JP2003279743A - Polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display with high display quality without causing problems such as light leakage or the like. <P>SOLUTION: This is a polarizing plate consisting of an optical compensation film which has an optical anisotropic layer which is comprised of (a) a polymer film, (b) a polarizing membrane, and (c) a liquid crystal compound on a polymer base material. The elastic modulus of the polymer film is 4 GPa or more. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate and a liquid crystal display device using the polarizing plate.

[0002]

2. Description of the Related Art A liquid crystal display device comprises a polarizing plate and a liquid crystal cell. In the TN mode TFT liquid crystal display device, which is currently the mainstream, an optical compensation film 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. is doing. 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 retardation plate on one surface of a polarizing film and an elliptically polarizing plate having a protective film on the other surface to increase the front contrast without increasing the thickness of the liquid crystal display device. There is a statement that it is possible. However, it has been found that the retardation film (optical compensation sheet) of the present invention is apt to cause a retardation due to distortion of heat or the like, and has a problem in durability. This phase difference causes frame-shaped light leakage (increased transmittance) in the liquid crystal display device, resulting in deterioration of display quality of the liquid crystal display device. To solve the problem of phase difference due to distortion, Japanese Patent Laid-Open No. 7-191217 and European Patent 09116
In the specification of No. 56A2, an optical compensation film in which an optically anisotropic layer made of a discotic (discotic) compound is coated on a transparent support is directly used as a protective film of a polarizing plate to thicken a liquid crystal display device. Without having to solve the above-mentioned problem regarding durability.

[0003]

However, when a polarizing plate using the above-mentioned optical compensation film as a protective film is attached to a large panel of 17 inches or more, light leakage due to thermal distortion cannot be completely eliminated. found. The optical compensatory sheet is required to have not only a function of optically compensating the liquid crystal cell, but also excellent durability due to a change in use environment. An object of the present invention is to optically compensate a liquid crystal cell using an optical compensation sheet. Another object of the present invention is to provide a liquid crystal display device with high display quality without causing problems such as light leakage by disposing an optical compensation sheet on one side of a polarizing film and using it in a liquid crystal display device. That is. Still another object of the present invention is to add an optical compensation function to a polarizing plate without increasing the number of components of the polarizing plate.

[0004]

In order to optically compensate a liquid crystal cell, an optically anisotropic layer formed of a liquid crystalline compound is used. Generally, the optically anisotropic layer is used as an optical compensatory sheet coated on a polymer film (when used for a polarizing plate, on a cellulose acetate film which is a protective film). When the optical compensation sheet is used in a liquid crystal display device, the optical compensation sheet is generally fixed to a liquid crystal cell or the like with an adhesive or the like before use. Therefore, when the polymer film used for such an optical compensation sheet expands or contracts, the generated distortion is suppressed as a whole of the optical compensation sheet, and the optical characteristics of the polymer film change.

Conventionally, the main causes of the change in optical characteristics were as follows. One is that the polymer film expands or contracts due to changes in the wet heat conditions in the usage environment of the liquid crystal display device, causing changes in the optical characteristics of the optical compensation sheet. On the other hand, when a backlight of a liquid crystal display device is turned on, a temperature distribution is generated in the surface of the optical compensation sheet, and its thermal distortion causes a change in optical characteristics.
In particular, it has been known that environmental conditions have a great influence on polymers having a hydroxyl group such as cellulose ester.

That is, in order to eliminate light leakage, the conventional idea is to suppress variations in the optical characteristics of the optical compensation sheet due to environmental conditions and make the temperature distribution generated in the optical compensation sheet uniform. The inventors of the present invention have earnestly studied and found an even more important cause. Generally, a polarizing plate
It consists of a pair of protective films and a polarizer whose main component is PVA. It was found that it is PVA used in the polarizer that causes the most dimensional change due to changes in wet heat conditions in the usage environment of the liquid crystal display device. In the usage mode, the polarizing plate is attached to the liquid crystal cell via an adhesive, so that the dimensional change due to the environment is transmitted to the protective film (that is, the optical compensation sheet) as strain stress. Due to this stress, the protective film (optical compensation sheet) causes fluctuations in optical characteristics. Therefore, by disposing a polymer film having an elastic modulus that cancels out the dimensional change of the polarizer in the polarizing plate, the distortion due to the environment is reduced, and the elastic modulus is reduced, whereby the light leakage is significantly reduced. I understood.

The object of the present invention was achieved by the following polarizing plates (1) to (6) and the liquid crystal display devices (7) and (8) below. (1) (a) polymer film, (b) polarizing film, and (c)
A polarizing plate comprising an optical compensation film having an optically anisotropic layer comprising a liquid crystalline compound on a polymer substrate, wherein the polymer film has an elastic modulus of 4 GPa or more. (2) The polarizing plate according to (1), wherein the polarizing film (b) is sandwiched between the polymer film (a) and the polymer substrate (c). (3) The polarizing plate according to (1) or (2), wherein the polymer film (a) is made of cellulose acetate. (4) The polarizing plate according to (1) to (3), wherein the polymer film (a) contains a metal oxide having an average particle size of 1 nm to 400 nm in an amount of 1% by volume to 99% by volume. (5) The polarizing plate according to (4), wherein the metal oxide is aluminum oxide or silicon dioxide. (6) The liquid crystalline compound used for the optically anisotropic layer is a discotic liquid crystalline compound, the plane of the discotic structural unit is inclined with respect to the surface of the polymer substrate, and the plane of the discotic structural unit and the polymer substrate. The polarizing plate according to any one of (1) to (5), wherein the angle formed with the surface changes in the depth direction of the optically anisotropic layer. (7) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged on both sides thereof, wherein the polarizing plate comprises a polarizing film and two transparent protective films arranged on both sides thereof.
A liquid crystal display device in which at least one polarizing plate is the polarizing plate according to any one of (1) to (6). (8) The liquid crystal display device according to (6), wherein the liquid crystal cell is an OCB mode, VA mode or TN mode liquid crystal cell.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate of the present invention has an elastic modulus of 4G.
It is composed of a polymer film having Pa or more, a polarizing film, and an optically anisotropic layer made of a liquid crystalline compound. First,
The polymer film having an elastic modulus of 4 GPa or more used for the polarizing plate of the present invention will be described.

[Polymer Film] It is preferable to use a polymer film having a light transmittance of 80% or more. Examples of the polymer constituting the film include cellulose ester (eg, cellulose acetate, cellulose diacetate), norbornene-based polymer, and polymethylmethacrylate. Commercially available polymers (for norbornene-based polymers, Arton and Zeonex) may be used.
Cellulose ester is preferable, and lower fatty acid ester of cellulose is more preferable. The lower fatty acid means a fatty acid having 6 or less carbon atoms. 2 carbon atoms
It is preferably (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is particularly preferred. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may also be used. Further, even a conventionally known polymer such as polycarbonate or polysulfone which easily exhibits birefringence, the one whose expression is reduced by modifying the molecule described in WO00 / 26705 is used. You can also

The polymer film has an acetylation degree of 5
Preference is given to using cellulose acetate which is between 5.0 and 62.5%. Especially the degree of acetylation is 57.0 to 6
It is preferably 2.0%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is
According to the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (testing method for cellulose acetate, etc.). The viscosity average degree of polymerization (DP) of cellulose ester is
It is preferably 250 or more, more preferably 290 or more. Further, the cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight and Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.

In the case of cellulose ester, 2 of cellulose is used.
The hydroxyl groups at the 3-position, 3-position and 6-position 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, the substitution degree of the 6-position hydroxyl group of cellulose is preferably higher than that of the 2-position and 3-position. 30% or more of the 6-position hydroxyl groups relative to the total degree of substitution 4
It is preferably substituted with an acyl group at 0% or less,
Further, it is preferably 31% or more, and particularly preferably 32% or more. The substitution degree at the 6-position is preferably 0.88 or more. The 6-position hydroxyl group may be substituted with an acyl group having 3 or more carbon atoms (eg, propionyl, butyryl, valeroyl, benzoyl, acryloyl) in addition to the acetyl group. The substitution degree at each position can be measured by NMR. Cellulose ester with a high degree of substitution of the 6-position hydroxyl group,
Paragraph Nos. 0043 to 00 of JP-A No. 11-5851
44, the synthesis example 2 described in paragraph numbers 0048 to 0049, and the synthesis example 3 described in paragraph numbers 0051 to 0052.

[Elastic Modulus] The polymer film of the present invention needs to reduce the dimensional change of the polarizer, and physical properties required for the polymer film include thickness and elastic modulus (corresponding to bulk elastic modulus). The stress, which is the product, corresponds. It is possible to reduce the dimensional change of the polarizer by increasing the thickness of the polymer film, but considering the recent trend toward thinner LCDs, the elastic modulus can be adjusted to a constant thickness or a thin film. It is preferable to raise it. The elastic modulus of the present invention can be determined using a micro surface hardness meter (Fischer Scope H100VP-HCU manufactured by Fisher Instruments Co., Ltd.). Specifically, a diamond quadrangular pyramid indenter (tip facing angle; 136 °) is used to measure the indentation depth under a test load, and the test load is the geometric shape of the indenter generated by the test load. It is a value obtained from the universal hardness divided by the surface area of the indentation calculated from, and is the value when the indentation depth is 1 μm. The surface elastic modulus is a value that correlates with the elastic modulus of the bulk, and the value of the surface elastic modulus is used as the elastic modulus of the bulk in the present invention.

[Modulation of Elastic Modulus] The elastic modulus of the polymer film is 4 GPa or more, preferably 4.3 GPa or more, and more preferably 4.5 GPa or more. The upper limit is 9 GPa or less, preferably 8 GPa or less, more preferably 7 GPa or less, and further preferably 6 GPa or less. In order to obtain such an elastic modulus, there are a means of using a polymer material having a high elastic modulus, a means of using a polymerizable component or a crosslinking component in the polymer, and a means of incorporating metal oxide fine particles. Is preferable. Hereinafter, a cellulose acetate polymer will be described in detail as an example.

The metal oxide fine particles used in the present invention are preferably metal oxide particles having a Mohs hardness of 7 or more. Specific examples include silicon dioxide, titanium diacid, zirconium oxide, and aluminum oxide. Silicon dioxide (silica) or aluminum oxide (alumina), which has a small difference in refractive index from cellulose acetate, is more preferable.

The average particle diameter of these metal oxide fine particles is 1 nm or more and 400 nm or less, more preferably 5 nm.
Or more and 200 nm or less, more preferably 10 nm or more 1
00 nm or less is preferable. If it is less than 1 nm, it is difficult to disperse, and agglomerated particles are likely to be formed.

The amount of these fine particles added is 1 to 99% by volume of cellulose acetate ("1 to 99% by volume" means 1% by volume or more and 99% by volume or less. The same shall apply), 5 to 80% by volume is preferable, 5 to 50% by volume is more preferable, and 5 to 20% by volume is particularly preferable.

The term "substantially free of metal oxide" means that the content thereof is less than 1% by volume.

Generally, metal oxide fine particles have a large surface hydrophilicity and a poor affinity with cellulose acetate, so that the interface is easily broken and the film is cracked and it is difficult to improve the scratch resistance by simply mixing the two. Is. In order to improve the affinity between the inorganic fine particles and cellulose acetate,
The surface of the inorganic fine particles is preferably surface-treated with a surface decorating agent.

The surface modifier preferably has both a segment that binds to the metal oxide (inorganic fine particles) on the one hand and an organic segment that has a high affinity for the cellulose acylate on the other hand. As a functional group capable of forming a bond with a metal oxide, a metal alkoxide compound such as silane, aluminum, titanium, zirconium; phosphoric acid monoester, phosphoric acid diester, sulfuric acid monoester, or phosphoric acid group, sulfonic acid group, A compound having an anionic group such as a carboxylic acid group, a salt thereof, or an acid chloride thereof; a compound having an amino group, or a compound having an amide group is preferable. As the above organic segment,
Those having a structure having an affinity for cellulose acylate are preferable, and those having a polar group such as an ester group, an epoxy group or an ether group are more preferable. Particularly preferred is a metal alkoxide compound or a surface modifier having an anionic group and having an ester group, an epoxy group or an ether group.

Representative examples of these surface modifiers are listed below. Silane coupling _{agent: H 2 C = C (CH} 3) COOC 3 H 6 Si (OCH 3) 3 H 2 C = CHCOOC 3 H 6 Si (OCH 3) 3

[0021]

[Chemical 1]

ClCH ₂ CH ₂ —CH ₂ OC ₃ H ₆ Si (OCH ₃ ) ₃ R (OCH ₂ CH ₂ ) _n OC ₃ H ₆ Si (OCH ₃ ) ₃ R (OCH ₂ CH (CH ₃ )) _n OC ₃ H ₆ Si (OCH ₃ )
₃ ROCO (CH ₂ ) _n Si (OCH ₃ ) ₃ (In the above three formulas, n represents an integer of 1 to 10 and R represents an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl and butyl. .) CH ₃ COCH ₂ COOC ₃ H ₆ Si (OCH ₃ ) ₃ (CH ₃ CH ₂ O) ₃ POC ₃ H ₆ Si (OCH ₂ CH ₃ ) ₃ etc.

Titanate-based coupling agent: C ₁₇ H ₃₅ COOTi (OCH (CH ₃ ) ₂ ) _{3 and the} like. Specifically, Planeact (KRTTS, manufactured by Ajinomoto Co., Inc.)
KR46B, KR55, KR41B, KR38S, KR
138S, KR238S, 338X, KR44, KR9
SA) and other aluminum-based coupling agents: Specifically, Planeact AL-M (manufactured by Ajinomoto Co., Inc.)
Saturated carboxylic acid: CH ₃ COOH, C ₂ H ₅ COOH, etc. C _n H _{2n + 1} COOH (n represents an integer of 1 to 10) Unsaturated carboxylic acid: Oleic acid, etc. Hydroxycarboxylic acid: citric acid, tartaric acid Dibasic acid: Oxalic acid, malonic acid, succinic acid, etc.

Aromatic Carboxylic Acids: Benzoic Acid and Other Terminal Carboxylic Acid Ester Compounds: RCOO (C ₅ H ₁₀ COO) _n H (n = 1 to 5), H ₂ C = CHCOO (C ₅ H ₁₀ COO) _n H ( n = 1,
2, 3) etc. Phosphoric acid monoester, phosphoric diester: H ₂ C = C (CH ₃ ) COOC ₂ H ₄ OCOC ₅ H ₁₀ OPO
(OH) ₂ (H ₂ C = C (CH ₃ ) COOC ₂ H ₄ OCOC ₅ H ₁₀ O) ₂
POOH

Phosphonic acid-containing organic compound: Sulfonate monoester such as phenylphosphonic acid or sulfonic acid group-containing organic compound: Benzenesulfonic acid H ₂ C = C (CH ₃ ) COOC ₂ H ₄ OSO ₃ H, etc. Polyoxyethylene derivative: Poly Oxyethylene aryl ether Polyoxyethylene alkyl ether Polyoxyethylene aryl ester Polyoxyethylene alkyl ester, etc.

The surface modification of these fine particles is preferably performed in a solution. Fine particles of metal oxide are added to the solution in which the surface modifier is dissolved, and the mixture is treated with ultrasonic waves, a stirrer, a homogenizer, a dissolver, a planetary mixer, a paint shaker, a sand grinder, a kneader, etc. while stirring and dispersing. It is preferable.

The solution for dissolving the surface modifier is preferably an organic solvent having a large polarity. Specific examples thereof include known solvents such as alcohols, ketones, and esters, but a solvent having the same composition as the solvent for the cellulose acylate dope is preferable.

The metal oxide fine particles can be mixed with the cellulose acylate by adding the metal oxide fine particles to the cellulose acylate dope and mixing / dispersing the metal oxide fine particles. A method of adding fine particles to the dope of cellulose acylate is preferable. It is preferable to further disperse after addition, a dissolver, a planetary mixer, a sand grinder, a kneader,
It is preferable to uniformly mix and disperse with a roll mill or the like.

The method for producing the cellulose acetate film filled with the metal oxide in the present invention will be described.
As a method and equipment for producing the cellulose acetate film of the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acetate solution) prepared in the dissolution tank (pot) is temporarily stored in a stock tank, and the bubbles contained in the dope are defoamed to make the final preparation. The dope is sent from the dope outlet to the pressure die through a pressure metering gear pump that can accurately deliver the dope by the number of revolutions, and the dope is running endlessly from the casting port (slit) of the pressure die. The film is evenly cast on the support of a certain portion, and the dope film (also referred to as a web) which is dry and dried is peeled from the support at a peeling point where the support almost makes one turn. Both ends of the obtained web are sandwiched by clips and conveyed by a tenter while keeping the width and dried, and then conveyed by rolls of a drying device to complete the drying and wound by a winder to a predetermined length. The combination of the tenter and the roll group drying device can be changed according to the purpose.

In the present invention, the cellulose acetate solution filled with the metal oxide may be cast as a monolayer liquid on a smooth band or a drum as a support, or a plurality of cellulose acetate having two or more layers. The liquid may be co-cast. When casting multiple cellulose acetate solutions,
Tandem casting may be performed to form a film while casting and stacking a cellulose acetate solution from a plurality of casting ports provided at intervals in the traveling direction of the support,
A film may be formed by co-casting a cellulose acetate solution from two adjacent casting ports. As a casting method for these, JP-A-6-13493 is known.
No. 3, or the method described in JP-A No. 11-198285 can be applied.

In front of the pressure die, which is the casting port,
It is also possible to form a laminar flow of two types of cellulose acetate solutions and cast the laminar flow state.

For drying the dope on the support for producing the cellulose acetate film of the present invention, the drying temperature in the drying step is 30 to 250 ° C., particularly 40 to 180.
C is preferable, and it is described in JP-B-5-17844. Further, there is also a method of positively stretching in the width direction, and in the present invention, for example, JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, and JP-A-4-284111.
No. 298310 and No. 11-48271. The stretching of the film may be uniaxial stretching or biaxial stretching. The stretching ratio of the film (the ratio of the increase due to stretching to the original length) is preferably 10 to 30%.

The thickness of the finished (dried) cellulose acetate film of the present invention varies depending on the purpose of use, but is usually in the range of 5 to 500 μm, and further 20 to 2
The range of 50 μm is preferable, and the range of 30 to 180 μm is particularly preferable. In addition, as an optical use, 30 to 11
The range of 0 μm is particularly preferable.

In the case of a laminated film having two or more layers, the thickness of each highly elastic cellulose acetate layer filled with a metal oxide is preferably 5 μm or more and 100 μm or less, and 10 μm.
Above 50 μm is more preferable.

The thickness can be adjusted by adjusting the solid content concentration in the dope, the slit gap of the die die, the extrusion pressure from the die, the support speed, and the like.

The transmittance of the finished cellulose acetate film of the present invention is preferably 85% or more, and 90%.
The above is more preferable. Here, the transmittance means the average transmittance in the visible region.

The haze of the finished cellulose acetate film of the present invention is preferably 5% or less, and 1
% Or less is more preferable.

In the present invention, the surface treatment of the cellulose acetate film can improve the adhesion between the cellulose acetate film and each functional layer (eg, hard coat layer, undercoat layer and back layer). . For improving adhesion, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, plasma treatment, flame treatment, acid or alkali treatment can be used. The alkali saponification treatment preferable as the surface treatment of the present invention is usually carried out by a cycle in which the film surface is immersed in an alkaline solution, neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution, and the concentration of hydroxide ion is preferably 0.1 mol / liter to 3.0 mol / liter,
More preferably from mol / liter to 2.0 mol / liter. The temperature of the alkaline solution is preferably room temperature to 90 ° C, more preferably 30 ° C to 70 ° C. The film treated with the alkaline solution is then generally washed with water, after which an acidic aqueous solution is passed through and then washed again with water to obtain a surface-treated cellulose acylate film. At this time, the acid that can be used is hydrochloric acid, nitric acid, acetic acid, formic acid, chloroacetic acid, oxalic acid, etc., and the concentration thereof is preferably 0.01 mol / liter to 3.0 mol / liter, and 0.05 mol / liter. It is more preferably ˜2.0 mol / liter. When the acid is a dibasic acid such as sulfuric acid, the concentration is 0.
The amount is preferably 005 mol / liter to 1.5 mol / liter, more preferably 0.025 mol / liter to 1.0 mol / liter. In order to achieve the adhesion between the cellulose acetate film support of the present invention and the functional layer, it is also preferable to provide a subbing layer (adhesive layer) and apply a desired functional layer thereon.

It is also possible to provide an antistatic layer on at least one layer of the cellulose acetate film of the present invention. As the conductive material, a conductive metal oxide or a conductive polymer is preferable. A transparent conductive film may be provided by vapor deposition or sputtering. The conductive layer may be the outermost layer or the inner layer. The conductivity of the conductive layer has a resistance of 1
It is preferably from 0 ⁰ to 10 ¹² Ω, and particularly from 10 ⁰ to 1
It is preferably 0 ¹⁰ Ω. It is preferable to use conductive metal oxides, examples of which are ZnO, TiO ₂ , and Sn.
O ₂ , In ₂ O ₃ , MgO, BaO, MoO ₂ , V ₂ O _5, etc., or a complex oxide of these is preferable, and Zn is particularly preferable.
O, SnO ₂ or V ₂ O ₅ are preferred. Examples of the conductive ionic polymer compound include an ionene type polymer having a dissociative group in the main chain and a cationic pendant type polymer having a cationic dissociative group in the side chain. Further, as the conductive material of the present invention, an organic electron conductive material is also preferable, and examples thereof include polyaniline derivatives, polythiophene derivatives, polypyrrole derivatives, and polyacetylene derivatives.

In the present invention, a surfactant may be used in any of the functional layers, and any of nonionic, cationic and betaine can be used. Further, those fluorine-based surfactants are also preferably used as wetting improvers and antistatic agents for organic solvents. Further, in the present invention, it is possible to incorporate a slip agent into any layer on the cellulose acetate film. For example, polyorganosiloxane described in JP-B-53-292, US Pat. Fatty acid amides described in Japanese Patent Publication No. 275,146, Japanese Patent Publication No. 58-33541, and British Patent No. 92.
7,446, JP-A-55-126238 and 58.
-90633 higher fatty acid ester (10 carbon atoms
.About.24 fatty acids and C10-24 alcohol esters), and the like are known.

The hard coat layer has a function of imparting scratch resistance to the cellulose acetate base material of the present invention. It is preferable to provide this hard coat layer on the cellulose acetate film of the present invention. The hard coat layer includes a crosslinked binder polymer. The hard coat layer containing a cross-linked binder polymer is coated with a coating liquid containing a polyfunctional active energy ray-polymerizable compound and a polymerization initiator on a transparent substrate to polymerize the polyfunctional active energy ray-polymerizable compound. It can be formed by As a functional group,
Polymerizable unsaturated double bond groups are preferred. Examples of the polymerizable unsaturated double bond group include an acrylate group, a methacrylate group, and a vinyl group. An acrylate group is preferably contained from the viewpoint of reactivity.

The hard coat layer used in the present invention may be a known polymerizable resin such as a thermosetting resin and an active energy ray-polymerizable resin, and the active energy ray-polymerizable resin is preferable. Examples of thermosetting resins include reactive resins that utilize the crosslinking reaction of prepolymers such as melamine resins, urethane resins, and epoxy resins.

Examples of active energy rays include radiation, gamma rays, alpha rays, electron rays, and ultraviolet rays (including near ultraviolet rays, middle ultraviolet rays, far ultraviolet rays, and vacuum ultraviolet rays), with ultraviolet rays being preferred.

The polyfunctional active energy ray-polymerizable compound is preferably an ester of a polyhydric alcohol and acrylic acid or methacrylic acid. Examples of polyhydric alcohols are ethylene glycol, 1,4-cyclohexanediol, pentaerythritol, trimethylolpropane, trimethylolethane, dipentaerythritol,
Included are 1,2,4-cyclohexanetriol, polyurethane polyols and polyester polyols.
Trimethylolpropane, pentaerythritol, dipentaerythritol and polyurethane polyols are preferred. You may use together two or more types of polyfunctional active energy ray-polymerizable compounds.

Examples of active energy ray-polymerizable compounds include active energy rays such as pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, and particularly ultraviolet polymerizable compounds. The polyfunctional compound of is mentioned. The thickness of the hard coat layer can be appropriately selected, but is preferably 5 to 50 μm, and more preferably 10 to 30 μm.

By adding inorganic fine particles to the hard coat layer, the cross-linking shrinkage rate as a film can be improved, the flatness of the coating film can be improved, and the hardness of the coating film can be increased. Generally, inorganic fine particles are harder than organic substances and do not shrink due to UV irradiation or the like. Therefore, by adding the inorganic fine particles to the hard coat layer, the entire layer becomes hard and the scratch resistance is improved, and the shrinkage of the hard coat layer due to the crosslinking reaction is suppressed, and the deformation of the film provided with the hard coat layer can also be prevented. . However, since the inorganic fine particles have a low affinity with the binder polymer, even if the inorganic fine particles are added as they are, the space between the inorganic fine particles and the binder polymer is easily broken, and it is difficult to improve scratch resistance and deformation. Therefore, the affinity between the inorganic fine particles and the binder polymer can be improved by surface-treating the inorganic fine particles with the above-mentioned surface treatment agent having a high affinity for the fine particles.

As the inorganic fine particles, those having a high hardness are preferable, and inorganic particles having a Mohs hardness of 6 or more, preferably 7 or more are more preferable. Examples include silicon dioxide particles, titanium diacid particles, zirconium oxide particles, aluminum oxide particles, tin oxide particles, calcium carbonate particles, barium sulfate particles, talc, kaolin and calcium sulfate particles. Of these, silicon dioxide, titanium dioxide, aluminum oxide and zirconium oxide particles are particularly preferable.

[Polarizing Plate] In the polarizing plate of the present invention, the polymer film having an elastic modulus of 4 GPa or more produced as described above is bonded to one surface of the polarizing film, and the protective film ( Alternatively, it can be prepared by laminating an optically anisotropic layer). As the polymer used for the polarizing film, polybiyl alcohol (hereinafter referred to as PVA
Is described) is preferably used. PVA is generally a saponified product of polyvinyl acetate, but may contain a component copolymerizable with vinyl acetate, such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins, vinyl ethers. . Further, a modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like can also be used.

The degree of saponification of PVA is not particularly limited,
From the viewpoint of solubility, etc., it is preferably in the range of 80 to 100 mol%, particularly preferably in the range of 90 to 100 mol%. The degree of polymerization of PVA is not particularly limited, but it is preferably in the range of 1000 to 10000, and particularly preferably in the range of 1500 to 5000.

A polarizing film is obtained by dyeing PVA. Staining is performed by gas phase or liquid phase adsorption. As an example of dyeing in a liquid phase, PV in an aqueous solution of iodine-potassium iodide is used.
A method of immersing the A film may be mentioned. The content of iodine in the aqueous solution is preferably 0.1 to 20 g / l, the content of potassium iodide is 1 to 100 g / l, and the mass ratio of iodine to potassium iodide is preferably in the range of 1 to 100. Dyeing time is 30 to 5000 seconds, solution temperature is 5
It is preferably in the range of 50 to 50 ° C. As a dyeing method, not only dipping but also any means such as application or spraying of iodine or dye solution can be performed. The dyeing may be performed before or after the PVA stretching step,
It is particularly preferable to dye in a liquid phase before the stretching step because the membrane is appropriately swollen and the stretching becomes easy.

It is also preferable to dye with a dichroic dye in addition to iodine. Specific examples of dichroic dyes include azo dyes,
Examples thereof include stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. Water-soluble compounds are preferable, but not limited thereto. Further, it is preferable that hydrophilic substituents such as a sulfonic acid group, an amino group and a hydroxyl group are introduced into these dichroic molecules.

Specific examples of the dichroic molecule include, for example, C.I. Eye. direct. Yellow 12, Sea. Eye. direct. Orange 39, C.I. Eye. direct. Orange 72, C.I. Eye. direct. Red 39, sea. Eye. direct. Red 79, sea. Eye. direct. Red 81, sea. Eye. direct. Red 83, sea. Eye. direct. Red 89, sea. Eye. direct. Violet 48, C.I. Eye. direct. Blue 67, Sea. Eye. direct. Blue 90, Sea. Eye. direct. Green 59, C.I.
Eye. Acid. Red 37 etc. are mentioned. further,
JP-A-1-161202, JP-A-1-172906
JP-A-1-172907, JP-A-1-18360
No. 2, JP-A-1-248105, and JP-A 1-22652.
Specific examples of dichroic molecules include the dyes described in JP-A No. 05 and JP-A-7-261024. These dichroic molecules are used as free acids, or alkali metal salts, ammonium salts, and salts of amines. By blending two or more of these dichroic molecules, polarizing films having various hues can be manufactured. A compound (pigment) that exhibits a black color when the polarization axes of a polarizing plate (or polarizing element) that uses a polarizing film is crossed, or a mixture of various dichroic molecules that exhibits a black color is transmitted by the polarizing plate alone. The refractive index and the polarization rate are excellent, which is preferable.

In the process of producing a polarizing film by stretching PVA, it is preferable to use an additive for crosslinking PVA. Especially when the oblique stretching method used in the present invention is used, if the PVA is not sufficiently hardened at the exit of the stretching step, the orientation direction of the PVA may shift due to the tension of the step. Therefore, in the step before stretching or the stretching step,
It is preferable to dip PVA in the crosslinking agent solution or apply the crosslinking agent solution to PVA to contain the crosslinking agent. As the cross-linking agent, those described in US Reissue Patent No. 232897 can be used, but boric acids are most preferably used.

The stretching method used in the present invention is also applied to the production of a so-called polyvinylene-based polarizing film in which PVA or polyvinyl chloride is dehydrated and dechlorinated to form a polyene structure and polarized light is obtained by a conjugated double bond. be able to.

From the viewpoint of increasing the contrast ratio of the liquid crystal display device, the polarizing plate preferably has a high transmittance and a high polarization degree. The transmittance of the polarizing plate is 550 nm.
In the above light, it is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50%.
The polarization degree is 90 to 10 in the light having a wavelength of 550 nm.
It is preferably in the range of 0%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100%.

To increase the transmittance of the polarizing plate, the transmittance of the polymer film of the present invention may be increased, or the refractive index of the adhesive that integrates the polarizing film and the polymer film may be adjusted. To increase the transmittance of the polymer film, the thickness may be reduced or the haze may be reduced.

The adhesive for bonding the polarizing film and the polymer film or the polarizing film and the optically anisotropic layer is not particularly limited, but PVA-based resin (acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group, etc.) (Including the modified PVA of 1.) and an aqueous solution of a boron compound, etc., among which PVA-based resins are preferable. The thickness of the adhesive layer after drying is preferably in the range of 0.01 to 10 μm, particularly preferably in the range of 0.05 to 5 μm. Regarding the refractive index of the adhesive, it is preferable that the difference in refractive index from the cellulose acetate film is small, and the difference is 0.1.
It is preferably not more than 0.05, more preferably not more than 0.05, most preferably not more than 0.01. Further, as described above, it is also preferable to improve the polarization degree of the polarizing film itself.

[Optically Anisotropic Layer Comprising Liquid Crystalline Compound] In the optically anisotropic layer of the present invention, an optically anisotropic layer formed of a liquid crystalline compound is preferably provided on a polymer substrate. Is. An alignment film is preferably provided between the polymer substrate and the optically anisotropic layer provided thereon. The alignment film functions to align the liquid crystal compound used in the present invention in a certain direction. Therefore, the alignment film is essential for realizing the preferred embodiment of the present invention. However, if the alignment state is fixed after the liquid crystal compound is aligned, the alignment film plays its role, and thus it is not always essential as a constituent element of the present invention. That is, only the optically anisotropic layer on the alignment film in which the alignment state is fixed can be transferred onto the polarization film to produce the polarizing plate of the present invention.

[Alignment Film] The alignment film has a function of defining the alignment direction of the liquid crystal compound. The alignment film is formed by rubbing an organic compound (preferably a polymer), obliquely depositing an inorganic compound, forming a layer having microgrooves, or an organic compound (eg, ω-tricosanoic acid) by the Langmuir-Blodgett method (LB film). , Dioctadecyl methylammonium chloride, methyl stearate). Furthermore, an alignment film which has an alignment function by applying an electric field, a magnetic field, or light irradiation is also known. The alignment film is preferably formed by rubbing a polymer.

The alignment film is preferably formed by rubbing a polymer. Polyvinyl alcohol is the preferred polymer. Modified polyvinyl alcohol having a hydrophobic group bonded thereto is particularly preferable. The description of WO 01 / 88574A1 on page 43, line 24 to page 49, line 8 can be referred to for the alignment film.

[Optically Anisotropic Layer] In the invention, the optically anisotropic layer formed of the liquid crystalline compound is formed on the alignment film provided on the polymer substrate. The liquid crystalline compound used for the optically anisotropic layer includes a rod-shaped liquid crystalline compound and a discotic liquid crystalline compound. The rod-shaped liquid crystal compound and the discotic liquid crystal compound may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which the low-molecular liquid crystals are crosslinked and no longer show liquid crystallinity. The optically anisotropic layer can be formed by applying a coating liquid containing a liquid crystal compound and, if necessary, a polymerizable initiator and optional components onto the alignment film.

An organic solvent is preferably used as the solvent used for preparing the coating liquid. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethylsulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg. , Chloroform, dichloromethane, tetrachloroethane), ester (eg, methyl acetate, butyl acetate), ketone (eg, acetone, methyl ethyl ketone), ether (eg, tetrahydrofuran,
1,2-dimethoxyethane). Alkyl halides and ketones are preferred. You may use together 2 or more types of organic solvents. Application of the coating liquid is a known method (eg, wire bar coating method, extrusion coating method,
Direct gravure coating method, reverse gravure coating method, die coating method). The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm. A discotic liquid crystal compound is preferably used as the liquid crystal compound used in the present invention.

[Rod-shaped liquid crystalline compound] Examples of the rod-shaped liquid crystalline compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters,
Cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans and alkenylcyclohexylbenzonitriles are preferably used. The rod-shaped liquid crystal compound also includes a metal complex. Also, a liquid crystal polymer containing a rod-shaped liquid crystalline compound in the repeating unit,
It can be used as a rod-shaped liquid crystalline compound. In other words, the rod-shaped liquid crystal compound may be bonded to the (liquid crystal) polymer. For rod-like liquid crystalline compounds, refer to Chapter 4, Chapter 7 and Chapter 11 of Quarterly Chemistry Review, Volume 22, Chemistry of Liquid Crystals (1994), Chemical Society of Japan, and Liquid Crystal Device Handbook, Committee 142, Japan Society for the Promotion of Science. It is described in Chapter 3. The birefringence of the rod-shaped liquid crystal compound is 0.001.
It is preferably in the range of 0.7 to 0.7. The rod-shaped liquid crystal compound preferably has a polymerizable group in order to fix the alignment state. WO for rod-like liquid crystalline compounds
01 / 88574A1, page 50, line 7 to page 57, last line.

The optically anisotropic layer is composed of a rod-shaped liquid crystal compound or a later-described polymerizable initiator and optional additives (eg, plasticizer, monomer, surfactant, cellulose ester, 1, 3, 5).
-A liquid crystal composition (coating liquid) containing a triazine compound and a chiral agent) is applied on the alignment film to form the film.

[Discotic liquid crystalline compound] Examples of the discotic liquid crystalline compound include C.I. Destr
ade et al., Mol. Cryst. Volume 71, 1
The benzene derivative described on page 11 (1981), C.I. Report of Destrade et al., Mol. Cr
yst. 122, 141 (1985), Phys
ics lett, A, Vol. 78, page 82 (1990); Kohne et al., Angew. Chem. Volume 96, page 70 (1
984) and cyclohexane derivatives described in J.
M. Lehn et al., J. Chem. Commu
n. , Pp. 1794 (1985), J. Research report by Zhang et al. Am. Chem. Soc. Volume 116, 2
Examples thereof include azacrown type and phenylacetylene type macrocycles described on page 655 (1994). Furthermore, as the discotic liquid crystalline compound,
In general, those having a structure in which a linear alkyl group, an alkoxy group, a substituted benzoyloxy group or the like is linearly substituted as a straight chain with these as the mother nucleus of the molecular center and exhibit a liquid crystallinity. However, it is not limited to these as long as the molecule itself has negative uniaxiality and can give a certain orientation. Further, in the present invention, the optically anisotropic layer formed from the discotic liquid crystalline compound does not need to be the final product, and for example, a low molecular discotic liquid crystalline compound may be heated or exposed to light. It also includes a group having a group that reacts with, etc., resulting in polymerization or crosslinking by reaction with heat, light, etc., resulting in high molecular weight and loss of liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284.

In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. However, when the polymerizable group is directly bonded to the discotic core, it becomes difficult to maintain the alignment state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystal compound having a polymerizable group is preferably a compound represented by the following formula (III).

(III) D (-LP) n wherein D is a discotic core; L is a divalent linking group, P is a polymerizable group, and n is 4-12. Is an integer. Discotic liquid crystalline compounds are also WO01 / 8
8574A1 page 58 line 6-65 line 8.

When the discotic liquid crystalline compound is used, the optically anisotropic layer is a layer having negative birefringence, and the plane of the discotic structural unit is inclined with respect to the polymer substrate surface The angle formed by the surface of the structural unit and the surface of the polymer substrate is preferably changed in the depth direction of the optically anisotropic layer.

The surface angle (tilt angle) of the disk-shaped structural unit is
Generally, it 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.
The tilt angle preferably increases with increasing distance.
Further, examples of changes 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. Even if the tilt angle includes a region where the tilt angle does not change, it is preferably increased or decreased as a whole. Furthermore, the tilt angle is preferably increased as a whole, and particularly preferably continuously changed.

The tilt angle of the disk-shaped unit on the support side can be adjusted by generally selecting the disk-shaped liquid crystalline compound or the material of the alignment film, or by selecting the rubbing treatment method. The tilt angle of the discoid unit on the surface side (air side) can be adjusted by selecting a discotic liquid crystal compound or another compound generally used together with the discotic liquid crystal compound. Examples of the compound used together with the discotic liquid crystalline compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. Further, the degree of change in the tilt angle can be adjusted by the same selection as above.

As a plasticizer, a surfactant and a polymerizable monomer used together with the discotic liquid crystalline compound, is it compatible with the discotic liquid crystalline compound and is it possible to change the tilt angle of the discotic liquid crystalline compound? Alternatively, any compound can be used as long as it does not disturb the orientation. Of these, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) are preferable. The amount of the above compound added is generally in the range of 1 to 50% by mass with respect to the discotic liquid crystalline compound, and
It is preferably in the range of -30% by mass. Further, by mixing and using a monomer having 4 or more reactive functional groups, it is possible to enhance the adhesion between the alignment film and the optically anisotropic layer.

As the polymer to be used with the discotic liquid crystalline compound, any polymer can be used as long as it is compatible with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound. You can 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 addition amount of the above-mentioned polymer is generally 0.1 to 10 relative to the discotic liquid crystalline compound so as not to hinder the orientation of the discotic liquid crystalline compound.
It is in the range of mass%, more preferably in the range of 0.1 to 8 mass%, and even more preferably in the range of 0.1 to 5 mass%.

The 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 performing alignment. It is obtained by maintaining the state (discotic nematic phase) and cooling. Alternatively, the optically anisotropic layer, a discotic liquid crystal compound and other compounds (further, for example, a polymerizable monomer, a photopolymerization initiator) is applied to the alignment film with a solution prepared by dissolving it in a solvent,
It is dried and then heated to the discotic nematic phase formation temperature and then polymerized (by irradiation with UV light, etc.),
It is obtained by 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 preferably 70 to 170 ° C.

[Fixation of Alignment State of Liquid Crystal Compound] The oriented liquid crystal compound can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization is preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (US Pat. Nos. 2,366,661 and 236).
7670), acyloin ether (US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin compound (US Pat. No. 2,722,512), polynuclear quinone compound (US Pat. No. 30461).
27, 2951758), a combination of triarylimidazole dimer and p-aminophenyl ketone (described in US Pat. No. 3,549,367), acridine and phenazine compounds (JP-A-60).
-105667, US Pat. No. 4,239,850) and oxadiazole compound (US Pat. No. 42)
12970 specification). The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass of the solid content of the coating liquid, and more preferably in the range of 0.5 to 5% by mass. Ultraviolet light is preferably used for light irradiation for polymerizing the liquid crystal compound. The irradiation energy is preferably in the range of 20 mJ / cm ^{2 to} 50 J / cm ² , and 20 to 5000 mJ / cm ^2.
More preferably in the range of ² , 100 to 800
More preferably, it is in the range of mJ / cm ² . Further, in order to accelerate the photopolymerization reaction, light irradiation may be carried out under heating conditions. A protective layer may be provided on the optically anisotropic layer. As described above, the preferred embodiment of the present invention can be realized by providing the optically anisotropic layer on the polymer substrate.

[Retardation of Polymer Substrate] In the present invention, the Re retardation value of the polymer substrate is 20.
It is preferable to adjust the Rth retardation value in the range of 70 to 400 nm and the Rth retardation value in the range of 70 to 400 nm. When two optically anisotropic layers are used in a liquid crystal display device, the Rth retardation value of the substrate is 70 to 250n.
It is preferably in the range of m. When a single optically anisotropic layer is used in the liquid crystal display device, the Rth retardation value of the substrate is preferably in the range of 150 to 400 nm. The birefringence of the base film (Δn: nx−
ny) is preferably in the range of 0.00028 to 0.020. In addition, the birefringence index in the thickness direction {(nx +
ny) / 2-nz} is preferably in the range of 0.001 to 0.04.

[Polymer Substrate] The polymer film is not particularly limited as long as it is a polymer film having a light transmittance of 80% or more, but in order to have the function of a protective film of a polarizing plate, a cellulose ester (eg, cellulose acetate, cellulose diester) may be used. It is preferably an (acetate) type polymer. It is preferable to use cellulose acetate having an acetylation degree of 55.0 to 62.5%. In particular, the acetylation degree is preferably 57.0 to 62.0%.

[Retardation Raising Agent] In order to adjust the retardation of the polymer film, particularly cellulose acetate film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation raising agent. The aromatic compound is used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acetate. You may use together two or more types of aromatic compounds. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

The aromatic hydrocarbon ring is a 6-membered ring (that is,
A benzene ring) is particularly preferable. The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, a 6-membered ring or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring.
The aromatic heterocycle generally has the largest number of 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, furazan ring, triazole ring, pyran ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,3
A 5-triazine ring is included. 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, A benzene ring and a 1,3,5-triazine ring are more preferable. 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 2
It is preferably from 20 to 20, more preferably from 2 to 12, even more preferably from 2 to 8, and most preferably from 2 to 6. The bonding relationship between two aromatic rings is (b) when forming a condensed ring (a).
It can be classified into a case where it is directly connected by a single bond and a case where it is connected through a linking group (c) (because it is an aromatic ring, a spiro bond cannot be formed). The connection relation may be any of (a) to (c). For such retardation increasing agents, WO01 / 88574A1 and WO00 / 2619A
1, JP-A Nos. 2000-111914 and 2000-27.
No. 5434 and Japanese Patent Application No. 2002-70009.

[Production of Polymer Substrate] It is preferable that the cellulose acetate film is produced from the prepared cellulose acetate solution (dope) by a solvent casting method. The above-mentioned retardation increasing agent is preferably added to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The dope before casting has a solid content of 18 to 35.
It is preferable to adjust the concentration so as to be%. The surface of the drum or band is preferably mirror-finished. Regarding the casting and drying methods in the solvent casting method, US Pat.
No. 67603, No. 2492078, No. 2492977.
No. 2,492,978, No. 2,607,704, No. 27.
No. 39069, No. 2739070, British Patent 6407
No. 31, 736892, each specification, Japanese Examined Patent Publication No. 45-4
554, 49-5614, and JP-A-60-1768.
34, 60-203430, 62-11503.
It is described in each publication of No. 5. The surface temperature of the dope is 10
It is preferable to cast on a drum or band at a temperature of not higher than 0 ° C. After casting, it is preferable to apply air for 2 seconds or more to dry. It is also possible to strip the obtained film from the drum or band and further dry it with hot 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, the time from casting to stripping can be shortened. 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.

The prepared cellulose acetate solution (dope) may be used to cast two or more layers of dope to form a film. The 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 10 to 40%. The surface of the drum or band is preferably mirror-finished. When casting multiple cellulose acetate solutions,
The film may be produced by casting a solution containing cellulose acetate from a plurality of casting holes provided at intervals in the traveling direction of the support, and stacking them. For example, JP-A-61-158414 and JP-A-1-
The methods described in the specifications of No. 122419 and JP-A No. 11-198285 can be used. Also, 2
A film may be formed by casting a cellulose acetate solution from one casting port. For example, Japanese Patent Publication Sho 60-
27562, JP-A-61-94724, JP-A-61
-947245, JP-A 61-104813, JP-A 61-158413, and JP-A 6-13493.
The method described in each specification of No. 3 can be used. Further, a flow of a cellulose acetate film described in JP-A-56-162617, in which a flow of a high-viscosity cellulose acetate solution is wrapped with a low-viscosity cellulose acetate solution and a high-viscosity and low-viscosity cellulose acetate solution is simultaneously extruded. The rolling method may be used.

The retardation of the cellulose acetate film can be adjusted by further stretching treatment. The draw ratio is preferably in the range of 3 to 100%. When the cellulose acetate film of the present invention is stretched, tenter stretching is preferably used, and in order to control the slow axis with high accuracy, it is possible to minimize the difference between the left and right tenter clip speeds and the release timing. preferable.

[Surface Treatment of Cellulose Acetate Film] The cellulose acetate film is preferably surface-treated. Specific methods include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment and ultraviolet irradiation treatment. In addition, JP-A-7-
It is also preferred to provide an undercoat layer as described in the specification of 333433. From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.

From the viewpoint of adhesion to the polarizing film, the surface treatment of the cellulose acetate film is particularly preferably acid treatment or alkali treatment, that is, saponification treatment of cellulose acetate. The surface energy is preferably 55 mN / m or more, 60 to 75
More preferably, it is in the range of mN / m. Hereinafter, the alkali saponification treatment will be specifically described as an example. The alkali saponification treatment is preferably carried out in a cycle of immersing the film surface in an alkali solution, neutralizing the film with an acid solution, washing with water and drying. Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution. The specified concentration of hydroxide ion is preferably in the range of 0.1 to 3.0N, more preferably in the range of 0.5 to 2.0N. Alkaline solution temperature is room temperature to 90 ° C
Is preferably in the range of 40 to 70 ° C., and more preferably in the range of 40 to 70 ° C.

The surface energy of a solid can be determined by the contact angle method, the wet heat method, and the adsorption method, as described in "Basic Wetting and Application of Wetting" (published by Realize Co., December 12, 1989). In the case of the cellulose acetate film of the present invention, it is preferable to use the contact angle method. Specifically, two kinds of solutions having known surface energies are dropped onto a cellulose acetate film, and at the intersection between the surface of the droplet and the film surface, the angle between the tangent line drawn to the droplet and the film surface is used. The surface energy of the film can be calculated by defining the angle containing the drop as the contact angle.

[Liquid Crystal Display Device] The polarizing plate using the above-mentioned cellulose acetate film is advantageously used for a liquid crystal display device, particularly a transmissive liquid crystal display device. The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates arranged on both sides of the liquid crystal cell. The liquid crystal cell carries liquid crystal between two electrode substrates. The polarizing plate of the present invention may be used for one or both of the polarizing plates. At this time, the (optically anisotropic) cellulose acetate film of the polarizing plate is arranged on the liquid crystal cell side. Liquid crystal cell is OCB mode, VA
Mode, ECB mode or TN mode is preferred.

The OCB mode liquid crystal cell is a bend alignment mode liquid crystal cell in which rod-shaped liquid crystal molecules are aligned in a substantially opposite direction (symmetrically) in the upper part and the lower part of the liquid crystal cell. Liquid crystal display devices using liquid crystal cells of bend alignment mode are disclosed in US Pat. Nos. 4,583,825 and 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
atory Bend) Also called liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.

When the polarizing plate of the present invention is an OCB mode liquid crystal display device, an optically anisotropic layer containing a discotic compound or a rod-shaped liquid crystal compound may be provided on the cellulose acetate film used for the polarizing plate. The optically anisotropic layer is formed by orienting a discotic compound (or a rod-shaped liquid crystal compound) and fixing the orientation state. Discotic compounds generally have a large birefringence. In addition, the discotic compound has various orientation forms. Therefore, by using the discotic compound, it is possible to produce a polymer film (optical compensation sheet) having optical properties that cannot be obtained by a conventional stretched birefringent film. A polymer film using a discotic compound is disclosed in JP-A-6-
214116, US Pat. Nos. 5,583,679, 5
There is a description in each specification of 646703 and West German Patent Publication 3911620A1.

In the VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied. VA
The mode liquid crystal cell includes (1) a VA mode liquid crystal cell in a narrow sense 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 (Japanese Patent Application Laid-Open No. 2-176625). (2) In order to widen the viewing angle, the VA mode is multi-domain (M
VA mode liquid crystal cell (SID97, Digest of tec)
h. Papers (Proceedings) 28 (1997) 845),
(3) A liquid crystal cell in a 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 of Japan Liquid Crystal Conference 58-59 (1998). )) And (4)
Includes SURVAIVAL mode liquid crystal cell (announced at LCD International 98).

The ECB mode is the oldest known liquid crystal mode and is described in many documents. In a 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 TN mode liquid crystal cell is a color TFT.
It is most widely used as a liquid crystal display device and is described in many documents.

[0091]

EXAMPLES In order to explain the present invention in detail, examples will be given below, but the present invention is not limited thereto. [Example 1] (Preparation of polymer film PF-1) At room temperature, 100 parts by mass of cellulose acetate having an average degree of acetylation of 60.3%, 7.8 parts by mass of triphenyl phosphate, 3.9 parts by mass of biphenyl diphenyl phosphate, The following retardation control agent 1 (trans form) 1.32 parts by mass, methylene chloride 587.69 parts by mass, methanol 50.85
A solution (dope) was prepared by mixing parts by mass. Surface modification of this dope (CH ₃ COO (C ₅ H ₁₀ COO) ₂ H
Alumina (aluminum oxide C manufactured by Nippon Aerogel Co., Ltd.) having a particle size of 13 nm was added so that the filler volume concentration was 5%. The obtained dope solution,
It 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 mass. The cellulose acetate film was peeled from the band and dried at 140 ° C. for 20 minutes. The residual amount of solvent in the obtained polymer film was 0.1% by mass.
Retardation control agent 1 (trans form)

[0092]

[Chemical 2]

The thickness of the obtained polymer film (PF-1) was 102 μm, and the elastic modulus was 4 GPa. The transmittance was 91% and the haze was 0.8%.

(Preparation of Polymer Film (PF-2))
All except that the volume concentration of the filler of alumina used in the polymer film (PF-1) was 20%.
A polymer film (PF-2) was obtained in the same manner as.

The obtained polymer film (PF)
-2) has a thickness of 102 μm and an elastic modulus of 4.5 G
It was Pa. The transmittance is 90% and the haze is 1.
It was 0%.

(Preparation of Polymer Base Material (PK-1)) At room temperature, 100 parts by mass of cellulose acetate having an average acetylation degree of 60.9% and retardation control agent 2 (trans)
Body) 4.6 parts by mass, triphenyl phosphate 7.8 parts by mass, biphenyldiphenyl phosphate 3.9 parts by mass, methylene chloride 594.61 parts by mass, and methanol 52.14 parts by mass to prepare a solution (dope). Prepared. 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 mass. The cellulose acetate film is peeled from the band, and transversely stretched at a stretching ratio of 28% using a tenter at 140 ° C. to 135 ° C.
And dried for 20 minutes. The obtained polymer substrate (PK-
The residual solvent amount of 1) was 0.1% by mass. Retardation control agent 2 (trans form)

[0097]

[Chemical 3]

The thickness of the polymer base material (PK-1) thus obtained was 92 μm, and the ellipsometer (M-150,
When the retardation value (Re) at a wavelength of 590 nm was measured using JASCO Corporation, it was 43n.
It was m. The retardation value (Rth) at a wavelength of 590 nm was measured and found to be 175 nm.

(Preparation of Polymer Base Material (PK-2)) At room temperature, cellulose triacetate (average acetylation degree: 6)
0.3%, viscosity average degree of polymerization 320, water content 0.4% by weight, viscosity of 6% by weight in methylene chloride solution 305 m
Pa · s, average particle diameter 1.5 mm and standard deviation 0.
Powder of 5 mm) 20 parts by mass, methyl acetate 58 parts by mass, acetone 5 parts by mass, methanol 5 parts by mass, ethanol 5 parts by mass, butanol 5 parts by mass, ditrimethylolpropane tetraacetate (plasticizer) 1.2 parts by mass. 1.2 parts by weight of triphenyl phosphate (plasticizer), 2,
4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5
-0.2 parts by mass of triazine (UV agent), 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)-
0.2 parts by mass of 5-chlorobenzotriazole (UV agent), 2- (2'-hydroxy-3 ', 5'-di-tert-
Amylphenyl) -5-chlorobenzotriazole (U
V agent) 0.2 parts by mass, C ₁₂ H ₂₅ OCH ₂ CH ₂ O-P (=
O)-(OK) ₂ (releasing agent) 0.02 parts by mass, citric acid (releasing agent) 0.02 parts by mass, and silica particles having a particle diameter of 20 nm (Mohs hardness: about 7) 0.05 parts by mass are mixed. To prepare a solution.

The cellulose triacetate used here had a residual acetic acid content of 0.01% by mass or less, and C
a is 0.05% by mass, Mg is 0.007% by mass,
Further, Fe was 5 ppm. The 6-position acetyl group was 0.95, which was 32.2% of all acetyl groups. The acetone extracted content was 11% by mass, and the ratio of the weight average molecular weight to the number average molecular weight was 0.5, showing a uniform distribution. The yellowness index is 0.3, the haze is 0.08, the transparency is 93.5%, and the T
g was 160 ° C., and the heat value of crystallization was 6.2 J / g.

Into another mixing tank, 2.25 parts by weight of the retardation control agent 1 (trans form), 16.0 parts by weight of methylene chloride and 1.39 parts by weight of methanol were added, and the mixture was stirred with heating. A retardation control agent solution was prepared. The retardation control agent solution was entirely added to the cellulose acetate solution and sufficiently stirred to prepare a dope. The obtained dope was cast and dried. The amount of residual solvent of the polymer base material (PK-2) is 0.5.
%Met.

The thickness of the obtained polymer substrate (PK-2) was 65 μm, and the ellipsometer (M-150,
When the retardation value (Re) at a wavelength of 590 nm was measured using JASCO Corporation, it was 8 nm.
Met. Further, the retardation value (Rth) at a wavelength of 590 nm was measured and found to be 78 nm.

(Optical Compensation Sheet with Optically Anisotropic Layer (KH
-1) Preparation) Polymer base material (PK-1) is 2.0N
After soaking in the potassium hydroxide solution (25 ° C) for 2 minutes,
It was neutralized with sulfuric acid, washed with pure water and dried. When the surface energy of PK-1 was determined by the contact angle method, it was 63 mN /
It was m. The formed film was rubbed in the direction of 45 ° with respect to the slow axis (measured at a wavelength of 632.8 nm) of the polymer substrate (PK-1).

[0104] (Alignment film coating liquid composition)   The following modified polyvinyl alcohol 10 parts by mass   Water 371 parts by mass   119 parts by mass of methanol   Glutaraldehyde (crosslinking agent) 0.5 parts by mass

[0105]

[Chemical 4]

(Formation of Optically Anisotropic Layer) 41.01 g of the following discotic (liquid crystalline) compound, ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) were formed on the alignment film. ) 4.06 g, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.35 g, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.35
g, sensitizer (Kayakyu DETX, Nippon Kayaku Co., Ltd.)
A coating solution prepared by dissolving 0.45 g of the above) in 102 g of methyl ethyl ketone was applied with a # 3 wire bar. This was attached to a metal frame and heated in a constant temperature bath at 130 ° C. for 2 minutes to orient the discotic compound. Next, UV irradiation was performed for 1 minute at 130 ° C. using a 120 W / cm high pressure mercury lamp to polymerize the discotic compound. Then, it stood to cool to room temperature. In this way, an optical compensation sheet with an optically anisotropic layer (KH-1) was produced. The Re retardation value of the optically anisotropic layer measured at a wavelength of 546 nm was 38 nm. The angle (tilt angle) between the disc surface and the first transparent support surface was 40 ° on average.

[0107]

[Chemical 5]

(Optical Compensation Sheet with Optically Anisotropic Layer (KH
-2) Preparation) Polymer base material (PK-2) is 2.0N
After soaking in the potassium hydroxide solution (25 ° C) for 2 minutes,
It was neutralized with sulfuric acid, washed with pure water and dried. When the surface energy of PK-2 was calculated by the contact angle method, it was 63 mN /
It was m. (Formation of Alignment Film) A coating liquid having the following composition was applied to the prepared PK-2 by a # 16 wire bar coater at 28 ml / m.
² applied. It was dried with hot air of 60 ° C. for 60 seconds and further with hot air of 90 ° C. for 150 seconds. Then, the formed film was rubbed in a direction parallel to the longitudinal direction of PK-2.

[0109] (Alignment film coating liquid composition)   10 parts by mass of the modified polyvinyl alcohol   Water 371 parts by mass   119 parts by mass of methanol   Glutaraldehyde (crosslinking agent) 0.5 parts by mass

(Formation of Optically Anisotropic Layer) 41.01 g of the discotic (liquid crystalline) compound, ethylene oxide-modified trimethylolpropane triacrylate (V
# 360, Osaka Organic Chemical Co., Ltd. 4.06 g, cellulose acetate butyrate (CAB551-0.2, Eastman Chemical Co., Ltd.) 0.90 g, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) ) 0.23 g, photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.35 g, sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.45 g
Was applied to a coating liquid dissolved in 102 g of methyl ethyl ketone with a # 3.6 wire bar. This is 130
The discotic compound was oriented by heating for 2 minutes in a constant temperature zone of ° C. Next, UV irradiation was carried out for 1 minute using a 120 W / cm high pressure mercury lamp in an atmosphere of 60 ° C. to polymerize the discotic compound. Then, it stood to cool to room temperature. In this way, an optically anisotropic layer was formed, and an optical compensation sheet (KH-02) was produced. R of the optically anisotropic layer measured at a wavelength of 546 nm
The e retardation value was 43 nm. The angle (tilt angle) between the disk surface and the first transparent support surface was 42 ° on average.

Example 1 Iodine was adsorbed to a stretched polyvinyl alcohol film to prepare a polarizing film, and a polyvinyl alcohol-based adhesive was used to prepare an optical compensation sheet (K
H-01) was attached to one side of the polarizing film. The polymer film (PF-1) was subjected to saponification treatment and was attached to the opposite side of the polarizing film using a polyvinyl alcohol adhesive. The transmission axis of the polarizing film and the slow axis of the polymer substrate (PK-01) were arranged so as to be parallel to each other. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal to each other. In this way, a polarizing plate (HB-1) was produced.

Example 2 Iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film, and a polyvinyl alcohol adhesive was used to prepare an optical compensation sheet (K
H-02) was attached to one side of the polarizing film. The polymer film (PF-2) was subjected to saponification treatment, and a polyvinyl alcohol-based adhesive was used to attach it to the opposite side of the polarizing film. The transmission axis of the polarizing film and the slow axis of the polymer substrate (PK-02) were arranged so as to be parallel to each other. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal to each other. In this way, a polarizing plate (HB-2) was produced.

Example 3 (Fabrication of Bend Alignment Liquid Crystal Cell) A glass substrate having an ITO electrode was provided with a polyimide film as an alignment film, and the alignment film was rubbed. The two glass substrates obtained were opposed to each other in such a manner that the rubbing directions were parallel to each other, and the cell gap was set to 6 μm. Δn is 0.13 in the cell gap
96 liquid crystal compounds (ZLI1132, manufactured by Merck Ltd.) were injected to prepare a bend alignment liquid crystal cell. The size of the liquid crystal cell was 20 inches. Two polarizing plates (HB-1) produced in Example 1 were attached so as to sandwich the produced bend alignment cell. The elliptically polarizing plate was arranged so that the optically anisotropic layer faced the cell substrate and the rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were antiparallel. A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. The normally white mode of white display 2V and black display 5V was adopted. Using a measuring instrument (EZ-Contrast160D, manufactured by ELDIM) with the transmittance ratio (white display / black display) as the contrast ratio, the viewing angle can be set in eight steps from black display (L1) to white display (L8). It was measured. The results are shown in Table 1.

[0114]

[Table 1]

(Evaluation of Frame Unevenness) Under an environmental condition of a temperature of 25 ° C. and a relative humidity of 60%, a backlight was continuously turned on for 5 hours, and a black display state was visually observed in a dark room to evaluate light leakage. As a result, no light leakage was observed on the display screen of the liquid crystal display device.

[Example 4] A pair of polarizing plates provided in a liquid crystal display device (AQUAS LC20C1S, manufactured by Sharp Corporation) using a TN type liquid crystal cell was peeled off, and the polarizing plate prepared in Example 2 was used instead. (HB-2), KH
-02 (optical compensation sheet) was attached to the observer side and the backlight side one by one via an adhesive so that it was on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be in the O mode. For the manufactured liquid crystal display device, a measuring instrument (EZ
-Contrast 160D, manufactured by ELDIM) was used to measure the viewing angle in 8 steps from black display (L1) to white display (L8). The results are shown in Table 2.

[Comparative Example 1] A liquid crystal display device (AQOS LC20C1S, manufactured by Sharp Corporation) using a TN type liquid crystal cell was used as a measuring instrument (EZ-Contrast160).
D, manufactured by ELDIM) was used to measure the viewing angle in eight steps from black display (L1) to white display (L8). The results are shown in Table 2.

[0118]

[Table 2]

(Evaluation of Frame Unevenness) Under an environmental condition of a temperature of 25 ° C. and a relative humidity of 60%, a backlight was continuously turned on for 5 hours, and a full black display state was visually observed in a dark room to evaluate light leakage. As a result, no light leakage was observed on the display screen of the liquid crystal display device of Example 4, but Comparative Example 1
A frame-like light leak was observed on the display screen.

[0120]

EFFECT OF THE INVENTION The present inventor uses a polarizing plate composed of a polymer film having a modulus of elasticity of 4 GPa or more, a polarizing film, and an optically anisotropic layer composed of a liquid crystalline compound to optically form a liquid crystal cell without side effects. We have succeeded in compensating for this and suppressing the increase of the frame-shaped transmittance in the liquid crystal display device.

Claims (2)

[Claims] 1. A polarizing plate comprising an optical compensation film having (a) a polymer film, (b) a polarizing film, and (c) an optically anisotropic layer comprising a liquid crystalline compound on a polymer substrate, wherein the polymer film Has a modulus of elasticity of 4 GPa or more. 2. A liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged on both sides thereof, wherein the polarizing plate comprises a polarizing film and two transparent protective films arranged on both sides thereof, at least A liquid crystal display device, wherein one polarizing plate is the polarizing plate according to claim 1.