JP2006071966A - Polarizing plate integrated optical compensation film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IPS (In-Plane Switching) type liquid crystal display device which is improved not only in display quality but also in a viewing angle characteristic with a simple constitution. <P>SOLUTION: The liquid crystal display device comprises at least a first polarizing film, a first retardation region which has positive refractive index anisotropy and has the optical axis substantially perpendicular to the layer surface, a second retardation region which has negative refractive index anisotropy and has the optical axis substantially parallel to the layer surface, a liquid crystal cell which holds a liquid crystal layer between a pair of substrates and a second polarizing film, wherein liquid crystal molecules in the liquid crystal layer align in parallel with respect to the surface of the pair of substrates when black is displayed. Retardation Rth in the thickness direction of the first retardation region which is defined by the relation of Rth=ä(nx+ny)/2-nz}×d by using refractive indexes nx, ny (nx≥ny) in the plane, refractive index nz in the thickness direction and thickness d is -30 nm to -250 nm and the slow axis of the second retardation region is orthogonal to the direction of the slow axis of the liquid crystal layer when black is displayed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to an in-plane switching mode liquid crystal display device that performs display by applying a horizontal electric field to liquid crystal molecules aligned in a horizontal direction. The present invention also relates to a polarizing plate integrated optical compensation film that contributes to optical compensation of a liquid crystal display device, particularly an in-plane switching mode liquid crystal display device.

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

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

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

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

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

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an IPS liquid crystal display device with a simple structure and not only display quality but also significantly improved viewing angle characteristics. Another object of the present invention is to provide a polarizing plate integrated optical compensation film that contributes to the improvement of viewing angle characteristics of a liquid crystal display device, particularly an IPS liquid crystal display device.

Means for solving the above-mentioned problems are as follows.
[1] A long polarizing film having an absorption axis parallel to the longitudinal direction, cellulose acetate propionate or cellulose propionate, in-plane refractive indices nx and ny (nx ≧ ny), thickness direction Rth defined by Rth = {(nx + ny) / 2−nz} × d using the refractive index nz and the thickness d is −30 nm to −250 nm, and Re = (nx−ny) × d A long polarizing plate-integrated optical compensation film having a long retardation film with Re defined as 50 nm or less.
[2] At least a polarizing film, a first retardation region having a positive refractive index anisotropy and an optical axis substantially perpendicular to the layer surface, and a negative refractive index anisotropy and an optical axis being a layer surface Is a polarizing plate-integrated optical compensation film having a second retardation region substantially parallel to the in-plane refractive index nx and ny (nx ≧ ny), a refractive index nz in the thickness direction, And the thickness d, the retardation Rth in the thickness direction of the first retardation region defined by Rth = {(nx + ny) / 2−nz} × d using the thickness d is −30 nm to −250 nm, and Re = (nx− ny) × d, the retardation Re of the second retardation region is 50 nm to 400 nm, and at least one of the first retardation region and the second retardation region is cellulose acetate propionate or cellulose Contains pionate Polarizing plate-integrated optical compensation film is Ilm.
[3] The polarizing film, the first retardation region, and the second retardation region are arranged in this order, and the slow axis of the second retardation region is the transmission axis of the polarizing film. [2] The polarizing plate-integrated optical compensation film according to [2], which is substantially parallel.
[4] The cellulose acetate propionate or the film containing cellulose propionate is a cellulose acylate film in which the acyl substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) [1] ] A polarizing plate integrated optical compensation film according to any one of [3] to [3].
(I) 2.82 ≦ SA + SP ≦ 3
(II) 0 ≦ SA ≦ 1.7
(III) 1.3 ≦ SP ≦ 2.9
(In the formula, SA and SP represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SP is the substitution degree of the propionyl group.)

[5] At least a first polarizing film, a first retardation region having a positive refractive index anisotropy and an optical axis substantially perpendicular to the layer surface, and an optical axis having a negative refractive index anisotropy. Includes a second retardation region that is substantially parallel to the layer surface, a liquid crystal cell that sandwiches the liquid crystal layer between a pair of substrates, and a second polarizing film. A liquid crystal display device aligned in parallel to the surface of a substrate, wherein Rth = {((in-plane refractive indices nx and ny (nx ≧ ny)), refractive index nz in the thickness direction, and thickness d. The retardation Rth in the thickness direction of the first retardation region defined by nx + ny) / 2−nz} × d is −30 nm to −250 nm, and the second position defined by Re = (nx−ny) × d The retardation Re of the retardation region is 50 nm to 400 nm, and the first retardation region and the first retardation region At least one of the retardation regions is cellulose acetate propionate or a film containing cellulose propionate, and the slow axis of the second retardation region is orthogonal to the slow axis direction of the liquid crystal layer during black display. Liquid crystal display device.
[6] The first polarizing film, the first retardation region, the second retardation region, and the liquid crystal cell are arranged in this order, and the slow axis of the second retardation region is the polarizing film. [5] The liquid crystal display device according to [5], which is substantially parallel to the transmission axis.
[7] The first retardation region, the liquid crystal cell, the second retardation region, and the first polarizing film are arranged in this order, and the slow axis of the second retardation region is the first polarizing film. [5] The liquid crystal display device of [5], which is substantially perpendicular to the transmission axis.
[8] It has a pair of protective films arranged with at least one of the first polarizing film and the second polarizing film interposed therebetween, and at least the position in the thickness direction of the protective film on the side close to the liquid crystal layer among the pair of protective films The liquid crystal display device according to any one of [5] to [7], wherein the phase difference Rth is 40 nm to −40 nm.
[9] It has a pair of protective films arranged with at least one of the first polarizing film and the second polarizing film interposed therebetween, and at least the position in the thickness direction of the protective film on the side close to the liquid crystal layer among the pair of protective films The liquid crystal display device according to any one of [5] to [8], wherein the phase difference Rth is 20 nm to -20 nm.
[10] It has a pair of protective films arranged with at least one of the first polarizing film and the second polarizing film interposed therebetween, and the thickness of the protective film on the side close to the liquid crystal layer of the pair of protective films is 60 μm or less. The liquid crystal display device according to any one of [5] to [9].
[11] A pair of protective films disposed between the first polarizing film and / or the second polarizing film, wherein the protective film on the side close to the liquid crystal layer is a cellulose acylate film or The liquid crystal display device according to any one of [5] to [10], which is a norbornene-based film.
[12] The liquid crystal display according to any one of [5] to [11], wherein the first retardation region and / or the second retardation region is adjacent to the first polarizing film and / or the second polarizing film. apparatus.
[13] Any of [5] to [12], wherein the first retardation region or the second retardation region is disposed at a position closer to the substrate on the opposite side to the viewing side of the pair of substrates of the liquid crystal cell. Liquid crystal display device.
[14] The cellulose acetate propionate or a film containing cellulose propionate is a cellulose acylate film in which the acyl substitution degree to the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) [5] ]-[13] Liquid crystal display device.
(I) 2.82 ≦ SA + SP ≦ 3
(II) 0 ≦ SA ≦ 1.7
(III) 1.3 ≦ SP ≦ 2.9
(In the formula, SA and SP represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SP is the substitution degree of the propionyl group.)

  The present invention includes at least a first polarizing film, a first retardation region, a second retardation region, a liquid crystal cell in which a liquid crystal layer is sandwiched between a pair of substrates, and a second polarizing film. In the liquid crystal display device in which the liquid crystal molecules of the layer are aligned parallel to the surfaces of the pair of substrates, the retardation Rth in the thickness direction is -30 nm to -250 nm, the refractive index anisotropy is positive, and the optical axis is on the layer surface. The first retardation region which is substantially perpendicular to the first retardation region, the in-plane retardation Re is 50 nm to 400 nm, the refractive index anisotropy is negative, and the optical axis is substantially parallel to the layer surface. Arrangement is made so that the slow axis of the second retardation region is perpendicular to the slow axis direction of the liquid crystal layer during black display, including two retardation regions, without changing the front direction characteristics at all. When viewed from an oblique azimuth direction, Reduction in contrast the absorption axis of the plate arises from the fact that deviates from 90 degrees, thereby particularly improving the reduction in the contrast of the 45-degree diagonal direction. In the present invention, cellulose acetate propionate or a film containing cellulose propionate is used in at least one of the two retardation regions. The film has optical properties required for the first retardation region or the second retardation region by adjusting the degree of acyl substitution to the hydroxyl group of cellulose acetate propionate or cellulose propionate and adjusting the production conditions. It can be filled with only one layer. Therefore, by using the film, a liquid crystal display device having a simple structure and improved viewing angle characteristics can be manufactured. In addition, since the film has the performance required as a protective film for the polarizing film, it can be made to function as a protective film by forming it on the surface of the polarizing film, and the viewing angle characteristics can be improved with a simpler configuration. The manufactured liquid crystal display device can be manufactured.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an embodiment of the liquid crystal display device of the present invention and its constituent members will be described in order. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  In the present specification, “parallel” and “orthogonal” mean that the angle is within a range of strictly less than ± 10 °. In this range, an error from a strict angle is preferably less than ± 5 °, and more preferably less than ± 2 °. Further, “substantially vertical” means within a range of less than ± 20 ° from a strict vertical angle. In this range, an error from a strict angle is preferably less than ± 15 °, and more preferably less than ± 10 °. Further, the “slow axis” means a direction in which the refractive index is maximized. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.

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

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a pixel region of the liquid crystal display device of the present invention. 2 and 3 are schematic views of an embodiment of the liquid crystal display device of the present invention.
[Liquid Crystal Display]
The liquid crystal display device shown in FIG. 2 includes polarizing films 8 and 20, a second retardation region 10, substrates 12 and 16, a liquid crystal layer 14 sandwiched between the substrates, and a first retardation region 18. . The polarizing films 8 and 20 are sandwiched between protective films 7a and 7b and 19a and 19b, respectively.

  In the liquid crystal display device of FIG. 2, the liquid crystal cell includes substrates 12 and 16 and a liquid crystal layer 14 sandwiched between them. The product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is optimal in the range of 0.2 to 0.4 μm for the IPS type having no twisted structure in the transmission mode. In this range, the white display luminance is high and the black display luminance is small, so that a bright and high-contrast display device can be obtained. An alignment film (not shown) is formed on the surfaces of the substrates 12 and 16 that are in contact with the liquid crystal layer 14, and the liquid crystal molecules are aligned substantially parallel to the surface of the substrate and are rubbed on the alignment film. The liquid crystal molecule alignment direction in the voltage non-application state or the low application state is controlled by the processing directions 13 and 17 and the like. Further, an electrode (not shown in FIG. 2) capable of applying a voltage to the liquid crystal molecules is formed on the inner surface of the substrate 12 or 16.

  FIG. 1 schematically shows the orientation of liquid crystal molecules in one pixel region of the liquid crystal layer 14. FIG. 1 shows the alignment of liquid crystal molecules in a very small area corresponding to one pixel of the liquid crystal layer 14 in the rubbing direction 4 of the alignment film formed on the inner surfaces of the substrates 12 and 16 and the substrates 12 and 16. It is the schematic diagram shown with the electrodes 2 and 3 which can apply a voltage to the liquid crystal molecule formed in the inner surface. When active driving is performed using a nematic liquid crystal having positive dielectric anisotropy as a field effect liquid crystal, the liquid crystal molecule alignment directions in a no voltage application state or a low application state are 5a and 5b. A display is obtained. When applied between the electrodes 2 and 3, the liquid crystal molecules change their alignment direction in the directions of 6 a and 6 b in accordance with the voltage. Usually, bright display is performed in this state.

In FIG. 2 again, the transmission axis 9 of the polarizing film 8 and the transmission axis 21 of the polarizing film 20 are arranged orthogonally. The slow axis 11 of the second retardation region 10 is orthogonal to the transmission axis 9 of the polarizing film 8 and the slow axis direction 15 of the liquid crystal molecules in the liquid crystal layer 14 during black display.
In the liquid crystal display device shown in FIG. 2, the configuration in which the polarizing film 8 is sandwiched between the two protective films 7a and 7b is shown, but the protective film 7b may be omitted. Further, although the polarizing film 20 is also sandwiched between the two protective films 19a and 19b, the protective film 19a on the side close to the liquid crystal layer 14 may be omitted.

  Another embodiment of the present invention is shown in FIG. The liquid crystal display device of FIG. 3 has the same configuration as the liquid crystal display device shown in FIG. 2 except that the first retardation region 18 is disposed between the polarizing film 8 and the second retardation region 10. In the liquid crystal display device of FIG. 3, the protective film 7b or the protective film 19a may be omitted. Further, a transparent support may be disposed between the first retardation region 18 and the protective film 7b or between the first retardation region 18 and the second retardation region 10. In the mode shown in FIG. 3, the second retardation region 10 has a slow axis 11 parallel to the transmission axis 9 of the polarizing film 8 and the slow axis direction of the liquid crystal molecules in the liquid crystal layer 14 during black display. 15 so as to be orthogonal to 15. In the aspect of FIG. 3, the first retardation region and the second retardation region may be disposed between the liquid crystal cell and the viewing-side polarizing film with reference to the position of the liquid crystal cell. You may arrange | position between the liquid crystal cell and the polarizing film of the back side. In any aspect, the second retardation region is disposed closer to the liquid crystal cell.

  2 and 3, the first retardation region 18 has a positive refractive index anisotropy and an optical axis substantially perpendicular to the layer surface, and Rth = {(nx + ny) / 2−nz } The retardation Rth in the thickness direction defined by × d is −30 nm to −250 nm. On the other hand, the second retardation region 10 has an in-plane retardation Re defined by Re = (nx−ny) × d of 50 nm to 400 nm. At least one of the first retardation region 18 and the second retardation region 10 is a film containing cellulose acetate propionate or cellulose propionate. Such a film exhibits only the optical characteristics required as the first retardation region or the second retardation region by adjusting the acyl substitution degree to the hydroxyl group of cellulose or by adjusting the production conditions. be able to. Further, since such a film can satisfy the performance required as a protective film for the polarizing film, in the embodiment of FIG. 2, when the second retardation region 10 is made of the film, the polarizing film can be obtained without the protective film 7b. When the film 8 and the second retardation region 10 are integrally formed, and the first retardation region 18 is made of the film, the polarizing film 20 and the first layer can be formed without the protective film 19a. By producing the phase difference region 18 integrally, the polarizing film 8 or the polarizing film 20 deteriorates even when placed in a harsh environment such as high temperature and humidity, and the display characteristics are deteriorated. Can be reduced. 3, when at least the first retardation region 18 is made of the film, the polarizing film 8 and the first retardation region 18 are integrally manufactured, and at least the second retardation region 10. Is made of the film, the polarizing film 8, the first retardation region 18 and the second retardation region 10 are integrally manufactured, so that even if there is no protective film 7b, it is severe under high temperature and humidity. Even when placed in an environment, it is possible to reduce the deterioration of the display characteristics due to the deterioration of the polarizing film 8.

  2 and 3 show a mode of a transmissive mode display device including an upper polarizing plate and a lower polarizing plate, the present invention is a mode of a reflection mode including only one polarizing plate. In such a case, since the optical path in the liquid crystal cell is doubled, the optimum value of Δn · d is about the above half value. The liquid crystal cell used in the present invention is not limited to the IPS mode, and any liquid crystal display device in which liquid crystal molecules are aligned substantially parallel to the surfaces of the pair of substrates during black display can be used. It can be used suitably. Examples thereof include a ferroelectric liquid crystal display device, an antiferroelectric liquid crystal display device, and an ECB type liquid crystal display device.

  The liquid crystal display device of the present invention is not limited to the configuration shown in FIGS. 1 to 3 and may include other members. For example, a color filter may be disposed between the liquid crystal layer and the polarizing film. Further, an antireflection treatment or a hard coat may be applied to the surface of the protective film of the polarizing film. Moreover, you may use what gave electroconductivity to the structural member. In the case of use as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a backlight using a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface. In this case, the arrangement of the backlight may be on the upper side or the lower side in FIGS. In addition, a reflective polarizing plate, a diffusion plate, a prism sheet, or a light guide plate can be disposed between the liquid crystal layer and the backlight. In addition, as described above, the liquid crystal display device of the present invention may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and the back side of the liquid crystal cell or the lower side of the liquid crystal cell. A reflective film is disposed on the inner surface of the substrate. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side.

  The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The present invention is particularly effective when applied to an active matrix liquid crystal display device using a three-terminal or two-terminal semiconductor element such as TFT or MIM. Of course, a mode applied to a passive matrix liquid crystal display device called time-division driving is also effective.

  Hereinafter, preferred optical characteristics of various members usable in the liquid crystal display device of the present invention, materials used for the members, manufacturing methods thereof, and the like will be described in detail.

In the present invention, at least one of the first retardation region and the second retardation region is made of cellulose acetate propionate or a film containing cellulose propionate. Cellulose acetate propionate is a cellulose acylate in which some of the hydroxyl groups of cellulose are substituted by acetyl groups and propionyl groups. Cellulose propionate is a cellulose acylate in which some of the hydroxyl groups of cellulose are substituted by propionyl groups. Rate. By using cellulose acetate propionate or cellulose propionate having different acyl group substitution degrees, films having desired optical properties can be produced. In order to satisfy the optical characteristics required for the second retardation region, it is preferable to use cellulose acetate propionate or cellulose propionate whose acyl substitution degree satisfies all of the following formulas (I) to (III). Preferably
(I) 2.82 ≦ SA + SP ≦ 3
(II) 0 ≦ SA ≦ 1.7
(III) 1.3 ≦ SP ≦ 2.9
(In the formula, SA and SP represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SP is the substitution degree of the propionyl group.)
More preferably,
(I) 2.83 ≦ SA + SP ≦ 2.99
(II) 0 ≦ SA ≦ 1.59
(III) 1.4 ≦ SP ≦ 2.85
And more preferably
(I) 2.85 ≦ SA + SP ≦ 2.98
(II) 0 ≦ SA ≦ 1.48
(III) 1.5 ≦ SP ≦ 2.8
It is.
Among these, when SA + SP is increased, the value of Rth can be decreased, and when SP is increased, the humidity dependency of retardation can be decreased.

Cellulose acylate such as cellulose acetate propionate or cellulose propionate that can be used in the present invention can be obtained by introducing a functional group biologically or chemically from cellulose ester compound and cellulose as a raw material. The basic principle of is described in Nobuhiko Ueda et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method of cellulose acylate is a liquid phase acylation method using a carboxylic acid anhydride-carboxylic acid-sulfuric acid catalyst. Specifically, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of carboxylic acid such as acetic acid, and then put into a precooled acylated mixture for esterification, and complete cellulose acylate (2nd, The total degree of acyl substitution at the 3rd and 6th positions is approximately 3.00). The acylated mixed solution generally contains a carboxylic acid as a solvent, a carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is generally used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system.

  After completion of the acylation reaction, water or hydrous acetic acid is added in order to hydrolyze the excess carboxylic anhydride remaining in the system. In order to partially neutralize the esterification catalyst, an aqueous solution of a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc carbonate, acetate, hydroxide or oxide) may be added. Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 20 to 90 ° C. in the presence of a small amount of an acylation reaction catalyst (generally, remaining sulfuric acid) to obtain a desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with a neutralizing agent as described above, or in water or dilute acetic acid without neutralization. The cellulose acylate solution is added (or water or dilute acetic acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

  The degree of polymerization of the cellulose acylate is preferably from 150 to 500, more preferably from 200 to 400, and even more preferably from 220 to 350 in terms of viscosity average degree of polymerization. The viscosity average degree of polymerization can be measured according to Uda et al.'S limiting viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). A method for measuring the viscosity average degree of polymerization is also described in JP-A-9-95538.

Cellulose acetate propionate or a film containing cellulose propionate can be produced by utilizing various methods such as an extrusion method and a solution casting method. In order to obtain predetermined optical characteristics after the film is formed, a stretching process can be further performed. In the case of producing the film by using a solution casting method, a plasticizer (preferably added amount is 0.1 to 20% by mass with respect to the cellulose ester, the same applies hereinafter) and a modifier (0. 1 to 20% by mass), an ultraviolet absorber (0.001 to 5% by mass), a fine particle powder (0.001 to 5% by mass) having an average particle diameter of 5 to 3000 nm, and a fluorosurfactant (0. 001-2 mass%), release agent (0.0001-2 mass%), deterioration inhibitor (0.0001-2 mass%), optical anisotropy control agent (0.1-15 mass%), infrared absorption You may contain additives, such as an agent (0.1-5 mass%). In addition, about the production method of a film, the details are described in the public technique 2001-1745 (issued on March 15, 2001, invention association) etc., and can be applied to this invention.
By subjecting the obtained unstretched and stretched cellulose acylate film to an appropriate surface treatment, adhesion between the cellulose acylate layer and other layers can be improved. The surface treatment includes glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, saponification treatment (acid saponification treatment, alkali saponification treatment), and glow discharge treatment and alkali saponification treatment are particularly preferable.
In addition, as described above, only the film containing cellulose acetate propionate or cellulose propionate can satisfy the optical characteristics required for the first retardation region or the second retardation region. The aspect in which the first retardation region or the second retardation region includes other birefringent film or retardation film together with cellulose acetate propionate film or cellulose propionate film is also included.

[First phase difference region]
The liquid crystal display device of the present invention has a first retardation region in which the refractive index anisotropy is positive and the optical axis is substantially perpendicular to the layer surface. The retardation in the thickness direction of the first retardation region defined by Rth = {(nx + ny) / 2−nz} × d using the refractive index nz in the thickness direction of the first retardation region and the thickness d. Rth is −30 nm to −250 nm. The more preferable range of Rth of the first retardation region varies depending on the optical characteristics of other optical members, and in particular, the Rth of the protective film (for example, triacetyl cellulose film) of the polarizing film located closer to the first optical retardation region. Depending on the situation, it varies greatly. In order to effectively reduce the light leakage in the oblique direction, Rth of the first retardation region is more preferably −50 nm to −200 nm, and further preferably −60 nm to −140 nm. On the other hand, the in-plane retardation Re of the first retardation region is not particularly limited, but is generally preferably 50 nm or less, more preferably 0 to 50 nm, and more preferably 0 to 20 nm. Is more preferable.

  The material and form of the first retardation region are not particularly limited as long as it has the optical characteristics. As described above, it may be composed of cellulose acetate propionate or a film containing cellulose propionate, or it may be composed of a birefringent polymer film made of other materials. A retardation film having a retardation layer formed by applying or transferring a polymer liquid crystalline compound may be used. Moreover, each can also be laminated | stacked and used.

<< First retardation region having birefringent polymer film >>
A retardation film made of a birefringent polymer film having the above optical properties can be easily formed by stretching a polymer film in the thickness direction of the film. In addition, cellulose acylates containing an Rth-suppressing additive that exhibits this optical property by simply casting without stretching can be suitably used. As such cellulose acylate, those described in Japanese Patent Application No. 2003-337683 can be used. Among these, the first retardation region is preferably a cellulose acetate propionate or a film containing cellulose propionate.

<< First Retardation Region Having Retardation Layer Formed from Liquid Crystalline Compound >>
As a retardation layer formed from a liquid crystalline compound having the above optical characteristics, a layer produced by applying a vinylcarbazole polymer and drying it (Japanese Patent Laid-Open No. 2001-091746), a cholesteric disco containing a chiral structural unit A layer formed by aligning the spiral axis of a tic liquid crystal compound or composition substantially perpendicularly to the substrate and then immobilizing it, and aligning a rod-like liquid crystal compound or composition having a positive refractive index anisotropy substantially perpendicularly to the substrate Examples of the layer formed after fixing are shown below (see, for example, JP-A-6-331826 and Japanese Patent No. 2853064). Furthermore, not only one retardation layer but also a plurality of retardation layers can be laminated to form the first retardation region showing the optical characteristics. Further, the first retardation region may be configured such that the entire laminated body of the support and the retardation layer satisfies the optical characteristics. As the rod-like liquid crystal compound to be used, those that take a nematic liquid crystal phase, a smectic liquid crystal phase, and a lyotropic liquid crystal phase in a temperature range in which the orientation is fixed are preferably used. In addition, in the presence of an additive, the rod-like liquid crystalline compound that is in the liquid crystal state in an appropriate orientation temperature range may be formed using a composition containing the additive and the rod-like liquid crystalline compound. preferable.

《Bar-shaped liquid crystalline compound》
The first retardation region of the present invention may be formed from a composition containing a rod-like liquid crystal compound. Examples of the rod-like liquid crystalline compound include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. In addition to the above low-molecular liquid crystalline molecules, high-molecular liquid crystalline molecules can also be used. As the liquid crystal molecules, those having a partial structure capable of causing polymerization or crosslinking reaction by actinic rays, electron beams, heat, or the like are preferably used. The number of the partial structures is 1 to 6, preferably 1 to 3.

When the first retardation region includes a retardation layer formed by fixing the rod-like liquid crystalline compound in the alignment state, the rod-like liquid crystal compound is substantially vertically aligned and fixed in that state. It is preferable to use a retardation layer. Substantially perpendicular means that the angle formed by the film surface and the director of the rod-like liquid crystal compound is in the range of 70 ° to 90 °. These liquid crystalline compounds may be aligned obliquely or may be changed so that the inclination angle gradually changes (hybrid alignment). Even in the case of oblique orientation or hybrid orientation, the average inclination angle is preferably 70 ° to 90 °, more preferably 80 ° to 90 °, and most preferably 85 ° to 90 °.
In addition, the coating solution solvent used for forming the retardation layer, other additives such as a polymerizable monomer and a polymerizable initiator, the retardation layer forming method, etc., which will be described later, are described below. It is the same.

[Second phase difference region]
The liquid crystal display device of the present invention has a second retardation region in which the refractive index anisotropy is negative and the optical axis is substantially parallel to the layer surface. The second retardation region is defined by Re = (nx−ny) × d using in-plane refractive indexes nx and ny (nx ≧ ny), a refractive index nz in the thickness direction, and a thickness d. The in-plane retardation Re is 50 nm to 400 nm. The slow axis of the second retardation region is arranged so as to be orthogonal to the slow axis direction of the liquid crystal layer during black display. In order to effectively reduce oblique light leakage, Re in the second phase difference region is more preferably 90 nm to 300 nm, and further preferably 120 nm to 250 nm. The retardation Rth in the thickness direction of the second retardation region is preferably −20 to −200 nm, and more preferably −60 to −130 nm.

  As long as the second retardation region has the optical characteristics, the material and form thereof are not particularly limited. As described above, it may be composed of cellulose acetate propionate or a film containing cellulose propionate, or it may be composed of a birefringent polymer film made of other materials. A retardation film having a retardation layer formed by applying or transferring a polymer liquid crystalline compound may be used. Moreover, each can also be laminated | stacked and used.

<< Second retardation region having birefringent polymer film >>
A retardation film made of a birefringent polymer film having the above optical characteristics can be easily formed by stretching a polymer film. The material of the polymer film is preferably a polymer having a negative intrinsic birefringence. Examples of the polymer having a negative intrinsic birefringence include styrene-based polymers. Styrenic polymers include styrene or homopolymers of styrene derivatives; copolymers of styrene or styrene derivatives and other monomers; graft copolymers obtained from styrene or styrene derivatives and other monomers; and mixtures of these polymers. Can be broadly classified.

  Examples of homopolymers of styrene or derivatives thereof include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, o-nitrostyrene, p-aminostyrene, p-carboxylstyrene, Mention may be made of homopolymers of p-phenylstyrene and 2,5-dichlorostyrene. Examples of copolymers of styrene or styrene derivatives with other monomers include styrene / acrylonitrile copolymer, styrene / methacrylonitrile copolymer, styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer Polymer, styrene / α-chloroacrylonitrile copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / acrylic acid copolymer, styrene / methacrylic acid Acid copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer, styrene / maleic anhydride copolymer, styrene / itaconic acid copolymer, styrene / vinyl carbazole copolymer, styrene / N-phenylacrylamide Copolymer, styrene / vinyl pyridine Copolymer, styrene / vinyl naphthalene copolymer, α-methyl styrene / acrylonitrile copolymer, α-methyl styrene / methacrylonitrile copolymer, α-methyl styrene / vinyl acetate copolymer, styrene / α-methyl Mention may be made of styrene / acrylonitrile copolymers, styrene / α-methylstyrene / methyl methacrylate copolymers, and styrene / styrene derivative copolymers. As the styrenic polymer, a graft copolymer obtained by graft-polymerizing at least one member of the group consisting of styrene, acrylonitrile and α-methylstyrene to a styrene / butadiene copolymer is preferable. Styrenic polymers are described in JP-A-4-97322 and JP-A-6-67169. The optical compensation sheet of the present invention that is optically negative uniaxial and has an optical axis parallel to the substrate can be obtained, for example, by uniaxially stretching a polymer having a negative intrinsic birefringence such as the styrene-based polymer.

<< Second retardation region having a retardation layer formed of a liquid crystalline compound >>
A retardation layer formed from a liquid crystalline compound having the above optical properties is obtained by applying a discotic liquid crystal compound having a negative refractive index anisotropy or a composition containing the same onto a support or a temporary support, The liquid crystal molecules can be formed by vertically aligning them, making their optical axes substantially horizontal to the substrate, and then immobilizing them. When it is formed on a temporary support, it can also be produced by transferring the retardation layer onto the support. Furthermore, not only one retardation layer but also a plurality of retardation layers can be laminated to form the second retardation region exhibiting the above optical characteristics. Further, the second retardation region may be configured so that the entire laminated body of the support and the retardation layer satisfies the optical characteristics.

《Discotic liquid crystalline compound》
The present invention includes various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystals). Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J. Am. Chem.Soc., Vol.116, page 2655 (1994)) can be used. The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284.

The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a discotic core of a discotic liquid crystalline compound can be considered. However, when a polymerizable group is directly connected to the discotic core, the alignment state is maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula.
D (-LP) _n
In the formula, D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12. Preferred specific examples of the discotic core (D), the divalent linking group (L) and the polymerizable group (P) in the above formula are (D1) to (D15) described in JP-A No. 2001-4837, respectively. ), (L1) to (L25), (P1) to (P18), and the contents described in the publication can be preferably used.

In an aspect in which the second retardation region has a retardation layer formed of a substantially vertically aligned discotic liquid crystalline compound, the retardation axis of the retardation layer is a slow phase of liquid crystal molecules during black display. It arrange | positions so that it may become orthogonal to an axial direction. Adjustment of Re in the second retardation region is performed by controlling the thickness of the discotic liquid crystal layer to be formed by coating. Further, the discotic liquid crystalline compound needs to align the disk surface substantially perpendicular to the film surface (average inclination angle in the range of 70 to 90 degrees). The discotic liquid crystalline compound may be oriented obliquely or may be changed so that the inclination angle gradually changes (hybrid orientation). Even in the case of oblique orientation or hybrid orientation, the average inclination angle is preferably 70 ° to 90 °, more preferably 75 ° to 90 °, and most preferably 80 ° to 90 °.
When the average inclination angle is smaller than this, the light leakage distribution becomes asymmetric.

<< Method for Forming Second Retardation Region Having Retardation Layer >>
A retardation layer formed of a discotic liquid crystalline compound is prepared by applying a coating liquid containing a discotic liquid crystalline compound, and optionally, the following polymerizable initiator, air interface vertical alignment agent and other additives on the support. It can be formed by coating on the vertical alignment film formed in (1), performing vertical alignment, and fixing the alignment state.

  As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

  The vertically aligned liquid crystal compound is preferably fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction of the polymerizable group (P) introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Description), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for polymerization of discotic liquid crystalline molecules is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the first retardation region including the optically illegal layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and most preferably 1 to 5 μm.

<< Vertical alignment film >>
In order to align the liquid crystalline compound vertically on the alignment film side, it is important to reduce the surface energy of the alignment film. Specifically, the surface energy of the alignment film is lowered by the functional group of the polymer, thereby bringing the liquid crystalline compound into a standing state. As the functional group for reducing the surface energy of the alignment film, a hydrocarbon group having 10 or more fluorine atoms and carbon atoms is effective. In order to allow a fluorine atom or a hydrocarbon group to exist on the surface of the alignment film, it is preferable to introduce a fluorine atom or a hydrocarbon group into the side chain rather than the main chain of the polymer. The fluoropolymer preferably contains fluorine atoms in a proportion of 0.05 to 80% by mass, more preferably in a proportion of 0.1 to 70% by mass, and in a proportion of 0.5 to 65% by mass. More preferably, it is most preferable to contain in the ratio of 1-60 mass%. The hydrocarbon group is an aliphatic group, an aromatic group or a combination thereof. The aliphatic group may be cyclic, branched or linear. The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not exhibit strong hydrophilicity, such as a halogen atom. The hydrocarbon group has preferably 10 to 100 carbon atoms, more preferably 10 to 60, and most preferably 10 to 40 carbon atoms. The main chain of the polymer preferably has a polyimide structure or a polyvinyl alcohol structure.

  Polyimide is generally synthesized by a condensation reaction of tetracarboxylic acid and diamine. A polyimide corresponding to a copolymer may be synthesized using two or more kinds of tetracarboxylic acids or two or more kinds of diamines. The fluorine atom or hydrocarbon group may be present in the repeating unit derived from tetracarboxylic acid, may be present in the repeating unit derived from diamine, or may be present in both repeating units. When introducing a hydrocarbon group into polyimide, it is particularly preferable to form a steroid structure in the main chain or side chain of the polyimide. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of vertically aligning the liquid crystalline compound. In this specification, the steroid structure is a cyclopentanohydrophenanthrene ring structure or a ring structure in which a part of the ring bond is a double bond in the range of an aliphatic ring (a range that does not form an aromatic ring). means.

  Further, as a means for vertically aligning the liquid crystalline compound, a method of mixing an organic acid with a polymer of polyvinyl alcohol, modified polyvinyl alcohol, or polyimide can be suitably used. As the acid to be mixed, carboxylic acid, sulfonic acid and amino acid are preferably used. You may use what shows the acidity among the below-mentioned air interface aligning agent. Moreover, quaternary ammonium salts can also be used suitably. The mixing amount is preferably 0.1% by mass to 20% by mass and more preferably 0.5% by mass to 10% by mass with respect to the polymer.

  The saponification degree of the polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. The polymerization degree of polyvinyl alcohol is preferably 100 to 5000.

  When aligning a discotic liquid crystalline compound, the alignment film is preferably made of a polymer having a hydrophobic group as a functional group in the side chain. The specific type of functional group is determined according to the type of liquid crystal molecule and the required alignment state. For example, the modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups 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, fluorine atoms Substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy) and the like can be mentioned. Specific examples of these modified polyvinyl alcohol compounds include, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426. And the like described in [0022].

  The alignment film is formed by using a polymer having a side chain having a crosslinkable functional group bonded to the main chain or a polymer having a crosslinkable functional group on a side chain having a function of aligning liquid crystal molecules. When the retardation film is formed using a composition containing a polyfunctional monomer, the polymer in the alignment film and the polyfunctional monomer in the retardation film formed thereon can be copolymerized. As a result, a covalent bond is formed not only between the polyfunctional monomers but also between the alignment film polymers and between the polyfunctional monomer and the alignment film polymer, and the alignment film and the retardation film are firmly bonded. Therefore, the strength of the optical compensation sheet can be remarkably improved by forming the alignment film using a polymer having a crosslinkable functional group. The crosslinkable functional group of the alignment film polymer preferably contains a polymerizable group in the same manner as the polyfunctional monomer. Specific examples include those described in paragraphs [0080] to [0100] in JP-A-2000-155216.

  Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent. Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [024] in JP-A-2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

  0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By adjusting in this way, even if the alignment film is used for a long time in a liquid crystal display device or left in a high-temperature and high-humidity atmosphere for a long time, sufficient durability without occurrence of reticulation can be obtained.

  The alignment film can be basically formed by applying a composition containing the polymer and the crosslinking agent, which are alignment film forming materials, onto a transparent support, followed by drying by heating (crosslinking) and rubbing treatment. it can. As described above, the crosslinking reaction may be performed at an arbitrary time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (eg, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the alignment film and also the phase difference layer surface reduces remarkably.

  The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient cross-linking, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is particularly preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is 4.5 to 5.5, and 5 is particularly preferable.

  The alignment film is preferably provided on the transparent support. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.

  For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, a method of obtaining the orientation by rubbing the surface of the orientation film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average.

  In order to uniformly align the discotic liquid crystalline compound, it is preferable to control the alignment direction with a rubbing-treated vertical alignment film, while it is preferable not to perform the rubbing treatment for the vertical alignment of the rod-like liquid crystalline compound. In addition, after aligning a liquid crystalline compound using an alignment film, the liquid crystalline compound is fixed in the alignment state to form a retardation layer, and only the retardation layer is formed on the polymer film (or transparent support). You may transcribe.

《Air interface vertical alignment agent》
Usually, since the liquid crystalline compound has a property of being inclined and aligned on the air interface side, it is necessary to control the alignment of the liquid crystalline compound vertically on the air interface side in order to obtain a uniformly vertically aligned state. . For this purpose, a phase difference film is formed by adding a compound that is unevenly distributed on the air interface side and that has the effect of vertically aligning the liquid crystalline compound by its excluded volume effect or electrostatic effect to the liquid crystal coating liquid. It is preferable to do this. The action of vertically aligning the liquid crystal compound corresponds to the action of reducing the tilt angle of the director, that is, the angle formed between the director and the coated liquid crystal air side surface in the discotic liquid crystal compound. As the compound that decreases the tilt angle of the director of the discotic liquid crystal molecule, a polymer containing a rigid structural unit having an excluded volume effect such as a maleimide group is preferably used.

  Moreover, the compound described in Unexamined-Japanese-Patent No. 2002-20363 and 2002-129162 can be used as an air interface aligning agent. Also, paragraph numbers [0072] to [0075] of Japanese Patent Application No. 2002-212100, paragraph numbers [0037] to [0039] of Japanese Patent Application No. 2002-262239, paragraphs of Japanese Patent Application No. 2003-91752 Nos. [0071] to [0078], paragraph numbers [0052] to [0054], [0065] to [0066], [0092] to [0094] of Japanese Patent Application No. 2003-119959, Japanese Patent Application No. 2003-330303 The matters described in paragraph numbers [0028] to [0030] of the specification and paragraph numbers [0087] to [0090] of Japanese Patent Application No. 2004-003804 can also be appropriately applied to the present invention. Moreover, by mix | blending these compounds, applicability | paintability is improved and generation | occurrence | production of a nonuniformity or a repellency is suppressed.

  The amount of the air interface alignment agent used in the liquid crystal coating liquid is preferably 0.05% by mass to 5% by mass. Moreover, when using a fluorine-type air interface aligning agent, it is preferable that it is 1 mass% or less.

<Other materials in retardation layer>
Along with the liquid crystal compound, a plasticizer, a surfactant, a polymerizable monomer, and the like can be used in combination to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal compound, and the like. These materials are preferably compatible with the liquid crystal compound and do not inhibit the alignment.

  Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Preferably, it is a polyfunctional radically polymerizable monomer and is preferably copolymerizable with the above-described polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A No. 2002-296423. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline molecules.

  Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specifically, for example, compounds described in JP-A-2001-330725, paragraphs [0028] to [0056], and paragraphs [0069] to [0126] in Japanese Patent Application No. 2003-295212. And the compounds described.

  The polymer used together with the liquid crystal compound is preferably capable of thickening the coating solution. A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include those described in paragraph [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and in the range of 0.1 to 8% by mass with respect to the liquid crystal molecules so as not to inhibit the alignment of the liquid crystal compound. It is more preferable. The discotic nematic liquid crystal phase-solid phase transition temperature of the liquid crystal compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

[Support]
In the present invention, a retardation layer formed from a liquid crystal compound may be formed on a support. The support is preferably transparent, and specifically, the light transmittance is preferably 80% or more. The support preferably has a small wavelength dispersion. Specifically, the Re400 / Re700 ratio is preferably less than 1.2. Among these, a polymer film is preferable. The transparent support can also serve as the first retardation region, the second retardation region, or the polarizing plate protective film. The transparent support and the whole retardation layer may constitute the first retardation region or the second retardation region. In addition, for example, when the second retardation region is a retardation film made of liquid crystalline molecules, the support contains cellulose propionate or cellulose propionate having optical characteristics required for the first retardation region. As a film, or when the first retardation region is a retardation film made of liquid crystalline molecules, the support contains cellulose propionate or cellulose propionate having optical properties required for the second retardation region. As the film, the first phase difference region and the first phase difference region can be integrally manufactured.

  The optical anisotropy of the support is preferably small, and the in-plane retardation (Re) is preferably 20 nm or less, more preferably 10 nm or less, and most preferably 5 nm or less. Further, when serving also as the second retardation region, the retardation Rth in the thickness direction is 50 nm to 200 nm, more preferably in the range of 60 nm to 150 nm, and most preferably in the range of 70 nm to 130 nm. Moreover, when it serves also as a polarizing plate protective film, the retardation Rth in the thickness direction is 25 nm or less, more preferably 20 nm or less, and most preferably 10 nm or less.

  Examples of the polymer film as the support include cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate and polymethacrylate films. A cellulose ester film is preferred, an acetyl cellulose film is more preferred, and a triacetyl cellulose film is most preferred. The polymer film used as the support is preferably formed by a solvent cast method. The thickness of the transparent support is preferably 20 to 500 μm, and more preferably 40 to 200 μm. In order to improve adhesion between the transparent support and the layer (adhesive layer, vertical alignment film or retardation layer) provided thereon, surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet light (UV) ) Treatment, flame treatment). An adhesive layer (undercoat layer) may be provided on the transparent support. Moreover, the average particle diameter is 10 to 100 nm in order to give the transparent support or the long transparent support a slip property in the transport process or to prevent the back surface and the surface from sticking after winding. It is preferable to use what formed the polymer layer which mixed the inorganic particle of about 5%-40% by solid content weight ratio on the one side of the support body by application | coating or co-casting with a support body.

[Protective film for polarizing film]
As the protective film for the polarizing plate, a film having no absorption in the visible light region, a light transmittance of 80% or more, and a retardation based on birefringence is preferable. Specifically, the in-plane Re is preferably 0 to 20 nm, more preferably 0 to 10 nm, and most preferably 0 to 5 nm. Furthermore, the retardation Rth in the thickness direction is preferably 0 to 40 nm, more preferably 0 to 20 nm, and most preferably 0 to 10 nm. Any film having this characteristic can be preferably used, but from the viewpoint of durability of the polarizing film, cellulose acylate or norbornene-based film is more preferable. Examples of the method for reducing the Rth of the cellulose acylate film include methods described in JP-A Nos. 11-246704, 2001-247717, and Japanese Patent Application No. 2003-379975. Rth can also be reduced by reducing the thickness of the cellulose acylate film. The thickness of the cellulose sylate film as the protective film for the second polarizing plate is preferably 10 to 100 μm, more preferably 10 to 60 μm, and still more preferably 20 to 45 μm.

  As described above, the first retardation region or the second phase region may also serve as a protective film for a polarizing plate (a protective film disposed closer to the liquid crystal cell). The protective film is preferably cellulose acetate propionate or cellulose propionate.

[Optical compensation film integrated with polarizing plate]
The present invention relates to a polarizing plate integrated compensation film produced by integrating a polarizing film and first and / or second retardation regions having an optical compensation function. By using the polarizing plate integrated optical compensation film of the present invention, the viewing angle characteristics of the liquid crystal display device can be improved with a simpler configuration. In addition, the polarizing plate integrated optical compensation film of the present invention can be produced in a long shape by roll-to-roll, and then cut into a desired size, so that it can be produced by a simple process, It also contributes to improving the productivity of liquid crystal display devices.

  One embodiment of the polarizing plate-integrated optical compensation film of the present invention comprises a long polarizing film having an absorption axis parallel to the longitudinal direction and cellulose acetate propionate or cellulose propionate, and is a letter in the thickness direction. A long polarizing plate-integrated optical compensation film having a long retardation film having a retardation Rth of −30 nm to −250 nm and an in-plane retardation Re of 50 nm or less. The polarizing plate integrated optical compensation film of the present embodiment has a retardation layer that satisfies not only the function as a polarizing film but also the optical characteristics as the first retardation region. The polarizing plate-integrated optical compensation film of the present embodiment is produced, for example, in a long shape by roll-to-roll, and after being cut into a predetermined size, a liquid crystal display device (for example, having the configuration shown in FIGS. 2 and 3). Used in liquid crystal display devices).

  In another aspect of the polarizing plate-integrated optical compensation film of the present invention, at least the polarizing film, the refractive index anisotropy is positive, and the optical axis is substantially perpendicular to the layer surface. A first retardation region comprising a film containing pionate or cellulose propionate, a composition having a negative refractive index anisotropy and an optical axis substantially parallel to the layer surface and containing discotic liquid crystal molecules A polarizing plate-integrated optical compensation film including a second retardation region made of a retardation film formed from a product, wherein the retardation Rth in the thickness direction of the first retardation region is −30 nm to −250 nm, The in-plane retardation Re of the second retardation region is a polarizing plate-integrated optical compensation film having a thickness of 50 nm to 400 nm. The polarizing plate integrated optical compensation film of this embodiment has not only a function as a polarizing film but also a retardation layer that satisfies optical characteristics as the first retardation region and the second retardation region. The polarizing plate-integrated optical compensation film of the present embodiment is produced, for example, in a long shape by roll-to-roll, and after being cut into a predetermined size, a liquid crystal display device (for example, a liquid crystal display device having the configuration of FIG. ).

  Note that the polarizing plate-integrated optical compensation film of the present invention may have a polarizing film protective film on the surface of the polarizing film opposite to the side where the retardation layer is formed. Further, a protective film for the polarizing film polarizing film may be provided between the polarizing film and the retardation layer. In such a case, the retardation based on the birefringence of the protective film is small. The in-plane retardation Re and the thickness direction retardation Rth are both preferably closer to 0 nm.

The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios of substances, operations, 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 is not limited to the following specific examples.
<Production of IPS mode liquid crystal cell>
As shown in FIG. 1, electrodes (2 and 3 in FIG. 1) are arranged on one glass substrate so that the distance between adjacent electrodes is 20 μm, and a polyimide film is used as an alignment film on it. A rubbing process was performed. The rubbing process was performed in the direction 4 shown in FIG. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. The two glass substrates are stacked and bonded so that the alignment films face each other, the distance between the substrates (gap; d) is 3.9 μm, and the rubbing directions of the two glass substrates are parallel. A nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric anisotropy (Δε) of 4.5 was enclosed. The value of d · Δn of the liquid crystal layer was 300 nm.

<Fabrication of ferroelectric liquid crystal cell>
A polyimide film on an ITO electrode glass substrate was provided as an alignment film, and a rubbing treatment was performed. Two substrates are manufactured, the alignment films are made to face each other, the distance between the substrates (gap; d) is set to 1.9 μm, and the rubbing directions of the two glass substrates are parallel to each other and bonded together. Next, a ferroelectric liquid crystal composition having a refractive index anisotropy (Δn) of 0.15 and a spontaneous polarization (Ps) of 12 nCcm ⁻² was sealed. The value of d · Δn of the liquid crystal layer was 280 nm.

<Production of cellulose acylate film>
Cellulose acylate films A to D were prepared according to the following.
(Preparation of cellulose acylate)
Cellulose acylates having different acyl group types and substitution degrees as shown in Table 1 were prepared. That is, a mixture of sulfuric acid as a catalyst (7.8 parts by mass with respect to 100 parts by mass of cellulose) and carboxylic anhydride is added to cellulose derived from pulp after cooling to -20 ° C, and acylation is performed at 40 ° C. went. At this time, the kind of acyl group and its substitution ratio were adjusted by adjusting the kind and amount of carboxylic anhydride. After acylation, aging was performed at 40 ° C. to adjust the total substitution degree.

(Preparation of cellulose acylate solution)
1) Cellulose acylate The prepared cellulose acylate was heated to 120 ° C. and dried to adjust the water content to 0.5% by mass or less, and then 30 parts by mass was mixed with a solvent.
2) Solvent Dichloromethane / methanol / butanol (81/15/4 parts by mass) was used as a solvent. The water content of these solvents was 0.2% by mass or less.
3) Additive In preparing all the solutions, 0.9 parts by mass of trimethylolpropane triacetate was added. In addition, 0.25 part by mass of silicon dioxide fine particles (particle diameter 20 nm, Mohs hardness about 7) was added in preparing all solutions.
4) Swelling and dissolution The cellulose acylate was gradually added to the 400 liter stainless steel dissolution tank having stirring blades and circulating cooling water around the periphery while stirring and dispersing the solvent and additives. . After completion of the addition, the mixture was stirred at room temperature for 2 hours, swollen for 3 hours, and then stirred again to obtain a cellulose acylate solution.
For stirring, a dissolver type eccentric stirring shaft that stirs at a peripheral speed of 15 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² ) and an anchor blade on the central axis and a peripheral speed of 1 m / sec. A stirring shaft that stirs at a sec (shear stress of 1 × 10 ⁴ kgf / m / sec ² ) was used. Swelling was carried out with the high speed stirring shaft stopped and the peripheral speed of the stirring shaft having anchor blades set at 0.5 m / sec.
5) Filtration The cellulose acylate solution obtained above was filtered with a filter paper (# 63, manufactured by Toyo Roshi Kaisha, Ltd.) having an absolute filtration accuracy of 0.01 mm, and further a filter paper (FH025, Poll) having an absolute filtration accuracy of 2.5 μm. To obtain a cellulose acylate solution.

(Preparation of cellulose acylate film)
The cellulose acylate solution was heated to 30 ° C., and cast on a mirror surface stainless steel support having a band length of 60 m set at 15 ° C. through a casting Giesser (described in JP-A-11-314233). The casting speed was 15 m / min and the coating width was 200 cm. The space temperature of the entire casting part was set to 15 ° C. And the cellulose acylate film which had been cast and rotated 50 cm before the casting part was peeled off from the band, and 45 ° C. dry air was blown. Next, it was dried at 110 ° C. for 5 minutes and further at 140 ° C. for 10 minutes to obtain a cellulose acylate film.

Further, a cellulose acylate film E was produced according to the following.
(Pelletization of cellulose acylate)
The cellulose acylate was dried at 120 ° C. for 3 hours to have a water content of 0.1% by mass, and 3% by mass of a plasticizer (dioctyl adipate) was added to the cellulose acylate. Further, silicon dioxide particles (Aerosil) R972V) 0.05% by weight was added. This mixture was put into a hopper of a twin-screw kneading extruder and kneaded. The biaxial kneading extruder was provided with a vacuum vent and evacuated (set to 0.3 atm).
After melting in this way, it was extruded into a strand having a diameter of 3 mm in a water bath, immersed for 1 minute (strand solidification), passed through 10 ° C. water for 30 seconds, lowered in temperature, and then cut into a length of 5 mm. The pellets thus prepared were dried at 100 ° C. for 10 minutes and then packaged.
Tg of the obtained pellet was measured by the following method.
(Tg measurement) 20 mg of a sample is put into a DSC measurement pan. The temperature is raised from 30 ° C. to 230 ° C. at 10 ° C./min in a nitrogen stream (1st-run), and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature is raised again to 30 ° C. to 230 ° C. (2nd-run). Tg obtained at 2nd-run (temperature at which the baseline starts to deviate from the low temperature side) was defined as Tg of the pellet.

(Preparation of cellulose acylate film)
The cellulose acylate pellets prepared by the above method were dried with a vacuum dryer at 110 ° C. for 3 hours. This was put into a hopper adjusted to Tg-10 ° C, melted at 200 ° C for 5 minutes, filtered through a filter (FH400, manufactured by Pall) with an absolute filtration accuracy of 0.04 mm, and further absolute filtration accuracy A cellulose acylate melt was obtained by filtration through a 0.01 μm filter (FH100, manufactured by Pall). The T / D ratio (lip gap / film thickness) is 1.0, and the casting drum (CD) and die gap (CD-die gap is divided by the film width and expressed as a percentage). A film was formed at 10%. At this time, a film having a desired thickness (D) was obtained by setting the casting drum speed to T / D times the extrusion speed. At this time, the temperature at both ends of the die was raised by 10 ° C. from the center.
The casting drum was set to Tg-10 ° C., and solidified thereon to form a film. The solidified melt was peeled off, and MD stretched and TD stretched to obtain desired optical characteristics at Tg + 15 ° C. to obtain a cellulose acylate film.

[Example 1]
<Preparation of Second Retardation Region 1 and Polarizing Plate Integrated Optical Compensation Films 1 and 2>
After saponification of the surface of a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.), an alignment film coating solution having the following composition was applied onto this film with a wire bar coater at 20 ml / m ² . The film was formed by drying with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds. Next, the formed film was rubbed in a direction parallel to the slow axis direction of the film to form an alignment film.
Composition of Alignment Film Coating Solution Modified Polyvinyl Alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 part by weight Tetramethylammonium fluoride 0.3 part by weight

  Next, 1.8 g of the following discotic liquid crystalline compound, 0.2 g of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), a photopolymerization initiator (IRGA) Cure 907, Ciba Geigy Co., Ltd.) 0.06 g, Sensitizer (Kaya Cure DETX, Nippon Kayaku Co., Ltd.) 0.02 g, Air Interface Side Vertical Alignment Agent (Exemplary Compound P-6) 0.01 g 3.9 g The solution dissolved in methyl ethyl ketone was applied with a # 6 wire bar. This was attached to a metal frame and heated in a thermostatic bath at 125 ° C. for 3 minutes to align the discotic liquid crystal compound. Next, using a 120 W / cm high-pressure mercury lamp at 90 ° C., UV irradiation was performed for 30 seconds to crosslink the discotic liquid crystal compound, and then the mixture was allowed to cool to room temperature to form a discotic liquid crystal retardation layer. A film made of a support made of a cellulose acetate film and a discotic liquid crystal retardation layer is used as the protective film 1.

  Using an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments), measure the light incident angle dependency of Re of the protective film 2 and subtract the contribution of the cellulose acetate film measured in advance. The optical characteristics of only the discotic liquid crystal retardation layer were calculated by the following equation. Re was 215 nm, Rth was −117 nm, the average tilt angle of the liquid crystal was 89.9 °, and the discotic liquid crystal was perpendicular to the film plane. It was confirmed that it was oriented. The slow axis direction was parallel to the rubbing direction of the alignment film. The discotic liquid crystal retardation layer produced as described above was a retardation layer having negative refractive index anisotropy and an optical axis substantially parallel to the layer surface. This discotic liquid crystal retardation layer was designated as a second retardation region 1.

  A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. Using a polyvinyl alcohol-based adhesive, the produced protective film 1 was saponified so that the cellulose acetate film was on the polarizing film side and attached to one side of the polarizing film. The transmission axis of the polarizing film and the slow axis of the protective film 1 (the slow axis of the second retardation region 1 also coincides with this) were arranged so as to be orthogonal. Commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is saponified and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Was made.

  Furthermore, the above-mentioned film A (first retardation region 1) in which a polarizing film produced by adsorbing iodine to a stretched polyvinyl alcohol film was saponified and a commercially available cellulose acetate film (Fujitac TD80UF, Fuji Photo Film ( (Manufactured by Co., Ltd.) was continuously bonded using an adhesive to produce a 500 m long polarizing plate-integrated optical compensation film 2 with a retardation film.

Next, various liquid crystal display devices were manufactured using the polarizing plate-integrated optical compensation film prepared above, and light leakage was evaluated. In addition, the polarizing plate integrated optical compensation film produced in a long shape was cut into a predetermined size and then incorporated into a liquid crystal display device.
<Production of liquid crystal display device 1>
Using an adhesive, the polarizing plate-integrated optical compensation film 1 is placed on one of the IPS mode liquid crystal cells produced above so that the slow axis of the protective film 1 is orthogonal to the rubbing direction of the liquid crystal cell (that is, Adhering so that the slow axis of the second retardation region 1 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display) and the discotic liquid crystal retardation layer surface side is the liquid crystal cell side It was. Subsequently, the produced polarizing plate-integrated optical compensation film 2 is pasted on the other side of the IPS mode liquid crystal cell 1 so that the film A side is the liquid crystal cell side and in a crossed Nicol arrangement. 1 was produced.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.04%.

[Example 2]
<Preparation of Second Compensation Region 2 and Polarizing Plate Integrated Optical Compensation Film 3>
Example except that the surface of the film B (first retardation region 2) was saponified, an alignment film was formed on the film in the same manner as in Example 1, and the bar number was changed to # 5.4. In the same manner as in Example 1, a vertically aligned discotic liquid crystal layer (second retardation region 2) was formed, and a protective film 2 was formed. The optical characteristics of only the discotic liquid crystal retardation layer were calculated in the same manner as in Example 1. As a result, Re was 195 nm, Rth was −97 nm, the average tilt angle of the liquid crystal was 89.9 °, and the discotic liquid crystal was a film surface. It was confirmed that the film was oriented perpendicularly.
A polarizing film is manufactured by adsorbing iodine to a stretched polyvinyl alcohol film, and the protective film 2 is pasted on one side of the polarizing film using a polyvinyl alcohol adhesive so that the film B side is the polarizing film side. It was. The transmission axis of the polarizing film and the slow axis of the protective film 2 (the slow axis of the second phase difference region 2 also coincides with this) are arranged in parallel. Subsequently, a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Film 3 was produced.

<Production of liquid crystal display device 2>
Using an adhesive, the polarizing plate-integrated optical compensation film 3 is placed on one of the IPS mode liquid crystal cells produced above so that the slow axis of the protective film 2 is orthogonal to the rubbing direction of the liquid crystal cell (that is, Adhering so that the slow axis of the second retardation region 2 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display) and the discotic liquid crystal retardation layer side is the liquid crystal cell side It was. Subsequently, a commercially available polarizing plate (HLC2-5618, manufactured by Sanritz Co., Ltd.) was attached to the other side of the IPS mode liquid crystal cell 1 in a crossed Nicol arrangement to produce the liquid crystal display device 1.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.03%.

[Example 3]
<Preparation of Second Retardation Region 3 and Polarizer-Integrated Optical Compensation Film 4>
After saponifying the surface of film D, an alignment film was formed on this film in the same manner as in Example 1, and the vertical alignment was performed in the same manner as in Example 1 except that the number of bars was changed to # 4.8. A discotic liquid crystal layer (second retardation region 3) was formed, and the protective film 3 was formed. The optical characteristics of only the discotic liquid crystal retardation layer were calculated in the same manner as in Example 1. As a result, Re was 172 nm, Rth was −86 nm, the average tilt angle of the liquid crystal was 89.9 °, and the discotic liquid crystal was a film surface. It was confirmed that the film was oriented perpendicularly.

  A polarizing film is manufactured by adsorbing iodine to a stretched polyvinyl alcohol film, and the protective film 3 is pasted on one side of the polarizing film using a polyvinyl alcohol adhesive so that the film D side is the polarizing film side. It was. The transmission axis of the polarizing film and the slow axis of the protective film 3 (the slow axis of the second phase difference region 3 also coincides with this) are arranged in parallel. Subsequently, a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) is subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol adhesive, and polarizing plate integrated optical compensation Film 4 was made.

<Production of liquid crystal display device 3>
Using an adhesive, the polarizing plate-integrated optical compensation film 4 is applied to one of the IPS mode liquid crystal cells produced above so that the slow axis of the protective film 3 is orthogonal to the rubbing direction of the liquid crystal cell (that is, Adhering so that the slow axis of the second retardation region 3 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display) and the discotic liquid crystal retardation layer surface side is the liquid crystal cell side It was. Subsequently, the polarizing plate integrated optical compensation film 2 produced in Example 1 was attached to the other side of the IPS mode liquid crystal cell 1 so that the film A side was the liquid crystal cell side and in a crossed Nicol arrangement. A liquid crystal display device 3 was produced.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.02%.

[Example 4]
<Preparation of Second Retardation Region 4 and Polarizing Plate Integrated Optical Compensation Film 5>
170 g of a styrene polymer obtained by graft polymerization of 90 parts by weight of the monomer mixture (B) below was dissolved in 830 g of methylene dichloride in 10 parts by weight of the copolymer (A) below.
(A) Styrene / butadiene copolymer (mass ratio: 20/80)
(B) Styrene / acrylonitrile / α-methylstyrene (mass ratio: 60/20/20)
This solution is cast on a glass plate so that the film thickness after drying is 100 μm, left at room temperature for 5 minutes, and then dried for 20 minutes with warm air at 45 ° C. The obtained film (film) is made of glass. Peeled from the board. This film was attached to a rectangular frame and dried at 70 ° C. for 1 hour. After further drying at 110 ° C. for 15 hours, uniaxial stretching was performed at a magnification of 1.9 times with a tensile tester (Strograph R2, manufactured by Toyo Seiki Co., Ltd.) at 115 ° C. As described above, a uniaxially stretched film (second retardation region 4) of the styrene polymer was produced. The retardation of the obtained film was measured. Re was 174 nm and Rth was -86 nm. This film had negative refractive index anisotropy and the optical axis was in a direction parallel to the film surface (that is, in the film surface). This film was designated as a second phase difference region 4.

  A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. Using polyvinyl alcohol adhesive, saponification treatment is applied to the above-mentioned film D and commercially available cellulose acetate film (Fujitac TD80UF), and a polarizing plate is formed on both sides of the polarizing film using polyvinyl alcohol adhesive. did. Further, using a commercially available adhesive, the second retardation region 4 is arranged on the surface of the film D so that the transmission axis of the polarizing film and the slow axis of the second retardation region 4 are orthogonal to each other. A body-shaped optical compensation film 5 was formed.

<Production of liquid crystal display device 4>
This is applied to one of the IPS mode liquid crystal cells 1 produced as described above using an adhesive, and the polarizing plate integrated optical compensation film 5, and the slow axis of the second retardation region 4 is orthogonal to the rubbing direction of the liquid crystal cell. (That is, the slow axis of the second retardation region 4 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display), and the surface side of the second retardation region 4 is liquid crystal Affixed to the cell side. Subsequently, the polarizing plate integrated optical compensation film 2 produced in Example 1 was attached to the other side of the IPS mode liquid crystal cell 1 so that the film A side was the liquid crystal cell side and in a crossed Nicol arrangement. A liquid crystal display device 4 was produced.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.02%.

[Example 5]
<Preparation of Second Retardation Region 5 and Polarizing Plate Integrated Optical Compensation Film 6>
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. Using a polyvinyl alcohol-based adhesive, the above-mentioned film E (second retardation region 5) and a commercially available cellulose acetate film (Fujitac TD80UF) are saponified, and using a polyvinyl alcohol-based adhesive, A polarizing plate-integrated optical compensation film 6 was formed by continuously pasting on both sides. In this way, the polarizing plate integrated optical compensation film 6 was formed so that the slow axis of the second retardation region 4 and the transmission axis of the polarizing film were orthogonal to each other.

<Production of liquid crystal display device 5>
This is applied to one of the IPS mode liquid crystal cells 1 produced as described above using an adhesive, and the polarizing plate integrated optical compensation film 6, and the slow axis of the second retardation region 5 is orthogonal to the rubbing direction of the liquid crystal cell. (That is, the slow axis of the second retardation region 5 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display), and the second retardation region 5 surface side is liquid crystal. Affixed to the cell side. Subsequently, the polarizing plate integrated optical compensation film 2 produced in Example 1 was attached to the other side of the IPS mode liquid crystal cell 1 so that the film A side was the liquid crystal cell side and in a crossed Nicol arrangement. A liquid crystal display device 5 was produced.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.02%.

[Example 6]
<Preparation of polarizing plate integrated optical compensation films 7 and 8>
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film. Using a polyvinyl alcohol-based adhesive, the above-mentioned film C (first retardation region 3) and a commercially available cellulose acetate film (Fujitac TD80UF) are subjected to saponification treatment, and using a polyvinyl alcohol-based adhesive, Affixed continuously to both sides. Further, a film E (second retardation region 6) is attached to the polarizing plate film C side with an adhesive so that the slow axis is parallel to the transmission axis of the polarizing film, and the integrated optical compensation film 7 is attached. Was made.

  A polarizing film is produced by adsorbing iodine to a stretched polyvinyl alcohol film, and a saponification treatment is performed on both sides of the polarizing film using a polyvinyl alcohol adhesive, and a commercially available cellulose acetate film (Fujitac TD80UF). , Manufactured by Fuji Photo Film Co., Ltd.) was continuously pasted to produce a long polarizing plate integrated optical compensation film 8.

<Production of liquid crystal display device 6>
This is applied to one of the IPS mode liquid crystal cells produced above using an adhesive, and the polarizing plate integrated optical compensation film 7 is rubbed with the slow axis of the film E (second retardation region 6) of the liquid crystal cell. Film E (second position) so that it is perpendicular to the direction (that is, the slow axis of the second retardation region 6 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display). The phase difference region 6) was bonded so that the surface side was the liquid crystal cell side. Subsequently, a polarizing plate-integrated optical compensation film 8 is attached to the other side of the IPS mode liquid crystal cell 1 so that the film D side is the liquid crystal cell side and in a crossed Nicol arrangement, thereby producing a liquid crystal display device 6. did.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.02%.

[Example 7]
<Production of liquid crystal display device 7>
This is applied to one of the ferroelectric liquid crystal cells prepared above using an adhesive, and the polarizing plate integrated optical compensation film 7 is used. The slow axis of the film E (second retardation region 6) is the liquid crystal cell. To be perpendicular to the molecular axis of the liquid crystal when a DC voltage is applied (that is, the slow axis of the second retardation region 6 is perpendicular to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display). The film E (second retardation region 6) was attached so that the surface side was the liquid crystal cell side. Subsequently, a polarizing plate-integrated optical compensation film 8 is attached to the other side of the ferroelectric liquid crystal cell so that the film D side is on the liquid crystal cell side and in a crossed Nicol arrangement, thereby producing a liquid crystal display device 7. did.
The leakage light of the liquid crystal display device thus manufactured was measured. The leakage light when observed from the left oblique direction of 60 ° was 0.02%.

[Comparative Example 1]
<Production of liquid crystal display device 8>
A commercially available polarizing plate (HLC2-5618, manufactured by Sanritz Co., Ltd.) in which the absorption axis of one polarizing film and the rubbing direction of the liquid crystal cell are orthogonal to each other on both surfaces of the produced IPS mode liquid crystal cell The liquid crystal display device 8 was produced by pasting in the arrangement. Furthermore, the leakage light in the left oblique direction at 60 ° was measured and found to be 0.55%.

[Comparative Example 2]
<Production of liquid crystal display device 9>
Using an adhesive, the polarizing plate-integrated optical compensation film 3 is placed on one of the IPS mode liquid crystal cells produced above so that the slow axis of the protective film 2 is parallel to the rubbing direction of the liquid crystal cell (that is, Adhering so that the slow axis of the second retardation region 2 is parallel to the slow axis of the liquid crystal molecules of the liquid crystal cell during black display) and the discotic liquid crystal retardation layer side is the liquid crystal cell side It was. Subsequently, a commercially available polarizing plate (HLC2-5618, manufactured by Sanritz Co., Ltd.) was attached to the other side of the IPS mode liquid crystal cell 1 in a crossed Nicol arrangement to produce the liquid crystal display device 1.
The leakage light of the liquid crystal display device thus manufactured was measured. Light leakage when observed from the left oblique direction of 60 ° was 1.5%.

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

Explanation of symbols

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

Claims (14)

A long polarizing film having an absorption axis parallel to the longitudinal direction;
Cellulose acetate propionate or cellulose propionate, Rth = {(nx + ny) / 2 using in-plane refractive index nx and ny (nx ≧ ny), thickness direction refractive index nz, and thickness d A long retardation film in which Rth defined by −nz} × d is −30 nm to −250 nm and Re defined by Re = (nx−ny) × d is 50 nm or less;
A long polarizing plate-integrated optical compensation film. At least a polarizing film, a first retardation region having a positive refractive index anisotropy and an optical axis substantially perpendicular to the layer surface, and a negative refractive index anisotropy and an optical axis relative to the layer surface A polarizing plate-integrated optical compensation film having a second retardation region that is substantially parallel;
The first phase difference defined by Rth = {(nx + ny) / 2−nz} × d using the in-plane refractive indexes nx and ny (nx ≧ ny), the refractive index nz in the thickness direction, and the thickness d. The retardation Rth in the thickness direction of the region is −30 nm to −250 nm, the retardation Re of the second retardation region defined by Re = (nx−ny) × d is 50 nm to 400 nm, and the first A polarizing plate integrated optical compensation film, wherein at least one of the retardation region and the second retardation region is a film containing cellulose acetate propionate or cellulose propionate. The polarizing film, the first retardation region, and the second retardation region are arranged in this order, and the slow axis of the second retardation region is substantially the transmission axis of the polarizing film. 3. The polarizing plate integrated optical compensation film according to claim 2, which is parallel. The cellulose acetate propionate or the film containing cellulose propionate is a cellulose acylate film in which the acyl substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III). The polarizing plate-integrated optical compensation film according to any one of the above.
(I) 2.82 ≦ SA + SP ≦ 3
(II) 0 ≦ SA ≦ 1.7
(III) 1.3 ≦ SP ≦ 2.9
(In the formula, SA and SP represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SP is the substitution degree of the propionyl group.) At least a first polarizing film, a first retardation region having a positive refractive index anisotropy and an optical axis substantially perpendicular to the layer surface, and a negative refractive index anisotropy and an optical axis on the layer surface. A liquid crystal cell having a liquid crystal layer sandwiched between a pair of substrates and a second polarizing film, wherein the liquid crystal molecules of the liquid crystal layer are surfaces of the pair of substrates during black display. A liquid crystal display device oriented parallel to
The first phase difference defined by Rth = {(nx + ny) / 2−nz} × d using the in-plane refractive indexes nx and ny (nx ≧ ny), the refractive index nz in the thickness direction, and the thickness d. The retardation Rth in the thickness direction of the region is −30 nm to −250 nm, the retardation Re of the second retardation region defined by Re = (nx−ny) × d is 50 nm to 400 nm,
A liquid crystal layer in which at least one of the first retardation region and the second retardation region is cellulose acetate propionate or a film containing cellulose propionate, and the slow axis of the second retardation region is black. Liquid crystal display device that is orthogonal to the slow axis direction. The first polarizing film, the first retardation region, the second retardation region, and the liquid crystal cell are arranged in this order, and the slow axis of the second retardation region is the transmission axis of the polarizing film. The liquid crystal display device according to claim 5, wherein the liquid crystal display device is substantially parallel to the liquid crystal display device. The first retardation region, the liquid crystal cell, the second retardation region, and the first polarizing film are arranged in this order, and the slow axis of the second retardation region is the transmission axis of the first polarizing film. The liquid crystal display device according to claim 5, wherein the liquid crystal display device is substantially orthogonal to. A pair of protective films disposed between at least one of the first polarizing film and the second polarizing film, and a thickness direction retardation Rth of the protective film on the side close to the liquid crystal layer of the pair of protective films. The liquid crystal display device according to claim 5, wherein the liquid crystal display device is 40 nm to −40 nm. A pair of protective films disposed between at least one of the first polarizing film and the second polarizing film, and a thickness direction retardation Rth of the protective film on the side close to the liquid crystal layer of the pair of protective films. The liquid crystal display device according to claim 5, which is 20 nm to −20 nm. A pair of protective films disposed between at least one of the first polarizing film and the second polarizing film, and a thickness of the protective film on the side close to the liquid crystal layer of the pair of protective films is 60 μm or less. Item 10. The liquid crystal display device according to any one of Items 5 to 9. A pair of protective films disposed between the first polarizing film and / or the second polarizing film, wherein the protective film on the side close to the liquid crystal layer is a cellulose acylate film or a norbornene-based film The liquid crystal display device according to any one of claims 5 to 10. The liquid crystal display device according to claim 5, wherein the first retardation region and / or the second retardation region is adjacent to the first polarizing film and / or the second polarizing film. . The said 1st phase difference area | region or the said 2nd phase difference area | region is arrange | positioned in the position nearer to the board | substrate on the opposite side to the visual recognition side among a pair of board | substrates of a liquid crystal cell. Liquid crystal display device. The cellulose acetate propionate or a film containing cellulose propionate is a cellulose acylate film in which the acyl substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III): The liquid crystal display device according to any one of the above.
(I) 2.82 ≦ SA + SP ≦ 3
(II) 0 ≦ SA ≦ 1.7
(III) 1.3 ≦ SP ≦ 2.9
(In the formula, SA and SP represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SP is the substitution degree of the propionyl group.)

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