JP2001272536A - Polarizing plate and reflective liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance of a circularly polarizing plate. SOLUTION: In the polarizing plate comprising a linearly polarizing film and an optically anisotropic layer, the slow axis of the optically anisotropic layer measured at 400 nm wavelength and that measured at 700 nm wavelength are made essentially to intersect perpendicularly with each other. Both slow axes are made to be in directions different from the direction of the polarized light transmission axis of the linearly polarizing film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate used for pickup of various displays and optical disks,
The present invention relates to a circularly polarizing plate, an OA device, and a reflective liquid crystal display device used for a mobile terminal.

[0002]

2. Description of the Related Art Several conventional techniques for forming a circularly polarizing plate from a plurality of optically anisotropic layers are known. JP-A-10-
No. 68816 and No. 10-90521 disclose a retardation plate obtained by laminating two polymer films having optical anisotropy. JP Hei 10
The retardation plate described in -68816 is a quarter-wave plate in which the phase difference of birefringent light is ４ wavelength, and a half-wave plate in which the phase difference of birefringent light is 波長 wavelength. Are bonded together with their optical axes intersecting. JP-A-10-90
No. 521 discloses at least two retardation plates having a retardation value of 160 to 320 nm.
The layers are stacked such that their slow axes are not parallel or perpendicular to each other. The retardation plate described in any of the publications,
Λ / 4 is achieved in a wide wavelength range to some extent. Also,
A reflection type liquid crystal display device using a quarter wavelength plate is also known.

FIG. 1 is a schematic sectional view of a conventional liquid crystal display device. A transparent electrode (53) made of a transparent conductive film is provided on the inside of the front substrate (51) and the back substrate (52) made of a transparent material (eg, glass). 54) are formed.
Further, a nematic liquid crystal layer (55) is filled between the front substrate (51) and the back substrate (52),
A liquid crystal panel (56) is configured. Front side board (5
1) and the respective alignment films (5) of the back substrate (52).
4) performs a rubbing process at 90 °, that is, in a direction orthogonal to the rubbing process. The liquid crystal panel (56) has polarizing plates (57) on both sides.
And basically used as a transmission type. When used as a reflection type liquid crystal display device, a reflection plate (58) is further disposed on the rear side.

FIG. 2 is a diagram showing a liquid crystal alignment direction of a conventional liquid crystal display device (shown in FIG. 1) and a polarization axis direction of a polarizing plate. The Y axis direction corresponds to the vertical axis direction of the display screen. By the rubbing treatment, the liquid crystal alignment method (60) near the front substrate (51) and the liquid crystal alignment direction (61) near the back substrate (52) are orthogonal to each other, and the liquid crystal layer (55)
Is twisted 90 degrees. The polarization axis direction (62) of the polarizing plate (57) disposed on the front substrate (51) side is at an angle of 90 ° orthogonal to the liquid crystal alignment direction (60) near the front substrate (51). Deploy. The polarization axis direction (6) of the polarizing plate (57) disposed on the back substrate (52) side
3) is arranged so as to be orthogonal to the liquid crystal alignment direction (61) by 90 ° with respect to the back side substrate (52).

In electric driving for image display, a voltage is applied between the transparent electrodes (53) inside the front substrate (51) and the back substrate (52) to perform optical control. When no voltage is applied, the linear polarization plane formed by the front polarizing plate (57), which is the light incident side, is twisted by 90 ° due to the optical rotation of the liquid crystal layer (55), and the back side, which is the transmission type emission side. And a white display is obtained. When a voltage is applied, the liquid crystal molecules of the liquid crystal layer (55) are
In addition, since the light is oriented so as to be perpendicular to the substrate surface of the back substrate (52), the linear polarization plane formed by the light incident side polarizing plate (57) directly reaches the output side polarizing plate (57). Since the polarization axis directions (62, 63) of the polarizing plate (57) are orthogonal to each other on the incident side and the exit side, the arrived light is blocked, and a black display is obtained. At this time, depending on the voltage value,
Halftone display from white to black can also be performed.

The above-described liquid crystal display device has a high contrast and is capable of halftone display.
Instead of 8), it is widely used as a transmissive type with a backlight. However, in the transmission type, an increase in power consumption, an increase in cost, and an increase in outer shape due to a backlight are a great limitation in adoption to portable devices. There is a need for a reflective liquid crystal display device that can overcome these restrictions.

However, when the above-described liquid crystal display device is used in a reflection type, the reflection plate (5) is used twice until the incident light passes through the liquid crystal layer (55) and reaches the reflection plate (58).
The light is transmitted through the polarizing plate (57) twice before being reflected by the liquid crystal layer (8) and transmitted through the liquid crystal layer (55) again and emitted, that is, four times before being optically modulated and reflected by the liquid crystal panel (56). Therefore, the attenuation of light increases. Therefore, it is difficult to obtain a bright display screen under daily ambient light.

The thickness of the back substrate (52) of the liquid crystal panel (56) exists between the liquid crystal layer (55) for optical modulation and the reflector (58). Since the direction and the viewing direction of the liquid crystal panel (56) deviate from the vertical direction corresponding to the front side of the liquid crystal panel (56), a double image occurs in the image due to the above thickness, and the brightness is reduced. Such a problem of parallax lowers the display quality of an image.

In order to solve the above problems, Japanese Patent Laid-Open No.
Japanese Patent Application Publication No. 186357 proposes a reflective liquid crystal display device that has good contrast, is bright, and is capable of halftone display by providing a phase difference member inside a front-side polarizing member and a back-side reflecting member. However, in the reflection type liquid crystal display device described in the publication, a white background is achieved from the front, but there is a problem that yellowish color is noticeable when viewed obliquely. Further, there is a problem that the thickness is increased by mounting the phase difference member.

[0010]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. H10-6881
In the manufacture of the retardation plates described in JP-A Nos. 6 and 10-90521, it is difficult to adjust the optical direction (optical axis or slow axis) of the two polymer films. The optical orientation of a polymer film generally corresponds to the longitudinal or transverse direction of a sheet or roll film.Polymer films having an optical axis or a slow axis in an oblique direction of the sheet or roll are extremely difficult to manufacture. Difficult. And
In the inventions described in JP-A Nos. 10-68816 and 10-90521, the optical directions of the two polymer films are set to angles that are neither parallel nor orthogonal. But,
In these methods, the polarization azimuth of RGB varies, and R
It is difficult for both GB to approach circularly polarized light. Also, it is difficult to precisely control the retardation value of a polymer film. An object of the present invention is to provide a broadband circularly polarizing plate capable of improving the performance as a circularly polarizing plate, and a reflective liquid crystal display device using the same.

[0011]

The object of the present invention has been attained by the following polarizing plates (1) to (9) and the reflection type liquid crystal display device of (10) to (12). (1) A polarizing plate having a linear polarizing film and an optically anisotropic layer, wherein the slow axis of the optically anisotropic layer measured at a wavelength of 400 nm and the slow axis of the optically anisotropic layer measured at a wavelength of 700 nm A polarizing plate, wherein the axes are substantially orthogonal to each other, and each of the slow axes is oriented in a direction different from the polarization transmission axis of the linear polarizing film. (2) Linear polarizing film and three optically anisotropic layers A, B and C
Wherein the optically anisotropic layer A is substantially 1
The optically anisotropic layer B has a retardation of 波長 wavelength, the optically anisotropic layer B has a retardation of substantially ４ wavelength, and the slow axis of the optically anisotropic layer C measured at a wavelength of 400 nm; The polarizing plate according to (1), wherein the slow axis of the optically anisotropic layer C measured at a wavelength of 700 nm is substantially orthogonal. (3) The polarizing plate according to (2), wherein one of the optically anisotropic layers A and B is a layer formed of liquid crystal molecules, and the other is a layer formed of a polymer film. (4) The polarizing plate according to claim 2, wherein each of the optically anisotropic layers A and B is a layer formed from liquid crystalline molecules. (5) The polarizing plate according to (3) or (4), wherein the liquid crystal molecules are discotic liquid crystal molecules.

(6) A linearly polarizing film, an optically anisotropic layer A, an optically anisotropic layer C, and an optically anisotropic layer B are laminated in this order, and the optical anisotropy measured at a wavelength of 400 nm. Layer C
Axis and optically anisotropic layer C measured at a wavelength of 700 nm
Wherein the slow axis is substantially orthogonal. (7) The circularly polarizing plate according to (6), wherein one of the optically anisotropic layers A and B is a layer formed of liquid crystal molecules, and the other is a layer formed of a polymer film. (8) The circularly polarizing plate according to (6), wherein each of the optically anisotropic layers A and B is a layer formed from liquid crystal molecules. (9) The circularly polarizing plate according to (7) or (8), wherein the liquid crystal molecules are discotic liquid crystal molecules.

(10) An electrode is formed on each of the inner surfaces of the pair of transparent substrates, and the pair of transparent substrates are bonded to each other with a liquid crystal layer interposed therebetween. Has a mechanism of reflecting off the reflective member and returning it to the outside of the front transparent substrate, and a linear polarizer disposed on the front transparent substrate and disposed inside the reflective member on the back transparent substrate side A reflective liquid crystal display device including a polarizing plate comprising an optically anisotropic layer, wherein the polarizing plate is the polarizing plate according to any one of (1) to (5). (11) The reflection type liquid crystal display device according to (10), wherein the electrode is a transparent electrode, and the optically anisotropic layer is disposed inside the linear polarizer and inside the reflection member. (12) The reflective liquid crystal display device according to (10), wherein the liquid crystal layer is a twisted nematic type.

[0014]

The optically anisotropic layer containing liquid crystal molecules used in the present invention is easier to control the optical properties than the polymer film. The optical direction of the optically anisotropic layer containing liquid crystal molecules can be easily adjusted by the rubbing direction of the liquid crystal molecules. The required retardation value can also be strictly adjusted by adjusting the type and amount of the liquid crystal molecules and the alignment state of the liquid crystal molecules. Further, by using an optically anisotropic layer in which the slow axis is different by 90 ° between the wavelength of 400 nm and the wavelength of 700 nm, the circular polarization characteristics can be secured in a wide band. Furthermore, by using the present invention for a reflection type liquid crystal display device, a reflection type liquid crystal display device excellent in display quality can be obtained by eliminating oblique yellow tint, increasing surface brightness.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Optical Properties of Retardation Plate] In the optically anisotropic layer A, the retardation value at a wavelength of 550 nm is set to a half wavelength. The specific retardation value is 200 to 300 nm. The retardation value is preferably from 230 to 280 nm,
More preferably, it is 240 to 270 nm. In the optically anisotropic layer B, the retardation value at a wavelength of 550 nm is set to １ ／ wavelength. A specific retardation value is 100 to 150 nm. The retardation value is preferably from 110 to 140 nm, more preferably from 120 to 130 nm.

In the optically anisotropic layer C, the slow axis measured at a wavelength of 400 nm (the direction in which the refractive index becomes maximum in the plane) is substantially orthogonal to the slow axis measured at a wavelength of 700 nm. . In other words, a wavelength of 400 nm to a wavelength of 700 nm
In between, there are wavelengths at which the retardation value becomes zero. It also means that the product of the retardation value measured at a wavelength of 400 nm and the retardation value measured at a wavelength of 700 nm becomes a negative value. Wavelength 4
The retardation value measured at 00 nm and the wavelength 700
Difference from the retardation value measured in nm (absolute value)
Is preferably 10 to 100 nm, more preferably 20 to 50 nm. The optically anisotropic layer C can be formed from a cellulose triacetate film or a cellulose diacetate film.

The optical directions of the two optically anisotropic layers A and B and the polarizing film are set so that the entire circularly polarizing plate becomes almost perfectly circularly polarized light. By setting the optical orientation in this way, λ / 4 can be achieved in a wide wavelength range.
For example, the angle between the slow axis of the optically anisotropic layer A and the slow axis of the optically anisotropic layer B is 60 °, and the slow axis of the optically anisotropic layer A and the polarizing axis of the polarizing film (the transmittance is By setting the angle between the slow axis of the optically anisotropic layer B and the polarization axis of the polarizing film to 15 ° and the angle between the slow axis of the optically anisotropic layer B and the polarizing axis of the polarizing film to 75 °, almost the entire visible region can be obtained. Complete circular polarization, that is, a wide band λ / 4, can be achieved. Further, the slow axis of the optically anisotropic layer A and the optically anisotropic layer B
The angle between the slow axis of the optically anisotropic layer A and the polarization axis of the polarizing film is 75 °, and the angle between the slow axis of the optically anisotropic layer A and the polarizing axis of the polarizing film is 75 °. The angle with the polarization axis may be set to 15 °. The allowable range of the above angle is within ± 10 °, preferably within ± 8 °, more preferably within ± 6 °, further preferably within ± 5 °, and ± 4 °. Most preferably, it is within the range. Specifically, the broad band λ / 4 is a wavelength of 450 nm, 550
retardation value measured at nm and 650 nm /
This means that the wavelength values are all in the range of 0.2 to 0.3. The retardation value / wavelength value is
It is preferably in the range of 0.21 to 0.29,
It is more preferably in the range of 0.22 to 0.28, further preferably in the range of 0.23 to 0.27, and most preferably in the range of 0.24 to 0.26. .

[Structures of retardation plate and circularly polarizing plate] FIG.
FIG. 3 is a cross-sectional view showing a typical mode of a retardation plate. FIG.
Has a configuration in which an optically anisotropic layer B (B), an optically anisotropic layer C (C), and an optically anisotropic layer A (A) are laminated in this order. At least one of the optically anisotropic layers A and B is preferably a layer formed from discotic liquid crystalline molecules. When a layer is formed from discotic liquid crystal molecules, an alignment film is applied on a support, and the discotic liquid crystal molecules are vertically aligned thereon.
FIG. 4 is a plan view showing the direction of the slow axis of the optically anisotropic layer. As shown in FIG. 4, the wavelength of the optically anisotropic layer C is 400 n.
The angle (γ) in the same plane between the slow axis (c400) measured at m and the slow axis (c700) measured at a wavelength of 700 nm.
Is 90 °. The slow axis (a) of the optically anisotropic layer A and the slow axis (c7) of the optically anisotropic layer C measured at a wavelength of 700 nm.
The angle (α) in the same plane as (00) is preferably 10 to 20 °. Slow axis (a) of optically anisotropic layer A
It is preferable that the angle (β) of the optically anisotropic layer B and the slow axis (b) in the same plane be 50 to 70 °.

FIG. 5 is a schematic sectional view showing a typical embodiment of a circularly polarizing plate. The circularly polarizing plate shown in FIG. 5 has an optically anisotropic layer B (B), an optically anisotropic layer C (C), and an optically anisotropic layer A.
(A) and a linearly polarizing film (P) are laminated in this order. FIG. 6 is a plan view showing the direction of the slow axis of the optically anisotropic layer and the direction of the polarization transmission axis of the linear polarizing film. As shown in FIG. 6, the angle (γ) of the slow axis (c400) of the optically anisotropic layer C measured at a wavelength of 400 nm and the slow axis (c700) measured at a wavelength of 700 nm in the same plane is: 9
0 °. Slow axis (a) of optically anisotropic layer A and wavelength 70
Slow axis of optically anisotropic layer C measured at 0 nm (c700)
Is preferably in the range of 10 to 20 °. Angle (β) of the slow axis (a) of optically anisotropic layer A and the slow axis (b) of optically anisotropic layer B in the same plane
Is preferably 50 to 70 °. The angle (δ) between the slow axis (a) of the optically anisotropic layer A and the polarization transmission axis (p) of the linear polarizing film is preferably 10 to 20 °.

[Optical Anisotropic Layer Made of Polymer Film] The polymer film is formed from a polymer capable of imparting optical anisotropy to the film. Examples of such polymers include polyolefins (eg, polyethylene, polypropylene, norbornene-based polymers), polycarbonates,
Polyarylate, polysulfone, polyvinyl alcohol, polymethacrylate, polyacrylate and cellulose ester (eg, cellulose triacetate, cellulose diacetate) are included. Further, a copolymer or a polymer mixture 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 a peripheral speed difference between two or more rolls or tenter stretching in which both sides of the polymer film are gripped and stretched in the width direction. In addition,
By using two or more polymer films, the optical properties of the entire two or more films may satisfy the above conditions.
The polymer film is preferably manufactured by a solvent casting method in order to reduce birefringence unevenness.
The thickness of the polymer film is preferably from 20 to 500 nm, more preferably from 50 to 200 nm, most preferably from 50 to 100 nm.

[Optical Anisotropic Layer Containing Liquid Crystalline Molecules] As the liquid crystal molecules, rod-like liquid crystal molecules or discotic liquid crystal molecules are preferable, and discotic liquid crystal molecules are particularly preferable. The liquid crystal molecules are preferably substantially uniformly oriented, more preferably fixed in a substantially uniform orientation state, and the liquid crystal molecules are fixed by a polymerization reaction. Is most preferred. When rod-like liquid crystal molecules are used, it is preferable to make the liquid crystal molecules horizontal and homogeneous. Examples of rod-like liquid crystal molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxane, tolan and alkenylcyclohexylbenzonitrile are preferably used. Not only low molecular liquid crystal molecules as described above but also high molecular liquid crystal molecules can be used.

When discotic liquid crystalline molecules are used, they are preferably oriented substantially vertically (average tilt angle in the range of 50 to 90 degrees). The discotic liquid crystal molecules may be obliquely aligned, or may be aligned so that the tilt angle changes gradually (hybrid alignment). Even in the case of the oblique orientation or the hybrid orientation, the average inclination angle is preferably 50 to 90 degrees. Discotic liquid crystalline molecules are described in various literatures (C. Destrade et al., Mo.
l. Crysr. Liq. Cryst., vol. 71, page 111 (1981);
The Chemical Society of Japan, Quarterly Review of Chemistry, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al.,
Angew. Chem. Soc. Chem. Comm., Page 1794 (1985);
J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page
2655 (1994)). The polymerization of discotic liquid crystal molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystal molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal molecules. However, when a polymerizable group is directly connected to the disc-shaped core,
It becomes difficult to maintain the alignment state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystalline molecule having a polymerizable group is preferably a compound represented by the following formula (I).

(I) D (-LP) _{n wherein} D is a discotic core; L is a divalent linking group; P is a polymerizable group; and n is 4 to 12 Is an integer. An example of the discotic core (D) of the formula (I) is shown below. In each of the following examples, LP (or PL) means a combination of a divalent linking group (L) and a polymerizable group (P).

[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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In the formula (I), the divalent linking group (L)
Is an alkylene group, alkenylene group, arylene group,-
It is preferably a divalent linking group selected from the group consisting of CO-, -NH-, -O-, -S- and a combination thereof. The divalent linking group (L) includes an alkylene group, an alkenylene group, an arylene group, -CO-, -NH-,-
More preferably, the group is a group obtained by combining at least two divalent groups selected from the group consisting of O- and -S-. The divalent linking group (L) is most preferably a group obtained by combining at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -CO- and -O-. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group, a halogen atom, a cyano, an alkoxy group, an acyloxy group).

Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is a polymerizable group (P).
To join. AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. L1: -AL-CO-O-AL- L2: -AL-CO-O-AL-O- L3: -AL-CO-O-AL-O-AL- L4: -AL-CO-O-AL- O-CO-L5: -CO-AR-O-AL-L6: -CO-AR-O-AL-O-L7: -CO-AR-O-AL-O-CO-L8: -CO-NH- AL-L9: -NH-AL-O-L10: -NH-AL-O-CO-

L11: -O-AL- L12: -O-AL-O- L13: -O-AL-O-CO- L14: -O-AL-O-CO-NH-AL- L15: -O- AL-S-AL-L16: -O-CO-AL-AR-O-AL-O-CO-L17: -O-CO-AR-O-AL-CO-L18: -O-CO-AR-O -AL-O-CO-L19: -O-CO-AR-O-AL-O-AL-OC-C
O-L20: -O-CO-AR-O-AL-O-AL-OA
L-O-CO-L21: -S-AL-L22: -S-AL-O-L23: -S-AL-O-CO-L24: -S-AL-S-AL-L25: -S-AR -AL-

The polymerizable group (P) in the formula (I) is determined according to the type of the polymerization reaction. Examples of the polymerizable group (P) are shown below.

[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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The polymerizable group (P) is an unsaturated polymerizable group (P
1, P2, P3, P7, P8, P15, P16, P1
7) or an epoxy group (P6, P18), more preferably an unsaturated polymerizable group,
Ethylenically unsaturated polymerizable groups (P1, P7, P8, P1
5, P16, P17). In the formula (I), n is an integer of 4 to 12. Specific numbers are determined according to the type of discotic core (D). The combination of a plurality of L and P may be different, but is preferably the same. Two or more types of discotic liquid crystal molecules (for example, a molecule having an asymmetric carbon atom in a divalent linking group and a molecule having no asymmetric carbon atom)
May be used in combination.

The optically anisotropic layer is formed by applying a coating liquid containing discotic liquid crystal molecules or the following polymerizable initiator and other additives on the vertical 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), a sulfoxide (eg, dimethylsulfoxide), a heterocyclic compound (eg, pyridine),
Hydrocarbon (eg, benzene, hexane), alkyl halide (eg, chloroform, dichloromethane), ester (eg, methyl acetate, butyl acetate), ketone (eg, acetone, methyl ethyl ketone), ether (eg, tetrahydrofuran, 1,2- Dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The application of the coating solution can be performed by a known method (eg, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method).

The vertically aligned discotic liquid crystalline molecules are fixed while maintaining the aligned state. The immobilization is preferably performed by a polymerization reaction of the polymerizable group (P) introduced into the discotic liquid crystalline molecule. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization reactions are preferred. Examples of photopolymerization initiators include α-carbonyl compounds (US Pat.
Nos. 3,766,661 and 2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. Patents 3046127 and 295175
No. 8), a combination of a triarylimidazole dimer and p-aminophenyl ketone (described in U.S. Pat. No. 3,549,367), an acridine and phenazine compound (JP-A-60-105667,
U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,221,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by weight of the solid content of the coating solution.
More preferably, it is 5 to 5% by weight. Light irradiation for the polymerization of discotic liquid crystalline molecules preferably uses ultraviolet light. The irradiation energy is 20 mJ /
cm ^{2 to} 50 J / cm ² , preferably 10
More preferably, it is 0 to 800 mJ / cm ² . Light irradiation may be performed under heating conditions to promote the photopolymerization reaction. The thickness of the optically anisotropic layer is 0.1 to 1
It is preferably 0 μm, more preferably 0.5 to 5 μm, and most preferably 1 to 5 μm.

[Vertical Alignment Film] In order to vertically align discotic liquid crystal molecules, it is important to lower the surface energy of the alignment film. Specifically, the surface energy of the alignment film is reduced by the functional group of the polymer,
As a result, the discotic liquid crystal molecules are set up. As the functional group that lowers the surface energy of the alignment film, a fluorine atom and a hydrocarbon group having 10 or more carbon atoms are effective. In order to make a fluorine atom or a hydrocarbon group exist on the surface of the alignment film, it is preferable to introduce a fluorine atom or a hydrocarbon group into a side chain rather than a main chain of the polymer. The fluorine-containing polymer preferably contains fluorine atoms at a ratio of 0.05 to 80% by weight, and 0.1 to 7% by weight.
The content is more preferably 0% by weight, more preferably 0.5 to 65% by weight, and most preferably 1 to 60% by weight. The hydrocarbon group is an aliphatic group, an aromatic group, or a combination thereof. The aliphatic group may be cyclic, branched, or linear. The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not show strong hydrophilicity, such as a halogen atom. The number of carbon atoms in the hydrocarbon group is
It is preferably 10 to 100, more preferably 10 to 60, and most preferably 10 to 40. The main chain of the polymer preferably has a polyimide structure or a polyvinyl alcohol structure.

The polyimide is generally synthesized by a condensation reaction between a tetracarboxylic acid and a diamine. A polyimide corresponding to a copolymer may be synthesized using two or more kinds of tetracarboxylic acids or two or more kinds of diamines. The fluorine atom or the hydrocarbon group may be present in a repeating unit derived from a tetracarboxylic acid, in a repeating unit derived from a diamine, or in both repeating units. When a hydrocarbon group is introduced into a polyimide, it is particularly preferable to form a steroid structure in the main chain or side chain of the polyimide. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of vertically aligning discotic liquid crystalline molecules. In the present specification, a steroid structure refers to a cyclopentanohydrophenanthrene ring structure or a ring structure in which a part of the bond of the ring is a double bond in the range of an aliphatic ring (range in which an aromatic ring is not formed). means.

[0049] Fluorine-modified polyvinyl alcohol can also be preferably used for the vertical alignment film. Fluorine-modified polyvinyl alcohol has 5 repeating units containing a fluorine atom.
In the range of 7 to 80 mol%, preferably 7 to 7 mol%.
More preferably, it is contained in the range of 0 mol%. Preferred fluorine-modified polyvinyl alcohol is represented by the following formula (PV). (PV)-(VAl) x- (FRU) y- (VAc) z- wherein VAl is a repeating unit of vinyl alcohol; FRU is a repeating unit containing a fluorine atom;
VAc is a vinyl acetate repeating unit; x is 20 to 95 mol% (preferably 24 to 90 mol%); y is 5 to 80 mol% (preferably 7 to 70 mol%); , Z are 0 to 30 mol% (preferably 2 to 20 mol%). A preferred repeating unit containing a fluorine atom (FRU) is represented by the following formula (FRU-I)
And (FRU-II).

[0050]

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In the formula, L ¹ represents —O—, —CO—, —SO
₂ -, - NH-, an alkylene group, an arylene group and a divalent linking group selected from their combinations; L
² is a single bond or -O -, - CO -, - SO 2 -,
-NH-, a divalent linking group selected from an alkylene group, an arylene group and a combination thereof;
f ¹ and Rf ² are each a fluorine-substituted hydrocarbon group. The alkylene group and the arylene group may be substituted by a fluorine atom. Examples of the divalent linking group formed by the above combination are shown below.

[0052] L1: -O-CO- L2: -O -CO- alkylene group -O- L3: -O-CO- alkylene group -CO-NH- L4: -O-CO- alkylene group -NH-SO ₂ -Arylene group-O-L5: -arylene group-NH-CO-L6: -arylene group-CO-O-L7: -arylene group-CO-NH-L8: -arylene group-O-L9: -O-CO -NH-arylene group -NH-CO-

The hydrocarbon group of the fluorine-substituted hydrocarbon group is an aliphatic group, an aromatic group or a combination thereof. The aliphatic group may be cyclic, branched or linear. The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The aliphatic group may have a substituent that does not show strong hydrophilicity, such as another halogen atom, in addition to the fluorine atom. The hydrocarbon group preferably has 1 to 100 carbon atoms,
It is more preferably from 60 to 60, and most preferably from 3 to 40. The proportion of the hydrogen atom of the hydrocarbon group substituted by a fluorine atom is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, and further preferably 80 to 100 mol%. It is most preferably 90 to 100 mol%.

Modified polyvinyl alcohol having a hydrocarbon group having 10 or more carbon atoms can also be preferably used for the vertical alignment film. The hydrocarbon group is an aliphatic group, an aromatic group, or a combination thereof. Aliphatic groups are cyclic,
It may be either branched or linear. Aliphatic groups are
It is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not show strong hydrophilicity, such as a halogen atom.
The number of carbon atoms in the hydrocarbon group is preferably from 10 to 100, more preferably from 10 to 60, and most preferably from 10 to 40. The modified polyvinyl alcohol having a hydrocarbon group contains 2 to 8 repeating units having a hydrocarbon group having 10 or more carbon atoms.
It is preferably contained in the range of 0 mol%, more preferably 3 to 70 mol%. Preferred number of carbon atoms is 1
The modified polyvinyl alcohol having 0 or more hydrocarbon groups is represented by the following formula (PV). (PV)-(VAl) x- (HyC) y- (VAc) z- wherein VA1 is a vinyl alcohol repeating unit; HyC is a repeating unit having a hydrocarbon group having 10 or more carbon atoms. VAc is a vinyl acetate repeating unit; x is 20 to 95 mol% (preferably 2 to 95 mol%)
Y is from 2 to 80 mol%)
(Preferably 3 to 70 mol%); and z is 0 to 30 mol% (preferably 2 to 20 mol%). Preferred repeating units (HyC) having a hydrocarbon group having 10 or more carbon atoms are represented by the following formulas (HyC-I) and (HyC-II).

[0055]

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In the formula, L ¹ represents —O—, —CO—, —SO
₂ -, - NH-, an alkylene group, an arylene group and a divalent linking group selected from their combinations; L
² is a single bond or -O -, - CO -, - SO 2 -,
-NH-, a divalent linking group selected from an alkylene group, an arylene group and a combination thereof;
¹ and R ² are each a hydrocarbon group having 10 or more carbon atoms. Examples of the divalent linking group formed by the above-mentioned combination include the above-mentioned formulas (FRU-I) and (FRU-I).
-II).

The degree of polymerization of the polymer used for the vertical alignment film is as follows:
It is preferably from 200 to 5,000, more preferably from 300 to 3,000. The molecular weight of the polymer is
It is preferably from 9000 to 200,000, and 13
More preferably, it is 000 to 130,000.
Two or more polymers may be used in combination. In forming the vertical alignment film, it is preferable to perform a rubbing treatment. The rubbing treatment is performed by rubbing the surface of the film containing the polymer several times with paper or cloth in a certain direction. After the discotic liquid crystalline molecules are vertically aligned using a vertical alignment film, the discotic liquid crystalline molecules are fixed in the aligned state to form an optically anisotropic layer, and only the optically anisotropic layer is formed. May be transferred onto a polymer film (or a transparent support). Discotic liquid crystal molecules fixed in the vertical alignment state can maintain the alignment state without the vertical alignment film. Therefore, in the retardation plate of the present invention, the vertical alignment film is not an essential element (although it is essential in the production of the retardation plate).

[Transparent Support] A transparent support may be used. It is preferable to use a polymer film having a small wavelength dispersion as the transparent support. The transparent support also preferably has a small optical anisotropy. Transparent support means that the light transmittance is 80% or more. The term “small chromatic dispersion” means, specifically, Re400 / Re70
Preferably, the ratio of 0 is less than 1.2. The fact that the optical anisotropy is small means that the in-plane retardation (R
e) is preferably 20 nm or less, more preferably 10 nm or less. Examples of polymers include cellulose esters, polycarbonates, polysulfones,
Includes polyethersulfone, polyacrylate and polymethacrylate. Cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. The polymer film is preferably formed by a solvent casting method. The thickness of the transparent support is preferably from 20 to 500 μm, more preferably from 50 to 200 μm. To improve the adhesion between the transparent support and the layer provided thereon (adhesive layer, vertical alignment film or optically anisotropic layer), the transparent support is subjected to a surface treatment (eg, glow discharge treatment, corona discharge treatment, ultraviolet light). (UV) treatment, flame treatment). An adhesive layer (undercoat layer) may be provided on the transparent support.

[Optically Anisotropic Layer C] The optically anisotropic layer C in the present invention has a slow axis perpendicular to the wavelength of 400 nm and a wavelength of 700 nm.
And 700 nm, the retardation has a different sign. In the present invention, the optically anisotropic layer A (１ ／ wavelength plate) and the optically anisotropic layer B (１ ／ wavelength plate) intersect to form a broadband 1
Although it is intended to form a 波長 wavelength plate, the polarization characteristics after passing through the optically anisotropic layer A (１ ／ wavelength plate) are different because the polarization azimuth angle differs between RGB due to wavelength dispersion. Even in the second optically anisotropic layer B (1/4 wavelength plate), the polarization azimuth angle is shifted, and neither RGB can be circularly polarized. However, with respect to polarized light after passing through the optically anisotropic layer A (1/2 wavelength plate), the slow axis of the optically anisotropic layer C of the present invention at a wavelength of 700 nm is smaller than that of G after passing through the optically anisotropic layer. By setting the polarization azimuth in substantially the same direction as the polarization azimuth, G has no effect and B has a negative retardation, so that the polarization azimuth can be increased to approach the azimuth of G. In addition, R can also approach the azimuth angle of G with a positive retardation, so that the RGB optically anisotropic layer A
It is possible to make the polarization azimuths after passing through a (1/2 wavelength plate) substantially coincide. Therefore, the optically anisotropic layer B (Ｂ)
After passing through the wave plate), both RGB can be circularly polarized. Such properties can be achieved by cellulose triacetate, but it can also be produced by a polymer blend of materials having intrinsic birefringence of positive and negative and different wavelength dispersion.

[Use of retardation plate] The retardation plate of the present invention is
Λ / 4 plate used in reflection type liquid crystal display device, optical disk writing pickup, GH-LCD and P
It is particularly advantageously used as a λ / 4 plate used for an S conversion element or a λ / 4 plate used as an antireflection film. The λ / 4 plate is generally used in combination with a polarizing film. Therefore, if a circularly polarizing plate is formed by combining a retardation plate and a polarizing film, it can be easily incorporated into a device such as a reflection type liquid crystal display device.
The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. Polarization axis (transmission axis) of polarizing film
Corresponds to the direction perpendicular to the stretching direction of the film. The polarizing film generally has a protective film. However, in the present invention, an optically anisotropic layer made of a polymer film or a transparent support can function as a protective film for a polarizing film. When a protective film of a polarizing film is used separately from these, it is preferable to use a cellulose ester film having high optical isotropy, particularly a triacetyl cellulose film, as the protective film.

[Reflective Liquid Crystal Display] FIG. 7 is a schematic sectional view showing a reflective liquid crystal display. The reflective liquid crystal display device shown in FIG. 7 includes, from the top, a polarizing plate (57), a half-wave plate (A), a quarter-wave plate (B), a front substrate (51),
A transparent electrode (53), an alignment film (54), a nematic liquid crystal (55), an alignment film (54), a transparent electrode (53), a back substrate (52), and a reflector (58) are formed in this order. 1
The values of the 波長 wavelength plate and the 波長 wavelength plate are values at a wavelength of 550 nm. 1/4 of wide band by combination of two wave plates
A wave plate is formed. In addition, at least one of the two retarders of the half-wave plate and the quarter-wave plate is formed by vertical alignment of the discotic liquid crystal. However, 1/2
The wave plate and the quarter wave plate need only maintain this order,
Any position may be set as long as it is between the polarizing plate and the reflecting plate, and the two retarders may be arranged apart. Further, a color filter may be arranged between the liquid crystal layer and the polarizing plate.

FIG. 8 is a diagram showing the axial configuration of each member of the reflection type liquid crystal display device. Optically anisotropic layer A (1/2 wavelength plate)
Of the optically anisotropic layer B (1/4 wavelength plate) with the slow axis (a) in the same plane (β) is 50 to 7
It is preferably 0 °. Slow axis (a) of optically anisotropic layer A (1/2 wavelength plate) and polarization transmission axis (p) of linearly polarizing film
Is preferably 10 to 20 °.

[0063]

EXAMPLES Example 1 <Optical Anisotropic Layer A> An optically isotropic roll-shaped triacetyl cellulose film having a thickness of 100 μm, a width of 500 mm and a length of 500 m was used as a transparent support. A dilute solution of a steroid-modified polyamic acid was continuously applied onto one surface of the transparent support to form a 0.5 μm-thick vertical alignment film. Next, rubbing treatment of the vertical alignment film was continuously performed in a direction of 15 ° with respect to the longitudinal direction of the transparent support.

On the vertical alignment film, a coating solution having the following composition is continuously applied by using a bar coater, dried and heated (alignment aging), and further irradiated with ultraviolet rays to have a thickness of 3.6.
An optically anisotropic layer having a thickness of μm was formed to prepare a retardation plate. Further, the optically anisotropic layer A had a slow axis in a direction perpendicular to the optical axis (a direction at 75 ° to the longitudinal direction of the transparent support).

[0065]

[Table 1] Table 1 塗布 Optically anisotropic layer coating Liquid composition デ ィ ス The following discotic liquid crystal molecules (1) 32.6 Weight% cellulose acetate butyrate 0.7 weight% modified trimethylolpropane triacrylate 3.2 weight% sensitizer 0.4 weight% photopolymerization initiator 1.1 weight% methyl ethyl ketone 62.0 Wt% ──────────────────────────────────

[0066]

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[0067]

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[0068]

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The retardation value of the optically anisotropic layer was measured. The results are shown in the graph of FIG. The retardation value at a wavelength of 550 nm was 269 nm, and at a wavelength of 550 nm, a phase difference (λ / 2) of substantially π was shown.

<Optical Anisotropic Layer B> Next, a norbornene resin (ARTON manufactured by JSR Corporation) was dissolved in methylene chloride and cast on a band to obtain a 170 μm film. The film was stretched at 150 ° C. by 20% to obtain a λ / 4 plate having a retardation of 135 nm at a wavelength of 550 nm. FIG. 10 shows the wavelength dispersion characteristics of the retardation of this film.

<Optically Anisotropic Layer C> Cotton obtained by mixing pulp cotton and linter cotton at a ratio of 1: 2 is subjected to acetylation treatment to a degree of acetylation of 2.98.
(Complete cellulose triacetate at 3.0), 15 parts by weight of a plasticizer containing triphenyl phosphate as a main component was added to 85 parts by weight of the cellulose triacetate, and a 25% by weight methylene chloride solution was added. Produced. This was cast on a metal band to produce a cellulose acetate film having a thickness of 115 μm. 10% of this film at 135 ° C
The film is stretched and the optical characteristics are measured by Oji Scientific Instruments KOBRA2
As a result of examining the wavelength dispersion characteristics of the retardation at 1 DH, the results are as shown in FIG. This film has a wavelength of 40
The retardation is different sign at 0 nm and wavelength 700 nm,
That is, the slow axes had different properties.

<Lamination> The optically anisotropic layers A, B, and C were configured as shown in FIG. 3 and the axial angles were α = 15 degrees and β in FIG.
= 60 degrees. Further, a polarizing plate was attached as shown in FIG. At this time, the polarizing plates were laminated so that the transmission axis P became δ = 15 ° C. shown in FIG. The optical characteristics of this laminate were measured using KOBRA21DH manufactured by Oji Scientific Instruments, λ /
The characteristics as four plates were evaluated. The result is shown in FIG.

Comparative Example 1 The procedure was the same as in Example 1 except that the optically anisotropic layer C was removed. FIG. 12 shows the measurement results of this laminate in the same manner as in Example 1. As can be seen from Example 1 and Comparative Example 1, by adding the optically anisotropic layer C, the characteristics of the broadband λ / 4 plate could be significantly improved.

[0074]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 2 is a diagram illustrating a liquid crystal alignment direction of a conventional liquid crystal display device and a polarization axis direction of a polarizing plate.

FIG. 3 is a cross-sectional view showing a typical mode of a phase difference plate.

FIG. 4 is a plan view showing a direction of a slow axis of the optically anisotropic layer.

FIG. 5 is a schematic cross-sectional view showing a typical mode of a circularly polarizing plate.

FIG. 6 is a plan view showing the direction of the slow axis of the optically anisotropic layer and the direction of the polarization transmission axis of the linear polarizing film.

FIG. 7 is a schematic sectional view showing a reflection type liquid crystal display device.

FIG. 8 is a diagram showing an axial configuration of each member of the reflective liquid crystal display device.

FIG. 9 is a graph showing the retardation value of the optically anisotropic layer A produced in Example 1.

FIG. 10 is a graph showing the retardation value of the optically anisotropic layer B produced in Example 1.

FIG. 11 is a graph showing a retardation value of the optically anisotropic layer C produced in Example 1.

FIG. 12 is a graph showing retardation / wavelength values of retardation films produced in Example 1 and Comparative Example 1.

[Explanation of symbols]

Reference Signs List 51 Front substrate 52 Back substrate 53 Transparent electrode 54 Alignment film 55 Liquid crystal layer 56 Liquid crystal panel 57 Polarizer 58 Reflector 60 Liquid crystal alignment direction near front substrate 61 Liquid crystal alignment direction near rear substrate 62 Polarized light disposed on front substrate Polarizing axis direction of plate 63 Polarizing axis direction of polarizing plate disposed on back side of substrate A Optically anisotropic layer A a Slow axis of optically anisotropic layer A B Optically anisotropic layer B b Optically anisotropic layer B Slow axis C of optically anisotropic layer C c400 slow axis of optically anisotropic layer C measured at a wavelength of 400 nm c700 slow axis of optically anisotropic layer C measured at a wavelength of 700 nm P linearly polarizing film p linearly polarized light The polarization transmission axis of the film α The angle of βa and c700 in the same plane β β and the angle of b in the same plane γ The angle of c400 and c700 in the same plane δ a and p in the same plane Angle at

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08J 5/18 C08J 5/18 C08L 101: 00 C08L 101: 00 (72) Inventor Ken Kawata Kanagawa 210 Nakanakanuma, Minamiashigara Fuji Photo Film Co., Ltd. F-term (reference) 2H049 BA02 BA03 BA06 BA07 BA42 BB03 BC22 2H088 EA47 2H091 FA08X FA08Z FA11X FA11Z FA14Z FB02 FC08 FC23 FC25 FD01 FD06 FD10 FD14 HA07 JA01 KA02 LA16

Claims (12)

[Claims] 1. A polarizing plate having a linear polarizing film and an optically anisotropic layer, wherein the slow axis of the optically anisotropic layer measured at a wavelength of 400 nm and the optically anisotropic layer measured at a wavelength of 700 nm The slow axis is substantially orthogonal, and both slow axes are
A polarizing plate, which is oriented in a direction different from the polarization transmission axis of the linear polarizing film. 2. A linear polarizing film and three optically anisotropic layers A and B
And C, wherein the optically anisotropic layer A has a retardation of substantially １ ／ wavelength and the optically anisotropic layer B has a retardation of substantially １ ／ wavelength. And the optically anisotropic layer C measured at a wavelength of 400 nm
Axis and optically anisotropic layer C measured at a wavelength of 700 nm
The polarizing plate according to claim 1, wherein the slow axis is substantially orthogonal. 3. The polarizing plate according to claim 2, wherein one of the optically anisotropic layers A and B is a layer formed from liquid crystalline molecules, and the other is a layer formed from a polymer film. 4. The polarizing plate according to claim 2, wherein each of the optically anisotropic layers A and B is a layer formed from liquid crystal molecules. 5. The polarizing plate according to claim 3, wherein the liquid crystal molecules are discotic liquid crystal molecules. 6. An optically anisotropic layer, wherein a linearly polarizing film, an optically anisotropic layer A, an optically anisotropic layer C, and an optically anisotropic layer B are laminated in this order and measured at a wavelength of 400 nm. A circularly polarizing plate, wherein the slow axis of C is substantially orthogonal to the slow axis of the optically anisotropic layer C measured at a wavelength of 700 nm. 7. The circularly polarizing plate according to claim 6, wherein one of the optically anisotropic layers A and B is a layer formed of liquid crystalline molecules, and the other is a layer formed of a polymer film. 8. The circularly polarizing plate according to claim 6, wherein each of the optically anisotropic layers A and B is a layer formed from liquid crystal molecules. 9. The circularly polarizing plate according to claim 7, wherein the liquid crystal molecules are discotic liquid crystal molecules. 10. An electrode is formed on each of inner surfaces of a pair of transparent substrates, and the pair of transparent substrates are bonded to each other with a liquid crystal layer interposed therebetween. It has a mechanism to reflect on the reflective member and return it to the outside of the front transparent substrate, and a linear polarizer disposed on the front transparent substrate, and an optical disposed on the back transparent substrate side inside the reflective member. A reflective liquid crystal display device including a polarizing plate comprising an anisotropic layer, wherein the polarizing plate is the polarizing plate according to any one of claims 1 to 5. 11. The reflection type liquid crystal display device according to claim 10, wherein said electrode is a transparent electrode, and said optically anisotropic layer is disposed inside a linear polarizer and inside a reflection member. 12. The reflection type liquid crystal display device according to claim 10, wherein said liquid crystal layer is of a twisted nematic type.