KR20070102964A - Optical compensation sheet, and polarizing plate and liquid-crystal display device using the same - Google Patents

Abstract

An optical compensation sheet, a polarizing plate, and a liquid crystal display device using the same are provided to improve productivity by using an optical anisotropic layer. An optical compensation sheet includes an optical anisotropic layer. The optical anisotropic layer is formed with a bar-shaped liquid crystal compound having a polymerizable radical, a polymerizable compound, and a liquid crystal composition including a photo-polymerization initiator on a supporting body. The polymerizable compound includes two or more polymerizable radicals and two or more hydroxyl groups of one molecule. The optical compensation sheet further includes an orientation layer formed between the supporting body and the optical anisotropic layer. The orientation layer includes a compound having the polymerizable radical.

Description

Optical compensation sheet, and polarizing plate and liquid crystal display device using the same {OPTICAL COMPENSATION SHEET, AND POLARIZING PLATE AND LIQUID-CRYSTAL DISPLAY DEVICE USING THE SAME}

[Patent Document 1] Japanese Patent Application Laid-Open No. 9-80424

[Patent Document 2] Japanese Patent Application Laid-Open No. 11-133408

[Patent Document 3] Japanese Patent Application Laid-Open No. 11-305217

[Patent Document 4] Japanese Patent Application Laid-Open No. 10-307291

This invention belongs to the field of the novel optical compensation sheet, and the polarizing plate and liquid crystal display device using the same. This invention also belongs to the technical field of the method of controlling the orientation order of a liquid crystalline compound. Moreover, this invention relates to the technical field of a liquid crystal display device, The display is performed by applying the electric field of a horizontal direction to the liquid crystalline compound especially oriented in a horizontal direction, The liquid crystal display of in-plane switching (IPS) mode or FFS mode. Device and the like.

As a liquid crystal display device, the method of hanging an electric field in the direction perpendicular | vertical to a board | substrate, the so-called TN mode, is widely used between two orthogonal polarizing plates, sandwiching the liquid crystal layer which twisted the nematic liquid crystal between. In this system, since the liquid crystal rises with respect to the substrate at the time of black display, when it is inclined, birefringence by the liquid crystal compound occurs and light leakage occurs. With respect to this problem, a method of optically compensating the liquid crystal cell and preventing the light leakage by using a film in which the liquid crystal compound is hybrid oriented has been put into practical use. However, even when a liquid crystal compound is used, it is very difficult to completely optically compensate a liquid crystal cell without a problem, and it has caused the problem that reversal of harmonics in the screen downward direction cannot be suppressed.

In order to solve this problem, the alignment is divided by a projection or a slit electrode formed in the panel by vertically aligning a liquid crystal display device in the so-called IPS mode or FFS mode, or a negative dielectric anisotropy, which applies a transverse electric field to the liquid crystal. One vertical orientation (VA) mode has been proposed and put into practical use. In recent years, these panels are developed not only for monitor use but also for television use. As a result, the brightness of the screen is greatly improved. For this reason, some light leakage in the oblique incidence direction of the diagonal position at the time of black display in these operation modes has been revealed as a cause of display quality deterioration.

As one of means for improving the viewing angle of the color tone and the black display, disposing an optical compensation material having birefringence property between the liquid crystal layer and the polarizing plate is also examined in the IPS and FFS modes. For example, a white or halftone display is inclined by arranging a birefringent medium having an optical axis orthogonal to each other having a function of compensating the increase or decrease of retardation of the liquid crystal layer at an inclination between the substrate and the polarizing plate. The thing which can improve the coloring at the time of looking directly at a direction is disclosed (refer patent document 1). In addition, as an optical compensation film, a method in which a birefringence is positive, an optical axis is in the plane of the film, and a birefringence is positive and the optical axis is in the normal direction of the film (see Patent Document 2), and the retardation is A method of using a biaxial optical compensation sheet having one wavelength (see Patent Document 3), a method of forming an optical compensation layer having a positive retardation on this surface by using a film having a negative retardation as a polarizing plate protective film ( Patent Document 4) has been proposed.

However, when optically compensating an IPS mode or FFS mode liquid crystal cell using an optical compensation sheet made of a stretched birefringent polymer film, it is necessary to use a plurality of films, and for the purpose of thinning, a discotic liquid crystal compound and An optical compensatory sheet using an optically anisotropic layer formed of a rod-like liquid crystal compound or the like has been developed.

The optical compensation sheet containing the optically anisotropic layer which consists of a liquid crystalline composition can be manufactured by forming the optically anisotropic layer containing an alignment film and a liquid crystalline compound on a transparent support body normally, and can be manufactured by UV light (the Liquid crystal compound is polymerized by external light) to cure the optically anisotropic layer. If this polymerization / curing reaction is insufficient, the adhesion between the alignment film and the optically anisotropic layer is insufficient, and an interlayer peeling occurs in the attaching process with the polarizing film or the attaching liquid crystal cell, or the alkali of the optically anisotropic layer which is a preliminary step of attaching. Improvement was desired because it causes the problem of cloudiness in the surface treatment process by.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical compensation sheet which contributes to the reduction of the leakage light and color taste change from the inclined direction of the liquid crystal display device, in particular, the liquid crystal display device in the IPS mode or the FFS mode, for example, from 60 °. To provide. Furthermore, an object of this invention is to make the attachment process with a polarizing film, and the adhesion process with a liquid crystal cell easier than before, and to improve a yield.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, it aims at the acceleration | stimulation of the polymerization reaction in the interface of an optically anisotropic layer and an oriented film, and the acceleration of the polymerization reaction of the air interface side of an optically anisotropic layer, and is made of the polyfunctional polymerizable monomer to an optically anisotropic layer. As a result of systematically examining the addition, it was found that the monomer having a specific structure exhibits a remarkable effect, and the present invention was reached. That is, this invention provides the following [1]-[6].

[1] An optical compensation sheet having an optically anisotropic layer formed of a liquid crystal composition containing a rod-like liquid crystal compound having a polymerizable group, a polymerizable compound, and a photopolymerization initiator on a support, wherein the polymerizable compound is one molecule Optical compensation sheet which has a 2 or more polymeric group and 2 or more hydroxyl group in the inside.

[2] The optical compensation sheet according to [1], having an alignment film between the support and the optically anisotropic layer.

[3] The optical compensation sheet according to [1] or [2], in which the alignment film contains a compound having a polymerizable group.

[4] A polarizing plate having the optical compensation sheet according to any one of [1] to [3].

[5] A liquid crystal display device having the polarizing plate according to [4].

[6] a liquid crystal cell having a polarizing film, the optical compensation sheet according to any one of [1] to [3], and a liquid crystal cell having a liquid crystal layer interposed between a pair of substrates, and at the time of black display; A liquid crystal display device in which an active compound is oriented substantially parallel to the surfaces of the pair of substrates, wherein Re (λ) of the support measured from the normal direction of the support in the optical compensation sheet is 20 nm to 200 nm, The Nz value of the support defined by Nz = Rth / Re + 0.5 is 0.8 to 7.0, Re (λ) of the optically anisotropic layer in the optical compensation sheet is -5nm to 5nm, Rth is -800nm to -50nm, A liquid crystal display device in which the liquid crystal compound in the optically anisotropic layer is homeotropically aligned, and the transmission axis of the polarizing film is parallel to the slow axis direction of the liquid crystal compound in the liquid crystal cell at the time of black display.

To practice the invention  Best form for

EMBODIMENT OF THE INVENTION Below, this invention is demonstrated in detail. Although description of the element | module described below may be made | formed based on typical embodiment of this invention, this invention is not limited to such embodiment. In addition, the numerical range displayed using "-" in this specification means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

In this specification, Re ((lambda)) and Rth ((lambda)) represent the in-plane retardation in the wavelength (lambda), and the retardation of the thickness direction, respectively. Any wavelength may be used as long as the measurement wavelength λ nm is in the range of the visible light region, specifically, in the range of 400 to 800 nm, but is preferably in the range of 400 to 750 nm, and more preferably in the range of 400 nm to 700 nm. In this specification, unless specifically determined, Re and Rth shall mean the value (or the value computed based on this value) measured at 530-600 nm. In-plane retardation Re is the value measured by making light of wavelength (lambda) nm inject into a film normal line direction in KOBRA 21ADH or WR (Oji Measurement Instruments Co., Ltd. product). When the film to be measured is represented by the uniaxial or biaxial refractive index ellipsoid, Rth is calculated by the following method.

Rth uses Re as the in-plane slow axis (judged by KOBRA 21ADH or WR) as the inclination axis (rotation axis) (when there is no ground axis, any direction in the film plane is the rotation axis). ) 6 points in total are measured by injecting light having a wavelength of λnm from the inclined direction in 10 degree steps from the normal direction to the 50 degree one side with respect to the film normal direction, and the assumption and input of the measured retardation value and average refractive index Based on the film thickness value obtained, KOBRA 21ADH or WR is calculated.

In the above description, in the case of a film having a direction in which the retardation value is zero at any inclination angle from the normal axis direction as the rotation axis, the retardation value at the inclination angle larger than the inclination angle is the symbol. After changing to negative, KOBRA 21ADH or WR is calculated.

In addition, the slow axis is set as the inclination axis (rotation axis) (when there is no ground axis, any direction in the film plane is the rotation axis), and the retardation value is measured from any inclined two directions, and the value and the average refractive index Based on the assumption value and the input film thickness value d, Rth may be calculated from the following equations (1) and (2).

Formula (1)

Re (θ) mentioned above represents the retardation value in the direction which inclined angle (theta) from a normal line direction.

Nx in Formula (1) represents the refractive index of the slow-axis direction in surface inside, ny represents the refractive index of the direction orthogonal to nx in surface, and nz represents the refractive index of the direction orthogonal to nx and ny.

Formula (2)

Rth = ((nx + ny) / 2-nz) × d

In the case where the film to be measured cannot be expressed by a single-axis or biaxial refractive ellipsoid, or a film without an so-called optical axis, Rth is calculated by the following method. Rth is inclined in 10 degree steps from -50 degrees to +50 degrees with respect to the film normal direction using the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) with respect to Re. 11 points of measurement were made by injecting light having a wavelength of λ nm from the direction, and KOBRA 21ADH or WR was calculated based on the measured retardation value, the assumption of the average refractive index, and the input film thickness value. From this calculated nx, ny, and nz, Nz = (nx-nz) / (nx-ny) is further calculated.

In addition, in this specification, a "ground axis" means the direction in which a refractive index becomes largest. In addition, in this specification, a "polarizing plate" is used by the meaning containing both a long polarizing plate and the polarizing plate cut | disconnected in the magnitude | size inserted in a liquid crystal device, unless it is specifically determined. In addition, in this specification, although a "polarizing film" and a "polarizing plate" are distinguished and used, a "polarizing plate" shall mean the laminated body which has a transparent protective film which protects this polarizing film on at least one surface of a "polarizing film."

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the optical compensation sheet of this invention is described in detail.

The optical compensation sheet of this invention is an optical compensation sheet which has an optically anisotropic layer containing the specific rod-shaped liquid crystalline compound which has a polymeric group on a support body. As for the orientation form, it is more preferable that it is homeotropic orientation.

[Bar-shaped liquid crystalline compound]

As a rod-shaped liquid crystalline compound in this invention, azomethine, azoxy, cyano biphenyl, cyano phenyl ester, benzoic acid ester, cyclohexane carboxylic acid phenyl ester, and cyano phenyl cyclohexane , Cyano substituted phenylpyrimidines, alkoxy substituted phenylpyrimidines, phenyldioxanes, tolans and alkenylcyclohexylbenzonitriles are preferably used. In addition, a metal complex is also contained in a rod-like liquid crystalline compound. Moreover, the liquid crystal polymer which contains a rod-like liquid crystalline compound in a repeating unit can also be used as a rod-shaped liquid crystalline compound in this invention. In other words, the rod-like liquid crystal compound may be bonded to the (liquid crystal) polymer. About rod-shaped liquid crystalline compound, for example, chemistry of quarterly chemical summary Vol. 22 liquid crystal (1994) Nippon Chemical Sculpture Chapter 4, 7 and 11, and liquid crystal device handbook Japanese Society for the Promotion 142th The things described in Chapter 3 of the Commission's edition can be adopted.

It is preferable that the birefringence of the rod-like liquid crystal compound is in the range of 0.001 to 0.7.

[Liquid crystalline compound having a polymerizable group]

The liquid crystal compound having a polymerizable group is not particularly limited as long as it is fixed by a polymerization reaction. For example, it is preferable that it is a liquid crystalline compound which has the polymeric group of [Formula 11] and [Formula 12] of Paragraph No. [0049]-[0050] of Unexamined-Japanese-Patent No. 2004-339193. Especially, the liquid crystalline compound which has an acrylate group and / or a methacrylate group is especially preferable. As a specific example of the rod-like liquid crystalline compound which has one or two acrylate groups and / or methacrylate groups, Paragraph No. 0082-0105 of Unexamined-Japanese-Patent No. 8-3111, Unexamined-Japanese-Patent No. Paragraphs [0022] to [0040] of Japanese Patent Application Laid-Open No. 9-281331, paragraphs [0115] to [0128] of JP 2000-281628, paragraphs [0250] to [0400] of JP 2002-220421 A And the compounds described in paragraphs [0056] to [0075] of JP-A-2003-48903. However, the rod-like liquid crystalline compound which has one or two acrylate groups and / or methacrylate groups is not limited to these.

The usage-amount is the range of 50-99.9 mass% of the total mass of an optically anisotropic layer, and the range of 70-99 mass% is preferable.

[Orientation order diagram]

S

1 의 범위에서 정의되는 값을 의미한다. S=0 이면, 액체 상태와 같이 완전하게 랜덤인 상태를 나타낸다. S=1 이면 결정과 같이 분자의 요동이 없고 1 방향으로 완전하게 배향하고 있는 상태를 나타낸다. 일반적으로 결정성 고분자 필름의 배향 질서도를 측정하는 데 X선 회절 패턴에 의해 측정되지만, 네마틱 액정성을 갖는 필름을 측정하는 경우, 이 방법으로는 감도가 악화되어 측정 방법으로서 바람직하지 않다. 본 명세서에 있어서 배향 질서도로는, 도쿄 인스트루먼트사 제조 「Nanofinder」에서 여기 레이저 파장을 532nm, 여기 레이저 출력을 시료부에서 약 400μW 의 측정 조건으로, 분광기 앞에 편광 해소자를 부착함으로써 측정을 실시한 값을 의미하는 것으로 한다. 측정 방법은 필름을 약 1∼2도로 경사지게 절삭(切削) 하고, 필름 중의 액정 재료층 중 표면 또는 계면 부근의 편광 라만 측정을 실시했다. 필름을 회전하고, 필름 면의 방위와 입사 레이저 편광의 전기장 방향이 이루는 각도를 바꾸어 몇 가지의 각도로 측정을 실시하고, 산란광의 성분 중 입사 레이저 편광 전기장과 평행한 편광 성분 I 평행과 수직인 편광 성분 I 수직을, 검광자를 사용하여 각각 분광 검출했다. 또한 액정성 화합물의 골격에 유래하는 피크를 갖는 밴드에 대해, 이론적으로 도출된 식에 의해 배향 오더 파라미 터 P2, P4 를 파라미터로서 최소 제곱법에 기초하는 피팅 해석을 실시하여, 배향 질서도를 얻었다.In the present specification, the orientation order (hereinafter, sometimes referred to as S) is used as an index indicating the degree of orientation of the polymer film and the degree of liquid crystal orientation.

S

Means a value defined in the range of 1. S = 0 indicates a completely random state such as a liquid state. S = 1 indicates a state in which there is no fluctuation of molecules like the crystal and is completely oriented in one direction. Generally, although it measures by the X-ray-diffraction pattern in order to measure the orientation order of a crystalline polymer film, when measuring the film which has nematic liquid crystallinity, a sensitivity deteriorates with this method and it is not preferable as a measuring method. In the present specification, the orientation order diagram means a value measured by attaching a polarization resolver in front of the spectrometer at a measurement condition of about 532 nm of excitation laser wavelength and about 400 μW of excitation laser output at a sample section in Tokyo Instrument manufactured "Nanofinder". I shall do it. The measuring method cut | disconnected the film in the inclination about 1-2 degree, and performed the polarization Raman measurement of the surface or interface vicinity among the liquid crystal material layers in a film. Rotate the film, change the angle formed between the orientation of the film plane and the direction of the electric field of the incident laser polarization, and measure at several angles, and the polarization perpendicular to the polarization component I parallel to the incident laser polarization electric field among the scattered light components. Component I perpendicular | vertical was respectively spectroscopically detected using the analyzer. In addition, about the band which has the peak derived from the skeleton of a liquid crystalline compound, fitting analysis based on the least square method as an parameter of orientation order parameters P2 and P4 is performed by the formula derived theoretically, Got it.

S

0.7 인 것이 바람직하고, 0.45

S

0.65 인 것이 보다 바람직하다. 배향 질서도가 이 범위에 있으면 상기 광학 이방성층을 액정 표시 장치에 부착했을 경우의 정면 콘트라스트의 향상에 기여한다. 상기 광학 이방성층이 스메틱 액정성을 나타내는 경우에는, 0.5

S

0.90 인 것이 바람직하고, 0.65

S

0.90 인 것이 보다 바람직하다.The orientation order of the present invention is 0.3 when the optically anisotropic layer exhibits nematic liquid crystallinity.

S

It is preferable that it is 0.7, and 0.45

S

It is more preferable that it is 0.65. If the orientation order is in this range, it contributes to the improvement of the front contrast at the time of attaching the said optically anisotropic layer to a liquid crystal display device. 0.5 when the optically anisotropic layer exhibits smectic liquid crystallinity

S

It is preferable that it is 0.90, 0.65

S

It is more preferable that it is 0.90.

[Alignment Film]

About the kind of specific polymer used for the oriented film in this invention, any of the polymer crosslinked by itself and a crosslinking agent can be used. Moreover, what combined these can also be used. As an example of the polymer used for the oriented film in this invention, the compound of Paragraph No. of Unexamined-Japanese-Patent No. 8-338913 is mentioned, for example. Preferably water-soluble polymers (for example, poly (N- methylol acrylamide), carboxymethyl cellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol), among them gelatin, polyvinyl alcohol and modified poly Vinyl alcohol is more preferable, and polyvinyl alcohol and modified polyvinyl alcohol are more preferable.

70-100% is preferable, as for the saponification degree of polyvinyl alcohol, 80-100% is more preferable, and 85-95% is further more preferable. It is preferable that the polymerization degree of polyvinyl alcohol is 100-3000.

The modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of the modified group include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, hydrocarbon groups substituted with fluorine atoms, thioether groups and polymerization. A group (unsaturated polymerizable group, an epoxy group, an aziridinyl group, etc.), an alkoxysilyl group (trialkoxy, dialkoxy, monoalkoxy), etc. are mentioned. As a specific example of these modified polyvinyl alcohol compounds, Paragraph No. of Unexamined-Japanese-Patent No. 2000-56310, Paragraph No. of Unexamined-Japanese-Patent No. 2000-155216, Unexamined-Japanese-Patent No. Paragraph number [0018]-[0022] of Unexamined-Japanese-Patent No. 2002-62426, etc. are mentioned.

[Orientation accelerator]

An orientation promoter is used for the purpose of improving the orientation of a rod-shaped liquid crystal in this invention. For example, the high molecular compound which has a fluoroalkyl group and a carboxylic acid in a side chain contributes to the said rod-shaped liquid crystal in the vertical orientation of the molecule | numerator of the said liquid crystalline compound in the air interface of an optically anisotropic layer. Specifically, the high molecular compound described as polymer A in Unexamined-Japanese-Patent No. 2005-282983 specification can be mentioned.

Although the preferable range of content of the said polymer A in a liquid crystalline composition differs according to the use, it is preferable that it is 0.005-8 mass% with respect to the gross mass of the composition (except the solvent in a coating liquid). It is more preferable that it is 0.01-5 mass%, and it is still more preferable that it is 0.05-1 mass%. Moreover, it is preferable that the addition amount of the repeating unit guide | induced from the said fluoroalkyl group containing monomer is 0.004 mass% or more and 6.5 mass% or less.

By setting it as such a range, it can prevent that drying of a coating film is not fully performed. Moreover, there exists a tendency for the performance (for example, uniformity of retardation etc.) as an optical film to improve more.

In addition, the onium salt contributes to the vertical alignment of the molecules of the rod-like liquid crystal compound on the interface side of the alignment film. The onium salt which can be used in the present invention contains an ammonium salt containing a nitrogen atom, a sulfonium salt containing a sulfur atom, a phosphonium salt containing a phosphorus atom, and the like, and more specifically, described in Japanese Patent Application No. 2005-282983. The onium salt as described in 0055]-[0086] is mentioned.

Although content of the onium salt in the said optically anisotropic layer changes preferable content by the kind, Usually, it is preferable that it is 0.01-10 mass% with respect to content of the liquid crystalline compound used together, and is 0.05-7 mass% More preferred. Although two or more types of onium salt may be used, it is preferable that the sum total of the usage-amount before using is the said range.

The liquid crystalline composition for optically anisotropic layer formation of the optical compensation sheet of this invention contains a polymeric compound which has two or more polymeric groups and two or more hydroxyl groups in 1 molecule as a polymeric compound (polymerizable monomer). In particular, when the rod-shaped liquid crystal having a polymerizable group is homeotropic alignment (vertical alignment), the polymerizable group is biased toward the air interface side, and the surface layer is hardly polymerized due to the polymerization inhibitory effect of oxygen. The polymerization reaction at can be promoted. Moreover, these monomers have a remarkable effect in improving adhesion with an orientation film. Although not limited by any theory, these phenomena are polymerizable and coatable in the upper and lower interfaces of the optically anisotropic layer because the above polymerizable compounds are unevenly distributed up and down the layer during the application and drying of the optically anisotropic layer. It is considered that this is because it is improved.

Although the monomer of the following structure is mentioned as a specific example of the polymeric compound which has two or more polymeric groups and two or more hydroxyl groups in 1 molecule, It is not limited to these.

[Formula 1]

1-50 mass% is preferable with respect to a liquid crystalline compound, and, as for content of the said polymeric compound in the liquid crystalline composition for optically anisotropic layer formation, it is more preferable that it is 3-30 mass%. In the present invention, other monomers may be used in combination. As a monomer preferably used together, the trifunctional, polyfunctional acryl ester, methacryl ester, styrene monomer, allyl as described in p38-p54 of the photosensitive material handbook, photopolymer round-table editing, and powder publication (1995), for example A system monomer is mentioned. In the case of using these monomers together, in the range of 5 mass%-120 mass% of the polymeric compound which has two or more polymeric groups and two or more hydroxyl groups in said 1 molecule, Preferably it is the range of 10-50 mass% Used in

In the liquid crystalline composition for optically anisotropic layer formation of the optical compensation sheet of this invention, you may contain another additive further. Examples of other additives include plasticizers, surfactants, polymers, and the like. It is preferable that these additives have compatibility with essential components, such as a liquid crystalline compound, and do not contribute to control of the inclination angle of a liquid crystalline compound, or do not inhibit orientation.

[Method for producing optically anisotropic layer]

The optical compensation sheet of this invention apply | coats a liquid crystalline composition (usually coating liquid) to a support body surface, Preferably the alignment film surface, orients the molecule | numerator of a liquid crystalline compound, and fixes the orientation state, for example. It can manufacture.

As a solvent used for manufacture of a coating liquid, an organic solvent is preferable. Examples of organic solvents include amides (eg N, N-dimethylformamide), sulfoxides (eg dimethylsulfoxide), heterocyclic compounds (eg pyridine), hydrocarbons (eg, Benzene, hexane), alkyl halides (e.g. chloroform, dichloromethane, tetrachloroethane), esters (e.g. methyl acetate, butyl acetate), ketones (e.g. acetone, methyl ethyl ketone), ethers ( Tetrahydrofuran, 1,2-dimethoxyethane) are included, for example, alkyl halides and ketones are preferred. Moreover, you may use together 2 or more types of organic solvents. When manufacturing an optical film with high uniformity, it is preferable that it is 25 mN / m or less, and, as for the surface tension of a coating liquid, it is more preferable that it is 22 mN / m or less.

Application of the coating liquid can be carried out by a known method (for example, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method), wire bar coating method, die Application by the coating method is preferred.

It is preferable to perform fixation by a photopolymerization reaction.

Examples of photopolymerization initiators include α-carbonyl compounds (US Pat. No. 2367661, US Pat. No. 2367670), acyloinether (US Pat. No. 2448828), α-hydrocarbon substituted aromatic acyloin compounds (US Patent 2722512), polynuclear quinone compounds (US Pat. No. 3046127, US Pat. No. 2951758), combinations of triarylimidazole dimers with p-aminophenylketone (described in US Pat. No. 3549367), Cridine and phenazine compounds (Japanese Patent Laid-Open No. 60-105667, described in each specification of US Patent 4239850) and oxadiazole compounds (described in US Patent 4212970 specification) are included. Moreover, the photoinitiator described in Japanese Patent Application 2005-273162 specification and Japanese Patent Application 2005-312276 specification is used effectively.

It is preferable that it is 0.01-20 mass% with respect to solid content of a coating liquid, and, as for the usage-amount of a photoinitiator, it is more preferable that it is 0.5-5 mass%.

It is preferable to use an ultraviolet-ray for the light irradiation for superposition | polymerization of a liquid crystalline compound (liquid crystalline molecule). It is preferable that irradiation energy exists in the range of 20mJ / cm <2> -50J / cm <2>, It is more preferable to exist in the range of 20mJ / cm <2> -5000mJ / cm <2>, It is more preferable to exist in the range of 100mJ / cm <2> -800mJ / cm <2>. . In order to promote the photopolymerization reaction, light irradiation may be performed under heating conditions or in an atmosphere where oxygen is less than the atmosphere by nitrogen substitution or the like.

It is preferable that the thickness of the optically anisotropic layer formed in this way is 0.1-20 micrometers, It is more preferable that it is 0.5-15 micrometers, It is further more preferable that it is 1-10 micrometers. Moreover, you may form a protective layer on an optically anisotropic layer.

[Support]

In this invention, you may form the said optically anisotropic layer on a support body. It is preferable that a support body is transparent, and it is preferable that specifically, light transmittance is 80% or more. It is preferable that a support body has small wavelength dispersion, and it is preferable that the ratio of Re (400) / Re (700) is less than 1.2 specifically ,. Especially, a polymer film is preferable. A part of retardation film may be sufficient as the support body of the said optically anisotropic layer, and all of retardation film may be sufficient as it. Moreover, the support body of the said optically anisotropic layer may function as a protective film (polarizing plate protective film) of a polarizing plate in this invention.

It is preferable that the optical anisotropy of a support body is small, It is preferable that in-plane retardation Re is -20 nm-20 nm, It is more preferable that it is -10 nm-10 nm, It is most preferable that it is -5 nm-5 nm. Moreover, when serving as a retardation film, it is preferable that Re is 20 nm-200 nm, It is more preferable that it is 40 nm-115 nm, It is still more preferable that it is 60 nm-95 nm. Moreover, it is preferable that Nz is 0.8-7.0, It is more preferable that it is 2.0-5.5, It is still more preferable that it is 2.5-5.0.

Examples of the polymer film serving as the support include films of cellulose esters, polycarbonates, polysulfones, polyethersulfones, polyacrylates, and polymethacrylates. A cellulose ester film is preferable and cellulose acetate is more preferable. It is preferable to form a polymer film by the solvent cast method. It is preferable that it is 20-500 micrometers, and, as for the thickness of a support body, it is more preferable that it is 40-200 micrometers. In order to improve the adhesion between the support and the layer (adhesive layer, vertical alignment layer or optically anisotropic layer) formed thereon, the support is subjected to surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame) Treatment). An adhesive layer (undercoat) may be formed on the support. Moreover, even when a support body is a film, such as a polymer which has a polymeric group, since adhesiveness with an optically anisotropic layer improves, it is preferable. In addition, in order to prevent adhesion | attachment of the back surface and the surface after providing slipperiness | lubricacy in a conveyance process or winding up to a support body or a long support body, 5%-40% of inorganic particles with an average particle size of 10-100 nm by solid content weight ratio. It is preferable to apply the mixed polymer layer to one side of the support or to form a covalent bond with the support.

Although the optical compensation sheet of this invention can be used independently in the member of a liquid crystal display device, etc., it can also be integrated with a polarizing plate and can be inserted into a liquid crystal display device as one member in a polarizing plate. The polarizing plate in which the optical compensation sheet of the present invention is integrated not only has a polarizing function but also contributes to the expansion of the viewing angle of the liquid crystal display device. Moreover, you may use the optical compensation sheet of this invention as a protective film of a polarizing film, and if it is set as such a structure, it contributes to thickness reduction of a liquid crystal display device.

Hereinafter, the polarizing plate using the optical compensation sheet of this invention is demonstrated in detail.

[Polarizing Plate]

The polarizing plate generally has a polarizing film produced by adsorbing and aligning a dichroic substance to a base film and a protective film attached to at least one side of the polarizing film. As a polymer used for the base film of a polarizing film, a polyvinyl alcohol (hereinafter PVA) type polymer is common. As a dichroic substance, iodine or a dichroic dye is used alone or in combination.

Although PVA used for a polarizing film here is what saponified polyvinyl acetate normally, you may contain the component copolymerizable with vinyl acetate like unsaturated carboxylic acid, unsaturated sulfonic acid, olefins, vinyl ether, for example. . Moreover, modified PVA containing an acetacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, etc. can also be used. Although the saponification degree of PVA is not specifically limited, From a viewpoint of solubility, polarization property, heat resistance, moisture resistance, etc., 80-100 mol% is preferable and 90-100 mol% is especially preferable. Moreover, although the polymerization degree of PVA is not specifically limited, 1000-10000 are preferable and, as for film strength, heat resistance, moisture resistance, and stretchability, 1500-5000 are more preferable. Moreover, it does not specifically limit about the syndiotactic of PVA, You can take arbitrary values according to the objective.

In order to dye and stretch PVA, and to manufacture a polarizing film, after extending | stretching a PVA film used as a disk by dry or wet method, it is immersed in the solution of iodine or a dichroic dye, of iodine or a dichroic dye. The method of extending | stretching and orienting a PVA film in a solution, the method of extending | stretching and orienting in a wet or dry manner, after immersing a PVA film in iodine or a dichroic dye, etc. are mentioned. Moreover, when forming a PVA original film by the solution film forming method, the method of previously containing a dichroic substance in a PVA solution can also be employ | adopted.

The manufacturing method by wet drawing of a typical polarizing plate is described below. First, a raw PVA film is preswelled with aqueous solution. Next, it is immersed in the solution of a dichroic substance, and a dichroic substance is made to adsorb | suck. Moreover, it uniaxially stretches in an advancing direction in aqueous solution of boron compounds, such as a boric acid. As needed, you may form a color taste adjustment bath, a hardening bath, etc. later. A protective film is affixed using adhesives, such as PVA, in the state dried to some extent. It is further dried to obtain a polarizing plate.

In the preliminary swelling liquid, you may add various organic solvents, an inorganic salt, a plasticizer, boric acids, etc. in aqueous solution.

As the dyeing solution, in the case of using iodine as the dichroic substance, for example, an iodine-potassium iodide aqueous solution can be used. It is preferable that the aqueous solution of iodine-potassium iodide is 0.1-20 g / liter of iodine, 1-100 g / liter of potassium iodide, and the weight ratio of iodine and potassium iodide is 1-100. The dyeing time is preferably 30 to 5000 seconds, and the liquid temperature is preferably 5 to 50 ° C. It is also preferable to contain a compound which crosslinks PVA, such as a boron compound, in a dyeing liquid. As for the boron compound in an extending | stretching bath, boric acid is especially preferable. The boric acid concentration is preferably 1 to 200 g / liter, more preferably 10 to 120 g / liter. The stretching bath may contain, in addition to the boron compound, inorganic salts such as potassium iodide, various organic solvents, dichroic dyes and the like. In addition to the dichroic dye, an inorganic salt, such as potassium iodide, a boron compound, etc. are contained in a color taste adjustment bath and a hardening bath as needed.

As a drawing process of PVA, in addition to the method of providing tension in the advancing direction of a continuous film, extending | stretching and orienting a film in a advancing direction as mentioned above, tension | tensile_strength in the width-length direction of a film by extending | stretching means, such as a tenter system. It is also possible to apply the method to orientate in the widthwise direction. It is preferable to perform extending | stretching 3 times or more in 1-axis direction, and 4.5 times or more is more preferable. You may perform biaxial stretching according to the purpose of use of a polarizing film. Although the film thickness after extending | stretching is not specifically limited, From a viewpoint of handleability, durability, and economy, 5-100 micrometers is preferable and 10-40 micrometers is more preferable. Although the temperature at the time of extending | stretching changes with extending conditions, Preferably it is 10-250 degreeC. When dry-stretching at the temperature of 100 degreeC or more, it is preferable to implement in inert gas atmosphere, such as nitrogen. Moreover, before dyeing the film extended | stretched previously, it is preferable to perform a crystallization process at the temperature of 100 degreeC or more.

As a dyeing method, not only the dipping method illustrated above but arbitrary means, such as application | coating or spraying of an iodine or dye solution, are possible. Moreover, not only the liquid layer adsorption mentioned above but also the adsorption by donation can be performed as needed. It is also preferable to dye with a dichroic dye. As a specific example of a dichroic dye, pigments, such as an azo pigment, a stilbene pigment, a pyrazolone pigment, a triphenylmethane pigment, a quinoline pigment, an oxazine pigment, a thiazine pigment, and an anthraquinone pigment, for example A system compound is mentioned. It is preferred to be water-soluble, with the exception of this. Moreover, it is preferable that hydrophilic substituents, such as a sulfonic acid group, an amino group, and a hydroxyl group, are introduce | transduced into these dichroic molecules.

Typical examples of dichroic molecules include CI direct, yellow 12, CI direct, orange 39, CI direct, orange 72, CI direct, red 28, CI direct, red 39, CI direct, red 79 and CI direct. Red 81, CI direct Red 83, CI direct Red 89, CI direct Violet 48, CI direct Blue 67, CI direct Blue 90, CI direct Green 59, CI acid Red 37, etc. are mentioned. . In addition, Japanese Unexamined Patent Publication No. Hei 1-61202, Japanese Unexamined Patent Publication No. Hei 1-72907, Japanese Unexamined Patent Publication No. Hei 1-72907, Japanese Patent Application Laid-Open No. Hei 1-183602, and Japanese Patent Application Laid-Open No. 2000-48105 And the dyes described in each of JP-A-2000-65205 and JP-A-7-261024. In particular, C.I.Direct.Red 28 (Congo Red) has long been known to be preferred for this use. These dichroic molecules are used as free acids or as salts of alkali metal salts, ammonium salts and amines.

These dichroic molecules can produce polarizers having various colors by blending two or more kinds. It is preferable to mix | blend various dichroic molecules so that the compound (pigment) which shows black, or black may be shown, when a polarizing axis orthogonally crosses a polarizing element as a polarizing element or a polarizing plate, and is excellent also in a single plate transmittance and a polarization rate.

It is preferable to include the additive which crosslinks to PVA in the manufacturing process of a polarizing film from a viewpoint of improving the heat resistance and moisture resistance of a polarizing film. As the crosslinking agent, those described in US Reissue Patent No. 232897 can be used, but boric acid and borax are preferably used practically. Moreover, it is also known to contain metal salts, such as zinc, cobalt, zirconium, iron, nickel, and manganese, in a polarizing film since it raises durability, and is preferable. These crosslinking agents and metal salts may be contained in any of the above-described pre-swelling bath, dichroic substance dyeing bath, stretching bath, curing bath, color tone bath, and the like, and the order of the steps is not particularly limited. There is no limitation in particular as an adhesive agent which bonds a protective film and a polarizing film, A well-known thing, such as a PVA system, a modified PVA system, a urethane system, an acryl type, can be used arbitrarily. 0.01-20 micrometers is preferable and, as for the thickness of an adhesive layer, 0.1-10 micrometers is more preferable.

As a polarizing plate of this invention, Preferably, it attaches to one surface of a polarizing film to the optical compensation sheet of this invention (more preferably, the support surface of the optical compensation sheet which has a support body contacts with a polarizing film), It is preferable to arrange | position the polymer film which consists of cellulose acylate etc. (it is set as the arrangement of an optically anisotropic layer / polarizing film / polymer film) on the surface of the other side.

The optical compensation sheet of this invention can be used for various liquid crystal display devices. It is preferable to use it for the liquid crystal display device of an IPS mode especially. When arrange | positioning the optical compensation sheet of this invention to the liquid crystal display device which has a liquid crystal cell and a pair of polarizing film which clamps the liquid crystal cell, between at least one of the said pair of polarizing films, and the said liquid crystal cell It is preferable to arrange. It is preferable that the optical compensation sheet of this invention determines the optical characteristic of an optically anisotropic layer so that the liquid crystalline compound in the liquid crystal cell in the black display of a liquid crystal display device may be compensated. Since the orientation state of the liquid crystal compound in the liquid crystal cell in black display differs with the mode of a liquid crystal display device, the preferable range of the optical characteristic of the said optically anisotropic layer also changes with a use. About the orientation state of the liquid crystalline compound in a liquid crystal cell, it describes in IDW'00, P411-414 of FMC7-2, etc.

As mentioned above, the optical characteristic of the optical compensation sheet of this invention differs in a preferable range according to the use, for example, which mode is used for optical compensation of the liquid crystal cell. In the IPS mode liquid crystal display device, Re of the optically anisotropic layer is preferably -5 to 5 nm, more preferably -3 to 3 nm, and Rth is preferably -800 to -50 nm, and -150 to -350 nm It is more preferable. In order to form an optically anisotropic layer exhibiting such optical characteristics, for example, a rod-like liquid crystalline compound is used and vertical alignment (orientation of the long axis direction of the rod-shaped molecules to be substantially perpendicular to the plane of the optically anisotropic layer), It is preferable to fix in the vertical alignment state.

About the liquid crystal display device of an IPS mode, it describes in Unexamined-Japanese-Patent No. 2003-207797, Unexamined-Japanese-Patent No. 2005-128498, etc. in detail, and can apply the content to this invention.

Example

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, usage amounts, ratios, treatment contents, treatment procedures, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the specific example shown below.

Example 1

(Production of Polymer Base Material (Support))

The following composition was put into the mixing tank, it stirred while heating, each component was melt | dissolved, and the cellulose acetate solution was produced. The solution was filtered using a retention particle size of 4 µm and a margin of time of 35 seconds (Advantech Co., No. 63) at 0.5 MPa (5 kg / cm 2) or less.

Cellulose Acetate Solution Composition Cellulose acetate with 60.9% acetonitrile (polymerization degree 300, Mn / Mw = 1.5) 100 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass Biphenyldiphenylphosphate (plasticizer) 3.9 parts by mass Methylene chloride (first solvent) 300 parts by mass Methanol (second solvent) 54 parts by mass 1-butanol (third solvent) 11 parts by mass

In another mixing tank, 16 mass parts of following retardation increasing agents A, 8 mass parts of retardation increasing agents B, 0.28 mass parts of silicon dioxide microparticles (average particle size: 100 nm), 80 mass parts of methylene chloride, and 20 mass parts of methanol A part was added and stirred while heating to prepare a solution A. 40 parts by mass of the solution A was mixed with 474 parts by mass of the cellulose acetate solution, and sufficiently stirred to prepare a dope.

[Formula 2]

[Formula 3]

The obtained dope was cast using a band softener. Residual solvent amount of 15% by mass of the film is stretched horizontally at a stretching ratio of 20% using a tenter under conditions of 130 ° C, held at 50 ° C for 30 seconds at the width after stretching, and then the clip is removed to remove the cellulose acetate film. Prepared. The amount of residual solvent at the time of completion | finish of extending | stretching is 5 mass%, and also it dried further and manufactured the film with the amount of residual solvent less than 0.1 mass%.

Thus, the obtained polymer description thickness was 80 micrometers. About the manufactured polymer base material, the light-incidence angle dependency of Re was measured using the automatic birefringence meter (KOBRA-21ADH, the product made by Oji Measurement Instruments Co., Ltd.). It is understood that Re is 60 nm and Rth is 200 nm, and from this, Nz is 3.8.

(Manufacture of Optical Compensation Sheet)

The saponification process of the surface of the manufactured polymer base material was performed, and on this film, the alignment film formation coating liquid of the following composition was adjusted to potassium hydroxide so that it might be set to pH 6.0. The alignment film coating liquid was applied with a wire bar coater at 20 ml / m 2. It dried for 60 second by the warm air of 60 degreeC, and 120 second by the warm air of 100 degreeC, and obtained the oriented film.

(Composition of Orientation Film-Forming Coating Liquid)

20 parts by mass of the following modified polyvinyl alcohol

0.05 parts by mass of potassium hydroxide

Glutaraldehyde 0.5 parts by mass

360 parts by mass of water

120 parts by mass of methanol

[Formula 4]

(Formation of Optically Anisotropic Layer)

First, the optically anisotropic layer formation solution which melt | dissolved the following composition in 102 g of methyl ethyl ketone was manufactured.

(The composition of the optically anisotropic layer)

Rod-like liquid crystalline compound (Ac-2) which has two following acrylate groups

45.07 parts by mass

0.45 parts by mass of the following onium salt (1)

Polymer A (following structure) 0.18 parts by mass

1.35 mass parts of photoinitiators (irgacure 907, Chiba Co., Ltd. product)

Sensitizer (Kayacure DETX, Nippon Gunpowder Co., Ltd.) 0.45 parts by mass

Denacol acrylate DA-314 (manufactured by M-3. Nagase Chemtex Co., Ltd.)

2.00 parts by mass

[Formula 5]

[Formula 6]

[Formula 7]

This coating liquid was apply | coated to the surface of the said oriented film by the wire bar, respectively. This was attached to the rim of a metal, it heated for 2 minutes in a 100 degreeC thermostat, and the rod-like liquid crystalline compound was orientated. Next, UV irradiation was carried out for 20 seconds by 120 W / cm high pressure mercury lamp at 60 degreeC, the rod-shaped liquid crystalline compound was bridge | crosslinked, and it was then cooled to room temperature, and the optically anisotropic layer was produced. Regarding the optically anisotropic layer produced, the light incidence angle dependence of Re was measured using an automatic birefringence meter (KOBRA-21 ADH, manufactured by Oji Measurement Instruments Co., Ltd.). 260 nm. Moreover, the optically anisotropic layer showed homeotropic orientation.

(Evaluation of the orientation order of the optically anisotropic layer)

The orientation order chart was calculated with reference to the method described on pages 651-654 of Proceedings of IDW'04,651 (2004) using "Nanofinder" manufactured by Tokyo Instruments. The orientation order was 0.54.

(Measuring degree of polymerization of optically anisotropic layer)

The polymerization degree of the surface layer of the optically anisotropic layer, manufactured by Nicolet, 710 FT-IR using SPECTROMETER and, 810㎝ derived from acrylate groups ^- from the peak area ratio of 1600㎝ ^-1 vicinity derived peak and ester groups of ^1, residual The composition of the acrylate group was calculated, and the degree of polymerization of the optically anisotropic layer was further calculated.

(Evaluation of Adhesiveness of Optical Compensation Sheet)

The adhesiveness of the optical compensation sheet was manufactured and evaluated according to the tape method of 8.5.2 base wood of JISK5400. However, Nitto Denko polyester adhesive tape NO31RH was used for evaluation. The results are shown in Table 1. 10 points for good adhesion and no peeling, and 0 points for lacking adhesion and the entire surface peeled off, and the numbers in between indicate good adhesion as the score is higher.

(Evaluation of Aptitude of Attachment Pretreatment of Optical Compensation Sheet)

The optical compensation sheet was immersed in 1.5 specified potassium hydroxide at 55 ° C. for 2 minutes, washed with water, immersed in 0.1 specified hydrochloric acid at 30 ° C. for 20 seconds, washed with water, and dried in order. Investigated. The results are shown in Table 1. (Circle) in this table is unchanged, transparent, (triangle | delta) is slightly cloudy, and x represents remarkable cloudy.

[Examples 2 to 10 and Comparative Examples 1 to 3]

The same operation as in Example 1 was repeated except that the components of the optically anisotropic layer of Example 1 were changed as shown in Table 1.

Table 1 shows the results of the polymerization degree measurement of the optically anisotropic layer, the adhesion evaluation of the optical compensation sheet, and the pretreatment process aptitude evaluation of the optical compensation sheet.

By Examples 1-10 and Comparative Examples 1-3, since the optical compensation sheet of this invention has favorable adhesiveness and there is no problem in a pre-adhesion process, it became clear that the yield of an adhesion process becomes high.

TABLE 1

As for the optical compensation sheet of this invention, the problem of the attachment process with a polarizing film or a liquid crystal panel is eliminated, and the yield of this process can be improved significantly.

Claims (6)

As an optical compensation sheet which has the optically anisotropic layer formed from the liquid crystal composition containing the rod-shaped liquid crystalline compound which has a polymeric group, a polymeric compound, and a photoinitiator on a support body, An optical compensation sheet, wherein said polymerizable compound has at least two polymerizable groups and at least two hydroxyl groups in one molecule. The method of claim 1, An optical compensation sheet having an alignment film between the support and the optically anisotropic layer. The method according to claim 1 or 2, The alignment film contains a compound having a polymerizable group. The polarizing plate which has the optical compensation sheet in any one of Claims 1-3. The liquid crystal display device which has a polarizing plate of Claim 4. It has a polarizing film, the liquid crystal cell which provided the optical compensation sheet of any one of Claims 1-3, and a liquid crystal layer between a pair of board | substrates, and the liquid crystalline compound in the said liquid crystal cell at the time of black display said A liquid crystal display device oriented substantially parallel to the surface of a pair of substrates, Re (λ) of the support measured from the normal direction of the support in the optical compensation sheet is 20 nm to 200 nm, and the Nz value of the support defined by Nz = Rth / Re + 0.5 is 0.8 to 7.0, and the optical Re (λ) of the optically anisotropic layer in the compensation sheet is -5 nm to 5 nm, Rth is -800 nm to -50 nm, and the liquid crystal compound in the optically anisotropic layer is homeotropically aligned, and the polarizing film The transmission axis is a liquid crystal display device parallel to the slow axis direction of the liquid crystal compound in the said liquid crystal cell at the time of black display.