JP2006267613A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device such that variation in color hues with a visual field varying in a vertical direction is reduced. <P>SOLUTION: The liquid crystal display device has TN mode liquid crystal cells (5a, 6, and 6b), polarizing films (2a and 2b) arranged on both the sides of the liquid crystal cells, and an optical compensating film arranged between the liquid crystal cell and the upper and lower polarizing films and is characterized in that the optical compensating film comprises 1st optical anisotropic media (3a and 3b) and 2nd optical anisotropic media (4a and 4b) and the retardation satisfies desired relation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device having an optical compensation film made of an optically anisotropic medium.

  A liquid crystal display device generally includes a liquid crystal cell, a polarizing element, and an optical compensation film (retardation plate). In a transmissive liquid crystal display device, usually, two polarizing elements are arranged on both sides of a liquid crystal cell, and one or two optical compensation films are arranged between the liquid crystal cell and the polarizing element. In a reflective liquid crystal display device, a reflector, a liquid crystal cell, a single optical compensation film, and a single polarizing element are usually arranged in this order. A liquid crystal cell usually comprises a rod-like liquid crystalline molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystalline molecule. The liquid crystal cell is different in the alignment state of rod-like liquid crystal molecules. As for the transmissive type, TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory N) (OCB). Super Twisted Nematic), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and reflection types are TN, HAN (Hybrid Aligned NeH), .

  Optical compensation films are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As the optical compensation film, an optical compensation film having an optically anisotropic layer formed from a discotic compound or a liquid crystalline molecule on a transparent support, such as a stretched birefringent polymer film, is generally used. The optical properties of the optical compensation film are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. Various optical compensation films corresponding to various display modes have been proposed.

Regarding the TN liquid crystal display mode, a compensation film in which a discotic compound is immobilized in a hybrid alignment state on a transparent support has been put to practical use as an optical compensation film that expands a high contrast viewing angle range (Patent Literature). 1). In this method, since the nematic liquid crystal cell composed of rod-shaped liquid crystals is compensated by the discotic compound, it is possible to compensate for incident light from an oblique direction, and the display viewing angle can be greatly expanded. is there. In this case, as shown in FIG. 5, for the TN liquid crystal cell 51 in which the rod-like molecules 52 are twisted nematically oriented, the compensation films 54a and 54b made of the discotic compound 53 are arranged on the display surface side and the backlight 55. Place on the back side. The azimuth direction in which the discotic compound is oriented is the vertical and horizontal directions in the normally white mode TN liquid crystal display device by effectively compensating for the black display state to which voltage is applied. It is designed to reduce the black transmittance in the direction and enlarge the viewing angle.
Japanese Patent No. 2587398

Although the viewing angle region (contrast viewing angle) capable of maintaining a high contrast of the TN liquid crystal display has been expanded by the method disclosed in Patent Document 1, the phenomenon that the color changes depending on the viewing angle direction (color variation) is solved. Was not. This is because it is difficult to achieve both the expansion of the contrast viewing angle and the color variation simply from the viewpoint of the design and material properties of the optical compensation film. Nowadays, as TN mode liquid crystal display devices are more widely used than notebook personal computers, monitors, TVs, etc., realization of wider contrast viewing angle and higher quality color reproducibility are strongly desired for liquid crystal display devices. Yes. In view of such a situation, an object of the present invention is to realize improvement (reduction) of color variation with respect to a vertical visual field change particularly in black display, in order to further expand the use area of the TN liquid crystal mode. .
As for the color variation, in the CIE1976UCS chromaticity diagram, the change from yellow to blue, the variation (Δu'v ') on the chromaticity diagram between the maximum v' value and the minimum v 'value is within about 0.12. It is hoped that.

  As a result of investigating the tendency of an image in which the color fluctuation is a significant problem, it has been found that the color purity of black and white is particularly important, and color misregistration can be easily identified. It is also known to be sensitive to color balance due to human skin color. When these facts and the image characteristics of the TN liquid crystal mode are collated, when the display image is observed from different directions, the change in the color of black particularly with respect to the angle is important, thereby reducing the display quality. This has become clear through various experiments. In order to further expand the application of the TN liquid crystal display device against the background of such display quality problems, the present invention provides a liquid crystal display device in which the color variation with respect to the viewing angle in the vertical direction is improved (reduced). Let it be an issue.

Means for solving the above-mentioned problems are as follows.
[1] A TN mode liquid crystal cell, a polarizing film disposed on both sides of the liquid crystal cell, and an optical compensation film disposed between the liquid crystal cell and the upper and lower polarizing films, respectively, and the optical compensation A liquid crystal display device in which the film is composed of a first optically anisotropic medium and a second optically anisotropic medium, and simultaneously satisfies the following formulas (1) to (6);
(1) 1.06 ≦ Δnd (450) / 2 × (P_Rth (450) + D_Rth (450)) ≦ 1.18
(2) 1.04 ≦ Δnd (550) / 2 × (P_Rth (550) + D_Rth (550)) ≦ 1.14
(3) 1.02 ≦ Δnd (610) / 2 × (P_Rth (610) + D_Rth (610)) ≦ 1.12
(4) 0.28 ≦ 2 × (P_Re (450) + D_Re (450)) / (450 × 10 ⁻⁹ ) ≦ 0.30
(5) 0.21 ≦ 2 × (P_Re (550) + D_Re (550)) / (550 × 10 ⁻⁹ ) ≦ 0.23
(6) 0.19 ≦ 2 × (P_Re (610) + D_Re (610)) / (610 × 10 ⁻⁹ ) ≦ 0.21
Where Δnd is the product of the rod-like liquid crystal birefringence Δn in the liquid crystal cell and the thickness d of the liquid crystal layer; P_Rth (λ) and P_Re (λ) are respectively the first optical anisotropic medium at the wavelength λ Rth and Re; D_Rth (λ) and D_Re (λ) mean Rth and Re of the second optically anisotropic medium at the wavelength λ, respectively.

[2] The liquid crystal display device according to claim 1, wherein the optical compensation film further satisfies the following formulas (7) to (12):
(7) Δnd (450) / 2 × (P_Rth (450) + D_Rth (450)) = 1.12
(8) Δnd (550) / 2 × (P_Rth (550) + D_Rth (550)) = 1.09
(9) Δnd (610) / 2 × (P_Rth (610) + D_Rth (610)) = 1.07
(10) 2 × (P_Re (450) + D_Re (450)) / (450 × 10 ⁻⁹ ) = 0.29
(11) 2 × (P_Re (550) + D_Re (550)) / (550 × 10 ⁻⁹ ) = 0.22
(12) 2 × (P_Re (610) + D_Re (610)) / (610 × 10 ⁻⁹ ) = 0.20
[3] The liquid crystal according to claim 1 or 2, wherein one of the first and second optically anisotropic media is a transparent support, and the other is an optically anisotropic layer containing a discotic compound. Display device.

  In the present specification, the term “optically anisotropic medium” is used for any medium exhibiting optical anisotropy regardless of the material. For example, any of a medium exhibiting optical anisotropy expressed by alignment of liquid crystal molecules, a polymer medium expressed by aligning a polymer by stretching treatment, and the like are used. In this specification, “polarizing film” and “polarizing plate” are distinguished from each other, and “polarizing plate” is a laminate having a transparent protective film for protecting the polarizing film on at least one side of the “polarizing film”. Means.

  In the present specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is a light having a wavelength of λ nm from the direction inclined by + 40 ° with respect to the normal direction of the film, using Re (λ) and the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis). And a retardation value measured by making light of wavelength λ nm 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 a total of three directions, the assumed value of the average refractive index, and the input film thickness value. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness.

  By adopting a TN liquid crystal display device that simultaneously satisfies the expressions (1) to (6) disclosed in the present invention, the black color from the top and bottom direction as compared with a conventional TN liquid crystal display device using an optical compensation film. Taste fluctuation can be suppressed and a display device that realizes good color reproduction can be obtained.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
FIG. 1 is a schematic diagram of an embodiment in which the present invention is applied to a transmissive TN liquid crystal display device. The liquid crystal display device shown in FIG. 1 includes a liquid crystal cell composed of upper and lower substrates 5b and 5a and a liquid crystal layer 6 sandwiched between the upper and lower substrates, and upper and lower polarizing films 2b and 2a disposed so as to sandwich the liquid crystal cell. Further, between the upper polarizing film 2b and the liquid crystal cell, an optically anisotropic layer 4b containing a transparent support 3b as a first optically anisotropic medium and a discotic compound as a second optically anisotropic medium. An optical compensation film comprising: a transparent support 3a as a first optical anisotropic medium and a discotic compound as a second optical anisotropic medium between the lower polarizing film 2a and the liquid crystal cell. An optical compensation film made of the optically anisotropic layer 4a is disposed. Further, transparent protective films 1b and 1a are disposed on the surfaces of the upper and lower polarizing films 2b and 2a, respectively.

  The absorption axes of the polarizing films 2a and 2b and the rubbing direction for controlling the orientation of the discotic compound contained in the optically anisotropic layers 4a and 4b are parallel when viewed from the front of the display device. The absorption axes of the polarizing films 2a and 2b and the rubbing direction for controlling the alignment of the liquid crystal molecules in the liquid crystal layer 6 may be parallel to form an O-mode structure, or the transmission axes of the polarizing films 2a and 2b, The liquid crystal layer 6 may be in the E mode in parallel with the rubbing direction for controlling the alignment of the liquid crystal molecules.

  Since the optical compensation films (3a and 4a and 3b and 4b in FIG. 2) are used together with the polarizing film (2a and 2b in FIG. 1), they are laminated with the transparent protective film and the polarizing film in advance. When an elliptically polarizing plate is used, it is efficient and useful in use.

  The upper and lower substrates 5b and 5a are made of, for example, a glass substrate, a TFT is formed on one side, and a color filter is formed on the other side. The liquid crystal cell is, for example, a display pixel made of a transparent electrode, an alignment film is applied on a substrate having a display size, and after rubbing, a micropolymer having a desired diameter is dispersed as a spacer for determining the thickness d of the liquid crystal layer. Then, it can be produced by injecting a rod-like liquid crystal having a desired birefringence Δn.

Next, the principle of optical compensation of the liquid crystal display device of FIG. 1 will be described with reference to FIG.
In order to optically compensate the TN liquid crystal display device, the liquid crystal state of black display is usually compensated by an optical compensation film. The optical compensation relationship at this time will be described using the Poincare sphere shown in FIG. The propagation of light here is when viewed from 60 ° above the screen of the liquid crystal display device in the black display state. The symbol on the Poincare sphere and the symbol in FIG. 1 have a one-to-one correspondence, and the polarization state of light that has passed through the polarizing film 2a, the lower optical compensation films 3a and 4a, the liquid crystal layer 6, and the upper optical compensation films 4b and 3b. The change is indicated by the position on the Poincare sphere. In FIG. 2, the S2 axis is an axis penetrating vertically from the top to the bottom of the drawing, and FIG. 2 is a view of the Poincare sphere viewed from the positive direction of the S2 axis. Also, since FIG. 2 is shown in a plan view, the displacement of the points before and after the change of the polarization state is indicated by the straight arrows in the figure. The change in the polarization state due to the passage is expressed by rotating a specific angle on a Poincare sphere around a specific axis determined according to each optical characteristic.

First, paying attention to the change in the longitude direction on the Poincare sphere, the transparent support 3a which is the first optical anisotropic medium on the incident side and the discotic compound layer 4a which is the second optical anisotropic medium are arranged on the Poincare sphere. The polarized light that has moved to the upper half (northern hemisphere) moves to the lower half (southern hemisphere) by the liquid crystal layer 6 and follows a trajectory returning to the horizontal plane (up to the equator) by the discotic compound layer 4b on the emission side and the transparent support 3b. .
Focusing on the change in the latitude direction on the Poincare sphere, the polarized light moved in the negative direction of S1 by the transparent support 3a on the incident side and the discotic compound layer 4a is moved again in the positive direction of S1 by the liquid crystal layer 6. Then, the path of returning to the S1 negative side and the equator is traced by the discotic compound layer 4b on the emission side and the transparent support 3b.

  In this way, the compensation relationship between the two layers of the first optical anisotropic medium and the second optical anisotropic medium and one TN liquid crystal layer is formed. When the change is traced, when the main wavelengths (BGR 3 colors of the color filter in the liquid crystal cell) constituting the color tone reach the point where the final extinction points are 450 nm, 550 nm, and 610 nm on the Poincare sphere. A perfect black will be realized.

From this point of view, if the polarization changes on the Poincare sphere due to Re and Rth of three wavelengths are arranged dimensionlessly as Re / λ and Rth / λ, ideally the longitudinal direction is the structure of FIG. For example, when the sum of Rth / λ of the two layers of the first optically anisotropic medium and the second layer of the second optically anisotropic medium coincides with Δnd / λ of the liquid crystal layer for all three wavelengths, the equator on the Poincare sphere The changed polarization will return to the equator. With respect to the latitudinal direction, a completely black state can be created when the polarized light from the point of the transmission side polarizing plate transmission axis reaches the point of the output side polarizing plate absorption axis. However, it is considered that the locus on the Poincare sphere having the BGR 3 wavelength does not coincide from the following two points.
1) Even when an ON voltage is applied to a general normally white mode 0 mode TN liquid crystal, the rod-shaped liquid crystals are not completely standing, but are tilted near the substrate and only near the center of the liquid crystal layer. Standing perfectly. Therefore, the Rth value of the compensation layer needs to be smaller than the value of Δnd. Since it is not completely standing, even a slight Re component remains even in the ON state.
2) Since the Re and Rth at the three wavelengths of the liquid crystal layer and the optical compensation film are different, different trajectories are passed on the Poincare sphere. Therefore, in most cases, the final destination will be different.

  Considering the above two causes, it is considered that the dimensionless Rth (λ) / λ of the three wavelengths is necessarily smaller by a certain amount than Δnd / λ of the liquid crystal layer. On the other hand, with respect to Re / λ, if the three wavelengths are completely on the equator and can be matched on the absorption axis of the output side polarizing plate, the black state can be realized with the same value. When the three wavelengths are the same distance from the point on the emission side polarizing plate absorption axis on the Poincare sphere, the same amount of light leaks from the emission side polarizing plate for all three wavelengths, and achromatic can be realized. This polarization state is indicated by the Poincare sphere in FIG. When the point indicating the polarization state of the three wavelengths is equidistant from the point on the absorption axis of the output-side polarizing plate, the same amount of light leaks at all three wavelengths, but the color is realized from black to gray. It will be. In this case, equidistant from a point on the absorption axis (on a circle with a certain radius) means that the three wavelengths do not coincide with each other in the Rth component in the longitude direction and have a certain ratio relationship. At the same time, there will be a specific proportion relationship that also includes Re components of three wavelengths.

Summarizing the above changes in polarization, all the Rth / λ of the compensation layer are smaller than Δnd of the liquid crystal layer, and Re / λ and Rth / λ need to have a certain special ratio in order to make the color black to gray. It is thought that there is. Therefore, the present inventor creates an optical model of the first optical anisotropic medium and the second optical anisotropic medium constituting the optical compensation film using commercially available simulation software for a liquid crystal display device, and generates a BGR 3 wavelength. Various Re and Rth values were calculated, and a special ratio of three wavelengths when the color tone was close to black was determined. This completed the present invention. The dimensions were made non-dimensional and the ratios thereof were calculated by comparing the quotients obtained by dividing Δnd of the liquid crystal layer and Re (λ) and Rth (λ) of the first and second optically anisotropic media by the wavelength λ.
As a result, it was found that when the relationships of the following formulas (7) to (12) are satisfied, a color balance can be achieved and black to gray can be realized.
(7) Δnd (450) / 2 × (P_Rth (450) + D_Rth (450)) = 1.12
(8) Δnd (550) / 2 × (P_Rth (550) + D_Rth (550)) = 1.09
(9) Δnd (610) / 2 × (P_Rth (610) + D_Rth (610)) = 1.07
(10) 2 × (P_Re (450) + D_Re (450)) / (450 × 10 ⁻⁹ ) = 0.29
(11) 2 × (P_Re (550) + D_Re (550)) / (550 × 10 ⁻⁹ ) = 0.22
(12) 2 × (P_Re (610) + D_Re (610)) / (610 × 10 ⁻⁹ ) = 0.20
Where Δnd is the product of the rod-like liquid crystal birefringence Δn in the liquid crystal cell and the thickness d of the liquid crystal layer; P_Rth (λ) and P_Re (λ) are each the first optical anisotropic at the wavelength λ D_Rth (λ) and D_Re (λ) mean Rth and Re of the second optically anisotropic medium at wavelength λ, respectively.

Centering on the above formulas (7) to (12), the target CIE 1976 UCS chromaticity diagram is within the target range at a distance Δu′v ′ on the chromaticity diagram that is the maximum v ′ and the minimum v ′. As a result of calculation of the necessary conditions shown in Table 1 below, when the following formulas (1) to (6) are satisfied at the same time, the knowledge that Δu′v ′ falls within the target range and the color variation can be reduced is obtained. It was.
(1) 1.06 ≦ Δnd (450) / 2 × (P_Rth (450) + D_Rth (450)) ≦ 1.18
(2) 1.04 ≦ Δnd (550) / 2 × (P_Rth (550) + D_Rth (550)) ≦ 1.14
(3) 1.02 ≦ Δnd (610) / 2 × (P_Rth (610) + D_Rth (610)) ≦ 1.12
(4) 0.28 ≦ 2 × (P_Re (450) + D_Re (450)) / (450 × 10 ⁻⁹ ) ≦ 0.30
(5) 0.21 ≦ 2 × (P_Re (550) + D_Re (550)) / (550 × 10 ⁻⁹ ) ≦ 0.23
(6) 0.19 ≦ 2 × (P_Re (610) + D_Re (610)) / (610 × 10 ⁻⁹ ) ≦ 0.21
Where Δnd is the product of the rod-like liquid crystal birefringence Δn in the liquid crystal cell and the thickness d of the liquid crystal layer; P_Rth (λ) and P_Re (λ) are respectively the first optical anisotropic medium at the wavelength λ Rth and Re; D_Rth (λ) and D_Re (λ) mean Rth and Re of the second optically anisotropic medium at the wavelength λ, respectively.

  FIG. 4 is a UCS chromaticity diagram defined in 1976 by CIE (Commission Internationale de l'Eclairage). On this chromaticity diagram, a vertical direction of a liquid crystal display device using a wide viewing angle polarizing plate (LPT-HL56-12, manufactured by Sanritz Co., Ltd.) using a conventional optical compensation film (manufactured by Fuji Photo Film Co., Ltd.). The color of the black display (up from 80 ° to 80 ° from the display normal) is from (u ′, v ′) = (0.172, 0.393) to (0.267, 0.514). A variation of Δu′v ′ = 0.15 occurred as a distance on the degree diagram. On the other hand, in the liquid crystal display device of the present invention that satisfies the expressions (1) to (6) at the same time, the color variation in the vertical direction is suppressed to Δu′v ′ = 0.06 to 0.07 at the maximum. It is done.

Hereinafter, the material and production method of the optical compensation film used in the liquid crystal display device of the present invention will be described in detail.
Examples of the optical compensation film used in the liquid crystal display device of the present invention include an optical anisotropy medium composed of a stretched polymer film, an optical anisotropy layer, and an optical anisotropy expressed by the orientation of the discotic compound. And an optically anisotropic medium.
[First optical anisotropic medium]
The first optically anisotropic medium is preferably a transparent polymer film that serves as a support for the second optically anisotropic medium.
The support preferably has a light transmittance (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 (eg, cellulose mono-, di-, and triacylates), norbornene-based polymers, and polymethyl methacrylate. Commercially available polymers (for norbornene polymers, Arton and Zeonex (both are trade names)) may be used. 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 first optically anisotropic medium.

[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, particularly preferred cellulose as described above cannot be used as it is, and linter, kenaf and pulp are purified and used.

  In the present invention, cellulose acylate is a carboxylic acid ester 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, etc. 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 (issued March 15, 2001, Japan Institute of Invention) p. 9 is described in detail.

The cellulose acylate preferably used in the present invention preferably has a degree of substitution with a hydroxyl group of cellulose satisfying the following mathematical formulas (1) and (2).
Formula (1): 2.3 ≦ SA ′ + SB ′ ≦ 3.0
Formula (2): 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.

Furthermore, it is preferable that the following mathematical formula (3) is satisfied at the same time.
Formula (3): 0 ≦ SB ”≦ 1.2
Here, SB ″ represents an acyl group having 3 or 4 carbon atoms replacing a hydrogen atom of a hydroxyl group of cellulose.

  Further, SB ″ is preferably 28% or more of the substituent at the 6-position hydroxyl group, more preferably 30% or more is the substituent at the 6-position hydroxyl group, more preferably 31% or more, and particularly preferably 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 the fatty acid bound to the hydroxyl group 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.

  The cellulose acylate film is preferably made of a cellulose acylate in which the polymer component constituting the film substantially satisfies the above mathematical formulas (1), (2) and (3). “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 (DP) 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 a polymer film is used as an optical compensation film as the first optical anisotropic medium, the polymer film preferably has a desired retardation value. The retardation value (Re (λ), Rth (λ)) of the polymer film depends on Δnd of the liquid crystal cell in which the optical compensation film is used and the optical properties of the second optically anisotropic medium described later. The range satisfies (1) to (6).

  In order to adjust the retardation of the polymer film, a method of applying an external force such as stretching is generally used, but a retardation increasing agent for adjusting the optical anisotropy is optionally added. In order to adjust the retardation of the cellulose acylate film, an aromatic compound having at least two aromatic rings is preferably used as a 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 thereof include compounds described in European Patent 0911656A2, JP-A Nos. 2000-1111914 and 2000-275434.

  Additives described above to be added to the polymer film or additives that can be added according to various purposes (for example, UV inhibitors, release agents, antistatic agents, deterioration inhibitors (eg, antioxidants, peroxide decomposers) , Radical inhibitors, metal deactivators, acid scavengers, amines, infrared absorbers, etc.) may be solid or oily, and if the film is formed from multiple layers, the type of additive in each layer For these details, the materials described in detail on pages 16 to 22 of the technique No. 2001-1745 described above are preferably used. The amount of each material added is not particularly limited as long as the function is exhibited, 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%. 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 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 kind of cellulose acylate solution may be cast as a single layer, or two or more kinds of cellulose acylate solutions may be cast simultaneously and / or sequentially.
As a method of 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 and laminating each (for example, a method described in JP-A-11-198285) 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. Can be 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 aforementioned technical number 2001-1745, and includes dissolution, casting (including co-casting), metal support, drying, peeling. Categorized as stretching, etc.

  The thickness of the first optically anisotropic medium is preferably 15 to 120 μm, more preferably 30 to 80 μm.

[Characteristics of polymer film]
[Hygroscopic expansion coefficient of film]
Furthermore, the hygroscopic expansion coefficient of the cellulose acylate film used in the present invention is preferably 30 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is preferably 15 × 10 ⁻⁵ /% RH or less, and more preferably 10 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is preferably small, but usually it is 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 film.
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 was cut out from the produced polymer film, and one end was fixed and hung in an atmosphere of 25 ° C. and 20% RH (R 0). A weight of 0.5 g was hung from the other end and left for 10 minutes to measure the length (L0). Next, the length (L1) was measured while the temperature was kept at 25 ° C. and the humidity was 80% RH (R1). The hygroscopic expansion coefficient was calculated by the following equation. The measurement was performed 10 samples for the same sample, and the average value was adopted.
Hygroscopic expansion coefficient [/% RH] = {(L1-L0) / L0} / (R1-R0)

  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 smaller the amount of residual solvent during film formation by the solvent casting method described later, the smaller the free volume. 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]
(Mechanical properties of film)
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 the center of the film, dust generation from the 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 stripes on the optical compensation film exceeds the allowable value. This 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 the reduction of the free volume by reducing the amount of residual solvent during film formation by the above-mentioned solution casting film forming method becomes the main effect factor.

  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. Further, in terms of 60 μm, 8 g or more is preferable, and more preferably 8 to 15 g. 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.

  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 as this range, the scratch resistance and handling property of the film surface can be maintained without any problem. The scratch strength can be evaluated with a load (g) by which the surface of the transparent protective film is scratched using a sapphire needle having a cone apex angle of 90 ° and a tip radius of 0.25 m, and the scratch mark can be visually confirmed.

(Equilibrium moisture content of film)
The equilibrium moisture content of the cellulose acylate film is determined depending on the film thickness so that the adhesiveness with a water-soluble polymer such as polyvinyl alcohol is not impaired when the optical compensation layer sheet is used as one transparent protective film of the polarizing plate. Regardless, the equilibrium moisture content at 25 × 80% RH is preferably 0 to 4% by mass. 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, it is preferable that the dependence of retardation on humidity change does not become too large when the cellulose acylate film is used as a transparent protective film of a polarizing plate.

  The moisture content was measured by a Karl Fischer method using a cellulose acylate film sample 7 mm × 35 mm, using a moisture measuring device “CA-03” and a sample drying device “VA-05” (both manufactured by Mitsubishi Chemical Corporation). It was measured. 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 is measured under the conditions of a temperature of 60 ° C. and a humidity of 95% RH based on JIS standard 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 film obtained by laminating an optically anisotropic layer on a cellulose acylate film is preferable because the absolute value of humidity dependency of Re value and Rth value is less than 0.5 nm /% RH. In addition, when such a polarizing plate with an optical compensation film 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 moisture 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 was conditioned at 25 ° C., 90% RH, 60 ° C., and 95% RH for 24 hours, respectively, and a moisture permeability test apparatus [“KK-709007” Toyo Seiki Co., Ltd.] calculates the amount of water per unit area (g / m ² ) according to JIS Z-0208, 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. 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 above-mentioned 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.

  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 treatment liquid include potassium hydroxide solution and sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0N. Furthermore, as an alkali treatment liquid, a solvent having good wettability to a film (eg, isopropyl alcohol, n-butanol, methanol, ethanol, etc.), a surfactant, a wetting agent (eg, 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, WO02 / 46809 gazette, Unexamined-Japanese-Patent No. 2003-43673, etc.

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

[Second optical anisotropic medium]
As the second optically anisotropic medium, there can be used an optically anisotropic layer made of a discotic compound, an optically anisotropic layer made of rod-like liquid crystalline molecules, a polymer film by stretching, and the like. Among them, the second optically anisotropic medium is preferably an optically anisotropic layer containing a discotic compound. Examples of the discotic compound mainly include discotic liquid crystalline compounds.

The rod-like liquid crystalline molecules and discotic compounds may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which low-molecular liquid crystals are cross-linked and no longer exhibit liquid crystallinity.
[Rod-like liquid crystalline molecules]
As rod-like liquid crystalline molecules, 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 molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 of the Chemical Chemistry of the Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), and the 142nd Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.

[Disc liquid crystalline molecules]
Examples of discotic compounds that can be used in the present invention include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  Examples of discotic compounds include compounds 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. In the optically anisotropic layer formed from the discotic liquid crystalline molecules, the compound finally contained in the optically anisotropic layer does not need to be a discotic liquid crystalline molecule. Also included are compounds having a group that reacts with heat or light and, as a result, polymerized or cross-linked by reaction with heat or light, resulting in a high molecular weight and loss of liquid crystallinity. Preferred examples of the discotic liquid crystalline molecules are described in JP-A-8-50206. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

  In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. 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 paragraphs [0151] to “0168” in JP-A No. 2000-155216.

  In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule 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 molecules on the polarizing film side can be generally adjusted by selecting a discotic liquid crystalline molecule or an alignment film material, or by selecting a rubbing treatment method. In addition, the major axis (disk surface) direction of the surface-side (air-side) discotic liquid crystalline molecules is generally adjusted by selecting the type of additive used together with the discotic liquid crystalline molecules or discotic liquid crystalline molecules. be able to. Examples of the additive used together with the discotic liquid crystalline molecule include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

[Other compositions of second optically anisotropic medium]
It is possible to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, etc. by using a plasticizer, a surfactant, a polymerizable monomer, etc. together with the above discotic compound or rod-like liquid crystalline compound. I can do it. It is preferable that the compound has compatibility with a discotic compound or the like and can change the tilt angle of the molecule or does not inhibit the orientation.

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

  Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include compounds described in paragraph numbers [0028] to [0056] in JP-A-2001-330725.

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

  In the alignment of an optically anisotropic layer containing a liquid crystal 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 film are also birefringence characteristics, that is, It is considered that adjusting the angle dependency of retardation is a simple and most tangible method for effectively improving the contrast viewing angle.

  Therefore, the optical compensation film used in the present invention includes, as an optical component, a transparent support film having negative birefringence as described above, and a tilt-oriented optically anisotropic layer coated thereon. Retardation value measured from the film normal direction of the optically anisotropic layer: direction in which Re is 40 nm or more and is inclined by 40 ° from the film normal in a plane perpendicular to the film including the orientation direction Retardation value measured from: Re (40): Re: Ratio Re (40) / Re is less than 2.0, and -40 from the film normal in the plane perpendicular to the film including the orientation direction. The ratio of retardation value Re (−40) measured from an inclined direction: Re (−40) / Re is preferably 0.4 or more. When such an optical compensation film is used, it becomes possible to greatly improve the contrast viewing angle of the liquid crystal display device. In particular, such an optical compensation film is effective for optical compensation of a normally white TN alignment cell.

The optical compensation film in the liquid crystal display device of the present invention is provided between the first optical anisotropic medium composed of the polymer substrate surface-treated as described above and the second optical anisotropic medium provided thereon. It is preferable to provide an alignment film.
[Alignment film]
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 liquid crystalline compound, the alignment film plays the role, and thus is not necessarily an essential component of the present invention. That is, only the optically anisotropic layer on the alignment film in which the alignment state is fixed is transferred onto the polarizer, and Re (λ) and Rth (λ) related to the first optically anisotropic medium are set to 0. Even if the conditions 1) to (6) are satisfied at the same time, it is possible to obtain a liquid crystal display device with an improved tint variation which is an object of the present invention.

  The alignment film is an organic compound (eg, 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-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). 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 crosslink having a function of aligning a side chain having a crosslinkable functional group (eg, double bond) to the main chain or aligning liquid crystalline molecules. It is preferable to introduce a functional functional 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 the polymer include methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol) described in paragraph No. [0022] of JP-A-8-338913. Acrylamide), 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) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. . 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 Examples include substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy), and the like. As specific examples of these modified polyvinyl alcohol compounds, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426 are described. [0022] and the like.

When a side chain having a crosslinkable functional group is bonded to the main chain of the alignment film polymer, or a crosslinkable functional group is introduced into a side chain having a function of aligning liquid crystalline molecules, the alignment film polymer and the optically anisotropic film The polyfunctional monomer contained in the conductive 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 film 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] in JP-A-2000-155216.

Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent.
Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole, and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [0024] in JP-A-2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

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

  The alignment film can be basically formed by applying the polymer on the transparent support containing the alignment film forming material and the crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be performed at an arbitrary time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (eg, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the 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), rod coating method or roll coating method. In particular, the slot die coating method described later 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 transparent 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 the orientation by rubbing the surface of the orientation film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. Generally, it is carried out by rubbing several times using a cloth or the like in which fibers having a uniform length and thickness are planted 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.

[Formation of second optically anisotropic medium]
The second optically anisotropic medium can be formed by applying a coating liquid containing liquid crystalline molecules and, if necessary, a polymerizable initiator described later and optional components on the alignment film.
As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
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 second optically anisotropic medium is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

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

The amount of the photopolymerization initiator used is preferably 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.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
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 provided on the optically anisotropic layer.

[Polarizing film]
The optical compensation film used in the present invention exhibits its functions remarkably by being bonded to a polarizing plate or used as a protective film for a polarizing plate.
As described above, in the second optically anisotropic medium, the first optically anisotropic medium is omitted, and Re (λ) and Rth (λ) are set to 0, and the equations (1) to (6) obtained from Table 1 are used. ) May be formed directly from the liquid crystal molecules on the polarizing film so as to satisfy the above), or may be formed from the liquid crystal molecules through an alignment film. Specifically, the optically anisotropic layer and the second optically anisotropic medium are formed by applying the coating liquid for the optically anisotropic layer as described above to 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 with a small stress (strain × cross-sectional area × elastic modulus) associated with the dimensional change of the polarizing film is created. . Even when the polarizing plate according to the present invention is attached to a large liquid crystal display device, an image with high display quality can be displayed without causing problems such as light leakage.

The polarizing film is manufactured by Optiva Inc. And a polarizing film comprising a binder and iodine or a dichroic dye is preferable.
Iodine and dichroic dye in the polarizing film exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal.
Currently, commercially available polarizers are made by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.
The commercially available polarizing film has iodine or dichroic dye distributed about 4 μm (about 8 μm on both sides) from the polymer surface, and a thickness of at least 10 μm is necessary to obtain sufficient polarization 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 binder 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 on a 17-inch liquid crystal display device.

  The binder of the polarizing film may be cross-linked. As the crosslinked binder, 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 binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change. Moreover, you may introduce | transduce a crosslinked structure into a polymer 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 stage of the final product, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

  As the binder 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 for the alignment film. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. 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 addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the moisture and heat resistance of the polarizing film are improved.
The alignment film contains a certain amount of a 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. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.

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

  It is also possible to dispose the polarizing film and the optically anisotropic medium, or the polarizing film and the alignment film via an adhesive. 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]
For the polarizing film, a method of continuously stretching between a plurality of rollers is the most common method, but from the viewpoint of yield, the binder is inclined by 10 to 80 degrees 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 axis 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 binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.
As described above, a binder film that is obliquely stretched by 10 to 80 degrees 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, orientation is obtained by rubbing the surface of the 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 planted on average.

It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are 30 μm or less. The film wrap angle 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, the film is preferably transported at a speed of 1 to 100 m / min in a constant tension state 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 liquid crystal display device, the angle is preferably 40 to 50 °. 45 ° is particularly preferred.

It is preferable to dispose a polymer film on the surface opposite to the optically anisotropic medium via the polarizing film (arrangement of optically anisotropic medium / polarizing film / polymer film).
It is also preferable that the polymer film is provided with an antireflection film having an outermost surface having antifouling properties and scratch resistance. Any conventionally known antireflection film can be used.

  In the following, the optimum values of the formulas (1) to (6) are obtained by computer experiments, and simulations are repeated to obtain specific actual prototype examples of the formulas (1) to (6) obtained in Table 1. Will be explained. The materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[Example]
(Preparation of transparent support)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.
(Cellulose acetate solution composition)
Cellulose acetate (linter) with an acetylation degree of 60.9% 80 parts by mass Cellulose acetate (linter) with an acetylation degree of 60.8% 20 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass Methylene chloride (first solvent) 300 parts by mass Methanol (second solvent) 54 parts by mass 1-butanol (third solvent) 11 parts by mass

In another mixing tank, 16 parts by mass of the following retardation increasing agent, 80 parts by mass of methylene chloride and 20 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution.
A dope was prepared by mixing 474 parts by mass of the cellulose acetate solution with 25 parts by mass of the retardation increasing agent solution and stirring sufficiently. The addition amount of the retardation increasing agent was 3.5 parts by mass with respect to 100 parts by mass of cellulose acetate.

The obtained dope was cast using a band casting machine. After the film surface temperature on the band reaches 40 ° C., the film is dried for 1 minute, peeled off, and then dried by 140 ° C., and the first optical anisotropic medium having a residual solvent amount of 0.3% by mass A transparent support was produced.
The width of the obtained transparent support was 1500 mm and the thickness was 65 μm.
Moreover, it was 4 nm when the retardation value (Re) in wavelength 550nm was measured using the ellipsometer (M-150, JASCO Corporation make). Moreover, it was 78 nm when the retardation value (Rth) of the thickness direction was measured.

Surface saponification treatment was performed in the same manner as the saponification treatment described in Example 1 of WO02 / 46809 specification using an alkaline solution having the following contents. The contact angle between the film surface and water was 32 degrees, and the surface energy was 61 mN / m.
Composition of alkaline solution:
Potassium hydroxide 5.6 parts by mass Isopropyl alcohol 65.5 parts by mass Ethylene glycol 12 parts by mass Fluoroaliphatic group-containing copolymer 1.0 part by mass (Megafac F780 manufactured by Dainippon Ink Co., Ltd.)
11.4 parts by weight of water

<Formation of alignment film>
On the above transparent support, a coating solution having the following composition was coated with a # 16 wire bar coater at a coating amount of 28 ml / m ² , then heated with 60 ° C. warm air for 60 seconds, and further with a temperature of 90 ° C. Dry with wind for 150 seconds. A rubbing treatment was performed in a direction rotated 4 ° clockwise from the slow axis of the transparent support to obtain an alignment film.
<Alignment film coating solution composition>
Modified polyvinyl alcohol having the following structure 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight

<Formation of discotic compound layer>
90 parts by mass of liquid crystalline discotic compound (A), 10 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), melamine formaldehyde / acrylic acid copolymer (Aldrich reagent) 0.6 Part by mass, 3.0 parts by mass of a photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) and 1.0 part by mass of a photosensitizer (Kaya Cure DETX, manufactured by Nippon Kayaku Co., Ltd.) are dissolved in methyl ethyl ketone. A solution having a solid content concentration of 38% by mass was prepared as a coating solution.

  This coating solution was continuously applied onto the alignment film with a # 3.8 wire bar and heated at 130 ° C. for 2 minutes to orient the molecules of the liquid crystalline discotic compound.

  Next, UV irradiation was performed for 1 minute using a 120 W / cm high pressure mercury lamp at 100 ° C. to polymerize the liquid crystalline discotic compound. Then, it stood to cool to room temperature. In this way, an optical compensation film with a discotic compound layer as a second optically anisotropic medium was produced. The thickness of the formed discotic compound layer was 1.5 μm. Only this optically anisotropic layer was peeled from the transparent support, and the β value was output with an ellipsometer (M-150 manufactured by JASCO Corporation), which was 38.5 °. Tables 2 and 3 show other characteristic values of the optical compensation film, Rth (λ) and Re (λ), which are converted into the relational expressions of the present invention.

(Preparation of polarizing film)
PVA having an average polymerization degree of 4000 and a saponification degree of 99.8 mol% was dissolved in water to obtain a 4.0% aqueous solution. This solution was band-cast using a die having a taper and dried to form a film so that the width before stretching was 110 mm, the thickness was 120 μm at the left end, and 135 μm at the right end.
This film was peeled off from the band, obliquely stretched in the 45 ° direction in a dry state, and immersed in an aqueous solution of iodine 0.5 g / L and potassium iodide 50 g / L for 1 minute at 30 ° C., and then boric acid. Iodine polarizing film was immersed in an aqueous solution of 100 g / L and potassium iodide 60 g / L at 70 ° C. for 5 minutes, further washed with water at 20 ° C. for 10 seconds and then dried at 80 ° C. for 5 minutes. Obtained. The polarizing film had a width of 660 mm and a thickness of 20 μm on both sides.

(Preparation of polarizing plate)
Using a polyvinyl alcohol-based adhesive, the optical compensation film was attached to one side of the polarizing film on the transparent support surface. Again, another triacetyl cellulose film: Fujitac TD-80U was subjected to saponification treatment performed with the transparent support of WO 02/46809, and on the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Pasted.
The absorption axis of the polarizing film and the slow axis of the transparent support were arranged in parallel. The slow axis of the above-mentioned Fujitac TD-80U was also arranged in parallel. In this way, a polarizing plate with an optical compensation film comprising a transparent support and a discotic compound was prepared.

(Evaluation with TN mode liquid crystal display)
A pair of polarizing plates provided in a liquid crystal display device (SyncMaster 172x, Nippon Samsung Co., Ltd.) using a twisted nematic alignment mode liquid crystal cell is peeled off, and Δnd of the liquid crystal layer and the twist direction of the liquid crystal are set to Shintech Co., Ltd. ) Measurement was performed using a general-purpose deflection analyzer H33. Δnd was about 420 nm at 450 nm, about 400 nm at 550 nm, and about 380 nm at 610 nm. It was confirmed that the liquid crystal cell was twisted about 90 ° clockwise from the light source side toward the display observation side as viewed from the display side. An optical compensation film made as a prototype so as to be orthogonal to the upper and lower liquid crystal layer rubbing axes was attached to the front and back of the liquid crystal cell to obtain a display device.

  From Table 1, it confirmed that the produced liquid crystal display device satisfy | fills Formula (1)-(6) simultaneously as shown in the said Table 2 and 3. FIG.

[Conventional example]
A pair of polarizing plates provided in the same liquid crystal display device (SyncMaster 172x, Nippon Samsung Co., Ltd.) as in the examples is peeled off, a conventional optical compensation film (Fuji Photo Film Co., Ltd.), an iodine polarizing film, and a protective film A commercially available wide viewing angle polarizing plate (LPT-HL56-12, manufactured by Sanritz Co., Ltd.) with a film integrated in advance was attached and used as a display device in the same manner as in the examples.

  About 2 types of produced liquid crystal display devices, the color was measured using the measuring machine (EZ-Contrast160D, ELDIM company make). In the CIE 1976 UCS coordinates, the distance Δu′v ′ on the coordinates of the maximum v ′ and the minimum v ′ in the vertical direction (80 ° to 80 ° below the display normal) was compared. As a result, Δu′v ′ was 0.08 in the display device of the example, and 0.13 in the conventional example that does not satisfy the expressions (1) to (6) at the same time.

  In the case of the examples satisfying the formulas (1) to (6) of the present invention at the same time, it was found that the color variation from yellow to blue was improved (reduced) compared to the conventional example. It was found that the target was 0.12 or less.

It is a schematic diagram of one embodiment of a liquid crystal display device of the present invention. 2 is a Poincare sphere for explaining the principle of optical compensation of the liquid crystal display device of FIG. It is a figure used in order to demonstrate that a fixed ratio generate | occur | produces in Re, Rth of 450 nm, 550 nm, and 610 nm on the Poincare sphere of FIG. It is a CIE1976UCS chromaticity diagram. It is a schematic diagram of an example of the conventional liquid crystal display device.

Explanation of symbols

1a, 1b Transparent protective film 2a, 2b Polarizing film 3a, 3b Transparent support 4a, 4b Optically anisotropic layer 5a, 5b Upper and lower substrates 6 of liquid crystal cell L. Backlight 51 Liquid crystal cell 52 Schematic diagram of rod-like liquid crystalline molecules 53 Schematic diagrams showing the orientation of discotic compounds 54a and 54b Diagrams showing arrangement examples of optical compensation films

Claims (3)

A TN mode liquid crystal cell; a polarizing film disposed on both sides of the liquid crystal cell; and an optical compensation film disposed between the liquid crystal cell and the upper and lower polarizing films. A liquid crystal display device comprising the first optically anisotropic medium and the second optically anisotropic medium and simultaneously satisfying the following formulas (1) to (6);
(1) 1.06 ≦ Δnd (450) / 2 × (P_Rth (450) + D_Rth (450)) ≦ 1.18
(2) 1.04 ≦ Δnd (550) / 2 × (P_Rth (550) + D_Rth (550)) ≦ 1.14
(3) 1.02 ≦ Δnd (610) / 2 × (P_Rth (610) + D_Rth (610)) ≦ 1.12
(4) 0.28 ≦ 2 × (P_Re (450) + D_Re (450)) / (450 × 10 ⁻⁹ ) ≦ 0.30
(5) 0.21 ≦ 2 × (P_Re (550) + D_Re (550)) / (550 × 10 ⁻⁹ ) ≦ 0.23
(6) 0.19 ≦ 2 × (P_Re (610) + D_Re (610)) / (610 × 10 ⁻⁹ ) ≦ 0.21
Where Δnd is the product of the rod-like liquid crystal birefringence Δn in the liquid crystal cell and the thickness d of the liquid crystal layer; P_Rth (λ) and P_Re (λ) are respectively the first optical anisotropic medium at the wavelength λ Rth and Re; D_Rth (λ) and D_Re (λ) mean Rth and Re of the second optically anisotropic medium at the wavelength λ, respectively. The liquid crystal display device according to claim 1, wherein the optical compensation film further satisfies the following formulas (7) to (12):
(7) Δnd (450) / 2 × (P_Rth (450) + D_Rth (450)) = 1.12
(8) Δnd (550) / 2 × (P_Rth (550) + D_Rth (550)) = 1.09
(9) Δnd (610) / 2 × (P_Rth (610) + D_Rth (610)) = 1.07
(10) 2 × (P_Re (450) + D_Re (450)) / (450 × 10 ⁻⁹ ) = 0.29
(11) 2 × (P_Re (550) + D_Re (550)) / (550 × 10 ⁻⁹ ) = 0.22
(12) 2 × (P_Re (610) + D_Re (610)) / (610 × 10 ⁻⁹ ) = 0.20 3. The liquid crystal display device according to claim 1, wherein one of the first and second optically anisotropic media is a transparent support, and the other is an optically anisotropic layer containing a discotic compound.

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