JP2007171815A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device that is superior in moving picture performance in addition to wide viewing angle display, in particular, superior in both the moving picture display and the viewing angle display characteristics, without using additional members, in low-cost TN mode. <P>SOLUTION: The liquid crystal display device comprises a liquid crystal cell, two sheets of polarizing plates arranged at the outside thereof, and an optical compensation sheet disposed between the liquid crystal cell and the polarizing plate. The liquid crystal cell has a prescribed characteristic, and has a specified relation between a retardation value (Rth) in the thickness direction of the optical compensation sheet and the product Δnd of the birefringence Δn of a liquid crystal material inside the liquid crystal cell and a liquid crystal cell gap d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device comprising a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and an optical compensation sheet disposed between the liquid crystal cell and the polarizing plate.

  The liquid crystal display device includes a liquid crystal cell, a polarizing element, and an optical compensation sheet (retardation plate). Liquid crystal cells are classified according to the alignment state and driving method of the liquid crystal, and are TN (Twisted Nematic), IPS (In-Plane Switching), VA (Vertical Compensatory Bend), OCB (Optically Compensated Bend), ECB (Electrically Bend), ECB (Electrically Bend). There are various display modes such as (Super Twisted Nematic), FLC (Ferroelectric Liquid Crystal), HAN (Hybrid Aligned Nematic), and GH (Guest-Host).

  Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and to widen the viewing angle. As an optical compensation sheet, a stretched birefringent polymer film has been conventionally used, but in recent years, instead of an optical compensation sheet made of a stretched birefringent film, it is formed from a low molecular or high-molecular liquid crystalline compound on a transparent support. It has been proposed to use an optical compensation sheet having an optically anisotropic layer. Since liquid crystal compounds have various alignment forms, optical compensation that uses liquid crystal compounds and corresponds to the alignment state of the liquid crystal molecules in the cell cannot be obtained with conventional stretched birefringent polymer films. It became possible to realize the nature. As such an optical compensation sheet, there is a technique in which a liquid crystal compound is hybrid-aligned to form a film, and a discotic liquid crystal compound (also referred to as a discotic liquid crystal compound) is used as the liquid crystal compound (Patent Literature). 1), and there is an example using a rod-like liquid crystalline compound (see Patent Document 2). In particular, for TN mode and OCB mode liquid crystal displays, an optical compensation sheet in which discotic liquid crystal is hybrid-aligned is very effective. By controlling the orientation of the discotic liquid crystal, desired optical characteristics are exhibited. ing.

In recent years, along with the rapid progress of flat panel displays, large-sized, wide viewing angle, high-brightness panels are being mass-produced in liquid crystal display devices. In accordance with this, the display content is changing from a relatively no movement such as a conventional PC application or car navigation to a content mainly composed of a moving picture represented by a TV. The moving image characteristics of the liquid crystal display was originally a hold display in addition to a slow response speed and was inferior to a CRT or plasma display, but improved the application of a fast response mode such as OCB, overdrive drive, flashing backlight, etc. Thus, a liquid crystal display device excellent in moving image display has been proposed.
JP-A-6-214116 JP-A-10-186356

  The TN mode is a display mode that has been used for an active matrix liquid crystal display device since the oldest, can achieve a wide viewing angle by an optical compensation sheet, and is widely used mainly for PC monitors. Further, a response speed of about 15 msec can be achieved without using a special driving method such as overdrive, and a manufacturing method has been established, so that a liquid crystal display device with excellent performance can be provided at low cost. . However, in order to display full-color moving image content as a large-screen TV intended for living use or a multimedia monitor, it is difficult to say that the viewing angle dependency and moving image characteristics are still sufficient. On the other hand, the VA mode and the IPS mode mainly applied to a large screen TV have a viewing angle display characteristic superior to that of the TN mode, but adopt a complicated pixel structure or add a drive circuit for overdrive. This realizes high-quality display and is inherently expensive.

The response speed of the liquid crystal display device is related to the rotational viscosity of the liquid crystal composition in the liquid crystal cell, physical properties such as elastic modulus and dielectric anisotropy, and the thickness of the liquid crystal cell. Control by the physical property value of the liquid crystal composition is generally in a trade-off relationship. For example, when the rotational viscosity is lowered, the dielectric anisotropy is also reduced, and as a result, it is difficult to increase the response speed. In addition, although it is relatively easy to reduce the cell gap, it is necessary to increase Δn of the liquid crystal composition in order to maintain the luminance.
In general, when the Δn of a liquid crystal composition is increased, its wavelength dependency tends to increase, and this deteriorates display characteristics, particularly color change. As described above, when speeding up the liquid crystal cell, the wavelength characteristics of the liquid crystal composition cause deterioration in display performance.

  Further, in the optical compensation sheet in which the discotic liquid crystal is hybrid-aligned, the director tilt angle and the birefringence in the thickness direction in the optical anisotropic layer are studied in detail in order to match the alignment state of the liquid crystal in the display cell. However, in the TN mode where the viewing angle characteristics are originally extremely poor, when aiming for a super wide viewing angle in which the contrast ratio of black-and-white display exceeds 10 in all directions, It was not always possible to obtain satisfactory characteristics.

  An object of the present invention is to provide a liquid crystal display device with excellent moving image performance at a low cost in addition to wide viewing angle display. In particular, an object of the present invention is to provide a liquid crystal display device excellent in both moving image display and viewing angle display characteristics without using an additional member in a low-cost TN mode.

  As a result of intensive studies by the inventors, it is possible to define a liquid crystal cell having predetermined characteristics, and wavelength characteristics of the liquid crystal cell and the optical compensation sheet within a certain range, viewing angle display characteristics, color change, moving picture characteristics We found that it becomes means to satisfy. Further, the inventors have found that defining the angle dependency of Re of the optically anisotropic layer within a certain range is a means for satisfying the contrast viewing angle, and the present invention has been completed.

The present invention solves these problems and provides the following means.
1. A liquid crystal display device comprising a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and at least one optical compensation sheet disposed between the liquid crystal cell and the polarizing plate,
The liquid crystal cell has a Δnd value of 370 to 440 nm, a twist angle of 88 ° to 92 °, twist nematic alignment, and a response time from white display to black display of 12 msec or less.
The optical compensation sheet satisfies the following mathematical formulas (1) and (2).
Formula (1): 0.9 ≦ {Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ } / {Δnd ₍₄₅₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.0.
Formula (2): 1.0 ≦ {Rth ₍₆₁₀₎ / Rth ₍₅₅₀₎ } / {Δnd ₍₆₁₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.10.
[Δnd is the product of the birefringence Δn of the liquid crystal material in the liquid crystal cell and the liquid crystal cell gap d, and Δnd ₍₄₅₀₎ , Δnd _(550), and Δnd ₍₆₁₀₎ are the birefringence at wavelengths of 450 nm, 550 nm, and 610 nm, respectively. Rth ₍₄₅₀₎ , Rth _(550), and Rth ₍₆₁₀₎ represent retardation values (Rth) in the thickness direction of the optical compensation sheet at wavelengths of 450 nm, 550 nm, and 610 nm, respectively. . ]
2. A liquid crystal display device comprising a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and at least one optical compensation sheet disposed between the liquid crystal cell and the polarizing plate,
The liquid crystal cell has a Δnd value of 370 to 440 nm, a twist angle of 88 ° to 92 °, twist nematic alignment, and a response time from white display to black display of 12 msec or less.
The optical compensation sheet has at least one optically anisotropic layer satisfying the following mathematical formulas (3) and (4).
Formula (3): 0.95 ≦ {Rth ¹ ₍₄₅₀₎ / Rth ¹ ₍₅₅₀₎ } / {Δnd ₍₄₅₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.05.
Formula (4): 0.95 ≦ {Rth ¹ ₍₆₁₀₎ / Rth ¹ ₍₅₅₀₎ } / {Δnd ₍₆₁₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.05.
[Δnd is the product of the birefringence Δn of the liquid crystal material in the liquid crystal cell and the liquid crystal cell gap d, and Δnd ₍₄₅₀₎ , Δnd _(550), and Δnd ₍₆₁₀₎ are the birefringence at wavelengths of 450 nm, 550 nm, and 610 nm, respectively. Rth ¹ ₍₄₅₀₎ , Rth ¹ ₍₅₅₀₎ and Rth ¹ ₍₆₁₀₎ are retardation values in the thickness direction of the optically anisotropic layer at wavelengths of 450 nm, 550 nm and 610 nm, respectively. Represents (Rth). ]
3. 3. The liquid crystal display device according to 1 or 2 above, wherein the wavelength dispersion Δn ₍₄₅₀₎ / Δn ₍₅₅₀₎ of liquid crystal molecules in the liquid crystal cell is 1.04 or more.
4). 4. The liquid crystal display device as described in 2 or 3 above, wherein the optically anisotropic layer is formed by fixing the orientation of the liquid crystalline compound.
5. 5. The liquid crystal display device as described in any one of 1 to 4 above, wherein the optical compensation sheet contains a polymer support film having birefringence and an optically anisotropic layer in which the orientation of the liquid crystal compound is fixed. 6). Retardation value of optical anisotropic layer measured from normal direction of optically anisotropic layer: Re is 40 nm or more,
And the retardation value of the optically anisotropic layer measured from the direction inclined by + 40 ° from the normal line of the optically anisotropic layer in a plane perpendicular to the optically anisotropic layer including the orientation direction: Re ⁽⁺⁴⁰⁾ , Re ratio: Re ⁽⁺⁴⁰⁾ / Re is less than 2.0,
Further, the retardation value of the optically anisotropic layer measured from the direction inclined by −40 ° from the normal line of the optically anisotropic layer in the plane perpendicular to the optically anisotropic layer including the orientation direction: Re ⁽⁻⁴⁰⁾ And the ratio of Re: The liquid crystal display device according to any one of the above 2 to 5, wherein Re ⁽⁻⁴⁰⁾ / Re is 0.40 or more.
7). 7. The liquid crystal display device according to any one of 4 to 6 above, wherein the liquid crystal compound used for the optically anisotropic layer is a discotic liquid crystal compound.
8). 8. The liquid crystal display device according to any one of 5 to 7, wherein the polymer support film is a cellulose acylate film.
9. 9. The liquid crystal display device according to any one of the above 1 to 8, wherein the optical compensation sheet is directly bonded to the polarizing film of the polarizing plate, thereby serving as a protective film for the polarizing plate.

  The liquid crystal display device of the present invention has a performance sufficient for moving picture characteristics, a wide viewing angle, and no color change by strictly controlling the TN liquid crystal cell and the optical compensation sheet capable of high-speed response at all wavelengths. High-quality display performance can be obtained.

  Hereinafter, the configuration and characteristics of the liquid crystal display device of the present invention and the optical compensation sheet used therefor will be described.

<Liquid crystal display device>
The liquid crystal display device of the present invention comprises a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and at least one optical compensation sheet disposed between the liquid crystal cell and the polarizing plate.
The liquid crystal cell is twisted nematically aligned with a twist angle of 88 ° to 92 ° (hereinafter, this liquid crystal cell is referred to as a “TN mode liquid crystal cell”).
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents. The alignment state in the liquid crystal cell in the TN mode black display is an alignment state in which the rod-like liquid crystalline molecules rise at the center of the cell and the rod-like liquid crystalline molecules lie in the vicinity of the cell substrate.

  The liquid crystal cell used in the present invention has a response time of 12 msec or less from white display to black display. The response time is preferably 10 msec or less. The general response speed of the TN mode is 15 msec, and the liquid crystal cell of the present invention has a higher response than the general response speed.

In the liquid crystal cell used in the present invention, Δnd is in the range of 370 to 440 nm. In order to make the liquid crystal cell have a high-speed response, reducing the cell gap is an effective means. If it is in said range, a cell gap can be made small and the brightness | luminance of a liquid crystal display device can be maintained. Δnd is preferably in the range of 380 to 420 nm.
In order to make Δnd within the above range, Δn of the liquid crystal composition in the cell is preferably increased, and the wavelength dispersion Δn ₍₄₅₀₎ / Δn ₍₅₅₀₎ of the liquid crystal composition is 1.04 or more. Is more preferable, and the range of 1.05 to 1.10.

The optical compensation sheet used in the present invention must satisfy the following mathematical formulas (1) and (2). Thereby, the wavelength characteristic of a liquid crystal cell and an optical compensation sheet can be brought close, and the color change of a liquid crystal display device can be reduced.
Formula (1): 0.9 ≦ {Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ } / {Δnd ₍₄₅₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.0.
Formula (2): 1.0 ≦ {Rth ₍₆₁₀₎ / Rth ₍₅₅₀₎ } / {Δnd ₍₆₁₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.10.
Where Δnd is the product of the birefringence Δn of the liquid crystal material in the liquid crystal cell and the liquid crystal cell gap d, and Δnd ₍₄₅₀₎ , Δnd ₍₅₅₀₎ and Δnd ₍₆₁₀₎ are the wavelengths 450 nm, 550 nm and Rth ₍₄₅₀₎ , Rth ₍₅₅₀₎ and Rth ₍₆₁₀₎ are values based on the retardation value in the thickness direction of the optical compensation sheet at wavelengths of 450 nm, 550 nm and 610 nm, respectively. Rth).

Or the optical compensation sheet in this invention can improve the color of a liquid crystal display device by having the at least 1 layer of optically anisotropic layer which satisfy | fills following numerical formula (3) and (4). That is, when the optical compensation sheet has a plurality of optically anisotropic layers, at least one of the layers can satisfy the above formulas (3) and (4) to obtain the above-described effect. The display characteristics of the liquid crystal display device are naturally determined by all of its optical elements, that is, a liquid crystal cell, an optical compensation sheet, a polarizing plate, etc., but at least one constituent layer of the optical compensation sheet is expressed by a formula ( If 3) and (4) are satisfied, the target performance can be exhibited.
Formula (3): 0.95 ≦ {Rth ¹ ₍₄₅₀₎ / Rth ¹ ₍₅₅₀₎ } / {Δnd ₍₄₅₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.05.
Formula (4): 0.95 ≦ {Rth ¹ ₍₆₁₀₎ / Rth ¹ ₍₅₅₀₎ } / {Δnd ₍₆₁₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.05.
In the formula, Δnd, Δnd ₍₄₅₀₎ , Δnd ₍₅₅₀₎ and Δnd ₍₆₁₀₎ are as defined in the above formulas (1) and (2), and Rth ¹ ₍₄₅₀₎ , Rth ¹ ₍₅₅₀₎ and Rth ¹ ₍₆₁₀₎ represents the retardation value (Rth) in the thickness direction of the optically anisotropic layer at wavelengths of 450 nm, 550 nm, and 610 nm, respectively.

When Rth _(λ) and Δnd _(λ) are the product of Rth of the optical compensation sheet at the wavelength λ (nm) and birefringence Δn of the liquid crystal material in the liquid crystal cell and the liquid crystal cell gap d, respectively. The wavelength characteristics of the optical compensation sheet can be expressed by the following mathematical formula (9).
Formula (9): F (λ) = {Rth _(λ) / Rth ₍₅₅₀₎ } / {Δnd _(λ) / Δnd ₍₅₅₀₎ }.
The above formulas (1) and (2) are expressed as follows using formula (9).
Formula (1 ′): 0.9 ≦ F (450) ≦ 1.0.
Formula (2 ′): 1.0 ≦ F (610) ≦ 1.1.
Furthermore, the optical compensation sheet preferably satisfies the following mathematical formulas (1′-1) and (2′-1).
Formula (1′-1): 0.92 ≦ F (450) ≦ 0.98.
Formula (2′-1): 1.00 ≦ F (610) ≦ 1.05.

When Rth ¹ _(λ) is Rth of the optically anisotropic layer at the wavelength λ (nm), the wavelength characteristics of the optically anisotropic layer included in the liquid crystal cell and the optical compensation sheet are expressed by the above formula (9). As in the case of, it can be expressed by the following formula (10).
Formula (10): F ¹ (λ) = {Rth ¹ _(λ) / Rth ¹ ₍₅₅₀₎ } / {Δnd _(λ) / Δnd ₍₅₅₀₎ }.
The above formulas (3), (3-1), (4), and (4-1) are expressed as follows using the formula (10).
Formula (3 ′): 0.95 ≦ F ¹ (450) ≦ 1.05.
Formula (4 ′): 0.95 ≦ F ¹ (610) ≦ 1.05.
Furthermore, the optically anisotropic layer included in the optical compensation sheet preferably satisfies the following mathematical formulas (3′-1) and (4′-1).
Formula (3′-1): 1.00 ≦ F ¹ (450) ≦ 1.05.
Formula (4′-1): 0.97 ≦ F ¹ (610) ≦ 1.03.

<Optical compensation sheet>
The optical compensation sheet is provided with an optically anisotropic layer formed of a liquid crystalline compound on an optically transparent support. By using this optical compensation sheet in a liquid crystal display device, the liquid crystal cell is optically compensated without side effects.
Hereinafter, constituent materials necessary for the optical compensation sheet will be described.

[Support]
As the support, it is preferable to use glass or a transparent polymer film. The support preferably has a light transmittance (at a wavelength of 400 to 700 nm) of 80% or more and a haze of 2.0% or less. More preferably, the light transmittance is 86% or more and the haze is 1.0% or less.

  Examples of the polymer constituting the polymer film include cellulose esters (for example, cellulose mono- to triacylate), norbornene-based polymers, and polymethyl methacrylate. Commercially available polymers {for Norbornene-based polymers, “Arton” and “Zeonex” (both trade names)} may be used. The polymer film can be appropriately adjusted as necessary. Polymers having relatively small birefringence as listed above are preferred because retardation can be easily adjusted and uneven stretching is less likely to occur. In order to perform optical compensation of the TN liquid crystal cell, the optical compensation sheet needs to have negative birefringence. Therefore, it is preferable that the birefringence of the polymer film used in the optical compensation sheet of the present invention is also negative. Moreover, even if it is a conventionally known polymer such as polycarbonate or polysulfone that easily develops birefringence, it is possible to develop birefringence by modifying the molecule as described in International Publication No. 00/26705 pamphlet. Can be used for the optical compensation sheet of the present invention. Hereinafter, the polymer film used for the support may be referred to as “polymer support film”.

[Cellulose acylate film]
As the polymer film, a cellulose acylate film is preferable.
Cellulose acylate film used as the raw material cellulose includes cotton linter, kenaf, wood pulp (hardwood pulp, softwood pulp), etc., and any cellulose ester obtained from any raw material cellulose can be used, optionally mixed May be.

  In the present invention, cellulose acylate is produced by esterification from cellulose. However, the above-mentioned particularly preferable cellulose is not always usable as it is, and linter, kenaf and pulp are purified and used.

In the present invention, cellulose acylate is a cellulose ester of a carboxylic acid having 2 to 22 carbon atoms in total.
The acyl group having 2 to 22 carbon atoms of the cellulose acylate used in the present invention may be an aliphatic acyl group or an aromatic acyl group, and is not particularly limited. They are, for example, alkyl carbonyl esters, alkenyl carbonyl esters, cycloalkyl carbonyl esters, aromatic carbonyl esters, aromatic alkyl carbonyl esters, and the like of cellulose, each of which may further have a substituted group. Examples of these preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, cyclohexanecarbonyl, adamantanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, (meth) acryloyl, and cinnamoyl groups. Among these, more preferred acyl groups are acetyl, propionyl, butanoyl, pentanoyl, hexanoyl, cyclohexanecarbonyl, (meth) acryloyl, phenylacetyl and the like.

  A method for synthesizing cellulose acylate is disclosed in JIII Journal of Technical Disclosure No. 2001-1745 (Invention Association, March 15, 2001) p. 9 is described in detail.

The cellulose acylate preferably used in the present invention preferably has a degree of substitution of cellulose with a hydroxyl group satisfying the following mathematical formulas (5) and (6).
Formula (5): 2.3 ≦ SA ′ + SB ′ ≦ 3.0.
Formula (6): 0 ≦ SA ′ ≦ 3.0.

  Here, SA ′ is the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution degree of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents. SA represents an acetyl group substituting a hydrogen atom of a hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting a hydrogen atom of a hydroxyl group of cellulose.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1). In the present invention, the total sum of substitution degrees of SA and SB (SA ′ + SB ′) is more preferably 2.6 to 3.0, and particularly preferably 2.80 to 3.00. Further, the degree of substitution (SA ′) of SA is more preferably 1.4 to 3.0, and particularly 2.3 to 2.9.

As the cellulose acylate suitably used in the present invention, it is preferable that the following formula (7) is satisfied at the same time.
Formula (7): 0 ≦ SB ”≦ 1.2.
Here, SB ″ represents the degree of substitution of the acyl group having 3 or 4 carbon atoms that replaces the hydrogen atom of the hydroxyl group of cellulose.

  Further, 28% or more of SB "is preferably a 6-position hydroxyl group substituent, more preferably 30% or more is a 6-position hydroxyl group substituent, more preferably 31% or more, and particularly 32% or more. It is also preferred that the substituent is a hydroxyl group at the 6-position. Furthermore, the sum of the substitution degrees of SA ′ and SB ″ at the 6-position of the cellulose acylate is 0.8 or more, more preferably 0.85 or more, A cellulose acylate film having a value of 0.90 or more can also be mentioned as a preferable example. These cellulose acylate films can produce a solution having a preferable solubility, and in particular, a non-chlorine organic solvent can produce a good solution.

The degree of substitution can be obtained by calculating the degree of binding of fatty acids bound to hydroxyl groups in cellulose. As a measuring method, it can measure based on ASTM-D817-91 and ASTM-D817-96. The state of substitution of the acyl group with the hydroxyl group is measured by ¹³ C NMR method.

  In the cellulose acylate film, the polymer component constituting the film is preferably made of cellulose acylate that substantially satisfies the above mathematical formulas (5), (6), and (7). “Substantially” means 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the total polymer components. The cellulose acylate may be used alone or in combination of two or more.

The viscosity average degree of polymerization (D _P ) of cellulose acylate is preferably 250 or more, and more preferably 290 or more. Cellulose acylate preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 5.0, and more preferably 1.0 to 3.0.

When using a polymer film for an optical compensation sheet, the polymer film preferably has a desired retardation value. The Re value and Rth value of the film are characteristic values that serve as references for the retardation value in the film plane and the retardation value in the thickness direction, respectively, and can be measured by, for example, a commercially available measuring instrument as described later. It is. Further, it is possible to three-dimensional directions of the refractive indices n _x, n _y, also n _z is measured.

  The preferred range of the retardation value of the polymer film varies depending on the liquid crystal cell in which the optical compensation sheet is used and the method of use thereof. The Re retardation value is preferably 0 to 200 nm, and the Rth retardation value is preferably adjusted in the range of 0 to 400 nm. When two optical compensation sheets are used in the liquid crystal display device, the Rth retardation value of the polymer film is preferably in the range of 0 to 250 nm. When one optical compensation sheet is used in the liquid crystal display device, the Rth retardation value of the polymer support film is preferably in the range of 0 to 400 nm.

  In order to adjust the retardation of the polymer film, a method of applying an external force such as stretching is generally used, but in some cases, a retardation increasing agent for adjusting optical anisotropy is added.

In order to adjust the retardation of the cellulose acylate film by adding a retardation increasing agent, it is preferable to use an aromatic compound having at least two aromatic rings as the retardation increasing agent. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Examples of such aromatic compounds include compounds described in European Patent No. 0911656A2, Japanese Patent Application Laid-Open Nos. 2000-1111914, 2000-275434, and the like.

  The above additives to be added to the polymer film, or additives that can be added according to various purposes {for example, an ultraviolet ray inhibitor, a release agent, an antistatic agent, a deterioration preventing agent (for example, an antioxidant, a peroxide decomposing agent) , Radical inhibitor, metal deactivator, acid scavenger, amine, etc.), infrared absorber, etc.} may be solid or oily. Furthermore, when a film is formed from multiple layers, the type and amount of additives in each layer may be different. For these details, the materials described in detail on pages 16 to 22 of the above-mentioned technique No. 2001-1745 are preferably used. The amount of these additives to be used is not particularly limited as long as the amount of each material exhibits its function, but it is preferably used in the range of 0.001 to 25% by mass in the entire polymer film composition.

[Production method of polymer film]
The polymer film is preferably produced by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which a polymer material is dissolved in an organic solvent.

  The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35% by mass. The surface of the drum or band is preferably finished in a mirror state.

  The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band and further dried by high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially.

  As a method for co-casting a plurality of cellulose acylate solutions of two or more layers as described above, for example, a solution containing cellulose acylate from a plurality of casting openings provided at intervals in the traveling direction of the support A method of casting a cellulose acylate solution from two casting ports (a method described in JP-A-6-134933) ), A method of wrapping a flow of a high-viscosity cellulose acylate solution with a low-viscosity cellulose acylate solution, and simultaneously extruding the high- and low-viscosity cellulose acylate solution (method described in JP-A-56-162617), etc. Is mentioned. The present invention is not limited to these.

  The manufacturing process of these solvent casting methods is described in detail on pages 22 to 30 of the above-mentioned public technical number 2001-1745, and includes dissolution, casting (including co-casting), metal support, drying, peeling. Categorized as stretching, etc.

  The thickness of the polymer support film is preferably 15 to 120 μm, more preferably 30 to 80 μm.

[Characteristics of polymer film]
(Hygroscopic expansion coefficient of film)
Further, the cellulose acylate film used for the optical compensation sheet in the present invention preferably has a hygroscopic expansion coefficient of 30 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is more preferably 15 × 10 ⁻⁵ /% RH or less, and further preferably 10 × 10 ⁻⁵ /% RH or less. Further, the hygroscopic expansion coefficient is preferably small, but usually a value of 1.0 × 10 ⁻⁵ /% RH or more. The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed at a constant temperature.

  By adjusting the hygroscopic expansion coefficient, it is possible to prevent a frame-like transmittance increase (light leakage due to distortion) while maintaining the optical compensation function of the optical compensation sheet.

The method for measuring the hygroscopic expansion coefficient is shown below.
A sample having a width of 5 mm and a length of 20 mm is cut out from the produced polymer film, and one end is fixed and suspended in an atmosphere of 25 ° C. and 20% RH (Rh ₀ ). A weight of 0.5 g is hung on the other end and left for 10 minutes to measure the length (L ₀ ). Next, with the temperature kept at 25 ° C., the humidity is set to 80% RH (Rh ₁ ), and the length (L ₁ ) is measured.
The hygroscopic expansion coefficient is calculated by the following mathematical formula (8). The measurement is performed 10 samples for the same sample, and the average value is adopted.
Formula (8): Hygroscopic expansion coefficient (/% RH) = {(L ₁ −L ₀ ) / L ₀ } / (Rh ₁ −Rh ₀ ).

  In order to reduce the dimensional change due to moisture absorption of the polymer film, it is preferable to add a compound having a hydrophobic group or fine particles. As the compound having a hydrophobic group, a material corresponding to a plasticizer or a degradation inhibitor having a hydrophobic group such as an aliphatic group or an aromatic group in the molecule is particularly preferably used. It is preferable that the addition amount of these compounds exists in the range of 0.01-10 mass% with respect to the solution (dope) to adjust. In addition, the free volume in the polymer film may be reduced. Specifically, the free volume is reduced by reducing the amount of residual solvent during film formation by the above-described solvent casting method. It is preferable to dry under the condition that the residual solvent amount with respect to the cellulose acylate film is in the range of 0.01 to 1.00% by mass.

(Mechanical properties of film)
(curl)
The curl value in the width direction of the polymer film used in the present invention is preferably -7 / m to + 7 / m. If the curl value in the width direction of the transparent protective film is within the above-mentioned range when performing on a long and wide polymer film, the handling of the film and the film will not be cut, and the film At the edges and center of the film, dust generation due to strong contact of the film with the transport roll and adhesion of foreign matter on the film are reduced, and the frequency of point defects and coating streaks of the optical compensation sheet of the present invention is acceptable. Is preferable. Further, it is preferable because bubbles can be prevented from entering when the polarizing film is bonded.

  The curl value can be measured according to a measurement method (ANSI / ASCPH1.29-1985) defined by the American National Standards Institute.

The residual solvent amount of the polymer film used in the present invention is preferably 1.5% by mass or less because curling can be suppressed. Furthermore, it is more preferable that it is 0.01-1.0 mass% or less. This is presumably because free deposition is reduced by reducing the amount of residual solvent during film formation by the above-described solution casting film forming method.

(Tear strength)
The tear strength of the cellulose acylate film is 2 g or more based on the tear test method (Elmendorf tear method) of JIS K-7128-2: 1998. It is preferable at the point which can fully hold | maintain. More preferably, it is 5-25g, More preferably, it is 6-25g. Moreover, when converted into a film thickness of 60 μm, 8 g or more is preferable, and 8 to 15 g is more preferable. Specifically, it can be measured using a light load tear strength tester after conditioning a sample piece of 50 mm × 64 mm under the conditions of 25 ° C. and 65% RH for 2 hours.

(Scratch strength)
The scratch strength is preferably 2 g or more, more preferably 5 g or more, and particularly preferably 10 g or more. By setting it within this range, the scratch resistance and handling properties of the film surface can be maintained without any problem. The scratch strength can be evaluated by scratching the surface of the transparent protective film with a sapphire needle having a cone apex angle of 90 ° and a tip radius of 0.25 m, and with a load (g) at which the scratch mark can be visually confirmed. .

(Equilibrium moisture content of film)
In the present invention, as will be described later, the optical compensation sheet can also be used as one protective film of the polarizing plate. The equilibrium water content of the resulting cellulose acylate film is preferably 0 to 4% by mass at 25 ° C. and 80% RH regardless of the film thickness. The content is more preferably 0.1 to 3.5% by mass, and particularly preferably 1 to 3% by mass. If the equilibrium moisture content is less than or equal to the upper limit, when the cellulose acylate film is used as a protective film for a polarizing plate (that is, the cellulose acylate film as a polymer support film in the optical compensation sheet also serves as a protective film for the polarizing plate. In this case, the dependence of the retardation on the humidity change is not too great.

  The moisture content was measured by applying a cellulose acylate film sample 7 mm × 35 mm to the Karl Fischer method using a moisture measuring device “CA-03” and a sample drying apparatus “VA-05” (both manufactured by Mitsubishi Chemical Corporation). I did. The moisture content is calculated by dividing the moisture content (g) by the sample mass (g).

(Water permeability of film)
The moisture permeability of the cellulose acylate film used in the present invention is measured under the conditions of a temperature of 60 ° C. and 95% RH based on JIS Z-0208, and the obtained value is converted to a film thickness of 80 μm. . Translucent humidity 400~2000g / m ² · 24h, and it is more preferable 500~1800g / m ² · 24h, in particular in the range of 600~1600g / m ² · 24h. If the moisture permeability is equal to or less than the upper limit, it is preferable because the absolute value of the humidity dependency of the retardation value of the film rarely exceeds 0.5 nm /% RH. In addition, an optical compensation sheet obtained by laminating an optically anisotropic layer on a cellulose acylate film is preferable because the absolute value of the humidity dependence of the Re value and Rth value is less than 0.5 nm /% RH. In addition, when such a polarizing plate with an optical compensation sheet is incorporated in a liquid crystal display device, it is preferable because problems such as a change in color and a decrease in viewing angle are hardly caused. On the other hand, if the moisture permeability is equal to or higher than the lower limit value, when the polarizing plate is prepared by being attached to both surfaces of the polarizing film, the cellulose acylate film prevents the adhesive from being dried and causes poor adhesion. This is preferable because it is less likely to cause defects.

  If the film thickness of the cellulose acylate film is thick, the moisture permeability becomes small, and if the film thickness is thin, the moisture permeability becomes large. Therefore, it is necessary to convert the sample of any film thickness to a standard of 80 μm. Conversion of the film thickness is obtained as (water vapor permeability in terms of 80 μm = measured water vapor permeability × measured film thickness μm / 80 μm).

The measurement method of moisture permeability is "Polymer Physical Properties II" (Polymer Experiment Course 4, Kyoritsu Shuppan), pages 285-294: Measurement of vapor permeation (mass method, thermometer method, vapor pressure method, adsorption amount method) The cellulose acylate film sample 70 mmφ of the present invention was conditioned at 25 ° C., 90% RH, 60 ° C., and 95% RH for 24 hours, respectively, and a moisture permeation test apparatus {“KK- 709007 “Toyo Seiki Co., Ltd.” according to JIS Z-0208 calculates the amount of water per unit area (g / m ² ), and obtains moisture permeability = mass after moisture conditioning−mass before moisture conditioning.

[Surface treatment of polymer film]
The polymer film is preferably subjected to a surface treatment. The surface treatment includes corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment and ultraviolet irradiation treatment. Details of these are described in detail on pages 30 to 32 of the aforementioned public technical number 2001-1745. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

(Alkaline saponification treatment)
The alkali saponification treatment may be either immersion in a saponification solution or application of a saponification solution, but a coating method is preferred. Examples of the coating method include a dip coating method, a curtain coating method, a die coating method (extrusion coating method, slide coating method, extrusion coating method), a gravure coating method, and a bar coating method. Examples of the alkali saponification solution include potassium hydroxide solution and sodium hydroxide solution, and the concentration of hydroxide ions is preferably in the range of 0.1 to 3.0 mol / L. Furthermore, as an alkali treatment liquid, a solvent (for example, isopropyl alcohol, n-butanol, methanol, ethanol, etc.) having good wettability to the film, a surfactant, a wetting agent (for example, diols, glycerin, etc.) is contained. Thus, the wettability of the saponification solution to the transparent support, the aging stability of the saponification solution, etc. are improved. Specifically, description of the content is mentioned, for example in Unexamined-Japanese-Patent No. 2002-82226, international publication 02/46809 pamphlet, Unexamined-Japanese-Patent No. 2003-43673.

  Instead of or in addition to the surface treatment, an undercoat layer (described in JP-A-7-333433) is applied, or a resin layer such as gelatin containing both a hydrophobic group and a hydrophilic group is further formed. As a first layer that is applied only as a first layer, a layer that adheres well to the polymer film (hereinafter abbreviated as the first undercoat layer) is provided, and a hydrophilic property such as gelatin that adheres well to the alignment film as the second layer thereon. The content of a so-called multi-layer method (for example, described in JP-A No. 11-248940) in which a resin layer (hereinafter abbreviated as a second undercoat layer) is applied.

(Optically anisotropic layer)
Next, details of preferred embodiments of the optically anisotropic layer made of a liquid crystalline compound will be described.
The optically anisotropic layer is preferably designed so as to compensate for the liquid crystalline compound in the liquid crystal cell in the black display of the liquid crystal display device. The alignment state of the liquid crystal compound in the liquid crystal cell in black display varies depending on the mode of the liquid crystal display device. Regarding the alignment state of the liquid crystal compound in this liquid crystal cell, “IDW'00, FMC7-2”, p. 411-414.

In the alignment of the optically anisotropic layer containing a liquid crystalline compound, it is generally very difficult to strictly control the tilt angle, the twist angle, and the like. In addition, it is often difficult to verify whether the target orientation is obtained. In the first place, the purpose of strictly adjusting the alignment state of the optically anisotropic layer is to effectively perform optical compensation in accordance with the polarization state of the light that has passed through the liquid crystal cell. Therefore, the characteristics of the optical compensation sheet are also birefringence characteristics, that is, It is considered that adjusting the angle dependency of retardation is a simple and most effective method for effectively improving the contrast viewing angle.

Therefore, as the optical components of the optical compensation sheet in the present invention, as described above, the transparent support film having a negative birefringence, and the optically anisotropic layer oriented on the gradient coating thereon. And a retardation value of the optical compensation sheet measured from the normal direction of the optically anisotropic layer: Re is 40 nm or more, and + 40 ° from the film normal in a plane orthogonal to the film including the orientation direction. The retardation value of the optical compensation sheet measured from the inclined direction: Re ⁽⁺⁴⁰⁾ and Re: ratio Re ⁽⁺⁴⁰⁾ / Re is less than 2.0, and is orthogonal to the film including the orientation direction. Retardation value of optical compensation sheet: Re ⁽⁻⁴⁰⁾ and Re: Re ⁽⁻⁴⁰⁾ / Re is 0.4 or more as measured from the direction inclined −40 ° from the film normal in the plane. Adjusted as In Rukoto, the contrast viewing angle of the liquid crystal display device it is possible to extremely improve. The optical compensation sheet in the present invention is particularly effective for normally white TN oriented cells.
First, after describing the alignment film, a liquid crystal compound used for the optically anisotropic layer, a method for forming the optically anisotropic layer, and the like will be described.

[Alignment film]
The optical compensation sheet used in the present invention is preferably provided with an alignment film between the polymer support film surface-treated as described above and the optically anisotropic layer provided thereon.
The alignment film has a function of defining the alignment direction of the liquid crystalline molecules. Therefore, the alignment film is indispensable for realizing a preferred embodiment of the present invention. However, if the alignment state is fixed after aligning the molecules of the liquid crystalline compound, the alignment film plays the role, and is not necessarily an essential component of the present invention. That is, it is possible to produce the polarizing plate of the present invention by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizing film.

  The alignment film is an organic compound (for example, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodget method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate, etc.). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.

  The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules.

  In the present invention, in addition to the function of aligning liquid crystalline molecules, a crosslinkable function having a function of bonding side chains having a crosslinkable functional group (for example, a double bond) to the main chain or aligning liquid crystal molecules. It is preferred to introduce the group into the side chain.

  As the polymer used for the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used.

Examples of such polymers include, for example, methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohols and modified polyvinyl alcohols described in paragraph No. [0022] of JP-A-8-338913, poly ( N-methylolacrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers {eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol, etc.} are preferred, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. preferable. It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization.

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

  A side chain having a function of aligning liquid crystal molecules generally has a hydrophobic group as a functional group. 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 those described in paragraph numbers [0022] to [0145] of JP-A No. 2000-155216 and paragraph numbers [0018] to [0022] of JP-A No. 2002-62426. Can be mentioned.

  By connecting a side chain having a crosslinkable functional group to the main chain of the alignment film polymer, or introducing a crosslinkable functional group into a side chain having a function of aligning liquid crystalline molecules, an optical difference from the polymer of the alignment film is obtained. A polyfunctional monomer contained in the isotropic layer can be copolymerized. As a result, not only between the polyfunctional monomer and the polyfunctional monomer, but also between the alignment film polymer and the alignment film polymer and between the polyfunctional monomer and the alignment film polymer is firmly bonded by a covalent bond. Therefore, the strength of the optical compensation sheet can be remarkably improved by introducing the crosslinkable functional group into the alignment film polymer.

  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] of JP-A No. 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. Specifically, for example, compounds described in paragraph Nos. [0023] to [0024] of JP-A No. 2002-62426 may be mentioned. 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 the above polymer containing a crosslinking agent, which is an alignment film forming material, on the support film, followed by drying by heating (crosslinking) and rubbing treatment. . As described above, the crosslinking reaction can be carried out at any time after coating on the support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating liquid is preferably a mixed solvent of an organic solvent (for example, 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 layer surface of an orientation film and also an optically anisotropic layer reduces remarkably.

  The coating method of the alignment film is preferably a spin coating method, dip coating method, curtain coating method, die coating method (extrusion coating method, slide coating method, extrusion coating method, slot die coating), rod coating method or roll coating method. . Of these coating methods, the slot die coating method is most 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 provided on the support or the undercoat layer. 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 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.

Next, the alignment film functions to align the liquid crystalline molecules of the optically anisotropic layer provided on the alignment film. Thereafter, as necessary, the alignment film polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment film polymer is crosslinked using a crosslinking agent.
The thickness of the alignment film is preferably in the range of 0.1 to 10 μm.

[Liquid crystal compounds]
The liquid crystalline compound used for the optically anisotropic layer includes a rod-like liquid crystalline compound and a discotic liquid crystalline compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a polymer liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity.

(Bar-shaped liquid crystalline compound)
Examples of rod-like liquid crystalline compounds 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.

  The rod-like liquid crystalline compound includes a metal complex. Moreover, the liquid crystal polymer which contains a rod-shaped liquid crystalline compound in a repeating unit can also be used as a rod-shaped liquid crystalline compound. In other words, the rod-like liquid crystalline compound may be bonded to a (liquid crystal) polymer.

For rod-like liquid crystalline compounds, see “Quarterly Chemical Review”, Volume 22 “Liquid Crystal Chemistry” (1994).
(Chapter 4), Chapter 7 and Chapter 11 of (Chemical Society of Japan) and Chapter 3 of "Liquid Crystal Device Handbook" (Japan Society for the Promotion of Science, 142nd Committee).

  The birefringence of the rod-like liquid crystalline compound is preferably in the range of 0.001 to 0.7.

  The rod-like liquid crystalline compound preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable group and the polymerizable group described in paragraph numbers [0064] to [0086] of JP-A-2002-62427 A liquid crystal compound is mentioned.

(Discotic liquid crystalline compounds)
Examples of discotic liquid crystal compounds include C.I. A benzene derivative described in a research report of Destrade et al., “Mol. Cryst.”, 71, 111 (1981), C.I. Dextrade et al., “Mol. Cryst.”, 122, 141 (1985), “Physics lett, A”, 78, 82 (1990); Kohne et al., “Angew. Chem.”, Vol. 96, p. 70 (1984); M.M. Lehn et al., “J. Chem. Commun.”, P. 1794 (1985), J. Chem. This includes the azacrown and phenylacetylene macrocycles described in the research report of Zhang et al., “J. Am. Chem. Soc.”, 116, 2655 (1994).

  As a discotic liquid crystalline compound, a compound having liquid crystallinity in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule Is also included. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. The optically anisotropic layer formed from the discotic liquid crystalline compound does not necessarily require that the compound finally contained in the optically anisotropic layer is a discotic liquid crystalline compound, for example, a low molecular weight discotic liquid crystalline compound. Includes a group that reacts with heat or light, and as a result, is polymerized or cross-linked by reaction with heat or light to increase the molecular weight and lose liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284.

  In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. Examples thereof include compounds described in JP-A 2000-155216, paragraph numbers [0151] to “0168”.

  In the hybrid alignment, the angle between the long axis (disk surface) of the discotic liquid crystalline compound and the surface of the polarizing film increases or decreases in the depth direction of the optically anisotropic layer and with increasing distance from the surface of the polarizing film. is doing. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the angle includes a region where the angle does not change, the angle only needs to increase or decrease as a whole. Furthermore, it is preferable that the angle changes continuously.

The average direction of the major axis of the discotic liquid crystalline compound on the polarizing film side can be generally adjusted by selecting the discotic liquid crystalline compound or the material of the alignment film, or by selecting the rubbing treatment method. Moreover, the major axis (disk surface) direction of the disk-like liquid crystalline compound on the surface side (air side) is generally adjusted by selecting the type of additive used together with the disk-like liquid crystalline compound or the disk-like liquid crystalline compound. can do. Examples of the additive used together with the discotic liquid crystalline compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can be adjusted by selecting the liquid crystal compound and the additive as described above.

[Other compositions of optically anisotropic layer]
Along with the liquid crystal compound, a plasticizer, a surfactant, a polymerizable monomer, and the like can be used together to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal compound, and the like. It is preferable that the compound has compatibility with the liquid crystal compound and can change the tilt angle of the liquid crystal compound or does 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 polymerizable group-containing liquid crystalline compound. Examples thereof include those described in JP-A-2002-296423, paragraph numbers [0018] to [0020]. 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 compound.

  Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include compounds described in paragraph numbers [0028] to [0056] of JP-A No. 2001-330725.

The polymer used together with the discotic liquid crystalline compound is preferably one that can change the tilt angle of the discotic liquid crystalline compound.
Examples of such polymers include cellulose esters. Preferable examples of the cellulose ester include those described in paragraph No. [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 compound 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 discotic liquid crystalline compound is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

[Formation of optically anisotropic layer]
The optically anisotropic layer can be formed by applying a liquid crystal compound and, if necessary, a coating liquid containing a polymerization initiator and an optional component described later on the alignment film.

  As the 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, Tetrachloroethane), esters (eg methyl acetate, butyl acetate), ketones (eg acetone, methyl ethyl ketone), ethers (eg tetrahydrofuran, 1,2-dimethoxyethane) and the like. Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

Application | coating of a coating liquid can be implemented by a conventionally well-known method, and the thing of the content as described in the said oriented film is mentioned.
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

[Fixation of alignment state of liquid crystalline compound]
The aligned liquid crystalline compound can be fixed while maintaining the alignment state of the molecules. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. 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 substitution 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 ( U.S. Pat. No. 3,549,367), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (described in U.S. Pat. No. 4,221,970) It is.

  The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays.
The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  A protective layer may be further provided on the optically anisotropic layer.

<Polarizing plate>
[Polarizing film]
As described above, the liquid crystal display device of the present invention includes a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and at least one optical compensation sheet disposed between the liquid crystal cell and the polarizing plate. The optical compensation sheet exhibits its function remarkably by being bonded to a polarizing plate, or preferably used as a protective film for a polarizing plate (directly bonding a polarizing film and an optical compensation sheet).
Further, the optically anisotropic layer (when providing a plurality of optically anisotropic layers, the first optically anisotropic layer closest to the polarizing film) is formed directly on the polarizing film from a liquid crystalline compound, or It can also be formed from a liquid crystalline compound via an alignment film (that is, an optical compensation sheet can be formed without using a polymer support film). Specifically, the optically anisotropic layer is formed by directly applying such a coating liquid for the optically anisotropic layer onto the surface of the polarizing film. As a result, without using a polymer film between the polarizing film and the optically anisotropic layer, a thin polarizing plate having a small stress (strain × cross-sectional area × elastic modulus) associated with the dimensional change of the polarizing film is produced. . When the polarizing plate according to the present invention is attached to a large liquid crystal display device, an image with high display quality is displayed without causing problems such as light leakage.

  The polarizing film is manufactured by Optiva Inc. A polarizing film composed of a coating type polarizing film represented by 1 or a base film and iodine or a dichroic dye is preferable.

  Iodine and dichroic dye in the polarizing film exhibit deflection performance by being oriented in the substrate film. It is preferable that the iodine and the dichroic dye are aligned along the molecules of the base film, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal.

Currently, a commercially available polarizing film is generally produced by immersing a stretched substrate film in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the substrate film. Is.
The commercially available polarizing film has iodine or dichroic dye distributed about 4 μm (about 8 μm on both sides) from the surface of the base film, and a thickness of at least 10 μm is necessary to obtain sufficient polarizing performance. . The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time.

  As described above, the lower limit of the substrate film thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed in a 17-inch liquid crystal display device, which is preferable.

The base film of the polarizing film may be cross-linked.
For the substrate film to be crosslinked, a polymer that can be crosslinked per se can be used. A polarizing film can be formed by reacting a polymer having a functional group or a base film obtained by introducing a functional group into the polymer with light, heat, or pH change between the polymers of the base film.

Moreover, you may introduce | transduce a crosslinked structure into the polymer of a base film with a crosslinking agent.
Crosslinking is generally carried out by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is only necessary to ensure durability at the final product stage, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

For the base film of the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Examples of the polymer include the same polymers as those described in the alignment film, and polyvinyl alcohol and modified polyvinyl alcohol are most preferable. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509, and JP-A-9-316127.
Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  The amount of the crosslinking agent added to the substrate film is preferably 0.1 to 20% by mass relative to the substrate film. Thereby, the orientation of the polarizing film and the heat-and-moisture resistance of the polarizing film are improved.

  The polarizing film contains some crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less and more preferably 0.5% by mass or less in the alignment film. In this way, even if the polarizing film is incorporated in a liquid crystal display device and used for a long time or left in a high temperature and high humidity atmosphere for a long time, the degree of polarization does not decrease.

  The crosslinking agent is described in US Reissue Patent 23297. Further, when the substrate film is polyvinyl alcohol or modified polyvinyl alcohol, boron compounds (for example, boric acid and borax) can also be used as a crosslinking agent.

As the dichroic dye, an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye or an anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (for example, a sulfo group, an amino group, a hydroxyl group, etc.).

  Examples of the dichroic dye include compounds described in, for example, the Japan Society for Invention and Innovation, Japanese Patent No. 2001-1745, page 58 (issued on March 15, 2001).

  In order to increase the contrast ratio of the liquid crystal display device, the transmittance of the polarizing plate is preferably higher and the degree of polarization is preferably higher. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50% in light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

  As described above, the optical compensation sheet suitably used in the present invention can be bonded to a polarizing plate or directly bonded to a polarizing film. Moreover, when not using a support film for an optical compensation sheet, it is also possible to arrange | position a polarizing film and an optically anisotropic layer or a polarizing film, and an orientation film through an adhesive agent. As the adhesive, a polyvinyl alcohol resin (including a modified polyvinyl alcohol with an acetoacetyl group, a sulfonic acid group, a carboxyl group, or an oxyalkylene group) or an aqueous boron compound solution can be used. A polyvinyl alcohol resin is preferred. The thickness of the adhesive layer is preferably in the range of 0.01 to 10 μm after drying, and particularly preferably in the range of 0.05 to 5 μm.

[Production of polarizing plate]
The most common method of polarizing film is to continuously stretch between a plurality of rollers. From the viewpoint of yield, the base film is tilted by 10 to 80 ° with respect to the longitudinal direction (MD direction) of the polarizing film. Then, after being stretched (stretching method) or rubbed (rubbing method), it is preferable to dye with iodine or a dichroic dye. The tilt angle is preferably stretched so as to match the angle formed between the transmission axes of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell.

  A normal inclination angle is 45 °. Recently, however, devices that are not necessarily 45 ° have been developed for transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

  In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be performed in several steps including oblique stretching. By dividing into several times, it is possible to stretch more uniformly even at high magnification. Before the oblique stretching, a slight stretching (a degree to prevent shrinkage in the width direction) may be performed horizontally or vertically.

Stretching can be performed by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. In biaxial stretching, stretching is performed at different speeds on the left and right, so that the thickness of the base film before stretching needs to be different on the left and right. In casting film formation, by tapering the die, it is possible to make a left-right difference in the flow rate of the base film forming solution.
As described above, a binder film that is obliquely stretched by 10 to 80 ° with respect to the MD direction of the polarizing film is produced.

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

  The rubbing treatment is preferably carried out using a rubbing roll whose roundness, cylindricity, and runout (eccentricity) are all 30 μm or less. The wrap angle of the base film on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more.

  When rubbing a long film, it is preferable to transport the film at a speed of 1 to 100 m / min with a constant tension by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a TN liquid crystal display device, 0 to 10 ° is preferable. 0 ° is particularly preferred.

  A polymer film is preferably disposed as a protective film on the surface of the polarizing film opposite to the optically anisotropic layer (arrangement of optically anisotropic layer / polarizing film / protective film). As the protective film, those described in [Support] in <Optical Compensation Sheet> can be suitably used. The protective film is also preferably provided with an antireflection film or antiglare layer having an antifouling property and scratch resistance on the outermost surface. Any conventionally known antireflection film and antiglare layer can be used.

  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.

Example 1
An optical compensation sheet and an elliptically polarizing plate having the configuration shown in FIG. 1 were prepared.

<Preparation of optical compensation sheet>
[Preparation of cellulose acylate film]
[Preparation of cellulose acylate stock solution]
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acylate stock solution.

(Cellulose acylate stock composition)
Cellulose acetate 100 parts by weight Acetic acid degree 60.7-61.1%
Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 336 parts by weight Methanol (second solvent) 29 parts by weight 1-butanol (third solvent) 11 parts by mass

In another mixing tank, 16 parts by mass of the following retardation increasing agent, 92 parts by mass of methylene chloride and 8 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution. Next, 31 parts by mass of the retardation increasing agent solution was mixed with 474 parts by mass of the cellulose acylate stock solution, and the dope was prepared by sufficiently stirring.
Retardation raising agent:

  The obtained dope was cast using a band stretching machine. After the film surface temperature on the band reached 40 ° C., the film was dried with warm air of 70 ° C. for 1 minute, and the film from the band was dried with 140 ° C. drying air for 10 minutes. A cellulose acylate film (thickness: 80 μm) was prepared.

  When the in-plane retardation (Re) and the retardation in the film thickness direction (Rth) of the produced cellulose acylate film were measured at a wavelength of 590 nm by the following method, Re was 8 nm and Rth was 91 nm.

[Measurement of Re and Rth]
The obtained cellulose acylate film was evaluated at a wavelength of 590 nm using the following method.
Re is measured by making light incident in the normal direction of the film in “KOBRA 21ADH” (manufactured by Oji Scientific Instruments). Rth is obtained by making light incident from a direction inclined + 40 ° with respect to the normal direction of the film, using Re and the in-plane slow axis (determined by “KOBRA 21ADH”) as an inclination axis (rotation axis). The measured retardation value and the retardation value measured by making light incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH calculates based on the retardation value measured in the direction, the assumed value of the average refractive index, and the input film thickness value.

  Here, as the assumed value of the average refractive index, “Polymer Handbook” (John Wiley & Sons, Inc.) and catalog values of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer.

Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), polystyrene (1.59).
Average refractive index of the assumed value and by inputting the thickness "KOBRA 21ADH" calculates the _{n x, n y, n z} .

[Alkaline saponification]
The cellulose acylate film produced above was immersed in a 2.0 mol / L potassium hydroxide solution (25 ° C.) for 2 minutes, then neutralized with sulfuric acid, washed with pure water and dried. The surface energy of this film was determined by the contact angle method and found to be 63 mN / m.

[Production of optical compensation sheet]
[Preparation of alignment film for optically anisotropic layer]
On this cellulose acylate film, a coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds.

(Orientation film coating solution composition)
The following modified polyvinyl alcohol 20 parts by mass Water 360 parts by mass Methanol 120 parts by mass Glutaraldehyde (crosslinking agent) 1.0 part by mass

  Modified polyvinyl alcohol:

[Preparation of optically anisotropic layer]
In the optical compensation sheet manufacturing process, the web is fed by a feeding machine, passes through a coating process by a rubbing roll and slot die coating while being supported by a guide roll, and then passes through a drying process. After that, the basic process is to pass through a drying zone, a heating zone, and an ultraviolet lamp and wind up by a winder. On the opposite side of the web in the direction of travel, a decompression chamber was installed at a position where it did not come into contact with the bead so that sufficient decompression adjustment was possible.

The upstream lip land length I _UP of the slot die shown in FIG. 2 was 1 mm, and the downstream lip land length I _L0 was 50 μm. Using this slot die, the coating solution was applied at 5 ml / m ² on the web so that the wet film thickness was 5 μm. The coating speed was 50 m / min. The cellulose acylate film coated with the alignment film was used for the web, and the length of the gap between the downstream lip land and the cellulose triacylate film as the web was set to 40 μm. The surface of the alignment film application surface was subjected to a rubbing treatment and conveyed to the application process as it was for application. In the rubbing treatment, the alignment film was rubbed in a direction parallel to the slow axis of the cellulose acylate film. The rotational peripheral speed of the rubbing roller in the rubbing treatment was 5.0 m / sec, and the pressing pressure against the alignment layer resin layer was set to 9.8 × 10 ⁻³ Pa.

  As the coating solution, the following coating solution composition 1 for an optically anisotropic layer was used. The coating speed was 50 m / min. Immediately after coating, initial drying was performed using the dryer 33 shown in FIG. The total length of the dryer 33 was 5 m. The condensing plate 32 in the dryer 33 is arranged with a predetermined inclination angle such that the downstream side in the running direction is separated from the coating film. The distance between the condenser plate 32 and the web, the temperature of the condenser plate, and the temperature of the coating liquid were controlled and adjusted so that the Rayleigh number was 1200. The web initially dried by the dryer 33 is passed through a heating zone set at 130 ° C., and the surface of the liquid crystal layer is irradiated with ultraviolet rays by a 160 W / cm ultraviolet lamp in an atmosphere at 60 ° C. to obtain an optical compensation sheet (KH− 1) was produced.

(Optically anisotropic layer coating solution composition 1)
The following composition was dissolved in 102 parts by mass of methyl ethyl ketone to prepare a coating solution.
41.0 parts by mass of the following discotic liquid crystalline compound Ethylene oxide modified trimethylolpropane triacrylate “V # 360”: 4.06 parts by mass of Osaka Organic Chemical Co., Ltd. 0.34 parts by mass of cellulose acetate butyrate “CAB551- 0.2 ": Eastman Chemical Japan Co., Ltd. Cellulose Acetate Butyrate 0.11 parts by mass" CAB531-1 ": Eastman Chemical Japan Co., Ltd. Fluoro aliphatic group-containing polymer (1) 0.03 Part by mass The following fluoroaliphatic group-containing polymer (2) 0.23 parts by mass Photopolymerization initiator 1.35 parts by mass “Irgacure 907”: Sensitizer 0.45 parts by mass manufactured by Ciba Specialty Chemicals Kayacure DETX ": Nippon Kayaku Co., Ltd.

[Characteristic evaluation of optical compensation sheet]
When the produced optical compensation sheet was placed between polarizing plates in a crossed Nicol arrangement and planar observation was performed, the optically anisotropic layer had no defects such as schlieren, and even if the viewing angle was changed from any direction, unevenness etc. There was no uniform film. In addition, with a microtome, an ultrathin section of the optical compensation sheet was cut out so that the rubbing treatment direction was a cross section, and observed while rotating the stage with a polarizing microscope, the direction of quenching in the thickness direction was different, Obviously, the hybrid orientation was found.

  The Re and Rth values of the produced optical compensation sheet were measured at a wavelength of 590 nm using “KOBRA 21ADH” (manufactured by Oji Scientific Instruments). The retardation of the cellulose acylate film used for the support was measured in the same manner, and the retardation value of the optically anisotropic layer was calculated from the difference. Moreover, the same measurement was performed at wavelengths of 450 nm, 550 nm, and 610 nm, and the wavelength dependency was measured. The results are shown in Table 1 below.

<Preparation of polarizing plate>
The prepared optical compensation sheet was immersed in a 1.5 mol / L NaOH aqueous solution at 50 ° C. for 1.5 minutes to make the surface hydrophilic, neutralized with sulfuric acid, washed with pure water, Dried. Similarly, the cellulose triacetate film “TD-80U” (manufactured by Fuji Photo Film Co., Ltd.) with a thickness of 80 μm is subjected to a hydrophilic treatment and is disposed on the surface of the polarizing plate opposite to the optical compensation sheet to protect the polarizing film. Used as.

  A polarizing film is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and then the above-mentioned hydrophilized optical compensation sheet and polarizing film protective film are respectively applied to both sides of the polarizing film using a polyvinyl alcohol-based adhesive. Pasted. In the optical compensation sheet, the surface on which the optically anisotropic layer was not applied was bonded to the polarizing film. The absorption axis of the polarizing film and the slow axis (parallel to the casting direction) of the support of the optical compensation sheet were arranged in parallel. Thus, an elliptically polarizing plate was produced.

<Production of liquid crystal cell and liquid crystal display device>
The liquid crystal cell has a cell gap (d) of 4.5 μm, a positive dielectric constant anisotropic layer, and a liquid crystal material having a chromatic dispersion Δn ₍₄₅₀₎ / Δn ₍₅₅₀₎ of 1.05 is dropped between the substrates. And Δnd was set to 400 nm (Δn is the refractive index anisotropy of the liquid crystal material). The twist angle of the liquid crystal cell liquid crystal layer is 90 °, and as shown in FIG. 1, the prepared polarizing plate is arranged so that the absorption axis of the polarizing plate coincides with the upper and lower substrate rubbing directions of the liquid crystal cell above and below the cell. It bonded together through the adhesive. In addition, a cell patterned in a dot matrix was also produced, and the moving image display characteristics by visual observation were evaluated.

[Optical measurement of the manufactured liquid crystal display]
A rectangular wave voltage of 60 Hz was applied to the liquid crystal display device thus manufactured. A normally white mode with a white display of 1.5 V and a black display of 5.6 V was set. “EZ-Contrast 160D” (manufactured by ELDIM) is used as the measuring device, and the contrast ratio, which is the transmittance ratio (white display / black display), black display (L1) and white display (L8), and the transmittance are equally spaced. The transmittance viewing angle was measured at 8 gradations. A range in which the transmittance of gradations adjacent in the downward direction is not reversed and a contrast ratio is 10 or more was measured. The results are shown in Table 1.

[Response speed measurement of the manufactured liquid crystal display]
The response time for changing the luminance from white display to black display was measured by driving the manufactured liquid crystal display device by the above method. The response time was defined as the time from the start of the black display drive until the luminance change reached 90% of the luminance difference between the white display and the black display. Similarly, the response time from black display to white display was also measured, and finally, a value with a large response time was measured as the response speed.

Example 2
A liquid crystal display device was produced in the same manner as in Example 1 except that the following optically anisotropic layer coating solution composition 2 was used.

(Optical anisotropic layer coating solution composition 2)
The following composition was dissolved in 95 parts by mass of methyl ethyl ketone to prepare a coating solution.
41.0 parts by mass of the discotic liquid crystalline compound Ethylene oxide-modified trimethylolpropane triacrylate “V # 360”: 4.06 parts by mass of Osaka Organic Chemical Co., Ltd. 0.34 parts by mass of cellulose acetate butyrate “CAB551-0” .2 ": Eastman Chemical Japan Co., Ltd. Cellulose Acetate Butyrate 0.11 parts by mass" CAB531-1 ": Eastman Chemical Japan Co., Ltd. said fluoro aliphatic group-containing polymer (1) 0.04 parts by mass The fluoroaliphatic group-containing polymer (2) 0.23 parts by mass Photopolymerization initiator 1.35 parts by mass “Irgacure 907”: Sensitizer 0.45 parts by mass “Cayacure DETX” manufactured by Ciba Specialty Chemicals Co., Ltd. : Nippon Kayaku Co., Ltd.

Example 3
In the same manner as in Example 1, except that the cellulose acylate support film having an Re of 9 nm and an Rth value of 103 nm was used by adjusting the addition amount of the retardation increasing agent of the cellulose acylate film. A display device was produced.

Comparative Example 1
A liquid crystal display device was produced in the same manner as in Example 1 except that the gap of the liquid crystal cell was 5.0 μm. At this time, Δnd of the liquid crystal cell was 445 nm.

Comparative Example 2
A liquid crystal display device was produced in the same manner as in Example 1 except that a liquid crystal compound different from that used in the liquid crystal cell of Example 1 was used and the cell gap was set to 4.2 μm. The wavelength dispersion Δn ₍₄₅₀₎ / Δn ₍₅₅₀₎ of the liquid crystal composition was 1.12, and Δnd of the liquid crystal cell was 420 nm.

Comparative Example 3
A liquid crystal display device was produced in the same manner as in Example 1 except that a liquid crystal compound different from that used in the liquid crystal cell of Example 1 was used and the cell gap was 5.0 μm. The wavelength dispersion Δn ₍₄₅₀₎ / Δn ₍₅₅₀₎ of the liquid crystal composition was 1.03, and Δnd of the liquid crystal cell was 400 nm.

Comparative Example 4
An optical compensation sheet and elliptically polarized light were prepared in the same manner as in Example 1 except that the following optical anisotropic layer coating solution composition 3 was used.

(Optical anisotropic layer coating solution composition 3)
The following composition was dissolved in 100 parts by mass of methyl ethyl ketone to prepare a coating solution.
The discotic liquid crystalline compound 41.0 parts by mass Ethylene oxide modified trimethylolpropane triacrylate “V # 360”: Osaka Organic Chemical Co., Ltd. 4.06 parts by mass Cellulose acetate butyrate 0.90 parts by mass “CAB551-0” .2 ": Eastman Chemical Japan Co., Ltd. Cellulose Acetate Butyrate 0.20 parts by mass" CAB531-1 ": Eastman Chemical Japan Co., Ltd. said fluoroaliphatic group-containing polymer (2) 0.23 parts by mass Photopolymerization initiator 1.35 parts by mass “Irgacure 907” manufactured by Ciba Specialty Chemicals Co., Ltd. 0.45 parts by mass “Kayacure DETX” manufactured by Nippon Kayaku Co., Ltd.

Comparative Example 5
About the application | coating of the coating liquid for optically anisotropic layer formation, the optical compensation sheet | seat and the elliptically polarizing plate were produced like Example 1 except apply | coating continuously with a # 3.0 wire bar.

  Table 1 summarizes the results. In the liquid crystal display device of the example, the viewing angle range in which the contrast ratio exceeded 10 was 160 ° or more in all directions. In addition, the color change due to the change in viewing angle was small, and good display characteristics were exhibited. In Comparative Example 1, Δnd of the liquid crystal cell is not appropriate, and in Comparative Examples 4 and 5, the retardation value of the optical compensation sheet or its angle dependency is not appropriate, and a good contrast viewing angle is obtained. Did not come. In Comparative Example 2, Comparative Example 4, and Comparative Example 5, an unnatural color change occurred depending on the viewing angle. It is considered that coloring occurred due to inappropriate retardation values and wavelength characteristics of the liquid crystal cell and the optical compensation sheet. Furthermore, although the moving image characteristics corresponded to the response speed of the liquid crystal cell, in Comparative Example 1 and Comparative Example 3, an afterimage was clearly generated, and the display was uncomfortable.

<Production of liquid crystal display device>
In the liquid crystal display device of Example 1, instead of using “TD-80U” {manufactured by Fuji Photo Film Co., Ltd.} as a polarizing plate protective film, a liquid crystal display device using an antireflection film subjected to the following surface treatment Was made.

Example 4
[Preparation of antireflection film (AF-1)]
(Preparation of sol solution a)
A reactor equipped with a stirrer and a reflux condenser, 120 parts by mass of methyl ethyl ketone, 100 parts of acryloyloxypropyltrimethoxysilane “KBM-5103” (manufactured by Shin-Etsu Chemical Co., Ltd.), diisopropoxyaluminum ethyl acetoacetate “Kelope EP- 12 "{manufactured by Hope Pharmaceutical Co., Ltd.} 3 parts by mass were added and mixed, 30 parts by mass of ion-exchanged water was added and reacted at 60 ° C for 4 hours, and then cooled to room temperature to obtain sol solution a. The mass average molecular weight was 1600, and among the components higher than the oligomer component, the component having a molecular weight of 1000 to 20000 was 100%. Further, from the gas chromatography analysis, the raw material acryloyloxypropyltrimethoxysilane did not remain at all.

{Preparation of hard coat layer coating solution (HCL-1)}
A coating solution having the following composition was prepared, and the coating solution was filtered through a polypropylene filter having a pore diameter of 30 μm to prepare a hard coating layer coating solution (HCL-1).

{Composition of coating liquid for hard coat layer (HCL-1)}
Pentaerythritol triacrylate 50.0 parts by mass “PET-30”: Nippon Kayaku Co., Ltd. photopolymerization initiator 2.0 parts by mass “Irgacure 184”: Ciba Specialty Chemicals Co., Ltd. crosslinked polystyrene particles ( (Refractive index 1.60) 1.7 parts by mass “SX-350H”: 30% by mass toluene dispersion manufactured by Soken Chemical Co., Ltd. Cross-linked acrylic-styrene particles (refractive index 1.55) 13.3 parts by mass “SX-” 350HL ": 30% by weight toluene dispersion manufactured by Soken Chemical Co., Ltd. Fluoro-based surface modifier: FP-132 0.75 parts by mass Acryloyloxypropyltrimethoxysilane 10.0 parts by mass" KBM-5103 ": 38.5 parts by mass of toluene manufactured by Shin-Etsu Chemical Co., Ltd.

[Coating of hard coat layer (HC-1)]
As the support, a triacetyl cellulose film “TD80U” {manufactured by Fuji Photo Film Co., Ltd.} was used. A film in a roll form is unwound and the above hard coat layer coating liquid (HCL-1) is directly applied to a micro gravure roll having a diameter of 180 lines / inch and a gravure pattern having a depth of 40 μm and a doctor blade and a doctor blade. Used, coated at a transfer speed of 30 m / min, dried at 60 ° C. for 150 seconds, and further under a nitrogen purge such that the oxygen concentration becomes 1.0 vol% or less, an “air-cooled metal halide lamp of 160 W / cm” ”{Igraphics Co., Ltd.} is used to cure the coating layer by irradiating with ultraviolet rays having an illuminance of 400 mW / cm ² and an irradiation amount of 250 mJ / cm ² to form a hard coat layer (HC-1), and winding I took it. The rotation speed of the gravure roll was adjusted so that the thickness after curing was 6 μm.

{Preparation of coating solution for low refractive index layer (LLL-1)}
The following composition was mixed to prepare a coating solution.
Thermally crosslinkable fluorine-containing silicone polymer composition 13.0 parts by mass “OPSTAR JTA113”: (solid content 6% by mass), silica fine particle dispersion (average particle size 45 nm) manufactured by JSR Corporation 1.3 parts by mass “MEK -ST-L ": (solid content 30% by mass), manufactured by Nissan Chemical Industries, Ltd. Sol solution a 0.6 parts by mass Methyl ethyl ketone (MEK) 5.0 parts by mass Cyclohexanone 0.6 parts by mass

[Coating of low refractive index layer (LL-1)]
The triacetyl cellulose film coated with the hard coat layer (HC-1) is unwound again, and the coating solution for low refractive index layer (LLL-1) has a gravure pattern with 180 lines / inch and a depth of 40 μm. Nitrogen that is applied with a micro gravure roll having a diameter of 50 mm and a doctor blade under the condition of a conveyance speed of 15 m / min, and further dried at 140 ° C. for 8 minutes and then dried to have an oxygen concentration of 0.1% by volume or less. Using a 240 W / cm “air-cooled metal halide lamp” {manufactured by Eye Graphics Co., Ltd.) under a purge, irradiate ultraviolet rays with an illuminance of 400 mW / cm ² and an irradiation amount of 900 mJ / cm ² so that the thickness becomes 100 nm. The antireflective film (AF-1) was produced by forming and winding the low refractive index layer (LL-1) while adjusting the rotation speed of the gravure roll.

  When the obtained antireflection film (AF-1) was used as a protective film for a polarizing plate, a liquid crystal display device was produced in the same manner as in Example 1. In addition to the good display characteristics in Example 1, the surroundings were reflected even in a bright room. It was confirmed that the display characteristics with good visibility were obtained without any conspicuous dust.

Example 5
[Preparation of antireflection film (AF-2)]
{Preparation of hard coat layer coating solution (HCL-2)}
A coating solution having the following composition was prepared, and the coating solution was filtered through a polypropylene filter having a pore size of 30 μm to prepare a hard coating layer coating solution (HCL-2).

{Composition of coating liquid for hard coat layer (HCL-2)}
Zirconia fine particle-containing hard coat composition 100 parts by mass “Desolite Z7404”: UV curable resin 31 parts by mass “DPHA”: Nippon Kayaku Co., Ltd. acryloyloxypropyltrimethoxysilane 10 parts by mass “KBM-” 5103 ": Shin-Etsu Chemical Co., Ltd. silica particle (1.5 [mu] m) 8.9 parts by mass" KE-P150 ": Nippon Shokubai Co., Ltd. cross-linked PMMA particles (3 [mu] m) 3.4 parts by mass" MXS-300 " : MEK 29 parts by mass Miso Isobutyl Ketone (MIBK) 13 parts by mass

[Coating of hard coat layer (HC-2)]
As the support, a triacetyl cellulose film “TD80U” {manufactured by Fuji Photo Film Co., Ltd.} was used. A film in a roll form is unwound, and the above hard coat layer coating liquid (HCL-2) is directly applied to a microgravure roll having a diameter of 135 lines / inch and a gravure pattern of 60 μm in depth and a doctor blade. The coating was carried out at a transfer speed of 10 m / min, dried at 60 ° C. for 150 seconds, and then “air-cooled metal halide lamp” of 160 W / cm under a nitrogen purge so that the oxygen concentration was 1.0% by volume or less. Using {I-Graphics Co., Ltd.}, the coating layer is cured by irradiating ultraviolet rays with an illuminance of 400 mW / cm ² and an irradiation amount of 250 mJ / cm ² to form a hard coat layer (HC-2). I took it. After curing, the gravure roll rotation speed was adjusted so that the thickness of the hard coat layer (HC-2) was 3.6 μm.

{Preparation of coating solution for low refractive index layer (LLL-2)}
The following composition was mixed to prepare a coating solution.
Thermally crosslinkable fluorine-containing polymer 100.0 parts by mass “JN7228A” (solid content 6% by mass), silica fine particle dispersion (average particle size 15 nm) manufactured by JSR Corporation 4.3 parts by mass “MEK-ST”: (solid 30 mass%), manufactured by Nissan Chemical Industries, Ltd. Silica fine particle dispersion (average particle size 45 nm) 5.1 parts by mass “MEK-ST-L”: (solid content 30 mass%), Nissan Chemical Industries, Ltd. Manufactured sol solution a 2.2 parts by mass MEK 15.0 parts by mass cyclohexanone 3.6 parts by mass

[Coating of low refractive index layer (LL-2)]
The triacetyl cellulose film coated up to the hard coat layer (HC-2) was unwound again, and the low refractive index layer coating solution (LLL-2) was gravure with 180 lines / inch and a depth of 40 μm. Using a micro gravure roll with a diameter of 50 mm and a doctor blade having a pattern, the coating was performed at a conveyance speed of 15 m / min, pre-dried at 120 ° C. for 150 seconds, and further post-dried at 140 ° C. for 8 minutes and then oxygen. Using a 240 W / cm “air-cooled metal halide lamp” {manufactured by Eye Graphics Co., Ltd.) under a nitrogen purge such that the concentration becomes 0.1% by volume or less, an illuminance of 400 mW / cm ² and an irradiation amount of 900 mJ / cm ² Is applied to form a low refractive index layer (LL-2) while adjusting the rotation speed of the gravure roll so as to have a thickness of 100 nm. A stop film (AF-2) was produced.

  Using the obtained antireflection film (AF-2) as a protective film for the polarizing plate, a liquid crystal display device was produced in the same manner as in Example 1. In addition to the good display characteristics in Example 1, the gradation characteristics were further excellent. In addition, it was confirmed that even in a bright room, the surrounding reflections were not noticeable and display characteristics with good visibility were obtained.

Example 6
[Preparation of antireflection film (AF-3)]
{Preparation of hard coat layer coating solution (HCL-3)}
750.0 parts by mass of trimethylolpropane triacrylate “TMPTA” {manufactured by Nippon Kayaku Co., Ltd.}, 270.0 parts by mass of poly (glycidyl methacrylate) having a mass average molecular weight of 15000, 730.0 parts by mass of methyl ethyl ketone, 500. 0 parts by mass and 50.0 parts by mass of a photopolymerization initiator “Irgacure 184” {manufactured by Ciba Specialty Chemicals)}, 25 parts by mass of (t-butylphenyl) iodonium hexafluorophosphate were added and stirred. . The hard coat layer coating solution (HCL-3) was filtered through a polypropylene filter having a pore size of 0.4 μm.

[Coating of hard coat layer (HC-3)]
As a support, a triacetyl cellulose film (TD80U, manufactured by Fuji Photo Film Co., Ltd.) is unwound in a roll form and directly has the above-mentioned hard coat layer coating solution having a gravure pattern of 180 lines / inch and a depth of 40 μm. Using a micro gravure roll with a diameter of 50 mm and a doctor blade, it was applied at a transfer speed of 30 m / min, dried at 60 ° C. for 150 seconds, and then purged with nitrogen so that the oxygen concentration was 1.0% by volume or less. Using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.), the coating layer is cured by irradiating ultraviolet rays with an illuminance of 400 mW / cm ² and an irradiation amount of 300 mJ / cm ^2. -3) was formed and wound up. The rotational speed of the gravure roll was adjusted so that the thickness after curing was 8 μm.

{Preparation of Titanium Dioxide Fine Particle Dispersion (TL-1)}
As the titanium dioxide fine particles, titanium dioxide fine particles “MPT-129C” containing cobalt and surface-treated with aluminum hydroxide and zirconium hydroxide, manufactured by Ishihara Sangyo Co., Ltd., TiO ₂ : Co ₃ O ₄ : Al ₂ O ₃ : ZrO ₂ = 90.5: 3.0: 4.0: 0.5 mass ratio} was used.

  The following dispersant (41.1 parts by mass) and cyclohexanone (701.8 parts by mass) were added to 257.1 parts by mass of the particles and dispersed by dynomill to prepare a titanium dioxide dispersion having a mass average diameter of 70 nm.

{Preparation of Medium Refractive Index Layer Coating Solution (MLL-1)}
A mixture "DPHA" of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate {manufactured by Nippon Kayaku Co., Ltd.} 68.0 parts by mass in 99.1 parts by mass of the above titanium dioxide dispersion (TL-1), light Polymerization initiator “Irgacure 907” {manufactured by Ciba Specialty Chemicals Co., Ltd.} 3.6 parts by mass, photosensitizer “Kayacure DETX” {manufactured by Nippon Kayaku Co., Ltd.} 1.2 parts by mass, methyl ethyl ketone 279. 6 parts by mass and 1049.0 parts by mass of cyclohexanone were added and stirred. After sufficiently stirring, the mixture was filtered through a polypropylene filter having a pore size of 0.4 μm.

[Coating of medium refractive index layer (ML-1)]
The triacetyl cellulose film “TD80UF” (manufactured by Fuji Photo Film Co., Ltd.) coated with the hard coat layer (HC-3) was unwound again, and the medium refractive index layer coating solution (MLL-1) was The coating was performed using a micro gravure roll having a diameter of 50 mm having a gravure pattern of 180 lines / inch and a depth of 40 μm and a doctor blade. Drying conditions are 90 ° C. and 30 seconds, and UV curing conditions are “air-cooled metal halide lamp” of 180 W / cm while purging with nitrogen so that the oxygen concentration is 1.0 volume% or less {eye graphics Co., Ltd. Was used, and the irradiation dose was 400 mW / cm ² and the irradiation dose was 400 mJ / cm ² . An intermediate refractive index layer (ML-1) was formed and wound up while adjusting the rotation speed of the gravure roll so that the thickness after application was 67 nm. The medium refractive index layer (ML-1) after curing had a refractive index of 1.630.

{Preparation of coating solution for high refractive index layer (HLL-1))
460.0 parts by mass of the above titanium dioxide dispersion (TL-1), 40.0 parts by mass of a mixture “DPHA” {manufactured by Nippon Kayaku Co., Ltd.} of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, light Polymerization initiator “Irgacure 907” {manufactured by Ciba Specialty Chemicals Co., Ltd.} 3.3 parts by mass, photosensitizer “Kayacure DETX” {manufactured by Nippon Kayaku Co., Ltd.} 1.1 parts by mass, methyl ethyl ketone 526. 2 parts by mass and 459.6 parts by mass of cyclohexanone were added and stirred. It filtered with the polypropylene filter with the hole diameter of 0.4 micrometer.

[Coating of high refractive index layer (HL-1)]
The triacetyl cellulose film “TD80UF” (manufactured by Fuji Photo Film Co., Ltd.) coated up to the middle refractive index layer (ML-1) was unwound again, and the coating solution for high refractive index layer (HLL-1) was The coating was performed using a micro gravure roll having a diameter of 50 mm having a gravure pattern of several 180 lines / inch and a depth of 40 μm and a doctor blade. Drying conditions are 90 ° C. and 30 seconds, and UV curing conditions are “air-cooled metal halide lamp” of 240 W / cm while purging with nitrogen so that the oxygen concentration is 1.0% by volume or less {eye graphics Co., Ltd. Was used, and the irradiation dose was 600 mW / cm ² and the irradiation dose was 400 mJ / cm ² . A high refractive index layer (HL-1) was formed and wound while adjusting the rotation speed of the gravure roll so that the thickness after coating was 107 nm. The high refractive index layer (HL-1) after curing had a refractive index of 1.905.

{Preparation of coating solution for low refractive index layer (LLL-3)}
30 parts by mass of tetramethoxysilane and 240 parts by mass of methanol are put into a four-necked reaction flask and stirred while keeping the liquid temperature at 30 ° C. Then, an aqueous solution in which 2 parts by mass of nitric acid is added to 6 parts by mass of water is added. The mixture was stirred at 30 ° C. for 5 hours to obtain a siloxane oligomer alcohol solution (solution A). The relative molecular weight in terms of ethylene glycol / polyethylene oxide by GPC of the siloxane oligomer was 950.

Separately, 300 parts by mass of methanol was placed in a four-necked reaction flask, and then 30 parts by mass of oxalic acid was mixed with stirring. While heating and refluxing this solution, 30 parts by mass of tetramethoxysilane and 8 parts by mass of tridecafluorooctyltrimethoxysilane were added dropwise, heated under reflux for 5 hours, and then cooled to obtain a fluoroalkyl structure and a polysiloxane structure. A solution (solution B) of a fluorine compound having

  30 parts by mass of solution A and 100 parts by mass of solution B are mixed with stirring, diluted with butyl acetate so that the solid content concentration in the mixed coating solution becomes 1% by mass, and coating solution for low refractive index layer (LLL-3) )

[Coating of low refractive index layer (LL-3)]
The slot die has an upstream lip land length I _UP of 0.5 mm, a downstream lip land length I _LO of 50 μm, a slot opening length of 150 μm in the web running direction, and a slot length of 50 mm. used. The gap between the upstream lip land 18a and the web W is 50 μm longer than the gap between the downstream lip land 18b and the web W (hereinafter referred to as an overbite length of 50 μm), and the gap between the downstream lip land 18b and the web W _GL was set to 50 μm. Further, the gap G _B between the gap G _S, and the back plate 40a and the web W between the side plate 40b and the web W in the vacuum chamber 40 were both 200 [mu] m.

The triacetyl cellulose film coated up to the high refractive index layer (HL-1) was unwound again, and the low refractive index layer coating solution (LLL-3) was applied at a coating speed of 25 m / min by the die coating method. After drying at 120 ° C. for 150 seconds and further drying at 140 ° C. for 8 minutes, a 240 W / cm “air-cooled metal halide lamp” {eye graphics under a nitrogen purge such that the oxygen concentration is 0.1% by volume or less. Is used to irradiate ultraviolet rays having an illuminance of 400 mW / cm ² and an irradiation amount of 900 mJ / cm ² to form a low refractive index layer (LL-3) having a thickness of 100 nm, which is wound to prevent reflection. A film (AF-3) was produced.

  Using the obtained antireflection film (AF-3) as a protective film for the polarizing plate, a liquid crystal display device of Example 1 was produced. In addition to the good display characteristics of Example 1, the gradation characteristics were excellent, and It was confirmed that the surrounding reflections were not noticeable even in the bright room and display characteristics with good visibility were obtained.

It is a schematic diagram of the polarizing plate at the time of using the optical compensation sheet used for this invention, and the optical compensation sheet used for this invention as a protective film of a polarizing plate. It is the figure which showed the slot die coater when implementing this invention. It is the schematic of the application | coating of an optically anisotropic layer when implementing this invention, and a drying process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Protective film 2 ... Polarizing film 3 ... Optical compensation sheet 11 ... Polymer support film 12 ... Optical anisotropic layer 21 ... Slot die 23 ... Slot 24 ... Downstream lip land 25 ... Upstream lip land 31 ... Web 32 ... Condenser plate 33 ... Dryer 34 ... Heating zone

Claims (9)

A liquid crystal display device comprising a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and at least one optical compensation sheet disposed between the liquid crystal cell and the polarizing plate,
The liquid crystal cell has a Δnd value of 370 to 440 nm, a twist angle of 88 ° to 92 °, twist nematic alignment, and a response time from white display to black display of 12 msec or less.
The optical compensation sheet satisfies the following mathematical formulas (1) and (2).
Formula (1): 0.9 ≦ {Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ } / {Δnd ₍₄₅₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.0.
Formula (2): 1.0 ≦ {Rth ₍₆₁₀₎ / Rth ₍₅₅₀₎ } / {Δnd ₍₆₁₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.10.
[Δnd is the product of the birefringence Δn of the liquid crystal material in the liquid crystal cell and the liquid crystal cell gap d, and Δnd ₍₄₅₀₎ , Δnd _(550), and Δnd ₍₆₁₀₎ are the birefringence at wavelengths of 450 nm, 550 nm, and 610 nm, respectively. Rth ₍₄₅₀₎ , Rth _(550), and Rth ₍₆₁₀₎ represent retardation values (Rth) in the thickness direction of the optical compensation sheet at wavelengths of 450 nm, 550 nm, and 610 nm, respectively. . ] A liquid crystal display device comprising a liquid crystal cell, two polarizing plates disposed outside the liquid crystal cell, and at least one optical compensation sheet disposed between the liquid crystal cell and the polarizing plate,
The liquid crystal cell has a Δnd value of 370 to 440 nm, a twist angle of 88 ° to 92 °, twist nematic alignment, and a response time from white display to black display of 12 msec or less.
The optical compensation sheet has at least one optically anisotropic layer satisfying the following mathematical formulas (3) and (4).
Formula (3): 0.95 ≦ {Rth ¹ ₍₄₅₀₎ / Rth ¹ ₍₅₅₀₎ } / {Δnd ₍₄₅₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.05.
Formula (4): 0.95 ≦ {Rth ¹ ₍₆₁₀₎ / Rth ¹ ₍₅₅₀₎ } / {Δnd ₍₆₁₀₎ / Δnd ₍₅₅₀₎ } ≦ 1.05.
[Δnd is the product of the birefringence Δn of the liquid crystal material in the liquid crystal cell and the liquid crystal cell gap d, and Δnd ₍₄₅₀₎ , Δnd _(550), and Δnd ₍₆₁₀₎ are the birefringence at wavelengths of 450 nm, 550 nm, and 610 nm, respectively. Rth ¹ ₍₄₅₀₎ , Rth ¹ ₍₅₅₀₎ and Rth ¹ ₍₆₁₀₎ are retardation values in the thickness direction of the optically anisotropic layer at wavelengths of 450 nm, 550 nm and 610 nm, respectively. Represents (Rth). ] 3. The liquid crystal display device according to claim 1, wherein the wavelength dispersion Δn ₍₄₅₀₎ / Δn ₍₅₅₀₎ of the liquid crystal molecules in the liquid crystal cell is 1.04 or more.   4. The liquid crystal display device according to claim 2, wherein the optically anisotropic layer is formed by fixing the orientation of the liquid crystalline compound.   The liquid crystal display device according to claim 1, wherein the optical compensation sheet contains a polymer support film having birefringence and an optically anisotropic layer in which the orientation of the liquid crystal compound is fixed. Retardation value of optical anisotropic layer measured from normal direction of optically anisotropic layer: Re is 40 nm or more,
And the retardation value of the optically anisotropic layer measured from the direction inclined by + 40 ° from the normal line of the optically anisotropic layer in a plane perpendicular to the optically anisotropic layer including the orientation direction: Re ⁽⁺⁴⁰⁾ , Re ratio: Re ⁽⁺⁴⁰⁾ / Re is less than 2.0,
Further, the retardation value of the optically anisotropic layer measured from the direction inclined by −40 ° from the normal line of the optically anisotropic layer in the plane perpendicular to the optically anisotropic layer including the orientation direction: Re ⁽⁻⁴⁰⁾ And the ratio of Re to: Re ⁽⁻⁴⁰⁾ / Re is 0.40 or more. The liquid crystal display device according to claim 2.   The liquid crystal display device according to claim 4, wherein the liquid crystal compound used in the optically anisotropic layer is a discotic liquid crystal compound.   The liquid crystal display device according to claim 5, wherein the polymer support film is a cellulose acylate film.   The liquid crystal display device according to any one of claims 1 to 8, wherein the optical compensation sheet also serves as a protective film for the polarizing plate by being directly bonded to the polarizing film of the polarizing plate.

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