 nm, respectively.
Further, the stretching ratio was changed, and two obtained polymer films were bonded so that their slow axes were parallel, and those having Re of 275 nm and 172 nm were designated as retardation films A and C, respectively.

<Production of First Phase Difference Region 2, First Phase Difference Region 3, First Phase Difference Region A, B, and C>
A heat-shrinkable uniaxially stretched polyester film is bonded to both surfaces of the retardation films 2, 3, A, and C prepared above via an acrylic adhesive layer so that the slow axes thereof are orthogonal to each other. The film is shrunk using a stretching apparatus while being shrunk by heating to 0 ° C., and then the heat-shrinkable film is peeled off to obtain the first phase difference region 2, the first phase difference region 3, and the first phase difference, respectively. Phase difference regions A, B and C were obtained. The shrinkage rate can be changed by changing the material of the heat shrinkable film to be used or by changing the stretch rate at the time of producing the heat shrinkable film, whereby the respective optical characteristics such as Rth can be changed to a predetermined value. Adjusted to value.

  About the produced 1st phase difference area | region 2, 1st phase difference area | region 3, 1st phase difference area | region A, B, and C, using an automatic birefringence meter (KOBRA-21ADH, Oji Scientific Instruments Co., Ltd. product). , Re dependency of the light incident angle was measured, and these optical characteristics were calculated. Each optical characteristic is as follows.

(Formation of third retardation region (vertically aligned rod-like liquid crystal compound layer))
Using a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re = 2 nm, Rth = 48 nm), the surface was saponified, and a commercially available vertical alignment film (JALS- 204R, manufactured by Nippon Synthetic Rubber Co., Ltd. was diluted 1: 1 with methyl ethyl ketone, and then 2.4 ml / m ^{2 was} applied with a wire bar coater. Immediately, it was dried with 120 ° C. warm air for 120 seconds. On this alignment film, 3.8 g of the following rod-shaped liquid crystal compound, 0.06 g of photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy), 0.02 g of sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) A solution prepared by dissolving 0.002 g of the following air interface side vertical alignment agent in 9.2 g of methyl ethyl ketone was applied with a # 3.5 wire bar. This was affixed to a metal frame and heated in a constant temperature bath at 100 ° C. for 2 minutes to align the rod-like liquid crystal compound. Next, UV irradiation was performed at 100 ° C. with a 120 W / cm high-pressure mercury lamp for 30 seconds to crosslink the rod-like liquid crystal compound, and then allowed to cool to room temperature to prepare a retardation layer. A film composed of a support composed of the cellulose acetate film and a retardation layer is referred to as a protective film 1.

  Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments), measure the light incident angle dependency of Re of the protective film 1 and subtract the contribution of the cellulose acetate film measured in advance. Thus, the optical characteristics of only the rod-like liquid crystal retardation layer were calculated. As a result, Re was 0 nm, Rth was -145 nm, and it was confirmed that the rod-like liquid crystal was aligned substantially vertically. The rod-like liquid crystal retardation layer had positive refractive index anisotropy and the optical axis was substantially perpendicular to the layer surface. This rod-like liquid crystal retardation layer was defined as a first layer difference region 1.

(Production of second retardation region 1)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution having the following composition.
Composition of cellulose acetate solution Cellulose acetate with an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 Mass part Methanol (second solvent) 54 parts by mass 1-butanol (third solvent) 11 parts by mass In another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride, and 20 parts by mass of methanol were added. Then, the mixture was stirred while heating to prepare a retardation increasing agent solution. A dope was prepared by mixing 6 parts by mass of the retardation increasing agent solution with 487 parts by mass of the cellulose acetate solution and stirring sufficiently.

The obtained dope was cast using a band casting machine. After the film surface temperature on the band reached 40 ° C., the film was dried with warm air of 60 ° C. for 1 minute, and the film was peeled off from the band. Next, the film was dried with a drying air at 140 ° C. for 10 minutes to produce a film having a thickness of 80 μm.
The optical properties of this film were determined by measuring the dependence of Re on the light incident angle using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments). And Re = 5 nm and Rth = 80 nm. This film was designated as a second phase difference region 1.

<Preparation of polarizing plate protective film 1 and polarizing plate protective film 2>
(Polarizing plate protective film 1)
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acetate solution A was prepared.
<Composition of cellulose acetate solution A>
Cellulose acetate with a substitution degree of 2.86 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (second solvent) 54 parts by weight 1-butanol 11 parts by weight

The following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-1 was prepared.
<Additive solution B-1 composition>
Methylene chloride 80 parts by mass Methanol 20 parts by mass The following optical anisotropy reducing agent 40 parts by mass

40 parts by mass of the additive solution B-1 was added to 477 parts by mass of the cellulose acetate solution A, and the dope was prepared by sufficiently stirring. The dope was cast from a casting port onto a drum cooled to 0 ° C. The solvent content is peeled off at 70% by mass, both ends in the width direction of the film are fixed with a pin tenter (the pin tenter described in FIG. 3 of JP-A-4-1009), and the solvent content is 3-5% by mass. In this state, the film was dried while maintaining an interval at which the stretching ratio in the transverse direction (direction perpendicular to the machine direction) was 3%. Then, it further dried by conveying between the rolls of the heat processing apparatus, and produced the polarizing plate protective film 1 with a thickness of 80 μm.
Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependence of Re was measured, and the optical characteristics were calculated. Re was 1 nm and Rth was 6 nm. I was able to confirm.

(Polarizing plate protective film 2)
Using a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re = 2 nm, Rth = 48 nm), the surface was saponified, and a commercially available vertical alignment film (JALS- 204R, manufactured by Nippon Synthetic Rubber Co., Ltd. was diluted 1: 1 with methyl ethyl ketone, and then 2.4 ml / m ^{2 was} applied with a wire bar coater. Immediately, it was dried with warm air of 120 ° C. for 120 seconds.

  On the alignment film, 1.8 g of the following rod-like liquid crystal compound, 0.06 g of photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy), 0.02 g of sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.), A solution obtained by dissolving 0.002 g of the following air interface side vertical alignment agent in 9.2 g of methyl ethyl ketone was applied with a wire bar of # 2.3. This was affixed to a metal frame and heated in a constant temperature bath at 100 ° C. for 2 minutes to align the rod-like liquid crystal compound. Next, using a 120 W / cm high-pressure mercury lamp at 100 ° C., UV irradiation was performed for 30 seconds to crosslink the rod-like liquid crystal compound. Then, it stood to cool to room temperature. Thus, the polarizing plate protective film 2 was produced.

  Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments Co., Ltd.), the light incident angle dependency of Re of the polarizing plate protective film 2 was measured. As a result, Re was 2 nm and Rth was −15 nm. there were.

<Preparation of polarizing plate A>
Next, iodine is adsorbed to the stretched polyvinyl alcohol film to produce a polarizing film, and saponification is performed on a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd., Re = 2 nm, Rth = 48 nm). Using a polyvinyl alcohol-based adhesive, it was attached to one side of the polarizing film. Further, the polarizing plate protective film 2 was attached to the other side of the polarizing film using a polyvinyl alcohol-based adhesive so that the polarizing film on the cellulose acetate film side was covered with the polarizing plate A, thereby preparing the polarizing plate A.

<Preparation of polarizing plate B>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was saponified and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . Further, similarly, the polarizing plate protective film 1 produced as described above was attached to the other surface of the polarizing film to form a polarizing plate B.

<Preparation of polarizing plate C>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was saponified and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . Further, in the same manner, a commercially available cellulose acetate film (Fujitac T40UZ, manufactured by Fuji Photo Film Co., Ltd., Re = 1 nm, Rth = 35 nm) was saponified, and a polyvinyl alcohol adhesive was used on the other side of the polarizing film. A pasting polarizing plate C was formed.

<Preparation of polarizing plate D>
A polarizing film is produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is subjected to saponification treatment and attached to both surfaces of the polarizing film using a polyvinyl alcohol adhesive. Plate D was formed.

<Preparation of polarizing plates E2 and EA with retardation film>
A polarizing film was produced in the same manner, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was saponified and attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. . In the same manner, the first retardation region 2 is saponified, and the transmission axis of the polarizing film and the slow axis of the first retardation region 1 are orthogonal to the other surface of the polarizing film using a polyvinyl alcohol adhesive. A polarizing plate E2 with a retardation film was prepared so as to be.
Similarly, the polarizing film EA having a retardation film was prepared by pasting the polarizing film so that the transmission axis of the polarizing film and the slow axis of the first retardation region A were parallel to each other.

[Example 6]
The second retardation region 1 was bonded to the first retardation region side of the retardation film-attached polarizing plate E2 using an acrylic adhesive.
This is applied to one of the IPS mode liquid crystal cells 1 prepared above so that the transmission axis of the polarizing plate is parallel to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation region 2 is black). The liquid crystal cell was pasted so that the surface side of the second retardation region 1 was on the liquid crystal cell side.
Subsequently, the polarizing plate B was attached to the other side of the IPS mode liquid crystal cell 1 so as to be in a crossed Nicols arrangement with respect to the polarizing film of the polarizing plate E2 with a retardation film, thereby producing a liquid crystal display device. The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.07%.

[Example 7]
An acrylic adhesive was used for the polarizing plate D, and the produced first retardation region 3 was attached so that the transmission axis of the polarizing film and the slow axis of the first retardation region 3 were parallel. In this configuration, Fujitac TD80UF, which is a protective film of the polarizing plate D, Re = 2 nm, and Rth = 48 nm correspond to the second retardation region.

This is applied to one of the IPS mode liquid crystal cells 1 produced above so that the transmission axis of the polarizing plate is parallel to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation region 3 is black). The liquid crystal cell was pasted so that the surface side of the first retardation region 3 was on the liquid crystal cell side.
Subsequently, the polarizing plate C is pasted on the other side of the IPS mode liquid crystal cell 1 so that the Fujitac T40UZ side is on the liquid crystal cell side and the polarizing plate D is in a crossed Nicol arrangement. Was made. The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.08%.

[Example 8]
An acrylic adhesive was used on the first retardation region side of the polarizing plate EA with a retardation film, and the first retardation region B was bonded so that the first retardation region A and the slow axis were parallel.
This is applied to one of the IPS mode liquid crystal cells 1 produced above so that the transmission axis of the polarizing plate is parallel to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation region A is black). The liquid crystal cell was pasted so that the first retardation region B surface side was on the liquid crystal cell side.
Subsequently, a polarizing plate B was attached to the other side of the IPS mode liquid crystal cell 1 so as to be in a crossed Nicols arrangement with respect to the polarizing film of the polarizing plate EA with a retardation film, thereby producing a liquid crystal display device. The leakage light of the liquid crystal display device thus manufactured was measured. Light leakage when observed from the left oblique direction of 60 ° was 0.01%.

[Example 9]
Using the acrylic adhesive for the polarizing plate D, the produced first retardation region C was attached so that the transmission axis of the polarizing film and the slow axis of the first retardation region C were perpendicular.

This is applied to one of the IPS mode liquid crystal cells 1 produced above so that the transmission axis of the polarizing plate is parallel to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation region C is black). The liquid crystal cell was pasted so that the slow axis of the liquid crystal molecules of the liquid crystal cell was perpendicular to the liquid crystal cell and the first retardation region C surface side was the liquid crystal cell side.
Subsequently, a third retardation region is attached to the other side of the IPS mode liquid crystal cell 1, and the polarizing plate B is crossed with the polarizing plate D so that the polarizing plate protective film 1 is on the liquid crystal cell side. A liquid crystal display device was manufactured by pasting in a Nicol arrangement. The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.02%.

[Comparative Example 1]
A commercially available polarizing plate (HLC2-5618, manufactured by Sanritz Co., Ltd.) was attached to both sides of the produced IPS mode liquid crystal cell 1 in a crossed Nicol arrangement to produce a liquid crystal display device. An optical compensation film was not used. In the liquid crystal display device, as in Example 1, the polarizing plate was attached so that the transmission axis of the upper polarizing plate was parallel to the rubbing direction of the liquid crystal cell. The leakage light of the liquid crystal display device thus manufactured was measured. Light leakage when observed from the left oblique direction of 60 ° was 0.55%.

[Comparative Example 2]
Using the acrylic adhesive for the polarizing plate D, the produced first retardation region 1 was attached so that the transmission axis of the polarizing film and the slow axis of the first retardation region 1 were parallel.
This is applied to one of the IPS mode liquid crystal cells 1 produced above so that the transmission axis of the polarizing plate is perpendicular to the rubbing direction of the liquid crystal cell (that is, the slow axis of the first retardation region 1 is black). The liquid crystal cell was pasted so that the slow axis of the liquid crystal molecules of the liquid crystal cell at the time was perpendicular to the liquid crystal cell side.
Subsequently, the polarizing plate B is attached to the other side of the IPS mode liquid crystal cell 1 so that the polarizing plate protective film 1 side is on the liquid crystal cell side and the polarizing plate D is arranged in a crossed Nicol arrangement, A liquid crystal display device was produced. The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 1.28%, which was a large leakage light.

It is the schematic which shows the pixel area example of the liquid crystal display device of this invention. It is the schematic which shows an example of the liquid crystal display device of this invention. It is the schematic which shows the other example of the liquid crystal display device of this invention. It is the schematic which shows the other example of the liquid crystal display device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal element pixel area 2 Pixel electrode 3 Display electrode 4 Rubbing direction 5a, 5b Director of liquid crystal compound at the time of black display 6a, 6b Director of liquid crystal compound at the time of white display 7a, 7b, 19a, 19b Protective film for polarizing film 8, 20 Polarizing film 9, 21 Polarizing transmission axis of polarizing film 10, 10 ', 10 "First retardation region 11 Slow axis 12 of first retardation region Second retardation region 13, 17 Cell substrates 14, 18 Cell substrate rubbing direction 15 Liquid crystal layer 16 Slow axis direction of liquid crystal layer 22 Third retardation region

Claims (11)

Made of cellulose acylate or norbornene polymer,
When the main refractive index in the plane is nx and ny, and the main refractive index in the thickness direction is nz, ny <nx <nz or ny <nz <nx,
When the thickness of the film is d, and Rth (Rth = [{(nx + ny) / 2} -nz] × d) at wavelengths of 700 nm and 400 nm are Rth (700) and Rth (400), respectively.
Rth (700) -Rth (400)>-20 nm
A birefringent film that meets the requirements. The birefringent film according to claim 1, wherein the birefringent film is produced by stretching in a thickness direction or shrinking in an in-plane direction. 3. A polarizing plate with a long retardation film comprising the long birefringent film according to claim 1 and a long polarizing film. A liquid crystal display device comprising the birefringent film according to claim 1 or 2 disposed on at least one side of a liquid crystal cell. 3. A liquid crystal cell comprising at least a first polarizing film, a first retardation region comprising the birefringent film according to claim 1 or 2, a liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer, and a second polarization A liquid crystal display device having a film, wherein the liquid crystal molecules of the liquid crystal layer are aligned parallel to the surfaces of the pair of substrates during black display. The Nz value of the first retardation region defined by Nz = (nx−nz) / (nx−ny) is less than 1,
In-plane main refractive indexes nx and ny are substantially equal, and further has a second retardation region having a thickness direction retardation Rth of 10 nm to 140 nm,
The slow axis of the first retardation region is substantially perpendicular or parallel to the transmission axis of the first polarizing film, and the transmission axis of the first polarizing film is the slow axis of the liquid crystal layer during black display. The liquid crystal display device according to claim 5, which is parallel to the phase axis direction. The retardation Re of the first retardation region defined by Re = (nx−ny) × d using the in-plane main refractive indices nx and ny and the film thickness d is 200 nm to 350 nm, and Nz = The Nz value defined by (nx−nz) / (nx−ny) is less than 1,
The slow axis of the first retardation region is substantially perpendicular or parallel to the transmission axis of the first polarizing film, and the transmission axis of the first polarizing film is the slow axis of the liquid crystal layer during black display. The liquid crystal display device according to claim 5, which is parallel to the phase axis direction. The first retardation region has a retardation Re of 200 to 350 nm and an Nz value of less than 1, and a retardation Re of 200 to 350 nm and an Nz value of less than 1. The first phase difference region b is composed of two regions, and the Nz value a of the first phase difference region a and the value of | a−b | of the Nz value b of the first phase difference region b are substantially equal to each other. Equal to 0.5, the slow axes of the first retardation region a and the first retardation region b are parallel, and the transmission axis of the first polarizing film is the slow axis of the liquid crystal layer during black display. The liquid crystal display device according to claim 5, which is parallel to the direction. The retardation Re of the first retardation region is 50 nm to 400 nm, the Nz value is −0.5 or more and 0.5 or less,
A rod-like liquid crystal compound that is substantially vertically aligned, further having a third layer difference region in which Rth is −250 to −40 nm and nx = ny <nz, and is a slow phase of the first retardation region 6. The liquid crystal display device according to claim 5, wherein the axis is perpendicular to the slow axis direction of the liquid crystal layer during black display. It has a pair of protective films arranged with the first polarizing film and / or the second polarizing film in between, and Rth of the protective film on the side close to the liquid crystal layer of the pair of protective films is 20 nm to -20 nm. The liquid crystal display device according to any one of claims 5 to 8. A pair of protective films disposed between the first polarizing film and / or the second polarizing film, and the thickness of the protective film on the side close to the liquid crystal layer of the pair of protective films is 60 μm or less; The liquid crystal display device according to claim 5.

Images