JP4731143B2 - Cellulose acylate film, optical compensation film, polarizing plate and liquid crystal display device - Google Patents

Description

The present invention is cellulose chromatography scan acylate film, and optical compensation film, further a polarizing plate using the same, 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 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, a reflector, a 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. Furthermore, the response speed is limited in the TN mode, and development of an LCD using a liquid crystal mode capable of responding at a higher speed is desired.

  Conventionally, an optical compensation film has been developed for a TN liquid crystal display device. However, as demand for liquid crystal televisions increases in recent years, there is a problem in response speed, such as tailing and afterimage phenomenon. It is being pointed out. Therefore, attention has been focused on the OCB mode (or bend mode), which is characterized by a high response speed. However, it is difficult to obtain a wide viewing angle characteristic in the OCB mode, and it is necessary to use an optical compensation film. For example, in the inventions described in Patent Documents 1 and 2, an optical compensation film having a layer made of a liquid crystal compound is applied to an OCB type liquid crystal display device. However, it is difficult to obtain good viewing angle characteristics only by controlling conventionally known optical parameters as described in these documents.

JP-A-9-212444 JP 11-316378 A

  An object of the present invention is to provide a liquid crystal display device, particularly an OCB mode liquid crystal display device, in which the liquid crystal cell is accurately optically compensated, has high contrast, and has reduced coloring depending on the viewing angle direction during black display. Is to provide. Another object of the present invention is to provide an optical compensation film that optically compensates for a liquid crystal cell, particularly an OCB mode liquid crystal cell, and contributes to improvement of contrast and reduction of coloring depending on the viewing angle direction during black display. And

Means for solving the problems of the present invention are as follows.
(1) A transparent cellulose acylate film stretched in at least one direction, and the substitution degree of cellulose acylate varies by 0.05 or more in the range of 2.00 to 3.00 in the thickness direction of the film. A cellulose acylate film having optical anisotropy satisfying the following formulas (I), (II) and (III) :
(I) 0.40 <{Re / Rth (450)} / {Re / Rth (550)} <0.95
(II) 1.05 <{Re / Rth (650)} / {Re / Rth (550)} <1.93
(III) 70 nm <Rth (550) <400 nm
[In the formula, Re / Rth (450) is a ratio of in-plane retardation value measured at a wavelength of 450 nm / thickness direction retardation value measured at a wavelength of 450 nm; Re / Rth (550) is a wavelength of 550 nm. Is the ratio of the in-plane retardation value measured in step / thickness direction retardation value measured at a wavelength of 550 nm; Re / Rth (650) is measured in the in-plane retardation value measured at a wavelength of 650 nm / wavelength of 650 nm. The ratio of retardation values in the thickness direction; and Rth (550) is the retardation value in the thickness direction measured at a wavelength of 550 nm .
(2) The cellulose acylate film according to (1), further comprising a retardation increasing agent.

(3) The cellulose acylate according to (1), wherein the substitution degree of the cellulose acylate film on the higher substitution degree side is 2.75 to 2.92, and the substitution degree on the lower side is 2.64 to 2.83. Rate film.
(4) The cellulose acylate film according to (1), wherein the cellulose acylate film is stretched in a state where a residual solvent is present on the side where the substitution degree of the cellulose acylate film is low.
(5) The difference between the substitution degree of cellulose acylate contained in one layer and the substitution degree of cellulose acylate contained in another layer formed by co-casting of two or more layers is 0.05 or more. (2) The cellulose acylate film as described in (1) above.

(6) An optical compensation film comprising a transparent cellulose acylate film stretched in at least one direction and a liquid crystalline compound and an optically anisotropic layer having in-plane optical anisotropy, the cellulose acylate In the thickness direction of the film, the substitution degree of cellulose acylate varies by 0.05 or more within the range of 2.00 to 3.00, and the cellulose acylate film satisfies the following formulas (I), (II) and (III) In the optically anisotropic layer, the molecules of the liquid crystalline compound are fixed in the aligned state, and the orientation average direction at the cellulose acylate film-side interface of the molecular symmetry axis of the liquid crystalline compound is The crossing angle between the direction orthogonally projected in the plane of the rate film and the slow axis in the plane of the cellulose acylate film is approximately 45 degrees. Optical compensation film:
(I) 0.40 <{Re / Rth (450)} / {Re / Rth (550)} <0.95
(II) 1.05 <{Re / Rth (650)} / {Re / Rth (550)} <1.93
(III) 70 nm <Rth (550) <400 nm
[In the formula, Re / Rth (450) is a ratio of in-plane retardation value measured at a wavelength of 450 nm / thickness direction retardation value measured at a wavelength of 450 nm; Re / Rth (550) is a wavelength of 550 nm. Is the ratio of the in-plane retardation value measured in step / thickness direction retardation value measured at a wavelength of 550 nm; Re / Rth (650) is measured in the in-plane retardation value measured at a wavelength of 650 nm / wavelength of 650 nm. The ratio of retardation values in the thickness direction; and Rth (550) is the retardation value in the thickness direction measured at a wavelength of 550 nm .
(7) The optical compensation film according to (6) , wherein the liquid crystalline compound is a discotic liquid crystalline compound.

(8) A polarizing plate comprising the cellulose acylate film according to any one of (1) to (5) or the optical compensation film according to (6) or (7) and a polarizer.
(9) A liquid crystal display device having a liquid crystal cell and the polarizing plate according to (8) .
(10) The liquid crystal display device according to (9) , wherein the liquid crystal cell is a VA mode or an OCB mode.

  In the present specification, “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 nm to 780 nm. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.

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

  In the present specification, the “molecular symmetry axis” means a symmetry axis when the molecule has a rotational symmetry axis, but does not require that the molecule is rotationally symmetric in a strict sense. In general, the molecular symmetry axis of the discotic liquid crystalline compound coincides with the axis perpendicular to the disc surface passing through the center of the disc surface, and the rod-like liquid crystalline compound coincides with the long axis of the molecule. In the present specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). Rth (λ) is incident with light of wavelength λnm from the direction inclined by + 40 ° with respect to the film normal direction with Re (λ) and in-plane slow axis (determined by KOBRA · 21ADH) as the tilt axis. The retardation value measured in this way, and the retardation value measured by making light of wavelength λ nm incident from a direction tilted by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis. KOBRA · 21ADH is calculated based on the retardation value measured in (1). Furthermore, KOBRA · 21ADH calculates nx, ny, and nz by inputting an assumed value of average refractive index of 1.48 and a film thickness.

  The present invention has been completed based on the knowledge obtained as a result of intensive studies by the present inventors. By using the above-described cellulose acylate film and optical compensation film, the VA system and the OCB system are particularly used. This makes it possible to compensate for the viewing angle in the black state at almost all wavelengths. As a result, in the liquid crystal display device of the present invention, light leakage in an oblique direction during black display is reduced, and the viewing angle contrast is remarkably improved. In addition, the liquid crystal display device of the present invention can suppress light leakage in an oblique direction during black display in almost all visible light wavelength regions. Has been greatly improved.

[Optically anisotropic layer]
First, the operation of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of a liquid crystal display device of the present invention. The OCB mode liquid crystal display device shown in FIG. 1 has a liquid crystal cell composed of a liquid crystal layer 7 in which the liquid crystal bends with respect to the substrate surface when a voltage is applied, that is, black display, and substrates 6 and 8 sandwiching the liquid crystal layer. The substrates 6 and 8 are subjected to alignment treatment on the liquid crystal surface, and the rubbing direction is indicated by an arrow RD. In the case of the back surface, it is indicated by a broken line arrow. Polarizing films 1 and 101 are disposed so as to sandwich the liquid crystal cell. The transmission axes 2 and 102 of the polarizing films 1 and 101 are arranged orthogonal to each other and at an angle of 45 degrees with the RD direction of the liquid crystal layer 7 of the liquid crystal cell. Cellulose acylate films 13a and 113a and optical anisotropic layers 5 and 9 are disposed between the polarizing films 1 and 101 and the liquid crystal cell, respectively. In the cellulose acylate films 13a and 113a, the slow axes 14a and 114a are arranged in parallel with the directions of the transmission axes 2 and 102 of the polarizing films 1 and 101 adjacent thereto, respectively. The optically anisotropic layers 5 and 9 have optical anisotropy expressed by the orientation of the liquid crystalline compound.

  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 therebetween. An alignment film (not shown) is formed on the surface of the substrates 6 and 8 in contact with the liquid crystal molecules 7 (hereinafter sometimes referred to as “inner surface”), and the liquid crystal molecules 7 in a state in which no voltage is applied or in a low application state. Is controlled in a parallel direction with a pretilt angle. Further, on the inner surfaces of the substrates 6 and 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 (micron) of the liquid crystal layer and the refractive index anisotropy Δn is preferably 0.1 to 1.5 microns, and further 0.2 to 1. It is more preferably 5 microns, more preferably 0.2 to 1.2 microns, and even more preferably 0.6 to 0.9 microns. 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 an aspect in which an electric field is applied between the upper and lower substrates 6 and 8, a 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. use.

  For example, when the liquid crystal cell is an OCB mode liquid crystal cell, a nematic liquid crystal material having a positive dielectric anisotropy between Δn = 0.08 and Δε = 5 is used between the upper and lower substrates 6 and 8. it can. The thickness d of the liquid crystal layer is not particularly limited, but can be set to about 6 microns when a liquid crystal having the above characteristics is used. In order to obtain sufficient brightness when white voltage is applied, the brightness during white display changes depending on the thickness Δ and the product Δn · d of refractive index anisotropy Δn 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 0.6 to 1.5 microns.

  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. A 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 averaging is performed. Can be reduced. Further, the same effect can be obtained even if each pixel is constituted by two or more different regions where the alignment direction of liquid crystal molecules continuously changes in a voltage application state.

  Cellulose acylate films 13a and 113a have a Re / Rth ratio Re / Rth (450 nm) at a wavelength of 450 nm of 0.4 to 0.95 times Re / Rth (550 nm) at a wavelength of 550 nm, and Re at a wavelength of 650 nm. / Rth (650 nm) satisfies the relationship of 1.05 to 1.9 times Re / Rth (550 nm), and Rth is 70 to 400 nm. The cellulose acylate films 13a and 113a may function as a support for the optically anisotropic layers 5 and 9, or may function as a protective film for the polarizing film 1 and the polarizing film 101. It may have both functions. That is, the polarizing film 1, the cellulose acylate film 13a and the optically anisotropic layer 5, or the polarizing film 101, the cellulose acylate film 113a and the optically anisotropic layer 9 are integrated into the liquid crystal display device as an integrated laminate. They may be incorporated, or may be incorporated as individual members. Further, a protective film for the polarizing film may be separately disposed between the cellulose acylate film 13a and the polarizing film 1 or between the cellulose acylate film 113a and the polarizing film 101. The protective film is preferably not disposed. The slow axis 14a of the cellulose acylate film 13a and the slow axis 114a of the cellulose acylate film 113a are preferably substantially parallel or orthogonal to each other. If the slow axes 14a and 114a of the cellulose acylate films 13a and 113a are orthogonal to each other, the optical characteristics of light perpendicularly incident on the liquid crystal display device are deteriorated by canceling the birefringence of the respective cellulose acylate films. Can be reduced. Further, in the aspect 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, the phase difference can be compensated by birefringence of the protective film.

  Regarding the transmission axes 2 and 102 of the polarizing films 1 and 101, the slow axis directions 14a and 114a of the cellulose acylate films 13a and 113a, and the alignment direction of the liquid crystal molecules 7, the materials used for each member, the display mode, and the member Adjust to the optimum range according to the laminated structure. 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.

  The optically anisotropic layers 5 and 9 are disposed between the cellulose acylate films 13a and 113a and the liquid crystal cell. The optically anisotropic layers 5 and 9 are layers formed from a composition containing a liquid crystal compound, for example, a rod-like compound or a discotic compound. In the optically anisotropic layer, the molecules of the liquid crystalline compound are fixed in a predetermined alignment state. In the plane of the cellulose acylate films 13a and 113a, the orientation average directions 5a and 9a of the molecular symmetry axis of the liquid crystalline compound in the optically anisotropic layers 5 and 9 at least at the interface on the cellulose acylate film 13a and 113a side, and The slow axes 14a and 114a intersect at approximately 45 degrees. When arranged in such a relationship, the optically anisotropic layer 5 or 9 causes retardation with respect to the incident light from the normal direction, does not cause light leakage, and is incident on the incident light from the oblique direction. In contrast, the effects of the present invention can be sufficiently achieved. Even at the interface on the liquid crystal cell side, the orientation average direction of the molecular symmetry axes of the optically anisotropic layers 5 and 9 is that the slow axes 14a and 114a in the planes of the cellulose acylate films 13a and 113a are approximately 45 degrees. Is preferred.

  Further, the orientation average direction 5a on the polarizing film side (cellulose acylate interface side) of the molecular symmetry axis of the liquid crystalline compound of the optically anisotropic layer 5 is approximately 45 with the transmission axis 2 of the polarizing film 1 located closer. It is preferable to arrange at a time. Similarly, the orientation average direction 9a on the polarizing film side (cellulose acylate film interface side) of the molecular symmetry axis of the liquid crystalline compound of the optically anisotropic layer 9 is substantially the same as the transmission axis 102 of the polarizing film 101 located closer. It is preferable to arrange at 45 degrees. If it arrange | positions in this relationship, optical switching can be carried out according to the sum of the retardation which optical anisotropic layer 5 or 9 generate | occur | produces, and the retardation which generate | occur | produces in a liquid-crystal layer, and it is with respect to the incident light from an oblique direction. Thus, the effects of the present invention can be sufficiently achieved.

Next, the principle of image display of the liquid crystal display device of FIG. 1 will be described.
In a driving state in which a driving voltage corresponding to black is applied to the transparent electrodes (not shown) of the liquid crystal cell substrates 6 and 8, the liquid crystal molecules 7 in the liquid crystal layer are bend-aligned, and the in-plane retardation at that time is obtained. Is canceled by the in-plane retardation of the optically anisotropic layers 5 and 9, and as a result, the polarization state of the incident light hardly changes. Since the transmission axes 2 and 102 of the polarizing films 1 and 101 are orthogonal to each other, the light incident from the lower side (for example, the back electrode) is polarized by the polarizing film 101 and passes through the liquid crystal cells 5 to 8 while maintaining the polarization state. Passes 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 the optically anisotropic layers 5 and 9 does not cancel, and the polarization state changes by passing through the liquid crystal cells 5 to 8, 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. Furthermore, the crossing angle of the transmission axes 2 and 102 of the upper and lower polarizing films 1 and 101 is 90 ° perpendicular to the front, but deviates 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, the cellulose acylate film 13a (or 113a) having optical characteristics satisfying specific conditions, in which Re / Rth in R, G, and B do not match each other, is used. As a result, light leakage in an oblique direction during black display is reduced and the contrast is improved.

More specifically, the present invention uses a cellulose acylate film having the optical characteristics described above, so that light of each wavelength R, G, and B incident in an oblique direction has different slow axes and retardations depending on the wavelength. It is possible to compensate optically. Furthermore, the optically anisotropic layer (5 and 9 in FIG. 1) in which the orientation of the liquid crystalline compound is fixed is obtained by aligning the orientation average direction at the cellulose acylate film side interface of the symmetry axis of the molecule of the liquid crystalline compound with the cellulose acylate. By arranging the film so that the slow axis of the film intersects at 45 °, a unique compensation method of OCB orientation can be performed 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 swung in the left-right direction, for example, there is a difference in coloring and a left-right asymmetry occurs at a polar angle of 60 degrees in the azimuth angle direction of 0 degrees and in the 180-degree direction. The
Here, in this specification, as wavelengths of R, G, and B, R has a wavelength of 650 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 the 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 a cellulose acylate film. 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 cellulose acylate film 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 cellulose acylate film is mainly determined by the slow axis orientation of the cellulose acylate film and the retardation of the cellulose acylate film. In the prior art, 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 specifying 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 light in an oblique direction passing through the cellulose acylate film passes through the optically anisotropic layer in which the alignment of the liquid crystal compound is fixed, and further passes through the bend alignment liquid crystal layer, retardation and vertical polarization at any wavelength. The value of Re / Rth of the cellulose acylate film is adjusted according to the wavelength so that the two factors that the apparent transmission axis of the film deviates from the front can be compensated simultaneously. Specifically, by increasing the Re / Rth of the cellulose acylate film as the wavelength increases, there is no difference in the polarization state in R, G, B caused by wavelength dispersion of the optically anisotropic layer and the liquid crystal cell layer. It became possible to do. As a result, complete compensation is possible and reduction in contrast is reduced. If film parameters are determined by representing the entire visible light region in R, G, and B, it is possible to perform almost complete compensation in the entire visible light region.

  Here, polar angle and azimuth angle are defined. The polar angle is the normal direction of the film surface, that is, the inclination angle from the z-axis in FIG. 1. For example, the normal direction of the film surface is the direction where the polar angle = 0 degrees. The azimuth angle represents an 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 degrees, 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 points before and after the change of the polarization state is indicated by straight arrows in the figure, but in reality, the liquid crystal layer or the cellulose acylate film is used. The change in the polarization state due to passing through is expressed by rotating a specific angle around a specific axis determined according to each optical characteristic on the Poincare sphere. 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. Note that the optical properties of the cellulose acylate films 13a and 113a and the optical properties of the optically anisotropic layers 5 and 9 were calculated under the same conditions as the Poincare sphere in 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 I ₁ of the G light that has passed through the polarizing film 101, I ₂ through the cellulose acylate film _113a, I ₃ through the optically anisotropic layer _9, a black display when the liquid crystal is I ₄ passes through the liquid crystal layer 7 of the _cell, I ₅ through the optically anisotropic layer _5, through the cellulose acylate film 13a becomes the polarization state of the I _6, shielded by the polarizing film 1, the ideal Display black. On the other hand, the G light incident from the right 60 ° also changes its polarization state from I ₁ ′ → I ₂ ′ → I ₃ ′ → I ₄ ′ → I ₅ ′ → I ₆ ′. Examining the change of the polarization state, the change of the polarization state by passing through the optically anisotropic layers 9 and 5 and the liquid crystal layer 7 is a mirror-symmetric change with the incident light from the left 60 ° and the right 60 °. On the other hand, the change in the polarization state by passing through the cellulose acylate films 113a and 13a coincides with the incident light from the left 60 ° and the right 60 °. In order to reduce the left and right black spots 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 region, the positions of I ₆ and I ₆ ′ coincide with each other, and the positions are blocked by the polarizing film 1. It is necessary to be in a position showing the polarization 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 cellulose acylate film 113a in which Re / Rth exhibits the above-described wavelength dependency. And 13a are not disposed, and instead, for example, the transparent supports 103a and 3a of the optically anisotropic layers 5 and 9 are disposed. The transparent supports 103 and 3 are used for the purpose of supporting the optically anisotropic layers 5 and 9, and are made of a general polymer film. Accordingly, there is no wavelength dependency on Re / Rth as shown in the cellulose acylate films 113a and 13a, and the same Re and Rth are shown at any of 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. As a result, a sufficient viewing angle contrast cannot be obtained, and compensation cannot be made at all wavelengths, so that there is a problem of coloring.

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 figure, the polarization state of _R incident light is indicated by I _R , the polarization state of G incident light is indicated by I _G , and the polarization state of _B incident light is indicated by IB. Further, as a configuration of a conventional OCB mode liquid crystal display device, it is assumed that the transparent supports 3 and 103 in FIG. 4 have Re = 45 nm and Rth = 160 nm at any wavelength of R, G, and B. The optical anisotropic layers 5 and 9 were calculated assuming that Re = 30 nm. First, in FIG. 5A, the polarization states I _R1 , I _G1 and I _B1 after passing through the polarizing film 101 are equal. Paying attention to the change in the polarization state of the B light, the B light incident from the left 60 ° has a direction in which the polarization state I _B2 after passing through the transparent support 103 transitions by passing through the optically anisotropic layer 9. The B light incident in the same direction and incident from 60 ° to the right is shifted in the direction opposite to the direction in which the polarization state I _B2 ′ after passing through the transparent support 103 transitions by passing through the optically anisotropic layer 9. I can understand that. That is, the light that is incident from the left and the light that is incident from the right differ in how the transparent support 103 affects the polarization state. As a result, the final transition states I _R6 , I _G6 and I _B6 of the R, G and B incident light from the left 60 °, the final transition states of the R, G and B incident light from the right 60 ° The positions of I _R6 ′, I _G6 ′, and I _B6 ′ do not coincide with each other, and 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 cellulose acylate film exhibiting specific optical characteristics, left and right black light omission and left and right color misregistration of an 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. FIG. 6A 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. 6B 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 figure, the polarization state of _R incident light is indicated by I _R , the polarization state of G incident light is indicated by I _G , and the polarization state of _B incident light is indicated by IB. Cellulose acylate films 113 and 13 have a Re / Rth (450 nm) at a wavelength of 450 nm of 0.17, a Re / Rth (550 nm) at a wavelength of 550 nm of 0.28, and a Re / Rth (650 nm) of 0 at a wavelength of 650 nm. .39, and Rth at a wavelength of 550 nm is assumed to be 160 nm. The Re of the optically anisotropic layers 5 and 9 was assumed to be the same value as the Poincare sphere shown in FIG.

  As shown in FIGS. 6 (a) and 6 (b), the R light, G light and B light incident from the left and right pass through the cellulose acylate films 113a and 13a, and all of them are near S1 = 0. And, it changes to the polarization state of the shifted position reflecting the wavelength dependency of Re / Rth of the cellulose acylate film 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 optically anisotropic layers 9, 5 and the liquid crystal layer 7. 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 uses a cellulose acylate film having optical properties 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, and the cellulose acylate By positively using the optical characteristics of the film for optical compensation, the left and right black lights and the left and right color shift are simultaneously improved. 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, TN mode, and OCB 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.

Next, a cellulose acylate film or an optical compensation film for realizing this optical compensation will be specifically described.
It is known that the cellulose acylate film has different wavelength dependency of Re or Rth depending on the degree of substitution (proportional to the acylate ratio). As the degree of substitution increases, Re (Rth) tends to decrease on the short wavelength side and Re (Rth) increases on the long wavelength side.
In the present invention, the substitution degree of cellulose acylate is varied within the range of 2.00 to 3.00 in the thickness direction of the film by 0.05 or more. The fluctuation range is preferably 0.07 or more, more preferably 0.08 or more, further preferably 0.09 or more, and most preferably 0.10 or more.

  The cellulose acylate film is generally preferably produced by a solution casting method, and the residual solvent is preferably stretched between 2 and 100% by mass. These specific examples will be described in detail later. The inventor analyzed the film after stretching and found that the stretching orientation degree of the cellulose acylate molecule was different in the thickness direction. Specifically, as compared with the inside of the film, the degree of stretching orientation increases toward the outside. This is presumed that the residual solvent stays inside the film, so that even if the inside of the film is stretched, orientation relaxation occurs, and as a result, the outer stretched orientation degree increases.

  That is, when a layer with a high degree of substitution (acylation rate) is provided on the outside of the cellulose acylate film and a layer with a low degree of substitution (acylation rate) is provided on the inside, and stretching is performed with a residual solvent, it is expressed by stretching. The effect of the layer having a high degree of substitution (acylation rate), which is the outer layer of the film, is increased, and the Rth value is determined by the plane orientation due to the decrease in the thickness of the entire film as the drying proceeds. to be influenced. Therefore, films having different wavelength dependences of the Re value and the Rth value can be produced. The outer substitution degree is 2.71 to 3.00 (acetation ratio in the case of cellulose acetate is 59.0 to 62.5%), and the inner substitution degree is 2.56 to 2.87 (in the case of cellulose acetate). Acetate ratio of 57.0 to 61.0%) is preferable. More preferably, the outer side is 2.75 to 2.92 (59.5 to 61.5%), and the inner side is 2.64 to 2.83 (58.0 to 60.5%). The ratio of the outer side to the inner side is preferably 0.01 to 0.5, more preferably 0.05 to 0.4, when the thickness is 1. The absolute values of Re and Rth and the wavelength dependency can be appropriately controlled by the additives described later.

  The ratio Re / Rth (450 nm) of Re and Rth at a wavelength of 450 nm in the visible light region of the cellulose acylate film of the present invention is 0.4 to 0.95 times Re / Rth (550 nm) at a wavelength of 550 nm, It is preferably 0.4 to 0.9 times, more preferably 0.6 to 0.8 times, and Re / Rth (650 nm) at a wavelength of 650 nm is 1.05 to Re / Rth (550 nm). 1.93 times, preferably 1.1 to 1.9 times, more preferably 1.2 to 1.7 times. Note that Re / Rth in each of R, G, and B is preferably in the range of 0.1 to 0.8.

  Further, the retardation (Rth) in the thickness direction of the entire cellulose acylate film has a function for canceling the retardation of the liquid crystal layer in the thickness direction during black display. The preferred range 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 (micron) and refractive index anisotropy Δn of 0.2 to 1.5 microns) When it is used for optical compensation, it is preferably 70 to 400 nm, more preferably 100 nm to 400 nm, and even more preferably 160 to 300 nm. The Re retardation is generally 20 to 110 nm, preferably 20 to 70 nm, and more preferably 35 to 70 nm. Hereinafter, details of the present invention will be described.

(Cellulose acylate)
As the raw material cotton of cellulose acylate, a known raw material can be used (for example, refer to the Japanese Society for Invention and Innovation 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 viscosity average polymerization degree of cellulose acylate is preferably 200 to 700, more preferably 250 to 500, and most 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 most preferably 3.0 to 4.0. preferable.

  The acyl group of the cellulose acylate film is not particularly limited, but is preferably an acetyl group or a propionyl group, and particularly preferably an acetyl group. The degree of substitution of all acyl groups is preferably 2.7 to 3.0, more preferably 2.8 to 2.95. In this specification, the substitution degree of an acyl group is a value calculated according to ASTM 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 61.5. % Is more preferable. When the acetylation degree is within this range, Re does not become larger than the desired value due to the conveying tension during casting, there is little in-plane variation, and there is little change in the retardation value due to temperature and humidity. In addition, the substitution degree of the acyl group at the 6-position is preferably 0.9 or more from the viewpoint of suppressing variations in Re and Rth.

(Co-casting)
The cellulose acylate films having different acylation rates in the thickness direction of the present invention are preferably produced by a co-casting method.
Hereinafter, the co-casting method preferably used in the present invention will be described in detail.
In the co-casting method, it is preferable to cast a plurality of cellulose acylate solutions of two or more layers on the obtained cellulose acylate solution on a smooth band or drum as a metal support.

  When a multilayer casting film or a multilayer film is manufactured by using the liquid casting method, a feed block type casting die is often used, and the feed block type casting die is disposed upstream of the casting die. This is a casting apparatus in which a merging means for merging seeds or more dopes is joined. A typical structure of the feed block type casting die is provided with a channel for passing a dope serving as a core layer in the center, and a dope forming a front surface layer and a back surface layer on both sides thereof, and the latter The two solution streams are joined to both sides of the former solution stream. As an example of a method for producing a multilayer film using the above feed block type casting die, a relatively high viscosity dope is used for the resin layer as the core layer, and a relatively low viscosity dope is used for the front and back surface layers. Japanese Patent Publication No. 62-43846 discloses a method of performing dry peeling after forming a multilayer cast film.

  In addition, when casting a plurality of cellulose acylate solutions, the film is formed while casting and laminating a solution containing cellulose acylate from a plurality of casting openings provided at intervals in the traveling direction of the metal support. For example, methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be applied. Alternatively, a film may be formed by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, This can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933. Further, a cellulose acylate film in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solutions are simultaneously extruded. A casting method may be used. Furthermore, it is also a preferred embodiment that the outer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner solution.

Alternatively, by using two casting ports, the film cast on the metal support is peeled off by the first casting port, and the second casting is performed on the side that is in contact with the metal support surface. For example, it is a method described in Japanese Patent Publication No. 44-20235. The cellulose acylate solutions to be cast may be the same solution or different cellulose acylate solutions, and are not particularly limited. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port.
Furthermore, the cellulose acylate solution of the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer).

  In the conventional single-layer liquid, it is necessary to extrude a cellulose acylate solution having a high concentration and a high viscosity in order to obtain a necessary film thickness. In many cases, this causes a problem such as a fault or flatness. As a solution to this, by casting a plurality of cellulose acylate solutions from a casting port, a highly viscous solution can be extruded onto a metal support at the same time, and the planarity is improved and an excellent planar film is obtained. In addition to being able to be produced, the use of a concentrated cellulose acylate solution could reduce the drying load and increase the film production speed.

  In the case of co-casting, a cellulose acylate film with a laminated structure is produced by co-casting cellulose acylate solutions with different additive concentrations such as the plasticizer, ultraviolet absorber, and matting agent described below in addition to the acylation ratio. You can also For example, a cellulose acylate film having a structure of skin layer / core layer / skin layer can be produced. For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Moreover, it is also a preferable aspect that a release agent is contained only in the skin layer on the metal support side. It is also preferable to add more alcohol, which is a poor solvent, to the skin layer than the core layer in order to cool the metal support by the cooling drum method to gel the solution. The Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. Further, the viscosity of the solution containing cellulose acylate during casting may be different between the skin layer and the core layer, and the viscosity of the skin layer is preferably smaller than the viscosity of the core layer. It may be smaller than the viscosity.

  The casting method according to the present invention will be described in more detail. A method for uniformly extruding the prepared dope from a pressure die onto a metal support, and a film thickness of the dope once cast on the metal support with a blade. There are a method using a doctor blade for adjustment, a method using a reverse roll coater for adjustment using a reverse rotating roll, and the like. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods mentioned here, various known methods for casting a cellulose triacetate solution (for example, JP-A-61-94724, JP-A-61-148013, JP-A-4-85011). No. 4, JP-A-4-286611, JP-A-5-185443, JP-A-5-185445, JP-A-6-278149, JP-A-8-207210, etc.) are preferably used. By setting each condition in consideration of the difference in the boiling point of the solvent to be used, the same effects as described in the respective publications can be obtained.

  In addition, as an invention related to co-casting, in order to increase the casting speed, Japanese Patent Application Laid-Open No. 53-134869 discloses that the cellulose acetate solution is 10-90% of the total film thickness from the first casting port. An invention is described in which the film thickness is cast and the remainder is cast from the second casting port at a distance of 30 to 60% from the first casting port to peeling.

  Japanese Patent Application Laid-Open No. 61-018943 discloses that TAC is a dope (M) made of methichro and methanol and another poor solvent in order to speed up casting stably, and a dope having a poor solvent ratio higher than A (see FIG. In B), there is described an invention in which the dope A is co-cast and formed into a film so as to be 5 μm or more in an undried state. Furthermore, it is also disclosed that it is desirable to join A and B in the middle of the slit with a composite slit die. This invention has the same effect even if the methylochrome is non-chlorine, and can be applied to the present invention.

  Furthermore, for the purpose of obtaining a magnetic recording layer with good flatness, Japanese Patent Application Laid-Open No. 4-124645 discloses a stripe co-casting die in which the sectional name of the slit from one manifold to the joining portion is a comb-like shape. An invention using is described.

  In addition, in order to reduce the solvent contained in the film immediately after production, which is excellent in transparency, dimensional stability, and heat-and-moisture resistance, JP-A-8-207210 discloses a cellulose acetate core having a substitution degree <2.7. An invention is described in which a surface layer having a thickness of 0.5 to 15 μm made of cellulose acetate having a substitution degree> 2.8 is provided on at least one side of the part and the core part.

  Further, in JP-A-10-058514, in order to prevent the film from being peeled off with good smoothness, the surface layer dope is coated on the base layer dope (excluding both ends) and simultaneously extruded from the die. The invention to perform is described.

  JP-A-5-040321 describes an invention relating to a light-sensitive material in which magnetic dope and non-magnetic dope are co-cast.

  In order to obtain a multilayer resin film with higher thickness accuracy, JP 2000-317960 A discloses a low-viscosity liquid and a high-viscosity liquid having a viscosity of 2 to 10 times from each flow path. An invention is described in which a multi-flow casting film is formed by discharging from a casting die lip for 5-25 seconds from the time of merging after joining and forming a liquid parallel flow in contact with the interface.

  Japanese Patent Application Laid-Open No. 2002-221620 discloses that the slope of the stripe-shaped unevenness with a pitch of 3 to 15 mm is less than 0.04 degrees by co-casting the outer layer with a low concentration in the polarizing plate film. It is described to do.

  Furthermore, in Japanese Patent Application Laid-Open No. 2003-080541, in order to suppress the occurrence of burrs, when casting a plurality of dopes from a die, a dope shear viscosity A and an intermediate layer are formed. An invention is described in which the ratio A / B with the shear viscosity B of the dope is A / B <0.9.

  Further, JP-A-2003-014933 discloses an invention of a retardation film having little additive bleed-out, no delamination phenomenon between layers, good slipperiness and excellent transparency.

  Furthermore, in JP-A-2003-014933, it is preferable to add fine particles to the surface layer in order to impart film slipperiness, and it is not necessary to add fine particles to the core layer, but they may be added. Is disclosed. However, since the transparency of the film deteriorates when the amount of fine particles added to the core layer is large, the amount added is preferably 1/10 or less of the amount added to the surface layer, and more preferably substantially the core layer. It is shown that it does not contain fine particles. (Substantially not contained, the amount of fine particles added is 0 to 0.01% by mass per solid content) It is also disclosed that the effect of slipperiness can be obtained if blended on at least one side of both surface layers. In particular, the primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 16 to 5 nm, and particularly preferably 12 to 5 nm from the viewpoint of keeping the haze low. . The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, particularly preferably 100 to 200 g / liter, and the higher the apparent specific gravity, the higher the specific gravity. It is described that a dispersion liquid having a concentration can be produced, and that haze and aggregates are improved, which is preferable. Here, the silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more are, for example, a mixture of vaporized silicon tetrachloride and hydrogen at 1000 to 1200 ° C. It can be obtained by burning in. For example, it is disclosed that it is marketed under the names of Aerosil 200V, Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.).

(Stretching)
The cellulose acylate film of the present invention exhibits a function by stretching.
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. For example, they are described in JP-A-62-115035, JP-A-4-152125, JP-A-4-284221, JP-A-4-298310, JP-A-11-48271, and the like. The film is stretched at room temperature or under heating conditions. The heating temperature is preferably not higher than the glass transition temperature of the film. The film may be stretched uniaxially or biaxially. The film can be stretched by a treatment during drying, and is particularly effective when the solvent remains. For example, by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed, the film is stretched. The film can also be stretched by conveying the film while holding it with a tenter and gradually widening the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine). The stretching ratio of the film (the ratio of the increase due to stretching relative to the original length) is preferably 0.5 to 300%, more preferably 1 to 200%, and particularly 1 to 100%. Is 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 step of stretching the formed film, and the draw ratio is 1.2 times or more. It is preferably 8 times or less. In addition, the stretching may be performed in one stage or in multiple stages. When performing in multiple stages, the product of each draw ratio may be within this range.

  The stretching speed is preferably 5% / min to 1000% / min, and more preferably 10% / min to 500% / min. The stretching temperature is preferably 30 ° C to 160 ° C, more preferably 70 ° C to 150 ° C. 85-150 degreeC is especially preferable. The stretching is preferably performed by a heat roll or / and a radiant heat source (such as an IR heater) or 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 this phase difference plate is 2.0 to 5.0.

  It is preferable to provide a preheating step before stretching. You may heat-process after extending | stretching. The heat treatment temperature is preferably 20 ° C. to 10 ° C. higher than the glass transition temperature of the cellulose acetate film, and the heat treatment time is preferably 1 second to 3 minutes. The heating method may be zone heating or partial heating using an infrared heater. You may slit the both ends of a film in the middle or the end of a process. These slit scraps are preferably recovered and reused as raw materials. Further, regarding the tenter, in JP-A-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 blowing air volume. By appropriately controlling the ratio and the use of a high specific heat drying gas, it is possible to ensure quality prevention such as flatness when the speed by the solution casting method is increased or the web width is widened.

  Japanese Patent Application Laid-Open No. 11-077782 describes an invention 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. .

  Furthermore, in order to prevent the occurrence of unevenness, Japanese Patent Application Laid-Open No. 4-204503 describes an invention in which the film is stretched with a solvent content of 2 to 10% based on the solid content.

  Further, in order to suppress curling due to the regulation of the clip biting width, Japanese Patent Application Laid-Open No. 2002-248680 discloses that tenter clip biting width D ≦ (33 / (log stretch ratio × log volatile content)). An invention that suppresses curling and facilitates film conveyance after the stretching process is described.

  Furthermore, in order to achieve both high-speed soft film conveyance and stretching, Japanese Patent Application Laid-Open No. 2002-337224 describes an invention in which tenter conveyance is switched between a first half pin and a second half clip.

  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, and then casting. The web (film) peeled from the support for the film is stretched 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. An optically biaxial invention obtained by the above is described. As a more preferred embodiment, it is described that the film is stretched 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. . In addition, as another stretching method, a circumferential speed difference is applied to a plurality of rolls, and a longitudinal stretching is performed using the difference between the circumferential speeds of the rolls, and both ends of the web are fixed with clips or pins. Examples include a method of extending the interval in the traveling direction and stretching in the vertical direction, a method of expanding in the horizontal direction and extending in the horizontal direction, a method of expanding the vertical and horizontal directions simultaneously and stretching in both the vertical and horizontal directions, a method using a combination of these, and the like. It has been. Further, in the case of the so-called tenter method, it is 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 or the like can be reduced.

  Further, as described in JP-A-2003-014933, 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 a resin, an additive, and an organic solvent, and a dope B containing no resin, or an additive containing a resin, an additive, and an organic solvent that is less than the dope A, After co-casting on the support so that the dope A becomes the core layer and the dope B as the surface layer, and evaporating the organic solvent until it becomes peelable, the web is peeled from the support, An invention is described in which the residual solvent in the resin film is stretched 1.1 to 1.3 times in at least one axial direction in the range of 3 to 50% by mass. Furthermore, as a preferred embodiment, the web is peeled from the support and further stretched 1.1 to 3.0 times in the uniaxial direction at a stretching temperature in the range of 140 ° C. 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 the solvent is evaporated, the web is peeled from the support, and the residual solvent amount in the resin film at the time of stretching is 1.1 to 3.0 times in at least one axial direction in the range of 3 to 50% by mass. Stretching, further stretching at least uniaxially in the range of 140 ° C to 200 ° C in a uniaxial direction, 1.1 to 3.0 times, dope A containing resin, organic solvent and additives, and additives Resin with less additive content than dope A A dope B containing an additive and an organic solvent, and a dope C containing a resin, fine particles, and an organic solvent are prepared. The dope A is a core layer, the dope B is a surface layer, and the dope C is a surface opposite to the dope B. After co-casting on the support so as to form a layer and evaporating the organic solvent until it can be peeled, the web is peeled off from the support, and the amount of residual solvent in the resin film during stretching is 3 mass Stretching 1.1 to 3.0 times in at least uniaxial direction in the range of 50% by mass to 50% by mass, 1.1 to 3.0 times stretching in at least uniaxial direction in the range of 140 ° C to 200 ° C. The additive amount in the dope A is 1 to 30% by mass with respect to the resin, the additive amount in the dope B is 0 to 5% by mass with respect to the resin, and the additive is a plasticizer or UV absorber. Agent or retardation control agent, in dope A and dope B It is preferred that the organic solvent is utilized in that it contains more than 50 wt% methylene chloride or methyl acetate with respect to the total organic solvents.

  Furthermore, in JP-A-2003-014933, as a stretching method, there is a transverse stretching machine called a tenter that fixes both ends of a web with clips and pins and stretches the intervals between the clips and pins in the lateral direction. It is described that it can be preferably used. It is also disclosed that stretching or shrinking in the longitudinal direction can be performed by widening or shrinking the interval in the transport direction of the clip or pin in the transport direction (longitudinal direction) using a simultaneous biaxial stretching machine. . In addition, driving the clip portion by the linear drive method is preferable because it can be smoothly stretched and the risk of breakage can be reduced, and as a method of stretching in the longitudinal direction, a difference in peripheral speed is applied to a plurality of rolls. In the meantime, it is suggested that a method of stretching in the longitudinal direction by utilizing the difference in the circumferential speed of the roll can be used. These stretching methods may be used in combination, and the stretching process may be performed in two or more stages, such as (longitudinal stretching, lateral stretching, longitudinal stretching) or (longitudinal stretching, longitudinal stretching). It is described that it is good.

  Furthermore, in order to prevent foaming of the tenter-dried web, improve detachability, and prevent dust generation, Japanese Patent Application Laid-Open No. 2003-004374 discloses that when hot air from a dryer hits both edges of the web. There is described an invention in which the width of the dryer is made shorter than the width of the web.

  Further, in order to prevent foaming of the tenter-dried web, improve detachability, and prevent dust generation, Japanese Patent Application Laid-Open No. 2003-019757 discloses that both end portions of the web are protected from being exposed to the tenter holding portion. An invention in which a wind shield is provided on the inside is described.

  Furthermore, in order to stably carry and dry, Japanese Patent Application Laid-Open No. 2003-053749 describes that the thickness after drying of both ends of the film carried by the pin tenter is X μm, and the average thickness after drying of the product portion of the film. When the thickness is T μm, when the relationship between X and T is formula (1) T ≦ 60, 40 ≦ X ≦ 200, and when formula (2) 60 <T ≦ 120, 40+ (T−60) × 0. The invention that satisfies the relationship of 52+ (T−120) × 0.2 ≦ X ≦ 400 when 2 ≦ X ≦ 300 or Formula (3) 120 <T is described.

  In order to prevent wrinkles from occurring in the multistage tenter, Japanese Patent Laid-Open No. 2-182654 discloses a tenter device in which a heating chamber and a cooling chamber are provided in the dryer of the multistage tenter, and the left and right clip chains are separated. Describes an invention for cooling.

  Further, in order to prevent web breakage, wrinkles, and conveyance failure, Japanese Patent Application Laid-Open No. 9-077315 describes an invention in which the pin density of the pin tenter is increased while the pin density on the outer side is decreased. .

  In order to prevent foaming of the web itself and adhesion of the web to the holding means in the tenter, Japanese Patent Application Laid-Open No. 9-085846 discloses a tenter drying device in which both side edge holding pins of the web are blown-out type coolers. In the invention, the pin is cooled to below the foaming temperature of the web, and the pin immediately before the web is entrapped is cooled to a gelling temperature of the dope in the duct type cooler + 15 ° C. or lower.

  Further, in order to prevent pin tenter losing and improve foreign matter, Japanese Patent Application Laid-Open No. 2003-103542 discloses a surface temperature of a web that cools the insertion structure and contacts the insertion structure in the pin tenter. Describes an invention relating to a solution casting method in which the temperature does not exceed the gelling temperature of the web.

  In order to prevent deterioration in quality such as flatness when the speed is increased by the solution casting method or the width of the web is widened by a tenter, JP-A-11-0777718 discloses a web in the tenter. When drying, the wind speed is 0.5 to 20 (40) m / s, the transverse temperature distribution is 10% or less, the web vertical air flow ratio is 0.2-1, and the dry gas ratio is 30 to 250 J / Kmol. The invention 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 at which the air blows out from the air outlet is 30 ° to 150 ° with respect to the film plane until the residual solvent amount in the web reaches 4% by mass. And the difference between the upper limit and the lower limit is within 20% of the upper limit when the wind speed distribution on the surface of the film located in the direction in which the drying gas is blown out is taken as the reference, the drying gas When the amount of residual solvent in the web is 130% by mass or less and 70% by mass or more, the wind speed of the dry gas blown from the blow type dryer on the web surface is 0.5 m / sec. When the residual solvent amount is less than 70% by mass and less than 4% by mass and the residual solvent amount is less than 70% by mass and less than 4% by mass, the dry gas wind blown out at a wind speed of 0.5m / sec to 40m / sec. 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, the residual solvent in the web It is described that when the 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 blow-out port of the blow-type dryer located above and below the conveyed web is 0.2 ≦ q ≦ 1. Has been. 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.

  In order to prevent deterioration of flatness and coating due to the generation of contaminants, Japanese Patent Application Laid-Open No. 11-0777719 describes an invention in which a tenter clip incorporates a heating part in a TAC manufacturing apparatus. ing. As a further preferable aspect, a device for removing foreign matter generated at the contact portion between the clip and the web between the time when the tenter clip releases the web and the time when the web is carried again, a jetting gas or liquid, and Remove foreign matter using a brush, the residual amount when the clip or pin contacts the web is 12% by mass or more and 50% by mass or less, and the surface temperature of the contact part between the clip or pin and the web is 60 ° or more. It is disclosed that it is 200 ° or less (more preferably 80 ° or more and 120 ° or less).

  In order to improve flatness, improve quality deterioration due to tearing in the tenter, and increase productivity, Japanese Patent Application Laid-Open No. 11-090943 describes a tenter clip with an arbitrary transport length Lt (m). The ratio Lr = Ltt / Lt of the total length Ltt (m) in the conveying direction of the portion where the clip of the tenter having the same length as Lt holds the web is 1.0 ≦ Lr ≦ 1.99 The invention to be described is described. Furthermore, as a preferable aspect, it is disclosed that the portion holding the web is arranged without a gap when viewed from the web width direction.

  In addition, in order to improve the flatness deterioration due to sagging of the web and the instability of the introduction when introducing the web into the tenter, Japanese Patent Application Laid-Open No. 11-090944 discloses a plastic film manufacturing apparatus before the tenter entrance. An invention having a sag suppressing device in the web width direction is described. Further, as a more preferable aspect, the sagging suppression 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 can blow air from under the web. Having a blower is also disclosed.

  In order to prevent deterioration of quality and sagging that hinders productivity, Japanese Patent Application Laid-Open No. 11-090945 provides an angle with respect to the horizontal of the web peeled from the support in the TAC manufacturing method. The invention to be introduced into the tenter is described.

  In order to produce a film having stable physical properties, Japanese Patent Application Laid-Open No. 2000-289903 discloses a web transfer apparatus that transports while applying tension in the width direction of the web when the solvent content is 50 to 12 wt%. Width detection means, web holding means, and an invention that has two or more variable bending points, calculates the web width from the detection signal in web width detection, and changes the position of the bending point Yes.

  Further, in order to improve the clipping property, prevent the web from being broken for a long period of time, and obtain a film with excellent quality, Japanese Patent Application Laid-Open No. 2003-033933 describes the left and right sides of the web on the left and right sides of the portion near the entrance of the tenter. A web side edge curl prevention guide plate is arranged at least below the upper and lower edges, and the web facing surface of the guide plate is in contact with the web contact resin portion arranged in the web conveyance direction. It is described that it is constituted by a metal part for use. As a further preferred embodiment, the web contact resin portion of the web facing surface of the guide plate is disposed on the upstream side in the web conveyance direction, the web contact metal portion is disposed on the downstream side, the web contact resin portion of the guide plate, and The level difference (including the inclination) between the web contact metal parts is within 500 μm, and the width of the guide plate web contact resin part and the web contact metal part contacting the web is 2 to 2, respectively. It is 150 mm, the distance of the web contact direction of the web contact resin part of the guide plate and the web contact metal part in the web conveyance direction is 5 to 120 mm, respectively, and the web contact resin part of the guide plate is made of metal. Provided by surface resin processing or resin coating on the guide substrate, the web contact resin part of the guide plate is made of a single resin, the left and right side edges of the web The distance between the web facing surfaces of the guide plates arranged above and below is 3 to 30 mm, and the distance between the web facing surfaces of the upper and lower guide plates at the left and right side edges of the web. In the width direction of the web and inward, it is enlarged at a rate of 2 mm or more per 100 mm width, 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 the upper and lower guide plates are arranged so as to be displaced back and forth along the web conveying direction, and the distance of the deviation between the upper and lower guide plates is −200 to +200 mm, the upper guide The web facing surface of the 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 metal portion is It is disclosed that the surface roughness of the web facing surface of the guide plate or the web contact resin portion and / or the web contact metal portion provided on the guide plate is 3 μm or less. Yes. 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. Has been.

  Further, in order to prevent the cutting and unevenness of the web that occurs during drying in the tenter, Japanese Patent Application Laid-Open No. 11-048271 discloses that after peeling, the web is stretched with a width stretching apparatus when the solvent content is 50 to 12 wt%. The invention describes a method in which a pressure of 0.2 to 10 KPa is applied from both sides of a web by a pressure device when the web is dried and the solvent content of the web is 10 wt% or less. As a more preferred embodiment, when applying pressure using a nip roll as a method of finishing applying tension when the solvent content is 4% by mass or more or applying pressure from both sides of the web (film), the number of nip roll pairs is from 1. It is also disclosed that about 8 sets are preferable, and the temperature when pressurizing is preferably 100 to 200 ° C.

  In addition, JP 2002-036266, which is an invention for obtaining a high-quality thin tack having a thickness of 20 to 85 μm, has, as a preferable aspect, a tension that acts on the web along the conveying direction before and after the tenter. The difference is set to 8 N / mm2 or less, a preheating process for preheating the web after the peeling process, a stretching process for stretching the web using a tenter after the preheating process, and the web after the stretching process. And a relaxation step for relaxing by an amount smaller than the stretching amount in the stretching step, the temperature T1 in the preheating step and the stretching step is set to (glass transition temperature Tg-60 of 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 process is 0 to 30 in a ratio to the web width immediately before entering the stretching process. In the web stretch ratio in the relaxation step, to -10 to 10%, etc. is disclosed.

  Further, JP 2002-225054 A, which aims to have a dry film thickness of 10 to 60 μm and a low durability with light weight and moisture permeability, has a residual solvent amount of 10% by mass after peeling. Until both ends of the web are gripped by clips, drying shrinkage is suppressed by holding the width, and / or stretching is performed in the width direction, and the formula S = {(Nx + Ny) / 2} −Nz Forming a film having a degree of plane orientation (S) of 0.0008 to 0.0020 (where Nx is the refractive index in the direction of highest refractive index in the plane of the film, and Ny is relative to Nx) The refractive index in the direction perpendicular to the plane, Nz is the refractive index in the film thickness direction), the time from casting to peeling is 30 to 90 seconds, and the web after peeling is in the width direction and / or the longitudinal direction. Stretching in the direction, etc. are disclosed.

  Japanese Patent Application Laid-Open No. 2002-341144 describes a solution film-forming method having a stretching step in which the mass concentration of the retardation increasing agent has a higher optical distribution as it approaches the center in the film width direction in order to suppress optical unevenness. Has been.

  Furthermore, in Japanese Patent Application Laid-Open No. 2003-071863, which is an invention for obtaining a film free from fogging, the draw ratio in the width direction is preferably 0 to 100%, and when used as a polarizing plate protective film, 5 It is described that -20% is more preferable, and 8-15% is most preferable. On the other hand, when used as a phase difference film, 10 to 40% is more preferable, and 20 to 30% is most preferable. Ro can be controlled by the draw ratio, and the higher the draw ratio, the more the film is completed. It is disclosed that it is preferable because of its excellent flatness. Further, 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 the content is 5% by mass or less. Further, the drying temperature in the case of performing the tenter is preferably 30 to 150 ° C, more preferably 50 to 120 ° C, most preferably 70 to 100 ° C, and the lower the drying temperature, the less the transpiration such as the ultraviolet absorber and the plasticizer. It is also disclosed that process contamination can be reduced, but on the other hand, the higher the drying temperature, the better the flatness of the film.

  Japanese Patent Application Laid-Open No. 2002-248639, which is an invention that reduces vertical and horizontal dimensional fluctuations during storage under high temperature and high humidity conditions, continuously casts a cellulose ester solution on a support. In the method for producing a film to be peeled and dried, the invention is described in which the drying shrinkage satisfies the formula: 0 ≦ dry shrinkage (%) ≦ 0.1 × residual solvent amount (%) when peeling. Has been. Further, as a preferred embodiment, 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 30% by mass while holding 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% by mass, the amount of residual solvent at the exit is 4 to 20% by mass, and the cellulose ester film is removed by tenter conveyance. It is disclosed that the tension to be conveyed increases from the entrance to the exit of the tenter conveyance, the tension to convey the cellulose ester film by the tenter conveyance and the tension in the width direction of the cellulose ester film are substantially equal. Yes.

  In order to obtain a film having a thin film thickness and excellent optical isotropy and flatness, Japanese Patent Application Laid-Open No. 2000-239403 describes a residual solvent ratio X during peeling and a residual solvent ratio when introduced into a tenter. It is disclosed that film formation is performed with the relationship of Y being in the range of 0.3X ≦ Y ≦ 0.9X.

  Japanese Patent Application Laid-Open No. 2002-286933 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. It is preferable to stretch the film at a temperature below the glass transition point of the resin. On the other hand, when the film formed by casting is stretched under solvent-impregnated conditions, the dried film is brought into contact with the solvent again. It is disclosed that it can be impregnated with a solvent and stretched.

(Retardation raising agent)
In order to express a desired retardation value, it is preferable to use a retardation increasing agent.
In this specification, the term “retardation increasing agent” means a cellulose acylate produced in the same manner except that the Re retardation value measured at a wavelength of 550 nm of a cellulose acylate film containing an additive does not contain the additive. It means “additive” which is 20 nm or more higher than the Re retardation value (unstretched state) measured at a wavelength of 550 nm of the film. The increase in retardation value is preferably 30 nm or more, more preferably 40 nm or more, and most 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 more preferable to use in the range of 5 to 5 parts by mass, and most preferable to use in the range of 0.5 to 2 parts by mass. Two or more types of 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.

In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring.
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.

The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. preferable.
The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-

The aromatic ring and the linking group may have a substituent.
Examples of the substituent include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.

The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl.
The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl.
The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.

The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl.
The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy.
The number of carbon atoms of the alkoxy group is preferably 1 to 8. The alkoxy group may further have a substituent (eg, alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy.
The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl.
The number of carbon atoms of the alkoxycarbonylamino group is preferably 2 to 10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include methylthio, ethylthio and octylthio.
The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl.
The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide.
The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamido group include methanesulfonamido, butanesulfonamido and n-octanesulfonamido.
The number of carbon atoms of the aliphatic substituted amino group is preferably 1 to 10. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino.
The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl.
The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl.
The number of carbon atoms in the aliphatic substituted ureido group is preferably 2 to 10. Examples of the aliphatic substituted ureido group include methylureido.
Examples of non-aromatic heterocyclic groups include piperidino and morpholino.
The molecular weight of the retardation increasing agent is preferably 300 to 800.

  In the present invention, a rod-shaped compound having a linear molecular structure can be preferably used in addition to a compound using a 1,3,5-triazine ring. The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically 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. The molecular structure being linear means that in the thermodynamically most stable structure obtained by calculation as described above, the angle of the main chain constituting the molecular structure is 140 degrees or more.

As the rod-shaped compound having at least two aromatic rings, a compound represented by the following general formula (1) is preferable.
General formula (1): Ar1-L1-Ar2
In the general formula (1), Ar1 and Ar2 are each independently an aromatic group.

In the present invention, the aromatic group includes an aryl group (aromatic hydrocarbon group), a substituted aryl group, an aromatic heterocyclic group, and a substituted aromatic heterocyclic group.
An aryl group and a substituted aryl group are more preferable than an aromatic heterocyclic group and a substituted aromatic heterocyclic group. The heterocycle of the aromatic heterocyclic group is generally unsaturated. 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 a hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferable, and a nitrogen atom or a sulfur atom is more preferable. As the aromatic ring of the aromatic group, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring and a pyrazine ring are preferable, and a benzene ring is particularly preferable. .

  Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, alkylamino group (eg, methylamino, ethylamino) , Butylamino, dimethylamino), nitro, sulfo, carbamoyl, alkylcarbamoyl groups (eg, N-methylcarbamoyl, N-ethylcarbamoyl, N, N-dimethylcarbamoyl), sulfamoyl, alkylsulfamoyl groups (eg, N- Methylsulfamoyl, N-ethylsulfamoyl, N, N-dimethylsulfamoyl), ureido, alkylureido groups (eg, N-methylureido, N, N-dimethylureido, N, N, N-trimethylureido) ), Alkyl groups (eg, methyl, ethyl, propyl, butyl, pentyl, Butyl, octyl, isopropyl, s-butyl, t-amyl, cyclohexyl, cyclopentyl), alkenyl groups (eg, vinyl, allyl, hexenyl), alkynyl groups (eg, ethynyl, butynyl), acyl groups (eg, formyl, acetyl, Butyryl, hexanoyl, lauryl), acyloxy groups (eg, acetoxy, butyryloxy, hexanoyloxy, lauryloxy), alkoxy groups (eg, methoxy, ethoxy, propoxy, butoxy, pentyloxy, heptyloxy, octyloxy), aryloxy groups (Eg, phenoxy), alkoxycarbonyl group (eg, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl, heptyloxycarbonyl), aryloxycarbo Group (eg, phenoxycarbonyl), alkoxycarbonylamino group (eg, butoxycarbonylamino, hexyloxycarbonylamino), alkylthio group (eg, methylthio, ethylthio, propylthio, butylthio, pentylthio, heptylthio, octylthio), arylthio group (eg, , Phenylthio), alkylsulfonyl groups (eg, methylsulfonyl, ethylsulfonyl, propylsulfonyl, butylsulfonyl, pentylsulfonyl, heptylsulfonyl, octylsulfonyl), amide groups (eg, acetamido, butyramide, hexylamide, laurylamide) and non- Aromatic heterocyclic groups (eg, morpholyl, pyrazinyl) are included.

Substituents of substituted aryl groups and substituted aromatic heterocyclic groups include halogen atoms, cyano, carboxyl, hydroxyl, amino, alkyl-substituted amino groups, acyl groups, acyloxy groups, amide groups, alkoxycarbonyl groups, alkoxy groups, alkylthios. And groups and alkyl groups are preferred.
The alkyl part and alkyl group of the alkylamino group, alkoxycarbonyl group, alkoxy group and alkylthio group may further have a substituent. Examples of the alkyl moiety and the substituent of the alkyl group include halogen atom, hydroxyl, carboxyl, cyano, amino, alkylamino group, nitro, sulfo, carbamoyl, alkylcarbamoyl group, sulfamoyl, alkylsulfamoyl group, ureido, alkylureido Group, alkenyl group, alkynyl group, acyl group, acyloxy group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, alkoxycarbonylamino group, alkylthio group, arylthio group, alkylsulfonyl group, amide group and non-aromatic An aromatic heterocyclic group is included. As the substituent for the alkyl moiety and the alkyl group, a halogen atom, hydroxyl, amino, alkylamino group, acyl group, acyloxy group, acylamino group, alkoxycarbonyl group and alkoxy group are preferable.

In the general formula (1), L1 is a divalent linking group selected from an alkylene group, an alkenylene group, an alkynylene group, —O—, —CO—, and a combination thereof.
The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group.
The alkylene group preferably has 1 to 20 carbon atoms, more preferably 1 to 15, more preferably 1 to 10, still more preferably 1 to 8, and most preferably 1 to 6 carbon atoms. It is.

The alkenylene group and the alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure.
The number of carbon atoms of the alkenylene group and the alkynylene group is preferably 2 to 10, more preferably 2 to 8, further preferably 2 to 6, further preferably 2 to 4, and most preferably 2. (Vinylene or ethynylene).
The arylene group preferably has 6 to 20 carbon atoms, more preferably 6 to 16, and still more preferably 6 to 12.

In the molecular structure of the general formula (1), the angle formed by Ar1 and Ar2 across L1 is preferably 140 degrees or more.
As the rod-like compound, a compound represented by the following formula (2) is more preferable.
General formula (2): Ar1-L2-X-L3-Ar2
In the general formula (2), Ar1 and Ar2 are each independently an aromatic group. The definition and examples of the aromatic group are the same as those for Ar1 and Ar2 in the general formula (I).

In the general formula (2), L2 and L3 are each independently a divalent linking group selected from an alkylene group, —O—, —CO— and a group consisting of a combination thereof.
The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure.
The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 6, still more preferably 1 to 4, and 1 or 2 (methylene Or ethylene).
L2 and L3 are particularly preferably —O—CO— or —CO—O—.

In the general formula (2), X is 1,4-cyclohexylene, vinylene or ethynylene.
Specific examples of the compound represented by the general formula (1) are shown below.

  Specific examples (1) to (34), (41), and (42) have two asymmetric carbon atoms at the 1-position and the 4-position of the cyclohexane ring. However, since the specific examples (1), (4) to (34), (41), and (42) have a symmetrical meso type molecular structure, there are no optical isomers (optical activity), and geometric isomers (trans Type and cis type). The trans type (1-trans) and cis type (1-cis) of specific example (1) are shown below.

As described above, the rod-like compound preferably has a linear molecular structure. Therefore, the trans type is preferable to the cis type.
Specific examples (2) and (3) have optical isomers (a total of four isomers) in addition to geometric isomers. As for geometric isomers, the trans type is similarly preferable to the cis type. The optical isomer is not particularly superior or inferior, and may be D, L, or a racemate.
In specific examples (43) to (45), the central vinylene bond includes a trans type and a cis type. For the same reason as above, the trans type is preferable to the cis type.

Other preferred compounds are shown below.

Two or more rod-shaped compounds whose maximum absorption wavelength (λmax) is 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. References include Mol. Cryst. Liq. Cryst., 53, 229 (1979), 89, 93 (1982), 145, 111 (1987), 170, 43 Page (1989), J. Am. Chem. Soc., 113, 1349 (1991), 118, 5346 (1996), 92, 1582 (1970), J. Org Chem., 40, 420 (1975), Tetrahedron, 48, 16, 3437 (1992).
The addition amount of the retardation enhancer is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, based on the amount of the polymer.

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

(Optical compensation film)
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 devices. The optical compensation film of the present invention may be disposed between the observer-side polarizing plate and the liquid crystal cell, 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 a liquid crystal display device as an independent member, or a protective film that protects a polarizing film is provided with optical characteristics to function as a transparent film, and as a member of a polarizing plate, liquid crystal It can also be incorporated inside the display device. The optical compensation film of the present invention has at least two layers of the cellulose acylate film of the present invention and an optically anisotropic layer having optical anisotropy in the plane. An alignment film for controlling the alignment of the liquid crystalline compound in the optically anisotropic layer may be provided between the cellulose acylate film and the optically anisotropic layer. Moreover, as long as the optical properties described later are satisfied, the cellulose acylate and the optically anisotropic layer may each be composed of two or more layers. First, each component of the optical compensation film of the present invention will be described in detail.

[Optically anisotropic layer]
The optical compensation film of the present invention has at least one optically anisotropic layer formed from a liquid crystalline compound. The optically anisotropic layer may be formed directly on the surface of the cellulose acylate film, or may be formed on the alignment film by forming an alignment film on the cellulose acylate film. In addition, it is possible to produce the optical compensation film of the present invention by transferring a liquid crystalline compound layer formed on another substrate onto a cellulose acylate 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, see Chapter 4, Chapter 7 and Chapter 11 of the Chemistry of the Quarterly Chemical Review Vol. 22 Liquid Crystal Chemistry (1994) edited by the Chemical Society of Japan, and the 142th Committee of the Japan Society for the Promotion of Science. 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 its alignment state. The polymerizable group is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most 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, a linking group is introduced between the discotic core and the polymerizable group. Accordingly, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (III).

Formula (III)
D (-LQ) _n
In the formula, D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.

  An example of the disk-shaped core (D) is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

  In the formula (III), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. A divalent linking group selected is preferable. The divalent linking group (L) is a divalent combination of at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO-, -NH-, -O-, and S-. The linking group is more preferable. The divalent linking group (L) is most preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and O- are combined. preferable. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms.

  Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, alkyl group).

L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-

L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AR-O-AL-CO-
L17: -O-CO-AR-O-AL-O-CO-
L18: -O-CO-AR-O-AL-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L20: -S-AL-
L21: -S-AL-O-
L22: -S-AL-O-CO-
L23: -S-AL-S-AL-
L24: -S-AR-AL-

The polymerizable group (Q) of the formula (III) is determined according to the type of polymerization reaction. The polymerizable group (Q) is preferably an unsaturated polymerizable group or an epoxy group, more preferably an unsaturated polymerizable group, and most preferably an ethylenically unsaturated polymerizable group.
In formula (III), n is an integer of 4-12. A specific number is determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.

  In the present invention, in the optically anisotropic layer, the molecules of the rod-like compound or the discotic compound are fixed in an oriented state. The alignment average direction of the molecular symmetry axis of the liquid crystal compound at the interface on the cellulose acylate film side has an intersecting angle with the slow axis in the plane of the cellulose acylate film of about 45 degrees. In this specification, “approximately 45 °” refers to an angle in the range of 45 ° ± 5 °, preferably 42 to 48 °, and more preferably 43 to 47 °. The average direction of the molecular symmetry axis of the liquid crystalline compound in the optically anisotropic layer is preferably 43 ° to 47 ° with respect to the longitudinal direction of the support (that is, the fast axis direction of the support).

  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, when an alignment film for forming an optically anisotropic layer is produced by rubbing treatment, rubbing treatment is performed in a direction of 45 ° with respect to the slow axis of the cellulose acylate film. An optically anisotropic layer having a molecular symmetry axis and an orientation average direction at least at the cellulose acylate film interface of 45 ° with respect to the slow axis of the cellulose acylate film can be formed. For example, the optical compensation film of the present invention can be continuously produced by using a long cellulose acylate film whose slow axis is parallel to the longitudinal direction. Specifically, a coating film for forming an alignment film is continuously applied to the surface of a long cellulose acylate film to prepare a film, and then the surface of the film is continuously 45 ° in the longitudinal direction. An alignment film is produced by rubbing in the direction, and then a coating liquid for forming an optically anisotropic layer containing a liquid crystalline compound is continuously applied onto the prepared alignment film to align the molecules of the liquid crystalline compound. Then, the optically anisotropic layer can be produced by fixing in this state, 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 in 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 relative to the slow axis of the cellulose acylate film. It is preferably about 45 °, more preferably 42 to 48 °, and even 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 can change the tilt angle of the liquid crystal compound or do not inhibit the alignment. Is preferred. Polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) are 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. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass with respect to the discotic liquid crystalline compound so as not to inhibit the orientation of the discotic liquid crystalline compound, and 0.1 to 8% by mass. 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, more preferably 70 to 170 ° C.

  In the present invention, the optically anisotropic layer 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 even 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 microns, more preferably 0.5 to 15 microns, and most preferably 1 to 10 microns.

[Alignment film]
The optical compensation film of the present invention may have an alignment film between the cellulose acylate film of the present invention and the optically anisotropic layer. In addition, an alignment film is used only when an optically anisotropic layer is produced, and after producing an optically anisotropic layer on the oriented film, only the optically anisotropic layer is placed on the cellulose acylate film of the present invention. You may transcribe.
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 composed 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 crosslinking in order to suppress the dust generation of the alignment film. A 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 most 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, polyville alcohol, and modified polyvinyl alcohol, and gelatin, polyville alcohol, and modified polyvinyl alcohol. Are preferable, and in particular, polyvinyl alcohol and modified polyvinyl alcohol can be mentioned.
In the case of directly coating polyvil alcohol and modified polyvinyl alcohol on the cellulose acylate film of the present invention, a method in which a hydrophilic undercoat layer is provided or a saponification treatment described in Japanese Patent Application No. 2000-369004 is preferably used. The

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 3000.
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). As a polymerization degree, the range of 100-3000 is preferable. Among these, unmodified or modified polyvinyl alcohol having a saponification degree of 80 to 100% is preferable, and unmodified or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% is more preferable.

As the modified polyvinyl alcohol used for the alignment film, a reaction product of a compound represented by the following general formula (6) and polyvinyl alcohol is preferable.
General formula (6):

In the formula, R ^1d represents an unsubstituted alkyl group or an alkyl group substituted with an acrylolyl group, a methacryloyl group or an epoxy group, W represents a halogen atom, an alkyl group or an alkoxy group, and X ^1d represents an active ester, an acid This represents a group of atoms necessary for forming an anhydride or acid halide, l represents 0 or 1, and n represents an integer of 0 to 4.

Moreover, as the modified polyvinyl alcohol used for the alignment film, a reaction product of a compound represented by the following general formula (7) and polyvinyl alcohol is also preferable.
General formula (7):

In the formula, X ^2d represents an atomic group necessary for forming an active ester, an acid anhydride or an acid halide, and m represents an integer of 2 to 24.

The polyvinyl alcohol used for reacting with the compounds represented by the general formula (6) and the general formula (7) includes the unmodified polyvinyl alcohol and the copolymer-modified one, that is, chain transfer. Examples include modified products of polyvinyl alcohol such as modified products and modified products by block polymerization. Preferred examples of the specific modified polyvinyl alcohol are described in detail in JP-A-8-338913.
When using a hydrophilic polymer such as polyvinyl alcohol for the alignment film, it is preferable to control the moisture content from the viewpoint of the degree of hardening, preferably 0.4% to 2.5%, 0.6% More preferably, it is -1.6%. 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 microns or less.

[Polarizer]
In the present invention, a polarizing plate comprising a polarizing film and a pair of protective films sandwiching the polarizing film can be used. For example, a polarizing film obtained by dyeing a polarizing film made of a polyvinyl alcohol film or the like with iodine, stretching, and laminating both surfaces with a protective film can be used. The polarizing plate is disposed outside the liquid crystal cell. It is preferable that a pair of polarizing plates each including a polarizing film and a pair of protective films sandwiching the polarizing film are disposed with the liquid crystal cell interposed therebetween. As described above, the protective film disposed on the liquid crystal cell side may be the optical compensation film (cellulose acylate film) of the present invention.

"adhesive"
The adhesive between the polarizing film and the protective film is not particularly limited, and examples thereof include PVA resin (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 microns after drying, and particularly preferably 0.05 to 5 microns.

《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 film for polarizing film is stretched and then contracted to reduce the volatile content, but after drying or after the transparent protective film is bonded to at least one side during drying, It is preferable to have a post-heating step. In an aspect in which the transparent protective film also serves as a support for the optically anisotropic layer functioning as a transparent film, after the transparent support having the transparent protective film on one side and the optically anisotropic layer on the opposite side is bonded together It is preferable to post-heat. As a specific attaching method, during the film drying process, a transparent protective film is attached to the polarizing film with 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 removed, 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 condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° C. or higher, more preferably 40 ° C. to 100 ° C., and further preferably 50 ° C. to 90 ° C. 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 polarizing plate comprising a transparent protective film, a polarizer and a transparent support related to the present invention are commercially available super high contrast products (for example, Sanritz Corporation). Manufactured by HLC2-5618 and the like) and preferably 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 rate of change in light transmittance before and after standing 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 in polarization degree is preferably 1% or less, more preferably 0.1% or less, based on the absolute value.

[Example 1]
[Preliminary experiment 1]
(Spectrum measurement of retardation increasing agent)
The ultraviolet-visible region (UV-vis) spectrum of the retardation increasing agent (10-trans), (41-trans) and (29-trans) was measured.
The retardation increasing agent was dissolved in tetrahydrofuran (without stabilizer (BHT)), and the concentration was adjusted to 10 ⁻⁵ mol / dm ³ . The solution thus prepared was measured with a measuring instrument (manufactured by Hitachi, Ltd.). The results are shown in Table 1.

Table 1 ─────────────────────────────────────────
Retardation raising agent Absorption maximum wavelength (λmax) Absorption coefficient at absorption maximum (ε)
────────────────────────────────────────
10-trans 220nm 15000
41-trans 230nm 16000
29-trans 240nm 20000
────────────────────────────────────────

(Preparation of cellulose acylate film)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

────────────────────────────────────────
Material / solvent composition Outer layer side Inner layer side ────────────────────────────────────────
Cellulose acetate Degree of substitution 2.87 Degree of substitution 2.75
Degree of acetylation 60.9% Degree of acetylation 59.5%
100 parts by mass 100 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass 7.8 parts by mass Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass 3.9 parts by mass Methylene chloride (first solvent) 300 parts by mass 300 parts by mass Methanol (second solvent) 45 parts by mass 45 parts by mass Dye (manufactured by Sumika Finechem Co., Ltd., 360FP) 0.0009 parts by mass 0.0009 parts by mass retardation increasing agent (41-trans) 1.32 parts by mass Part 1.32 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., it was dried for 1 minute, peeled off, and then stretched 28% in the width direction using a tenter with a drying air of 140 ° C. Then, it dried for 20 minutes with 135 degreeC drying air, and manufactured the cellulose acetate support body (PK-1) whose residual solvent amount is 0.3 mass%.
The width of the obtained support (PK-1) was 1340 mm, and the thickness was 88 μm. Using an ellipsometer (M-150, manufactured by JASCO Corporation), 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 45. 0.0 nm. Moreover, it was 160.0 nm when the retardation value (Rth) in wavelength 550nm was measured.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 650 nm were measured and found to be 31 nm and 59 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 650nm was measured, they were 171nm and 155nm, respectively.

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 formed on the band surface side of the produced support (PK-1). Was applied at 10 cc / m ² and kept at a temperature of about 40 ° C. for 30 seconds, then 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 PK-1 with respect to pure water was found to be 42 °.

(Preparation of alignment film)
On this PK-1 (alkali-treated surface), 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 ────────────────────────────────────────
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight Citrate ester (AS3 manufactured by Sankyo Chemical) 0.35 parts by weight ──────── ────────────────────────────────

(Rubbing process)
PK-1 is transported at a speed of 20 m / min, a rubbing roll (300 mm diameter) is set so as to be rubbed at 45 ° with respect to the longitudinal direction, rotated at 650 rpm, and an alignment film installation surface of PK-1 The rubbing process was given to. The contact length between the rubbing roll and PK-1 was set to be 18 mm.

(Formation of optically anisotropic layer)
On the alignment film, 41.01 kg of the following discotic liquid crystalline compound, 4.06 kg of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.45 Kg, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.35 Kg, sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.45 Kg, 102 kg To the coating solution dissolved in methyl ethyl ketone, 0.1 kg of a fluoroaliphatic group-containing copolymer (Megafac F780 manufactured by Dainippon Ink Co., Ltd.) is added, and the # 3.0 wire bar is rotated 391 times to the film transport direction. Rotate in the same direction and continuously on the alignment film surface of PK-1 being conveyed at 20 m / min It was applied to.

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 130 ° C. drying zone. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, the film is transported to a drying zone at 80 ° C., and an ultraviolet ray with an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 100 ° C. Irradiation was carried out for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the orientation. 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 (KH-1) was produced.
The film surface temperature of the discotic liquid crystal compound layer was 127 ° C., and the viscosity of the layer at this temperature was 695 cp. The viscosity was measured with a heating E-type viscosity system for a liquid crystal layer (excluding the solvent) having the same composition ratio as the layer.

A part of the produced roll-shaped optical compensation film (KH-1) was cut out and used as a sample to measure optical characteristics. The Re retardation value of the optically anisotropic layer measured at a wavelength of 550 nm in an environment of 25 ° C. and 55% RH was 30.0 nm. The angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface was continuously changed in the depth direction of the layer, and was 30 ° on average. Furthermore, when only the optically anisotropic layer was peeled from the sample and the average direction of the molecular symmetry axis of the optically anisotropic layer was measured, it was 45 ° with respect to the longitudinal direction of the optical compensation film (KH-1). It was.
Furthermore, when the polarizing plate was placed in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, no unevenness was detected even when viewed from the front and the direction inclined to 60 ° from the normal.

[Example 2]
(Preparation of cellulose acylate film PK-2)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

────────────────────────────────────────
Material / solvent composition Outer layer side Inner layer side ────────────────────────────────────────
Cellulose acetate Degree of substitution 2.87 Degree of substitution 2.75
Degree of acetylation 60.9% Degree of acetylation 59.5%
100 parts by mass 100 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass 5.3 parts by mass Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass 2.7 parts by mass Methylene chloride (first solvent) 300 parts by mass 300 parts by mass Methanol (second solvent) 45 parts by mass 45 parts by mass Dye (manufactured by Sumika Finechem Co., Ltd., 360FP) 0.0009 parts by mass 0.0009 parts by mass retardation increasing agent (41-trans) 1.32 parts by mass Part −
Retardation raising agent (below)-4.45 parts by mass ------------------------------ ───

Retardation raising agent

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., it was dried for 1 minute, peeled off, and then stretched 16% in the width direction using a tenter with a drying air of 140 ° C. Then, it dried for 20 minutes with 135 degreeC drying air, and manufactured the cellulose acetate support body (PK-2) whose residual solvent amount is 0.3 mass%.
The obtained support (PK-2) had a width of 1340 mm and a thickness of 88 μm. Using an ellipsometer (M-150, manufactured by JASCO Corporation), 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 40. 0.0 nm. Moreover, it was 200.0 nm when the retardation value (Rth) in wavelength 550nm was measured.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 650 nm were measured and found to be 22 nm and 58 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 650nm was measured, they were 225nm and 191nm, respectively.
In the same manner as in Example 1 (PK-1), an alignment film was placed after the alkali treatment, and the alignment film surface was rubbed.

(Formation of optically anisotropic layer)
On the alignment film, 41.01 kg of the following discotic liquid crystalline compound, 4.06 kg of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.45 Kg, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.35 Kg, sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 0.45 Kg, 102 kg 0.1 kg of fluoroaliphatic group-containing copolymer (Megafac F780, Dainippon Ink, Inc.) is added to the coating solution dissolved in methyl ethyl ketone, and the # 3.4 wire bar is rotated 391 times to transport the film. Rotate in the same direction as the PK-1, which is transported at 20 m / min. Was applied.

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 130 ° C. drying zone. The discotic liquid crystal compound was aligned by heating for 2 seconds. Next, the film is transported to a drying zone at 80 ° C., and UV light having an illuminance of 600 mW is applied by an ultraviolet irradiation device (ultraviolet lamp: output 160 W / cm, emission length 1.6 m) with the surface temperature of the film being about 80 ° C. Irradiation was carried out for 4 seconds to advance the crosslinking reaction, and the discotic liquid crystal compound was fixed to the orientation. 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 (KH-2) was produced.
The film surface temperature of the discotic liquid crystal compound layer was 127 ° C., and the viscosity of the layer at this temperature was 695 cp. The viscosity was measured with a heating E-type viscosity system for a liquid crystal layer (excluding the solvent) having the same composition ratio as the layer.

A part of the produced roll-shaped optical compensation film (KH-2) was cut out and used as a sample to measure optical characteristics. The Re retardation value of the optically anisotropic layer measured at a wavelength of 550 nm in an environment of 25 ° C. and 55% RH was 36.0 nm. In addition, the angle (tilt angle) between the disc surface of the discotic liquid crystal compound in the optically anisotropic layer and the support surface was continuously changed in the depth direction of the layer, and averaged 32 °. Furthermore, only the optically anisotropic layer was peeled from the sample, and the average direction of the axis of molecular symmetry of the optically anisotropic layer was measured. The result was 45 ° with respect to the longitudinal direction of the optical compensation film (KH-2). It was.
Furthermore, when the polarizing plate was placed in a crossed Nicol arrangement and the unevenness of the obtained optical compensation sheet was observed, no unevenness was detected even when viewed from the front and the direction inclined to 60 ° from the normal.

[Example 3]
(Preparation of cellulose acylate film PK-3)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

────────────────────────────────────────
Material / solvent composition Outer layer side Inner layer side ────────────────────────────────────────
Cellulose acetate degree of substitution 2.87 degree of substitution 2.64
60.9% acetylation degree 58.0% acetylation degree
100 parts by mass 100 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass 5.3 parts by mass Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass 2.7 parts by mass Methylene chloride (first solvent) 300 parts by mass 300 parts by mass Methanol (second solvent) 45 parts by mass 45 parts by mass Dye (manufactured by Sumika Finechem Co., Ltd., 360FP) 0.0009 parts by mass 0.0009 parts by mass retardation increasing agent (10-trans) 1.32 parts by mass 3.34 parts by mass ────────────────────────────────────────

A cellulose acylate film (PK-3) was produced in the same manner as in Example 1 (PK-1).
The obtained support (PK-3) had a width of 1340 mm and a thickness of 80 μm. Using an ellipsometer (M-150, manufactured by JASCO Corporation), 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 45. 0.0 nm. Moreover, it was 160.0 nm when the retardation value (Rth) in wavelength 550nm was measured.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 650 nm were measured and found to be 42 nm and 48 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 650nm was measured, they were 164nm and 158nm, respectively.
In the same manner as in Example 1 (PK-1), an alignment film is installed after alkali treatment, a rubbing process is performed on the surface of the alignment film, an optically anisotropic layer is coated thereon, and an optical compensation film (KH- 3) was produced.

[Example 4]
(Preparation of cellulose acylate film PK-3)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.

────────────────────────────────────────
Material / solvent composition Outer layer side Inner layer side ────────────────────────────────────────
Cellulose acetate degree of substitution 2.87 degree of substitution 2.64
60.9% acetylation degree 58.0% acetylation degree
100 parts by mass 100 parts by mass Triphenyl phosphate (plasticizer) 7.8 parts by mass 5.3 parts by mass Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by mass 2.7 parts by mass Methylene chloride (first solvent) 300 parts by mass 300 parts by mass Methanol (second solvent) 45 parts by mass 45 parts by mass Dye (manufactured by Sumika Finechem Co., Ltd., 360FP) 0.0009 parts by mass 0.0009 parts by mass retardation increasing agent (10-trans) 3.32 parts by mass Part 1.35 parts by mass retardation increasing agent (below)-4.65 parts by mass ------------------------- ─────────

Retardation raising agent

A cellulose acylate film (PK-3) was produced in the same manner as in Example 1 (PK-1).
The obtained support (PK-3) had a width of 1340 mm and a thickness of 80 μm. Using an ellipsometer (M-150, manufactured by JASCO Corporation), 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 25. 0.0 nm. Further, the retardation value (Rth) at a wavelength of 550 nm was measured and found to be 300.0 nm.
Similarly, the retardation values (Re) at wavelengths of 450 nm and 650 nm were measured and found to be 22 nm and 40 nm, respectively. Moreover, when the retardation value (Rth) in wavelength 450nm and 650nm was measured, they were 320nm and 280nm, respectively.
In the same manner as in Example 2 (PK-2), an alignment film is installed after alkali treatment, a rubbing process is performed on the surface of the alignment film, an optically anisotropic layer is coated thereon, and an optical compensation film (KH- 4) was produced.

[Example 5]
<Preparation of polarizing plate>
A polarizing film was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and the optical compensation film (KH-01) prepared in Example 1 was attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the retardation plate (KH-01) were arranged in parallel.
A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. In this way, a polarizing plate was 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 opposed to each other so that the rubbing directions were parallel to each other, and the cell gap was set to 4.6 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.
Two produced polarizing plates were bonded so as to sandwich the produced bend alignment cell. 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 optically anisotropic layer facing it were 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. Applying a voltage that minimizes the transmittance at the front, that is, a black voltage, the black display transmittance (%) at the azimuth angle 0 °, polar angle 60 ° viewing angle, and azimuth angle 0 ° polar angle 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. In addition, using a measuring instrument (EZ-Contrast 160D, manufactured by ELDIM) as a contrast ratio with 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 1.

[Example 6]
<Preparation of polarizing plate>
A polarizing film was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and the optical compensation film (KH-02) prepared in Example 2 was attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizing film and the slow axis of the retardation plate (KH-02) were arranged in parallel.
A commercially available cellulose triacetate film (Fujitac TD80UF, manufactured by Fuji Photo Film Co., Ltd.) was subjected to saponification treatment and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. In this way, a polarizing plate was 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 6.3 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.
Two produced polarizing plates were bonded so as to sandwich the produced bend alignment cell. 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 optically anisotropic layer facing it were antiparallel.
A rectangular wave voltage of 55 Hz was applied to the liquid crystal cell. A normally white mode with 2 V white display and 7 V 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 2. 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 2.

Table 2 ─────────────────────────────────────────
Re / Rth
A: 450nm B: 550nm C: 650nm A / B C / B Transmittance Color shift ──────────────────────────────── ─────────
Example 5 0.18 0.28 0.38 0.64 1.36 0.04 0.05
Example 6 0.10 0.20 0.30 0.50 1.50 0.016 0.05
────────────────────────────────────────
(註)
Transmittance: Black display transmittance (%) at azimuth angle 0 °, polar angle 60 ° viewing angle
Color shift: Color shift Δx between azimuth angle 0 degree polar angle 60 degrees and azimuth angle 180 degrees polar angle 60 degrees

  From the results shown in Table 2, Re / Rth (450 nm) is 0.49 to 0.91 times Re / Rth (550 nm), and Re / Rth (650 nm) is 1 of Re / Rth (550 nm). The liquid crystal display device Examples 1 to 4 of the embodiment of the present invention which are 0.08 to 1.51 times each have a low transmittance at the time of black display at a polar angle of 60 ° as compared with Comparative Example 1. It can also be seen that the color shift from the front is small. Further, from the results in Table 1, when Re / Rth (450 nm) is 0.61 times Re / Rth (550 nm) and Re / Rth (650 nm) is 1.38 times Re / Rth (550 nm). It can be understood that both transmittance and color shift are minimized.

Table 3 ─────────────────────────────────────────
Liquid crystal viewing angle (contrast ratio of 10 or more and no black-side gradation inversion)
Display device Up / Down Left / Right ────────────────────────────────────────
Example 5 80 ° 80 ° 80 ° Example 6 80 ° 80 ° 80 ° ───────────────────────────────── ────────
(Ii) Black-side gradation inversion: inversion between L1 and L2

It is a schematic diagram which shows the structural example of the liquid crystal display device of OCB mode according to this invention. 6 is a chart showing the relationship between the angle of the slow axis and Re / Rth when light traveling in an oblique direction is incident on a cellulose acylate film. FIG. 2 is a schematic diagram of a Poincare sphere showing a change in the polarization state of G light incident on the liquid crystal display device of FIG. 1 from the left 60 ° (a) or the right 60 ° (b). It is a schematic diagram which shows the structure of the liquid crystal display device of the conventional OCB mode. FIG. 5 is a schematic diagram of a Poincare sphere showing changes in polarization state of light incident on the liquid crystal display device of FIG. 4 from left 60 ° (a) or right 60 ° (b) for R, G, and B, respectively. FIG. 2 is a schematic diagram of a Poincare sphere showing changes in the polarization state of light incident on the liquid crystal display device of FIG. 1 from the left 60 ° (a) or the right 60 ° (b) for R, G, and B, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Polarizing film 2,102 Transmission axis 13a, 103a, 113a Cellulose acylate film 14a, 104a, 114a Slow axis 5, 9 Optical anisotropic layer 5a, 9a Average orientation direction 6, 8 Substrate 7 Liquid crystal layer RD Rubbing direction

Claims (10)

In at least one direction a stretch processed transparent cellulose acylate film, the substitution degree of the cellulose acylate in the thickness direction of the film varies 0.05 or more within the range of 2.00 to 3.00, the following formula Cellulose acylate film characterized by having optical anisotropy satisfying (I), (II) and (III) :
(I) 0.40 <{Re / Rth (450)} / {Re / Rth (550)} <0.95
(II) 1.05 <{Re / Rth (650)} / {Re / Rth (550)} <1.93
(III) 70 nm <Rth (550) <400 nm
[In the formula, Re / Rth (450) is a ratio of in-plane retardation value measured at a wavelength of 450 nm / thickness direction retardation value measured at a wavelength of 450 nm; Re / Rth (550) is a wavelength of 550 nm. Is the ratio of the in-plane retardation value measured in step / thickness direction retardation value measured at a wavelength of 550 nm; Re / Rth (650) is measured in the in-plane retardation value measured at a wavelength of 650 nm / wavelength of 650 nm. The ratio of retardation values in the thickness direction; and Rth (550) is the retardation value in the thickness direction measured at a wavelength of 550 nm .   The cellulose acylate film according to claim 1, further comprising a retardation increasing agent.   The cellulose acylate according to claim 1 or 2, wherein the substitution degree of the cellulose acylate film on the higher substitution side is 2.75 to 2.92, and the substitution degree on the lower side is 2.64 to 2.83. Film.   The cellulose acylate film according to any one of claims 1 to 3, wherein the cellulose acylate film is stretched in a state where a residual solvent is present on the low substitution degree side of the cellulose acylate film. It is formed by co-casting of two or more layers, and the difference between the substitution degree of cellulose acylate contained in one layer and the substitution degree of cellulose acylate contained in another layer is 0.05 or more the cellulose acylate fill-beam according to any one of claims 1 to 4. An optical compensation film comprising a transparent cellulose acylate film stretched in at least one direction and a liquid crystalline compound and an optically anisotropic layer having in-plane optical anisotropy, the thickness of the cellulose acylate film The degree of substitution of cellulose acylate varies by 0.05 or more in the range of 2.00 to 3.00, and the cellulose acylate film satisfies the following formulas (I), (II) and (III). The orientation of the liquid crystal compound is fixed in an oriented state in the optically anisotropic layer, and the orientation average direction at the cellulose acylate film side interface of the molecular symmetry axis of the liquid crystal compound is the cellulose acylate film surface. The crossing angle between the direction orthogonally projected inward and the slow axis in the plane of the cellulose acylate film is approximately 45 degrees. Amortization film:
(I) 0.40 <{Re / Rth (450)} / {Re / Rth (550)} <0.95
(II) 1.05 <{Re / Rth (650)} / {Re / Rth (550)} <1.93
(III) 70 nm <Rth (550) <400 nm
[In the formula, Re / Rth (450) is a ratio of in-plane retardation value measured at a wavelength of 450 nm / thickness direction retardation value measured at a wavelength of 450 nm; Re / Rth (550) is a wavelength of 550 nm. Is the ratio of the in-plane retardation value measured in step / thickness direction retardation value measured at a wavelength of 550 nm; Re / Rth (650) is measured in the in-plane retardation value measured at a wavelength of 650 nm / wavelength of 650 nm. The ratio of retardation values in the thickness direction; and Rth (550) is the retardation value in the thickness direction measured at a wavelength of 550 nm . 7. The optical compensation film according to claim 6, wherein the liquid crystal compound is a discotic liquid crystal compound . A polarizing plate comprising the cellulose acylate film according to any one of claims 1 to 5 or the optical compensation film according to claim 6 or 7 and a polarizer . A liquid crystal display device comprising a liquid crystal cell and the polarizing plate according to claim 8 . The liquid crystal display device according to claim 9, wherein the liquid crystal cell is a VA method or an OCB method .

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