JP2007047697A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has a narrow horizontal view angle with simple constitution, has a wide vertical view angle, and further has less deterioration in luminance in a front direction. <P>SOLUTION: The liquid crystal display device comprises at least a liquid crystal cell comprising a pair of oppositely arranged substrates one of which has an electrode and a specified liquid crystal layer interposed between the substrates, and polarizing plates arranged outside the liquid crystal cell respectively. An optical anisotropic layer is provided on the surface of one polarizing plate which is close to the liquid crystal cell. The liquid crystal display device has at least the liquid crystal cell comprising the pair of oppositely arranged substrates one of which has the electrode and the specified liquid crystal layer interposed between the substrates and also has the polarizing plates arranged outside the liquid crystal cell respectively, and one polarizing plate having an optical anisotropic layer is arranged further outside. The optical anisotropic layer is provided on the surface close to the liquid crystal cell. The optical anisotropic layer is made of a hybrid-aligned compound, and an alignment control direction of the hybrid-aligned compound is nearly parallel to an axis of absorption of one of polarizing films. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bend type liquid crystal display device represented by an OCB (Optically Compensatory Bend) type.

  The liquid crystal display device includes at least a liquid crystal cell and a polarizing plate. And a polarizing plate consists of a protective film and a polarizing film at least. Generally, a polarizing plate is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating protective films on both sides. In the transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets (referred to as an optical compensation film or an optical compensation film) may be disposed. On the other hand, in a reflective liquid crystal display device, it is common to arrange a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate 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 the liquid crystal cell can be applied to both transmissive and reflective type, TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory Bend), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence) A display mode like a ferroelectric liquid crystal has been proposed.

  Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As an optical compensation sheet, a stretched birefringent polymer film has been conventionally used. In addition, a method of providing an optical compensation sheet formed of low-molecular or high-molecular liquid crystalline molecules on a transparent support instead of the optical compensation sheet made of a stretched birefringent film has been proposed. By using liquid crystalline molecules, it is possible to realize optical properties that cannot be obtained by conventional stretched birefringent polymer films by utilizing its various alignment forms. Furthermore, the structure which serves as both a protective film and an optical compensation sheet by adding birefringence to the protective film of the polarizing plate has been proposed.

  The optical properties of the optical compensation sheet can be determined according to the optical properties of the liquid crystal cell, specifically, the difference in display mode as described above. When liquid crystalline molecules are used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. Optical compensation sheets using liquid crystal molecules have already been proposed for various display modes.

  It was important to widen the viewing angle of liquid crystal display devices, but in recent years liquid crystal display devices have come to be used in various applications. For example, display devices for mobile phones and portable terminals (notebook personal computers) can prevent peeping. Therefore, a narrow viewing angle may be required. That is, it is required to enlarge the viewing angle in the vertical direction and narrow the viewing angle in the horizontal direction. Therefore, a method of disposing an optical compensation sheet and changing the retardation thereof to control the viewing angle (see Patent Document 1), or a method of narrowing the left-right direction viewing angle by narrowing the emitted light of the backlight (Patent Document 2). Have been proposed).

JP-A-2005-37784 JP 2001-30531 A

  However, such a viewing angle control film has problems such as insufficient expansion of the viewing angle in the vertical direction and lowering of the front luminance.

  The present invention has been made in view of the above-mentioned problems, and has a simple configuration, narrows the viewing angle in the left-right direction, wides the viewing angle in the up-down direction, and has a low front luminance reduction, in particular, bend mode. Another object is to provide an OCB type liquid crystal display device.

The present invention employs the following means in order to solve the above problems.
[1] A liquid crystal cell comprising at least a pair of opposed substrates having electrodes on one side and a liquid crystal layer containing a nematic liquid crystal material bend-oriented between the substrates, and polarized light respectively disposed outside the liquid crystal cell A liquid crystal display device comprising a plate,
The polarizing plate comprises at least a polarizing film and a protective film provided on at least one surface of the polarizing film, and an optically anisotropic layer is provided on a surface close to the liquid crystal cell of at least one polarizing plate ( However, the optically anisotropic layer may also be configured to serve as the protective film),
The optically anisotropic layer is composed of a hybrid-oriented compound, and the orientation control direction of the hybrid-oriented compound is substantially parallel to any one of the absorption axes of the polarizing film. apparatus.
[2] The liquid crystal display device according to [1], wherein the optically anisotropic layer is disposed on both sides of the liquid crystal cell.
[3] A liquid crystal cell comprising at least a pair of opposed substrates having electrodes on one side and a liquid crystal layer containing a nematic liquid crystal material bend-aligned between the substrates, and polarized light respectively disposed outside the liquid crystal cell A liquid crystal display device having a plate and further disposing a polarizing plate having at least one optically anisotropic layer on the outside thereof,
The polarizing plate comprises at least a polarizing film and a protective film provided on at least one surface of the polarizing film, and the optically anisotropic layer is provided on a surface close to the liquid crystal cell (provided that the optically different layer is provided). The isotropic layer may be configured to double as the protective film)
The optically anisotropic layer is composed of a hybrid-oriented compound, and the orientation control direction of the hybrid-oriented compound is substantially parallel to any one of the absorption axes of the polarizing film. apparatus.
[4] The thickness of the optically anisotropic layer is d [μm],
The average tilt angle of the hybrid-oriented compound in the optically anisotropic layer is β [°],
When the in-plane retardation of the optically anisotropic layer is Q [nm], the following formula 0.5 ≦ d ≦ 3.0
20 ≦ β ≦ 90
10 ≦ Q ≦ 500
The liquid crystal display device according to any one of [1] to [3], wherein:
[5] The liquid crystal display device according to any one of [1] to [4], wherein an alignment state of at least one of the optically anisotropic layers is changed by an external field.

  According to the present invention, it is possible to provide a liquid crystal display device having the same configuration as a conventional liquid crystal display device and having a function of optically compensating a liquid crystal cell. Further, in the liquid crystal display device of the present invention, the luminance at the time of black display in the left-right direction is increased, the viewing angle is narrowed, and peeping prevention can be prevented. As for the vertical viewing angle, the wide viewing angle unique to the conventional OCB mode could be maintained. Further, a bright OCB type liquid crystal display device can be provided without lowering the front luminance.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

Terms used in this specification will be described.
(Retardation Re, Rth)
In the present invention, Re ₍ λ ₎ which is the front retardation 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 _), which is retardation in the thickness direction, is + 40 ° with respect to the normal direction of the film, using Re ₍ λ _{) as} an in-plane slow axis (determined by KOBRA 21ADH) as a tilt axis (rotation axis). Retardation measured by injecting light of wavelength λ nm from the tilted direction, and light of wavelength λ nm from the direction tilted by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis) KOBRA 21ADH is calculated based on the retardation measured in three directions, the assumed value of the average refractive index, and the input film thickness value. Here, as the assumed value of the average refractive index, “Polymer Handbook” (John Wiley & Sons, Inc.) and catalog values of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

(Molecular orientation axis)
The sample 70mm x 100mm was conditioned at 25 ° C and 65% RH for 2 hours, and the molecule was determined from the phase difference when the incident angle at normal incidence was changed with an automatic birefringence meter (KOBRA21DH, Oji Scientific Co., Ltd.). The orientation axis was calculated.
(Axis misalignment)
Moreover, the axis | shaft misalignment angle was measured with the automatic birefringence meter (KOBRA-21ADH, Oji Scientific Instruments). Twenty points were measured at equal intervals over the entire width in the width direction, and the average absolute value was determined. The range of the slow axis angle (axis deviation) is the measurement of 20 points at equal intervals over the entire width direction, and the difference between the average of four points from the larger absolute value of the axis deviation and the average of the four points from the smaller one. Is taken.

(Transmittance)
The transmittance of visible light (615 nm) was measured on a 20 mm × 70 mm sample at 25 ° C. and 60% RH with a transparency measuring instrument (AKA phototube colorimeter, KOTAKI Corporation).
(Spectral characteristics)
A sample 13 mm × 40 mm was measured for transmittance at a wavelength of 300 to 450 nm with a spectrophotometer (U-3210, Hitachi, Ltd.) at 25 ° C. and 60% RH. The inclination width was obtained at a wavelength of 72% -5%. The limit wavelength was expressed by a wavelength of (gradient width / 2) + 5%. The absorption edge is represented by a wavelength with a transmittance of 0.4%. From this, the transmittances at 380 nm and 350 nm were evaluated.

  In the present specification, “45 degrees”, “parallel” or “vertical” means that the angle is within a range of strictly less than ± 5 degrees. That is, it means approximately 45 degrees, approximately parallel, and approximately vertical. The error from the exact angle is preferably less than 4 degrees, more preferably less than 3 degrees. 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 “ It is also used in the sense of 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. Furthermore, in the present invention, the polarizing plate may include an optical compensation sheet. In the present invention, the optically anisotropic layer can also serve as the protective film.

The liquid crystal display device of the first aspect of the present invention is
A liquid crystal cell comprising at least a pair of substrates arranged opposite to each other having electrodes on one side and a liquid crystal layer containing a nematic liquid crystal material bend-oriented between the substrates, and a polarizing plate disposed on the outside of the liquid crystal cell. A liquid crystal display device,
The polarizing plate comprises at least a polarizing film and a protective film provided on at least one surface of the polarizing film, and an optically anisotropic layer is provided on a surface close to the liquid crystal cell of at least one polarizing plate ( However, the optically anisotropic layer may also be configured to serve as the protective film),
The optically anisotropic layer is composed of a hybrid-oriented compound, and the orientation control direction of the hybrid-oriented compound is substantially parallel to any one of the absorption axes of the polarizing film. Device (hereinafter also referred to as “Liquid Crystal Display I”)
And
The liquid crystal display device of the second aspect of the present invention is
A liquid crystal cell comprising at least a pair of opposed substrates having electrodes on one side and a liquid crystal layer containing a nematic liquid crystal material bend-aligned between the substrates, and disposed outside the liquid crystal cell; A liquid crystal display device having a polarizing plate and further disposing a polarizing plate having at least one optically anisotropic layer on the outside thereof,
The polarizing plate comprises at least a polarizing film and a protective film provided on at least one surface of the polarizing film, and the optically anisotropic layer is provided on a surface close to the liquid crystal cell (provided that the optically different layer is provided). The isotropic layer may be configured to double as the protective film)
The optically anisotropic layer is composed of a hybrid-oriented compound, and the orientation control direction of the hybrid-oriented compound is substantially parallel to any one of the absorption axes of the polarizing film. Device (hereinafter also referred to as “Liquid Crystal Display II”)
It is.
Hereinafter, the liquid crystal display devices I and II may be collectively referred to as the liquid crystal display device of the present invention.

Hereinafter, constituent members of one embodiment of the liquid crystal display device of the present invention will be described in order.
FIG. 1 shows a schematic diagram of 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 13 in which the liquid crystal bends with respect to the substrate surface when a voltage is applied, that is, black display, and substrates 11 and 14 sandwiching the liquid crystal layer. The substrates 11 and 14 have a liquid crystal surface subjected to alignment treatment, and the rubbing direction is indicated by arrows 12 and 15. Polarizing films 3 and 22 are disposed so as to sandwich the liquid crystal cell. The absorption axes 4 and 23 of the polarizing films 3 and 22 are arranged orthogonal to each other and at an angle of 45 degrees with the rubbing directions 12 and 15 of the liquid crystal layer 13 of the liquid crystal cell. Protective films 5 and 20 and optically anisotropic layers 9 and 18 are disposed between the polarizing films 3 and 22 and the liquid crystal cell, respectively. The protective films 5 and 20 are arranged such that the slow axes 6 and 21 thereof are orthogonal to the directions of the absorption axes 4 and 23 of the polarizing films 3 and 22 adjacent thereto, respectively. The optically anisotropic layers 9 and 18 have optical anisotropy expressed by the orientation of the liquid crystal compound.

  The liquid crystal cell in FIG. 1 includes a liquid crystal layer formed of an upper substrate 11 and a lower substrate 14 and a liquid crystal layer 13 sandwiched therebetween. An alignment film (not shown) is formed on the surface of the substrates 11 and 14 that is in contact with the liquid crystal layer 13 (hereinafter sometimes referred to as “inner surface”). Is controlled in a parallel direction with a pretilt angle. Further, on the inner surfaces of the substrates 11 and 14, a transparent electrode (not shown) capable of applying a voltage to the liquid crystal layer composed of the liquid crystal layer 13 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 11 and 14, a liquid crystal material having a positive dielectric anisotropy such that the liquid crystal layer 13 responds 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 11 and 14. 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 the OCB mode liquid crystal display device, the chiral material generally used in the TN mode liquid crystal display device is rarely used to degrade the dynamic response characteristics, but is added to reduce alignment defects. Sometimes it is done. 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.

  The protective films 5 and 20 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 / Rth at a wavelength of 650 nm. (650 nm) preferably satisfies the relationship of 1.05 to 1.9 times Re / Rth (550 nm), and Rth is preferably 70 to 400 nm. The protective films 5 and 20 may function as a support for the optically anisotropic layers 9 and 18, may function as a protective film for the polarizing film 3 and the polarizing film 22, or both of them. It may have a function. That is, the polarizing film 3, the protective film 5, and the optically anisotropic layer 9, or the polarizing film 22, the protective film 20, and the optically anisotropic layer 18 are incorporated in the liquid crystal display device as an integrated laminate. Alternatively, they may be incorporated as individual members.

  Regarding the absorption axes 4 and 23 of the polarizing films 3 and 22, the slow axis directions 6 and 21 of the protective films 5 and 20, and the alignment direction of the liquid crystal layer 13, the materials used for each member, the display mode, and the laminated structure of the members It is preferable to adjust to the optimum range according to the above. That is, it is preferable that the absorption axis 4 of the polarizing film 3 and the absorption axis 23 of the polarizing film 22 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 9 and 18 are disposed between the protective films 5 and 20 and the liquid crystal cell. The optically anisotropic layers 9 and 18 are layers formed from a composition containing a liquid crystalline compound, for example, a rod-like compound or a discotic compound. Although FIG. 1 shows an embodiment having optically anisotropic layers on both sides of the liquid crystal cell, the liquid crystal display device I is not limited to this embodiment, and an optical device provided at least on one side of the liquid crystal cell. The anisotropic layer may be the above-described predetermined optical anisotropic layer. In the liquid crystal display device of the present invention, it is possible to have two or more optically anisotropic layers on one side of the liquid crystal cell.

  In the crossed Nicols state of a conventional polarizing plate without an optical compensation sheet, light leakage occurs during black display and the viewing angle is narrowed in four directions when observed from four oblique directions as shown by 50 in FIG.

On the other hand, the liquid crystal display device I has an optically anisotropic layer made of a hybrid-oriented compound on a protective film close to the liquid crystal cell of at least one polarizing plate, and the orientation control direction of the hybrid-oriented compound is liquid crystal It is comprised so that it may become substantially parallel with the any one absorption axis of the polarizing film contained in a display apparatus. (In the aspect shown in FIG. 1, the orientation control direction 19 of the lower optically anisotropic layer 18 is the upper polarized light. And is substantially parallel to the absorption axis 4 of the plate polarizing film 3). When the liquid crystal display device of the present invention is observed obliquely, there is only two directions of light leakage as shown in FIG. 3, an optical design with a wide viewing angle in the horizontal direction and a wide viewing angle is possible. In the hybrid orientation direction, the retardation decreases in the oblique viewing angle direction, but in the lateral direction of the orientation direction, the retardation increases in the oblique viewing angle direction, and the transmittance increases, and the image becomes white. In addition, the optically anisotropic layer may be disposed only on one side of the liquid crystal cell, but by arranging it on both sides, a vertically symmetric viewing angle characteristic can be obtained. The optically anisotropic layer can be provided on the protective film of the polarizing plate, but can also be provided directly on the polarizing film. In this case, the optically anisotropic layer can also serve as a protective film for the polarizing plate.
In the present invention, the “alignment control direction” can be, for example, a rubbing direction of an alignment film described later.

  Further, in the liquid crystal display device II, a polarizing plate further having at least one optically anisotropic layer is disposed outside the pair of polarizing plates, and the optically anisotropic layer is made of a hybrid-oriented compound, and The orientation control direction of the hybrid oriented compound is substantially parallel to any one absorption axis of the polarizing film included in the liquid crystal display device. Thereby, similarly to the liquid crystal display device I, an optical design with a narrow viewing angle in the left-right direction and a wide viewing angle in the up-down direction is possible. In the present invention, the viewing angle characteristics can also be changed by sandwiching the optically anisotropic layer between a substrate on which a transparent electrode is disposed, such as glass or a polyimide film, and changing the orientation by an external field such as an electric field. .

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. In addition, the liquid crystal display device of the present invention may be of a reflective type. In such a case, only one polarizing plate needs to be arranged on the observation side, and is reflected on the back surface of the liquid crystal cell or the inner surface of the lower substrate of the liquid crystal cell. A membrane can be installed. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Furthermore, the liquid crystal display device of the present invention may be an anti-transmission type in which a reflection portion and a transmission portion are provided in one pixel of the display device in order to achieve both transmission and reflection modes.
Furthermore, in order to increase the luminous efficiency of the backlight, a prismatic or lens-shaped condensing brightness enhancement sheet (film) is laminated, or a polarization reflection type brightness enhancement sheet (film) that improves light loss due to absorption of the polarizing plate. ) May be laminated between the backlight and the liquid crystal cell. In addition, a diffusion sheet (film) for making the light source of the backlight uniform may be laminated, and conversely, a sheet (film) formed by printing a reflection or diffusion pattern for giving an in-plane distribution to the light source. You may laminate.

  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 three-terminal or two-terminal semiconductor elements such as TFT and 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.

  In the present invention, by setting the slow axis of the protective film of the polarizing plate and the absorption axis of the polarizing film to have a predetermined relationship, the viewing angle of the liquid crystal display device is improved. By arranging the optical compensation sheet between them, the viewing angle can be further improved. The optical compensation sheet is not particularly limited and may have any configuration as long as it has optical compensation capability. For example, a birefringent polymer film, a laminated body of an optical compensation sheet composed of a transparent support and liquid crystal molecules formed on the transparent support, and the like can be mentioned. In the latter embodiment, the transparent protective film on the side close to the liquid crystal layer of the polarizing plate may also serve as the support for the optical compensation sheet.

Next, each member used for the liquid crystal display device of the present invention will be described.
In the present invention, an optically anisotropic layer containing a liquid crystalline compound fixed in an alignment state is used for optical compensation of the liquid crystal cell. In the present invention, the optically anisotropic layer may be formed on a support and incorporated in a liquid crystal display device as an optical compensation sheet, or an elliptically polarizing plate in which the optical compensation sheet and a linearly polarizing film are integrated. May be incorporated in the liquid crystal display device. The method for producing the optical compensation sheet and the polarizing plate whose angles are set as described above is not particularly limited, but the method for adjusting the orientation control direction and the stretching direction with respect to the roll conveying direction at the time of producing the optical compensation sheet or the polarizing plate. In addition, after the optical compensation sheet and the polarizing plate are produced by roll-to-roll, a method of punching at a set angle at the time of punching may be mentioned.

[Optical compensation sheet]
Examples of the optical compensation sheet that can be used in the present invention include an optically transparent support and an optically anisotropic layer formed from a liquid crystalline compound on the support. By using this optical compensation sheet in a liquid crystal display device, the liquid crystal cell can be optically compensated without deteriorating other characteristics.

Hereinafter, the constituent materials of the optical compensation sheet will be described.
<Support>
The optical compensation sheet may have a support. The direction of the slow axis of the transparent support to which the optically anisotropic layer is attached is not particularly limited, but may be −50 ° to 50 ° with respect to the alignment control direction (eg, rubbing direction) of the liquid crystalline compound. Preferably, it is −45 ± 5 °, 45 ° ± 5 °, or −5 ° to 5 °. The support is preferably glass or a transparent polymer film. The support preferably has a light transmittance of 80% or more. Examples of the polymer constituting the polymer film include cellulose esters (eg, cellulose mono- to triacylate), norbornene-based polymers, and polymethyl methacrylate. A commercially available polymer (for norbornene polymers, both Arton and Zeonex are trade names)) may be used. In addition, conventionally known polymers such as polycarbonate and polysulfone, which are likely to exhibit birefringence, have their birefringence controlled by modification of molecules as described in WO 00/26705. It is preferable to use one.

  Among these, cellulose esters are preferable, and lower fatty acid esters of cellulose are more preferable. Lower fatty acid means a fatty acid having 6 or less carbon atoms. In particular, cellulose acylate having 2 to 4 carbon atoms is preferable, and cellulose acetate is particularly preferable. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. The viscosity average degree of polymerization (DP) of cellulose acetate is preferably 250 or more, and more preferably 290 or more. Cellulose acetate 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. A specific value of Mw / Mn is preferably 1.0 to 1.7, and more preferably 1.0 to 1.65.

  As the polymer film, it is preferable to use cellulose acetate having an acetylation degree of 55.0 to 62.5%. The acetylation degree is more preferably 57.0 to 62.0%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is determined by measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

In cellulose acetate, the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are not evenly substituted but the degree of substitution at the 6-position tends to be small. In the polymer film used in the present invention, it is preferable that the degree of substitution at the 6-position of cellulose is the same or greater than that at the 2- and 3-positions. The ratio of the substitution degree at the 6-position to the total substitution degree at the 2-position, the 3-position and the 6-position is preferably 30 to 40%, more preferably 31 to 40%, and more preferably 32 to 40%. Most preferably it is. The substitution degree at the 6-position is preferably 0.88 or more.
These specific acyl groups and a method for synthesizing cellulose acylate are described in detail on page 9 of JIII Journal of Technical Disclosure No. 2001-1745 (issued on March 15, 2001).

Although the preferred range of the retardation value of the polymer film varies depending on the liquid crystal cell in which the optical compensation sheet is used and the method of use thereof, the front retardation Re is preferably 0 to 200 nm, and the retardation Rth in the thickness direction is preferred. Is preferably in the range of 70 to 400 nm. When two optically anisotropic layers are used in a liquid crystal display device, the Rth of the polymer film is preferably in the range of 70 to 250 nm. When a single optically anisotropic layer is used in a liquid crystal display device, the retardation of the substrate is preferably in the range of 150 to 400 nm.
In addition, it is preferable that the birefringence ((DELTA) n: nx-ny) of a base film exists in the range of 0.00028-0.020. The birefringence {(nx + ny) / 2−nz} in the thickness direction of the cellulose acetate film is preferably in the range of 0.001 to 0.04.

  In order to adjust the retardation of the polymer film, a method of applying an external force such as stretching is common, but a retardation increasing agent for adjusting optical anisotropy can also be used. In order to adjust the retardation of the cellulose acylate film, an aromatic compound having at least two aromatic rings is preferably used as a retardation increasing agent. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Examples thereof include compounds described in European Patent Application Publication No. 91656, JP-A 2000-1111914, 2000-275434, and the like.

Furthermore, in the present invention, the hygroscopic expansion coefficient of the cellulose acetate film used for the optical compensation sheet is preferably 30 × 10 ⁻⁵ /% RH or less, and more preferably 15 × 10 ⁻⁵ /% RH or less. More preferably, it is 10 × 10 ⁻⁵ /% RH or less. Further, the hygroscopic expansion coefficient is preferably small, but usually a value of 1.0 × 10 ⁻⁵ /% RH or more. The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed at a constant temperature. By adjusting the hygroscopic expansion coefficient, it is possible to prevent a frame-like transmittance increase (light leakage due to distortion) while maintaining the optical compensation function of the optical compensation sheet.
The method for measuring the hygroscopic expansion coefficient is shown below. A sample having a width of 5 mm and a length of 20 mm is cut out from the produced polymer film, and one end is fixed and suspended in an atmosphere of 25 ° C. and 20% RH (R ₀ ). A weight of 0.5 g is hung on the other end and left for 10 minutes to measure the length (L ₀ ). Next, with the temperature kept at 25 ° C., the humidity is set to 80% RH (R ₁ ), and the length (L ₁ ) is measured. Based on the above measured values, the hygroscopic expansion coefficient can be calculated by the following equation. As measurement values, 10 samples can be taken for the same sample, and an average value can be adopted.
Hygroscopic expansion coefficient [/% RH] = {(L ₁ −L ₀ ) / L ₀ } / (R ₁ −R ₀ )

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

  Additives described above to be added to the polymer film or additives that can be added in accordance with various purposes (for example, UV inhibitors, release agents, antistatic agents, deterioration inhibitors (eg, antioxidants, peroxide decomposers, The radical inhibitor, metal deactivator, acid scavenger, amine), infrared absorber and the like may be solid or oily. Moreover, when a film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For these details, the materials described in detail on pages 16 to 22 of the above-mentioned public technical number 2001-1745 are preferably used. The amount of these additives to be used is not particularly limited as long as the amount of each material exhibits its function, but it is preferably used in the range of 0.001 to 25% by mass in the entire polymer film composition.

<< Production Method of Polymer Film (Support) >>
The polymer film is preferably produced by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which a polymer material is dissolved in an organic solvent. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state.

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

In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially.
As a method of co-casting a plurality of cellulose acylate solutions of two or more layers as described above, for example, a solution containing cellulose acylate from a plurality of casting openings provided at intervals in the traveling direction of the support. A method of casting and laminating each (for example, a method described in JP-A-11-198285) A method of casting a cellulose acylate solution from two casting ports (a method described in JP-A-6-134933) A method of wrapping a flow of a high-viscosity cellulose acylate solution with a low-viscosity cellulose acylate solution and simultaneously extruding the high- and low-viscosity cellulose acylate solution (method described in JP-A-56-162617), etc. Can be mentioned. The present invention is not limited to these. The manufacturing process of these solvent casting methods is described in detail on pages 22 to 30 of the above-mentioned public technical number 2001-1745, and includes dissolution, casting (including co-casting), metal support, drying, It is classified as peeling or stretching.
In the present invention, the thickness of the film (support) is preferably 15 to 120 μm, and more preferably 30 to 80 μm.

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

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

  Instead of surface treatment, in addition to the surface treatment, a single layer in which only a single undercoat layer (described in JP-A-7-333433) or a resin layer such as gelatin containing both a hydrophobic group and a hydrophilic group is applied A hydrophilic resin layer such as gelatin (hereinafter referred to as an undercoat first layer) is provided as a first layer, and a gelatin layer or other hydrophilic resin layer (hereinafter referred to as an undercoat first layer) as a second layer. Also, a so-called multi-layer method (for example, described in JP-A No. 11-248940) in which an undercoat second layer is applied can be used.

《Alignment film》
In the present invention, the liquid crystalline compound in the optically anisotropic layer is controlled in alignment by the alignment axis and fixed in that state. Examples of the alignment axis for controlling the alignment of the liquid crystalline compound include a rubbing axis of an alignment film formed between the optically anisotropic layer and the polymer film (support). However, in the present invention, the alignment axis is not limited to the rubbing axis, and any alignment axis may be used as long as it can control the alignment of the liquid crystalline compound in the same manner as the rubbing axis.

  The alignment film has a function of defining the alignment direction of the liquid crystalline molecules. Therefore, the alignment film is indispensable for realizing a preferred embodiment of the present invention. However, if the alignment state is fixed after aligning the liquid crystalline compound, the alignment film plays the role, and thus is not necessarily an essential component of the present invention. That is, it is also possible to produce a polarizing plate by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizing film.

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

  The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules. In the present invention, in addition to the function of aligning liquid crystalline molecules, a cross-linking having a function of aligning a side chain having a crosslinkable functional group (eg, double bond) to the main chain or aligning liquid crystalline molecules. It is preferable to introduce a functional functional group into the side chain. As the polymer used in the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of the polymer include methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol) described in paragraph No. [0022] of JP-A-8-338913. Acrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. . It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization.

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

  A side chain having a function of aligning liquid crystal molecules generally has a hydrophobic group as a functional group. The specific type of functional group can be determined according to the type of liquid crystal molecule and the required alignment state. For example, the modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, fluorine atoms Substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy) and the like can be mentioned. As specific examples of these modified polyvinyl alcohol compounds, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426 are described. [0022] and the like.

When a side chain having a crosslinkable functional group is bonded to the main chain of the alignment film polymer or a crosslinkable functional group is introduced into a side chain having a function of aligning liquid crystalline molecules, the alignment film polymer and the optically anisotropic film The polyfunctional monomer contained in the conductive layer can be copolymerized. As a result, not only between the polyfunctional monomer and the polyfunctional monomer, but also between the alignment film polymer and the alignment film polymer and between the polyfunctional monomer and the alignment film polymer is firmly bonded by a covalent bond. Therefore, the strength of the optical compensation sheet can be remarkably improved by introducing the crosslinkable functional group into the alignment film polymer.
The crosslinkable functional group of the alignment film polymer preferably contains a polymerizable group in the same manner as the polyfunctional monomer. Specifically, for example, those described in paragraphs [0080] to [0100] of JP-A No. 2000-155216, and the like can be mentioned.

  Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent. Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole, and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [024] in JP-A No. 2002-62426. Among them, an aldehyde having a high reaction activity, particularly glutaraldehyde is preferable.

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

  The alignment film can be basically formed by coating the polymer, which is an alignment film forming material, on a transparent support containing a crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be carried out at any time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (eg, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an orientation film and also an optically anisotropic layer reduces remarkably.

  The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient cross-linking, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is particularly preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is 4.5 to 5.5, and 5 is particularly preferable.

  The alignment film can be provided on the transparent support or the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.

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

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

<< Optically anisotropic layer >>
Next, details of preferred embodiments of the optically anisotropic layer made of a liquid crystalline compound will be described.
The optically anisotropic layer is preferably designed so as to compensate for the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device. The alignment state of the liquid crystal compound in the liquid crystal cell in black display varies depending on the mode of the liquid crystal display device. The alignment state of the liquid crystal compound in this liquid crystal cell is described in IDW'00, FMC7-2, P411-414. The optically anisotropic layer contains a liquid crystal compound in which the orientation is controlled by an orientation axis such as a rubbing axis and the orientation is fixed.

In the liquid crystal display device of the present invention, the optically anisotropic layer made of a hybrid-oriented compound and having an orientation control direction substantially parallel to the absorption axis of the polarizing film has a thickness of d [μm]. When the average tilt angle of the hybrid-oriented compound in the optically anisotropic layer is β [°] and the in-plane retardation of the optically anisotropic layer is Q [nm], the following formula:
0.5 ≦ d ≦ 3.0
20 ≦ β ≦ 90
10 ≦ Q ≦ 500
It is preferable to satisfy.
Here, the hybrid-oriented optically anisotropic layer has a thickness, an average inclination angle β [°] of the hybrid-oriented compound, and an in-plane retardation Q [nm] of the optically anisotropic layer. The magnitude of the leaked light in the oblique direction changes.
The following formula 0.5 ≦ d ≦ 3.0
20 ≦ β ≦ 90
10 ≦ Q ≦ 500
Leakage light is generated when satisfying the condition, and it is effective for preventing peeping in an oblique direction. When it is smaller than this range, the retardation of the optically anisotropic layer generated in the oblique direction is small, and the leakage light is small. On the other hand, if it is larger than this range, there is a risk that the transmittance will be significantly reduced and a coloring phenomenon may occur.

  Examples of liquid crystalline molecules used for the optically anisotropic layer include rod-like liquid crystalline molecules and discotic liquid crystalline molecules. The rod-like liquid crystal molecules and the disk-like liquid crystal molecules may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which low-molecular liquid crystals are cross-linked and no longer exhibit liquid crystallinity. When a rod-like liquid crystalline compound is used for the production of the optically anisotropic layer, it is preferable that the rod-like liquid crystalline molecule has an average direction in which the major axis is projected on the support surface is parallel to the alignment axis. . Further, when a discotic liquid crystalline compound is used for the production of the optically anisotropic layer, the average direction of the axis of the discotic liquid crystalline molecule projected on the support surface is parallel to the alignment axis. It is preferable. In addition, as described above, the liquid crystal display device of the present invention is a compound having a hybrid alignment in which the angle (tilt angle) between the major axis of liquid crystalline molecules (the disk surface in the case of disk-like molecules) and the layer plane changes in the depth direction. An optically anisotropic layer comprising:

《Bar-shaped liquid crystalline molecules》
As rod-like liquid crystalline molecules, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 of the Chemical Chemistry of the Quarterly Chemical Review Vol. 22, Liquid Crystal Chemistry (1994), and the 142nd Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.
The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.

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

《Disk-like liquid crystalline molecule》
For discotic liquid crystal molecules, 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.

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

  In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. Examples thereof include compounds described in paragraphs [0151] to “0168” in JP-A No. 2000-155216.

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

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

<< Other additives in optically anisotropic layer >>
Along with the liquid crystal molecules, a plasticizer, a surfactant, a polymerizable monomer, and the like can be used in combination to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, and the like. It is preferable that the compound has compatibility with the liquid crystal molecules and can change the tilt angle of the liquid crystal molecules or does not inhibit the alignment.

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

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

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

<< Formation of optically anisotropic layer >>
The optically anisotropic layer can be formed by applying a coating liquid containing liquid crystalline molecules and, if necessary, a polymerizable initiator described later and optional components on the alignment film.

  As the solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

  The coating liquid can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

  The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

<Fixing the alignment state of liquid crystalline molecules>
The aligned liquid crystal molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

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

  As an optical compensation sheet other than a discotic compound, an optical compensation sheet comprising a stretched birefringent polymer film, and an optical compensation sheet having an optically anisotropic layer formed from a low-molecular or high-molecular liquid crystalline compound on a transparent support However, any of them can be used in the present invention. In addition, an optical compensation sheet having a laminated structure can be used, including a laminate of two optical compensation sheets. Regarding the optical compensation sheet having a laminated structure, in consideration of the thickness, an optical compensation sheet made of a coating-type laminate is preferred to an optical compensation sheet made of a laminate of stretched polymer films.

  The polymer film used as the optical compensation sheet may be a stretched polymer film or a combination of a coating type polymer layer and a polymer film. As a material for the polymer film, a synthetic polymer (eg, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin, triacetylcellulose) is generally used.

  Since the liquid crystalline compound has various alignment forms, the optically anisotropic layer made of the liquid crystalline compound can exhibit desired optical properties by a single layer or by a laminate of a plurality of layers. That is, the optical compensation sheet may be an embodiment comprising a support and one or more optically anisotropic layers formed on the support. The retardation of the entire optical compensation sheet of this aspect can be adjusted by the optical anisotropy of the optically anisotropic layer. Liquid crystal compounds can be classified into rod-like liquid crystal compounds and discotic compounds based on their shapes. Furthermore, there are low molecular weight and high molecular weight types, respectively, and both can be used. The optically anisotropic layer made of a liquid crystal compound used in the present invention preferably uses a rod-like liquid crystal compound or a discotic compound as the liquid crystal compound, and more preferably uses a discotic compound having a polymerizable group.

《Ellipse Polarizing Plate》
In the present invention, an elliptically polarizing plate in which the optically anisotropic layer is integrated with a linear polarizing film can be used. It is preferable that the elliptically polarizing plate is molded into substantially the same shape as the pair of substrates constituting the liquid crystal cell so that it can be incorporated into the liquid crystal display device as it is (for example, if the liquid crystal cell is rectangular, the elliptically polarizing plate). The plate is also preferably molded into the same rectangular shape). As described above, in the liquid crystal display device of the present invention, in the optically anisotropic layer disposed at a predetermined position, the orientation control direction of the hybrid oriented compound is substantially parallel to any one absorption axis of the polarizing film. It is comprised so that it may become.

  The elliptically polarizing plate can be manufactured by laminating the optically anisotropic layer and a linearly polarizing film (hereinafter simply referred to as “linearly polarizing film” when referred to as “polarizing film”). The optically anisotropic layer may also serve as a protective film for the linearly polarizing film.

  The linear polarizing film is manufactured by Optiva Inc. And a polarizing film comprising a binder and iodine or a dichroic dye is preferable. The iodine and the dichroic dye in the linearly polarizing film exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal. At present, a commercially available polarizing film is produced by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.

  The commercially available polarizing film has iodine or dichroic dye distributed about 4 μm (about 8 μm on both sides) from the polymer surface, and a thickness of at least 10 μm is necessary to obtain sufficient polarization performance. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time. As described above, the lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed on a 17-inch liquid crystal display device.

  The binder contained in the polarizing film may be cross-linked. As the crosslinked binder, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. A polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally carried out by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is sufficient if durability can be ensured at the final product stage, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained. Examples of the polymer include the same polymers as those described in the alignment film. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination. As for the addition amount of the crosslinking agent in a binder, 0.1-20 mass% is preferable with respect to a binder. Thereby, the orientation of the polarizing element and the moisture and heat resistance of the polarizing film are improved.

The polarizing film contains some crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less, more preferably 0.5% by mass or less in the polarizing film. In this way, even if the polarizing film is incorporated in a liquid crystal display device and used for a long time or left in a high temperature and high humidity atmosphere for a long time, the degree of polarization does not decrease.
The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.

As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl).
As an example of a dichroic dye, the compound as described in page 58 of the said technical number 2001-1745 is mentioned, for example.

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

<< Manufacture of elliptically polarizing plates >>
The elliptically polarizing plate can be produced by a stretching method or a rubbing method. When producing by a drawing method, the draw ratio is preferably 2.5 to 30.0 times, more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be performed in several steps including oblique stretching. By dividing into several times, it can be stretched more uniformly even at high magnification. Before the oblique stretching, a slight stretching (a degree to prevent shrinkage in the width direction) may be performed horizontally or vertically. Stretching can be performed by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. In biaxial stretching, stretching is performed at different speeds on the left and right, so that the thickness of the binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.

  In the rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. Generally, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are all 30 μm or less. The film wrap angle on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more.

  When rubbing a long film, the film is preferably transported at a speed of 1 to 100 m / min in a constant tension state by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a liquid crystal display device, the angle is preferably 40 to 50 °. 45 ° is particularly preferred.

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

The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. In addition, “%” described below indicates “% by mass” unless otherwise specified.
[Example 1]
Below, the manufacturing method of each used member is demonstrated.
<Preparation of OCB mode liquid crystal cell>
The manufactured liquid crystal display will be described with reference to FIG.
A transparent electrode (not shown) made of ITO is formed on one of the transparent substrates 11, 14 and the inside of the substrate, and an orientation control film (not shown) is formed thereon. The rod-like liquid crystal molecules 13 sandwiched between the substrates are spray-oriented when no electric field is applied. In this case, the dielectric anisotropy of the liquid crystal is assumed to be positive. When an electric field is applied, the liquid crystalline molecules 13 change their direction in the direction of the electric field and become bend alignment.
The liquid crystal cell had a cell gap of 6 μm, a liquid crystal material having a positive dielectric constant anisotropic layer (for example, ZLI4722 manufactured by Merck) was enclosed between the substrates by drop injection, and the retardation Re value of the liquid crystal layer 13 was 780 nm.

<Preparation of upper and lower polarizing plates>
The stacking angle of each film is based on the horizontal direction of the display device. The angle of the slow axis 2 of the upper polarizing plate protective film 1 is 90 °, the angle of the slow axis 6 of the upper polarizing plate protective film 5 is 0 °, The angle of the absorption axis 4 of the film 3 is 90 °, the angle of the absorption axis 23 of the lower polarizing plate polarizing film 22 is 0 °, the angle of the slow axis 25 of the lower polarizing plate protective film 24 is 0 °, and the lower polarizing plate The angle of the slow axis 21 of the protective film 20 was set to 90 °. Further, the protective film of the upper and lower polarizing plates was made of a cellulose acetate film, and Re was set to 40 nm and Rth was set to 180 nm. Optically anisotropic layers 7, 16 and 18 are sequentially formed on the protective film (transparent protective film) of the upper and lower polarizing plates, and the optically anisotropic layer is close to the liquid crystal cell between the liquid crystal cell and the protective film. It arranged so that it might become a position.
The optically anisotropic layer was formed by hybrid orientation of a discotic compound. The Re of the optically anisotropic layer was 60 nm, and the angle of the same orientation direction (orientation control direction) 17 was 90 °. The orientation control direction 10 of the optically anisotropic layer 7 was set to 225 °, the orientation control direction 17 of the optically anisotropic layer 16 was set to 90 °, and the orientation control direction 19 of the optically anisotropic layer 18 was set to 225 °. That is, in this liquid crystal display device, the orientation control direction of the optically anisotropic layer 16 is substantially parallel to the absorption axis of the polarizing film 3.

<Production of cellulose acetate film>
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose acetate solution.
Cellulose acetate solution composition Cellulose acetate having an acetylation degree of 60.7 to 61.1% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first Solvent) 336 parts by mass Methanol (second solvent) 29 parts by mass 1-butanol (third solvent) 11 parts by mass

  In another mixing tank, 16 parts by mass of the following retardation increasing agent, 92 parts by mass of methylene chloride and 8 parts by mass of methanol were added and stirred while heating to prepare a retardation increasing agent solution. A dope was prepared by mixing 474 parts by mass of the cellulose acetate solution with 25 parts by mass of the retardation increasing agent solution and stirring sufficiently. The addition amount of the retardation increasing agent was 6.0 parts by mass with respect to 100 parts by mass of cellulose acetate.

  The obtained dope was cast using a band stretching machine. After the film surface temperature on the band reached 40 ° C., the film was dried with warm air of 70 ° C. for 1 minute, and the film was dried from the band with 140 ° C. drying air for 10 minutes. A cellulose acetate film (thickness: 80 μm) was prepared. About the produced cellulose acetate film (transparent support body, transparent protective film), Re and Rth at a wavelength of 546 nm were measured using an ellipsometer (M-150, manufactured by JASCO Corporation). Re was 8 nm and Rth was 78 nm. The produced cellulose acetate film was immersed in a 2.0N potassium hydroxide solution (25 ° C.) for 2 minutes, neutralized with sulfuric acid, washed with pure water, and then dried. Thus, a cellulose acetate film for a transparent protective film was produced.

<Preparation of alignment film for optically anisotropic layer>
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. Next, the formed film was rubbed so as to be oriented in a direction parallel to the in-plane slow axis (the direction parallel to the casting direction) of the cellulose acetate film (that is, the rubbing axis is the slow axis of the cellulose acetate film). Parallel to the phase axis).
Alignment film coating solution composition Modified polyvinyl alcohol 20 parts by weight Water 360 parts by weight Methanol 120 parts by weight Glutaraldehyde (crosslinking agent) 1.0 part by weight

<Preparation of optically anisotropic layer>
On the alignment film, 91.0 g of the following discotic (liquid crystalline) compound, 9.0 g of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.), cellulose acetate butyrate (CAB551-) 0.2, manufactured by Eastman Chemical Co., Ltd.) 2.0 g, cellulose acetate butyrate (CAB531-1, manufactured by Eastman Chemical Co., Ltd.) 0.5 g, photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Co.) 3.0 g, Dissolve 1.0 g of sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) and 1.3 g of fluoroaliphatic group-containing copolymer (Megafac F780, Dainippon Ink Co., Ltd.) in 207 g of methyl ethyl ketone. The applied coating solution was applied with 6.2 ml / m ² with a # 3.6 wire bar. This was heated in a constant temperature zone of 130 ° C. for 2 minutes to orient the discotic compound. Next, UV irradiation was performed for 1 minute using a 120 W / cm high pressure mercury lamp in an atmosphere of 60 ° C. to polymerize the discotic compound. Then, it stood to cool to room temperature. Thus, an optically anisotropic layer was formed and an optical compensation sheet was produced.

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

<Preparation of polarizing film>
A polarizing film was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and the optical compensation sheet was attached to one side of the polarizing film on the support surface using a polyvinyl alcohol-based adhesive. Further, a cellulose triacetate film (TD-80U, manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was subjected to saponification treatment, and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. The absorption axis of the polarizing film and the slow axis (parallel to the casting direction) of the support of the optical compensation sheet were arranged in parallel. In this way, a polarizing plate was produced.

<Optical measurement of the produced liquid crystal display device>
A rectangular wave voltage of 60 Hz was applied to the liquid crystal display device thus manufactured. A normally white mode of 2V white display and 5V black display was set. A measuring device (EZ-Contrast 160D, manufactured by ELDIM) was used, and a contrast ratio, which is a transmittance ratio (white display / black display), was measured. A front contrast ratio of 700 to 1 was obtained. In addition, the viewing angle with a contrast of 10 or more in the left-right direction was 40 °. On the other hand, the upward direction was 80 ° and the downward direction was 80 °.

[Comparative Example 1]
It was set as the structure which removed the lower optically anisotropic layer 16 of the produced said OCB mode liquid crystal cell. Other configurations were the same as those in Example 1. The viewing angle with a contrast of 10 or more was 80 ° in the vertical and horizontal directions.

  From the comparison between Example 1 and Comparative Example 1, the viewing angle in the vertical direction is maintained by configuring the orientation control direction of the hybrid-oriented optically anisotropic layer and the absorption axis of the polarizing film to be substantially parallel. However, it can be seen that the viewing angle in the left-right direction can be narrowed. Furthermore, in Example 1, it was also confirmed that the luminance at the time of black display in the left-right direction was increased because the front luminance was small.

[Example 2]
A polarizing plate 7 with an optically anisotropic layer produced in the same formulation as in Example 1 was placed on the surface of a commercially available liquid crystal TV, Nanao SC23XA1, on which an OCB panel is mounted. FIG. 5 shows the configuration. Here, the absorption axis direction 4 of the polarizing film 3 on the front side of the commercial TV is 90 °, the absorption axis direction of the additional polarizing plate 7 is also 90 °, and the orientation control of the optically anisotropic layer integrally formed with the polarizing plate 7 is performed. The direction 8 was also 90 °.
The viewing angle with a contrast of 10 or more in the left-right direction was 40 ° compared to 80 ° on a commercial TV. On the other hand, the vertical direction was 80 °, which was the same as a commercial TV. As described above, in this example, the polarizing plate having the optically anisotropic layer further hybrid-aligned is arranged outside the polarizing plate, and the orientation control direction in the optically anisotropic layer and the absorption axis of the polarizing film are set. By arranging them substantially in parallel, it was possible to narrow only the viewing angle in the left-right direction while maintaining the viewing angle in the up-down direction. Furthermore, in Example 2, it was also confirmed that the luminance at the time of black display in the left-right direction was increased because the front luminance was less decreased.

[Example 3]
A liquid crystal display device having a configuration in which the optically anisotropic layer of the polarizing plate 7 with the optically anisotropic layer was replaced with a liquid crystal cell in the configuration of FIG. 5 described in Example 2 was produced. The liquid crystal cell uses two 50 × 40 mm solid electrode glass substrates with ITO, a vertical alignment film is applied to one substrate, a horizontal alignment film is applied to the other substrate, and rubbed to form a hybrid alignment cell (optical anisotropy). Corresponding to the layer). As the liquid crystal material, for example, ZLI4792 manufactured by Merck & Co., Inc. was used, and the cell gap was set to 5 μm.
When no voltage was applied, the viewing angle with a contrast of 10 or more in the left-right direction was 40 °, and the vertical direction was 80 °. When an AC rectangular wave with a frequency of 30 Hz and 5 V were applied, the viewing angle with a contrast of 10 or more was 80 ° in the vertical and horizontal directions as in a commercial TV. When no electric field is applied, the orientation control direction of the hybrid alignment cell is substantially parallel to the absorption axis of the polarizing film as in the second embodiment, so that the viewing angle in the left-right direction can be narrowed compared to when an electric field is applied. did it. Furthermore, in Example 3, it was also confirmed that the luminance at the time of black display in the left-right direction was increased because the front luminance was small.

  The liquid crystal display device of the present invention is suitable as a display device for a mobile phone or a mobile terminal (notebook personal computer).

It is a schematic diagram which shows the example of the liquid crystal display device of this invention. It is a schematic diagram which shows the leak light of the conventional polarizing plate. It is a schematic diagram which shows the leak light of the polarizing plate in the liquid crystal display device of this invention. It is a schematic diagram which shows the example of the liquid crystal display device of this invention. It is a schematic diagram which shows the example of the liquid crystal display device of this invention.

Explanation of symbols

1 Upper polarizing plate protective film 1
2 Upper polarizing plate protective film 1 Slow axis 3 Upper polarizing plate polarizing film 4 Upper polarizing plate polarizing film Absorption axis 5 Upper polarizing plate protective film 2
6 Upper polarizing plate protective film 2 Slow axis 7 Polarizing plate with optical anisotropic layer 8 Orientation control direction 9 of optical anisotropic layer of polarizing plate 7 Upper optical anisotropic layer 10 Orientation of upper optical anisotropic layer Control direction 11 Liquid crystal cell upper substrate 12 Upper substrate Liquid crystal alignment rubbing direction 13 Liquid crystal molecule 14 Liquid crystal cell lower substrate 15 Lower substrate Liquid crystal alignment rubbing direction 18 Lower optical anisotropic layer 19 Lower optical anisotropic layer Orientation control direction 20 Lower polarizing plate protective film 2
21 Lower polarizing plate protective film 2 Slow axis 22 Lower polarizing plate polarizing film 23 Lower polarizing plate polarizing film absorption axis 24 Lower polarizing plate protective film 1
25 Lower polarizing plate protective film 1 Slow axis 50 Leakage light generation region 51 Upper polarizing plate absorption axis 52 Lower polarizing film absorption axis 53 Orientation control direction of optical anisotropic layer

Claims (5)

A liquid crystal cell comprising at least a pair of substrates arranged opposite to each other having electrodes on one side and a liquid crystal layer containing a nematic liquid crystal material bend-oriented between the substrates, and a polarizing plate disposed on the outside of the liquid crystal cell. A liquid crystal display device,
The polarizing plate comprises at least a polarizing film and a protective film provided on at least one surface of the polarizing film, and an optically anisotropic layer is provided on a surface close to the liquid crystal cell of at least one polarizing plate ( However, the optically anisotropic layer may also be configured to serve as the protective film),
The optically anisotropic layer is composed of a hybrid-oriented compound, and the orientation control direction of the hybrid-oriented compound is substantially parallel to any one of the absorption axes of the polarizing film. apparatus. The liquid crystal display device according to claim 1, wherein the optically anisotropic layer is disposed on both sides of the liquid crystal cell. At least a liquid crystal cell comprising a pair of opposed substrates having electrodes on one side and a liquid crystal layer containing a nematic liquid crystal material bend-aligned between the substrates, and a polarizing plate disposed on the outside of the liquid crystal cell are provided. Further, a liquid crystal display device in which a polarizing plate having at least one optically anisotropic layer is disposed on the outside thereof,
The polarizing plate comprises at least a polarizing film and a protective film provided on at least one surface of the polarizing film, and the optically anisotropic layer is provided on a surface close to the liquid crystal cell (provided that the optically different layer is provided). The isotropic layer may be configured to double as the protective film)
The optically anisotropic layer is composed of a hybrid-oriented compound, and the orientation control direction of the hybrid-oriented compound is substantially parallel to any one of the absorption axes of the polarizing film. apparatus. The thickness of the optically anisotropic layer is d [μm],
The average tilt angle of the hybrid-oriented compound in the optically anisotropic layer is β [°],
When the in-plane retardation of the optically anisotropic layer is Q [nm], the following formula 0.5 ≦ d ≦ 3.0
20 ≦ β ≦ 90
10 ≦ Q ≦ 500
The liquid crystal display device according to claim 1, wherein: 5. The liquid crystal display device according to claim 1, wherein an alignment state of at least one of the optically anisotropic layers is changed by an external field.