JP2003232922A - Polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To laminate a linearly polarizing film having a longitudinal direction on an optical retardation plate having a longitudinal direction in roll-to-roll process in such a manner that the absorption axis of the linearly polarizing film is substantially neither parallel nor perpendicular to the phase lagging axis of the optical retardation plate. <P>SOLUTION: An optical retardation plate having the phase lagging axis present in the direction substantially neither parallel nor perpendicular to the longitudinal direction is used, or a linearly polarizing film having the absorption axis present in the direction substantially neither parallel nor perpendicular to the longitudinal direction is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long film having a linear polarizing film having a longitudinal direction and a retardation plate having a longitudinal direction arranged so that their longitudinal directions are substantially parallel to each other. Of the polarizing plate. The present invention also provides a circularly polarizing plate in which a linear polarizing film and a λ / 4 plate are arranged such that the absorption axis of the linear polarizing film and the slow axis of the λ / 4 plate form an angle of 45 °. Also related to. Furthermore, the present invention comprises a liquid crystal cell in which a nematic liquid crystal exhibiting bend alignment or hybrid alignment is sealed, a circularly polarizing plate, and an optical compensation film, and the alignment vector of the nematic liquid crystal with respect to the substrate is changed by the change of the voltage applied to the liquid crystal cell. It also relates to a liquid crystal display device in which the angle of is changed.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) is a CRT (cat
Compared with hode ray tube), it has excellent features such as thinness, light weight, and low power consumption, and it has come to be widely used in notebook computers, monitors, TVs, PDAs, mobile phones, car navigation systems, video cameras, etc. . The most popular at present is the TN (twisted nematic) mode using twisted nematic liquid crystal, but in this method, in principle, there is a problem in viewing angle characteristics that the display color and contrast change depending on the viewing direction, and There was a problem that the response speed was still insufficient.

US Pat. Nos. 4,583,825 and 54,104.
No. 22 discloses a liquid crystal display device using a bend alignment mode liquid crystal cell in which a rod-shaped liquid crystal is aligned in a substantially opposite direction (symmetrically) in an upper portion and a lower portion of the liquid crystal cell. . Since the rod-shaped liquid crystal molecules are symmetrically aligned in the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function.
Also called Compensatory Bend) mode. This method requires the use of an optical compensation film in order to cancel the retardation on the front side and further widen the viewing angle. As this optical compensation film, a film having an optically anisotropic layer on a transparent support is disclosed in JP-A-6-2141.
16 publication, US Pat. Nos. 5,583,679 and 56467.
No. 03, West German Patent Publication 3911620A1.

In order to further improve the viewing angle of a bend alignment mode liquid crystal display device, it has been studied to use an optical compensation film as in a general liquid crystal mode. JP-A-8-327822 and JP-A-9-278822 -197397 (US Pat. No. 5,805,253), WO96 / 3
No. 7804 (European Patent Application No. 0783128A) and JP-A No. 11-316378 (US Pat. No. 6,064,457) disclose an optical compensation film having an optically anisotropic layer formed of a discotic liquid crystal,
And a liquid crystal display device of bend alignment mode using the same is disclosed. An extremely wide viewing angle can be obtained by using an optical compensation film having an optically anisotropic layer formed of discotic liquid crystal in a bend alignment mode liquid crystal display device.

Furthermore, the 42nd Spring Applied Physics Society (29
a-SZC-20, 1995), the HAN mode (Hybri
d-aligned-nematic mode) Liquid crystal cells have been proposed.
That is, this HAN mode liquid crystal cell utilizes the hybrid alignment above the bend alignment cell. This HA
In the N-mode liquid crystal cell, a biaxially stretched film has been proposed as an optical compensation film. In order to further improve the viewing angle of a HAN-mode liquid crystal display device utilizing this hybrid alignment, an optical system having an optically anisotropic layer formed of discotic liquid crystal is disclosed in Japanese Patent Laid-Open No. 9-21914 and Japanese Patent No. 3118197. A compensation film and a HAN mode liquid crystal display device using the same are described. OCB mode and HAN mode liquid crystal cells
Compared with the conventional liquid crystal mode (TN mode, STN mode), it is characterized by having a wider viewing angle and faster response speed, and is being used in a transmissive type. However, in the future, a reflective type or a semi-transmissive type will be used. Is expected to develop as a liquid crystal display device, but in this case, a λ / 4 plate is essential,
As compared with the transmissive type, there remains a problem in manufacturing that the manufacturing process becomes longer or the yield rate of non-defective products decreases.

[0006]

The object of the present invention is to provide an OC
An object of the present invention is to improve a polarizing plate that can be used in a B-mode transflective liquid crystal display device or a HAN mode reflective liquid crystal display, and to provide a polarizing plate that can be manufactured with a short manufacturing process and a high yield rate.

[0007]

Means for Solving the Problems The present invention includes the following (1) to
The polarizing plate of (4) and the liquid crystal display device of the following (5) to (7) are provided. (1) A linear polarizing film having a longitudinal direction and a retardation plate having a longitudinal direction are arranged such that their longitudinal directions are substantially parallel to each other, and the absorption axis of the linear polarizing film is in the longitudinal direction. On the other hand, a polarizing plate that is substantially parallel to the retardation plate, and the slow axis of the retardation plate exists in a direction that is neither substantially parallel nor perpendicular to the longitudinal direction. (2) The polarizing plate according to (1), wherein the retardation plate is a λ / 4 plate and the slow axis of the retardation plate is substantially 45 ° with respect to the longitudinal direction.

(3) The linear polarizing film having the longitudinal direction and the retardation plate having the longitudinal direction are arranged so that their longitudinal directions are substantially parallel to each other, and the absorption axis of the linear polarizing film is A polarizing plate that is present in a direction that is neither substantially parallel to nor perpendicular to the longitudinal direction, and in which the slow axis of the retardation plate is substantially parallel to the longitudinal direction. (4) The retardation plate is a λ / 4 plate, and the absorption axis of the linear polarizing film is substantially 45 ° with respect to the longitudinal direction (3)
The polarizing plate described in.

(5) A liquid crystal in which a nematic liquid crystal exhibiting bend alignment or hybrid alignment is enclosed between a pair of substrates with transparent electrodes having an alignment film on the surface and at least one polarizing plate. A liquid crystal display device, wherein the polarizing plate is cut from the polarizing plate according to any one of (1) to (4).

(6) An optical compensation film consisting of a transparent support and an optically anisotropic layer in which the orientation of the discotic liquid crystal is fixed is disposed between the liquid crystal cell and the polarizing plate. Re (0 °), Re (40
°) and Re (-40 °) are 35 ± 25n, respectively.
m, 105 ± 55 nm, 35 ± 25 nm, The liquid crystal display device according to (5). Re (0 °), Re
(40 °) and Re (−40 °) are in a plane including the direction and the direction in which the retardation of the optically anisotropic layer takes the minimum value,
Letters of the optical compensation film measured with light having a wavelength of 633 nm from the direction of the normal, the direction inclined by 40 ° in the direction opposite to the direction of the minimum from the normal, and the direction inclined by 40 ° in the direction of the minimum by the normal. Represents the foundation value.

(7) The transparent support of the optical compensation film is
The liquid crystal display device according to (6), which is optically anisotropic and has a Re retardation value in the range of 10 to 70 nm and an Rth retardation value in the range of 70 to 400 nm. The Re retardation value and the Rth retardation value are represented by the following formulas (I) and (II), respectively.
(I) Re = (nx-ny) * d (II) Rth = {(nx + ny) / 2-nz} * d [In the Formula, nx is a slow phase in a transparent support surface. Is the refractive index in the axial direction; ny is the refractive index in the fast axis direction in the plane of the transparent support; nz is the refractive index in the thickness direction of the transparent support; and d is the refractive index of the transparent support. Thickness.]

As used herein, "substantially parallel",
“Substantially perpendicular” or “substantially 45 °” means within ± 5 ° of the exact angle. Therefore, "neither substantially parallel nor perpendicular" means
It means that the angle (narrower angle) is more than 5 ° and less than 85 °.

[0013]

In the polarizing plate according to the present invention, the linear polarizing film and the retardation film can be bonded together by roll-to-roll. Like a circularly polarizing plate, the absorption axis of the linearly polarizing film and the slow axis of the retardation plate (λ / 4 plate for the circularly polarizing plate) are not parallel or perpendicular (45 ° for the circularly polarizing plate). In the case of bonding to the above, in the conventional technique, the chip in which the linear polarizing film was cut and the chip in which the retardation plate was cut were bonded. In the roll-shaped linear polarizing film manufactured by the conventional technology,
The absorption axis is parallel or perpendicular to the longitudinal direction. Similarly, in the roll-shaped retardation plate manufactured by the conventional technique, the slow axis is parallel or perpendicular to the longitudinal direction. Therefore, when a roll-shaped linear polarizing film and a roll-shaped retardation film manufactured by conventional techniques are pasted together by roll-to-roll, the absorption axis of the linear polarizing film and the slow axis of the retardation plate are parallel or perpendicular to each other. However, it cannot be arranged so that it is in a different direction.

According to the research conducted by the present inventor, a retardation plate whose slow axis is neither substantially parallel nor perpendicular to the longitudinal direction, or linearly polarized light whose absorption axis is neither substantially parallel nor perpendicular to the longitudinal direction. It has been found that a membrane can be produced. As a result, the present inventor only needs to stick the linear polarizing film and the retardation plate by roll-to-roll to make the absorption axis of the linear polarizing film and the slow axis of the retardation plate parallel to each other like a circularly polarizing plate. However, we succeeded in manufacturing a polarizing plate that is arranged so that it is not vertical. The method of laminating the linear polarizing film and the retardation plate by roll-to-roll is shorter process, higher yield and lower cost than the method of laminating the linear polarizing film and the retardation plate into chips and then laminating them. Which is a very advantageous manufacturing method. The liquid crystal display device of the bend alignment mode or the hybrid alignment (HAN) mode is a reflective type and has a wide viewing angle and a high-speed response. If the circularly polarizing plates used for them can be manufactured with a short process, high yield and low cost, it can be expected that such liquid crystal display devices will be widely spread in the future.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION [Liquid Crystal Cell] A liquid crystal cell of bend alignment mode and HAN alignment mode is disclosed in Japanese Patent No. 31.
No. 18197 is described in detail. A liquid crystal cell using a liquid crystal having bend alignment (bend alignment cell) is a symmetrical cell, and a liquid crystal display device having this liquid crystal cell has a wide viewing angle. Similarly, a reflective liquid crystal display device using a HAN-aligned liquid crystal also has a wide viewing angle.

A liquid crystal cell generally comprises a substrate having a pair of transparent electrodes on which an alignment film is formed, and a layer of nematic liquid crystal enclosed between the substrates. In the bend alignment cell, a nematic liquid crystal that can be bend aligned in a liquid crystal cell to which a voltage is applied is generally used. The liquid crystal used in the bend alignment liquid crystal cell generally has a positive dielectric anisotropy. And of the alignment vector of the nematic liquid crystal,
The angle with respect to the substrate changes due to changes in the voltage applied to the liquid crystal cell. Generally, the angle of the orientation vector of the nematic liquid crystal with respect to the substrate increases with an increase in the voltage applied to the liquid crystal cell, and the birefringence decreases. An image is obtained by this change in birefringence. In the present specification, the liquid crystal bend orientation means that the orientation vector (that is, the director or the optical axis) of the liquid crystal molecules in the liquid crystal layer is symmetric (line symmetric) with respect to the center line of the liquid crystal layer, and the bend orientation is at least in a region near the substrate. Means having a part. The bend portion refers to a portion where a line formed by the director in a region near the substrate is bent.

That is, the bend orientation of the liquid crystal means that when a voltage is applied to the liquid crystal cell, the director of the liquid crystal molecules in the cell is substantially parallel to the lower substrate in the vicinity of the lower substrate. The angle between the director and the surface of the substrate increases with increasing distance from, and in the region where the distance between the upper substrate and the lower substrate is equal (center line region),
It becomes perpendicular or nearly perpendicular to the substrate surface, and then the director further increases the angle between the director and the substrate surface as the distance from the lower substrate increases, eventually making the director nearly parallel to the upper substrate near the upper substrate. The liquid crystal molecules are aligned so that Near the center line,
The director may be twist-oriented. Further, the directors in the region close to the upper and lower substrates or in the contact region may be tilted from the substrate surface (that is, may have a tilt angle). In the bend-aligned liquid crystal cell, the product of the refractive index anisotropy Δn of the liquid crystal compound and the thickness d of the liquid crystal layer of the liquid crystal cell (Δ
n × d) is 100 in order to achieve both brightness and viewing angle.
Is preferably in the range of 150 to 2000 nm, and is preferably 150
To 1700 nm is more preferable,
Most preferably, it is in the range of 500 to 1500 nm.

The HAN alignment mode is well known in the field of liquid crystal display devices. The HAN alignment cell has a structure in which the lower substrate is arranged at the center line of the bend alignment cell,
The alignment film on the lower substrate is a layer capable of homeotropic alignment of nematic liquid crystals. Examples of such an alignment film include an inorganic vapor deposition film, a surfactant layer, and an organic silane layer. The nematic liquid crystal used in the HAN-aligned cell of the present invention is generally a liquid crystal capable of forming a hybrid alignment by applying a voltage. In the HAN alignment cell, it is preferable that the liquid crystal is aligned substantially vertically on one substrate and the pretilt angle on the other substrate is 0 to 45 °. The product (Δnd) of the refractive index anisotropy (Δn) of the liquid crystal layer and the thickness (d) of the liquid crystal layer is preferably 100 nm to 1000 nm, more preferably 300 to 800 nm. The substrate on the side of vertically aligning the liquid crystal may be the substrate on the reflection plate side or the substrate on the transparent electrode side.

The liquid crystal display device having the bend alignment cell or the HAN alignment cell has a self-compensation director region, but when the display device is viewed from a large angle (especially in the vertical direction), the light transmittance of the black display portion is high. Is increased, resulting in a decrease in contrast. By mounting the optical compensation sheet of the present invention on the cell, the contrast when viewed from the tilt direction can be greatly improved without lowering the contrast when viewed from the front.

[Linear Polarizing Film] The linear polarizing film can be used as a circularly polarizing plate when its absorption axis is bonded to the slow axis of the λ / 4 plate at an angle of 45 °. In order to manufacture a circularly polarizing plate by laminating a linearly polarizing film and a λ / 4 plate with a roll-to-roll method, the absorption axis is 4 in the longitudinal direction of the film.
A combination of a long linear polarizing film inclined at 5 ° and a λ / 4 plate whose slow axis is parallel to the longitudinal direction of the film, or a long linear polarizing film whose absorption axis is parallel to the longitudinal direction of the film and a slow axis are A combination with a λ / 4 plate inclined at 45 ° in the longitudinal direction of the film is preferable.

Several methods have been proposed for inclining the orientation axis of a polymer at a desired angle with respect to the film transport method. For example, in Japanese Unexamined Patent Publication No. 2000-9912, while uniaxially stretching a plastic film horizontally or vertically, the left and right of the stretching direction are stretched at different speeds in a longitudinal or lateral direction different from the stretching direction, and oriented. A method of inclining a shaft with respect to the uniaxial stretching direction, JP-A-3-18
As described in Japanese Patent No. 2701, a pair of left and right film holding points forming an angle of θ with the running direction is provided at both left and right ends of the continuous film, and each pair of points extends in the direction of θ as the film runs. A method for manufacturing a film having a stretching axis at an arbitrary angle θ with respect to the traveling direction of the film by a mechanism that allows the film to travel at both ends of the film within a predetermined traveling section, as described in JP-A-2-113920. The film is stretched in a direction oblique to the length direction of the film by gripping and traveling between two rows of chucks traveling on tenter rails arranged so that the transmission axis is rubbed. There is a long roll-shaped polarizing plate comprising a tilted polarizing plate and a diagonally stretched polymer film obtained by a diagonal stretching method of a polymer film.

It is preferable to use a long-length roll-shaped polarizing plate by the oblique stretching method for producing a linearly polarizing film.
Polyvinyl alcohol (PVA) is mainly used as a material for the linearly polarizing film. This PVA film is stretched and then dyed with iodine or a dichroic dye, or dyed and then stretched, and then a boron compound is added. A linear polarizing film is formed by crosslinking. Moreover, what stretched polyene and dyed similarly can also be used.

Regarding the production of a linear polarizing film whose absorption axis is neither parallel nor perpendicular to the longitudinal direction of the film,
A method for stretching a polymer film for polarizing plate (mainly PVA) in which both ends of a continuously supplied polymer film are held by a holding means, and stretching is performed by applying tension while advancing the holding means in the longitudinal direction of the film, Trajectory L1 of the holding means from the substantial holding start point of one end of the polymer film to the substantial holding release point and the holding means from the substantial holding start point of the other end of the polymer film to the substantial holding release point The distance W between the two substantial holding release points with the locus L2 satisfies the following formula (3), the polymer film is supported, and the volatile content is 5% or more. Then, a method for producing a polymer film for a polarizing plate, which is characterized by shrinking to reduce the volatile content and then winding it into a roll, can be applied.

Formula (3) | L2-L1 |> 0.4W For the linear polarizing film, an optical compensation film described later as a protective film, a retardation plate such as a λ / 4 plate, or a protective film for a normal polarizing plate is used. An optically transparent cellulose triacetate film having a small birefringence used as the above can be used.

[Optical Compensation Film] The optical compensation film is preferably composed of at least a transparent support and an optically anisotropic layer in which the orientation of the discotic liquid crystal is fixed, and Re (0 °) showing its optical anisotropy. , Re (40
°) and Re (-40 °) are 35 ± 25n each
m, 105 ± 55 nm, 35 ± 25 nm. Here, Re (0 °), Re (40 °),
Re (−40 °) is the normal direction in a plane including the direction in which the retardation of the optically anisotropic layer takes the minimum value and the normal direction,
The direction tilted by 40 ° in the direction opposite to the direction of the minimum value from the normal line,
The retardation value of the optical compensation film measured with light having a wavelength of 633 nm from the direction inclined by 40 ° from the normal to the direction of the minimum value of retardation is shown.

[Transparent Support] As the transparent support of the optical compensation film, it is preferable to use a polymer film having a light transmittance of 80% or more. The polymer film is preferably one which is unlikely to exhibit birefringence due to external force. Examples of polymers include cellulose-based polymers and norbornene-based polymers (eg, ARTON, JSR Corporation).
ZEONOR, manufactured by Nippon Zeon Co., Ltd .; ZEONE
X, manufactured by Nippon Zeon Co., Ltd.) and polymethylmethacrylate. Cellulosic polymers are preferred, cellulose esters are more preferred, and lower fatty acid esters of cellulose are even more preferred. The lower fatty acid means a fatty acid having 6 or less carbon atoms. 2 carbon atoms
It is preferably (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). The cellulose ester is preferably cellulose acetate, and examples thereof include diacetyl cellulose and triacetyl cellulose.
Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.

Generally, the second and third positions of cellulose acetate
The hydroxyl groups at the 6- and 6-positions are not evenly distributed in 1/3 of the total substitution degree, and the substitution degree of the 6-position hydroxyl group tends to be small. In the present invention, cellulose acetate 6
It is preferable that the degree of substitution of the hydroxyl group at the position is higher than that at the positions of 2 and 3. The ratio of the substitution degree at the 6-position to the total substitution degree at the 2-position, 3-position, and 6-position is preferably 30% or more and 40% or less, and more preferably 31% or more, Most preferably, it is 32% or more. The substitution degree of the 6-position acyl group of cellulose acetate is preferably 0.88 or more.

The 6-position hydroxyl group has 3 carbon atoms in addition to the acetyl group.
The above-mentioned acyl groups, propionyl group, butyroyl group,
It may be substituted with a valeroyl group, a benzoyl group or an acryloyl group. The substitution degree at each position can be measured by NMR. As cellulose acetate,
Paragraph Nos. 0043 to 00 of JP-A No. 11-5851
44, Synthesis Example 1, Paragraph Nos. 0048 to 0
049, and paragraph number 00.
The cellulose acetate obtained by the synthesis method of Synthesis Example 3 described in Nos. 51 to 0052 can be used.

[Retardation Value of Polymer Film] Re retardation value and Rth retardation value of polymer film are defined by the following formulas (I) and (II), respectively. (I) Re = (nx−ny) × d (II) Rth = {(nx + ny) / 2−nz} × d In the formulas (I) and (II), nx is the slow axis direction in the film plane ( The direction in which the refractive index becomes maximum). In the formulas (I) and (II), ny is the refractive index in the fast axis direction (direction in which the refractive index is minimum) in the film plane. In the formula (II), nz is the refractive index in the thickness direction of the film. In formulas (I) and (II), d
Is the film thickness in nm.

In the present invention, the Re retardation value of the polymer film is preferably 10 to 70 nm, and the Rth retardation value thereof is preferably 70 to 400 nm. The birefringence of the polymer film (Δn:
nx-ny) is preferably 0.00025 to 0.00088. The birefringence index {(nx + ny) / 2-nz} in the thickness direction of the transparent support is 0.0008.
It is preferably from 8 to 0.005.

[Angle of slow axis of polymer film] The angle of the slow axis in the plane of the transparent support is defined by the angle between the slow axis and the reference line with the stretching direction of the polymer film as the reference line (0 °). . Here, when a roll-shaped film is stretched in the width direction, the width direction is used as a reference line, and when stretched in the longitudinal direction, the length direction is used as a reference line. The average value of the slow axis angle is preferably 3 ° or less, more preferably 2 ° or less, and most preferably 1 ° or less. The direction of the average value of the slow axis angle is defined as the average direction of the slow axis. Further, the standard deviation of the slow axis angle is preferably 1.5 ° or less, more preferably 0.8 ° or less, and most preferably 0.4 ° or less.

In a transmission type liquid crystal display device using an optical compensation film, "frame-like display unevenness" may occur in the peripheral portion of the screen after a lapse of time after energization. This unevenness is due to an increase in the transmittance of the peripheral portion of the screen, and is particularly noticeable during black display. In the semi-transmissive liquid crystal display device, heat is generated from the backlight and a temperature distribution is generated in the plane of the liquid crystal cell. The change in the optical characteristics (retardation value, angle of the slow axis) of the optical compensation film due to this temperature distribution is the cause of the "frame-shaped display unevenness". The change in the optical characteristics of the optical compensation film is caused by the elastic deformation of the optical compensation film because the expansion or contraction of the optical compensation film due to the temperature rise is suppressed by the adhesion with the liquid crystal cell or the linear polarizing film.

In order to suppress the above-mentioned "frame-like display unevenness", it is preferable to use a polymer film having a high thermal conductivity as the optical compensation film. As a polymer with high thermal conductivity, cellulose acetate {0.22W /
(M · ° C)}, low-density polyethylene {0.34W / (m
.Degree. C.)}, ABS {0.36 W / (m.degree. C.)}, and polycarbonate {0.19 W / (m.degree. C.)} are preferred. ZEONEX {0.20, which is a cyclic olefin polymer
W / (m ・ ° C), manufactured by Nippon Zeon Co., Ltd.}, ZEONOR
{0.20 W / (m · ° C), manufactured by Nippon Zeon Co., Ltd.}, A
RTON {0.20W / (m ・ ° C), made by JSR Corporation}
Is also preferable.

In consideration of the above optical characteristics and thermal characteristics, the polymer film of the present invention has an acetylation degree of 5
It is preferable to use a cellulose acetate film having a content of 9.0 to 61.5%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. Acetification degree is A
According to the measurement and calculation of the degree of acetylation in STM: D-817-91 (testing method for cellulose acetate, etc.). Also, the viscosity average degree of polymerization (DP) of the polymer film
Is preferably 250 or more, more preferably 290 or more. Also, the polymer film is
Mw / by gel permeation chromatography
It is preferable that the molecular weight distribution of Mn (Mw is a mass average molecular weight and Mn is a number average molecular weight) is narrow. Specific Mw / Mn
The value of is preferably 1.0 to 1.7, more preferably 1.3 to 1.65,
Most preferably, it is 1.4 to 1.6.

[Retardation Raising Agent] In order to adjust the retardation of the polymer film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation raising agent, which has at least two aromatic rings. As the aromatic compound, triphenyltriazines are preferable. As another specific example,
JP-A-2000-111914 and 2000-27.
No. 5434, PCT / JP00 / 02619, and the like. You may use together two or more types of aromatic compounds. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

The retardation increasing agent has a molecular weight of 30.
It is preferably 0 to 800. When a cellulose acetate film is used as the polymer film, the aromatic compound is used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acetate.

[Production of Polymer Film] The production method of the cellulose acetate film which is preferably used as the polymer film is described in JIII Journal of Technical Disclosure (Publication 2001-1745, published on Mar. 15, 2001, Institute of Invention). ing. Other polymer films can be manufactured by the same method.

[Stretching Treatment of Polymer Film] The retardation of the produced polymer film can be adjusted by further stretching treatment. The draw ratio is preferably 3 to 100%. The thickness of the polymer film is preferably 40 to 140 μm, and 70
To 120 μm is more preferable.

By adjusting the conditions of this stretching process, the standard deviation of the angle of the slow axis of the optical compensation film can be reduced. The stretching method is not particularly limited, but an example thereof includes a stretching method using a tenter. When the film produced by the solvent casting method is transversely stretched using a tenter, the standard deviation of the slow axis angle of the film can be reduced by controlling the state of the film after stretching. Specifically, a stretching treatment for adjusting the retardation value is performed using a tenter, and the polymer film immediately after stretching is kept in that state in the vicinity of the glass transition temperature of the film to obtain a standard slow axis angle. The deviation can be reduced. If the temperature of the film during this holding is lower than the glass transition temperature, the standard deviation becomes large. Further, as another example, when the longitudinal stretching is performed between the rolls, the standard deviation of the slow axis can be reduced by increasing the distance between the rolls.

[Surface Treatment of Polymer Film] When the polymer film is used as a transparent protective film for a polarizing plate, it is preferable to treat the surface of the polymer film. As the surface treatment, corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment or ultraviolet irradiation treatment is carried out. It is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment for the polymer film.

[Alignment Film] The alignment film has a function of defining the alignment direction of the discotic liquid crystal of the optically anisotropic layer. The alignment film is formed by rubbing an organic compound (preferably a polymer), obliquely depositing an inorganic compound, forming a layer having microgrooves, or an organic compound (eg, ω-tricosanoic acid) by the Langmuir-Blodgett method (LB film). ,
It can be provided by means such as accumulation of dioctadecylmethyl ammonium chloride, methyl stearyl acid). Furthermore, an alignment film which has an alignment function by applying an electric field, a magnetic field, or light irradiation is also known.

The alignment film is preferably formed by rubbing a polymer. Polyvinyl alcohol is the preferred polymer. Modified polyvinyl alcohol having a hydrophobic group bonded thereto is particularly preferable. Since the hydrophobic group has an affinity with the discotic liquid crystal of the optically anisotropic layer, the discotic liquid crystal can be uniformly aligned by introducing the hydrophobic group into polyvinyl alcohol. The hydrophobic group is attached to the main chain end or side chain of polyvinyl alcohol. The hydrophobic group is preferably an aliphatic group having 6 or more carbon atoms (preferably an alkyl group or an alkenyl group) or an aromatic group. When a hydrophobic group is bonded to the end of the main chain of polyvinyl alcohol, it is preferable to introduce a linking group between the hydrophobic group and the end of the main chain. Examples of the linking group, -S -, - C (CN ) R 1 -, - NR 2 -, - CS
-And combinations thereof. R ₁ and R ₂ are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (preferably having 1 to 6 carbon atoms).
Is an alkyl group).

[0043] When introducing a hydrophobic group in the side chain of the polyvinyl alcohol, a part of polyvinyl alcohol acetyl group vinyl acetate unit (-CO-CH _3), carbon atoms of 7 or more acyl groups (- CO-R ₃₎ to may be replaced. R ₃ is an aliphatic group or aromatic group having 6 or more carbon atoms. Reference can be made to JP-A-9-152509. A commercially available modified polyvinyl alcohol (eg, MP103, MP203, R1130, manufactured by Kuraray Co., Ltd.) may be used.

The saponification degree of the (modified) polyvinyl alcohol used for the orientation film is preferably 80% or more.
The degree of polymerization of the (modified) polyvinyl alcohol is preferably 200 or more. The rubbing treatment is performed by rubbing the surface of the alignment film with paper or cloth in a certain direction several times. It is preferable to use a cloth in which fibers having uniform length and thickness are uniformly flocked. Even if the alignment film is removed after the discotic liquid crystal molecules in the optically anisotropic layer are aligned using the alignment film, the alignment state of the discotic liquid crystal molecules can be maintained. That is, the alignment film is essential in the production of the elliptically polarizing plate for aligning the discotic liquid crystal molecules, but is not essential in the produced optical compensation sheet. When the alignment film is provided between the transparent support and the optically anisotropic layer, it is preferable to further provide an undercoat layer (adhesive layer) between the transparent support and the alignment film.

[Optical anisotropic layer] The optical anisotropic layer is formed of discotic liquid crystal. Discotic liquid crystals generally have optically negative uniaxiality. In the optical compensation film of the present invention, the discotic liquid crystal preferably has an angle formed by the disc surface and the transparent support surface that changes in the depth direction of the optically anisotropic layer (hybrid alignment). The optical anisotropic layer does not have a direction in which the retardation value becomes 0 or an optical axis. The optically anisotropic layer aligns the discotic liquid crystal by the above alignment film,
It is preferably formed by fixing the discotic liquid crystal in the aligned state. The discotic liquid crystal is preferably fixed by a polymerization reaction. The thickness of the optically anisotropic layer is preferably 0.5 to 100 μm, more preferably 0.5 to 30 μm.

Regarding discotic liquid crystals, various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst.,
vol. 71, page 111 (1981); Chemical Society of Japan, Quarterly Chemistry Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. C.
hem. Comm., page 1794 (1985); J. Zhang et al., JA
m. Chem. Soc., vol. 116, page 2655 (1994)). For the polymerization of discotic liquid crystals,
It is described in JP-A-8-27284. In order to fix the discotic liquid crystal by polymerization, it is preferable to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal, and after alignment, crosslink by thermal polymerization or photopolymerization to fix the discotic liquid crystal. However, when the polymerizable group is directly bonded to the discotic core, it becomes difficult to maintain the alignment state in the polymerization reaction. Therefore, it is preferable to introduce a linking group between the discotic core and the polymerizable group.

Examples of the photopolymerization initiator which causes a polymerization reaction for fixing the aligned discotic liquid crystal while maintaining the aligned state include α-carbonyl compounds (US Pat.
No. 67661, No. 2376670).
Acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2951758). , Triarylimidazole dimer and p-aminophenyl ketone combination (US Pat.
No. 5,493,67), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass of the solid content of the coating solution,
It is more preferably 5 to 5% by mass. The light irradiation for polymerizing the discotic liquid crystal molecules preferably uses ultraviolet rays. The irradiation energy is 20 to 5
Is preferably 000mJ / cm _2, and more preferably in the range of 100 to 800 mJ / cm _2. Further, in order to accelerate the photopolymerization reaction, light irradiation may be carried out under heating conditions. A protective layer may be provided on the optically anisotropic layer.

[Phase Difference Plate] The phase difference plate preferably functions as a λ / 4 plate. The λ / 4 plate has a retardation value (Re59) measured at least at a wavelength of 590 nm.
0) is required to be 120 to 160 nm and may be composed of a single sheet or a plurality of sheets. It is preferable that the retardation value is λ / 4 in a wide wavelength range, and that the polymer film is a single sheet and in a roll form. The λ / 4 plate has its slow axis as the absorption axis of the linear polarizing film and
It is necessary to bond them at a 5 ° angle to form a circularly polarizing plate. In order to bond the linearly polarizing film and the λ / 4 plate by roll-to-roll, the absorption axis is inclined at 45 ° in the longitudinal direction of the film. A long linear polarizing film and a λ / 4 plate whose slow axis is parallel to the longitudinal direction of the film, or a long linear polarizing film whose absorption axis is parallel to the longitudinal direction of the film and a slow axis is the longitudinal direction of the film. A combination with a λ / 4 plate inclined by 45 ° in the direction is preferable.

Specifically, a birefringent film having a large retardation and a birefringent film having a small retardation, which are described in JP-A-5-27118 and JP-A-5-27119, are used. If the retardation plates are laminated so that their axes are orthogonal to each other and the difference in retardation between the two films is λ / 4 over the entire visible light range, the retardation plate is theoretically Functions as a λ / 4 plate.

Further, in Japanese Patent Laid-Open No. 10-68816,
A retardation plate capable of obtaining λ / 4 in a wide wavelength range by stacking a polymer film having λ / 4 at a specific wavelength and a polymer film having the same wavelength and having λ / 2 at the same wavelength. Is disclosed. Japanese Unexamined Patent Application Publication No. 10-90521 also discloses a film capable of achieving λ / 4 in a wide wavelength region by stacking two polymer films.

A preferred λ / 4 plate is a single polymer film, specifically, a single polymer film described in JP 2000-137116 A and WO 00/26705, and the shorter the measurement wavelength is. The retardation plate has a small retardation.

The λ / 4 plate has a retardation value (Re450) measured at a wavelength of 450 nm of 100 to 125 nm.
And the retardation value (Re590) measured at a wavelength of 590 nm is 120 to 160 nm, and the relationship of Re590-Re450 ≧ 2 nm is satisfied. More preferably, Re590-Re450 ≧ 5 nm, and most preferably Re590-Re450 ≧ 10 nm. The retardation value (Re450) measured at a wavelength of 450 nm is 108 to 120 nm, and the retardation value (R) measured at a wavelength of 550 nm (R
e550) is 125 to 142 nm and has a wavelength of 590n.
The retardation value (Re590) measured by m is 13
0-152 nm, and Re590-Re55
It is preferable to satisfy the relationship of 0 ≧ 2 nm. Re59
More preferably 0-Re550 ≧ 5 nm,
Most preferably, Re590-Re550 ≧ 10 nm. It is also preferable that Re550-Re450 ≧ 10 nm.

The retardation value (Re) is calculated according to the following formula. Retardation value (Re) = (nx−ny) × d where nx is the in-plane slow axis direction refractive index (maximum in-plane refractive index) of the λ / 4 plate; ny is λ Is the refractive index in the direction perpendicular to the slow axis in the plane of the / 4 plate; and d is
The thickness (nm) of the λ / 4 plate.

Further, it is preferable that the λ / 4 plate is composed of one sheet of polymer film satisfying the following formula. 1 ≦ (nx−nz) / (nx−ny) ≦ 2 In the formula, nx is a refractive index in the slow axis direction in the plane of the λ / 4 plate; ny is in the plane of the λ / 4 plate. Is the refractive index in the direction perpendicular to the slow axis; and nz is the refractive index in the thickness direction of the λ / 4 plate. The preferred λ / 4 plate having the above optical properties is obtained by stretching a polymer film or coating a rod-shaped liquid crystal on the polymer film and then rubbing to align the rod-shaped liquid crystal and fixing the orientation by photopolymerization or the like. It can be produced by providing an optically anisotropic layer and further laminating these polymer films. The slow axis direction of the λ / 4 plate can be controlled by oblique stretching, oblique rubbing, or the like.

[Λ / 4 plate consisting of one film] λ /
The thickness of one polymer film that composes four plates is 5 to
It is preferably 1000 μm, and 10 to 500 μm
Is more preferable, 40 to 200 μm is further preferable, and 70 to 120 μm is most preferable.

[Polymer Film] As the polymer of the polymer film, the polymer of the transparent support of the optical compensation film described above can be used in the same manner. The polymer is preferably a cellulose ester, more preferably a lower fatty acid ester of cellulose. What is a lower fatty acid?
It means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate), particularly preferably cellulose acetate. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may also be used. The average degree of acetylation (degree of acetylation) of cellulose acetate is preferably 45.0 to 62.5%, more preferably 55.0 to 61.0%, and 59.0 to 60.0. % Is most preferred.

[Retardation Raising Agent] In order to adjust the retardation value at each wavelength, a retardation raising agent can be added to a polymer film, preferably a cellulose acetate film. The retardation increasing agent may be the same as the above-mentioned optical compensation film, for example, triphenyltriazines, but a rod-shaped compound having at least one aromatic ring, for example, p of 1,4-cyclohexanedicarboxylic acid.
-N-heptylphenol diester is preferred. The retardation increasing agent is preferably used in the range of 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and more preferably 0.2 to 100 parts by mass of the polymer. More preferably, it is used in the range of 5 to 5 parts by mass, and most preferably in the range of 0.5 to 2 parts by mass. You may use together two or more types of retardation raising agents.

The retardation increasing agent is from 250 to 40
It preferably has a maximum absorption in the wavelength region of 0 nm.
The retardation increasing agent preferably has substantially no absorption in the visible region. In the polymer film, the refractive index (refractive index nx in the in-plane slow axis direction, refractive index ny in the direction perpendicular to the in-plane slow axis, and refractive index nz in the thickness direction) can be adjusted by further stretching treatment. preferable. Further, the slow axis can be tilted by 45 ° with respect to the longitudinal direction of the film by the same method as the above-mentioned oblique stretching of PVA.

[Coating Type λ / 4 Plate] As the λ / 4 plate, the coating type λ / 4 plate described in JP-A-2001-21720 can also be used. That is, by introducing a twist structure into one of the two optically anisotropic layers, it became possible to significantly improve the broadband characteristics. The two optically anisotropic layers are preferably layers made of a birefringent film or liquid crystal, more preferably at least one layer made of liquid crystal, and most preferably both layers made of liquid crystal.
That is, the optical anisotropic layer made of liquid crystal is easier to control the optical properties than the birefringent film made of polymer.

The direction of the slow axis of the optically anisotropic layer containing liquid crystal is
It can be easily adjusted by the rubbing direction of the liquid crystal molecules.
Furthermore, the required retardation value can be strictly adjusted by adjusting the type and amount of liquid crystal molecules. In this case, the product of the orientation birefringence and the thickness of the optically anisotropic layer is 150 to 350 nm with respect to light having a wavelength of 550 nm, which is a wavelength approximately in the middle of the visible region. The optical anisotropic layer is
Further, it has a twist structure with a twist angle of 3 to 45 °. The product of the orientation birefringence and the thickness corresponds to the in-plane retardation value when the twist structure does not exist.

[Birefringent Film] The other optically anisotropic layer is preferably a birefringent film having a phase difference of 60 to 170 nm with respect to light having a wavelength of about 550 nm which is substantially in the visible region. Examples of the polymer used for the birefringent film include polyolefin (eg, polyethylene, polypropylene, norbornene-based polymer), polyvinyl chloride, polystyrene, polyacrylonitrile, polysulfone, polyarylate, polyvinyl alcohol,
Included are polymethacrylic acid esters, polyacrylic acid esters and cellulose esters.

Further, copolymers or polymer mixtures of these polymers may be used. The optical anisotropy of the film is preferably obtained by stretching. The stretching is preferably uniaxial stretching. The uniaxial stretching is preferably longitudinal uniaxial stretching utilizing the peripheral speed difference of two or more rolls or tenter stretching in which both sides of the polymer film are grasped and stretched in the width direction. In addition, using two or more polymer films,
The optical properties of the two or more films as a whole may satisfy the above conditions. The polymer film is preferably manufactured by a solvent casting method in order to reduce unevenness of birefringence. The thickness of the polymer film is 20 to 5
The thickness is preferably 00 nm, more preferably 50 to 200 nm, most preferably 50 to 100 nm.

[Circular Polarizing Plate] A circularly polarizing plate can be obtained by laminating the λ / 4 plate so that the slow axis thereof and the absorption axis of the linear polarizing film form an angle of substantially 45 °. When the absorption axis of the linearly polarizing film is inclined substantially 45 ° with respect to the longitudinal direction of the roll-shaped film, the slow axis of the λ / 4 plate is substantially parallel to the longitudinal direction of the roll-shaped film. Preferably, when the absorption axis of the linear polarizing film is substantially parallel to the longitudinal direction of the roll-shaped film, the slow axis of the λ / 4 plate is substantially parallel to the longitudinal direction of the roll. It is preferable that it is inclined at 45 °. The angle between the slow axis of the λ / 4 plate and the absorption axis of the linear polarizing film is preferably 41 to 49 °, more preferably 42 to 48 °, and 43 to 4 °.
It is more preferably 7 °, most preferably 44 to 46 °.

A transparent protective film is preferably provided on the surface opposite to the surface where the linearly polarizing film and the λ / 4 plate are bonded together. The transparent protective film is preferably manufactured by using a transparent polymer (having a light transmittance of 80% or more). As a transparent polymer, polyolefin (trade name: ARTON, ZEO
NEX, ZEONOR), cellulose acetate, polycarbonate, polyarylate, polysulfone or polyether sulfone can be used. A commercially available transparent polymer or transparent polymer film may be used. It is preferable that the slow axis of the transparent protective film and the absorption axis of the linear polarizing film are substantially in equilibrium.

The linear polarizing film and the λ / 4 plate or the linear polarizing film and the transparent protective film are attached to each other by using an adhesive. As the adhesive, a polyvinyl alcohol-based resin or an aqueous solution of a boron compound is preferable, and a polyvinyl alcohol-based resin is particularly preferable. As the polyvinyl alcohol-based resin, a modified polyvinyl alcohol into which a functional group other than alcohol (eg, acetoacetyl, sulfo, carboxyl, alkoxy group) is introduced may be used. The thickness of the adhesive is
It is preferably 0.01 to 10 μm after drying,
It is more preferably 0.05 to 5 μm.

[Liquid Crystal Display Device] The liquid crystal display device of the present invention exhibits a dark display when the applied voltage is low and a bright display when the applied voltage is high, even in the normally white mode, which is a bright display when the applied voltage is low and a dark display when the applied voltage is high. It can also be used in the normally black mode. As a driving method of the reflective or transflective liquid crystal display device of the present invention, an active matrix method is preferable to a simple matrix method, and a TFT (Thin Film Transistor) is preferable.
r), TFD (Thin Film Diode) or MIM (Metal Insulator Meta)
It is more preferred to use l). More preferably, low temperature polysilicon or continuous grain boundary silicon is used for the TFT.

For details of the liquid crystal display device, refer to “Liquid Crystal Device Handbook” edited by Japan Society for the Promotion of Science, 142nd Committee, Nikkan Kogyo Shimbun, “Liquid Crystal Applied” by Koji Okano, Baifukan, “Color Liquid Crystal Display” by Shunsuke Kobayashi, etc. , Industrial books, "Next-generation liquid crystal display technology" Tatsuo Uchida, Industrial research group, "Cutting-edge of liquid crystal display" edited by Young Researchers of Liquid Crystal, Sigma Publishing, "Liquid crystal: Basic and new application of LCD"
It is described in Liquid Crystal Young Research Group, Sigma Publishing, etc.

[0069]

EXAMPLES [Example 1] (Preparation of HAN-type liquid crystal cell) A polyimide film was provided as an alignment film on a glass substrate with an ITO electrode, and a rubbing treatment was performed. Another glass substrate with an ITO electrode was prepared, and a SiO vapor deposition film was provided as an alignment film. The two glass substrates are arranged so that the alignment films face each other, and they are bonded with a cell gap of 4.8 μm, and a liquid crystal ZLI11 manufactured by Merck Ltd.
32 (Δn = 0.396) was injected to prepare a HAN type liquid crystal cell. The retardation of the liquid crystal layer of the obtained liquid crystal cell was 671 nm.

(Preparation of Rolled λ / 4 Plate) At room temperature, 120 parts by mass of cellulose triacetate having an average degree of acetylation of 59.5%, 9.36 parts by mass of triphenyl phosphate, 4.68 parts by mass of biphenyldiphenylphosphate, and letter. Trans-1,4 as a cation increasing agent
-4-n-heptylphenol diester of cyclohexanedicarboxylic acid 1.00 parts by mass, methylene chloride 5
A solution (dope) was prepared by mixing and dissolving 43.14 parts by mass, 99.35 parts by mass of methanol, and 19.87 parts by mass of n-butanol.

The obtained dope was cast on a moving stainless steel band and kept in a zone at 25 ° C. for 1 minute for 45 minutes.
The zone was allowed to dry for 5 minutes. The residual amount of solvent after drying was 30% by mass. After that, the film was peeled from the band, the winding speed was made higher than the carrying speed of the band, and the film was stretched in the carrying direction at 130 ° C. The direction perpendicular to the stretching direction was allowed to shrink freely. After stretching, 120
The film was dried by passing through the zone at 30 ° C. for 30 minutes, and the stretched film was wound up. The residual amount of solvent after stretching was 0.1% by mass.

The thickness of the obtained roll film is 10
When the retardation values (Re) at wavelengths of 450 nm, 550 nm and 590 nm were measured using an ellipsometer (M-150, manufactured by JASCO Corporation), they were 119.3 nm and 137.
2 nm and 142.7 nm. The direction of the slow axis was parallel to the transport direction (same as the stretching direction: longitudinal direction). Furthermore, from the measurement of the refractive index using an Abbe refractometer and the measurement of the angle dependence of the retardation, a wavelength of 550n
m, the refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index n in the thickness direction.
When z was calculated and the value of (nx-nz) / (nx-ny) was calculated, it was 1.60.

(Production of Roll-Shaped Linear Polarizing Film) PVA film was prepared by adding 2.0 g / l of iodine and 4.0 g / potassium iodide.
1 second aqueous solution at 25 ° C. for 240 seconds, further 10 g / l aqueous boric acid solution at 25 ° C. for 60 seconds, then introduced into a tenter stretching machine and stretched 5.3 times to stretch the tenter. After that, it was bent and kept constant in width, dried in an atmosphere of 80 ° C. while shrinking, and then separated from the tenter and wound up. The water content of the PVA film before the stretching is 3
The water content was 1% and the water content after drying was 1.5%. The difference in transport speed between the left and right tenter clips was less than 0.05%, and the angle between the center line of the film introduced and the center line of the film sent to the next step was 46 °. No wrinkles or film deformation was observed at the tenter exit.
The absorption axis direction of the obtained linear polarizing film was inclined by 45 ° with respect to the transport direction (longitudinal direction) of the tenter, and the linear polarizing film had a transmittance at 550 nm of 43.7% and a polarization degree of 9.
It was 9.97%.

(Production of Circular Polarizing Plate) Cellulose triacetate film (Fujitac TD80U, manufactured by Fuji Photo Film Co., Ltd.) and the above λ / 4 plate were placed at 55 ° C. in 1.5N.
After saponifying both sides by immersing in NaOH aqueous solution for 1 minute, polyvinyl alcohol adhesive is applied to each side by about 30μ.
To a thickness of 2 mm, the rolls were attached to both sides of the linear polarizing film by roll-to-roll, and further dried at 80 ° C. to prepare a circularly polarizing plate. The film thickness of this circularly polarizing plate was about 241 μm.

(Preparation of Optical Compensation Film) The following composition was put in a mixing tank and stirred while heating,
Each component was dissolved to prepare a cellulose triacetate solution.

[0076] ────────────────────────────────────   Cellulose triacetate solution composition ────────────────────────────────────   100 parts by mass of cellulose acetate having a degree of acetylation of 60.9%   Triphenyl phosphate (plasticizer) 8.1 parts by mass   Biphenyl diphenyl phosphate (plasticizer) 3.6 parts by mass   Methylene chloride (first solvent) 338 parts by mass   Methanol (second solvent) 27 parts by mass ────────────────────────────────────

Into another mixing tank, 15 parts by weight of the following retardation increasing agent, 80 parts by weight of methylene chloride and 20 parts by weight of methanol were charged and stirred while heating to prepare a retardation increasing agent solution.

[0078]

[Chemical 1]

52 parts by mass of the retardation increasing agent solution was mixed with 477 parts by mass of the cellulose triacetate solution and stirred to prepare a dope. The obtained dope was cast using a band casting machine. 50% by mass of residual solvent
The film in the above state was peeled from the band, transversely stretched at a stretching ratio of 17% using a tenter under the condition of 130 ° C., and the width after stretching was kept at 130 ° C. for 30 seconds. Then, the clip was removed to produce a cellulose triacetate film.

With respect to the produced cellulose triacetate film, the Re retardation value and the Rth retardation value at a wavelength of 550 nm were measured using an ellipsometer (M-150, manufactured by JASCO Corporation). Further, the axis deviation angle was measured with an automatic birefringence meter (KOBRA-21ADH, Oji Scientific Instruments). Each measurement was performed at 10 points at equal intervals in the width direction, and an average value was obtained.
Furthermore, the standard deviation of the slow axis angle was obtained. The result is the first
Shown in the table.

[0081]

[Table 1]                                 Table 1 ────────────────────────────────────   Transparent support Re value Rth value Standard deviation of slow axis angle ────────────────────────────────────   Example 1 40 nm 220 nm 1.4 °   Example 2 40 nm 220 nm 1.3 ° ────────────────────────────────────

On the cellulose triacetate film,
1.0 normal potassium hydroxide solution (solvent: IPA / propylene glycol / water = 75/13/12 wt%) #
After coating with 3 bar and heating at 60 ° C for 10 seconds, water is coated with # 1.6 bar on the same surface, and then wash water at 40 ° C 5
00cc / m ² is sprayed from the nozzle, and immediately the cleaning water on the film is blown off with an air knife three times,
It was dried with hot air at 100 ° C. to prepare a cellulose triacetate film whose surface was saponified.

On one side of a saponified cellulose triacetate film, 2.0 g of the following modified polyvinyl alcohol (the number in parentheses is Wt%) was dissolved in 36 g of water, and 12 g of methanol and glutaraldehyde (crosslinking agent) were added. 1 g of the resulting coating solution was applied with a # 14 wire bar coater, dried with hot air at 60 ° C. for 60 seconds and further dried with hot air at 90 ° C. for 160 seconds, and oriented on a roll-shaped cellulose triacetate film. A film was formed. Then, the obtained alignment film was subjected to rubbing treatment parallel to the transport direction (longitudinal direction) of the roll-shaped cellulose triacetate film.

[0084]

[Chemical 2]

On the alignment film which was rubbed in the direction of 45 ° with respect to the longitudinal direction, the following discotic liquid crystal 38.
4 g, ethylene oxide modified trimethylolpropane triacrylate (V # 360, Osaka Organic Chemical Co., Ltd.)
4.1 g, cellulose acetate butyrate (CA)
B551-0.2, Eastman Chemical Co., Ltd.) 0.8
g, cellulose acetate butyrate (CAB531-
1, Eastman Chemical Co., Ltd.) 0.2 g, photopolymerization initiator (Irgacure 907, Ciba Geigy Co., Ltd.) 1.5
g, sensitizer (Kayakyu DETX, Nippon Kayaku Co., Ltd.)
(Manufactured by Mitsui Chemicals Co., Ltd.), 0.5 g of which was dissolved in 102 g of methyl ethyl ketone was applied with a # 3 wire bar. This was attached to a metal frame and heated in a constant temperature bath at 130 ° C. for 2 minutes to take a discotic nematic phase of a monodomain. Next, UV irradiation was performed at 130 ° C. with a 120 W / cm high-pressure mercury lamp for 1 minute to polymerize the discotic liquid crystal, and then allowed to cool to room temperature. In this way, an optically anisotropic layer was formed and an optical compensation film was produced.

[0086]

[Chemical 3]

The retardation value of the optical compensation film was measured by an ellipsometer in the direction including the normal direction, the rubbing direction and the normal line, and the direction inclined by 40 ° C. or −40 ° from the normal direction. The results are shown in Table 2.

[0088]

[Table 2]                                 Table 2 ────────────────────────────────────   Optical Compensation Sheet Re (0 °) Re (-40 °) Re (40 °) ────────────────────────────────────     Example 1 38 nm 42 nm 83 nm     Example 2 40 nm 44 nm 87 nm ────────────────────────────────────

(Production of HAN Alignment Mode Reflective Liquid Crystal Display Device) A HAN type liquid crystal cell was attached to a reflector used in a commercially available reflective liquid crystal display device, and an optical compensation film was placed on the liquid crystal cell. The rubbing direction of the optical compensation film and the rubbing direction of the optical compensation film are antiparallel to each other, and an acrylic adhesive is attached to the cellulose triacetate side of the optical compensation film, and the λ / A similar acrylic adhesive was attached to the 4 plate side, and the λ / 4 plate of the circular deflection plate was laminated so that the slow axis was parallel to the rubbing direction of the liquid crystal cell, and a HAN alignment mode liquid crystal display device was manufactured. did. The configuration of this liquid crystal display device is shown below.

──────────────────────────────────── Circular polarizing plate Protective film (TD80U) Linear polarizing film (PVA / I ₂ ) Retardation plate (λ / 4 plate) ──────────────────────────────────── ─ Optical compensation film Transparent support (Cellulose triacetate film) Optical anisotropic layer (Discotic liquid crystal layer) ───────────────────────────── ──────── HAN liquid crystal cell ──────────────────────────────────── Reflector ────────────────────────────────────

White display voltage 2 is applied to the liquid crystal cell of the liquid crystal display device.
V, black display voltage 6V is applied, and the measuring instrument (EZ-Contrast 16
The front contrast ratio was measured using OD, manufactured by ELDIM. Further left and right direction (direction orthogonal to the rubbing direction of the cell)
The viewing angle (angle range where the contrast ratio is 5 or more) was examined. The results are shown in Table 3.

[0092]

[Table 3]                                 Table 3 ────────────────────────────────────   Liquid crystal display device Front contrast ratio Viewing angle ────────────────────────────────────     Example 1 15 120 °     Example 2 12 100 ° ────────────────────────────────────

Example 2 (Fabrication of Bend Alignment Liquid Crystal Cell) A glass substrate having an ITO electrode was provided with a diffusion reflection plate by aluminum vapor deposition on one side while leaving a window for a transmission type, and a diffusion reflection plate was provided thereon. A polyimide film was provided as an alignment film, and the alignment film was rubbed. A polyimide film was provided as an alignment film on the other glass substrate, and a rubbing treatment was performed. The two glass substrates thus obtained were opposed to each other in an arrangement such that the rubbing directions were parallel to each other, and the cell gap was set to 10 μm. Liquid crystalline compound having Δn of 0.1396 in the cell gap (ZLI1
132, manufactured by Merck & Co., Inc. was injected to prepare a bend alignment liquid crystal cell. The liquid crystal cell thus obtained had a retardation of 6
It was 98 nm.

Cellulose triacetate powder (average size:
2 mm) was gradually added.

[0095] ────────────────────────────────────   Cellulose acetate solution composition ────────────────────────────────────   100 parts by mass of cellulose triacetate having an acetylation degree of 60.5%   Triphenyl phosphate (plasticizer) 6.8 parts by mass   Biphenyl diphenyl phosphate (plasticizer) 4.9 parts by mass   Methyl acetate (first solvent) 240 parts by mass   Cyclohexanone (second solvent) 100 parts by mass   25 parts by mass of methanol (third solvent)   Ethanol (4th solvent) 25 parts by mass   Silica (particle size 20 nm) 0.5 parts by mass   Retardation increasing agent used in Example 1 6.7 parts by mass ────────────────────────────────────

After the addition, the mixture was left at room temperature (25 ° C.) for 3 hours. The obtained heterogeneous gel solution was cooled at -70 ° C for 6 hours, then heated to 50 ° C and stirred to obtain a dope.
Thereafter, a cellulose triacetate film was prepared in the same manner as in Example 1, and the optical characteristics and thermal conductivity were measured. The results are shown in Table 1.

Cellulose acetate film was added to 1.5
It was immersed in a specified aqueous sodium hydroxide solution at 55 ° C. for 2 minutes. It was washed in a water-washing bath at room temperature and neutralized at 30 ° C. with 0.1 N sulfuric acid. It was washed again in a water-washing bath at room temperature, and dried with warm air at 100 ° C. In this way, the surface of the cellulose acetate film was saponified.

On one surface of the saponified cellulose triacetate film, an alignment film similar to that of Example 1 was provided and the same rubbing treatment was performed.

On the alignment film, 41.0 g of the discotic liquid crystal used in Example 1, 4.0 g of ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Industry Co., Ltd.), and cellulose acetate butyrate. (CAB551-0.2, Eastman Chemical Co.) 0.90 g, cellulose acetate butyrate (CAB531-1, Eastman Chemical Co.) 0.
23 g, photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 1.35 g, sensitizer (Kayacure DET)
X, manufactured by Nippon Kayaku Co., Ltd.) (0.45 g) dissolved in 102 g of methyl ethyl ketone was applied with a # 3 wire bar. Paste this on a metal frame, 130 ℃
Was heated for 2 minutes in the constant temperature bath to form a monodomain of discotic nematic phase. Next, UV irradiation was performed at 130 ° C. for 1 minute using a 120 W / cm high pressure mercury lamp to polymerize the discotic liquid crystal. Then, it stood to cool to room temperature. The retardation value of the thus-obtained optical compensation film in the direction including the normal direction, the rubbing direction and the normal line and tilted at 40 ° C. or −40 ° from the normal direction was measured with an ellipsometer. . The results are shown in Table 2.

(Production of Linear Polarizing Film) PVA film was immersed in an aqueous solution of 2.0 g / l of iodine and 4.0 g / l of potassium iodide at 25 ° C. for 240 seconds, and further 10 g / boric acid was added.
After being immersed in an aqueous solution of 1 for 60 seconds at 25 ° C., it was introduced into a longitudinal stretching machine, stretched 7.4 times, and then kept constant in width and dried in an atmosphere of 80 ° C. while shrinking, and then a longitudinal stretching machine. I left. The water content of the PVA film before the stretching is 30%,
The water content after drying was 1.3%. The absorption axis direction of the obtained linear polarizing film is parallel to the transport direction (longitudinal direction), and the transmittance at 550 nm of this linear polarizing film is 4
The degree of polarization was 3.9% and the degree of polarization was 99.96%.

(Preparation of λ / 4 Plate) The following coating solution was coated on the cellulose triacetate film used in the optical compensation film of Example 1 with a bar coater and dried at 130 ° C. for 3 minutes to give a thickness of 0. A vertical alignment film of 0.5 μm was formed.

[0102] ────────────────────────────────────     Composition of coating liquid for vertical alignment film ────────────────────────────────────     Steroid-modified polyamic acid 5.0% by mass     N-methyl-2-pyrrolidone 25.0% by mass     Ethylene glycol monobutyl ether 25.0% by mass     Methyl ethyl ketone 45.0 mass% ────────────────────────────────────

After performing a rubbing treatment at 45 ° with respect to the transport direction (longitudinal direction) of the roll-shaped vertical alignment film, a coating solution having the following composition was applied and dried, and further 500 W / c was applied.
Ultraviolet rays were irradiated for 1 second with a mercury lamp having an illuminance of m 2 to prepare a λ / 4 plate having a retardation value of 138 nm and a slow axis direction inclined by 45 ° with respect to the longitudinal direction in the film plane.

[0104] ────────────────────────────────────     Optical anisotropic layer coating solution composition ────────────────────────────────────     32.6% by mass of the discotic liquid crystal used in Example 1     Cellulose acetate butyrate 0.2% by mass     Trimethylolpropane triacrylate 3.2 mass%     Irgacure 907 (manufactured by Ciba Geigy) 0.4% by mass     Kayakyu DETX (Nippon Kayaku Co., Ltd.) 1.1% by mass     The following chiral agent (C-2) 0.35% by mass     Methyl ethyl ketone 62.5% by mass ────────────────────────────────────

[0105]

[Chemical 4]

(Production of Circular Polarizing Plate) Cellulose triacetate film (TD80U, Fuji Photo Film Co., Ltd.)
And a λ / 4 plate were saponified on both sides in the same manner as in Example 1, and then a polyvinyl alcohol-based adhesive was applied to the cellulose triacetate side to a thickness of about 30 μm. The rolls were stuck together and further dried at 80 ° C. to prepare a circularly polarizing plate. The thickness of this elliptically polarizing plate was about 241 μm.

(Production of OCB Alignment Mode Transflective Liquid Crystal Display Device) Cellulose triacetate of the optical compensation film is arranged so that the rubbing direction of the liquid crystal cell is parallel to the rubbing direction of the optical compensation film on both sides of the bend alignment liquid crystal cell. Acrylic pressure sensitive adhesive is attached to the side, and the same acrylic pressure sensitive adhesive is applied to the λ / 4 plate side of the circularly polarizing plate on top of it, and the direction of the earth layer axis of the λ / 4 plate of the circular deflection plate is the liquid crystal cell. The circularly polarizing plate was attached so as to be antiparallel to the rubbing direction of. A prism sheet and a diffusion plate were further attached in this order to the reflective plate side of the liquid crystal cell, and a backlight unit was attached to manufacture a semi-transmissive liquid crystal display device. The structure of the liquid crystal display device is shown below.

──────────────────────────────────── Circular polarizing plate Protective film (TD80U) Linear polarizing film (PVA / I ₂ ) Retardation plate (λ / 4 plate) ──────────────────────────────────── ─ Optical compensation film Transparent support (Cellulose triacetate film) Optical anisotropic layer (Discotic liquid crystal layer) ───────────────────────────── ──────── Bend alignment liquid crystal cell (CB mode) ─────────────────────────────────── ──Optical compensation film Optical anisotropic layer (Discotic liquid crystal layer) Transparent support (Cellulose triacetate film) ─────────────────────────── ──────── circular polarizer retarder (lambda / 4 plate) linear polarizing film (PVA / I ₂₎ protective film (TD80U) ──────────────── ──────────────────── Prism sheet ──────────────────────────── ──────── Diffuser ──────────────────────────────────── Backlight

A white display voltage of 2 V and a black display voltage of 6 V were applied to the liquid crystal cell of the manufactured liquid crystal display device, and the measuring instrument (EZ-Con
The front contrast ratio was measured as a reflection type liquid crystal display device using trast 160D, manufactured by ELDIM. Furthermore, the viewing angle (angle range where the contrast ratio is 5 or more) in the left-right direction (direction orthogonal to the rubbing direction of the cell) was examined. The results are shown in Table 3.

Claims (7)

[Claims] 1. A linear polarizing film having a longitudinal direction and a retardation plate having a longitudinal direction are arranged such that their longitudinal directions are substantially parallel to each other, and the absorption axis of the linear polarizing film is longitudinal. A polarizing plate that is substantially parallel to the direction, and the slow axis of the retardation plate exists in a direction that is substantially neither parallel nor perpendicular to the longitudinal direction. 2. The polarizing plate according to claim 1, wherein the retardation plate is a λ / 4 plate, and the slow axis of the retardation plate is substantially 45 ° with respect to the longitudinal direction. 3. A linear polarizing film having a longitudinal direction and a retardation plate having a longitudinal direction are arranged such that their longitudinal directions are substantially parallel to each other, and the absorption axis of the linear polarizing film is longitudinal. A polarizing plate that is present in a direction that is neither substantially parallel nor perpendicular to the direction and in which the slow axis of the retardation plate is substantially parallel to the longitudinal direction. 4. The polarizing plate according to claim 3, wherein the retardation plate is a λ / 4 plate, and the absorption axis of the linear polarizing film is substantially 45 ° with respect to the longitudinal direction. 5. A liquid crystal display provided with a liquid crystal cell in which a nematic liquid crystal exhibiting bend alignment or hybrid alignment is enclosed between a pair of substrates with transparent electrodes having an alignment film on the surface, and at least one polarizing plate. A liquid crystal display device, wherein the polarizing plate is cut from the polarizing plate according to any one of claims 1 to 4. 6. An optical anisotropic film of an optical anisotropic layer is provided between a liquid crystal cell and a polarizing plate, and an optical compensation film comprising a transparent support and an optical anisotropic layer in which the orientation of discotic liquid crystal is fixed is disposed. Re (0 °), Re (40
°) and Re (-40 °) are 35 ± 25n, respectively.
The liquid crystal display device according to claim 5, wherein the liquid crystal display device has a range of m, 105 ± 55 nm, and 35 ± 25 nm. 7. The transparent support of the optical compensation film is optically anisotropic, has a Re retardation value in the range of 10 to 70 nm, and has Rth in the range of 70 to 400 nm.
The liquid crystal display device according to claim 6, which has a retardation value.