JP2007279158A - Optical compensation film, polarization plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film for a VA (vertically aligned) or OCB (optically compensatory bend) mode liquid crystal cell, and to provide a polarization plate and a liquid crystal display device. <P>SOLUTION: The optical compensation film has a transparent support and an optical anisotropic layer, wherein the transparent support satisfies the relation expressed by formulae (1) to (4) and the optical anisotropic layer satisfies the relation expressed by formulae (5) to (8). They are: (1):10 nm≤Re<SB>(550)</SB>≤100 nm; (2):20 nm≤Rth<SB>(550)</SB>≤150 nm; (3):0.4≤äRe<SB>(450)</SB>/Rth<SB>(450)</SB>}/äRe<SB>(550)</SB>/Rth<SB>(550)</SB>}≤0.95; (4):1.02≤äRe<SB>(630)</SB>/Rth<SB>(630)</SB>}/äRe<SB>(550)</SB>/Rth<SB>(550)</SB>}≤1.9; (5):0 nm≤Re<SB>2(550)</SB>≤10 nm; (6):20 nm≤Rth<SB>2(550)</SB>≤100 nm; (7):1.10<Rth<SB>2(450)</SB>/Rth<SB>2(550)</SB><1.35; and (8):0.90<Rth<SB>2(630)</SB>/Rth<SB>2(550)</SB><1.00. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical compensation film, a polarizing plate, and a liquid crystal display device.

  The liquid crystal display device has a liquid crystal cell and a polarizing plate. The polarizing plate generally has a protective film and a polarizing film made of cellulose acetate. For example, a polarizing film made of a polyvinyl alcohol film is dyed with iodine, stretched, and both surfaces thereof are laminated with a protective film. Obtained. In a transmissive liquid crystal display device, polarizing plates are attached to both sides of a liquid crystal cell, and one or more optical compensation films may be disposed. In a reflective liquid crystal display device, the reflector, liquid crystal cell, one or more optical compensation films, and a polarizing plate are usually arranged in this order. The liquid crystal cell includes a liquid crystal molecule, two substrates for encapsulating the liquid crystal molecule, and an electrode layer for applying a voltage to the liquid crystal molecule. The liquid crystal cell performs ON / OFF display depending on the alignment state of liquid crystal molecules, and can be applied to both transmission and reflection types. TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend). ), VA (Vertically Aligned), and ECB (Electrically Controlled Birefringence) have been proposed.

  Among such LCDs, for applications that require high display quality, a 90 degree twisted nematic liquid crystal display device (hereinafter referred to as a TN mode) that uses nematic liquid crystal molecules having positive dielectric anisotropy and is driven by a thin film transistor. Is mainly used. However, although the TN mode has excellent display characteristics when viewed from the front, the contrast is lowered when viewed from an oblique direction, and display is caused by gradation inversion in which the brightness is reversed in gradation display. There is a viewing angle characteristic that the characteristic is deteriorated, and this improvement is strongly desired.

  On the other hand, the liquid crystal systems with wide viewing angles such as the IPS system, OCB system, and VA system have expanded their share with the recent increase in demand for liquid crystal televisions. Each system has improved display quality year by year (Patent Documents 1 to 14), but the problem of color misregistration that occurs when viewed obliquely has not been solved.

JP-A-9-212444 JP 11-316378 A Japanese Patent Laid-Open No. 2-176625 JP-A-11-95208 JP 2003-15134 A JP-A-11-95208 Japanese Patent Laid-Open No. 2002-221622 Japanese Patent Laid-Open No. 9-80424 Japanese Patent Laid-Open No. 10-54982 JP-A-11-202323 Japanese Patent Laid-Open No. 9-292522 JP 11-133408 A JP-A-11-305217 JP-A-10-307291

The present invention focuses on the wavelength dispersion characteristics of Re, which is the in-plane retardation of the optical compensation film, and Rth, which is the retardation in the thickness direction, and the Re and Rth of the transparent support may have any dispersion performance. In order to obtain the optical characteristics of a transparent support capable of designing an optically anisotropic layer having a degree of freedom, the present inventors have intensively studied, and as a result, have solved the above problems in the past, and The purpose is to achieve the goal. That is, the liquid crystal cell accurately compensates optically, realizes a high contrast, and improves the color shift depending on the viewing angle direction during black display, particularly an optical compensation film for VA, IPS and OCB modes, And it aims at providing the polarizing plate using the same.
It is another object of the present invention to provide a liquid crystal display device, particularly a VA, IPS, and OCB mode, in which contrast is improved and color shift depending on the viewing angle direction during black display is improved.

Means for solving the above-mentioned problems are as follows. That is,
<1> At least a transparent support and an optically anisotropic layer, wherein the transparent support includes a retardation increasing agent,
The optical support film is characterized in that the transparent support satisfies the following formulas (1) to (4), and the optically anisotropic layer satisfies the following formulas (5) to (8). .
However, in the following formulas (1) to (4), Re _(λ) is the retardation value of the transparent support for light with a wavelength of λnm, and Rth _(λ) is the transparent support for light with a wavelength of λnm. In the following formulas (5) to (8), Re _{2 (λ)} is a retardation value of the optically anisotropic layer with respect to light having a wavelength of _λ nm, and Rth _{2 (λ )} Is a retardation value in the thickness direction of the optically anisotropic layer with respect to light having a wavelength of λ nm.
(Equation 29)
10 nm ≦ Re ₍₅₅₀₎ ≦ 100 nm (1)
(Equation 30)
20 nm ≦ Rth ₍₅₅₀₎ ≦ 150 nm (2)
(Equation 31)
0.4 ≦ {Re ₍₄₅₀₎ / Rth ₍₄₅₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 0.95 (3)
(Expression 32)
1.02 ≦ {Re ₍₆₃₀₎ / Rth ₍₆₃₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 1.9 Equation (4)
(Expression 33)
0 nm ≦ Re _{2 (550)} ≦ 10 nm (5)
(Equation 34)
20 nm ≦ Rth _{2 (550)} ≦ 100 nm (6)
(Equation 35)
1.10 <Rth _{2 (450)} / Rth _{2 (550)} <1.35 (7)
(Equation 36)
0.90 <Rth _{2 (630)} / Rth _{2 (550)} <1.00 Equation (8)
<2> At least a transparent support and an optically anisotropic layer, wherein the transparent support includes a retardation increasing agent,
The transparent support satisfies the relationships of the following formulas (1) to (2) and (9) to (12), and the optically anisotropic layer satisfies the relationships of the following formulas (5) to (8). This is an optical compensation film.
However, in the following formulas (1) to (2) and (9) to (12), Re _(λ) is a retardation value of the transparent support for light having a wavelength of _λ nm, and Rth _(λ) is Retardation value in the thickness direction of the transparent support with respect to light having a wavelength of λ nm. In the following formulas (5) to (8), Re _{2 (λ)} is a letter of the optically anisotropic layer with respect to light with a wavelength of _λ nm. Rth _{2 (λ)} is a retardation value in the thickness direction of the optically anisotropic layer with respect to light having a wavelength of _λ nm.
(Equation 37)
10 nm ≦ Re ₍₅₅₀₎ ≦ 100 nm (1)
(Equation 38)
20 nm ≦ Rth ₍₅₅₀₎ ≦ 150 nm (2)
(Equation 39)
0.5 <Re ₍₄₅₀₎ / Re ₍₅₅₀₎ <1.0 (9)
(Equation 40)
1.0 <Re ₍₆₃₀₎ / Re ₍₅₅₀₎ <1.5 (10)
(Equation 41)
1.0 <Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ <1.5 ... Formula (11)
(Equation 42)
0.5 <Rth ₍₆₃₀₎ / Rth ₍₅₅₀₎ <1.0 (12)
(Equation 43)
0 nm ≦ Re _{2 (550)} ≦ 10 nm (5)
(Equation 44)
20 nm ≦ Rth _{2 (550)} ≦ 100 nm (6)
(Equation 45)
1.10 <Rth _{2 (450)} / Rth _{2 (550)} <1.35 (7)
(Equation 46)
0.90 <Rth _{2 (630)} / Rth _{2 (550)} <1.00 Equation (8)
<3> At least a transparent support and an optically anisotropic layer, wherein the transparent support includes a retardation increasing agent,
The transparent support satisfies the relationships of the following formulas (1) to (2), (9) to (10), and (13) to (14), and the optically anisotropic layer has the following formula (5). It is an optical compensation film characterized by satisfying the relationship of (8).
However, in the following formulas (1) to (2), (9) to (10), and (13) to (14), Re _(λ) is a retardation value of the transparent support with respect to light having a wavelength of _λ nm. Rth _(λ) is a retardation value in the thickness direction of the transparent support with respect to light having a wavelength of _λ nm. In the following formulas (5) to (8), Re _{2 (λ)} is light having a wavelength of _λ nm. Rth _{2 (λ)} is a retardation value in the thickness direction of the optically anisotropic layer with respect to light having a wavelength of λnm.
(Equation 47)
10 nm ≦ Re ₍₅₅₀₎ ≦ 100 nm (1)
(Formula 48)
20 nm ≦ Rth ₍₅₅₀₎ ≦ 150 nm (2)
(Equation 49)
0.5 <Re ₍₄₅₀₎ / Re ₍₅₅₀₎ <1.0 (9)
(Equation 50)
1.0 <Re ₍₆₃₀₎ / Re ₍₅₅₀₎ <1.5 (10)
(Equation 51)
0.5 <Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ <1.0 Expression (13)
(Formula 52)
1.0 <Rth ₍₆₃₀₎ / Rth ₍₅₅₀₎ <1.5 (Equation 14)
(Formula 53)
0 nm ≦ Re _{2 (550)} ≦ 10 nm (5)
(Equation 54)
20 nm ≦ Rth _{2 (550)} ≦ 100 nm (6)
(Equation 55)
1.10 <Rth _{2 (450)} / Rth _{2 (550)} <1.35 (7)
(Formula 56)
0.90 <Rth _{2 (630)} / Rth _{2 (550)} <1.00 Equation (8)
<4> The optical compensation film according to any one of <1> to <3>, wherein the retardation increasing agent is included in an amount of 0.5 to 15% by mass relative to the cellulose ester that is a main component of the transparent support.
<5> The optical compensation film according to any one of <1> to <4>, wherein the optically anisotropic layer includes a discotic compound and a cholesteric compound.
<6> The optical compensation film according to any one of <1> to <5>, wherein the support is at least one stretched cellulose acylate film.
<7> A polarizing plate having a polarizing film and a pair of protective films sandwiching the polarizing film, wherein at least one of the protective films is the optical compensation according to any one of <1> to <6> It is a polarizing plate characterized by being a film.
<8> A liquid crystal display device comprising the liquid crystal cell and the polarizing plate according to <7>.
<9> The liquid crystal display device according to <8>, wherein the liquid crystal cell is VA mode or OCB.

According to the present invention, the liquid crystal cell accurately optically compensates, realizes a high contrast, and improves the color shift depending on the viewing angle direction during black display, particularly for VA or OCB mode. A film and a polarizing plate using the film can be provided.
In addition, according to the present invention, it is possible to provide a liquid crystal display device, particularly a VA or OCB mode, in which the contrast is improved and the color shift depending on the viewing angle direction during black display is improved.

Hereinafter, the optical compensation film, the polarizing plate, and the liquid crystal display device according to the present invention will be described in detail.
In the description of the present embodiment, “45 °”, “parallel” or “orthogonal” means that the angle is within a range of strictly less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °. Regarding the angle, “+” means the clockwise direction, and “−” means the counterclockwise direction. Further, the “slow axis” means a direction in which the refractive index is maximized. The “visible light region” means 380 to 780 nm. Further, the refractive index measurement wavelength is a value in the visible light region (λ = 550 nm) unless otherwise specified.

In the description of the present embodiment, the term “polarizing plate” is used to include both a long polarizing plate and a polarizing plate cut into a size incorporated in a liquid crystal device unless otherwise specified. Yes. Here, “cutting” includes “punching” and “cutting out”.
In the description of the present embodiment, “polarizing film” and “polarizing plate” are distinguished from each other. However, “polarizing plate” is a laminate having a transparent protective film that protects the polarizing film on at least one side of “polarizing film”. It shall mean the body.

In the description of the present embodiment, the “molecular symmetry axis” refers to a symmetry axis when the molecule has a rotational symmetry axis, but strictly requires that the molecule is rotationally symmetric. is not.
In general, in a discotic liquid crystalline compound, the molecular symmetry axis coincides with an axis perpendicular to the disc surface passing through the center of the disc surface, and in a rod-like liquid crystalline compound, the molecular symmetry axis is the long axis of the molecule. Match.

In this 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 with KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) by making light of wavelength λ nm incident in the normal direction of the film.
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is the film surface when Re (λ) is used and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotary axis) (if there is no slow axis) Measurement is performed at a total of 6 points by injecting light of wavelength λ nm from each inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction (with any direction in the rotation axis). Then, KOBRA 21ADH or WR calculates based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
Note that the retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis). Rth can also be calculated from the following formula (A) and formula (B) based on the value, the assumed value of the average refractive index, and the input film thickness value.

(Equation 57)
・ ・ ・ ・ ・ ・ Formula (A)
Note that Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
Further, nx in the formula (A) represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the refraction in the direction orthogonal to nx and ny. Represents a rate.

(Formula 58)
Rth = ((nx + ny) / 2−nz) × d (Equation (B)
When the film to be measured is a film that cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is from −50 degrees with respect to the film normal direction, with Re (λ) being the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis). Measured at 11 points by making light of wavelength λ nm incident from each tilted direction in steps of 10 degrees up to +50 degrees, and based on the measured retardation value, the assumed average refractive index and the input film thickness value. KOBRA 21ADH or WR is calculated.
In the above measurement, 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 or WR calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

(Configuration of liquid crystal display device)
FIG. 1 is a diagram showing a configuration of a liquid crystal display device of the present invention.
As shown in FIG. 1, the OCB mode liquid crystal display device includes a liquid crystal layer in which liquid crystal bends with respect to the substrate surface when a voltage is applied, that is, black display, a substrate 6 and a substrate 8 sandwiching the liquid crystal layer. A liquid crystal cell comprising:
As for the board | substrate 6 and the board | substrate 8, the alignment process is given to the surface at the side of a liquid crystal layer. The orientation direction (rubbing direction) is indicated by an arrow RD. In the case of the back surface, it is indicated by a broken line arrow. The polarizing films 1 and 101 are disposed so as to sandwich the liquid crystal cell, and the transmission axis 2 of the polarizing film 1 and the transmission axis 102 of the polarizing film 101 are orthogonal to each other and in the RD direction of the liquid crystal layer of the liquid crystal cell. And 45 degrees.
An optical compensation film 13A (113A) is disposed between the polarizing film 1 (101) and the liquid crystal cell. The optical compensation film 13A (113A) is optically anisotropic with the cellulose acylate film 13a (113a). Layer 13b (113b) and another optically anisotropic layer 5 (9) in which molecules of the discotic compound are fixed in a hybrid alignment state in which the inclination angle with respect to the film plane is different in the thickness direction. ing. The cellulose acylate film 13a (113a) has a slow axis 4a (104a) arranged in parallel with the direction of the transmission axis 2 (102) of the polarizing film 1 (101) adjacent thereto.

The liquid crystal cell in FIG. 1 includes a liquid crystal layer formed of an upper substrate 6 and a lower substrate 8 and liquid crystal molecules 7 sandwiched between them. An alignment film (not shown) is formed on the surface of the substrate 6 and the substrate 8 that is in contact with the liquid crystal molecules 7 (hereinafter sometimes referred to as “inner surface”). The orientation of the molecules 7 is controlled in a parallel direction with a pretilt angle.
Further, on the inner surfaces of the substrate 6 and the substrate 8, a transparent electrode (not shown) capable of applying a voltage to the liquid crystal layer made of the liquid crystal molecules 7 is formed.
In the present invention, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn is preferably 0.1 to 1.5 μm, more preferably 0.2 to 1.5 μm. Is more preferably 0.3 to 1.2 μm, and particularly preferably 0.4 to 1.0 μm. In these ranges, since the white display luminance when white voltage is applied is high, a bright and high-contrast display device can be obtained. The liquid crystal material to be used is not particularly limited, but in a mode in which an electric field is applied between the upper and lower substrates 6 and 8, the liquid crystal material having a positive dielectric anisotropy such that the liquid crystal molecules 7 respond in parallel to the electric field direction. Is used.

For example, when the liquid crystal cell is an OCB mode liquid crystal cell, the dielectric anisotropy between the upper substrate 6 and the lower substrate 8 is positive and Δn = 0.16 and Δε = 5 or so. A liquid crystal material or the like can be used.
The thickness d of the liquid crystal layer is not particularly limited, but can be set to about 4 μm when a liquid crystal having the above characteristics is used. The brightness at the time of white display changes depending on the thickness Δ and the product Δn · d of the refractive index anisotropy Δn when white voltage is applied, so that sufficient brightness can be obtained when white voltage is applied. The Δn · d of the liquid crystal layer in the non-application state is preferably set to be in the range of 0.4 to 1.0 μm.

In addition, in the OCB mode liquid crystal display device, the addition of a chiral material generally used in the TN mode liquid crystal display device is rarely used to degrade the dynamic response characteristics, but in order to reduce alignment defects. May be added.
In addition, the multi-domain structure is advantageous for adjusting the alignment of the liquid crystal molecules in the boundary region between the domains.
Here, the multi-domain structure refers to a structure in which one pixel of a liquid crystal display device is divided into a plurality of regions. For example, in the OCB mode, a multi-domain structure is preferable because the viewing angle characteristics of luminance and color tone are improved.
Specifically, each pixel is composed of two or more (preferably 4 or 8) regions in which the initial alignment state of the liquid crystal molecules is different from each other, and the luminance and color tone bias depending on the viewing angle are averaged. Can be reduced. Further, the same effect can be obtained even if each pixel is composed of two or more different regions where the alignment direction of liquid crystal molecules continuously changes in a voltage application state.

The transparent support 13a (113a) and the optically anisotropic layer 13b (113b) may function as a support for another optically anisotropic layer 5 (9), or the polarizing film 1 (101). It may function as a protective film or may have both functions. That is, the polarizing film 1 (101), the transparent support 13a (113a), the optically anisotropic layer 13b (113b), and the other optically anisotropic layer 5 (9) are liquid crystal as an integrated laminate. It may be incorporated inside the display device or may be incorporated as a single member.
Further, a protective film for a polarizing film may be separately disposed between the transparent support 13a (113a) and the polarizing film 1 (101), but the protective film is not disposed. Is preferred. The slow axis 14a of the transparent support 13a and the slow axis 114a of the transparent support 113a are preferably substantially parallel or orthogonal to each other. When the slow axis 14a of the transparent support 13a and the slow axis 114a of the transparent support 113a are orthogonal to each other, the birefringence of each transparent support cancels each other, thereby perpendicularly entering the liquid crystal display device. It is possible to reduce deterioration of optical characteristics of light. Further, in a mode in which the slow axes 14a and 114a are parallel to each other, when there is a residual phase difference in the liquid crystal layer, this phase difference can be compensated for by birefringence of the protective film.

  Regarding the transmission axis 2 (102) of the polarizing film 1 (101), the slow axis direction 14a (114a) of the transparent support 13a (113a), and the alignment direction of the liquid crystal molecules 7, the materials used for each member and the display mode Then, the optimum range is adjusted according to the laminated structure of the members. That is, the transmission axis 2 of the polarizing film 1 and the transmission axis 102 of the polarizing film 101 are arranged so as to be substantially orthogonal to each other. However, the liquid crystal display device of the present invention is not limited to this configuration.

Another optically anisotropic layer 5 (9) is disposed between the transparent support 13a (113a) and the liquid crystal cell. Another optically anisotropic layer 5 (9) is a layer formed from a composition containing a liquid crystal compound, for example, a rod-like compound or a discotic compound.
In another optically anisotropic layer 5 (9), the molecules of the liquid crystal compound are fixed in a predetermined alignment state.
The orientation average direction 5a (9a) at the interface of at least the optically anisotropic layer 13b (113b) of the molecular symmetry axis of the liquid crystalline compound in another optically anisotropic layer 5 (9) and the transparent support 13a (113a) ) Intersects the slow axis 14a (114a) in the plane of approximately 45 degrees. When arranged in such a relationship, another optically anisotropic layer 5 (9) causes retardation with respect to incident light from the normal direction, does not cause light leakage, and from an oblique direction. The effect of the present invention can be sufficiently exerted with respect to incident light. Even at the interface on the liquid crystal cell side, the orientation average direction of the molecular symmetry axis of another optically anisotropic layer 5 (9) is relative to the slow axis 14a (114a) in the plane of the cellulose acylate film 13a (113a). Is preferably about 45 degrees.

  In addition, the orientation average direction 5a on the polarizing film side (optical anisotropic layer interface side) of the molecular symmetry axis of the liquid crystalline compound of another optically anisotropic layer 5 is the transmission axis 2 of the polarizing film 1 located closer to it. And approximately 45 degrees. Similarly, the transmission axis of the polarizing film 101 where the orientation average direction 9a on the polarizing film side (optical anisotropic layer interface side) of the molecular symmetry axis of the liquid crystalline compound of another optically anisotropic layer 9 is located closer. It is preferable to arrange at 102 and approximately 45 degrees. When arranged in such a relationship, optical switching can be performed according to the sum of the retardation generated in another optically anisotropic layer 5 (9) and the retardation generated in the liquid crystal layer, and from an oblique direction. The effect of the present invention can be sufficiently exerted with respect to incident light.

<Principle of image display>
Next, the principle of image display of the liquid crystal display device will be described with reference to FIG.
In a driving state in which a driving voltage corresponding to black is applied to the transparent electrodes (not shown) of the substrate 6 and the substrate 8 of the liquid crystal cell, the liquid crystal molecules 7 in the liquid crystal layer are bend-aligned, and the surface at that time The internal retardation is canceled by the in-plane retardation of the other optically anisotropic layer 5 (9). As a result, the polarization state of the incident light hardly changes. Since the transmission axis 2 of the polarizing film 1 and the transmission axis 102 of the polarizing film 101 are orthogonal to each other, the light incident from below is polarized by the polarizing film 101 and passes through the liquid crystal cell while maintaining the polarization state. And is blocked by the polarizing film 1.
That is, the liquid crystal display device of FIG. 1 realizes an ideal black display in the driving state. On the other hand, in a driving state in which a driving voltage corresponding to white is applied to a transparent electrode (not shown), the liquid crystal molecules 7 in the liquid crystal layer have a bend alignment different from the bend alignment corresponding to black. It changes when the retardation is black. As a result, the in-plane retardation of another optically anisotropic layer 5 (9) does not cancel, and the polarization state changes by passing through the liquid crystal cell, and passes through the polarizing film 1. That is, a white display is obtained.

Conventionally, in the OCB mode, there is a problem that even if the front contrast is high, the contrast decreases in an oblique direction. At the time of black display, high contrast is obtained by compensation of the liquid crystal cell and the optically anisotropic layer in the front, whereas birefringence and rotation of the polarization axis occur in the liquid crystal molecules 7 when observed obliquely.
Further, the crossing angle between the transmission axis 2 of the polarizing film 1 and the transmission axis 102 of the polarizing film 101 is 90 ° perpendicular to the front, but is shifted from 90 ° when viewed obliquely. Conventionally, due to these two factors, there has been a problem that leakage light is generated in an oblique direction and the contrast is lowered.
In the liquid crystal display device of the present invention having the configuration shown in FIG. 1, Re / Rth in R, G, and B does not match, and the transparent support 13a (113a) having optical characteristics satisfying a specific condition, By using the isotropic layer 13b (113b), light leakage in an oblique direction during black display is reduced and the contrast is improved.

More specifically, in the present invention, by using the transparent support having the optical characteristics and the optically anisotropic layer, the R, G, and B wavelengths incident in the oblique direction are different for each wavelength. Optical compensation is possible with the slow axis and retardation.
Furthermore, another optically anisotropic layer 5 (9) in which the orientation of the liquid crystalline compound is fixed is obtained by aligning the orientation average direction at the transparent support side interface of the symmetry axis of the molecule of the liquid crystalline compound, and the slow axis of the transparent support. Is arranged so as to intersect at 45 °, it is possible to perform a unique compensation method of OCB orientation at all wavelengths.
As a result, the viewing angle contrast of black display is greatly improved, and the coloring in the viewing angle direction of black display is further reduced.
In particular, when the viewing angle is shaken in the left-right direction, for example, there is a difference in coloring at the polar angle of 60 degrees in the azimuth angle direction of 0 degrees and the 180-degree direction, and a left-right asymmetry has occurred. Is done.
Here, in this specification, as the wavelengths of R, G, and B, R has a wavelength of 630 nm, G has a wavelength of 550 nm, and B has a wavelength of 450 nm. The wavelengths of R, G, and B are not necessarily represented by these wavelengths, but are considered to be suitable wavelengths for defining optical characteristics that exhibit the effects of the present invention.

  In particular, in the present invention, attention is paid to Re / Rth which is a ratio of Re and Rth of the transparent support. This is because the value of Re / Rth determines the axes of two intrinsic polarizations in the propagation of light traveling obliquely through a biaxial birefringent medium. The two axes of intrinsic polarization in the propagation of light traveling obliquely through a biaxial birefringent medium are the major axis and the minor axis of the cross section formed when the refractive index ellipsoid is cut in the normal direction of the light traveling direction. Corresponds to the direction. In FIG. 2, when light traveling in an oblique direction is incident on the transparent support used in the present invention, the direction of one axis of two intrinsic polarizations, that is, the angle of the slow axis in this case, and Re / Rth An example of the result of calculating the relationship is shown.

In FIG. 2, the propagation direction of light is assumed to be azimuth = 45 degrees and polar angle = 34 degrees. As shown in FIG. 2, the angle of the slow axis does not depend on the wavelength of incident light, but is uniquely determined by Re / Rth. How the polarization state of incident light changes by passing through the transparent support is mainly determined by the slow axis orientation of the transparent support and the retardation of the transparent support. Then, the Re / Rth values are almost the same regardless of the R, G, and B wavelengths, that is, the slow axis angles are almost the same.
On the other hand, in the present invention, by defining the Re / Rth relationship separately for each of the R, G, and B wavelengths, both the slow axis and the retardation, which are factors that mainly determine the change in the polarization state, can be obtained. Optimization is performed for each wavelength of R, G, and B.
Then, when the light in the oblique direction passing through the transparent support passes through the optically anisotropic layer in which the orientation of the liquid crystalline compound is fixed and further passes through the bend-oriented liquid crystal layer, the retardation and the upper and lower polarizing films at any wavelength. The value of Re / Rth of the transparent support is adjusted according to the wavelength so that the two factors that the apparent transmission axis is deviated from the front can be compensated simultaneously.
Specifically, by increasing the Re / Rth of the transparent support as the wavelength increases, the difference in polarization state in R, G, and B caused by the wavelength dispersion of the optically anisotropic layer and the liquid crystal cell layer is eliminated. It became possible.
As a result, complete compensation is possible and reduction in contrast is reduced. If the parameters of the film are determined with R, G, and B representing the entire visible light region, almost complete compensation can be achieved in the entire visible light region.

Here, polar angle and azimuth angle are defined. The polar angle is a normal direction of the optical compensation film surface, that is, an inclination angle from the z-axis in FIG. 1. For example, the normal direction of the optical compensation film surface is a direction of polar angle = 0 degree.
The azimuth angle represents the azimuth rotated counterclockwise with respect to the positive direction of the x-axis. For example, the positive direction of the x-axis is the direction of the azimuth angle = 0 degree, and the positive direction of the y-axis is Azimuth angle = 90 degrees.
The oblique direction in which black display is most problematic is that the polarization axis of the polarizing layer is ± 45, so that the polar angle is not 0 degrees and the azimuth angle = 0 degrees, 90 degrees, 180 degrees. It mainly refers to the case of 270 degrees.

  In order to explain the effect of the present invention in more detail, the polarization state of the light incident on the liquid crystal display device is shown on the Poincare sphere in FIG. In FIG. 3, the S2 axis is an axis that penetrates vertically from the top to the bottom of the drawing, and FIG. 3 is a view of the Poincare sphere viewed from the positive direction of the S2 axis. Further, since FIG. 3 is shown in a plan view, the displacement of the point before and after the change of the polarization state is indicated by a straight arrow 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. The same applies to FIGS. 5 and 6 below.

3A shows the change in the polarization state of the G light incident from the left 60 ° on the liquid crystal display device of FIG. 1, and FIG. 3B shows the change in the polarization state of the G light incident from the right 60 °. FIG. The G light incident from the left 60 ° changes its polarization state as indicated by a point on the Poincare sphere in FIG.
Specifically, the polarization state I1 of G light that has passed through the polarizing film 101 passes through the transparent support 113a and the optically anisotropic layer 113b, passes through I2, passes through another optically anisotropic layer 9, and passes through I3. Polarization state of I4 passing through the liquid crystal layer of the liquid crystal cell at the time of black display, I5 passing through another optical anisotropic layer 5, and passing through the transparent support 113a and the optical anisotropic layer 13b And is blocked by the polarizing film 1 to display ideal black. On the other hand, the G light incident from the right 60 ° also changes its polarization state from I1 ′ → I2 ′ → I3 ′ → I4 ′ → I5 ′ → I6 ′.
Examining the state of change in the polarization state, the change in the polarization state caused by passing through another optically anisotropic layer 5 (9) and the liquid crystal layer is caused by the incident light from the left 60 ° and right 60 °. On the other hand, the change in the polarization state by passing through the transparent support 13a (113a) and the optically anisotropic layer 13b (113b) is incident light from 60 ° left and 60 ° right. Match. In order to reduce the left and right black glare and the left and right color shifts, it is necessary to satisfy this compensation condition at the left and right at the same time. That is, not only the G light but also the R (red) and B (blue) incident light in the visible light range, the positions of I6 and I6 ′ coincide with each other and the polarized light whose position is blocked by the polarizing film 1 is used. It must be in a position that indicates the state. The above transition is represented by a straight line in the figure, but is not necessarily limited to a linear transition on the Poincare sphere.

In the configuration of the conventional OCB mode liquid crystal display device as shown in FIG. 4, for example, in the configuration disclosed in Japanese Patent Laid-Open No. 11-316378, the optical compensation film whose Re / Rth exhibits the above wavelength dependency is disposed. Instead, for example, a transparent support 3a (103a) of another optically anisotropic layer 5 (9) is disposed. The transparent support 3a (103a) is used for the purpose of supporting another optically anisotropic layer 5 (9), and is made of a general polymer film.
Accordingly, there is no wavelength dependency on Re / Rth as shown by the transparent support 3a (103a), and the same Re and Rth are exhibited at any of the R, G, and B wavelengths.
As a result, in the conventional OCB mode liquid crystal display device, when voltage is applied, that is, when black is displayed, the front retardation of the liquid crystal cell and the optically anisotropic layer is canceled in the front, and black is obtained. In the direction, there was a problem that light leakage of black display could not be completely suppressed. In addition, sufficient viewing angle contrast cannot be obtained, and compensation cannot be made at all wavelengths, thus causing a coloring problem.

In order to explain in more detail, the result of calculating the polarization state of the R, G, B light incident on the OCB mode liquid crystal display device of the conventional configuration shown in FIG. 4 is shown on the Poincare sphere in FIG. FIG. 5A is a diagram showing changes in the polarization state of light incident from the left 60 ° for each of R, G, and B, and FIG. 5B is a change in the polarization state of light incident from the right 60 °. Is a diagram showing R, G and B respectively. In the drawing, the polarization state of R incident light is indicated by IR, the polarization state of G incident light is indicated by IG, and the polarization state of B incident light is indicated by IB. Further, as a configuration of the conventional OCB mode liquid crystal display device, the transparent support 3a (103a) in FIG. 4 has Re = 45 nm and Rth = 160 nm at any wavelength of R, G, and B. Assuming and assuming that another optically anisotropic layer 5 (9) is Re = 30 nm, the calculation was performed.
First, in FIG. 5A, the polarization state after passing through the polarizing film 101, IR1, IG1, and IB1 are equal. When attention is paid to the change in the polarization state of the B light, the B light incident from the left 60 ° transitions when the polarization state IB2 after passing through the transparent support 103a passes through another optically anisotropic layer 9. In the direction opposite to the direction in which the polarization state IB2 ′ after passing through the transparent support 103a transits by passing through another optically anisotropic layer 9 is shifted in the same direction as the incident light from 60 ° to the right. I can understand that it is shifted. In other words, the light incident from the left and the light incident from the right differ in how the transparent support 103a affects the polarization state. As a result, the final transition state IR6 of R, G and B incident light from the left 60 °, the position of IG6 and IB6, the final transition state IR6 ′ of the R, G and B incident light from the right 60 °, The positions of IG6 ′ and IB6 ′ are not only coincident, but are completely different at the left 60 ° and the right 60 °. Therefore, left and right black light leakage and left and right color misregistration occur, and it has been difficult to improve these simultaneously.

In the present invention, by disposing a transparent support exhibiting specific optical characteristics, the left and right black light leakage and the left and right color shift of the OCB mode liquid crystal display device are simultaneously improved. In order to explain in more detail, the result of calculating the polarization state of the R, G, B light passing through the OCB mode liquid crystal display device having the configuration of the present invention shown in FIG. 1 is shown on the Poincare sphere in FIG. It was.
6A is a diagram showing changes in the polarization state of light incident from the left 60 ° for each of R, G, and B. FIG. 6B is a polarization state of light incident from the right 60 °. It is the figure which showed the change of R about R, G, and B, respectively.
6 (a) and 6 (b), the polarization state of the R incident light is indicated by IR, the polarization state of the G incident light is indicated by IG, and the polarization state of the B incident light is indicated by IB.

  As shown in FIGS. 6A and 6B, R light, G light, and B light incident from the left and right pass through the transparent support 113a and the optically anisotropic layer 113b, and all of them are near S1 = 0. And the polarization state of the position shifted by reflecting the wavelength dependency of Re / Rth of the transparent support 113a. This shift makes it possible to cancel the shift in the polarization state that the R light, G light, and B light receive due to the wavelength dispersion of the other optically anisotropic layers 9 and 5 and the liquid crystal layer. As a result, the light that has entered from either the left or right direction can have the same final transition point regardless of the wavelength. As a result, it is possible to simultaneously improve the left and right black light omission and the left and right color shift.

  The present invention relates to a cellulose acylate film and an optically anisotropic layer having optical characteristics in which the wavelength dispersion of retardation is different between the normal direction and an oblique direction inclined with respect to the normal direction, for example, a polar angle of 60 degrees. By using such optical characteristics of the transparent support and the optically anisotropic layer positively for optical compensation, the left and right black lights and the right and left color shifts are improved at the same time. As long as this principle is used, the scope of the present invention is not limited by the display mode of the liquid crystal layer, and a liquid crystal display having a liquid crystal layer of any display mode such as VA mode, IPS mode, ECB mode, and TN mode. It can also be used for devices.

  Further, the liquid crystal display device of the present invention is not limited to the configuration shown in FIG. 1 and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizing film. In the case of use as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a backlight having a light emitting diode, a field emission element, or an electroluminescent element as a light source can be disposed on the back surface.

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

(Optical compensation film)
Next, an optical compensation film for realizing this optical compensation will be specifically described.

  The optical compensation film of the present invention has at least a support, and the support is not particularly limited as long as it is a transparent film, and may be a stretched polymer film or a coating type polymer. A combination of a layer and a polymer film may be used. As a material for the polymer film, a synthetic polymer is generally used. Examples of the synthetic polymer include polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin, and triacetyl cellulose.

The range of the following formula (3) relating to the support constituting the optical compensation film of the present invention is preferably 0.40 to 0.95, more preferably 0.55 to 0.8, and More preferably, it is 55-0.75.
The range of the following formula (4) relating to the support constituting the optical compensation film of the present invention is preferably 1.02-1.90, more preferably 1.02-1.45, More preferably, it is 1.02-1.40.

(Equation 59)
0.4 ≦ {Re ₍₄₅₀₎ / Rth ₍₄₅₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 0.95 Expression (3)

(Equation 60)
1.02 ≦ {Re ₍₆₃₀₎ / Rth ₍₆₃₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 1.90 Equation (5)

  Here, the absolute value of Re is preferably controlled within a preferable range depending on the mode of each liquid crystal layer. For example, in the case of the OCB and VA modes, the thickness is 20 to 110 nm, preferably 20 to 70 nm, and more preferably 35 to 70 nm.

The method for controlling Re of the support constituting the optical compensation film of the present invention is a method of stretching at a temperature of (Tg-30) to (Tg + 100) ° C., where (Tg) is the glass transition point of the support. Preferably used.
On the other hand, the transmittance of the optical compensation film is preferably 85% or more, and more preferably 90% or more. Even if the same material is used by applying the stretching method of the present invention, an optical compensation film having a higher transmittance can be obtained. According to the present inventor, it is estimated that by stretching at a very high temperature, impurities and the like in the polymer material are volatilized and the scattering factor in the film is reduced.

  In order to improve the color shift of the liquid crystal display device, it is also important to control Rth. The optical compensation film of the present invention can control Rth by coating an optically anisotropic layer satisfying the following formulas (11) and (12) on a support. The range of the following formula (11) is more preferably 1.15 to 1.35, and further preferably 1.20 to 1.33. Further, the range of the following formula (12) is more preferably 0.90 to 0.98, and still more preferably 0.92 to 0.98.

(Equation 61)
1.10 <Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ <1.35 Expression (11)

(Equation 62)
0.90 <Rth ₍₆₃₀₎ / Rth ₍₅₅₀₎ <1.00 Expression (12)

By coating the optically anisotropic layer, a preferable optical property control range allowed for the support is expanded, and the support can be produced using a more general method.
Further, the retardation (Rth) in the thickness direction of the entire support has a function for canceling the retardation of the liquid crystal layer in the thickness direction during black display, and therefore a preferable range depending on the mode of each liquid crystal layer. Is also different. For example, an OCB mode liquid crystal cell (for example, an OCB mode liquid crystal cell having a liquid crystal layer having a product Δn · d of thickness d (μm) and refractive index anisotropy Δn of 0.2 to 1.5 μm). When used for optical compensation, it is preferably 70 to 400 nm, more preferably 100 to 400 nm, and even more preferably 130 to 200 nm.

  Hereafter, each element which comprises the optical compensation film of this invention is demonstrated in detail.

<< cellulose acylate >>
As the raw material cotton of cellulose acylate selected as the material of the support of the present invention, a known raw material can be used (see, for example, JIII Journal of Technical Disclosure 2001-1745).
Cellulose acylate can also be synthesized by a known method (for example, see Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968)).
The average degree of polymerization of cellulose acylate is preferably 200 to 700, more preferably 250 to 500, and still more preferably 250 to 350.
The cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography.
The specific value of Mw / Mn is preferably 1.5 to 5.0, more preferably 2.0 to 4.5, and further preferably 3.0 to 4.0. preferable.

The acyl group of the cellulose acylate film of the present invention is not particularly limited, but an acetyl group or a propionyl group is preferably used, and an acetyl group is particularly preferable. The substitution degree of all acyl groups is preferably 2.7 to 3.0, more preferably 2.8 to 2.95. In the present embodiment, the substitution degree of the acyl group is a value calculated according to ASTM (AMERICA SOCIETY FOR TESTING AND MATERIALS) D817.
The acyl group is most preferably an acetyl group, and when cellulose acetate having an acyl group as the acetyl group is used, the degree of acetylation is preferably 57.0 to 62.5%, and 58.0 to 62.0. % Is more preferable. When the acetylation degree is within this range, Re does not become larger than a desired value due to the conveyance tension during casting, there is little in-plane variation, and there is little change in the retardation value due to temperature and humidity.
In particular, it is obtained by substituting the hydroxyl group of the glucose unit constituting the cellulose of the cellulose acylate film with an acyl group having 2 or more carbon atoms, and the substitution degree of the hydroxyl group at the 2-position of the glucose unit with the acyl group is DS2, 3 When the substitution degree of the hydroxyl group at the position is DS3 and the substitution degree of the acyl group at the 6-position hydroxyl group is DS6, if the following formula (I) and the following formula (II) are satisfied, the Re by temperature and humidity The fluctuation of the value is reduced, which is preferable.
(Equation 63)
2.0 ≦ DS2 + DS3 + DS6 ≦ 3.0... Formula (I)
(Equation 64)
DS6 / (DS2 + DS3 + DS6) ≧ 0.315... Formula (II)

[Stretching method]
The cellulose acylate film of the present invention exhibits a function by stretching as described above.
Below, the preferable extending | stretching method for this invention is demonstrated concretely.
The cellulose acylate film of the present invention is preferably stretched in the width direction when applied to a polarizing plate. As for this stretching method, for example, in JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, JP-A-4-298310, JP-A-11-48271, etc. Are listed.
In addition, the cellulose acylate film of the present invention is stretched under the conditions of 25 to 100 ° C., which is the Tg of the film, as described above.
The cellulose acylate film of the present invention may be stretched uniaxially or biaxially.
Moreover, the cellulose acylate film of the present invention can be stretched by a treatment during drying, and is particularly effective when a solvent remains. For example, the cellulose acylate film is stretched by adjusting the speed of the conveyance roller of the cellulose acylate film so that the take-up speed of the cellulose acylate film is higher than the peeling speed of the cellulose acylate film.
The cellulose acylate film can also be stretched by conveying the cellulose acylate film while holding it with a tenter and gradually widening the width of the tenter.
Furthermore, after the cellulose acylate film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine).
The stretch ratio of the cellulose acylate film of the present invention (ratio of increase due to stretching relative to the original length) is preferably 0.5 to 300%, more preferably 1 to 200%, and more preferably 1 to 100%. % Stretching is more preferred.

The cellulose acylate film of the present invention is preferably produced by sequentially or continuously performing a film-forming step by a solvent cast method and a drawing step for drawing the formed film, and the draw ratio is 1.2. It is preferable that it is not less than twice and not more than 1.8 times.
Moreover, the said extending process may be performed by 1 step | paragraph and may be performed by multiple steps | paragraphs. When it is performed in multiple stages, the product of the stretching ratios may be in the above range (1.2 to 1.8 times).

The stretching speed is preferably 5 to 1,000% / min, and more preferably 10 to 500% / min.
The stretching temperature is preferably 30 to 160 ° C, more preferably 70 to 150 ° C, and particularly preferably 85 to 150 ° C.
Furthermore, it is preferable that the said extending process is performed with a heat roll and / or a radiant heat source (IR heater etc.) and warm air. Moreover, you may provide a thermostat in order to improve the uniformity of temperature. When performing uniaxial stretching by roll stretching, it is preferable that L / W which is a ratio of the distance (L) between rolls and the film width (W) of a protective film is 2.0-5.0.

Furthermore, it is preferable to provide a preheating step before the stretching step, and heat treatment may be performed after the stretching step. The heat treatment temperature is preferably a temperature between 20 ° C. lower than the glass transition temperature (Tg) of the cellulose acetate film (support) and 10 ° C. higher than the glass transition temperature (Tg). The time is preferably 1 to 3 minutes.
The heating method may be zone heating, partial heating using an infrared heater, or slitting both ends of the cellulose acetate film during or at the end of the heating process. And it is preferable to collect | recover and reuse as a raw material the slit waste produced at this time.

  Regarding the tenter, in Japanese Patent Application Laid-Open No. 11-0777718, when the web is dried while the width is maintained by the tenter, the drying gas blowing method, the blowing angle, the wind speed distribution, the wind speed, the air volume, the temperature difference, the air volume difference, the upper and lower air blowing By appropriately controlling the use of air volume ratio and high specific heat drying gas, etc., it is possible to ensure quality prevention such as flatness when increasing the speed by the solution casting method or widening the web width. These techniques may be employed in the present invention.

  Japanese Patent Application Laid-Open No. 11-077782 describes a technique in which a stretched thermoplastic resin film is heat treated by providing a temperature gradient in the width direction of the film in the thermal relaxation process after the stretching process in order to prevent unevenness. This technique may be employed in the heat treatment step.

  Japanese Patent Laid-Open No. 4-204503 describes a technique for stretching the film so that the solvent content of the film is 2 to 10% based on the solid content in order to prevent the occurrence of unevenness, and this technique is employed in the present invention. May be.

  Japanese Patent Application Laid-Open No. 2002-248680 discloses that tenter clip biting width D ≦ (33 / (log stretch ratio × log volatile content)) in order to suppress curling due to the regulation of clip biting width. Describes a technique for suppressing curling and facilitating film conveyance after the stretching process, and this technique may be employed in the present invention.

  Japanese Patent Laid-Open No. 2002-337224 describes a technique for switching the tenter conveyance to the first half pin and the second half clip in order to achieve both high-speed soft film conveyance and stretching, and this technique is employed in the present invention. May be.

Japanese Patent Application Laid-Open No. 2002-187960 discloses that a cellulose ester dope solution is cast on a casting support for the purpose of easily improving the viewing angle characteristics and improving the viewing angle. The web (film) peeled off from the support for stretching is 1.0 to 4.0 times in at least one direction while the amount of residual solvent in the web is in the range of 100% by mass or less, particularly 10 to 100% by mass. An invention having optically biaxiality obtained by stretching is described.
As a further preferred embodiment of this technique, it is also described that the film is stretched by 1.0 to 4.0 times in at least one direction while the residual solvent amount in the web is in the range of 100% by mass or less, particularly 10 to 100% by mass. Has been.
In addition, as another stretching method of this technique, a difference in circumferential speed is applied to a plurality of rolls, and the roll is stretched in the longitudinal direction using the difference in circumferential speed between the rolls, and both ends of the web are fixed with clips or pins. A method of extending the gap between the pins in the direction of travel and extending in the vertical direction, a method of extending the width in the horizontal direction and extending in the horizontal direction, a method of extending the length and width simultaneously and extending in both the vertical and horizontal directions, a method of combining these, etc. Are also listed.
Furthermore, in the case of the so-called tenter method, it has been shown that it is preferable to drive the clip portion by the linear drive method because smooth stretching can be performed and the risk of breakage can be reduced. You may employ | adopt for invention.

JP-A-2003-014933 discloses that a resin and an additive are added in order to produce a retardation film with little additive bleed-out, no delamination phenomenon between layers, and excellent slipperiness and excellent transparency. A dope A containing an additive and an organic solvent, and a dope B containing no additive or a resin having a lower additive content than the dope A, an additive and an organic solvent, and the dope A being a core layer Then, after co-casting on the support so that the dope B becomes a surface layer, and evaporating the organic solvent until it becomes peelable, the web is peeled off from the support, and the resin film remains at the time of stretching. A technique is described in which the solvent is stretched 1.1 to 1.3 times in at least a uniaxial direction in the range of 3 to 50 mass%.
As a further preferred embodiment of this technique, the web is peeled from the support, and further stretched at least uniaxially in the uniaxial direction at a stretching temperature of 140 to 200 ° C., and a resin and an organic solvent are included. A dope B containing a dope A, a resin, fine particles, and an organic solvent is prepared, and the dope A is co-cast on the support so that the dope A becomes a core layer and the dope B becomes a surface layer, and is organic until it becomes peelable. After evaporating the solvent, the web is peeled from the support, and further stretched at least uniaxially 1.1 to 3.0 times in the range of 3 to 50% by mass of the residual solvent in the resin film during stretching. Further, the film is stretched at least uniaxially in the range of 140 to 200 ° C. in a uniaxial direction by 1.1 to 3.0 times, a dope A containing a resin, an organic solvent and an additive, and no additive or additive. Resin with less content than Dope A A dope B containing an agent and an organic solvent, and a dope C containing a resin, fine particles, and an organic solvent. Dope A is a core layer, dope B is a surface layer, and dope C is a surface layer opposite to dope B After co-casting on the support to evaporate the organic solvent until it can be peeled, the web is peeled from the support, and the amount of residual solvent in the resin film during stretching is 3 to 50 Stretching at least uniaxially 1.1 to 3.0 times in the range of mass%, stretching at least uniaxially 1.1 to 3.0 times in the range of stretching temperature 140 to 200 ° C., in dope A The additive amount is 1-30% by mass with respect to the resin, the additive amount in the dope B is 0-5% by mass with respect to the resin, and the additive is a plasticizer, UV absorber, or retardation control. Be an agent, organic solution in dope A and dope B There is described that it is preferable to use that it contains more than 50 wt% methylene chloride or methyl acetate with respect to the total organic solvents may be employed these techniques to the present invention.

Japanese Patent Application Laid-Open No. 2003-014933 discloses a transverse stretching machine called a tenter that stretches in the lateral direction by fixing both ends of the web with clips and pins and expanding the distance between the clips and pins in the lateral direction. It is described that can be preferably used.
In addition, in this publication, in order to stretch or shrink in the longitudinal direction, the simultaneous biaxial stretching machine is used to expand or contract the interval in the transport direction of clips and pins in the transport direction (vertical direction). It is also disclosed that
Further, in this publication, when the clip portion is driven by a linear drive method, it is possible to smoothly stretch and reduce the risk of breakage and the like, and a method of stretching in the longitudinal direction is preferable. It has been shown that a method can be used in which a difference in circumferential speed is applied to the belt and the roll is stretched in the longitudinal direction by utilizing the difference in circumferential speed of the roll.
In addition, in the publication, these stretching methods can be used in combination, and the stretching process is performed in two or more stages, such as (longitudinal stretching, lateral stretching, longitudinal stretching) or (longitudinal stretching, longitudinal stretching). However, these techniques may be applied to the present invention.

  Japanese Patent Laid-Open No. 2003-004374 discloses that in order to prevent foaming of the tenter-dried web, improve detachability, and prevent dust generation, hot air from the dryer is applied to both edges of the web. In order not to hit, a technique is described in which the width of the dryer is formed shorter than the width of the web, and this technique may be employed in the present invention.

  Japanese Patent Application Laid-Open No. 2003-019757 discloses that the tenter drying web is prevented from being foamed, the releasability is improved, and dust is prevented from being generated. The technique which provides a wind-shielding board inside a part is described, You may employ | adopt this technique for this invention.

  Japanese Patent Application Laid-Open No. 2003-053749 discloses that the thickness after drying of both ends of a film carried by a pin tenter is X (μm) in order to stably carry and dry the film. When the average thickness after drying is T (μm), T ≦ 60 satisfies 40 ≦ X ≦ 200, and 60 <T ≦ 120, 40+ (T−60) × 0.2 ≦ X ≦ 300 Is satisfied, and in 120 <T, a technique that satisfies 52+ (T−120) × 0.2 ≦ X ≦ 400 is described, and this technique may be employed in the present invention.

  Japanese Patent Laid-Open No. 2-182654 discloses a tenter device in which a heating chamber and a cooling chamber are provided in a dryer of a multistage tenter so that wrinkles are not generated in the multistage tenter. A separate cooling technique is described and may be employed in the present invention.

  Japanese Patent Application Laid-Open No. 9-073315 describes a technique for increasing the inner pin density and decreasing the outer pin density in the pin tenter pins in order to prevent web breakage, wrinkles, and conveyance failure. This technique may be employed in the present invention.

  Japanese Patent Laid-Open No. 9-085846 discloses a web-type side edge holding pin in a tenter drying device in order to prevent foaming of the web itself and adhesion of the web to the holding means in the tenter. A technology is described in which the pin is cooled to below the foaming temperature of the web with a cooler, and the pin immediately before the web is entrapped is cooled to the gelation temperature of the dope + 15 ° C. or less in the duct type cooler. You may employ | adopt for this invention.

  Japanese Patent Laid-Open No. 2003-103542 discloses a surface of a web that cools the insertion structure and contacts the insertion structure in the pin tenter in order to prevent pin tenter loss and improve foreign matter. A technique relating to a solution casting method for preventing the temperature from exceeding the gelling temperature of the web is described, and this technique may be employed in the present invention.

Japanese Patent Application Laid-Open No. 11-077718 discloses a web in a tenter in order to prevent deterioration in quality such as flatness when the speed is increased by a solution casting method or the width of the web is widened by a tenter. Is dried, the wind speed is 0.5-20 (40) m / s, the transverse temperature distribution is 10% or less, the web up-down air volume ratio is 0.2-1 and the dry gas ratio is 30-250 J /. A technique of Kmol is described. Furthermore, preferable drying conditions are disclosed depending on the amount of residual solvent in drying in the tenter.
Specifically, after the web is peeled off from the support, the angle of the air blown from the outlet is in the range of 30 to 150 ° with respect to the film plane until the amount of residual solvent in the web reaches 4% by mass. And when the wind speed distribution on the film surface located in the direction in which the drying gas is blown out is based on the upper limit value of the wind speed, the difference between the upper limit value and the lower limit value is within 20% of the upper limit value, When the blowout, drying the web, and the amount of residual solvent in the web is 70% by mass or more and 130% by mass or less, the wind speed of the dry gas blown out from the blowout dryer on the web surface is 0.5 m. / Sec or more and 20 m / sec or less, and when the residual solvent amount is less than 70% by mass and 4% by mass or more, the dry gas blown out at a wind speed of the drying gas of 0.5 m / sec or more and 40 m / sec or less. When the temperature distribution of the drying gas in the width direction of the web is based on the upper limit value of the gas temperature, the difference between the upper limit value and the lower limit value should be within 10% of the upper limit value. When the solvent amount is 4% by mass or more and 200% by mass or less, the air flow ratio q of the dry gas blown out from the blowout port of the blowout dryer located above and below the conveyed web may be 0.2 ≦ q ≦ 1. Are listed. Furthermore, as a preferred embodiment, at least one kind of gas is used for the drying gas, the average specific heat is 31.0 J / K · mol or more and 250 J / K · mol or less, and the room temperature contained in the drying gas during drying. And the concentration of the liquid organic compound is dried with a drying gas having a saturated vapor pressure of 50% or less, and these techniques may be employed in the present invention.

Japanese Patent Laid-Open No. 11-0777719 discloses that a tenter clip incorporates a heating part in a TAC (cellulose triacetate) film manufacturing apparatus in order to prevent deterioration of flatness and coating due to generation of contaminants. The technology is described.
As a further preferred aspect of this technique, a device for removing foreign matter generated at the contact portion between the clip and the web after the tenter clip releases the web and again supports the web is provided, and the gas to be injected Alternatively, the foreign matter is removed using a liquid and a brush, the residual amount at the time of contact between the clip or pin and the web is 12% by mass or more and 50% by mass or less, and the surface temperature of the contact portion between the clip or pin and the web is It is disclosed that it is 60 ° or more and 200 ° or less (more preferably 80 ° or more and 120 ° or less), and this technique may be employed in the present invention.

  In addition, in JP-A-11-090943, in order to improve flatness, improve quality deterioration due to tearing in the tenter, and increase productivity, in the tenter clip, an arbitrary transport length Lt ( m) and the total length Ltt (m) in the conveyance direction of the portion where the clip of the tenter having the same length as Lt holds the web Lr = Ltt / Lt is 1.0 ≦ Lr ≦ 1 .99 is described. Further, as a preferred embodiment, a technique is disclosed in which a portion for holding a web is arranged without a gap when viewed from the web width direction, and this technique may be adopted in the present invention.

Japanese Patent Application Laid-Open No. 11-090944 discloses a plastic film manufacturing apparatus in front of a tenter entrance in order to improve flatness deterioration and introduction instability caused by web sagging when the web is introduced into the tenter. Describes a technology having a sag suppressing device in the width direction of the web.
As a more preferable aspect of this technique, the sag suppressing device is a rotating roller that rotates in the direction range of 2 to 60 ° in the width direction, has an air intake device on the upper part of the web, and from below the web. Having a blower capable of blowing air is also disclosed, and this technique may be employed in the present invention.

  Japanese Patent Laid-Open No. 11-090945 discloses a TAC manufacturing method in which the web peeled from the support is angled with respect to the horizontal in order to prevent the deterioration of quality and sagging that hinders productivity. Is introduced to the tenter, and this technology may be employed in the present invention.

  JP-A-2000-289903 discloses a transporting apparatus that transports while applying tension in the width direction of the web when the film is peeled and has a solvent content of 50 to 12% by mass in order to produce a film having stable physical properties. , A web width detecting means, a web holding means, and a technique that has two or more variable bending points, calculates a web width from a detection signal in web width detection, and changes the position of the bending point This technique may be employed in the present invention.

Japanese Patent Application Laid-Open No. 2003-033933 discloses that the right and left sides of the web on the left and right sides near the entrance of the tenter are provided in order to improve clipping, prevent web breakage for a long period of time, and obtain a film with excellent quality. A web side edge curl prevention guide plate is disposed at least below the upper and lower side edges, and the web facing surface of the guide plate is arranged in the web conveying direction and the web. It is described that it is composed of a contact metal part.
As a further preferable aspect of this technique, the web contact resin portion of the guide plate facing the web is disposed on the upstream side in the web conveyance direction, and the web contact metal portion is disposed on the downstream side. The step between the resin part and the metal part for web contact (including the inclination) is within 500 μm, and the distance in the width direction in contact with the web of the resin part for web contact of the guide plate and the web of the metal part for web contact is The distance between the web contact resin part of the guide plate and the web contact metal part of the web contact direction in the web conveyance direction is 5 to 120 mm, respectively, and the web contact resin part of the guide plate is 2 to 150 mm. , Provided on a metal guide substrate by surface resin processing or resin coating, the web contact resin portion of the guide plate is made of a single resin, the left and right sides of the web The distance between the web facing surfaces of the guide plates arranged above and below at the side edge is 3 to 30 mm, and between the web facing surfaces of the upper and lower guide plates at the left and right side edges of the web. The distance is increased in the width direction of the web and inward at a rate of 2 mm or more per width of 100 mm, and the upper and lower guide plates have a length of 10 to 300 mm at the left and right side edges of the web, respectively. And both upper and lower guide plates are arranged so as to be displaced back and forth along the web conveyance direction, and the distance of deviation between the upper and lower guide plates is −200 to +200 mm, The web facing surface of the upper guide plate is made of only resin or metal, the web contact resin portion of the guide plate is made of Teflon (registered trademark), and the web contact gold The genus part is made of stainless steel, the web facing surface of the guide plate or the resin part for web contact provided on the surface, and / or the surface roughness of the metal part for web contact is 3 μm or less, Etc. are disclosed.
Further, it is also described that the installation position of the upper and lower guide plates for preventing web side edge curl generation is preferably between the peeling side end portion of the support and the tenter introduction portion, and more preferably installed near the tenter entrance. These techniques may be employed in the present invention.

Japanese Patent Laid-Open No. 11-048271 discloses a width stretching apparatus at the time when the web has a solvent content of 50 to 12% by mass in order to prevent the web from being cut or uneven during drying in the tenter. And a technique of applying a pressure of 0.2 to 10 KPa from both sides of the web with a pressurizing device when the solvent content of the web is 10% by mass or less.
As a further preferred embodiment of this technique, when applying pressure using a nip roll as a method of finishing applying tension when the solvent content is 4% by mass or more and applying pressure from both sides of the web (film), a pair of nip rolls is used. It is also disclosed that about 1 to 8 pairs are preferable, and that the temperature when pressurizing is preferably 100 to 200 ° C., and this technique may be adopted in the present invention.

Japanese Patent Application Laid-Open No. 2002-036266 discloses a preferred embodiment of a technique for obtaining a high-quality thin tack having a thickness of 20 to 85 μm as a difference in tension acting on the web along the conveying direction before and after the tenter. Is 8 N / mm ² or less, a preheating step for preheating the web after the peeling step, a stretching step for stretching the web using a tenter after the preheating step, and after the stretching step, And a relaxation step for relaxing by an amount smaller than the stretching amount in the stretching step, and the temperature T1 in the preheating step and the stretching step is set to (glass transition temperature Tg-60 of the film) or higher, and the relaxation step The temperature T2 is set to (T1-10) ° C. or lower, and the web stretch ratio in the stretching step is set to 0 to 30% in a ratio to the web width immediately before entering the stretching step. A web of stretch rate in the relaxation step, to -10 to 10%, etc. are disclosed, may be employed the technique of the present invention.

  JP 2002-225054 A discloses that the residual solvent amount of the web after peeling is 10% by mass for the purpose of being excellent in thinness and dry weight with a dry film thickness of 10 to 60 μm and small durability. In the meantime, the both ends of the web are gripped with clips, the drying shrinkage is suppressed by holding the width, and / or the stretching is performed in the width direction, and the plane orientation degree S represented by the following formula (III) Forming a film of 0.0008 to 0.0020 (in the following formula (III), Nx is the refractive index in the direction of the largest refractive index in the plane of the film, and Ny is perpendicular to Nx in the plane) The refractive index in the direction, Nz refers to the refractive index in the film thickness direction of the film.), The time from casting to peeling is set to 30 to 90 seconds, and the web after peeling in the width direction and / or the longitudinal direction Stretching, etc. are disclosed. The may also be employed in the present invention.

(Equation 65)
S = {(Nx + Ny) / 2} −Nz... Formula (III)

  Japanese Patent Application Laid-Open No. 2002-341144 discloses a solution film-forming method having a stretching process in which the mass concentration of a retardation increasing agent has a higher optical distribution as it approaches the center in the film width direction in order to suppress optical unevenness. This technique may be employed in the present invention.

In addition, in JP-A-2003-071863, in order to obtain a film in which fogging does not occur, the draw ratio in the width direction is preferably 0 to 100%. It is described that 20% is more preferable, and 8 to 15% is most preferable.
On the other hand, in the gazette, when used as a retardation film, 10 to 40% is more preferable, 20 to 30% is most preferable, Ro can be controlled by the draw ratio, and the higher draw ratio is, It is disclosed that the finished film is preferable because of its excellent flatness.
Furthermore, when the tenter is used, the residual solvent amount of the film is preferably 20 to 100% by mass at the start of the tenter, and drying is performed while the tenter is applied until the residual solvent amount of the film becomes 10% by mass or less. It is preferable that 5% by mass or less is more preferable.
Moreover, the drying temperature in the case of performing a tenter is preferably 30 to 150 ° C., more preferably 50 to 120 ° C., most preferably 70 to 100 ° C. However, it is also disclosed that the higher the drying temperature, the better the flatness of the film, and this technique may be adopted in the present invention.

Japanese Patent Laid-Open No. 2002-248639 discloses that a cellulose ester solution is continuously cast on a support in order to reduce vertical and horizontal dimensional fluctuations during storage under high temperature and high humidity conditions. In the method for producing a film to be peeled and dried, a technique for drying so that the drying shrinkage rate satisfies the following formula (IV) is described.
As a more preferred embodiment of this technique, when the residual solvent amount of the cellulose ester film after peeling is in the range of 40 to 100% by mass, at least the residual solvent amount is set to 30 while gripping both ends of the cellulose ester film by tenter conveyance. The amount of residual solvent at the tenter conveyance entrance of the cellulose ester film after peeling is 40 to 100 mass%, the amount of residual solvent at the exit is 4 to 20 mass%, and the cellulose ester by tenter conveyance It is disclosed that the tension for transporting the film increases from the entrance to the exit of the tenter transport, the tension for transporting the cellulose ester film by the tenter transport and the tension in the width direction of the cellulose ester film are substantially equal. This technique may be employed in the present invention.

(Equation 66)
0 ≦ dry shrinkage (%) ≦ 0.1 × residual solvent amount when peeling (%) ··· formula (IV)

  Japanese Patent Application Laid-Open No. 2000-239403 discloses a residual solvent ratio X at the time of peeling and a residual value when introduced into a tenter in order to obtain a film having a thin film thickness and excellent optical isotropy and flatness. It is disclosed that the film formation is performed with the relationship with the solvent ratio Y being in the range of 0.3X ≦ Y ≦ 0.9X, and this technique may be employed in the present invention.

  JP 2002-286933 A includes a method of stretching a film to be formed by casting, a method of stretching under heating conditions and a method of stretching under solvent-containing conditions. When stretching, it is preferable to stretch at a temperature below the glass transition point of the resin. On the other hand, when stretching a cast film under solvent-impregnated conditions, the once dried film is re-solvent. It is disclosed that the film can be impregnated with a solvent to be stretched, and this technique can be employed in the present invention.

<< Retardation raising agent >>
[Retardation increasing agent for controlling Re]
In order to control the absolute value of Re of the protective film (optical compensation film) of the present invention, a compound having a maximum absorption wavelength (λmax) shorter than 250 nm in the ultraviolet absorption spectrum of the solution is used as a retardation increasing agent. Is preferred.
By using such a compound, the absolute value can be controlled without substantially changing the wavelength dependency of Re in the visible region.
In addition, from the viewpoint of the function of the retardation increasing agent, a rod-like compound is preferable, preferably having at least one aromatic ring, and more preferably having at least two aromatic rings.
The rod-shaped compound preferably has a linear molecular structure. The linear molecular structure means that the molecular structure of the rod-shaped compound is linear in the thermodynamically most stable structure.
The thermodynamically most stable structure can be obtained by crystal structure analysis or molecular orbital calculation.
For example, molecular orbital calculation can be performed using molecular orbital calculation software (eg, WinMOPAC2000, manufactured by Fujitsu Limited) to obtain a molecular structure that minimizes the heat of formation of a compound.
Here, the molecular structure being linear means that the angle of the molecular structure is 140 ° or more in the thermodynamically most stable structure obtained by calculation as described above.
The rod-like compound preferably exhibits liquid crystallinity. More preferably, the rod-like compound exhibits liquid crystallinity upon heating (has thermotropic liquid crystallinity). The liquid crystal phase is preferably a nematic phase or a smectic phase.

As a preferable compound of the rod-like compound, a compound described in JP-A-2004-4550 can be adopted, but is not limited thereto. Two or more rod-shaped compounds having a maximum absorption wavelength (λmax) shorter than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination.
The rod-like compound can be synthesized with reference to methods described in literature. As literature, Mol. Cryst. Liq. Cryst. 53, 229 pages (1979), 89, 93 pages (1982), 145, 111 pages (1987), 170 pages, 43 pages (1989), J. Am. Am. Chem. Soc. 113, 1,349 (1991), 118, 5,346 (1996), 92, 1,582 (1970); Org. Chem. 40, 420 (1975), Tetrahedron, 48, 16, 3,437 (1992).
In addition, it is preferable that the addition amount of a retardation raising agent is 0.1-30 mass% of the quantity of a polymer, and it is still more preferable that it is 0.5-20 mass%.

[Retardation increasing agent for controlling Rth]
In order to express desired Rth, it is preferable to use a retardation increasing agent.
Here, “retardation increasing agent” in the present specification was prepared in exactly the same manner except that the Re retardation value measured at a wavelength of 550 nm of a cellulose acylate film containing an additive did not contain the additive. It means an “additive” that is 20 nm or more higher than the Rth retardation value measured at a wavelength of 550 nm of the cellulose acylate film.
The increase in retardation value is preferably 30 nm or more, more preferably 40 nm or more, and further preferably 60 nm or more.

The retardation increasing agent is preferably a compound having at least two aromatic rings. The retardation increasing agent is preferably used in the range of 0.01 to 20 parts by mass, more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the polymer. It is still more preferable to use in the range of -5 mass parts, and it is especially preferable to use in the range of 0.5-2 mass parts. Two or more retardation increasing agents may be used in combination.
The retardation increasing agent preferably has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.
The retardation increasing agent for controlling Rth preferably does not affect Re expressed by stretching, and is preferably a discotic compound.
The discotic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring, and the aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).

The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds.
As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.

  As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, In particular, a 1,3,5-triazine ring is preferably used. Specifically, for example, compounds disclosed in JP-A No. 2001-166144 are preferably used.

  An aromatic compound is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acylates. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass and more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate. Two or more kinds of compounds may be used in combination.

[Control of Rth by optically anisotropic layer]
As a method for controlling Rth without affecting Re expressed by stretching, a method of coating an optically anisotropic layer such as a liquid crystal layer is preferably used.
Specific examples of the liquid crystal layer include a method of aligning a discotic liquid crystal so that the angle between the disc surface and the optical compensation film surface is within 5 ° (described in JP-A-10-32166), rod-like There is a method (described in JP-A No. 2000-304932) in which the liquid crystal is aligned so that the angle between the major axis and the surface of the optical compensation film is within 5 °.

<Application to optical compensation film>
Next, an optical compensation film for realizing this optical compensation will be specifically described.
The optical compensation film of the present invention contributes to the expansion of the viewing angle contrast and the reduction of the color shift depending on the viewing angle of the liquid crystal display device, particularly the OCB mode and VA mode liquid crystal display device.
The optical compensation film of the present invention may be disposed between the observer-side polarizing plate and the liquid crystal cell, or may be disposed between the rear-side polarizing plate and the liquid crystal cell, or may be disposed on both. Also good.
For example, it can be incorporated into the liquid crystal display device as an independent member, or a protective film that protects the polarizing film can be provided with optical characteristics and function as a transparent film. It can also be incorporated inside the display device.
The optical compensation film of the present invention can also have at least two layers of the optical compensation film of the present invention and an optically anisotropic layer having other optical properties.

[Second optically anisotropic layer (hybrid orientation anisotropic layer)]
The optical compensation film of the present invention has at least one optically anisotropic layer formed from a liquid crystalline compound in accordance with the liquid crystal system to be used. The optically anisotropic layer may be formed directly on the surface of the optical compensation film, or may be formed on the alignment film by forming an alignment film on the optical compensation film. Moreover, it is also possible to produce the optical compensation film of the present invention by transferring the liquid crystalline compound layer formed on another substrate onto the optical compensation film using an adhesive, an adhesive, or the like.

  Examples of the liquid crystalline compound used for forming the optically anisotropic layer include a rod-like liquid crystalline compound and a discotic liquid crystalline compound (hereinafter, the discotic liquid crystalline compound may be referred to as a “discotic liquid crystalline compound”). The rod-like liquid crystal compound and the discotic liquid crystal compound may be a high-molecular liquid crystal or a low-molecular liquid crystal. In addition, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, when a low-molecular liquid crystalline compound is used for the production of the optically anisotropic layer, the optically anisotropic layer In the process of forming, the compound may be cross-linked and no longer exhibits liquid crystallinity.

[Bar-shaped liquid crystalline compound]
Examples of the rod-like liquid crystalline compound that can be used in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, and cyano-substituted phenylpyrimidines. Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystalline compound includes a metal complex. A liquid crystal polymer containing a rod-like liquid crystal compound in a repeating unit can also be used. In other words, the rod-like liquid crystalline compound may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline compounds, Chapter 4, Chapter 7 and Chapter 11 of Quarterly Chemical Review Volume 22 “Chemicals of Liquid Crystals” (1994, The Chemical Society of Japan) and Liquid Crystal Device Handbook (Japan Society for the Promotion of Science) 142 Chapter), described in Chapter 3.

The birefringence of the rod-like liquid crystalline compound used in the present invention 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 the alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and still more preferably an ethylenically unsaturated polymerizable group.

[Discotic liquid crystalline compounds]
Examples of discotic liquid crystalline compounds 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.

  The discotic liquid crystalline compound exhibits liquid crystallinity with a structure in which a linear alkyl group, an alkoxy group or a substituted benzoyloxy group is radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule. Also included are compounds. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation.

  As described above, when an optically anisotropic layer is formed from a liquid crystalline compound, the compound finally contained in the optically anisotropic layer no longer needs to exhibit liquid crystallinity. For example, a low-molecular discotic liquid crystalline compound has a group that reacts with heat or light, and the group reacts with heat or light to polymerize or crosslink to increase the molecular weight. When a layer is formed, the compound contained in the optically anisotropic layer may no longer have liquid crystallinity. Preferred examples of the discotic liquid crystalline compound are described in JP-A-8-50206. Moreover, about superposition | polymerization of a discotic liquid crystalline compound, Unexamined-Japanese-Patent No. 8-27284 has description.

  In order to fix the discotic liquid crystalline compound by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline compound. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, it is preferable to introduce a linking group between the discotic core and the polymerizable group.

  In the present invention, in the optically anisotropic layer, the rod-like compound or the molecule of the discotic compound is fixed in an oriented state. The orientation average direction of the molecular symmetry axis of the liquid crystal compound at the interface on the optical compensation film side has an intersection angle of about 45 ° with the slow axis in the plane of the optical compensation film. In the present specification, “approximately 45 °” means an angle in a range of 45 ° ± 5 °, preferably 42 to 48 °, and more preferably 43 to 47 °.

The orientation average direction of the molecular symmetry axis of the liquid crystal compound can be generally adjusted by selecting a material of the liquid crystal compound or the alignment film or by selecting a rubbing treatment method.
In the present invention, for example, in the case of producing an optical compensation film for the OCB method, an alignment film for forming an optically anisotropic layer is produced by rubbing treatment and rubbed in a direction of 45 ° with respect to the slow axis of the optical compensation film By processing, an optically anisotropic layer in which the orientation average direction of the molecular symmetry axis of the liquid crystalline compound at least at the cellulose acylate film interface is 45 ° with respect to the slow axis of the cellulose acylate film is formed. Can do.
For example, the optical compensation film of the present invention can be continuously produced by using the long optical compensation film of the present invention whose slow axis is perpendicular to the longitudinal direction.
Specifically, a coating liquid for forming an alignment film is continuously applied to the surface of the long optical compensation film to produce a film, and then the surface of the film is continuously applied in the longitudinal direction. An alignment film is prepared by rubbing in the direction of °, and then a coating liquid for forming an optically anisotropic layer containing a liquid crystalline compound is continuously applied onto the prepared alignment film. By aligning the molecules and fixing them in that state, an optically anisotropic layer can be produced, and a long optical compensation film can be produced continuously. The optical compensation film produced in a long shape is cut into a desired shape before being incorporated into the liquid crystal display device.

  In addition, with respect to the orientation average direction of the molecular symmetry axis on the surface side (air side) of the liquid crystalline compound, the orientation average direction of the molecular symmetry axis of the liquid crystalline compound on the air interface side is substantially about the slow axis of the optical compensation film. The angle is preferably 45 °, more preferably 42 to 48 °, and still more preferably 43 to 47 °. In general, the orientation average direction of the molecular symmetry axis of the liquid crystal compound on the air interface side can be adjusted by selecting the type of the liquid crystal compound or the additive used together with the liquid crystal compound. Examples of the additive used together with the liquid crystal compound include a plasticizer, a surfactant, a polymerizable monomer and a polymer. Similarly to the above, the degree of change in the orientation direction of the molecular symmetry axis can be adjusted by selecting the liquid crystal compound and the additive. In particular, regarding the surfactant, it is preferable that the surface tension control of the coating solution is compatible.

  The plasticizer, surfactant and polymerizable monomer used together with the liquid crystal compound are compatible with the discotic liquid crystal compound and may change the tilt angle of the liquid crystal compound or do not inhibit the alignment. preferable. A polymerizable monomer (eg, a compound having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) is preferred. 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 liquid crystal compound. In addition, when a monomer having 4 or more polymerizable reactive functional groups is mixed and used, adhesion between the alignment film and the optically anisotropic layer can be improved.

When a discotic liquid crystalline compound is used as the liquid crystalline compound, it is preferable to use a polymer that has a certain degree of compatibility with the discotic liquid crystalline compound and can change the tilt angle of the discotic liquid crystalline compound.
A cellulose ester can be mentioned as an example of a polymer. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. In order not to inhibit the orientation of the discotic liquid crystalline compound, the amount of the polymer added is preferably in the range of 0.1 to 10% by mass, preferably 0.1 to 8% by mass with respect to the discotic liquid crystalline compound. More preferably, it is in the range of 0.1 to 5% by mass.
The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound is preferably 70 to 300 ° C, and more preferably 70 to 170 ° C.

  In the present invention, the “other” optically anisotropic layer described above has at least in-plane optical anisotropy. The in-plane retardation Re of the optically anisotropic layer is preferably 3 to 300 nm, more preferably 5 to 200 nm, and still more preferably 10 to 100 nm. The retardation Rth in the thickness direction of the optically anisotropic layer is preferably 20 to 400 nm, and more preferably 50 to 200 nm. The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and still more preferably 1 to 10 μm.

[Alignment film]
The optical compensation film of the present invention may have an alignment film between the support and the optically anisotropic layer. In addition, the alignment film is used only when the optically anisotropic layer is prepared, and after forming the optically anisotropic layer on the alignment film, only the optically anisotropic layer is used as the optical compensation film (support) of the present invention. ) May be transferred onto.
In the present invention, the alignment film is preferably a layer made of a crosslinked polymer. The polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. The alignment film is formed by reacting a polymer having a functional group or a polymer having a functional group introduced therein with light, heat, pH change, or the like; or a cross-linking agent that is a highly reactive compound Can be formed by introducing a linking group derived from a cross-linking agent between polymers to cross-link between the polymers.

The alignment film made of a crosslinked polymer can be usually formed by applying a coating solution containing the polymer or a mixture of a polymer and a crosslinking agent on a support, followed by heating.
In the rubbing process described later, it is preferable to increase the degree of cross-linking in order to suppress dust generation in the alignment film. The value (1- (Ma / Mb)) obtained by subtracting 1 from the ratio (Ma / Mb) of the amount (Ma) of the crosslinking agent remaining after crosslinking to the amount (Mb) of the crosslinking agent added to the coating solution. When Mb)) is defined as the degree of crosslinking, the degree of crosslinking is preferably 50 to 100%, more preferably 65 to 100%, and even more preferably 75 to 100%.

In the present invention, the polymer used for the alignment film may be either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent. Of course, a polymer having both functions can also be used. Examples of the polymer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol acrylamide), Styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose And polymers such as gelatin, polyethylene, polypropylene and polycarbonate, and compounds such as silane coupling agents. Examples of preferred polymers are water-soluble polymers such as poly (N-methylacrylamide), carboxymethyl cellulose, gelatin, polyvir alcohol and modified polyvinyl alcohol, and further gelatin, polyvir alcohol and modified polyvinyl alcohol. Are preferable, and in particular, polyvinyl alcohol and modified polyvinyl alcohol can be mentioned.
When the polyvinyl alcohol and the modified polyvinyl alcohol are directly coated on the optical compensation film (especially cellulose acylate film) of the present invention, a hydrophilic undercoat layer is provided, or saponification described in the pamphlet of International Publication No. WO2002 / 046809 A method of applying the treatment is preferably used.

Among the above polymers, polyvinyl alcohol or modified polyvinyl alcohol is preferable.
Examples of the polyvinyl alcohol include those having a saponification degree of 70 to 100%, generally those having a saponification degree of 80 to 100%, and more preferably those having a saponification degree of 82 to 98%. The degree of polymerization is preferably in the range of 100 to 3,000.
Examples of the modified polyvinyl alcohol include those modified by copolymerization (for example, COONa, Si (OX) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ COO, SO ₃ Na, C ₁₂ H _25, etc. Modified by chain transfer (for example, COONa, SH, SC ₁₂ H _25, etc. are introduced as modifying groups), modified by block polymerization (modified groups such as COOH, for example) , CONH ₂ , COOR, C ₆ H _5, etc. are introduced). The degree of polymerization is preferably in the range of 100 to 3,000.
Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100% is preferable, and unmodified, modified polyvinyl alcohol, or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% is more preferable.
The polyvinyl alcohol is preferably introduced with a crosslinking / polymerization active group in order to provide adhesion between the optical compensation film and the optically anisotropic layer made of liquid crystal. This is described in detail in Japanese Patent No. 338913.
In the case of using a hydrophilic polymer such as polyvinyl alcohol for the alignment film, it is preferable to control the water content from the viewpoint of the degree of hardening, preferably 0.4 to 2.5%, and 0.6 to 1 More preferably, it is 6%. The water content can be measured with a commercially available Karl Fischer moisture content measuring device. The alignment film preferably has a thickness of 10 μm or less.

<< Adhesive >>
The adhesive between the polarizing film and the protective film is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm, and particularly preferably 0.05 to 5 μm after drying.

<< Integrated manufacturing process of polarizing film and transparent protective film >>
The polarizing plate that can be used in the present invention has a drying step in which the polarizing film is stretched and then contracted to reduce the volatile content rate, but after drying or pasting a transparent protective film on at least one side during drying, It is preferable to have a post-heating step.
In an embodiment in which the transparent protective film also serves as a support for the optically anisotropic layer functioning as a transparent film, a transparent support having a transparent protective film on one side and an optically anisotropic layer on the other side is pasted. After combining, it is preferable to post-heat.
As a specific attaching method, during the film drying process, the transparent protective film is attached to the polarizing film using an adhesive while holding both ends, and then both ends are cut off, or after drying, from both end holding parts There is a method in which the polarizing film is released, both ends of the film are cut off, and then a transparent protective film is applied.
As a method for cutting off the ears, general techniques such as a method of cutting with a cutter such as a blade or a method of using a laser can be used.
After bonding, it is preferable to heat in order to dry the adhesive and improve the polarization performance.
The heating conditions vary depending on the adhesive, but in the case of an aqueous system, 30 ° C or higher is preferable, 40 to 100 ° C is more preferable, and 50 to 90 ° C is still more preferable. It is more preferable in terms of performance and production efficiency that these processes are manufactured in a consistent line.

<Performance of polarizing plate>
The optical properties and durability (short-term and long-term storage stability) of a transparent protective film, a polarizer (polarizing film), and a transparent support, which are related to the present invention, are commercially available super high contrast products (for example, It is preferable to have equivalent or better performance.
Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization {(Tp−Tc) / (Tp + Tc)} ^1/2 ≧ 0.9995 (where Tp is parallel transmittance, and Tc is orthogonal transmission) The change rate of the light transmittance before and after being left in an atmosphere of 60 ° C. and a humidity of 90% RH for 500 hours and 80 ° C. in a dry atmosphere for 500 hours is 3% or less based on the absolute value, Further, it is preferably 1% or less, and the rate of change of the polarization degree is preferably 1% or less, more preferably 0.1% or less based on the absolute value.

(Liquid crystal display device)
The polarizing plate obtained by laminating the optical compensation film or the optical compensation film and the polarizing film is advantageously used for a liquid crystal display device, particularly a transmissive liquid crystal display device. The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates arranged on both sides thereof.
The polarizing plate includes a polarizing film and at least two transparent protective films disposed on both sides of the polarizing film. Further, the liquid crystal cell carries a liquid crystal between two electrode substrates.
One optical compensation film of the present invention is disposed between the liquid crystal cell and one polarizing plate, or two optical compensation films are disposed between the liquid crystal cell and both polarizing plates.
The polarizing plate of the present invention may be used as at least one of the two polarizing plates disposed on both sides of the liquid crystal cell. In this case, the polarizing plate of the present invention is arranged so that the optical compensation film is on the liquid crystal cell side. ,
The liquid crystal cell is preferably in VA mode, OCB mode, IPS mode, or TN mode.
In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). (2) Liquid crystal cell (SID97, Digest of tech. Papers (Proceedings) 28 (1997) 845 in which the VA mode is converted into a multi-domain (for MVA mode) in order to expand the viewing angle. (3) A liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary Collection 58- 59 (1998)), and (4) SURVAIVAL mode liquid crystal cells (announced at LCD International 98).
The OCB mode liquid crystal cell is a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell.
A liquid crystal display device using a bend alignment mode liquid crystal cell is disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function.
For this reason, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.
In a TN mode liquid crystal cell, rod-like liquid crystalline molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °.
The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (Substitution degree: 2.81 Acetylation degree: 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... ... 630 parts by mass, methanol (second solvent) ... 95 parts by mass
-Retardation increasing agent shown in the following structural formula (A) ... 3 parts by mass

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and further dried with 135 ° C. drying air for 20 minutes to produce a film. Thereafter, this film was uniaxially stretched to 120% under a temperature condition of 190 ° C. to prepare a support. In addition, Tg of the used cellulose acylate film is 148 degreeC.
The thickness of the produced support was 80 μm. The retardation value (Re) at a wavelength of 550 nm after being conditioned for 2 hours in an environment of 25 ° C. and 55% RH was 41.0 nm. Moreover, it was 110 nm when the retardation value (Rth) in wavelength 550nm was measured.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 630 nm were measured and found to be 29 nm and 51 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 630nm was measured, they were 112nm and 103nm, respectively. The results are shown in Table 1.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle with respect to the pure water of the treated surface of this support was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol represented by the following structural formula (B): 10 parts by mass, water: ······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3 manufactured by Sankyo Chemical Co., Ltd.) ...... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of optically anisotropic layer >>
On the alignment film, a film containing a discotic liquid crystal having the following composition is rotated at a speed of 20 m / min by rotating a # 2.4 wire bar at 391 rotations in the same direction as the film conveyance direction. The film was continuously applied to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the following structural formula (C) ... 32.6 parts by mass-Compound represented by the following structural formula (D) (additive for orienting the disc surface within 5 degrees) ) ... 0.1 parts by mass / Ethylene oxide-modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) (Made by Yakuhin Co., Ltd.) ········ 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Corp.) ··· 1.1 parts by mass
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, in the state where the surface temperature of the film is about 130 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 75nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Example 2)
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (substitution degree 2.77, acetylation degree 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... 610 parts by mass / methanol (second solvent) ... 90 parts by mass
-Retardation increasing agent shown in the structural formula (A)-0.5 mass part

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and further dried with 135 ° C. drying air for 20 minutes to produce a film. Thereafter, this film was uniaxially stretched to 130% under a temperature condition of 130 ° C. to prepare a support. In addition, Tg of the used cellulose acylate is 148 degreeC.
The thickness of the produced support was 80 μm. The retardation value (Re) at a wavelength of 550 nm after humidity conditioning for 2 hours in an environment of 25 ° C. and 55% RH was 52.0 nm. Further, the retardation value (Rth) at a wavelength of 550 nm was measured and found to be 90 nm.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 630 nm were measured and found to be 42 nm and 57 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 630nm was measured, they were 79nm and 96nm, respectively. The results are shown in Table 1.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of this film with pure water was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol shown in the above structural formula (B) ・ ・ ・ ・ ・ ・ 10 parts by mass ・ Water ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3 manufactured by Sankyo Chemical Co., Ltd.) ...... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of optically anisotropic layer >>
A coating solution containing a discotic liquid crystal having the following composition is rotated on the alignment film by rotating a # 2.8 wire bar at 391 rotations in the same direction as the film conveyance direction. It applied continuously to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the above structural formula (C) ... 32.6 parts by mass-Compound represented by the above structural formula (D) (additive for orienting the disk surface within 5 degrees) ) ... 0.1 parts by mass / ethylene oxide modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) (Manufactured by Yakuhin Co., Ltd.) ······· 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Corp.) ··· 1.1 parts by mass
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, in the state where the surface temperature of the film is about 130 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 95nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Example 3)
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (substitution degree 2.77, acetylation degree 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... 610 parts by mass / methanol (second solvent) ... 90 parts by mass
-Retardation increasing agent represented by the following structural formula (E): 2.0 parts by mass

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and further dried with 135 ° C. drying air for 20 minutes to produce a film. Thereafter, the film was uniaxially stretched to 125% under a temperature condition of 155 ° C. to prepare a support. In addition, Tg of the used cellulose acylate is 148 degreeC.
The thickness of the produced support was 55 μm. The retardation value (Re) at a wavelength of 550 nm after being conditioned for 2 hours in an environment of 25 ° C. and 55% RH was 55.0 nm. Moreover, it was 90 nm when the retardation value (Rth) in wavelength 550nm was measured.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 630 nm were measured and found to be 44 nm and 60 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 630nm was measured, they were 85nm and 95nm, respectively. The results are shown in Table 1.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of this film with pure water was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol shown in the above structural formula (B) ・ ・ ・ ・ ・ ・ 10 parts by mass ・ Water ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3 manufactured by Sankyo Chemical Co., Ltd.) ...... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The thickness of the alignment film after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of optically anisotropic layer >>
A coating solution containing a discotic liquid crystal having the following composition on the alignment film is rotated at a speed of 20 m / min by rotating a # 2.8 wire bar in 391 rotations in the same direction as the film conveyance direction. The film was continuously applied to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the above structural formula (C) ... 32.6 parts by mass-Compound represented by the above structural formula (D) (additive for orienting the disk surface within 5 degrees) ) ... 0.1 parts by mass / ethylene oxide modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) (Manufactured by Yakuhin Co., Ltd.) ······· 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Corp.) ··· 1.1 parts by mass
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried. The discotic liquid crystal compound was aligned by heating for 90 seconds. Next, in the state where the surface temperature of the film is about 130 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 95nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

Example 4
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (substitution degree 2.77, acetylation degree 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... 610 parts by mass / methanol (second solvent) ... 90 parts by mass
-Retardation increasing agent shown in the above structural formula (E) ... 0.6 parts by mass

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and further dried with 135 ° C. drying air for 20 minutes to produce a film. Thereafter, this film was uniaxially stretched to 135% under a temperature condition of 130 ° C. to prepare a support. In addition, Tg of the used cellulose acylate is 148 degreeC.
The thickness of the produced support was 55 μm. The retardation value (Re) at a wavelength of 550 nm after being conditioned for 2 hours in an environment of 25 ° C. and 55% RH was 52.0 nm. Further, the retardation value (Rth) at a wavelength of 550 nm was measured and found to be 90 nm.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 630 nm were measured and found to be 40 nm and 59 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 630nm was measured, they were 77nm and 98nm, respectively. The results are shown in Table 1.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of this film with pure water was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol shown in the above structural formula (B) ・ ・ ・ ・ ・ ・ 10 parts by mass ・ Water ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3 manufactured by Sankyo Chemical Co., Ltd.) ...... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The thickness of the alignment film after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of optically anisotropic layer >>
A coating solution containing a discotic liquid crystal having the following composition is rotated on the alignment film by rotating a # 2.8 wire bar at 391 rotations in the same direction as the film conveyance direction. It applied continuously to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the above structural formula (C) ... 32.6 parts by mass-Compound represented by the above structural formula (D) (additive for orienting the disk surface within 5 degrees) ) ... 0.1 parts by mass / ethylene oxide modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) (Manufactured by Yakuhin Co., Ltd.) ······· 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Corp.) ··· 1.1 parts by mass
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, in the state where the surface temperature of the film is about 130 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 95nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Example 5)
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (Substitution degree: 2.81 Acetylation degree: 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... ... 630 parts by mass, methanol (second solvent) ... 95 parts by mass
-Retardation increasing agent shown in the structural formula (A)-2.5 parts by mass

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and further dried with 135 ° C. drying air for 20 minutes to produce a film. Thereafter, this film was uniaxially stretched to 130% under a temperature condition of 200 ° C. to prepare a support. In addition, Tg of the used cellulose acylate is 148 degreeC.
The thickness of the produced support was 80 μm. The retardation value (Re) at a wavelength of 550 nm after humidity conditioning for 2 hours in an environment of 25 ° C. and 55% RH was 69.0 nm. Moreover, it was 70 nm when the retardation value (Rth) in wavelength 550nm was measured.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 630 nm were measured and found to be 64 nm and 76 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 630nm was measured, they were 78nm and 68nm, respectively. The results are shown in Table 1.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of this film with pure water was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol shown in the above structural formula (B) ・ ・ ・ ・ ・ ・ 10 parts by mass ・ Water ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3 manufactured by Sankyo Chemical Co., Ltd.) ...... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of optically anisotropic layer >>
A coating solution containing a discotic liquid crystal having the following composition is rotated on the alignment film by rotating a # 2.0 wire bar in the same direction as the film conveyance direction at 391 rotations, and the film is conveyed at 20 m / min. It applied continuously to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the above structural formula (C) ... 32.6 parts by mass-Compound represented by the above structural formula (D) (additive for orienting the disk surface within 5 degrees) ) ... 0.1 parts by mass / ethylene oxide modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) (Manufactured by Yakuhin Co., Ltd.) ······· 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Corp.) ··· 1.1 parts by mass
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, in the state where the surface temperature of the film is about 130 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 50nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Comparative Example 1)
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (Substitution degree: 2.81 Acetylation degree: 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... ... 630 parts by mass, methanol (second solvent) ... 95 parts by mass, as shown in the following structural formula (F) Retardation increasing agent ... 3 parts by mass

The obtained dope was cast using a casting machine having a band having a width of 2 m and a length of 65 m. After the film surface temperature on the band reached 40 ° C., the film was dried for 1 minute, peeled off, and further dried with 135 ° C. drying air for 20 minutes to produce a film. Thereafter, this film was uniaxially stretched to 120% under a temperature condition of 185 ° C. to prepare a support. In addition, Tg of the used cellulose acylate is 138 degreeC.
The thickness of the produced support was 80 μm. The retardation value (Re) at a wavelength of 550 nm after humidity conditioning for 2 hours in an environment of 25 ° C. and 55% RH was 80 nm. The retardation value (Rth) at a wavelength of 550 nm was measured and found to be 65 nm.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 630 nm were measured and found to be 83 nm and 77 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 630nm was measured, they were 66nm and 64nm, respectively. The results are shown in Table 1.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of this film with pure water was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol shown in the above structural formula (B) ・ ・ ・ ・ ・ ・ 10 parts by mass ・ Water ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3, Sankyo Chemical Co., Ltd.) ... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of Another Optical Anisotropic Layer >>
A coating solution containing a discotic liquid crystal having the following composition is rotated on the alignment film by rotating a # 4.0 wire bar at 391 rotations in the same direction as the film conveyance direction. It applied continuously to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the above structural formula (C) ... 32.6 parts by mass-Compound represented by the above structural formula (D) (additive for orienting the disk surface within 5 degrees) ) ... 0.1 parts by mass / ethylene oxide modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) (Manufactured by Yakuhin Co., Ltd.) ······· 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Corp.) ··· 1.1 parts by mass
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, in the state where the surface temperature of the film is about 130 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound is aligned. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 120nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Comparative Example 2)
<Production of optical compensation film>
<< Preparation of support >>
A cellulose acylate film was produced under the same conditions as in Example 2.

A 1.0N potassium hydroxide solution (solvent: water / isopropyl alcohol / propylene glycol = 69.2 parts by mass / 15 parts by mass / 15.8 parts by mass) is applied to the band surface side of the produced support at 10 mL / m ^2. After applying and holding at about 40 ° C. for 30 seconds, the alkaline solution was scraped off, washed with pure water, and water droplets were removed with an air knife. Then, it dried at 100 degreeC for 15 second. The contact angle of this film with pure water was determined to be 42 °.

<< Preparation of alignment film >>
On this support, an alignment film coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. The film was dried with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds to produce an alignment film.

[Alignment film coating solution composition]
・ Modified polyvinyl alcohol shown in the above structural formula (B) ・ ・ ・ ・ ・ ・ 10 parts by mass ・ Water ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・······· 371 parts by mass · Methanol ···················································· Cross-linking agent) ... 0.5 parts by mass
・ Citrate ester (AS3 manufactured by Sankyo Chemical Co., Ltd.) ...... 0.35 parts by mass

  Drying was performed at 25 ° C. for 60 seconds, 60 ° C. warm air for 60 seconds, and 90 ° C. warm air for 150 seconds. The alignment film thickness after drying was 1.1 μm. Further, the surface roughness of the alignment film was measured with an atomic force microscope (AFM: Atomic Force Microscope, SPI3800N, manufactured by Seiko Instruments Inc.) and found to be 1.147 nm.

<< Formation of optically anisotropic layer >>
A coating solution containing a discotic liquid crystal having the following composition is rotated on the alignment film by rotating a # 2.8 wire bar at 391 rotations in the same direction as the film conveyance direction. It applied continuously to the alignment film surface.

[Coating liquid composition of discotic liquid crystal layer]
-Discotic liquid crystalline compound represented by the following structural formula (G) ... 32.6 parts by mass-Compound represented by the structural formula (D) (additive for orienting the disk surface within 5 degrees) ) ... 0.1 parts by mass / ethylene oxide modified trimethylolpropane triacrylate (V #) 360, manufactured by Osaka Organic Chemical Co., Ltd.) ........................... 3.2 parts by mass / sensitizer (Kayacure DETX, Nippon Kayaku) Yakugyo Co., Ltd.) ······· 0.4 parts by mass · Photopolymerization initiator (Irgacure 907, Ciba Geigy Corp.) ··· 3.0 parts
・ Methyl ethyl ketone ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 62.0 parts by mass

In the step of continuously heating from room temperature to 100 ° C., the solvent is dried, and thereafter, the film surface wind speed of the discotic liquid crystal compound layer is about 90 m so as to be 2.5 m / sec in the 120 ° C. drying zone. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, with the surface temperature of the film being about 80 ° C., an ultraviolet ray irradiation device (ultraviolet lamp: output 120 W / cm) is irradiated with ultraviolet rays for 1 minute to advance the crosslinking reaction, thereby aligning the discotic liquid crystal compound. Fixed to. Then, it was allowed to cool to room temperature and wound into a cylindrical shape to form a roll. In this way, a roll-shaped optical compensation film was produced.
The angle between the disc surface of the discotic liquid crystal compound and the film surface of the support was 0 degree.
When the retardation value at a wavelength of 550nm after allowed to cool (Re ₂₎ was measured and found to be 0nm. In addition, when the retardation value at a wavelength of 550nm the (Rth ₂₎ was measured and found to be 95nm. The results are shown in Table 2.

  When the polarizing plate was arranged in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, the unevenness was not detected even when viewed from the front and the direction inclined to 60 ° from the normal line.

(Comparative Example 3)
<Production of optical compensation film>
<< Preparation of support >>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose triacetate (triacetyl cellulose: TAC) solution.

[Material / solvent composition]
・ Cellulose acetate (Substitution degree: 2.81 Acetylation degree: 60.2%) ・ ・ ・ 100 parts by mass ・ Triphenyl phosphate (plasticizer) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 6 .5 parts by mass-biphenyl diphenyl phosphate (plasticizer) ... 5.2 parts by mass-methylene chloride (first solvent) ... ... 630 parts by mass, methanol (second solvent) ... 95 parts by mass
-Retardation increasing agent shown in the following structural formula (A) ... 18 parts by mass

  Since the produced cellulose acylate film was whitened, the optical properties could not be evaluated.

<Coating of another optically anisotropic layer (hybrid alignment discotic layer)>
In 400.0 parts by mass of methyl ethyl ketone, 100 parts by mass of the discotic liquid crystal compound represented by the above structural formula (G), 0.4 parts by mass of an air interface alignment controller represented by the following structural formula (H), a photopolymerization initiator ( A coating solution was prepared by dissolving 3 parts by mass of Irgacure 907 (manufactured by Ciba Geigy) and 1 part by mass of a sensitizer (Kaya Cure DETX, manufactured by Nippon Kayaku Co., Ltd.).
This coating solution was coated on a support with a # 2.0 wire bar. This was attached to a metal frame and heated in a constant temperature bath at 120 ° C. for 90 seconds to align the discotic liquid crystal compound.
Next, using a 120 W / cm high-pressure mercury lamp at 80 ° C., ultraviolet rays were irradiated for 1 minute to polymerize the discotic liquid crystal compound. Then, it stood to cool to room temperature. Thus, another optically anisotropic layer was formed on the optically anisotropic layer in the optical compensation films prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

<< Measurement of optical properties >>
An alignment film is produced on glass in the same manner as in Example 1, the other optically anisotropic layer is formed on the alignment film, and Re ₍₅₅₀₎ is measured with light having a wavelength of 550 nm using KOBRA21 ADH. As a result, it was 30 nm.

The discotic liquid crystal compound represented by the structural formula (G) was poured into a 2 μm glass cell in which a director of the discotic liquid crystal compound was aligned in parallel in the plane while being heated, and left for 2 minutes. When the retardation value Re_m ₍₅₅₀₎ of this cell was measured with light having a wavelength of 550 nm using KOBRA21 ADH, it was 235 nm. Since the cell gap was 2 μm, the value of Re_m ₍₅₅₀₎ / d was 0.118.

<Preparation of polarizing plate>
First, iodine was adsorbed on a stretched polyvinyl alcohol film to prepare a polarizing film. Then, each optical compensation film of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 coated with another optically anisotropic layer, and Example without coating another optically anisotropic layer 3 is attached to one surface of the polarizing film using a polyvinyl alcohol adhesive, and the other surface of the polarizing film is saponified using a polyvinyl alcohol adhesive. A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was attached. In addition, when the optical compensation film was attached to one surface of the polarizing film, the transmission axis of the polarizing film and the slow axis of the optical compensation film were arranged in parallel. Thus, 5 types of polarizing plates based on Examples 1 to 3 and Comparative Examples 1 to 2 were produced.

<Mounting evaluation with liquid crystal display devices>
<< Preparation of bend alignment liquid crystal cell >>
A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and the alignment film was rubbed. The obtained two glass substrates were faced to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 4.7 μm. A bend-aligned liquid crystal cell was prepared by injecting a liquid crystal compound (ZLI1132, manufactured by Merck & Co., Inc.) having a Δn of 0.1396 into the cell gap.
A polarizing plate produced by using the optical compensation films produced in Examples 1 and 2 and Comparative Example 1 on the upper and lower polarizing plates of a liquid crystal display device using the above-described bend alignment type liquid crystal cell. Are attached to the viewer side and the backlight side one by one through an adhesive so that the liquid crystal cell side becomes the liquid crystal cell side. The optically anisotropic layer of the polarizing plate faced the cell substrate, and the rubbing direction of the liquid crystal cell and the rubbing direction of the “another” optically anisotropic layer facing the liquid crystal cell were arranged to be antiparallel.
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode of 2V white display and 5V black display was set. A voltage at which the transmittance at the front is minimized, that is, a black voltage, is applied, and the black display transmittance (%) at an azimuth angle of 0 ° and a polar angle of 60 ° direction viewing angle and an azimuth angle of 0 ° and a polar angle of 60 ° A color shift Δx with an azimuth angle of 180 degrees and a polar angle of 60 degrees was determined. The results are shown in Table 1. Further, using the measuring device (EZ-Contrast 160D, manufactured by ELDIM) as the contrast ratio, the transmittance ratio (white display / black display), the visual field is displayed in eight stages from black display (L1) to white display (L8). The corner was measured. The results are shown in Table 3.

<Mounting evaluation with liquid crystal display devices>
<< Production of VA Oriented Liquid Crystal Cell >>
The liquid crystal cell has a cell gap between substrates of 3.6 μm, and a liquid crystal material having negative dielectric anisotropy (“MLC6608”, manufactured by Merck & Co., Inc.) is dropped between the substrates and sealed. Prepared by forming a layer. The retardation of the liquid crystal layer (that is, the product Δn · d of the thickness d (μm) of the liquid crystal layer and the refractive index anisotropy Δn) was set to 300 nm. The liquid crystal material was aligned so as to be vertically aligned.

A polarizing plate using the optical compensation film prepared in Example 3 is used as the upper and lower polarizing plates of the liquid crystal display device using the vertical alignment type liquid crystal cell, and the optical compensation film prepared in Example 3 is the liquid crystal cell. One sheet was attached to the observer side and the backlight side through an adhesive so as to be on the side. The crossed Nicols were arranged so that the transmission axis of the polarizing plate on the viewer side was in the vertical direction and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction.
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally black mode with 5 V white display and 0 V black display was set. The black display transmittance (%) at the azimuth angle of 0 ° and the polar angle of 60 ° and the color shift Δx between the azimuth angle of 0 ° polar angle of 60 ° and the azimuth angle of 180 ° and polar angle of 60 ° were obtained. . The results are shown in Table 2.
In Table 2 below, “color shift” means ΔCu′v ′: u′v ′ (polar angle 60 °) −u′v ′ (polar angle 0 °) and azimuth angle 180 at an azimuth angle of 0 °. ΔCu′v ′ at °: sum of u′v ′ (polar angle 60 °) −u′v ′ (polar angle 0 °). (U'v ': color coordinates in CIELAB space)

Further, using the measuring device (EZ-Contrast 160D, manufactured by ELDIM) as the contrast ratio, the transmittance ratio (white display / black display), the visual field is displayed in eight stages from black display (L1) to white display (L8). The corner was measured. The results are shown in Table 3.
In Table 3 below, “viewing angle” refers to a range where the contrast ratio is 10 or more and there is no “black-scale gradation inversion (inversion between L1 and L2)”.

From the results shown in Tables 1 to 3, 0.4 ≦ {Re ₍₄₅₀₎ / Rth ₍₄₅₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 0.95, 1.02 ≦ {Re ₍₆₃₀₎ / Rth ₍₆₃₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 1.9 The liquid crystal display device according to the embodiment of the present invention is capable of transmitting black at a polar angle of 60 °. It can be seen that the rate is low and the color shift from the front is small.

The optical compensation film and polarizing plate of the present invention can improve high contrast and color shift depending on the viewing angle direction during black display, particularly in the VA method and OCB method, and the viewing angle contrast is remarkably improved. It can be suitably used for a liquid crystal display device.
The liquid crystal display device of the present invention optically compensates the liquid crystal cell, can improve the contrast, and reduce the color shift depending on the viewing angle direction, and is preferably used for mobile phones, monitors for personal computers, televisions, liquid crystal projectors, and the like. be able to.

FIG. 1 is a schematic diagram illustrating a configuration example of a liquid crystal display device of the present invention. FIG. 2 is a graph showing optical characteristics of an example of the optical compensation film used in the present invention. FIG. 3 is a schematic view of a Poincare sphere used for explaining a change in the polarization state of incident light in the liquid crystal display device of the present invention. FIG. 4 is a schematic diagram illustrating a configuration example of a conventional OCB mode liquid crystal display device. FIG. 5 is a schematic view of a Poincare sphere used for explaining a change in the polarization state of incident light in an example of a conventional liquid crystal display device. FIG. 6 is a schematic view of a Poincare sphere used for explaining a change in the polarization state of incident light in the liquid crystal display device of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing film 2 Transmission axis 3a Transparent support 13A Optical compensation film 13a Transparent support 13b Optical anisotropic layer 14a In-plane slow axis 5 Another optical anisotropic layer 5a Polarizing film side of molecular symmetry axis of liquid crystalline compound Orientation average direction 6 on the interface side of the support 6 Substrate 7 Liquid crystalline molecule 8 Substrate 9 Another optical anisotropic layer 9a Orientation average direction on the polarizing film side (interface side of the support) of the molecular symmetry axis of the liquid crystalline compound 103a Transparent support 113A Optical compensation film 113a Transparent support 113b Optical anisotropic layer 114a In-plane slow axis 101 Polarizing film 102 Transmission axis

Claims (9)

It has at least a transparent support and an optically anisotropic layer, and the transparent support contains a retardation increasing agent,
The optical compensation film, wherein the transparent support satisfies the following formulas (1) to (4), and the optically anisotropic layer satisfies the following formulas (5) to (8).
However, in the following formulas (1) to (4), Re _(λ) is the retardation value of the transparent support for light with a wavelength of λnm, and Rth _(λ) is the transparent support for light with a wavelength of λnm. In the following formulas (5) to (8), Re _{2 (λ)} is a retardation value of the optically anisotropic layer with respect to light having a wavelength of _λ nm, and Rth _{2 (λ )} Is a retardation value in the thickness direction of the optically anisotropic layer with respect to light having a wavelength of λ nm.
(Equation 1)
10 nm ≦ Re ₍₅₅₀₎ ≦ 100 nm (1)
(Equation 2)
20 nm ≦ Rth ₍₅₅₀₎ ≦ 150 nm (2)
(Equation 3)
0.4 ≦ {Re ₍₄₅₀₎ / Rth ₍₄₅₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 0.95 (3)
(Equation 4)
1.02 ≦ {Re ₍₆₃₀₎ / Rth ₍₆₃₀₎ } / {Re ₍₅₅₀₎ / Rth ₍₅₅₀₎ } ≦ 1.9 Equation (4)
(Equation 5)
0 nm ≦ Re _{2 (550)} ≦ 10 nm (5)
(Equation 6)
20 nm ≦ Rth _{2 (550)} ≦ 100 nm (6)
(Equation 7)
1.10 <Rth _{2 (450)} / Rth _{2 (550)} <1.35 (7)
(Equation 8)
0.90 <Rth _{2 (630)} / Rth _{2 (550)} <1.00 Equation (8) It has at least a transparent support and an optically anisotropic layer, and the transparent support contains a retardation increasing agent,
The transparent support satisfies the relationships of the following formulas (1) to (2) and (9) to (12), and the optically anisotropic layer satisfies the relationships of the following formulas (5) to (8). An optical compensation film characterized by the above.
However, in the following formulas (1) to (2) and (9) to (12), Re _(λ) is a retardation value of the transparent support for light having a wavelength of _λ nm, and Rth _(λ) is Retardation value in the thickness direction of the transparent support with respect to light having a wavelength of λ nm. In the following formulas (5) to (8), Re _{2 (λ)} is a letter of the optically anisotropic layer with respect to light with a wavelength of _λ nm. Rth _{2 (λ)} is a retardation value in the thickness direction of the optically anisotropic layer with respect to light having a wavelength of _λ nm.
(Equation 9)
10 nm ≦ Re ₍₅₅₀₎ ≦ 100 nm (1)
(Equation 10)
20 nm ≦ Rth ₍₅₅₀₎ ≦ 150 nm (2)
(Equation 11)
0.5 <Re ₍₄₅₀₎ / Re ₍₅₅₀₎ <1.0 (9)
(Equation 12)
1.0 <Re ₍₆₃₀₎ / Re ₍₅₅₀₎ <1.5 (10)
(Equation 13)
1.0 <Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ <1.5 ... Formula (11)
(Equation 14)
0.5 <Rth ₍₆₃₀₎ / Rth ₍₅₅₀₎ <1.0 (12)
(Equation 15)
0 nm ≦ Re _{2 (550)} ≦ 10 nm (5)
(Equation 16)
20 nm ≦ Rth _{2 (550)} ≦ 100 nm (6)
(Equation 17)
1.10 <Rth _{2 (450)} / Rth _{2 (550)} <1.35 (7)
(Equation 18)
0.90 <Rth _{2 (630)} / Rth _{2 (550)} <1.00 Equation (8) It has at least a transparent support and an optically anisotropic layer, and the transparent support contains a retardation increasing agent,
The transparent support satisfies the relationships of the following formulas (1) to (2), (9) to (10) and (13) to (14), and the optically anisotropic layer has the following formula (5) to An optical compensation film characterized by satisfying the relationship of (8).
However, in the following formulas (1) to (2), (9) to (10) and (13) to (14), Re _(λ) is the retardation value of the transparent support with respect to light having a wavelength of _λ nm. , Rth _(λ) is a retardation value in the thickness direction of the transparent support with respect to light having a wavelength of λnm. In the following formulas (5) to (8), Re _{2 (λ)} represents light with a wavelength of λnm. It is the retardation value of the optically anisotropic layer, and Rth _{2 (λ)} is the retardation value in the thickness direction of the optically anisotropic layer with respect to light having a wavelength of λnm.
(Equation 19)
10 nm ≦ Re ₍₅₅₀₎ ≦ 100 nm (1)
(Equation 20)
20 nm ≦ Rth ₍₅₅₀₎ ≦ 150 nm (2)
(Equation 21)
0.5 <Re ₍₄₅₀₎ / Re ₍₅₅₀₎ <1.0 (9)
(Equation 22)
1.0 <Re ₍₆₃₀₎ / Re ₍₅₅₀₎ <1.5 (10)
(Equation 23)
0.5 <Rth ₍₄₅₀₎ / Rth ₍₅₅₀₎ <1.0 Expression (13)
(Equation 24)
1.0 <Rth ₍₆₃₀₎ / Rth ₍₅₅₀₎ <1.5 (Equation 14)
(Equation 25)
0 nm ≦ Re _{2 (550)} ≦ 10 nm (5)
(Equation 26)
20 nm ≦ Rth _{2 (550)} ≦ 100 nm (6)
(Equation 27)
1.10 <Rth _{2 (450)} / Rth _{2 (550)} <1.35 (7)
(Equation 28)
0.90 <Rth _{2 (630)} / Rth _{2 (550)} <1.00 Equation (8)   The optical compensation film according to any one of claims 1 to 3, comprising 0.5 to 15% by mass of a retardation increasing agent.   The optical compensation film according to claim 1, wherein the optically anisotropic layer comprises a discotic compound and a cholesteric compound.   6. The optical compensation film according to claim 1, wherein the transparent support is at least one stretched cellulose acylate film.   A polarizing plate having a polarizing film and a pair of protective films sandwiching the polarizing film, wherein at least one of the protective films is the optical compensation film according to any one of claims 1 to 6. A polarizing plate.   A liquid crystal display device comprising a liquid crystal cell and the polarizing plate according to claim 7. The liquid crystal display device according to claim 8, wherein the liquid crystal cell is VA mode or OCB.