JP2014077879A - Liquid crystal display device and driving method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a TN type liquid crystal display device in a birefringence mode which hardly causes halation in a halftone display while maintaining a state of suppressing downward gradation inversion.SOLUTION: A liquid crystal display device includes: a pair of polarizers; a liquid crystal cell which includes at least a pair of substrates having an electrode that constitutes a pixel on at least one of counter surfaces, and a liquid crystal layer disposed between the pair of substrates and showing twisted alignment at about 90° twist angle; and an optical compensation film disposed between each of the pair of polarizers and the liquid crystal cell. In the display device, the pair of polarizers and the liquid crystal layer are disposed to give a birefringence mode; and the optical compensation film is a laminate film comprising a support and at least an optical anisotropic layer including a liquid crystal fixed to a hybrid alignment state. One pixel of the liquid crystal cell comprises a red (R) pixel, a green (G) pixel, a blue (B) pixel and a white (W) pixel. The liquid crystal display device also includes drive means which applies a voltage Vand a voltage Vsatisfying the following conditions to between electrodes constituting the G pixel and to between electrodes constituting the W pixel, respectively, in accordance with a gradation L (where L satisfies 0≤L≤1) in a gradation mode where a substantially equal voltage Vis applied to between electrodes constituting each of the R pixel, the G pixel and the B pixel. The conditions are (i) T≤0.25×Twhen L is in a range of 0<L≤0.5 and (ii) T≤4×T-3 when L is in a range of 0.5<L≤1; where Tand Trepresent normalized transmittances obtained by normalizing the respective transmittances of the G pixel and the W pixel with respect to the luminance of white, which is set to 1, in the normal direction of the display screen of the liquid crystal display device.

Description

  The present invention relates to a liquid crystal display device and a driving method thereof.

  Conventionally, an RGBW liquid crystal display device has been proposed as a high-brightness liquid crystal display device (for example, Patent Document 1). The RGBW type liquid crystal display device performs color display with four colors of RGBW pixels, and by adding white (W) pixels, the normal direction of the display surface (hereinafter referred to as “normal” RGB type) is added. , Which is called “front direction”). If it is used in a TN liquid crystal display device that features high transmittance, it is expected that the features will be further enhanced.

  On the other hand, the TN liquid crystal display device has a problem that gradation inversion occurs. Conventionally, the actual situation is that gradation inversion is improved to some extent by compensating residual retardation during black display with an optical compensation film.

JP-A-5-241551

Here, it is known that the TN liquid crystal display device has an optical rotation mode and a birefringence mode. It is known that gradation inversion tends to occur in the downward direction in the optical rotation mode. On the other hand, in the birefringence mode, gradation reversal in the downward direction (hereinafter sometimes referred to as “bottom reversal”) is unlikely to occur, and white luminance in the front (hereinafter referred to as “front white luminance”) tends to be favorable. In the halftone between white display and black display, there is a problem that a phenomenon of horizontal whitening that becomes whitish when viewed from the horizontal direction occurs.
An object of the present invention is to solve such a problem, and it is difficult to cause gradation reversal in the downward direction, to maintain a high front white brightness, and to prevent halftone skipping. An object is to provide a TN liquid crystal display device in a refraction mode.

Under such circumstances, as a result of intensive studies by the present inventors, the voltage V _RGB applied between the electrodes constituting the R pixel, the G pixel, and the B pixel, and the voltage V applied between the voltages constituting the W pixel, respectively. It has been found that the above problem can be solved by setting _W so as to satisfy a specific condition. Specifically, the above problem has been solved by the following means <1>, preferably <2> to <5>.

<1> a pair of polarizers; at least one pair of substrates having electrodes constituting pixels on one opposing surface, and a liquid crystal layer disposed between the pair of substrates and twist-aligned at a twist angle of about 90 ° A liquid crystal cell; and an optical compensation film disposed between each of the pair of polarizers and the liquid crystal cell;
The pair of polarizers and the liquid crystal layer are arranged to be in a birefringence mode,
The optical compensation film is a laminated film having at least a support and an optically anisotropic layer containing liquid crystal fixed in a hybrid alignment state,
A liquid crystal display device in which one pixel of the liquid crystal cell includes a red (R) pixel, a green (G) pixel, a blue (B) pixel, and a white (W) pixel,
In a gradation in which a substantially equal voltage V _RGB is applied between the electrodes constituting each of the R pixel, the G pixel, and the B pixel, according to the gradation L (where L satisfies 0 ≦ L ≦ 1), A liquid crystal comprising drive means for applying a voltage V _RGB and a voltage V _W satisfying the following (i) and (ii) between electrodes constituting a G pixel and between electrodes constituting a W pixel, respectively: Display device:
(I) When 0 <L ≦ 0.5, T _G ≦ 0.25 × T _W
(Ii) When 0.5 <L ≦ 1, T _G ≦ 4 × T _W −3
However, _TG and _TW are normalized transmittances obtained by normalizing the transmittances of the G pixel and the W pixel, respectively, with the white luminance in the normal direction of the display surface of the liquid crystal display device being 1.
<2> The liquid crystal display device according to <1>, wherein one of an angle formed by the absorption axis of the polarizer and the rubbing direction of the substrate is 45 ° and the other is 135 °.
<3> The liquid crystal display device according to <1> or <2>, wherein the liquid crystal contained in the optically anisotropic layer is a discotic compound.
<4> The liquid crystal display device according to any one of <1> to <3>, wherein an angle formed between a slow axis of the support and an absorption axis of the polarizer is 45 ° or 135 °.
<5> a pair of polarizers; at least one pair of substrates having electrodes constituting pixels on one opposing surface, and a liquid crystal layer disposed between the pair of substrates and twist-aligned at a twist angle of about 90 ° A liquid crystal cell; and an optical compensation film disposed between each of the pair of polarizers and the liquid crystal cell;
The pair of polarizers and the liquid crystal layer are arranged to be in a birefringence mode,
The optical compensation film is a laminated film having at least a support and an optically anisotropic layer containing liquid crystal fixed in a hybrid alignment state,
A method of driving a liquid crystal display device in which one pixel of the liquid crystal cell is composed of a red (R) pixel, a green (G) pixel, a blue (B) pixel, and a white (W) pixel,
In a gradation in which a substantially equal voltage V _RGB is applied between the electrodes constituting each of the R pixel, the G pixel, and the B pixel, according to the gradation L (where L satisfies 0 ≦ L ≦ 1), A driving method for a liquid crystal display device, wherein a voltage V _RGB and a voltage V _W satisfying the following (i) and (ii) are respectively applied between electrodes constituting a G pixel and between electrodes constituting a W pixel: :
(I) When 0 <L ≦ 0.5, T _G ≦ 0.25 × T _W
(Ii) When 0.5 <L ≦ 1, T _G ≦ 4 × T _W −3
However, _TG and _TW are normalized transmittances obtained by normalizing the transmittances of the G pixel and the W pixel, respectively, with the white luminance in the normal direction of the display surface of the liquid crystal display device being 1.

 According to the present invention, it is possible to provide a birefringence mode TN type liquid crystal display device in which gradation reversal in the downward direction is unlikely to occur and the white brightness on the front surface is maintained high, and halftone whiteout is unlikely to occur.

Contributions of the gradation of the G pixel and the gradation of the W pixel of the RGBW type TN mode liquid crystal display device used in Comparative Example 1, Example 1, and Example 2 of the present application viewed from the horizontal direction (right direction) of 45 ° The relationship between the rate and the normalized transmittance is a three-dimensional map. It is a graph which shows the relationship of the gradation (Level) seen from 45 degrees of horizontal directions (right direction) and the normalized transmittance | permeability of the RGBW type | mold TN mode liquid crystal display device used for this application comparative example 1 and Example 1. FIG. Contributions of the gradation of the G pixel and the gradation of the W pixel of the RGBW type TN mode liquid crystal display device used in Comparative Example 2, Example 3, and Example 4 of the present application viewed from the horizontal direction (right direction) of 45 ° The relationship between the rate and the normalized transmittance is a three-dimensional map. It is a graph which shows the relationship of the gradation (Level) seen from 45 degrees of horizontal directions (right direction) and the normalized transmittance | permeability of the RGBW type | mold TN mode liquid crystal display device used for this application comparative example 2 and Example 3. FIG. In the RGBW type TN mode liquid crystal display device used in Comparative Example 1, Example 1 and Example 2 of the present application, the contribution ratios and the standards of the gradation of the G pixel and the gradation of the W pixel, as seen from the upper direction of 45 °, 3 is a three-dimensional map showing the relationship of the normalized transmittance. It is a graph which shows the relationship between the gradation (Level) seen from 45 degree | times upwards, and the normalized transmittance | permeability of the RGBW type | mold TN mode liquid crystal display device used for this application comparative example 1 and Example 1. FIG. In the RGBW type TN mode liquid crystal display device used in Comparative Example 2, Example 3, and Example 4 of the present application, the contribution ratios and standards of the gradation of the G pixel and the gradation of the W pixel, as seen from the upper direction of 45 °, 3 is a three-dimensional map showing the relationship of the normalized transmittance. It is a graph which shows the relationship of the gradation (Level) seen from 45 degrees of the upper direction, and the normalized transmittance | permeability of the RGBW type | mold TN mode liquid crystal display device used for this application comparative example 2 and Example 3. FIG. It is a cross-sectional schematic diagram which shows an example of the liquid crystal display device of a birefringence mode. It is the cross-sectional schematic which shows an example of the liquid crystal display device of the birefringence mode created in the Example. It is the cross-sectional schematic which shows an example of the liquid crystal display device of the birefringence mode created in the Example. It is the cross-sectional schematic which shows an example of the liquid crystal display device of the birefringence mode created in the Example. It is the cross-sectional schematic which shows an example of the liquid crystal display device of the birefringence mode created in the Example. It is an upper surface schematic diagram of an example of the RGBW color filter which can be used for this invention.

Hereinafter, the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value. In the present specification, numerical ranges and numerical values should be interpreted as numerical ranges and numerical values including errors allowed in the technical field to which the present invention belongs.
Further, in this specification, the polar angle is defined as the tilt angle from the normal direction of the display surface, and the right, upper, left, and lower directions of the display screen are azimuth angles of 0 degrees, 90 degrees, 180 degrees, and 270 degrees, respectively. When defined, “downward” means a direction with an azimuth angle of 270 degrees, and for example, “downward 45 °” means a direction with an azimuth angle of 270 degrees and a polar angle of 45 degrees.
About 90 ° means that the angle is within a strict angle of less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °.

The liquid crystal display device of the present invention is an RGBW type TN mode liquid crystal display device in which one pixel of a liquid crystal cell is composed of a red (R) pixel, a green (G) pixel, a blue (B) pixel, and a white (W) pixel. In a gradation in which a substantially equal voltage V _RGB is applied between the electrodes constituting each of the R pixel, the G pixel, and the B pixel, the gradation L (however, L satisfies 0 ≦ L ≦ 1). Accordingly, there is provided a drive voltage means for determining a voltage to be applied between the electrodes constituting each pixel and applying the voltage to each pixel. Note that the gradation is an achromatic state, that is, a state in which substantially the same voltage V _RGB is applied between the electrodes constituting the R pixel, the G pixel, and the B pixel. In the following, the driving means and driving method according to the present invention will be described in terms of the voltage applied between the electrodes constituting each of the G pixel and the W pixel. The relationship described below refers to the relationship between the G pixel, the R pixel, This relationship is established even if the pixel is replaced with the B pixel.

As described above, in the birefringence mode, there is usually no problem with downward gradation inversion and front white luminance, but halftone horizontal whiteout occurs. In the present invention, in a gradation in which a substantially equal voltage V _RGB is applied between the electrodes constituting each of the R pixel, G pixel, and B pixel, the gradation L (where L satisfies 0 ≦ L ≦ 1). In accordance with the above, by adopting driving means for applying the voltage V _RGB and the voltage V _W satisfying the following (i) and (ii) between the electrodes constituting the G pixel and between the electrodes constituting the W pixel, respectively. In this way, gradation inversion when viewed from below is suppressed, and halftone horizontal whiteout is effectively suppressed while maintaining high frontal white luminance. Furthermore, in the present invention, by adopting the above-mentioned driving means, it is possible to suppress halftone whiteout seen from above.
(I) When 0 <L ≦ 0.5, T _G ≦ 0.25 × T _W
(Ii) When 0.5 <L ≦ 1, T _G ≦ 4 × T _W −3
However, _TG and _TW are normalized transmittances obtained by normalizing the transmittances of the G pixel and the W pixel, respectively, with the white luminance in the normal direction of the display surface of the liquid crystal display device being 1.

In the present invention,
(I) When 0 <L ≦ 0.5, T _G ≦ 0.18 × T _W is preferable, and T _G ≦ 0.11 × T _W is more preferable.
(Ii) When 0.5 <L ≦ 1, T _G ≦ 5.67 × T _W −4.67 is preferable, and T _G ≦ 9 × T _W −8 is more preferable.

In the present invention, the relationship between the contribution ratio and the transmittance of the gradation of the G pixel and the gradation of the W pixel with respect to the gradation L is three-dimensionally mapped, and a gradation change path where gradation inversion starts is predicted in advance. In order to avoid the path, the voltages (T _G , T _W ) applied between the electrodes constituting the G pixel and the W pixel are determined according to the gradation L.

An example of the three-dimensional map is shown in FIGS. These are the relationship between the contribution rate of each of the gradation of the G pixel and the gradation of the W pixel and the transmittance at 45 degrees in the upward direction or 45 degrees in the lateral direction for the RGBW type TN mode liquid crystal display device of this embodiment or the comparative example. FIG. Note that the transmittance is shown as a normalized transmittance that is normalized by setting the transmittance of white luminance to 1.
The normalized transmittance is obtained for each of R, G, B, and W pixels. First, the normalized transmittance on the front will be described. The standardized transmittance on the front is a transmittance normalized by setting the white transmittance (usually near the maximum transmittance) to 1 from the relationship between the voltage and the transmittance on the front. The normalized transmittance is a value between 0 and 1, but when the normalized transmittance value is approximately 0 (usually, the vicinity of the minimum value is used), the gradation L0 (black), and the normalized transmittance value is When the value is 1, the gradation is L1 (white), and the middle of the gradation is intermediate gradation. The voltages to be applied corresponding to the gradations L0 to L1 are obtained from the front voltage-normalized transmittance relationship. For example, the voltages corresponding to the gradation L0 (black) correspond to V0 and L1 (white). Becomes V1 and becomes a voltage between V0 and V1 in the intermediate gradation.

Next, the normalized transmittance at 45 degrees upward will be described. The relationship between voltage and transmittance at 45 degrees in the upward direction when V0 to V1 obtained from the relationship between the front voltage and the normalized transmittance is applied is obtained, and this relationship is obtained when V1 (that is, white voltage) is obtained. The transmittance normalized by setting the transmittance at 45 degrees in the upward direction to 1 has a voltage-normalized transmittance relationship at 45 degrees in the upward direction. Using this relationship, a normalized transmittance at 45 degrees in the upper direction at each gradation is obtained. The same applies to the horizontal direction and the downward direction.
In this way, in each of the R, G, B, and W pixels, the normalized transmittance in the front and left / right / up / down directions at each gradation is obtained.
For example, FIG. 5 shows the respective contribution ratios of the gradation of the G pixel and the gradation of the W pixel at 45 degrees in the upward direction for the RGBW type TN mode liquid crystal display devices of Comparative Example 1, Example 1 and Example 2 of the present application. It is the figure which made the relationship with the transmittance | permeability 3D map. In the example shown in FIG. 5, in the change in transmittance along the straight line shown in Comparative Example 1, the transmittance increases until the gradation L changes from 0 to 0.07, but then decreases, that is, It can be understood that there is a valley → mountain → valley change. This causes gradation inversion.

On the other hand, in the example shown in FIG. 1, in the RGBW type TN mode liquid crystal display device of Comparative Example 1, Example 1 and Example 2, the contribution ratios of the gray scale of the G pixel and the gray scale of the W pixel are shown in the horizontal direction. (Right direction) It is the figure which made the three-dimensional map the relationship with the transmittance | permeability in 45 degree | times. Here, as indicated by the ideal line in FIG. 2, it is preferable that the gradation and the normalized transmittance coincide. This is because whiteout occurs in the halftone as it deviates from the ideal line. In the change in transmittance along the straight line shown in Comparative Example 1 of FIG. 1, it is in a state far from the ideal line as shown in FIG. 2. In such a state, halftone horizontal whiteout occurs. Resulting in. In the present invention, by adopting driving means for applying the voltage V _RGB and the voltage V _W satisfying (i) and (ii), respectively, between the electrodes constituting the G pixel and between the electrodes constituting the W pixel ( For example, Example 1 in FIG. 1 is a success in suppressing halftone horizontal whiteout while maintaining lower inversion and excellent front white luminance (Example 1 in FIG. 2).

Furthermore, the present invention employs driving means for applying the voltage V _RGB and the voltage V _W satisfying (i) and (ii), respectively, between the electrodes constituting the G pixel and between the electrodes constituting the W pixel. Therefore, it has also succeeded in suppressing the halftone tone seen from above. Details thereof will be described in an embodiment described later.

Next, the birefringence mode liquid crystal display device used in the present invention will be described.
FIG. 9 is a schematic cross-sectional view of an example of a birefringence mode liquid crystal display device of the present invention. The liquid crystal display device shown in FIG. 9 has a pair of polarizers 3 and 4 arranged so that their absorption axes 1 and 2 are orthogonal to each other, and a TN mode liquid crystal cell 5 arranged therebetween, and a pair of polarized light. Optical compensation films 6 and 7 are provided between each of the children 3 and 4 and the liquid crystal cell 5. The optical compensation films 6 and 7 have a support and an optically anisotropic layer made of a liquid crystal composition. Although omitted in the figure, a protective film made of a cellulose acylate film or the like is disposed on the outer surface of the polarizers 3 and 4. In the present embodiment, the protective film on the side close to the liquid crystal cell among the protective films for the polarizer is configured to serve as the optical compensation films 6 and 7. The optical compensation film is a laminated film having at least a support and an optically anisotropic layer containing liquid crystal fixed in a hybrid alignment state.

The liquid crystal cell is a TN mode liquid crystal cell that is twist-aligned with a twist angle of approximately 90 °. It has at least one pair of substrates 8 and 9 each having an electrode constituting a pixel on at least one opposing surface, and a liquid crystal layer disposed between the pair of substrates and twist-aligned at a twist angle of 90 °. A twist angle of 90 ° is preferable in terms of obtaining a high front contrast.
The liquid crystal display device of the present invention is a birefringence mode. As an example of the birefringence mode, the rubbing directions 10 and 11 of the liquid crystal cell substrates 8 and 9 and the absorption axes 1 and 2 of the polarizers 3 and 4 are 45. The form which is set to ° or 135 degrees is mentioned.

  One pixel of the liquid crystal cell 5 includes a red (R) pixel, a green (G) pixel, a blue (B) pixel, and a white (W) pixel. For example, in the liquid crystal cell 5, as shown in FIG. 14, an RGBW color filter is arranged on the opposite surface of one substrate to constitute an RGBW pixel. However, the configuration of the RGBW color filter is not limited to this example, and any conventionally proposed RGBW color filter can be used as long as the effects of the present invention are not impaired.

  In the liquid crystal cell 5, the nematic liquid crystal layer is twisted and white when no driving voltage is applied. When the driving voltage is applied, the twist alignment is canceled and the nematic liquid crystal is vertically aligned with respect to the substrate. Then it becomes black.

The optical compensation films 6 and 7 have a function of compensating for residual retardation when the liquid crystal cell 5 displays black. In the present invention, the optically anisotropic layer is an optically anisotropic layer containing a liquid crystal fixed in a hybrid alignment state.
The liquid crystal may be a rod-like liquid crystal or a disk-like liquid crystal, and a disk-like liquid crystal is preferred.
The optically anisotropic layer is measured from a direction inclined by 40 ° from the normal to the film surface direction in a plane (incident surface) including a normal perpendicular to the slow axis of the optical compensation film at a wavelength of 550 nm. The ratio of the retardation R [+ 40 °] and the retardation R [−40 °] measured from the direction inclined 40 ° from the normal line is 8 <R [−40 °] / R [+ 40 °] < 17 is preferably satisfied.
Moreover, it is preferable that the optical compensation film exhibits optical characteristics with Re (550) of 8 to 45 nm.
The support may or may not contribute to optical compensation. In the present invention, it is preferable that the support exhibits optical characteristics in which Re (550) is 0 to 45 nm and Rth (550) is 0 to 200 nm.

  When an optically anisotropic layer containing a liquid crystal fixed in a hybrid alignment state is used for optical compensation of a TN mode liquid crystal display device, the in-plane slow axis of the optically anisotropic layer is polarized in the vicinity. It is preferable to arrange it at 45 ° or 90 ° with respect to the transmission axis of the child. The in-plane slow axis of the optically anisotropic layer is preferably 45 ° or 90 ° with respect to the transmission axis of the adjacent polarizer.

  As the optical compensation film 15, “WV-EA film” manufactured by FUJIFILM Corporation or the like can be used. The “WV-EA film” is a laminated film composed of an optically anisotropic layer containing a discotic liquid crystal fixed in a hybrid alignment state and a support. Moreover, the optical compensation film produced by the well-known method may be sufficient.

Although omitted in the figure, the liquid crystal display device is driven by the control means, based on a signal from the outside, each of the RGB pixels by applying a substantially equal V _RGB, by applying a V _W to W pixels, gray The scale gradation L is controlled to be displayed. The drive control means includes a detection unit that detects information of gradation L from an external signal, a calculation unit that determines an applied voltage to each of the G pixel and the W pixel, and the determined voltage for each of the G pixel and the W pixel. And a drive unit to be applied.

  The liquid crystal display device of the birefringence mode of the present invention is not limited to the embodiment shown in FIG. 9, but supports the absorption axes 1 and 2 of the polarizer 3.4 and the optical compensation films 6 and 7 as in the embodiment shown in FIG. The slow axis of the body may be parallel, and as in the embodiment of FIG. 11, the absorption axes 1 and 2 of the polarizer 3.4 and the slow axis of the support of the optical compensation films 6 and 7 are 45. It may be at an angle of ° or 135 °. Further, as shown in FIGS. 12 and 13, an optical anisotropic layer (DLC) containing a disc-like liquid crystal fixed in a hybrid alignment state and / or an optical anisotropic containing a rod-like liquid crystal fixed in a hybrid alignment state The aspect which has an optical compensation film which laminates | stacks a property layer (RLC) and has an at least 2 optically anisotropic layer may be sufficient. In this case, the direction of the slow axis of the two optical anisotropic layers is preferably the same.

In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. In the present specification, the wavelength λ is 590 nm unless otherwise specified. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotary axis) (if there is no slow axis, any in-plane film The light is incident at a wavelength of λ nm from the inclined direction in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction of the rotation axis of KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (1) and (2).

式（２）
Ｒｔｈ＝｛（ｎｘ＋ｎｙ)／２ − ｎｚ｝ × ｄ
上記式中、Ｒｅ(θ)は法線方向から角度θ傾斜した方向におけるレターデーション値をあらわし、ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘおよびｎｙに直交する方向の屈折率を表す。ｄは膜厚である。

Formula (2)
Rth = {(nx + ny) / 2−nz} × d
In the above formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction, nx represents a refractive index in the slow axis direction in the plane, and ny is a direction orthogonal to nx in the plane. Nz represents the refractive index in the direction orthogonal to nx and ny. d is the film thickness.

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction. The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or WR is calculated.
In the above measurement, the assumed value of the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of the main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.
In the present specification, the refractive index measurement wavelength is 550 nm unless otherwise specified.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to a following example.

<Production of liquid crystal display device 1>
1. Preparation of optical compensation film (1) Optical compensation film 1
As described below, after producing a transparent support film, an alignment film and an optically anisotropic layer were formed thereon to produce an optical compensation film, which was used as the optical compensation film 1.

(Preparation of transparent support)
(1) Preparation of intermediate layer dope 1 An intermediate layer dope 1 having the following composition was prepared.
――――――――――――――――――――――――――――――――――――
Composition of Dope 1 ――――――――――――――――――――――――――――――――――――
Cellulose acetate (degree of acetylation 2.86) 100 parts by mass Methylene chloride (first solvent) 320 parts by mass Methanol (second solvent) 83 parts by mass 1-butanol (third solvent) 3 parts by mass Triphenyl Phosphate 7.6 parts by mass, biphenyldiphenyl phosphate 3.8 parts by mass ────────────────────────────────── ───

Specifically, it was prepared by the following method.
While stirring and dispersing the above mixed solvent well into a 4000 L stainless steel dissolution tank with stirring blades, cellulose acetate powder (flake), triphenyl phosphate and biphenyl diphenyl phosphate are gradually added to a total of 2000 kg. It was prepared as follows. In addition, all the solvents used that the water content is 0.5 mass% or less. First, cellulose acetate powder is a dissolver type in which powder is put into a dispersion tank and stirred at a peripheral shear speed of 5 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² ) at first. The dispersion was carried out for 30 minutes under the condition of having an eccentric stirring shaft and an anchor blade on the central shaft and stirring at a peripheral speed of 1 m / sec (shear stress of 1 × 10 ⁴ kgf / m / sec ² ). The starting temperature of dispersion was 25 ° C., and the final temperature reached 48 ° C. After completion of the dispersion, the high-speed stirring was stopped, and the peripheral speed of the anchor blade was set to 0.5 m / sec and further stirred for 100 minutes to swell the cellulose acetate flakes. Until the end of swelling, the inside of the tank was pressurized to 0.12 MPa with nitrogen gas. At this time, the oxygen concentration in the tank was less than 2 vol%, and the state of no problem was maintained in terms of explosion protection. The water content in the dope was confirmed to be 0.5% by mass or less, specifically 0.3% by mass.

The swollen solution was heated from the tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. by pressurization at 2 MPa to completely dissolve. The heating time was 15 minutes.
Next, the temperature was lowered to 36 ° C., and a dope was obtained by passing through a filter medium having a nominal pore diameter of 8 μm. At this time, the primary pressure of filtration was 1.5 MPa, and the secondary pressure was 1.2 MPa. The filters, housings, and pipes exposed to high temperatures were made of Hastelloy alloy and had excellent corrosion resistance, and those having a jacket for circulating a heat medium for heat insulation and heating were used.

The pre-concentration dope thus obtained was flushed at 80 ° C. in a normal pressure tank, and the evaporated solvent was recovered and separated by a condenser. The solid concentration of the dope after flashing was 21.8% by mass. The condensed solvent was sent to a recovery process to be reused as a solvent in the preparation process (recovery is carried out by a distillation process, a dehydration process, etc.). A flash tank having an anchor blade on the central axis was used for defoaming by stirring at a peripheral speed of 0.5 m / sec. The temperature of the dope in the tank was 25 ° C., and the average residence time in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 450 (Pa · s) at a shear rate of 10 (sec ⁻¹ ).

  Next, bubbles were removed by irradiating the dope with weak ultrasonic waves. Thereafter, under a pressure of 1.5 MPa, first, a sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then, a 10 μm sintered fiber filter was also passed. Respective primary pressures were 1.5 and 1.2 MPa, and secondary pressures were 1.0 and 0.8 MPa. The dope temperature after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank. By using a stock tank having an anchor blade on the central axis and stirring constantly at a peripheral speed of 0.3 m / sec, an intermediate layer dope 1 was obtained. In addition, when the dope was prepared from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

  Subsequently, the dope 1 in the stock tank was fed by a feedback pump control using an inverter motor so that the primary pressure of the high precision gear pump was 0.8 MPa with a gear pump for primary pressure increase. The high-precision gear pump had a volume efficiency of 99.2% and a discharge rate variation of 0.5% or less. The discharge pressure was 1.5 MPa.

(2) Preparation of dope 2 for support layer Matting agent (silicon dioxide (particle size 20 nm)) and release accelerator (citric acid ethyl ester (citric acid, monoethyl ester, diethyl ester, triethyl ester mixture)) and the intermediate The layer dope 1 was mixed through a static mixer to prepare a support layer dope 2. The addition amount was such that the total solid content concentration was 20.5% by mass, the matting agent concentration was 0.05% by mass, and the release accelerator concentration was 0.03% by mass.

(3) Preparation of Air Layer Dope 3 A matting agent (silicon dioxide (particle size: 20 nm)) was mixed with the intermediate layer dope 1 through a static mixer to prepare an air layer dope 3. The amount added was such that the total solid content concentration was 20.5% by mass and the matting agent concentration was 0.1% by mass.

(4) Film formation by co-casting Equipped with a feed block adjusted for co-casting as a casting die, an apparatus that can form a three-layer film by laminating on both sides in addition to the main stream Was used. In the following description, a layer formed from the mainstream is referred to as an intermediate layer, a layer on the support surface side is referred to as a support layer, and a surface on the opposite side is referred to as an air layer. In addition, the dope liquid supply flow path used three flow paths for the intermediate layer, the support layer, and the air layer.

  The intermediate layer dope, support layer dope 2 and air layer dope 3 were co-cast from a casting port onto a drum cooled to -5 ° C. At this time, the flow rate of each dope was adjusted so that the thickness ratio was air layer / intermediate layer / support layer = 4/73/3. The cast dope film was dried on a drum, and peeled off from the drum with a residual solvent of 150%. During peeling, 17% stretching was performed in the transport direction (longitudinal direction). Thereafter, the film was conveyed and dried while holding both ends of the film in the width direction (direction perpendicular to the casting direction) with a pin tenter (a pin tenter described in FIG. 3 of JP-A-4-1009). Furthermore, it dried further by conveying between the rolls of a heat processing apparatus, and manufactured the 80-micrometer-thick film. The produced cellulose acetate film had an in-plane retardation Re at a wavelength of 550 nm of 4 nm and a thickness direction retardation Rth of 42 nm.

(Preparation of alignment film)
On this cellulose acetate film, a coating solution having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds. A rubbing treatment was performed on the surface of the formed film by rotating it at 500 rotations / minute in a + 45 ° direction (counterclockwise) with respect to the conveying direction with a rubbing roll to produce an alignment film. Similarly, the surface of the formed film was rubbed with a rubbing roll in the direction of −45 ° (clockwise) with respect to the transport direction at 500 rpm to produce an alignment film.
────────────────────────────────────
(Orientation film coating solution composition)
────────────────────────────────────
Modified polyvinyl alcohol 10 parts by weight Water 370 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight ─────────────────────── ─────────────

(Preparation of optically anisotropic layer)
The following coating solution was continuously applied to the alignment film surface of the film using a # 3.6 wire bar. In the step of continuously heating from room temperature to 100 ° C., the solvent was dried, and then heated in a drying zone at 135 ° C. for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 80 ° C., and the surface temperature of the film is about 100 ° C., and irradiated with ultraviolet rays with an illuminance of 600 mW for 10 seconds by an ultraviolet irradiation device to advance the crosslinking reaction. Was polymerized. Then, it stood to cool to room temperature, the optically anisotropic layer was formed, and the optical compensation film 1 was produced.
―――――――――――――――――――――――――――――――――――――
(Optical anisotropic layer coating composition)
―――――――――――――――――――――――――――――――――――――
Methyl ethyl ketone 333.39 parts by mass The following discotic liquid crystalline compound (1) 91.00 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.00 parts by mass The following air Interfacial orientation control agent (1) 0.56 parts by mass The following air interface orientation control agent (2) 0.19 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 3.00 parts by mass Sensitizer (Kayacure) DETX, manufactured by Nippon Kayaku Co., Ltd.) 1.00 parts by mass ――――――――――――――――――――――――――――――――――――― -

空気界面配向制御剤（１）

空気界面配向制御剤（２）

Discotic liquid crystal compound (1)

Air interface orientation control agent (1)

Air interface orientation control agent (2)

(Measurement of optical properties)
An alignment film and an optically anisotropic layer are similarly produced on a glass plate instead of the transparent support, and the surface of the optically anisotropic layer having a wavelength of 550 nm is used using KOBRA-WR (manufactured by Oji Scientific Instruments). The inner retardation Re (550) was measured. In addition, in the plane perpendicular to the slow axis of the optically anisotropic layer, light having a wavelength of 550 nm is incident from a direction inclined by ± 40 degrees from the normal direction, and retardations R [+ 40 °] and R [−40 °] was measured, and R [−40 °] / R [+ 40 °] was calculated.

(Production of polarizer)
The polarizer used was a 20 μm-thick linear polarizing film prepared by continuously stretching an 80 μm-thick polyvinyl alcohol film in an aqueous iodine solution and drying it, and the adhesive was polyvinyl alcohol ( A Kuraray PVA-117H) 3% aqueous solution was used.

(Production of TN mode liquid crystal display device)
The optical compensation film 1 is arranged so that the relationship between the slow axis of the produced transparent support, the optically anisotropic layer, and the absorption axis of the polarizer is as shown in FIG. 10, and a TN mode liquid crystal display having a birefringence mode configuration is provided. Device 1 was made.
As the liquid crystal cell, a TN mode liquid crystal cell having an RGBW color filter having the configuration shown in FIG. 14 was prepared and used. The birefringence Δnd of the liquid crystal was adjusted to 410 nm by adjusting the cell gap.

<Evaluation>
For Examples and Comparative Examples, in each of the gradation L, respectively T _G and T _W of G pixels and W pixels by applying a voltage so as to satisfy the values in the following Table, driving each liquid crystal display device did. The gradation (Level) indicates a value of (T _G + T _W ) / 2.
For example, in Example 1 and Example 2, a voltage was applied so as to satisfy the following.
When 0 <L ≦ 0.5, T _G = 0.25 × T _W
When 0.5 <L ≦ 1, T _G = 4 × T _W −3
On the other hand, in Comparative Example 1, a voltage was applied to each of the G pixel and the W pixel so as to satisfy T _G = T _W.
Halftone horizontal whiteout, gradation inversion in the downward direction, and front white luminance were evaluated.

In each of the liquid crystal display devices produced above, ISO 12640-1: 1997, standard number JIX 9201: 1995, image name portrait is displayed, and visually observed from a downward direction (polar angle 30 °) in a dark room, The gradation inversion of the display image was evaluated.
A: Gradation inversion in the downward direction is hardly observed, and there is no practical problem.
B: The gradation inversion in the downward direction is small, and there is no practical problem.
C: Since the gradation inversion in the downward direction is poor, there is a problem in practical use.

(Intermediate white jump)
Each of the liquid crystal display devices manufactured as described above displays ISO 12640-1: 1997, standard number JIX 9201: 1995, image name portrait, and is visually observed from the lower direction (polar angle 45 °) in a dark room. The overexposure of the image was evaluated.
A: In the upward direction, there is almost no impression that the halftone is floating in white, and there is no practical problem.
B: In the upward direction, it is small that the halftone is white and flying away, and there is no practical problem.
C: The halftone in the upward direction is white and floats, which is problematic in practice.

(Front white brightness)
About each liquid crystal display device produced above, the brightness | luminance of a front direction (normal direction with respect to a display surface) is measured by a white display using the measuring instrument "EZ-Contrast XL88" (made by ELDIM). Then, the luminance was measured only for the backlight in which the liquid crystal panel was removed from the liquid crystal display device (the result was Y0), and the ratio (I = Y / Y0) was obtained. Then, in order to relatively compare the front luminance of each comparative example and example, a relative value when I of Comparative Example 1 was set to 100 was obtained by calculation, and this was defined as front white luminance.

＊表中、透明支持体／光学異方性層の積層順とは、以下の内容を示す。
Ａ：液晶セル側から光学異方性層、透明支持体の順で積層したことを意味している。

* In the table, the order of lamination of the transparent support / optically anisotropic layer indicates the following contents.
A: It means that the optically anisotropic layer and the transparent support were laminated in this order from the liquid crystal cell side.

<Production of liquid crystal display device 2>
(Preparation of optical compensation film 2)
As described below, after producing a transparent support film, an alignment film and an optically anisotropic layer were formed thereon to produce an optical compensation film, which was used as the optical compensation film 2.

(Preparation of transparent support)
Cellulose acylate was synthesized by the method described in JP-A-10-45804 and 08-231761, and the degree of substitution was measured. Specifically, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl substituent was added, and an acylation reaction was performed at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.

(Preparation of cellulose acylate solution C01)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate solution. The amount of the solvent (methylene chloride and methanol) was appropriately adjusted so that the solid content concentration of each cellulose acylate solution was 22% by mass. However, for CO5, the amount of the solvent was appropriately adjusted so that the solid content concentration was 19% by mass.
―――――――――――――――――――――――――――――――――――――
Cellulose acetate (substitution degree 2.45) 100.0 parts by mass Additives in the following table Compound A 19.0 parts by mass Methylene chloride 365.5 parts by mass Methanol 54.6 parts by mass ――――――――――――――――――――――――――――――

(Preparation of cellulose acylate solution C02)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate solution. The amount of the solvent (methylene chloride and methanol) was appropriately adjusted so that the solid content concentration of each cellulose acylate solution was 22% by mass. However, for CO5, the amount of the solvent was appropriately adjusted so that the solid content concentration was 19% by mass.
―――――――――――――――――――――――――――――――――――――
Cellulose acetate (degree of substitution 2.81) 100.0 parts by mass Additives in the following table Compound A 12.0 parts by mass Methylene chloride 365.5 parts by mass Methanol 54.6 parts by mass ――――――――――――――――――――――――――――――
Compound A represents a terephthalic acid / succinic acid / ethylene glycol / propylene glycol copolymer (copolymerization ratio [mol%] = 27.5 / 22.5 / 25/25).
Compound A is a non-phosphate ester compound and also a retardation developer. The end of compound A is sealed with an acetyl group.

The cellulose acylate solution C01 was cast using a band stretching machine so that the cellulose acylate solution C02 became a skin layer A having a thickness of 2 μm so that the core layer had a thickness of 56 μm. Subsequently, the obtained web (film) was peeled from the band, sandwiched between clips, and transversely stretched using a tenter. The stretching temperature was set to 172 ° C. and the stretching ratio was set to 30%. Thereafter, the clip was removed from the film and dried at 130 ° C. for 20 minutes to obtain a film.
The in-plane retardation Re at a wavelength of 550 nm of the produced transparent support was −50 nm (the direction of the slow axis of the optically anisotropic layer was positive, the same applies hereinafter), and the retardation Rth in the thickness direction was 120 nm. . The film thickness was 60 μm.

(Preparation of alignment film)
On this transparent support, coating solution H-1 having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds. The formed film surface was rubbed with a rubbing roll in a direction parallel to the conveying direction at 500 rpm to produce an alignment film.
────────────────────────────────────
(Alignment film coating solution composition H-1)
────────────────────────────────────
Modified polyvinyl alcohol 10 parts by weight Water 370 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight ─────────────────────── ─────────────

(Preparation of optically anisotropic layer)
The following coating solution was continuously applied to the alignment film surface of the film using a # 3.0 wire bar. In the step of continuously heating from room temperature to 100 ° C., the solvent was dried, and then heated in a drying zone at 135 ° C. for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 80 ° C., and the surface temperature of the film is about 100 ° C., and irradiated with ultraviolet rays with an illuminance of 600 mW for 10 seconds by an ultraviolet irradiation device to advance the crosslinking reaction. Was polymerized. Then, it stood to cool to room temperature, the optically anisotropic layer was formed, and the optical compensation film was produced.
―――――――――――――――――――――――――――――――――――――
(Optical anisotropic layer coating composition)
―――――――――――――――――――――――――――――――――――――
Methyl ethyl ketone 333.39 parts by mass The above discotic liquid crystalline compound (1) 91.00 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.00 parts by mass The following air Interfacial orientation control agent 0.75 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 3.00 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1.00 parts by mass ――――――――――――――――――――――――――――――――――

Air interface orientation control agent:

(Production of TN mode liquid crystal display device)
The liquid crystal display device 2 was produced by arranging the produced transparent support, the slow axis of the optically anisotropic layer, and the absorption axis of the polarizer so that the relationship shown in FIG.
As the liquid crystal cell, a TN mode liquid crystal cell having an RGBW color filter having the configuration shown in FIG. 14 was prepared and used. The birefringence Δnd of the liquid crystal was adjusted to 410 nm by adjusting the cell gap.

＊表中、透明支持体／光学異方性層の積層順とは、以下の内容を示す。
Ａ：液晶セル側から光学異方性層、透明支持体の順で積層 Examples 3 and 4 and Comparative Example 2 were evaluated in the same manner as in Examples 1 and 2.

* In the table, the order of lamination of the transparent support / optically anisotropic layer indicates the following contents.
A: Laminated in order of optically anisotropic layer and transparent support from the liquid crystal cell side

<Production of liquid crystal display device 3>
(Preparation of optical compensation film 3)
As described below, after producing a transparent support film, an alignment film and an optically anisotropic layer were formed thereon to produce an optical compensation film, which was used as the optical compensation film 3.

(Preparation of transparent support)
The following composition was put into a mixing tank and stirred while heating to 30 ° C. to dissolve each component to prepare a cellulose acetate solution C-1.
──────────────────────────────────────
Cellulose acetate solution composition (C-1) (parts by mass) Inner layer Outer layer ─────────────────────────────────── ───
Cellulose acetate with an acetylation degree of 60.9% 100 100
Triphenyl phosphate (plasticizer) 7.8 7.8
Biphenyl diphenyl phosphate (plasticizer) 3.9 3.9
Methylene chloride (first solvent) 293 314
Methanol (second solvent) 71 76
1-butanol (third solvent) 1.5 1.6
Silica fine particles (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.)
0 0.8
Retardation raising agent 1.7 0
─────────────────────────────────────

  The inner layer dope and the outer layer dope of S-1 thus obtained were cast on a drum cooled to 0 ° C. by adjusting the flow rate of the inner layer dope using a three-layer co-casting die. The film having a residual solvent amount of 70% by mass was peeled off from the drum, both ends were fixed with a pin tenter, and the film was dried at 80 ° C. while being transported at a draw ratio of 110% in the transport direction. By the way, it was dried at 110 ° C. Thereafter, it is dried at a temperature of 140 ° C. for 30 minutes to produce transparent supports 1 and 2 of a cellulose acetate film (thickness 40 μm (outer layer: 3 μm, inner layer: 34 μm, outer layer: 3 μm)) having a residual solvent of 0.3% by mass. did. The produced cellulose acetate film had an in-plane retardation Re at a wavelength of 550 nm of 7 nm and a thickness direction retardation Rth of 45 nm.

  The produced cellulose acetate was immersed in a 2.0N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid, washed with pure water and dried.

(Preparation of alignment film)
On this transparent support, coating solution H-1 having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds. The formed film surface was rubbed with a rubbing roll in a direction parallel to the conveying direction at 500 rpm to produce an alignment film.
────────────────────────────────────
(Orientation film coating solution composition)
────────────────────────────────────
Modified polyvinyl alcohol 10 parts by weight Water 370 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight ─────────────────────── ─────────────

(Preparation of optically anisotropic layer RLC)
A coating liquid containing a rod-like liquid crystal compound having the following composition was continuously applied onto the alignment film with a # 2.2 wire bar. In order to dry the solvent after coating and to mature the alignment of the rod-like liquid crystal compound, it was heated with hot air at 90 ° C. for 60 seconds.

Composition of coating solution for optically anisotropic layer RLC ――――――――――――――――――――――――――――――――――――――
The following rod-like liquid crystal compound 100 parts by mass The following photopolymerization initiator 3 parts by mass sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by mass The following fluoropolymer (D) 0.4 parts by mass The following Horizontal alignment agent 0.2 parts by mass Methyl ethyl ketone 195 parts by mass ―――――――――――――――――――――――――――――――――――――

光重合開始剤

フッ素系ポリマー（Ｄ）

水平配向剤

Rod-shaped liquid crystal compound

Photopolymerization initiator

Fluoropolymer (D)

Horizontal alignment agent

(Preparation of alignment film)
On this optically anisotropic layer RLC, a coating solution H-1 having the following composition was applied at 28 mL / m ² with a # 16 wire bar coater. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 90 ° C. for 150 seconds. The formed film surface was rubbed with a rubbing roll in a direction parallel to the conveying direction at 500 rpm to produce an alignment film.
────────────────────────────────────
(Orientation film coating solution composition)
────────────────────────────────────
Modified polyvinyl alcohol 10 parts by weight Water 370 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 0.5 parts by weight ─────────────────────── ─────────────

(Preparation of optically anisotropic layer DLC)
The following coating solution was continuously applied to the alignment film surface of the film using a # 3.0 wire bar. In the step of continuously heating from room temperature to 100 ° C., the solvent was dried, and then heated in a drying zone at 135 ° C. for about 90 seconds to align the discotic liquid crystal compound. Next, the film is transported to a drying zone at 80 ° C., and the surface temperature of the film is about 100 ° C., and irradiated with ultraviolet rays with an illuminance of 600 mW for 10 seconds by an ultraviolet irradiation device to advance the crosslinking reaction. Was polymerized. Then, it stood to cool to room temperature, the optically anisotropic layer was formed, and the optical compensation film was produced.
The normalized transmittance of the optical compensation film 3 thus produced was almost the same as the normalized transmittance of the optical compensation film 2.
―――――――――――――――――――――――――――――――――――――
(Optical anisotropic layer coating composition)
―――――――――――――――――――――――――――――――――――――
Methyl ethyl ketone 333.39 parts by mass The above discotic liquid crystalline compound (1) 91.00 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.00 parts by mass The following air Interfacial orientation control agent 0.75 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 3.00 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1.00 parts by mass ――――――――――――――――――――――――――――――――――

Air interface alignment control agent

(Production of TN mode liquid crystal display device)
The liquid crystal display device 3 was produced by arranging the produced transparent support, the slow axis of the optically anisotropic layer, and the absorption axis of the polarizer so that the relationship shown in FIG.
As the liquid crystal cell, a TN mode liquid crystal cell having an RGBW color filter having the configuration shown in FIG. 14 was prepared and used. The birefringence Δnd of the liquid crystal was adjusted to 410 nm by adjusting the cell gap.

  Evaluations of Examples 5 and 6 and Comparative Example 3 were performed in the same manner as in Examples 1 and 2.

＊表中、透明支持体／光学異方性層ＲＬＣ／光学異方性層ＤＬＣの積層順とは、以下の内容を示す。
Ａ２：液晶セル側から光学異方性層ＤＬＣ、光学異方性層ＲＬＣ、透明支持体の順で積層
積層

* In the table, the order of lamination of the transparent support / optically anisotropic layer RLC / optically anisotropic layer DLC indicates the following.
A2: Laminated and laminated in order of optically anisotropic layer DLC, optically anisotropic layer RLC, and transparent support from the liquid crystal cell side

<Production of liquid crystal display device 4>
(Preparation of optical compensation film 4)
(Alkaline saponification treatment of transparent support)
The transparent support used in Example 5 was passed through a dielectric heating roll having a temperature of 60 ° C., and the film surface temperature was raised to 40 ° C. Then, an alkali solution having the composition shown below was applied to one side of the film with a bar coater. Was applied at a coating amount of 14 ml / m ² and transported for 10 seconds under a steam far-infrared heater manufactured by Noritake Company Limited, heated to 110 ° C. Subsequently, 3 ml / m ^{2 of} pure water was applied using the same bar coater. Next, washing with a fountain coater and draining with an air knife were repeated three times, and then transported to a drying zone at 70 ° C. for 10 seconds and dried to prepare an alkali saponified transparent support.

(Alkaline solution composition)
───────────────────────────────────
Alkaline solution composition ───────────────────────────────────
Potassium hydroxide 4.7 parts by weight Water 15.8 parts by weight Isopropanol 63.7 parts by weight Surfactant SF-1: C ₁₄ H ₂₉ O (CH ₂ CH ₂ O) ₂₀ H 1.0 part by weight Propylene glycol 14. 8 parts by mass ───────────────────────────────────

(Formation of alignment film)
An alignment film coating solution having the following composition was continuously applied to the transparent support subjected to the saponification treatment as described above with a # 14 wire bar. Drying was performed with warm air of 60 ° C. for 60 seconds and further with warm air of 100 ° C. for 120 seconds.
Composition of alignment film coating solution ―――――――――――――――――――――――――――――――――――
Denatured polyvinyl alcohol 10 parts by weight Water 371 parts by weight Methanol 119 parts by weight Glutaraldehyde 0.5 parts by weight Photopolymerization initiator (Irgacure 2959, manufactured by Ciba Japan) 0.3 parts by weight ―――――――――――――――――――――――――――

Modified polyvinyl alcohol (unit of content ratio of each unit is mol%)

(Formation of optically anisotropic layer A)
The alignment film thus prepared was continuously rubbed. At this time, the longitudinal direction of the transparent support was parallel to the transport direction, and the rotation axis of the rubbing roller was 45 ° and −45 ° clockwise with respect to the longitudinal direction of the transparent support.

A coating liquid (A) containing a discotic liquid crystal compound having the following composition was continuously applied onto the prepared alignment film with a # 1.6 wire bar. The conveyance speed (V) of the film was 36 m / min. In order to dry the solvent of the coating solution and to mature the orientation of the discotic liquid crystal compound, it was heated with hot air at 80 ° C. for 90 seconds. Subsequently, UV irradiation was performed at 80 ° C. to fix the orientation of the liquid crystal compound and form an optically anisotropic layer.
The optically anisotropic layer A represents the optically anisotropic layer on the transparent support side in FIG. 13, and the optically anisotropic layer B is laminated in contact with the optically anisotropic layer A. Represents a layer.

Composition of coating solution (A) for optically anisotropic layer ―――――――――――――――――――――――――――――――――――
The following discotic liquid crystal compound 100 parts by mass photopolymerization initiator (Irgacure 907, manufactured by Ciba Japan) 3 parts by mass sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by mass The following pyridinium salt 1 Part by mass The following fluoropolymer (FP1) 0.4 part by mass Methyl ethyl ketone 473 parts by mass ――――――――――――――――――――――――――――――― ――――

(Formation of alignment film)
An alignment film was formed on the produced optically anisotropic layer A in the same manner as in Example 3.

(Preparation of optically anisotropic layer B)
An optically anisotropic layer was produced in the same manner as in Example 3.
The normalized transmittance of the optical compensation film 4 thus produced was almost the same as the normalized transmittance of the optical compensation film 2.

(Production of TN mode liquid crystal display device)
The liquid crystal display device 4 was produced by arranging the produced transparent support, the slow axis of the optically anisotropic layer, and the absorption axis of the polarizer so as to have the relationship shown in FIG.
As the liquid crystal cell, a TN mode liquid crystal cell having an RGBW color filter having the configuration shown in FIG. 14 was prepared and used. The birefringence Δnd of the liquid crystal was adjusted to 410 nm by adjusting the cell gap.

  Evaluations of Examples 7 to 8 and Comparative Example 4 were performed in the same manner as in Examples 1 and 2.

＊表中、透明支持体／光学異方性層Ａ／光学異方性層Ｂの積層順とは、以下の内容を示す。
Ａ２：液晶セル側から光学異方性層Ａ、光学異方性層Ｂ、透明支持体の順で積層

* In the table, the order of lamination of the transparent support / the optically anisotropic layer A / the optically anisotropic layer B indicates the following contents.
A2: Laminated in order of optically anisotropic layer A, optically anisotropic layer B, and transparent support from the liquid crystal cell side

<Production of liquid crystal display device 5>
A liquid crystal display device was produced in the same manner as in Example 7 except that the birefringence Δnd of the liquid crystal of the liquid crystal display device in Example 7 was changed to 450 nm, and evaluated in the same manner as in Examples 1 and 2.

  As is clear from the above table, it was found that all of the liquid crystal display devices of the examples were suppressed from bottom inversion, had high front white luminance, and did not easily cause over-exposure in halftones. on the other hand. In the comparative example, the bottom inversion is suppressed and the front white luminance is excellent, but the whiteout in the halftone has occurred.

  FIG. 1 shows a distribution of normalized transmittance that contributes to G and W pixels when viewed from a horizontal direction of 45 ° in a liquid crystal display device using the optical compensation film 1, and FIG. FIG. 5 shows a distribution of normalized transmittance from 45 ° in the horizontal direction when the film 2 is used. FIG. 5 shows a distribution of normalized transmittance from 45 ° in the downward direction when the optical compensation film 1 is used. FIG. 7 shows the normalized transmittance distribution from the horizontal direction of 45 ° when the optical compensation film 2 is used.

FIG. 2 shows the normalized transmittance with respect to each gradation (Level) in the liquid crystal display device having the normalized transmittance distribution shown in FIG. Show. The dotted line is the ideal line. Compared to Comparative Example 1, Example 1 is closer to the ideal line, and it can be seen that halftone skipping in the horizontal direction is suppressed.
Similarly, FIG. 4 shows a normalized transmission for each gradation (Level) in the liquid crystal display device having the normalized transmittance distribution shown in FIG. 3 when viewed from the horizontal direction in Example 3 and Comparative Example 2. Shows the rate. The dotted line is the ideal line. Compared to Comparative Example 2, Example 3 is closer to the ideal line, and it can be seen that the halftone skip in the horizontal direction is suppressed.

FIG. 6 shows the normalized transmittance with respect to each gradation (Level) when viewed from above in Example 1 and Comparative Example 1 in the liquid crystal display device having the normalized transmittance distribution shown in FIG. Show. The dotted line is the ideal line. Compared to Comparative Example 1, Example 1 is closer to the ideal line, and it can be seen that the halftone jumping in the upward direction is suppressed.
FIG. 8 shows the normalized transmittance with respect to each level when the liquid crystal display device having the normalized transmittance distribution shown in FIG. 7 is viewed from above in Example 1 and Comparative Example 1. . The dotted line is the ideal line. Compared with Comparative Example 2, Example 3 is close to the ideal line, and it can be seen that halftone jumping in the upward direction is suppressed.

  According to the present invention, it is possible to provide a liquid crystal display device in a birefringence mode in which downward gradation inversion is suppressed, front white luminance is high, and halftone whiteout is hardly generated.

DESCRIPTION OF SYMBOLS 1 Absorption axis 2 Absorption axis 3 Polarizer 4 Polarizer 5 Liquid crystal cell 6 Optical compensation film 7 Optical compensation film 8 Liquid crystal cell substrate 9 Liquid crystal cell substrate 10 Rubbing direction 11 Rubbing direction

Claims (5)

A pair of polarizers; a liquid crystal cell having at least one pair of substrates having electrodes constituting pixels on at least one opposing surface, and a liquid crystal layer disposed between the pair of substrates and twist-aligned at a twist angle of approximately 90 ° And an optical compensation film disposed between each of the pair of polarizers and the liquid crystal cell;
The pair of polarizers and the liquid crystal layer are arranged to be in a birefringence mode,
The optical compensation film is a laminated film having at least a support and an optically anisotropic layer containing liquid crystal fixed in a hybrid alignment state,
A liquid crystal display device in which one pixel of the liquid crystal cell includes a red (R) pixel, a green (G) pixel, a blue (B) pixel, and a white (W) pixel,
In a gradation in which a substantially equal voltage V _RGB is applied between the electrodes constituting each of the R pixel, the G pixel, and the B pixel, according to the gradation L (where L satisfies 0 ≦ L ≦ 1), A liquid crystal comprising drive means for applying a voltage V _RGB and a voltage V _W satisfying the following (i) and (ii) between electrodes constituting a G pixel and between electrodes constituting a W pixel, respectively: Display device:
(I) When 0 <L ≦ 0.5, T _G ≦ 0.25 × T _W
(Ii) When 0.5 <L ≦ 1, T _G ≦ 4 × T _W −3
However, _TG and _TW are normalized transmittances obtained by normalizing the transmittances of the G pixel and the W pixel, respectively, with the white luminance in the normal direction of the display surface of the liquid crystal display device being 1. 2. The liquid crystal display device according to claim 1, wherein one of an angle formed by an absorption axis of the polarizer and a rubbing direction of the substrate is 45 ° and the other is 135 °. The liquid crystal display device according to claim 1, wherein the liquid crystal contained in the optically anisotropic layer is a discotic compound. The liquid crystal display device according to claim 1, wherein an angle formed by a slow axis of the support and an absorption axis of the polarizer is 45 ° or 135 °. A pair of polarizers; a liquid crystal cell having at least one pair of substrates having electrodes constituting pixels on at least one opposing surface, and a liquid crystal layer disposed between the pair of substrates and twist-aligned at a twist angle of approximately 90 ° And an optical compensation film disposed between each of the pair of polarizers and the liquid crystal cell;
The pair of polarizers and the liquid crystal layer are arranged to be in a birefringence mode,
The optical compensation film is a laminated film having at least a support and an optically anisotropic layer containing liquid crystal fixed in a hybrid alignment state,
A method of driving a liquid crystal display device in which one pixel of the liquid crystal cell is composed of a red (R) pixel, a green (G) pixel, a blue (B) pixel, and a white (W) pixel,
In a gradation in which a substantially equal voltage V _RGB is applied between the electrodes constituting each of the R pixel, the G pixel, and the B pixel, according to the gradation L (where L satisfies 0 ≦ L ≦ 1), A driving method for a liquid crystal display device, wherein a voltage V _RGB and a voltage V _W satisfying the following (i) and (ii) are respectively applied between electrodes constituting a G pixel and between electrodes constituting a W pixel: :
(I) When 0 <L ≦ 0.5, T _G ≦ 0.25 × T _W
(Ii) When 0.5 <L ≦ 1, T _G ≦ 4 × T _W −3
However, _TG and _TW are normalized transmittances obtained by normalizing the transmittances of the G pixel and the W pixel, respectively, with the white luminance in the normal direction of the display surface of the liquid crystal display device being 1.

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