JP2006235580A - Liquid crystal display device and elliptical polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device excellent in reliability which causes no leakage of light in the periphery of a polarizing plate without lowering display characteristics even in a severe use environment, and to provide an elliptically polarizing plate for the apparatus. <P>SOLUTION: The liquid crystal display device comprises: a pair of substrates 9, 12; a liquid crystal layer 11 containing liquid crystal molecules the alignment of which is controlled by alignment axes 10, 13 possessed by the counter faces of the substrates 9, 12, respectively; a pair of polarizing films 3, 18 disposed to sandwich the liquid crystal layer 11; and at least one layer of optical anisotropic layer 7, 14 which is disposed between the liquid crystal layer 11 and at least one of the polarizing films 3, 18 and which contains a liquid crystal compound with the alignment controlled by the alignment axes 8, 15 and fixed in this alignment state. The absorption axes 4, 19 of the polarizing films are parallel or perpendicular to the horizontal direction on the screen of the display device. At least one of the alignment axes 10, 13 of the substrates and the alignment axis 8, 15 of at least one layer of optical anisotropic layers give an intersection angle of 10 to 35°. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device having a wide viewing angle characteristic excellent in durability and an elliptically polarizing plate used therefor.

  A cathode ray tube (CRT) has been mainly used so far as a display device used for OA equipment such as a word processor, a notebook personal computer, a personal computer monitor, a portable terminal, and a television. In recent years, liquid crystal display devices have been widely used instead of CRTs because of their thinness, light weight, and low power consumption. The liquid crystal display device includes a liquid crystal cell and a polarizing plate. The polarizing plate is usually composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of a polyvinyl alcohol film with iodine, stretching, and laminating both surfaces with a protective film. 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 may be disposed. In a reflective liquid crystal display device, usually, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. A liquid crystal cell usually comprises liquid crystal molecules, two substrates for encapsulating the liquid crystal molecules, and an electrode layer for applying a voltage to the liquid crystal molecules. The liquid crystal cell performs ON-OFF display depending on the alignment state of liquid crystal molecules, and can be applied to any of a transmission type, a reflection type, and a semi-transmission type, TN (Twisted Nematic), IPS (In-Plane Switching), Display modes such as OCB (Optically Compensatory Bend), VA (Vertically Aligned), ECB (Electrically Controlled Birefringence), and STN (Super Twisted Nematic) are 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. It has been proposed to use an optical compensation sheet having an optically anisotropic layer formed from a low-molecular or high-molecular liquid crystalline compound on a transparent support, instead of the optical compensation sheet comprising a stretched birefringent film. Since liquid crystal compounds have various alignment forms, it has become possible to realize optical properties that cannot be obtained with conventional stretched birefringent polymer films by using liquid crystal compounds. Furthermore, it functions as a protective film for the polarizing plate.

  The optical properties of the optical compensation sheet are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. When a liquid crystal compound is used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. Various optical compensation sheets using liquid crystal compounds corresponding to various display modes have already been proposed. For example, an optical compensation sheet for a TN mode liquid crystal cell optically compensates for an alignment state tilted on the substrate surface while eliminating the twisted structure of liquid crystal molecules by applying a voltage, and prevents contrast leakage by preventing light leakage in an oblique direction during black display. Improve viewing angle characteristics.

  As described above, in the TN mode liquid crystal display device, the viewing angle characteristics are improved, but the problem that the polarizing plate contracts in a severe use environment, for example, a high temperature or high humidity environment, and light leaks around the polarizing plate is solved. Was not. This light leakage is caused by contraction of the polarizing plate, and there is an example that can be improved by selecting a material for the pressure-sensitive adhesive of the polarizing plate (see Patent Document 1).

JP 2004-516359 A

  However, in the TN mode liquid crystal display device, the contraction of the polarizing plate generates a phase difference in the protective film for the polarizing plate, and there is a large amount of light leakage. Accordingly, an object of the present invention is to provide a liquid crystal display device, particularly a TN liquid crystal display device, having a simple configuration and improved reliability in a harsh environment regardless of the material of the polarizing plate.

In the present invention, for such a problem, this problem is improved by shifting the contraction direction of the polarizing plate and the maximum light leakage direction. That is, this problem can be improved by arranging 90 ° (vertical) or 0 ° (parallel) from the conventional arrangement in which the polarizing plate absorption axis angle in the TN mode intersects with the horizontal direction of the screen at 45 °. It was.
However, in such an arrangement, there is a problem in that the contrast (hereinafter sometimes abbreviated as “CR”) changes when the polar angle to be observed is different, that is, the left and right asymmetry of the CR viewing angle. Sometimes. The inventors of the present invention have further studied and found a configuration that can solve the above problem.
That is, the invention specific matters of the present invention are as follows.

[1]
A pair of substrates having electrodes arranged at least on one side, a liquid crystal layer containing liquid crystal molecules whose orientation is controlled by the alignment axes of the opposing surfaces of the pair of substrates, and the liquid crystal layer interposed therebetween The alignment is controlled by an alignment axis between a pair of polarizing plates having a polarizing film and a protective film provided on at least one surface of the polarizing film, and at least one of the liquid crystal layer and the pair of polarizing films. At least one optically anisotropic layer containing a liquid crystalline compound fixed in the alignment state, and the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or perpendicular to each other. At least one of the orientation axes and at least one orientation axis of the optically anisotropic layer intersect, and the intersection angle is 10 to 35 °.
[2]
The angle formed by the orientation axes of the pair of upper and lower optically anisotropic layers is 80 to 100 °, wherein the liquid crystal display device according to [1].
[3]
The liquid crystal display device according to [1] or [2], wherein the liquid crystal compound is a discotic liquid crystal compound.
[4]
The liquid crystal display device according to any one of [1] to [3], wherein the liquid crystal layer is a TN mode.
[5]
The liquid crystal display device according to [4], wherein the twist angle of the liquid crystal layer is 80 to 100 °.
[6]
[5] The liquid crystal display device according to [5], wherein an angle formed between the orientation axis of the substrate and the horizontal direction of the screen of the display device is 40 to 50 °.
[7]
An elliptically polarizing plate having at least one optically anisotropic layer and a polarizing film, wherein the absorption axis of the polarizing film and the orientation axis of the optically anisotropic layer intersect, and the intersection angle is 10 to 10. An elliptically polarizing plate, which is 35 ° or 55 to 80 °.

  In the present invention, by making the absorption axis of the polarizing film parallel or perpendicular to the horizontal direction of the screen of the display device, the light leakage at the periphery of the polarizing plate has the same configuration as that of the conventional liquid crystal display device even under severe use environment. It is possible to provide a liquid crystal display device with improved reliability, particularly a TN mode liquid crystal display device, in which no occurrence occurs. In the present invention, the left-right symmetry of the CR viewing angle is reduced by setting the crossing angle between at least one of the orientation axes of the substrate and the orientation axis of at least one layer of the optically anisotropic layer to 10 to 35 °. The above effects can be exhibited.

  Terms used in this specification will be described.

(Retardation, Re, Rth)
In the present invention, the protective film, the optically anisotropic layer has retardation, Re, and Rth, and Re _(λ) is KOBRA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.). Measured by incidence. Rth _(λ) is Re _(λ) , a light having a wavelength of λ nm from the direction inclined by + 40 ° with respect to the film normal direction with the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotation axis). And retardation measured by injecting light having a wavelength of λ nm from a 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 calculates based on the retardation measured in three directions, the assumed 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.

  In the present specification, regarding the angle, “+” means the counterclockwise direction, and “−” means the clockwise direction. Further, when the upper direction of the liquid crystal display device is 12 o'clock and the lower direction is 6 o'clock, the absolute value 0 ° direction in the angular direction means the 3 o'clock direction (right direction of the screen). 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.

  Also, in the present specification, in the description of the arrangement between the axes and directions and the angle of the crossing angle, it is simply “parallel”, “vertical”, “0 °”, “90 °”, “45 °”, etc. without showing the range Means “approximately parallel”, “approximately vertical”, “approximately 0 °”, “approximately 90 °”, and “approximately 45 °”, and is not strict. Some deviation is allowed within the range to achieve each purpose. For example, “parallel” and “0 °” means that the crossing angle is approximately 0 °, and is 0 ° to 10 °, preferably 0 ° to 5 °, more preferably 0 ° to 3 °. “Vertical” “90 °” means that the crossing angle is approximately 90 °, and is 80 ° to 90 °, preferably 85 ° to 90 °, more preferably 87 ° to 90 °. “45 °” means that the crossing angle is approximately 45 °, and is 35 ° to 55 °, preferably 40 ° to 50 °, more preferably 42 ° to 48 °.

Hereinafter, the present invention will be described in detail.
The present invention relates to a pair of substrates having electrodes arranged at least on one side and arranged opposite to each other, a liquid crystal layer containing liquid crystal molecules whose orientation is controlled by the orientation axes of the opposing surfaces of the pair of substrates, and the liquid crystal layer An alignment axis between a pair of polarizing plates disposed between and having a polarizing film and a protective film provided on at least one surface of the polarizing film, and between the liquid crystal layer and at least one of the pair of polarizing films In a liquid crystal display device having at least one optically anisotropic layer containing a liquid crystal compound whose orientation is controlled and fixed in that orientation state, the absorption axis of the polarizing film and the maximum shrinkage direction of the polarizing plate, that is, the polarizing plate By arranging the long side and short side direction of the end (or the horizontal direction of the screen of the display device) to be parallel or vertical, a severe use environment (high temperature and high humidity), for example, temperature 40 ° humidity 90%, temperature 65 ° The light leakage from the periphery of the polarizing plate is improved at a humidity of 80%. Furthermore, by adjusting the arrangement angle relationship between the alignment axis of the liquid crystal cell substrate and the alignment control direction of the optically anisotropic layer, a wide viewing angle characteristic was also satisfied.

  As a result of inventor's diligent study, in the conventional TN mode liquid crystal display device, the light leakage around the polarizing plate is caused by the retardation of the polarizing plate, and the retardation Re and Rth are generated in the polarizing plate protective film due to the photoelastic effect. It was found that the light leakage can be improved by adjusting the alignment angle relationship between the alignment axis of the liquid crystal cell substrate, the alignment control direction of the optically anisotropic layer for optical compensation, and the absorption axis of the polarizing plate.

  In a harsh environment, the polarizing plate contracts. In particular, the shrinkage in the direction parallel to the long and short sides of the screen is maximized. When an elastic force such as shrinkage or elongation is applied to the film used for the polarizing plate, the retardation changes. When the polarizing plate absorption axis intersects the retardation generation direction at 45 °, the light transmission is maximized and is observed as leakage light.

In the present invention, it was found that the liquid crystal layer can improve light leakage particularly in the TN mode.
In the conventional TN mode, the polarizing plate absorption axis intersects with the horizontal direction of the screen, that is, the polarizing plate end long side direction at 45 °. Since the contraction direction of the polarizing plate is parallel to the long side and short side directions of the end portion of the polarizing plate, leakage light is maximized in this arrangement.
Therefore, it has been found that light leakage can be improved in the TN mode by making the polarizing plate absorption axis parallel or perpendicular to the horizontal direction of the screen, that is, the long side direction of the polarizing plate end.
(A configuration in which the polarizing plate absorption axis of the liquid crystal display device is thus parallel or perpendicular to the horizontal direction of the screen, that is, the long side direction of the polarizing plate end may be hereinafter referred to as “0 ° -90 ° pasting”.)

  In the TN mode liquid crystal display device, TFT driving is adopted in order to perform high definition and high contrast high quality display. In TFT driving, gate wiring and signal (or source) wiring are arranged in the horizontal and vertical directions of the screen. Since the polarizing plate shrinkage direction is parallel or perpendicular to this wiring, even if the polarizing plate absorption axis is arranged parallel or perpendicular to this wiring, the maximum shrinking direction of the polarizing plate, that is, the long side and short side of the polarizing plate end Light leakage can be improved by arranging them in parallel or perpendicular to the direction.

Further, in order to obtain a wide viewing angle characteristic in the TN mode liquid crystal display device, the absorption axis of at least one polarizing film of the pair of polarizing plates intersects with the alignment axis of the substrate on the side of at least one polarizing plate at 45 °. Good.
In order to improve light leakage at the periphery of the polarizing plate, it can be improved by making the polarizing plate absorption axis parallel or perpendicular to the horizontal direction of the screen, that is, the long side direction of the polarizing plate end. At this time, by setting the alignment control direction of the TN mode liquid crystal display device, that is, the alignment axis of the substrate of the liquid crystal cell, to 45 °, a substantially symmetric viewing angle characteristic can be obtained.
Even in the conventional TN mode, the orientation control direction is set to 45 ° with respect to the horizontal direction of the screen, and the vertical viewing angle characteristics are asymmetrical, but the left and right viewing angle characteristics are symmetric. However, the polarizing film absorption axis and protective film slow axis of the polarizing plate were also set to 45 °, and light leakage occurred in the periphery of the polarizing plate in a severe use environment.

Next, an embodiment in which the present invention is applied to a TN mode liquid crystal display device will be described with reference to the drawings.
In order to explain the present invention, the operation of the liquid crystal display device shown in FIG. 1, which is a conventional example, will be described first by taking a general TN mode as an example. Here, an example in which TFT (active) driving is performed using nematic liquid crystal having positive dielectric anisotropy as field effect liquid crystal will be described.
The liquid crystal cells 9 to 13 include an upper substrate 9 and a lower substrate 12 and a liquid crystal layer formed of liquid crystal molecules 11 sandwiched between them. An alignment film (not shown) is formed on the surfaces of the substrates 9 and 13 that are in contact with the liquid crystal molecules 11 (hereinafter may be referred to as “inner surfaces”), and by a rubbing process or the like applied on the alignment film, The alignment of the liquid crystal molecules 11 in a state where no voltage is applied or in a state where a voltage is not applied is controlled. Further, on the inner surfaces of the substrates 9 and 12, a transparent electrode (not shown) capable of applying a voltage to the liquid crystal layer made of the liquid crystal molecules 11 is formed.
In the TN mode liquid crystal display device, in a non-driving state in which no driving voltage is applied to the electrodes, the liquid crystal molecules 11 in the liquid crystal cell are aligned substantially parallel to the substrate surface, and the alignment direction is twisted by 90 ° between the upper and lower substrates. ing. In the case of a transmissive display device, the light from the backlight passes through the lower polarizing plate and becomes linearly polarized light. The linearly polarized light propagates along the twisted structure of the liquid crystal layer, passes through the upper polarizing plate as it is by rotating the polarization plane by 90 degrees while maintaining the polarization state, and the display device displays white.
On the other hand, when the applied voltage is increased, the liquid crystal molecules gradually stand in the direction perpendicular to the substrate surface while eliminating the twist. In the TN mode liquid crystal display device in an ideal high voltage application state, the twist of the liquid crystal molecules is almost completely eliminated, and the alignment state stands almost perpendicular to the substrate surface. At this time, the linearly polarized light that has passed through the lower polarizing plate propagates without rotating the polarization plane because the liquid crystal layer does not have a twisted structure, and is incident at an angle perpendicular to the absorption axis of the upper polarizing plate, so that the light is blocked. Black display.
Thus, in the TN mode, the function as a display device is achieved by blocking or transmitting polarized light. In general, as a numerical value representing display quality, a ratio between white display luminance and black display luminance is defined and used as a contrast ratio. The higher the contrast ratio, the higher the quality of the display device, and in order to increase the contrast, it is important to maintain the polarization state in the liquid crystal display device and pass through.

An example of a TN mode liquid crystal cell configuration is shown below. A liquid crystal cell is formed by rubbing and aligning liquid crystals having a positive dielectric anisotropy between the upper and lower substrates 9 and 12 and a refractive index anisotropy of Δn = 0.0854 (589 nm, 20 ° C.) and Δε = + 8.5. Make it. The alignment control of the liquid crystal layer is controlled by an alignment film and rubbing. A director indicating the alignment direction of the liquid crystal molecules, that is, a so-called tilt angle is preferably set in a range of about 0.1 to 10 °, and is set to 3 ° here. The rubbing direction is applied in a direction perpendicular to the upper and lower substrates, and the tilt angle can be controlled by the strength and the number of rubbing times. The alignment film is formed by applying and baking a polyimide film. The magnitude of the twist angle of the liquid crystal layer is determined by the crossing angle of the upper and lower substrates in the rubbing direction and the chiral agent added to the liquid crystal material. Here, a chiral agent having a pitch of about 60 μm is added so that the twist angle is approximately 90 °. The thickness d of the liquid crystal layer is set to 5 μm.
Further, the liquid crystal material LC is not particularly limited as long as it is a nematic liquid crystal. As the dielectric anisotropy Δε is larger, the driving voltage can be reduced. When the refractive index anisotropy Δn is small, the thickness (gap) of the liquid crystal layer can be increased, the liquid crystal sealing time can be shortened, and the gap variation can be reduced. In addition, a larger Δn can reduce the cell gap and enable high-speed response. In general, Δn is set between 0.04 and 0.28, the cell gap is set between 1 and 10 μm, and the product of Δn and d is adjusted so as to be between 0.25 and 0.55 μm.

  The absorption axis 4 of the upper polarizing plate and the absorption axis 19 of the lower polarizing plate are laminated orthogonally, and the absorption axis 4 of the upper polarizing plate and the rubbing direction (orientation axis) 10 of the upper substrate 9 of the liquid crystal cell are parallel to each other. Lamination is performed such that the absorption axis 19 of the side polarizing plate and the rubbing direction (alignment axis) 13 of the lower substrate 12 of the liquid crystal cell are parallel to each other. Transparent electrodes (not shown) are formed inside the alignment films of the upper substrate 9 and the lower substrate 12, but in a non-driving state where no driving voltage is applied to the electrodes, the liquid crystal molecules 11 in the liquid crystal cell As a result, the polarization state of light passing through the liquid crystal panel is propagated along the twisted structure of the liquid crystal molecules, and the polarization plane is rotated by 90 ° and emitted. That is, the liquid crystal display device realizes white display in the non-driven state. On the other hand, in the driving state, the liquid crystal molecules are aligned in a direction that forms an angle with respect to the substrate surface, and the light that has passed through the lower polarizing plate is transferred to a letter such as a liquid crystal layer by the optical anisotropic layers 14 and 7. The foundation is canceled out, passes through the liquid crystal layer 11 while maintaining the polarization state, and is blocked by the polarizing film 3. In other words, an ideal black display can be obtained in the driving state in the liquid crystal display device.

  The protective films 5 and 16 on the side near the liquid crystal cell of the upper and lower polarizing plates may also serve as a support for the optically anisotropic layers 7 and 14, and the upper polarizing plate and the lower polarizing plate are optically different. It may be incorporated in the liquid crystal display device as a structure integrally laminated with the isotropic layers 7 and 14. In the liquid crystal display device of the present invention, the transparent support of the optical compensation sheet is also used as a protective film on one side of the polarizing film, that is, a transparent protective film, a polarizing film, and a transparent protective film (also used as a transparent support). And an integrated elliptically polarizing plate laminated in the order of the optically anisotropic layer. Since this integrated elliptical polarizing plate includes an optically anisotropic layer having optical compensation ability, the liquid crystal display device can be accurately optically compensated with a simple structure by using the integrated elliptical polarizing plate. . In the liquid crystal display device, the transparent protective film, the polarizing film, the transparent support, and the optically anisotropic layer are preferably laminated in this order from the outside of the device (the side far from the liquid crystal cell).

  1 shows a mode of a TN mode liquid crystal display device, the liquid crystal display device of the present invention is not only a TN mode but also a mode of VA mode, IPS mode, OCB mode, and ECB mode. Also good. Further, in a liquid crystal display device of each display mode, when a structure called multi-domain in which one pixel is divided into a plurality of regions, the viewing angle characteristics in the vertical and horizontal directions are averaged, and the display quality is improved.

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 may be disposed on the observation side, and reflected on the back surface of the liquid crystal cell or the inner surface of the lower substrate of the liquid crystal cell. Install the membrane. Of course, it is also possible to provide a front light using the light source on the liquid crystal cell observation side. Further, the liquid crystal display device of the present invention may be a transflective type in which a reflective portion and a transmissive 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 and diffusion pattern for giving the light source an in-plane distribution. 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 a three-terminal or two-terminal anti-conductor element such as TFT or MIM. Of course, an embodiment applied to a passive matrix liquid crystal display device represented by STN type called time-division driving is also effective.

  As described above, the occurrence of light leakage can be suppressed by adopting 0 ° -90 ° pasting for the arrangement of the polarizing plates. However, when the optically anisotropic layer of the liquid crystal layer is disposed as in the conventional case, there arises a problem that CR changes when the polar angle to be observed is different on the left and right sides, that is, left and right asymmetry.

The inventors of the present invention have further studied and found a configuration of a liquid crystal display device that can solve the above problem.
That is, the present invention employs 0 ° -90 ° pasting, and at least one of the orientation axes of the substrate intersects with at least one orientation axis of the optically anisotropic layer, and the intersection angle is 10 to 35 °. It is the structure characterized by being.

  In the configuration of the liquid crystal display device, it is more preferable that the angle formed by the orientation axis of the substrate and the horizontal direction of the screen of the display device is 40 to 50 °.

In order to obtain a liquid crystal display device having such a configuration, an elliptically polarizing plate having the following configuration may be used.
That is, an elliptically polarizing plate having at least one optically anisotropic layer and a polarizing film, wherein the crossing angle between the absorption axis of the polarizing film and the orientation axis of the optically anisotropic layer is 10 to 35 ° or 55 to 80. It is an elliptically polarizing plate that is °.

  With the above configuration, the CR viewing angle can be enlarged and the left-right asymmetry can be improved even when pasting at 0 ° -90 °.

FIG. 2 shows an example of the present invention. This example is an example for explaining the effect of the present invention, and the present invention is not limited to this.
The absorption axes 4 and 19 of the polarizing films 3 and 18 in FIG. 2 are 0 ° and 90 °, that is, up and down and left and right with respect to the horizontal direction of the display screen. In FIG. 2, the absorption axis 4 of the upper polarizing film 3 is 90 °, and the absorption axis 19 of the lower polarizing film 18 is 0 °.
Further, the alignment control directions (alignment axes) 8 and 15 of the optically anisotropic layers 7 and 14 intersect with the alignment control directions (alignment axes) 10 and 12 of the upper and lower substrates of the liquid crystal layer 11.

FIGS. 3A, 3B, and 3C show the liquid crystal layer 11 and the upper and lower optically anisotropic layers 7 and 14 of FIG. 2 viewed from the display surface side.
The alignment control direction 8 on the support side of the upper optically anisotropic layer 7 and the upper alignment control direction 10 of the liquid crystal layer are arranged so as to be oriented as shown in FIG.
Similarly, the alignment control direction 15 on the support side of the lower optical anisotropic layer 14 and the lower alignment control direction 12 of the liquid crystal layer are arranged so as to be oriented as shown in FIG.
At this time, the crossing angle between the alignment axis of the optically anisotropic layer and the alignment axis of the substrate of the liquid crystal layer is defined as θ [°]. This θ is preferably 10 to 35 °, more preferably 13 to 32 °, and still more preferably 15 to 30 °.
FIG. 3C shows the upper and lower sides of the liquid crystal layer superimposed. An angle formed by the orientation control directions (orientation axes) 8 and 15 of the pair of upper and lower optically anisotropic layers 7 and 14 is defined as φ [°]. This φ is preferably 80 to 100 °, more preferably 85 to 95 °, and still more preferably about 90 °.

In order to widen the CR viewing angle, the thickness of the optically anisotropic layer is d [μm], the average tilt angle of the compound in the optically anisotropic layer is β [°], When the in-plane retardation is Q [nm], the following formula 1.5 ≦ d ≦ 2.5
20 ≦ β ≦ 50
20 ≦ Q ≦ 60
It is preferable to satisfy.

The d is more preferably 1.6 ≦ d ≦ 2.2, and more preferably 1.7 ≦ d ≦ 2.0.
The β is more preferably 25 ≦ β ≦ 45, and further preferably 30 ≦ β ≦ 40.
The Q is more preferably 25 ≦ Q ≦ 55, and further preferably 30 ≦ Q ≦ 50.

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. And 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]
An example of the optical compensation sheet that can be used in the present invention includes an optically transparent support, and an optically anisotropic layer formed from a liquid crystal 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 is −50 ° to 50 ° with respect to the alignment control direction (for example, the rubbing axis) 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 that are likely to exhibit birefringence have their birefringence controlled by modification of molecules as described in International Publication No. 00/26705 pamphlet. 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. Cellulose acetate is particularly preferred. 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 polymer film retardation value varies depending on the liquid crystal cell in which the optical compensation sheet is used and the method of use thereof, the Re retardation value is preferably 0 to 200 nm, and the Rth retardation value is 70 to 400 nm. A range is preferred. When two optically anisotropic layers are used in the liquid crystal display device, the Rth retardation value of the polymer film is preferably in the range of 70 to 250 nm. When one optically anisotropic layer is used in the liquid crystal display device, the Rth retardation value 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 generally used, but a retardation increasing agent for adjusting the optical anisotropy is optionally added. In order to adjust the retardation of the cellulose acylate film, an aromatic compound having at least two aromatic rings is preferably used as a retardation increasing agent. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Examples thereof include compounds described in European Patent Application Publication No. 91656, JP-A 2000-1111914, 2000-275434, and the like.

Furthermore, the hygroscopic expansion coefficient of the cellulose acetate film used in the optical compensation sheet of the present invention is preferably 30 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is preferably 15 × 10 ⁻⁵ /% RH or less, and more preferably 10 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is preferably small, but usually it is 1.0 × 10 ⁻⁵ /% RH or more. The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed at a constant temperature. By adjusting the hygroscopic expansion coefficient, it is possible to prevent a frame-like transmittance increase (light leakage due to distortion) while maintaining the optical compensation function of the optical compensation sheet.
The method for measuring the hygroscopic expansion coefficient is shown below. 5 mm wide from the produced polymer film. A sample having a length of 20 mm was cut out, one end was fixed, and the sample was hung in an atmosphere of 25 ° C. and 20% RH (R ₀ ). A weight of 0.5 g was hung from the other end and left for 10 minutes to measure the length (L ₀ ). Next, with the temperature kept at 25 ° C., the humidity was set to 80% RH (R ₁ ), and the length (L ₁ ) was measured. The hygroscopic expansion coefficient was calculated by the following equation. The measurement was performed 10 samples for the same sample, and the average value was adopted.
Hygroscopic expansion coefficient [/% RH] = {(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 kind of cellulose acylate solution may be cast as a single layer, or two or more kinds of cellulose acylate solutions may be cast simultaneously and / or sequentially.
As a method of co-casting a plurality of cellulose acylate solutions of two or more layers as described above, for example, a solution containing cellulose acylate from a plurality of casting openings provided at intervals in the traveling direction of the support. A method of casting and laminating each (for example, a method described in JP-A-11-198285) A method of casting a cellulose acylate solution from two casting ports (a method described in JP-A-6-134933) A method of wrapping a flow of a high-viscosity cellulose acylate solution with a low-viscosity cellulose acylate solution and simultaneously extruding the high- and low-viscosity cellulose acylate solution (method described in JP-A-56-162617), etc. Can be mentioned. The present invention is not limited to these. The manufacturing process of these solvent casting methods is described in detail on pages 22 to 30 of the above-mentioned public technical number 2001-1745, and includes dissolution, casting (including co-casting), metal support, drying, It is classified as peeling or stretching.
The thickness of the film (support) of the present invention is preferably 15 to 120 μm, 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, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

  The alkali saponification treatment may be either immersion in a saponification solution or application of a saponification solution, but a coating method is preferred. Examples of the coating method include a dip coating method, a curtain coating method, 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 the surface treatment, in addition to the surface treatment, a single undercoat layer (described in JP-A-7-333433) or a single resin layer such as gelatin containing both hydrophobic groups and hydrophilic groups is applied. A layer that adheres well to the polymer film (hereinafter abbreviated as the first undercoat layer) is provided as the first layer method, and a hydrophilic resin layer (hereinafter referred to as gelatin) that adheres well to the alignment film as the second layer thereon. The contents of a so-called multilayer method (for example, described in JP-A No. 11-248940) is applied.

《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 possible to produce the polarizing plate of the present invention by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizer.

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

  The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules. In the present invention, in addition to the function of aligning liquid crystalline molecules, a 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 is determined according to the type of liquid crystal molecule and the required alignment state. For example, the modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, fluorine atoms 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. Specific examples include those described in paragraphs [0080] to [0100] in JP-A-2000-155216.

  Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent. Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole, and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [024] in JP-A-2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

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

  The alignment film can be basically formed by applying the polymer on the transparent support containing the alignment film forming material and the crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be 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 is provided on the transparent support or the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.

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

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

<< 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 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.

  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 of an axis projected on the support surface of the long axis 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. Is preferred. Moreover, the hybrid orientation described later in which the angle (inclination angle) formed by the disk surface and the layer plane changes in the depth direction is preferable.

《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 disk surface of the discotic liquid crystalline molecule and the surface of the polarizing film increases or decreases in the depth direction of the optically anisotropic layer and with an increase in the distance from the surface of the polarizing film. 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 discotic liquid crystalline molecules on the polarizing film side can be generally adjusted by selecting a discotic liquid crystalline molecule or an alignment film material, or by selecting a rubbing treatment method. In addition, the disc surface direction of the surface side (air side) discotic liquid crystalline molecules can be generally adjusted by selecting the discotic liquid crystalline molecules or the type of additive used together with the discotic liquid crystalline molecules. Examples of the additive used together with the discotic liquid crystalline molecule include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the orientation direction of the major axis can also be adjusted by selecting liquid crystalline molecules and additives as described above.

<< Other additives in optically anisotropic layer >>
Along with the liquid crystal molecules, a plasticizer, a surfactant, a polymerizable monomer, etc. 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 liquid crystal molecules have compatibility with the liquid crystal molecules and can change the tilt angle of the liquid crystal molecules or do 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 molecule is preferably capable of changing the tilt angle of the discotic liquid crystalline molecule.
A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include those described in paragraph [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and preferably in the range of 0.1 to 8% by mass with respect to the liquid crystal molecule so as not to inhibit the alignment of the liquid crystal molecules. It is more preferable. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline molecules is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

<< 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 polymerization initiator described later and optional components on the alignment film.

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

  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 aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules. The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  A protective layer may be provided on the optically anisotropic layer.

《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. The elliptically polarizing plate is preferably molded into a shape substantially the same as that of the pair of substrates constituting the liquid crystal cell so that it can be incorporated into a 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). In the present invention, the alignment axis of the substrate of the liquid crystal cell, the absorption axis of the linearly polarizing film, and / or the alignment axis of the optically anisotropic layer are adjusted to a specific angle.

  The elliptically polarizing plate can be produced by laminating the optical compensation sheet and a linearly polarizing film (hereinafter simply referred to as “linearly polarizing film” when referred to as “polarizing film”). The optical compensation sheet 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. Currently, commercially available polarizers are made by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.

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

  The binder of the polarizing film may be cross-linked. As the crosslinked binder, a polymer that can be crosslinked per se can be used. A polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally carried out by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. Since it is 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.

  As the binder of the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Examples of the polymer include the same polymers as those described for the alignment film. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  The addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the wet heat resistance of the polarizing film are improved.

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

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

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

  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 °.

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 present invention will be described more specifically with reference to the following reference examples and examples. The materials, reagents, substance amounts and ratios, operations, and the like shown in the following reference examples and examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

[Reference Example 1]
A liquid crystal display device having the configuration shown in FIG. 4 was produced. That is, from the observation direction (top) to the upper (elliptical) polarizing plate (protective film 1, polarizing film 3, protective film 5 (also serving as an optical compensation sheet support), optical anisotropic layer 7), liquid crystal cell (upper substrate 9) , Liquid crystal layer 11, lower substrate 12), lower (elliptical) polarizing plate (optical anisotropic layer 14, protective film 16 (also serving as an optical compensation sheet support), polarizing film 18, protective film 20). Further, a backlight (not shown) using a cold cathode fluorescent lamp was disposed below the lower polarizing plate.
Below, the manufacturing method of each used member is demonstrated.

≪Production of liquid crystal cell≫
The liquid crystal cell has a cell gap (d) of 4 μm, a liquid crystal material having a positive dielectric constant anisotropic layer is enclosed between the substrates by drop injection, and Δn · d of the liquid crystal layer 11 is 410 nm (Δn is a value of the liquid crystal material). Refractive index anisotropy). In addition, the rubbing direction (alignment axis) 10 of the upper (observer side) substrate 9 of the liquid crystal cell is 90 °, the rubbing direction (alignment axis) 13 of the lower (backlight side) substrate 12 is 0 °, and the twist angle is The angle was 90 °. In this way, a TN mode liquid crystal cell was produced.

<< Production of optical compensation sheet >>
<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, and the residual solvent amount was 0.3% by mass. A cellulose acetate film (thickness: 80 μm) was prepared. With respect to the produced cellulose acetate film (transparent support, transparent protective film), Re retardation value and Rth retardation value at a wavelength of 546 nm were measured. 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 aligned in a direction parallel to the in-plane slow axis (parallel to the casting direction) of the cellulose acetate film (thus controlling the orientation of the optically anisotropic layer). The direction (rubbing axis) is parallel to the slow axis of the cellulose acetate film.
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, Eastman Chemical Co., Ltd.) 2.0 g, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co., Ltd.) 0.5 g, photopolymerization initiator (Irgacure 907, Ciba Geigy Co.) 3.0 g, sensitization Coating agent (Kayacure DETX, Nippon Kayaku Co., Ltd.) 1.0g, fluoroaliphatic group-containing copolymer (Megafac F780 Dainippon Ink Co., Ltd.) 1.3g dissolved in 207g methyl ethyl ketone The liquid 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 liquid crystalline 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 could not be detected even when viewed from the front and the direction inclined to 60 ° from the normal.

≪ (Ellipse) Production of Polarizing Plate≫
A polarizing film was prepared by adsorbing iodine to the stretched polyvinyl alcohol film, and the prepared 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 are arranged in parallel (therefore, the absorption axis of the polarizing film and the orientation axis of the optically anisotropic layer) (It is parallel to the rubbing axis.) The polarizing plate was cut out so that the long side or the short side was parallel to the slow axis of the support. Thus, an elliptically polarizing plate was produced.

≪Production of liquid crystal display device≫
Observe the produced elliptical polarizing plate on the produced TN cell with an adhesive so that the optical compensation sheet is on the liquid crystal cell side so that the absorption axis of the polarizing film is perpendicular and parallel to the horizontal direction of the screen of the display device. One piece was pasted on the person side and the backlight side. At this time, a liquid crystal display device was produced so that the absorption axis of the polarizing film of the polarizing plate was parallel to the alignment axis (rubbing direction) of the substrate of the liquid crystal cell facing each other.
That is, in this reference example, the absorption axis 4 of the upper polarizing plate polarizing film 3, the slow axes 2 and 6 of the upper polarizing plate protective films 1 and 5 are 90 °, the absorption axis 19 of the lower polarizing plate polarizing film 18, The slow axes 17 and 21 of the side polarizing plate protective films 16 and 20 were set to 0 °. The orientation control direction 8 of the upper optical anisotropic layer 7 was set to 270 °, and the orientation control direction 15 of the lower optical anisotropic layer 14 was set to 180 °.

<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 with 1.5 V white display and 5 V black display was set. The measuring device (EZ-Contrast 160D, manufactured by ELDIM) was used to measure the contrast ratio, which is the transmittance ratio (white display / black display). A front contrast ratio of 1000 to 1 was obtained. Further, after storing in an environmental test room at 40 ° 80% for 24 hours and leaving at room temperature for 1 hour, the luminance difference during black display between the center of the panel and the center of the long side of the polarizing plate was measured to find 0.1 cd / m ^2. Met. Visual observation revealed no light leakage in the periphery of the polarizing plate. The viewing angle with a contrast ratio of 10 or more in the left-right direction was 80 ° on the left and 60 ° on the right. The color tone of white display at 60 ° diagonally was Luv chromaticity coordinates, v ′ was 0.48, and the front transmittance during white display was 30%.

[Reference Example 2]
A liquid crystal display device having the configuration shown in FIG. 5 was produced. The alignment control direction (rubbing direction) 10 of the upper substrate 9 of the liquid crystal cell is 45 ° counterclockwise from the left-right direction, the alignment control direction (rubbing direction) 13 of the lower substrate 12 is also −45 °, and the upper polarizing plate polarization. The absorption axis 4 of the film 3, the slow axes 2 and 6 of the upper polarizing plate protective films 1 and 5 are 0 °, the absorption axis 19 of the lower polarizing plate polarizing film 18, and the slow phases of the lower polarizing plate protective films 16 and 20. The axes 17 and 21 are set to 90 °, the orientation control direction 8 of the upper optical anisotropic layer 7 is set to 180 °, the orientation control direction 15 of the lower optical anisotropic layer 14 is set to 90 °, and other configurations are carried out. Same as Example 1.
When stored in a 40 ° 80% environmental test room for 24 hours and left at room temperature for 1 hour, the difference in luminance at the time of black display between the center of the panel and the center of the long side of the polarizing plate was measured and found to be 0.1 cd / m ² . there were. Visual observation revealed no light leakage in the periphery of the polarizing plate. The viewing angle with a contrast ratio of 10 or more in the left-right direction was 80 ° on the left and 70 ° on the right.

[Reference Example 3]
A liquid crystal display device having the structure shown in FIG. 6 was produced. In Reference Example 2, the orientation control direction (rubbing direction) 8 of the upper optical anisotropic layer 7 is 45 ° counterclockwise from the left-right direction, and the orientation control direction 15 of the lower optical anisotropic layer 14 is also −45 °. Other configurations were the same as those in Reference Example 2.
When stored in a 40 ° 80% environmental test room for 24 hours and left at room temperature for 1 hour, the difference in luminance at the time of black display between the center of the panel and the center of the long side of the polarizing plate was measured and found to be 0.1 cd / m ² . there were. Visual observation revealed no light leakage in the periphery of the polarizing plate. The viewing angle with a contrast ratio of 10 or more in the left-right direction was 80 ° on the left and 75 ° on the right.

[Reference Example 4]
A liquid crystal display device having the structure shown in FIG. 7 was produced. In Reference Example 1, the lower optically anisotropic layer 14 was omitted, and other configurations were the same as Reference 1.
When stored in a 40 ° 80% environmental test room for 24 hours and left at room temperature for 1 hour, the difference in luminance at the time of black display between the center of the panel and the center of the long side of the polarizing plate was measured and found to be 0.1 cd / m ² . there were. Visual observation revealed no light leakage in the periphery of the polarizing plate. The viewing angle with a contrast ratio of 10 or more in the left-right direction was 60 ° on the left and 60 ° on the right.

[Comparative Reference Example 1]
A liquid crystal display device having the configuration shown in FIG. 1 was produced. In Reference Example 1, all angles were rotated counterclockwise by −45 °, and other configurations were the same as Reference Example 1.
When stored in a 40 ° 80% environmental test room for 24 hours and left at room temperature for 1 hour, the luminance difference during black display between the center of the panel and the center of the long side of the polarizing plate was measured and found to be 0.5 cd / m ² . there were. Visual observation revealed light leakage on the arc at the long and short sides of the periphery of the polarizing plate. The viewing angle with a contrast ratio of 10 or more in the left-right direction was 80 ° on the left and 80 ° on the right.

<< Examples and Comparative Examples >>
An optical simulation was performed on the liquid crystal display device configured as shown in FIGS. 1 and 2, and the effect was confirmed. For the optical calculation, LCD Master Ver 6.11 manufactured by Shintech Co., Ltd. was used. The liquid crystal cell, electrode, substrate, polarizing plate, etc. used heretofore have been used for liquid crystal displays. As the liquid crystal material, ZLI-4792 attached to the LCD Master was used. The liquid crystal cell was a TN mode, and the twist angle was 90 °. The alignment direction on the backlight side was 315 °, and the alignment direction on the display surface side was 45 °. A liquid crystal material having a positive dielectric anisotropy and a retardation of the liquid crystal (that is, the product Δn · d _LC of the thickness d _LC [μm] of the liquid crystal layer and the refractive index anisotropy Δn) was set to 400 nm. The liquid crystal applied voltage during white display was 1.8 V, and the liquid crystal applied voltage during black display was 5.6 V. G1220DU attached to LCD Master was used for the polarizing film. A BACKLIGHT light source attached to the LCD Master was used as the light source. In this manner, the optical characteristics of the following comparative examples and examples were obtained using the liquid crystal display device having the configuration shown in FIGS. 1 and 2 as a model.

[Comparative Example 1]
First, for comparison with the present invention, optical characteristics of a liquid crystal display device having a conventional configuration and specification (the crossing angle θ between the alignment axis of the substrate and the alignment axis of the optically anisotropic layer is 0 °) are shown. Calculated by LCD Master.
The absorption axis angle of the polarizing plate is −45 ° on the backlight side and + 45 ° on the display surface side. The orientation control direction of the optically anisotropic layer is 315 ° on the backlight side and 225 ° on the display surface side.
At this time, the CR viewing angle was 80 ° on both the left and right sides, and the left-right luminance difference was 0 (zero) [cd / m ² ] at the polar angle of 60 ° during black display.
Further, the actual measurement value of the light leakage amount (luminance difference between the screen center and the edge during black display) in this configuration was 0.5 [cd / m ² ].

[Comparative Example 2]
Next, the liquid crystal layer is arranged in the same manner as before, and a liquid crystal display device having a configuration / specification in which the alignment control direction of the polarizing film absorption axis and the optically anisotropic layer is rotated by + 45 ° (the alignment axis of the substrate and the optical anisotropic direction The optical property was calculated by LCD Master for the crossing angle θ with the orientation axis of the conductive layer was 45 °.
The absorption axis angle of the polarizing plate is 0 ° on the backlight side and 90 ° on the display surface side, and the orientation control direction of the optically anisotropic layer is 0 ° on the backlight side and 270 ° on the display surface side.
At this time, the CR viewing angle was 46 ° to the left and 57 ° to the left and left and right asymmetric, and the luminance difference between the left and right at the polar angle of 60 ° during black display was 0.0406 [cd / m ² ].
In addition, the actually measured value of the light leakage amount in this configuration was 0.1 [cd / m ² ].

[Example 1]
The liquid crystal layer is arranged in the same manner as in the prior art, and the liquid crystal display device has a configuration and specifications in which the polarizing film absorption axis is rotated by + 45 ° and the alignment control direction of the optical anisotropic layer is rotated by + 20 ° (the alignment axis of the substrate and the optical axis). The optical property was calculated by LCD Master for the angle of intersection θ with the orientation axis of the anisotropic layer was 20 °.
The absorption axis angle of the polarizing plate is 0 ° on the backlight side and 90 ° on the display surface side, and the orientation control direction of the optically anisotropic layer is 335 ° on the backlight side and 245 ° on the display surface side.
At this time, the CR viewing angle was 80 ° to the left and 80 ° to the left and was almost symmetrical, and the luminance difference between the left and right at the polar angle of 60 ° during black display was 0.0035 [cd / m ² ]. This is a small value as compared with Comparative Example 2.
The light leakage amount in this configuration is considered to be equivalent to 0.1 [cd / m ² ] in Comparative Example 2.
[Example 2]
The liquid crystal layer is arranged in the same manner as in the prior art, and the liquid crystal display device has a configuration and specifications in which the polarizing film absorption axis is rotated by + 45 ° and the orientation control direction of the optically anisotropic layer is rotated by + 15 ° (the alignment axis of the substrate and the optical axis). The optical property was calculated by LCD Master for the intersection angle θ with the orientation axis of the anisotropic layer was 15 °.
The absorption axis angle of the polarizing plate is 0 ° on the backlight side and 90 ° on the display surface side, and the orientation control direction of the optically anisotropic layer is 330 ° on the backlight side and 240 ° on the display surface side.
At this time, the CR viewing angle was 80 ° to the left and 80 ° to the right and was almost symmetrical, and the luminance difference between the left and right at the polar angle of 60 ° during black display was 0.0028 [cd / m ² ]. This is a small value as compared with Comparative Example 2.
The light leakage amount in this configuration is considered to be equivalent to 0.1 [cd / m ² ] in Comparative Example 2.

[Summary]
The results are summarized in Table 1. From these, it can be seen that the example satisfying the claims has a reduced light leakage and improved left-right symmetry of the CR viewing angle compared to the comparative example.

It is the schematic which shows an example of the conventional liquid crystal display device. It is the schematic which shows an example of the liquid crystal display device of this invention. It is the figure which looked at the liquid crystal layer 11 and the up-and-down optical anisotropic layers 7 and 14 of the liquid crystal display device of this invention from the display surface side. It is the schematic which shows an example of a structure of the liquid crystal display device used as the reference of this invention. It is the schematic which shows an example of a structure of the liquid crystal display device used as the reference of this invention. It is the schematic which shows an example of a structure of the liquid crystal display device used as the reference of this invention. It is the schematic which shows an example of a structure of the liquid crystal display device used as the reference of this invention.

Explanation of symbols

1 Upper polarizing plate outer protective film 2 Upper polarizing plate outer protective film slow axis 3 Upper polarizing plate polarizing film 4 Absorption axis of upper polarizing plate polarizing film 5 Upper polarizing plate liquid crystal cell side protective film (optical compensation sheet support)
6 Upper polarizing plate liquid crystal cell side protective film slow axis 7 Upper optical anisotropic layer 8 Orientation control direction (alignment axis) of upper optical anisotropic layer
9 Liquid crystal cell upper substrate 10 Upper substrate liquid crystal alignment control direction (alignment axis)
11 Liquid crystal molecules (liquid crystal layer)
12 Liquid crystal cell lower substrate 13 Lower substrate Liquid crystal alignment control direction (alignment axis)
14 Lower optical anisotropic layer 15 Orientation control direction (alignment axis) of lower optical anisotropic layer
16 Lower polarizing plate Liquid crystal cell side protective film (Optical compensation sheet support)
17 Lower polarizing plate liquid crystal cell side protective film slow axis 18 Lower polarizing plate polarizing film 19 Absorption axis of lower polarizing plate polarizing film 20 Lower polarizing plate outer protective film 21 Lower polarizing plate outer protective film slow axis θ Crossing angle between the alignment axis of the liquid crystal layer substrate and the alignment axis of the optically anisotropic layer φ Angle formed by the alignment axes of the upper and lower optically anisotropic layers

Claims (7)

  A pair of substrates having electrodes arranged at least on one side, a liquid crystal layer containing liquid crystal molecules whose orientation is controlled by the alignment axes of the opposing surfaces of the pair of substrates, and the liquid crystal layer interposed therebetween The alignment is controlled by an alignment axis between a pair of polarizing plates having a polarizing film and a protective film provided on at least one surface of the polarizing film, and at least one of the liquid crystal layer and the pair of polarizing films. At least one optically anisotropic layer containing a liquid crystalline compound fixed in the alignment state, and the absorption axis of the polarizing film and the horizontal direction of the screen of the display device are parallel or perpendicular to each other. At least one of the orientation axes and at least one orientation axis of the optically anisotropic layer intersect, and the intersection angle is 10 to 35 °.   2. The liquid crystal display device according to claim 1, wherein an angle formed by the orientation axes of the pair of upper and lower optically anisotropic layers is 80 to 100 degrees.   The liquid crystal display device according to claim 1, wherein the liquid crystal compound is a discotic liquid crystal compound.   The liquid crystal display device according to claim 1, wherein the liquid crystal layer is a TN mode.   The liquid crystal display device according to claim 4, wherein a twist angle of the liquid crystal layer is 80 to 100 °.   6. The liquid crystal display device according to claim 5, wherein an angle formed by the orientation axis of the substrate and the horizontal direction of the screen of the display device is 40 to 50 degrees.   An elliptically polarizing plate having at least one optically anisotropic layer and a polarizing film, wherein the absorption axis of the polarizing film and the orientation axis of the optically anisotropic layer intersect, and the intersection angle is 10 to 10. An elliptically polarizing plate, which is 35 ° or 55 to 80 °.

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