JP2000284120A - Phase difference plate and circular polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide wide-band λ/4 which can easily be manufactured. SOLUTION: The phase difference plate which has a long-sized transparent base and two optical anisotropic layers A and B has at least one of the optical anisotropic layers A and B formed of liquid crystal molecules and is so adjusted that an inequality I 130<Re550B-Re550A<145 and an inequality II Re450B/Re650 B<Re450A/Re650A hold for Re450A, Re550A, and Re650A as retardation values of the optical anisotropic layer A measured at wavelengths 450, 550, and 650 nm and Re450B, Re550B, and Re650B as retardation values of the optical anisotropic layer B measured at wavelengths 450, 550, and 650 nm. The in-plane phase delay axis of the optical anisotropic layer A and the in-plane phase delay axis of the optical anisotropic layer B are made substantially orthogonal to each other and the angle between the length direction of the transparent base and the in-plane phase delay axis of the optical anisotropic layer A and the angle of the length direction of the transparent base and the in-plane phase delay axis of the optical anisotropic layer B are adjusted to substantially 45 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a retardation plate having a long transparent support and an optically anisotropic layer, and a circularly polarizing plate using the same. In particular, the present invention relates to a retardation plate effective as a λ / 4 plate used for a reflection type liquid crystal display device, an optical disk writing pickup, or an antireflection film.

[0002]

2. Description of the Related Art A λ / 4 plate has a great number of uses and has already been actually used. However, even if it is called a λ / 4 plate, most achieve λ / 4 at a specific wavelength. Japanese Patent Application Laid-Open Nos. 10-68816 and 10-90521 disclose a retardation plate obtained by laminating two polymer films having optical anisotropy. The retardation plate described in Japanese Patent Application Laid-Open No. 10-68816 has a 波長 wavelength plate in which the phase difference of birefringent light is １ ／ wavelength, and a あ る wavelength plate in which the phase difference of birefringent light is 波長 wavelength. The wave plate and the wave plate are bonded together with their optical axes crossing each other. The retardation plate described in JP-A-10-10-90521 has a retardation value of 160 to 320.
At least two retardation plates each having a thickness of nm are laminated such that their slow axes are not parallel or orthogonal to each other. The retardation plates described in any of the publications can theoretically achieve λ / 4 in a wide wavelength region (theoretical explanation is detailed in JP-A-10-68816). Each of the retardation plates described in any of the publications (specifically, JP-A-10-90521 is detailed) has a laminate of two polymer films.

[0003]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. H10-6881
No. 6, No. 10-90521, the production of the retardation plate requires a complicated production process in order to adjust the optical direction (optical axis or slow axis) of the two polymer films. . The optical orientation of the polymer film generally corresponds to the longitudinal or transverse direction of the sheet or roll film. A polymer film having an optical axis or a slow axis in a diagonal direction of a sheet or a roll can theoretically be manufactured but has extremely low productivity. And Japanese Patent Laid-Open No. 10-
In the inventions described in Japanese Patent Nos. 68816 and 10-90521, the optical directions of the two polymer films are set to angles that are neither parallel nor orthogonal. Therefore, Japanese Patent Application Laid-Open
In order to manufacture the retardation plates described in JP-A-68816 and JP-A-10-90521, it is necessary to cut two types of polymer films at a predetermined angle and bond the obtained chips. If a phase difference plate is to be manufactured by bonding chips, the processing is complicated, the quality is likely to be reduced due to misalignment, the yield is reduced, the cost is increased, and deterioration due to contamination is liable to occur. Further, it is difficult to strictly control the retardation value of a polymer film. It is an object of the present invention to provide a broadband λ /
4 boards.

[0004]

The object of the present invention has been attained by the following [1] to [4] retardation plates and the following [5] circularly polarizing plates. [1] A retardation plate having a long transparent support and two optically anisotropic layers A and B, wherein at least one of the optically anisotropic layers A and B is composed of liquid crystal molecules and has a wavelength of 45
Re450A, R, which are the retardation values of the optically anisotropic layer A measured at 0 nm, 550 nm and 650 nm.
e550A and Re650A, wavelength 450 nm, 5
Re450B and Re550B, which are the retardation values of the optically anisotropic layer B measured at 50 nm and 650 nm.
And Re650B satisfy the following formulas (1) and (2), and the in-plane slow axis of the optically anisotropic layer A and the optically anisotropic layer B
And the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer A, and the longitudinal direction of the transparent support. A retardation plate, wherein an angle between the in-plane slow axis and the anisotropic layer B is substantially 45 °. (1) 130 <Re550B-Re550A <145 (2) Re450B / Re650B <Re450A / R
e650A [2] The retardation plate according to [1], wherein the optically anisotropic layer A is composed of liquid crystal molecules, and the liquid crystal molecules are substantially uniformly oriented. [3] The liquid crystal molecule of the optically anisotropic layer A is a discotic liquid crystal molecule, wherein the discotic liquid crystal molecule is oriented substantially perpendicular to the transparent support surface. Phase difference plate. [4] The retardation plate according to [1], wherein the optically anisotropic layer B is made of a polymer film.

[5] A circularly polarizing plate comprising a polarizing film, a long transparent support, and two optically anisotropic layers A and B, wherein at least the optically anisotropic layers A and B One is composed of liquid crystalline molecules and has a wavelength of 450 nm, 550 nm.
Re450A, Re550A and R, which are the retardation values of the optically anisotropic layer A measured at 650 and 650 nm.
e650A, wavelengths 450 nm, 550 nm and 65
Re450B, Re550B and Re650B, which are the retardation values of the optically anisotropic layer B measured at 0 nm.
Satisfy the following formulas (1) and (2), and the in-plane slow axis of the optically anisotropic layer A and the in-plane slow axis of the optically anisotropic layer B are substantially orthogonal to each other. And the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer A, and the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer B. Are each substantially 45 °. (1) 130 <Re550B-Re550A <145 (2) Re450B / Re650B <Re450A / R
e650A As used herein, “substantially orthogonal” or “substantially 45 °” means within an exact angle range of less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °, further preferably less than 2 °, and most preferably less than 1 °. Further, the “slow axis” means a direction in which the refractive index becomes maximum.

[0006]

As a result of the research by the present inventors, an alignment film was applied on a long transparent support, and rubbed in the direction of 45 ° with respect to the longitudinal direction of the transparent support. It has been found that by forming an optically anisotropic layer containing molecules, a retardation plate that can be bonded to a polarizing film by roll-to-roll can be obtained. Since this retardation plate can be instantaneously attached to a polarizing film in a batch, a circularly polarizing plate can be easily manufactured. In addition, a high-quality product can be obtained because the misalignment of the axis and the inclusion of foreign matter in the production of the retardation plate or the circularly polarizing plate can be avoided. In the present invention, at least one of the optically anisotropic layers A and B is composed of liquid crystalline molecules. The optically anisotropic layer composed of liquid crystal molecules 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. Therefore, there is no need to cut the film into chips as in the prior art. Further, by adjusting the type and amount of the liquid crystal molecules, the required retardation value can be strictly adjusted. Further, in the case where both the optically anisotropic layers A and B are formed of liquid crystal molecules, the rubbing treatment of each layer is performed in the direction of 45 ° opposite to the longitudinal direction of the transparent support. By performing this, a retardation plate in which the in-plane slow axis of the optically anisotropic layer A and the in-plane slow axis of the optically anisotropic layer B are substantially orthogonal can be manufactured. Further, the obtained retardation plate can be bonded to the polarizing film by roll-to-roll, and the batch bonding of chips can be omitted. Also, a transparent support,
It can also function as one protective film of the polarizing film. In this case, one manufacturing step of the circularly polarizing plate can be reduced, and the circularly polarizing plate can be made thin and lightweight.
As described above, according to the present invention, a broadband λ / 4 plate that can be easily manufactured is obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Optical Properties of Retardation Plate]
The retardation value of the optically anisotropic layer A at a wavelength of 550 nm (Re550A) and the retardation value of the optically anisotropic layer B at a wavelength of 550 nm (Re550)
b) is adjusted so as to satisfy the following equation (1). (1) 130 <Re550B-Re550A <145 Difference between Re550A and Re550B (Re550B-R
e550A) is preferably from 135 to 140 nm. Second, the retardation value (Re450B) of the optically anisotropic layer B measured at a wavelength of 450 nm and the wavelength 55
The ratio (Re450B / Re550) to the retardation value (Re550B) of the optically anisotropic layer B measured at 0 nm.
Optically anisotropic layer A measured at a wavelength of 450 nm rather than B)
Retardation value (Re450A) and wavelength 550n
m of the optically anisotropic layer A (R
e550A) so that the ratio (Re450A / Re550A) becomes larger. That is, Re4
50A, Re550A, Re450B and Re550
B is set to satisfy the following expression (2).

(2) Re450B / Re650B <Re
450A / Re650A Re450A, Re550A, Re450B and Re
550B preferably satisfies the following expression (2a). Also, Re450A, Re550A, Re450B
And Re550B are represented by the following formulas (2b) and (2B)
Is preferably satisfied, and the following formulas (2c) and (2c) are satisfied.
C) is more preferably satisfied, and the following formula (2d) is satisfied.
And (2D) is most preferably satisfied. (2a) Re450A / Re550A-Re450B /
Re550B> 0.1 (2b) Re450B / Re550B <1.2 (2B) 1.3 <Re450A / Re550A (2c) Re450B / Re550B <1.15 (2C) 1.45 <Re450A / Re550A (2d) Re450B / Re550B <1.1 (2D) 1.6 <Re450A / Re550A

Third, the in-plane slow axis of the optically anisotropic layer A and the slow axis of the optically anisotropic layer B are made substantially orthogonal to each other. 4th
The angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer A and the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer B are , Each substantially 45
Adjust to ゜. The retardation value in the formulas (1) and (2) means an in-plane retardation value with respect to light incident from the normal direction of the optically anisotropic layer. Specifically, it is a value defined by the following equation (3). (3) Retardation value (Re) = (nx−ny) ×
In the formula, nx and ny are the in-plane principal refractive index of the optically anisotropic layer, and d is the thickness (nm) of the optically anisotropic layer.

When the retardation plate has the above optical properties, λ / 4 can be achieved in the entire required wavelength range. The required wavelength range is generally selected from the visible range, that is, in the range of 400 to 800 nm. It is desirable that λ / 4 can be achieved even in a wavelength range of 100 nm or more from the visible region.

[Structure of Retardation Plate] FIG. 1 is a schematic sectional view showing a typical constitution of the retardation plate of the present invention. As shown in FIG. 1, a typical retardation plate includes a long transparent support (S), an alignment film (1), an optically anisotropic layer A (A), and an optically anisotropic layer B (B ) Are stacked in this order. The in-plane slow axis (a) of the optically anisotropic layer A (A) and the in-plane slow axis (b) of the optically anisotropic layer B (B) are orthogonal to each other. The angle between the longitudinal direction (c) of the transparent support (S) and the in-plane slow axis (a) of the optically anisotropic layer A (A) is 45 °, and the transparent support (S) The angle between the longitudinal direction and the slow axis in the plane of the optically anisotropic layer B (B) is also 45 °. The optically anisotropic layer A (A) shown in FIG. 1 contains discotic liquid crystalline molecules (2). The discotic liquid crystal molecules (2) are vertically oriented. The direction of the disc surface of the discotic liquid crystalline molecules (2) corresponds to the in-plane slow axis (a) of the optically anisotropic layer A (A). The optically anisotropic layer B (B) shown in FIG. 1 is a uniaxially stretched film.

[Optical Anisotropic Layer Made of Polymer Film] The optically anisotropic layer B is preferably made of a polymer film. The polymer film is formed from a polymer that can impart optical anisotropy to the film. Examples of such polymers include polyolefins (eg, polyethylene, polypropylene, norbornene-based polymers), polyvinyl alcohol, polymethacrylates, polyacrylates and cellulose esters. 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 a polymer film are gripped and stretched in the width direction. In addition,
When two or more polymer films are used, the optical properties of the entire two or more films may satisfy the above conditions.
When the intrinsic birefringence of the polymer used is positive, the in-plane slow axis of the polymer film corresponds to the stretching direction of the film. When the intrinsic birefringence of the polymer used is negative, the in-plane slow axis of the polymer film corresponds to a direction perpendicular to the stretching direction of the film. Polymer films are
In order to reduce birefringence unevenness, it is preferable to manufacture by a solvent casting method. The thickness of the polymer film is preferably from 20 to 500 nm,
The thickness is more preferably from 200 to 200 nm, and most preferably from 50 to 100 nm.

[Optical Anisotropic Layer Made of Liquid Crystalline Molecules] The optically anisotropic layer A is preferably made of liquid crystal molecules. As the liquid crystal molecules, rod-shaped liquid crystal molecules or discotic liquid crystal molecules are preferable, and discotic liquid crystal molecules having a high refractive index in the thickness direction 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. The orientation of the liquid crystal molecules is adjusted so that the in-plane slow axis of the optically anisotropic layer and the in-plane slow axis of the polymer film are substantially orthogonal to each other. When a discotic liquid crystal is used, the liquid crystal is homogeneously oriented so that the director of the liquid crystal faces the slow axis in the plane of the polymer film. When a rod-shaped liquid crystal is used, the liquid crystal is homogeneously oriented so that the director is oriented in a direction orthogonal to the slow axis in the plane of the polymer film. As the rod-like liquid crystal molecules, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates,
Cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, 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.

Particularly preferred discotic liquid crystalline molecules will be further described. Discotic liquid crystal molecules are substantially perpendicular (50) to the polymer film plane.
(An average inclination angle in the range of 90 to 90 degrees). Discotic liquid crystalline molecules are described in various literatures (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vo.
l. 71, page 111 (1981); edited by The 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. Chem. C
omm., page 1794 (1985); J. Zhang et al., J. Am. Che
m. Soc., vol. 116, page 2655 (1994)). Regarding the polymerization of discotic liquid crystalline molecules,
It 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 an oriented 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).

[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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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.

[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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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 not having one)
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 crystal molecules are fixed while maintaining the alignment 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 US 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 from 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 crystalline 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 hydrocarbon group having 10 or more carbon atoms is effective. In order to make the hydrocarbon group exist on the surface of the alignment film, it is preferable to introduce the hydrocarbon group into a side chain rather than the main chain of the polymer. 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 preferably from 10 to 100, more preferably from 10 to 60, and most preferably from 10 to 40. The main chain of the polymer is
It 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 hydrocarbon group may be present in the repeating unit derived from a tetracarboxylic acid, may be present in the repeating unit derived from a diamine, or may be present 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.

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%.

A preferred modified polyvinyl alcohol having a hydrocarbon group having 10 or more carbon atoms is represented by the following formula (P
V). (PV)-(VAl) x- (HyC) y- (VAc) z
-Where VAl is a repeating unit of vinyl alcohol; HyC is a repeating unit having a hydrocarbon group having 10 or more carbon atoms; VAc is a repeating unit of vinyl acetate; x is from 20 to 95 mol. % (Preferably 2
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).

[0043]

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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 combination are shown below.

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 polymerization degree 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] As the transparent support, it is preferable to use a polymer film having a small wavelength dispersion. The transparent support also preferably has a small optical anisotropy. Transparent support means that the light transmittance is 80% or more. Specifically, it is preferable that the ratio of Re400 / Re700 is less than 1.2 when the wavelength dispersion is small. The optical anisotropy is small, specifically,
The in-plane retardation (Re) is preferably at most 20 nm, more preferably at most 10 nm. The long transparent support has a roll shape or a rectangular sheet shape. It is preferable that the optically anisotropic layer is laminated using a roll-shaped transparent support and then cut into a required size. Examples of polymers include cellulose esters, polycarbonates, polysulfones, polyethersulfones, polyacrylates and polymethacrylates. 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 20 to 500 μm,
More preferably, it is 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.

[Circularly Polarizing Plate] The retardation plate of the present invention is used as a λ / 4 plate used in a reflection type liquid crystal display device, a λ / 4 plate used in a pickup for writing on an optical disk, or as an antireflection film. The λ / 4 plate used is particularly advantageously used. The λ / 4 plate is generally used as a circularly polarizing plate combined 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.
The transmission axis of the polarizing film corresponds to a 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.

The wide band λ / 4 is, specifically, a wavelength 45
The retardation value / wavelength value measured at 0 nm, 550 nm and 650 nm is 0.2 to 0.3.
Within the range. Retardation value /
The value of the wavelength is preferably in the range of 0.21 to 0.29, more preferably in the range of 0.22 to 0.28, and in the range of 0.23 to 0.27. More preferably, it is most preferably in the range of 0.24 to 0.26.

[0050]

[Example 1] Thickness 100 μm, width 500 m
An optically isotropic rolled triacetyl cellulose film having a length of 500 m and a length of 500 m was used as a transparent support. A dilute solution of steroid-modified polyamic acid was continuously applied on 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 at 45 ° to the longitudinal direction of the transparent support.

On the vertical alignment film, a coating solution having the following composition is continuously applied using a bar coater, dried and heated (alignment aging), and further irradiated with ultraviolet rays to have a thickness of 1.7.
A μm optically anisotropic layer A was formed. The discotic liquid crystalline molecules were homogeneously aligned so as to have an optical axis (director) in a direction at 45 ° to the longitudinal direction of the transparent support. The optically anisotropic layer A is oriented in a direction perpendicular to the optical axis (a direction at an angle of 45 ° to the longitudinal direction of the transparent support).
Had a slow axis.

<< Composition of Optically Anisotropic Layer A Coating Solution >>デ ィ ス The following discotic liquid crystal molecules (1) 32.6% by weight cellulose 0.7% by weight of acetate butyrate The following modified trimethylolpropane triacrylate 3.2% by weight The following sensitizer 0.4% by weight The following photopolymerization initiator 1.1% by weight 62.0% by weight of methyl ethyl ketone ──────────────────────────────────

[0053]

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[0054]

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[0055]

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The retardation value of the optically anisotropic layer A was measured. The results are shown in FIG. Wavelength 450nm, 550n
The retardation values at m and 650 nm are as follows. Re450A: 232 nm Re550A: 200 nm Re650A: 187 nm Re450A / Re650A: 1.24

Next, a norbornene film having a thickness of 100 μm was uniaxially stretched to obtain a stretched birefringent film. The obtained stretched birefringent film was used as the optically anisotropic layer B. The optically anisotropic layer B had a slow axis in the longitudinal direction. The retardation value of the optically anisotropic layer B was measured.
The results are shown in FIG. The retardation values at wavelengths of 450 nm, 550 nm and 650 nm are as follows. Re450A: 346 nm Re550A: 342 nm Re650A: 339 nm Re450A / Re650A: 1.02

A transparent support having the optically anisotropic layer A formed thereon,
The optically anisotropic layer B is formed by setting the slow axis of the optically anisotropic layer A and the slow axis of the optically anisotropic layer B to be orthogonal to each other, and furthermore, the longitudinal direction of the transparent support and the optically anisotropic layer B Lamination was performed so that the angle with the slow axis was 45 ° to obtain a retardation plate according to the present invention. The wavelength dependence of the obtained retardation plate was measured. The results are shown in FIG.

A polarizing film was laminated on the transparent support of the produced retardation plate, and an optically isotropic triacetyl cellulose film was further laminated thereon to produce a circularly polarizing plate. The angle between the slow axis of the optically anisotropic layer A and the polarizing axis of the polarizing film was adjusted to 45 °, and the angle between the slow axis of the optically anisotropic layer B and the polarizing axis of the polarizing film was adjusted to 45 °. . When the optical properties of the obtained circularly polarizing plate were examined, almost perfect circularly polarized light was achieved.

Example 2 The roll-shaped optically anisotropic layer A produced in Example 1 and a polarizing plate were continuously laminated by roll-to-roll. The angle between the slow axis of the optically anisotropic layer A and the polarization axis of the polarizing film was adjusted to 45 °. Next, the optically anisotropic layer B
Is that the slow axis of the optically anisotropic layer A is orthogonal to the slow axis of the optically anisotropic layer B, and the angle between the longitudinal direction of the transparent support and the slow axis of the optically anisotropic layer B is Laminated to 45 ゜
A circularly polarizing plate was obtained. When the optical properties of the obtained circularly polarizing plate were examined, almost perfect circularly polarized light was achieved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a typical configuration of a retardation plate of the present invention.

FIG. 2 is a graph showing the wavelength dispersion of retardation of the optically anisotropic layers A and B produced in Example 1.

FIG. 3 is a graph showing the wavelength dependence of the retardation plate manufactured in Example 1.

[Explanation of symbols]

 S Long transparent support A Optically anisotropic layer A a In-plane slow axis of optically anisotropic layer A B Optically anisotropic layer B b In-plane slow axis of optically anisotropic layer B 1 Alignment film 2 Discotic liquid crystalline molecules

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nori Kawata 210 Nakanakanuma, Minamiashigara-shi, Kanagawa Prefecture Fuji Photo Film Co., Ltd. F-term (reference) 2H049 BA03 BA07 BA42 BB03 BB49 BC02 BC04 BC05 2H091 FA11X FA11Z FB02 FC08 FC23 FC25 FD06 KA02 KA10 LA12 MA10 5D119 AA38 JA31 JA32

Claims (6)

[Claims] 1. A retardation plate comprising a long transparent support and two optically anisotropic layers A and B, wherein at least one of the optically anisotropic layers A and B comprises liquid crystal molecules. ,
Re45 which is a retardation value of the optically anisotropic layer A measured at wavelengths of 450 nm, 550 nm and 650 nm.
0A, Re550A and Re650A, and wavelength 450
Re450B, Re which are the retardation values of the optically anisotropic layer B measured at 550 nm and 650 nm.
550B and Re650B satisfy the following formulas (1) and (2), and the in-plane slow axis of the optically anisotropic layer A and the in-plane slow axis of the optically anisotropic layer B are substantially equal. Are orthogonal,
Further, the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer A, and the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer B, Each substantially 4
A retardation plate characterized by 5 °. (1) 130 <Re550B-Re550A <145 (2) Re450B / Re650B <Re450A / R
e650A 2. An optically anisotropic layer A comprising liquid crystalline molecules,
The retardation plate according to claim 1, wherein the liquid crystal molecules are substantially uniformly aligned. 3. The liquid crystal molecules of the optically anisotropic layer A are discotic liquid crystal molecules, and the discotic liquid crystal molecules are oriented substantially perpendicular to the surface of the transparent support. 2. The retardation plate according to 1. 4. The retardation plate according to claim 2, wherein the liquid crystalline molecules of the optically anisotropic layer A are contained in the optically anisotropic layer A in a polymerized state. 5. The retardation plate according to claim 1, wherein the optically anisotropic layer B is made of a polymer film. 6. A circularly polarizing plate having a polarizing film, a long transparent support, and two optically anisotropic layers A and B, wherein at least one of the optically anisotropic layers A and B has liquid crystallinity. Consisting of molecules, wavelengths 450 nm, 550 nm and 65 nm
Re450A, Re550A and Re650A, which are the retardation values of the optically anisotropic layer A measured at 0 nm.
And Re, which is the retardation value of the optically anisotropic layer B measured at wavelengths of 450 nm, 550 nm and 650 nm.
450B, Re550B and Re650B satisfy the following formulas (1) and (2), and the in-plane slow axis of the optically anisotropic layer A and the in-plane slow axis of the optically anisotropic layer B are substantially And the angle between the longitudinal direction of the transparent support and the slow axis in the plane of the optically anisotropic layer A, and the retardation in the longitudinal direction of the transparent support and the plane of the optically anisotropic layer B. A circularly polarizing plate, wherein the angle with the phase axis is substantially 45 °. (1) 130 <Re550B-Re550A <145 (2) Re450B / Re650B <Re450A / R
e650A