JP2005062671A - Optical anisotropic layer, retardation plate using the same, elliptic polarization plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical anisotropic layer, a retardation plate and an elliptic polarization plate contributing to the enlargement of a visibility angle of a liquid crystal display device. <P>SOLUTION: The optical anisotropic layer is constituted by aligning discotic liquid crystalline molecules in uniform inclined nematic orientation where an average tilt angle is 35 to 85° to the plane of the layer and the tilt angle on either boundary side and the other tilt angle on the other boundary side in the layer are substantially equal, and its phase difference in wavelength 550nm is 80 to 200nm; the retardation plate has the optical anisotropic layer and a 2nd optical anisotropic layer whose phase difference in the wavelength 550nm is 200 to 350nm and whose Nz factor (=(nx-nz)/(nx-ny)) is 0.5 to 2.0; and the elliptic polarization plate has the retardation plate and a polarizer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optically anisotropic layer, a phase difference plate, and an elliptically polarizing plate used in various displays (for example, OA equipment, reflective and transflective liquid crystal display devices used in portable terminals) and optical disk pickups. Further, the present invention relates to a reflection type, a transflective type liquid crystal display device and the like.

The λ / 4 plate has a great many applications, and is already used for a reflective LCD, a pickup for an optical disk, and a PS conversion element. However, even if it is referred to as a λ / 4 plate, most of them achieve λ / 4 at a specific wavelength. In order to achieve λ / 4 in a wider wavelength range, a technique of laminating two polymer films having optical anisotropy has been proposed (see, for example, Patent Documents 1 and 2). There has also been proposed a phase difference plate in which a polymer film having a phase difference of λ / 4 and a polymer film having a phase difference of λ / 2 are bonded together with a slow axis crossed (for example, Patent Documents). 3). Furthermore, a retardation plate is proposed in which at least two retardation plates having a retardation value of 160 to 320 nm are laminated so that their slow axes are not parallel or orthogonal to each other (for example, (See Patent Document 4). These retardation plates achieve λ / 4 in a wide wavelength region by using two polymer films. On the other hand, a broadband λ / 4 plate that has been thinned by laminating a plurality of optically anisotropic layers formed of liquid crystal molecules is also disclosed. (For example, see Patent Documents 5 and 6)
JP-A-10-68816 JP-A-10-90521 JP-A-10-68816 JP-A-10-90521 JP 2001-4837 A JP 2000-321576 A

  However, in these retardation plate examples, the retardation in the front direction is set to an appropriate size to function as a λ / 4 plate, but from the oblique direction, the liquid crystal cell, the optically anisotropic layer In both cases, the retardation is dependent on the viewing angle, resulting in a shift, resulting in a decrease in contrast. That is, the optically anisotropic layer forming the conventional λ / 4 plate does not include a function for compensating the viewing angle of the liquid crystal cell, and a λ / 4 plate technology having a wider viewing angle range is desired. . In the present invention, it has been found that it is effective to use an optically anisotropic layer in which liquid crystal molecules are aligned and fixed at a high tilt angle in order to provide the viewing angle compensation function to the λ / 4 plate.

  By the way, in the reflection type liquid crystal display device, outside light such as room light or outdoor light is used, but these lights are incident not only vertically but also obliquely. When a λ / 4 plate formed of a plurality of optically anisotropic layers is incorporated in a reflective liquid crystal display device, it usually has about a quarter wavelength at normal incidence in order to obtain sufficient dark display. Because of the design, it is often the case that the obliquely incident light deviates from a quarter wavelength. Accordingly, there remains a problem that the contrast is lowered depending on the viewing angle. In order to improve the viewing angle dependency, a liquid crystal display element including two compensation elements including a liquid crystalline film in which nematic hybrid alignment is fixed is disclosed (for example, Patent Document 6), but is still insufficient. .

  Accordingly, an object of the present invention is to provide an optically anisotropic layer, a phase difference plate and an elliptically polarizing plate that contribute to improvement of display quality and viewing angle characteristics, and display quality and viewing angle characteristics when used in a liquid crystal display device. It is an object of the present invention to provide an excellent liquid crystal display device, in particular, a reflective or transflective liquid crystal display device.

Means for solving the problems of the present invention are as follows.
(1) The discotic liquid crystal molecules have an average tilt angle of 35 to 85 ° with respect to the layer plane, and the tilt angle on one interface side in the layer is substantially equal to the tilt angle on the other interface side. An optically anisotropic layer that is nematically oriented and has a phase difference of 80 to 200 nm at a wavelength of 550 nm.
(2) An optically anisotropic layer having two or more optically anisotropic layers, wherein at least one layer is the optically anisotropic layer according to (1).
(3) The first optical anisotropic layer which is the optical anisotropic layer according to (1), a phase difference of 200 to 350 nm at a wavelength of 550 nm, and an Nz factor (the following formula) of 0.5 to 2 A retardation plate having a second optically anisotropic layer which is 0.0.
Nz factor = (nx−nz) / (nx−ny)
[Where nx and ny are in-plane main refractive indexes, and nz is the main refractive index in the thickness direction. ]
(4) The retardation plate according to (3), wherein the second optically anisotropic layer is formed by horizontally aligning liquid crystalline molecules having positive optical anisotropy.
(5) The retardation plate according to (3), wherein the second optically anisotropic layer is made of a stretched polymer film.
(6) The retardation according to any one of (3) to (5), further including a third optical anisotropic layer having a thickness direction retardation Rth (the following formula) of 0 to 300 nm at a wavelength of 589.3 nm. Board.
Rth = ((nx + ny) / 2−nz) × d
[Where nx and ny are in-plane main refractive indexes, nz is the main refractive index in the thickness direction, and d is the thickness (nm). ]
(7) The retardation plate according to (6), wherein the third optically anisotropic layer is a layer formed from a material selected from liquid crystalline molecules, triacetylcellulose, and / or cyclic polyolefin.

(8) An elliptically polarizing plate having a polarizer and the retardation plate according to any one of (3) to (7).
(9) A TN type or ECB type liquid crystal display device having the elliptically polarizing plate according to (8).
(10) The average direction of the axis projected on the plane parallel to the director of the liquid crystal molecules in the liquid crystal cell during black display, and the discotic liquid crystal molecule die uniformly oriented in the first optical anisotropic layer The liquid crystal display device according to (9), wherein a direction in which the reflector is projected onto the layer parallel plane is substantially parallel.

  According to the present invention, when used in a liquid crystal display device, an optically anisotropic layer, a phase difference plate and an elliptically polarizing plate that contribute to improving display quality and viewing angle characteristics, and liquid crystal excellent in display quality and viewing angle characteristics. A display device, in particular, a reflective or transflective liquid crystal display device can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.
The optically anisotropic layer of the present invention comprises nematic liquid crystal tilted at an average tilt angle of 35 to 85 ° with respect to the layer plane, and has a phase difference of 80 to 200 nm at a wavelength of 550 nm. The optically anisotropic layer of the present invention is produced by nematic alignment of liquid crystal compound molecules, but the liquid crystal molecules may be fixed by polymerization or the like in the layer and may no longer have liquid crystallinity. Hereinafter, the optically anisotropic layer of the present invention may be referred to as “first optically anisotropic layer”.

  In the present invention, the “tilt angle” means an angle formed by the tilted nematic liquid crystal with the layer plane, and the maximum refractive index direction in the refractive index ellipsoid of the liquid crystalline molecule is the maximum of the angles formed by the layer plane. Means the angle. Therefore, for rod-like liquid crystalline molecules having positive optical anisotropy, the tilt angle means the angle between the major axis direction of the rod-like liquid crystalline molecules, that is, the director direction and the layer plane, and negative optical anisotropy. In a discotic liquid crystal molecule having a disk-like molecular shape, the tilt angle means the inclination of the disk surface of the molecule from the layer plane. In the present invention, the “average tilt angle” means an average value of the tilt angle at the upper interface and the tilt angle at the lower interface of the optically anisotropic layer. Therefore, the average tilt angle in the layer in the uniform tilt alignment matches the tilt angle of the upper interface and the tilt angle of the lower interface, and in the hybrid alignment, it is an intermediate value between the tilt angle of the upper interface and the tilt angle of the lower interface. . In the first optically anisotropic layer, the average tilt angle of the liquid crystalline molecules is 35 ° to 85 ° as an absolute value, preferably 37 ° to 70 °, more preferably 40 ° to 60 °. When the average tilt angle is out of the range of 5 ° to 85 °, when used in a liquid crystal display device, the display contrast is lowered. The average tilt angle can be obtained by applying a crystal rotation method.

  The first optically anisotropic layer may be a layer in which uniform tilted nematic orientation (hereinafter may be simply referred to as “uniform tilt orientation”) is fixed. In the present invention, the “uniformly tilted nematic orientation” means that the liquid crystal molecules are nematically oriented while being tilted with respect to the layer plane, and the tilt angle at one interface of the layer and the tilt angle at the other interface are A substantially equal orientation form. Substantially equal means that the difference in tilt angle between the vicinity of the upper surface interface and the vicinity of the lower surface interface is less than 5 °, preferably less than 3 °, more preferably less than 1 °.

  In the case where the first optically anisotropic layer is formed by fixing a uniform tilted nematic orientation, the first optically anisotropic layer maintains its orientation under the conditions in which the liquid crystal display element is used, and its optical It is preferable that the characteristics are not lost. In the optically anisotropic layer formed by fixing the uniform tilted nematic alignment, the directors of the liquid crystal molecules are oriented at substantially the same angle at all positions in the film thickness direction of the layer. Therefore, the optically anisotropic layer has a uniaxial optical axis in an oblique direction when viewed as a structure.

  The optically anisotropic layer formed by fixing the uniform tilted nematic alignment can be produced by aligning liquid crystalline molecules in a uniform tilted nematic alignment and fixing it in the alignment state. As long as the said conditions are satisfy | filled, it may consist of what kind of material, and it does not limit about the aspect of fixation. For example, a low molecular liquid crystal can be prepared by uniformly inclining nematic alignment in a liquid crystal state and then fixing by photocrosslinking or thermal crosslinking. Alternatively, the liquid crystal can be prepared by uniformly tilting nematic alignment in a liquid crystal state and then fixing by cooling.

  The first optically anisotropic layer may be a layer formed by fixing nematic hybrid orientation (hereinafter sometimes simply referred to as “hybrid orientation”). In the present invention, “nematic hybrid alignment” refers to an alignment form in which liquid crystal molecules are nematic aligned and the tilt angle of the liquid crystal molecules is different between the upper surface and the lower surface of the layer. Therefore, in the first optical anisotropic layer, the tilt angle of the liquid crystal molecules is different between the vicinity of the upper surface interface and the vicinity of the lower surface interface. Specifically, the difference in tilt angle between the vicinity of the upper surface interface and the vicinity of the lower surface interface is 5 More than °. The tilt angle preferably changes continuously from the upper surface interface toward the lower surface interface.

  When the first optically anisotropic layer is formed by fixing the nematic hybrid orientation, the first optically anisotropic layer maintains the orientation under the conditions in which the liquid crystal display element is used, and its optical characteristics. It is preferable that it is not lost. In the first optically anisotropic layer, the directors of the liquid crystal molecules are oriented at different angles at all locations in the thickness direction of the layer. Therefore, the first optically anisotropic layer has no optical axis when viewed as a structure.

  The optically anisotropic layer composed of the liquid crystal molecules that are hybrid aligned can be produced by hybrid aligning the liquid crystal molecules so as to be in the range of the average tilt angle and fixing in the alignment state. As long as the said conditions are satisfy | filled, it may consist of what kind of material, and it does not limit about the aspect of fixation. For example, it can be produced by hybridizing a low molecular liquid crystal in a liquid crystal state and then immobilizing it by photocrosslinking or thermal crosslinking. Alternatively, the polymer liquid crystal can be prepared by hybrid alignment in a liquid crystal state and then cooling and fixing.

One aspect of the optically anisotropic layer of the present invention has an average tilt angle of 35 to 85 ° with respect to the plane, and the tilt angle on one interface side and the tilt angle on the other interface side in the layer are substantially equal. It is an optically anisotropic layer composed of rod-like liquid crystalline molecules with uniform and uniformly inclined nematic alignment and having a phase difference of 80 to 200 nm at a wavelength of 550 nm.
In another aspect of the optically anisotropic layer of the present invention, the average tilt angle is 35 to 85 ° with respect to the layer plane, and the tilt angle on one interface side and the tilt angle on the other interface side in the layer are substantially different. It is an optically anisotropic layer composed of discotic liquid crystal molecules with uniformly inclined nematic alignment and having a phase difference of 80 to 200 nm at a wavelength of 550 nm.
Another aspect of the optically anisotropic layer of the present invention is composed of rod-like liquid crystalline molecules that are nematic hybrid aligned with an average tilt angle of 35 to 85 ° with respect to the layer plane, and has a phase difference of 80 to 200 nm at a wavelength of 550 nm. It is an optically anisotropic layer.
Another embodiment of the optically anisotropic layer of the present invention is composed of a discotic liquid crystalline molecule that is nematic hybrid aligned at an average tilt angle of 35 to 85 ° with respect to the layer plane, and has a phase difference of 80 to 200 nm at a wavelength of 550 nm. An optically anisotropic layer.

  The optically anisotropic layer of the present invention alone exhibits various optical properties by laminating two or more optically anisotropic layers of the present invention or in combination with other optically anisotropic layers, When used in a liquid crystal display device, it can contribute to improvement of viewing angle characteristics, improvement of contrast, and the like.

[Optical properties of retardation plate]
One aspect of the retardation plate of the present invention includes the first optical anisotropic layer of the present invention and a second optical anisotropic layer having a phase difference of substantially π / 2 at a wavelength of 550 nm. The first optically anisotropic layer has a phase difference of substantially π at a wavelength of 550 nm. Specifically, the phase difference is 80 to 200 nm, preferably 100 to 180 nm, more preferably 120 to 160 nm. The retardation value of the second optically anisotropic layer at a wavelength of 550 nm is ½ wavelength, specifically, the retardation value at a wavelength of 550 nm is 200 to 350 nm, preferably 220 to 330 nm, More preferably, it is 240-300 nm. The Nz factor derived from the following formula of the second optically anisotropic layer is preferably in the range of 0.5 to 2.0, more preferably in the range of 0.5 to 1.5. preferable.
Nz factor = (nx−nz) / (nx−ny)
In the formula, nx and ny are in-plane main refractive indexes, and nz is a main refractive index in the thickness direction. The retardation plate made of this laminate preferably has a retardation value / wavelength value measured at wavelengths of 450 nm, 550 nm, and 650 nm, all in the range of 0.2 to 0.3.

In another aspect of the retardation plate of the present invention, the first and second optically anisotropic layers and a third optical retardation having a thickness direction retardation (Rth) of 0 to 300 nm at a wavelength of 589.3 nm are provided. Has an anisotropic layer. Rth is defined by the following mathematical formula (2). Rth of the third optically anisotropic layer is preferably 10 to 300 nm, and more preferably 50 to 200 nm. The third optically anisotropic layer preferably has negative optical anisotropy, that is, it preferably satisfies the following formula (1). Furthermore, it is preferable that nx and ny of the third optical anisotropic layer are substantially equal.
Formula (1) nx ≧ ny> nz
Formula (2) Rth = {(nx + ny) / 2−nz} × d
In the formula, nx and ny are in-plane main refractive indexes of the optically anisotropic layer, nz is the main refractive index in the thickness direction, and d is the thickness (nm) of the optically anisotropic layer.

  Hereinafter, the optically anisotropic layer (first optically anisotropic layer) of the present invention and the second and third optically anisotropic layers preferably combined with the optically anisotropic layer of the present invention will be described in detail. explain.

[First optically anisotropic layer]
In the present invention, the first optically anisotropic layer can be formed from a composition containing a liquid crystal compound. The liquid crystal compound is preferably a rod-like liquid crystal compound or a discotic liquid crystal compound.
(Bar-shaped liquid crystalline compound)
Examples of rod-like liquid crystalline compounds that can be used in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenyl. Pyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are included. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used.

  In the first optically anisotropic layer, the rod-like liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Examples of polymerizable rod-like liquid crystalline compounds that can be used in the present invention include Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and JP-A-2001-2001. And the compounds described in US Pat.

(Discotic liquid crystalline compounds)
Examples of discotic liquid crystalline compounds that can be used in the present invention include various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan). , Quarterly Chemical Review, 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)).

  In the first optically anisotropic layer, the discotic liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. JP-A-2001-4387 discloses a discotic liquid crystalline molecule having a polymerizable group.

(Tilt angle of liquid crystalline molecules)
In the aspect in which the first optically anisotropic layer is composed of liquid crystal molecules having a uniform tilted nematic alignment, the tilt angles at the upper interface and the lower interface of the liquid crystal molecules are substantially equal, so that the upper and lower layers are symmetrical with respect to the layer plane. It is. Further, in the aspect in which the first optically anisotropic layer is composed of liquid crystal molecules that are hybrid-aligned, the tilt angle is different between the upper interface and the lower interface of the liquid crystal molecules, and therefore, the first optically anisotropic layer is vertically asymmetric with respect to the layer plane. In the present invention, by setting the average tilt angle within the above range, the optically anisotropic layer contributes to improving the viewing angle when used in a liquid crystal display device. In consideration of the optical parameters of the liquid crystal cell and the required optical performance, an optically anisotropic layer having a uniform tilt orientation, an optically anisotropic layer having a hybrid orientation, or an average tilt thereof is used. The angle, the tilt angle of the upper and lower interfaces, the in-plane orientation direction, the in-plane retardation of each layer, Rth, etc. can be optimized.

  The tilt angle on the lower interface, that is, the support side and the tilt angle on the upper interface, that is, the air interface side of the first optically anisotropic layer can be controlled by selecting an air interface alignment agent added to the alignment film or the liquid crystal layer. By making the tilt angle on the lower interface side the same as the tilt angle on the air interface side, the inside of the layer can be uniformly tilted, and the tilt angle on the air interface side is made larger than the tilt angle on the lower interface side. Thus, the inside of the layer can be hybrid-aligned.

  The first optically anisotropic layer can be formed by applying a coating liquid containing a liquid crystalline compound and, if desired, the following polymerizable initiator and other additives on the alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

  The aligned liquid crystalline molecules are preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystalline molecule. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Description), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

  Moreover, in forming the optically anisotropic layer of the present invention, by using a desired additive, it is possible to reduce the occurrence of uneven optical characteristics in the optically anisotropic layer. With this additive, the surface tension of the coating solution can be lowered and the coating stability can be increased. The surface tension of the coating solution at this time is preferably 25 to 20 dyn / cm, and more preferably 23 to 21 dyn / cm. The amount of the additive used is preferably 0.01 to 1.0% by mass, more preferably 0.02 to 0.5% by mass, based on the solid content of the coating solution. There is no restriction | limiting in particular as a compound of this additive, A low molecular compound may be sufficient and a high molecular compound may be sufficient. As a preferable one, a fluorine-containing surfactant or a silicon compound can be used. As a result of using this additive, when used in a liquid crystal display device, it contributes to improvement in unevenness of display characteristics.

[Second optically anisotropic layer]
In the present invention, the second optical anisotropic layer may be made of any material as long as the optical characteristics are satisfied. Such an optically anisotropic layer may be a layer made of a composition containing a liquid crystalline compound or a stretched polymer film layer. The optical axis of the second optically anisotropic layer is preferably parallel to the layer plane. When the optically anisotropic layer is formed from a liquid crystalline compound, it is preferable that the liquid crystalline molecules are substantially horizontally (homogeneously) aligned in the layer. The substantially horizontal (homogeneous) orientation of the liquid crystal molecules means that the average angle between the director direction of the liquid crystal molecules and the layer plane is in the range of 0 to 40 °, and the director is in the vicinity of the upper surface interface and the lower surface interface. It means that the angle formed between and the layer plane is smaller than 5 °.

  As described above, the second optically anisotropic layer may be formed from a composition containing a liquid crystal compound. The liquid crystal compound is preferably a rod-like liquid crystal compound. Examples of the rod-like liquid crystalline compound that can be used for the second optically anisotropic layer are the same as those of the rod-like liquid crystalline compound that can be used for the first optically anisotropic layer.

  The liquid crystal molecule coating method and the alignment state fixing method in the second optical anisotropic layer are the same as those in the first optical anisotropic layer.

  As described above, the second optically anisotropic layer may be formed from a polymer film. The polymer film is formed from a polymer that can exhibit optical anisotropy. Examples of such polymers include polyolefins (eg, polyethylene, polypropylene, norbornene-based polymers), polycarbonate, polyarylate, polysulfone, polyvinyl alcohol, polymethacrylic acid ester, polyacrylic acid ester and cellulose ester (eg, cellulose triacetate). Tate, cellulose diacetate). Moreover, a copolymer or a polymer mixture of these polymers may be used.

  The optical anisotropy of the polymer film is preferably obtained by stretching. The stretching is preferably uniaxial stretching or biaxial stretching. Specifically, longitudinal uniaxial stretching using a difference in peripheral speed between two or more rolls, tenter stretching for grasping both sides of the polymer film and stretching in the width direction, or biaxial stretching in combination of these is preferable. In addition, 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 produced by a solvent cast method in order to reduce unevenness in birefringence. The thickness of the polymer film is preferably 20 to 500 μm, and most preferably 40 to 100 μm.

[Third optically anisotropic layer]
In the present invention, the third optically anisotropic layer may be made of any material as long as the above conditions are satisfied. For example, the third optically anisotropic layer may be a polymer film layer that exhibits optical anisotropy, or a layer that exhibits optical anisotropy by aligning liquid crystalline molecules. May be. Moreover, it may be formed from a single layer or may be formed from multiple layers.

  When the third optically anisotropic layer is a polymer film, examples of the material of the polymer film include triacetylcellulose, cyclic polyolefin, polyimide, and modified polycarbonate. These exhibit negative optical anisotropy. The material of the polymer film is not limited to the above material as long as the orientation state of the molecular chain is the same as the orientation state of the polymer molecular chain. Among them, a polymer film made of triacetyl cellulose or cyclic polyolefin is preferable. Moreover, you may express desired Rth by biaxially stretching a polymer film. In addition, an additive may be added to the polymer to adjust Rth. As methods for adjusting Rth of triacetyl cellulose, methods described in JP-A Nos. 2000-11914 and 2001-166144 are known. It has been.

  As described above, the third optically anisotropic layer may be formed from a composition containing a liquid crystalline compound. The liquid crystalline compound is preferably a discotic liquid crystalline compound or a cholesteric liquid crystalline compound, and more preferably a discotic liquid crystalline compound. A layer exhibiting negative optical anisotropy can be formed by aligning the discotic liquid crystalline molecules substantially horizontally with respect to the substrate. Such a technique is disclosed in Japanese Patent Laid-Open No. 11-352328. Substantially horizontal means that the tilt angle of the discotic liquid crystalline molecules is in the range of 0 ± 10 °. That is, the angle formed by the optical axis of the discotic liquid crystal molecules and the normal direction of the substrate is in a range of 0 ± 10 °. The tilt angle of the discotic liquid crystalline molecules may not be 0 ° (specifically, in a range of 0 ± 10 °), or may be a diagonal alignment, or a hybrid alignment in which the tilt angle gradually changes. In addition, a twisting deformation may be added to the orientation state by adding a chiral agent or applying a shear stress.

  An example of a preferable discotic liquid crystal that forms the third optically anisotropic layer is the same as the example of the discotic liquid crystal that can be used for the first optically anisotropic layer, and the preferable range thereof is also the same. The molecules of the cholesteric liquid crystalline compound exhibit negative optical anisotropy due to the helical twisted orientation. Desired optical properties can be obtained by arranging the cholesteric liquid crystalline molecules in a spiral and controlling the twist angle and retardation value of the alignment. The twisted orientation of cholesteric liquid crystalline molecules can be achieved by using a known method. The liquid crystalline molecules are preferably fixed in an aligned state, and more preferably fixed by polymerization.

[Alignment film]
When the first, second and third optically anisotropic layers are formed from liquid crystalline molecules, it is preferable to use an alignment film in order to align the liquid crystalline molecules. For example, when the first, second and third optical anisotropic layers are sequentially formed on the same support, the support / alignment film / second optical anisotropic layer / alignment film / first Optical anisotropic layer / alignment film / third optical anisotropic layer or support / alignment film / third optical anisotropic layer / alignment film / first optical anisotropic layer / alignment film / Like the second optically anisotropic layer, etc., each optically anisotropic layer can be formed on the alignment film to control the alignment and to exhibit desired optical characteristics.
The material of the alignment film can be selected according to the required optical properties and the type of liquid crystalline molecules used. In addition, even if an alignment film is not separately provided between each optically anisotropic layer, it can be laminated on the optically anisotropic layer by adding molecules having an alignment film function to the components constituting the optically anisotropic layer. The optically anisotropic layer thus formed can be brought into a desired orientation state.

  The alignment film is formed by rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, formation of a layer having a micro group, or an organic compound (for example, ω-tricosanoic acid, dioctadecyldimethyl by Langmuir-Blodgett method). It can be provided by means such as accumulation (LB film) of ammonium chloride and methyl stearate. Furthermore, an alignment film in which an alignment function is generated by application of an electric field or a magnetic field or light irradiation is also known. An alignment film formed by a polymer rubbing treatment is particularly preferable. The rubbing treatment is carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth.

  The type of polymer used for the alignment film is determined according to the alignment (particularly the average tilt angle) of the liquid crystal compound. It is preferable to adjust the surface energy according to the average tilt angle to be expressed. In the present invention, when the third optically anisotropic layer is formed of liquid crystalline molecules, it is preferable to use a polymer that does not reduce the surface energy of the alignment film. When the third optically anisotropic layer is formed using discotic liquid crystalline molecules, the rubbing treatment may not be performed and the alignment film may be omitted. However, for the purpose of improving the adhesion between the liquid crystalline molecules and the transparent support, an alignment film (described in JP-A-9-152509) forming a chemical bond with the liquid crystalline molecules at the interface may be used. When the alignment film is used for the purpose of improving adhesion, rubbing treatment need not be performed.

  In the first or second optically anisotropic layer, when directors of liquid crystalline molecules having positive optical anisotropy are aligned at an angle larger than 45 ° with respect to the major axis direction of the transparent support It is preferable to use an alignment film (hereinafter referred to as an orthogonal alignment film) in which directors of rod-like liquid crystal molecules are arranged in a direction orthogonal to the rubbing direction. The orthogonal alignment film is described in JP-A No. 2002-62427 and JP-A No. 2002-268068.

  The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm. In any of the alignment films, after the liquid crystalline molecules are fixed in the aligned state, they can be transferred onto another support. The liquid crystal compound fixed in the alignment state can maintain the alignment state even without the alignment film. Therefore, the retardation plate of the present invention requires each optically anisotropic layer formed on a temporary support, in addition to the method of sequentially forming each optically anisotropic layer on the same support. If it exists, it can also be produced by a method of bonding using an adhesive or the like.

  Any alignment film preferably has a polymerizable group. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group.

[Lamination of optically anisotropic layer]
When all the optically anisotropic layers to be laminated are made of a liquid crystal compound, the three layers may be sequentially laminated on the same support, or they may be bonded to each other after being formed on the temporary support. Then, one layer formed on the temporary support may be transferred to a laminate of two layers on the support.

  When one of the optically anisotropic layers to be laminated is a layer made of a liquid crystal compound and one is a layer made of a polymer film, the layer made of the polymer film is used as a support for forming a layer made of the liquid crystal compound. Can be used. For example, a polymer film having negative optical anisotropy, such as triacetyl cellulose, can be used as the third optical anisotropic layer and as a support for the first optical anisotropic layer made of a liquid crystalline compound. Can also be used. Furthermore, a liquid crystal compound may be applied thereon to form a second optical anisotropic layer, or a polymer film may be bonded to form a second optical anisotropic layer. Further, when the stretched polymer film is used as the second optically anisotropic layer, the optical anisotropy of the present invention comprising a liquid crystalline compound is formed on one surface of the film, and further on or on the film The third optical liquid crystal compound is laminated and applied to the other surface, the liquid crystal layer formed on the temporary support is transferred, or the polymer film is bonded to form the third optical anisotropic layer. It may be formed.

  The polymer film used as the support on which the liquid crystal compound is applied can be used as any one of the second and third optically anisotropic layers, and can be used as a protective film for the polarizer. It can also be used as a film that has both functions. In addition, the preferable form of the elliptically polarizing plate of this invention mentioned later is a thing which laminated | stacked the polarizer, the 2nd, 1st, and 3rd optically anisotropic layer in this order, but finally this order. If it becomes, the order which laminates | stacks is not ask | required.

[Support]
The retardation plate and the elliptically polarizing plate of the present invention may have a support, and the support is preferably a transparent support. As the transparent support, a glass plate or a polymer film, preferably a polymer film is used. That the support is transparent means that the light transmittance is 80% or more. The thickness of the support is preferably 10 to 500 μm, and more preferably 30 to 200 μm.

  In order to improve adhesion between the support and the layer (adhesive layer, alignment film or optically anisotropic layer) provided thereon, surface treatment (for example, glow discharge treatment, corona discharge treatment, ultraviolet treatment) is applied to the transparent support. , Flame treatment, etc.). An ultraviolet absorber may be added to the support. An adhesive layer (undercoat layer) may be provided on the transparent support. The adhesive layer is described in JP-A-7-333433. The thickness of the adhesive layer is preferably 0.1 to 2 μm, and preferably 0.2 to 1 μm.

  As the support, it is preferable to use a polymer film having a small wavelength dispersion. It is also preferable that the support has a small optical anisotropy. Specifically, the small chromatic dispersion means that the ratio of Re400 / Re700 is preferably less than 1.2. Specifically, the small optical anisotropy means that in-plane retardation (Re) is preferably 20 nm or less, and more preferably 10 nm or less. Examples of the polymer include cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate and cyclic polyolefin. Cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. Examples of the cyclic polyolefin include a polymer obtained by hydrogenating a ring-opening polymer of tetracyclododecenes or a ring-opening copolymer of tetracyclododecenes and norbornenes described in JP-B-2-9619. The polymer used as the constituent component and the product name can be used from Arton (manufactured by JSR), Zeonex, and Zeonore (manufactured by Nippon Zeon). The polymer film is preferably formed by a solvent cast method.

[Elliptically polarizing plate]
The retardation plate of the present invention is used as a λ / 4 plate used in a liquid crystal display device, a pickup for writing an optical disc, a λ / 4 plate used in a GH-LCD or a PS conversion element, or an antireflection film. It is particularly advantageously used as a λ / 4 plate. The λ / 4 plate is generally used in combination with a polarizing film. Therefore, if it is configured as an elliptically polarizing plate in which a retardation plate and a polarizing film are combined, it can be easily incorporated into a device for a purpose such as a reflection type or a transflective liquid crystal display device.

  The elliptically polarizing plate of the present invention has the retardation plate of the present invention and a linear polarizer. In the elliptically polarizing plate of the present invention, the first and second optically anisotropic layers and the linearly polarizing film are laminated so that the whole is almost completely circularly polarized. By setting the optical orientation in this way, it is possible to provide a broadband λ / 4 plate that achieves λ / 4 in a wide wavelength region. For example, the angle between the slow axis of the first optical anisotropic layer and the slow axis of the second optical anisotropic layer is 60 °, the slow axis of the first optical anisotropic layer and the polarizing film The angle between the polarization axis (the direction in which the transmittance is maximized in the plane) is set to 75 °, and the angle between the slow axis of the second optical anisotropic layer and the polarization axis of the polarizing film is set to 15 °. Thus, circularly polarized light, that is, broadband λ / 4 can be achieved in the entire visible region. The angle between the slow axis of the first optical anisotropic layer and the slow axis of the second optical anisotropic layer is 60 °, and the slow axis of the first optical anisotropic layer is The angle between the polarizing axis of the polarizing film and the polarizing axis of the polarizing film may be set to 15 ° and 15 ° and 75 °, respectively. The allowable range of the above angle is within ± 10 °, preferably within ± 8 °, more preferably within ± 6 °, further preferably within ± 5 °, and more preferably ± 4 °. Is most preferably within.

  A preferred embodiment of the elliptically polarizing plate of the present invention is an elliptically polarizing plate in which the linearly polarizing film and the second, first and third optically anisotropic layers are laminated in this order.

  In the present specification, the broad-band λ / 4 plate specifically means that the retardation value / wavelength value measured at wavelengths of 450 nm, 550 nm, and 650 nm are both in the range of 0.2 to 0.3. It means that there is. The retardation value / wavelength value is preferably in the range of 0.21 to 0.29, more preferably in the range of 0.22 to 0.28, and 0.23 to 0.27. Most preferably within the range.

  FIG. 1 is a schematic cross-sectional view showing a typical embodiment of an elliptically polarizing plate. The elliptically polarizing plate shown in FIG. 1 includes a linearly polarizing film (P), a second optically anisotropic layer (A), and a first optically anisotropic layer (both sides) sandwiched between protective films (T1, T2). B) and the third optically anisotropic layer (C) are stacked in this order. FIG. 2 is a plan view showing the direction of the slow axis of the optically anisotropic layer and the direction of the polarization transmission axis or polarization absorption axis of the linear polarizing film. In FIG. 2, the angle (a) of the slow axis (a) of the second optical anisotropic layer (A) and the slow axis (b) of the first optical anisotropic layer (B) in the same plane ( α) is preferably 50 to 70 °. In FIG. 2, the angle (β) between the slow axis (a) of the second optically anisotropic layer (A) and the polarization transmission axis or polarization absorption axis (p1) of the linear polarizing film is 10-20. It is preferable that it is (degree).

  The elliptically polarizing plate of the present invention is composed of the retardation plate of the present invention and a linear polarizing film. Examples of the linear polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The polarizing axis (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. The transparent support can function as an optically anisotropic layer made of a polymer film, or can function as a protective film on one side of the polarizing film. When a protective film is used separately from the transparent support, it is preferable to use a cellulose ester film having high optical isotropy, particularly a triacetyl cellulose film or a cyclic polyolefin film, as the protective film.

  In the elliptically polarizing plate according to the present invention, Rth of the protective film is 30 nm or less smaller than Rth of the third optical anisotropic layer. Rth of the protective film is preferably 0 to 50 nm, more preferably 0 to 30 nm, and most preferably 0 to 20 nm.

  In a different form of the elliptically polarizing plate according to the present invention, a polarizing film having a protective film only on one side may be used. That is, there is no protective film between the polarizing film and the first optically anisotropic layer, and only a substantially optically isotropic adhesive layer or adhesive layer is interposed.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes at least the elliptically polarizing plate, and includes a reflective, transflective, and transmissive liquid crystal display device. A liquid crystal display device generally includes a polarizing plate, a liquid crystal cell, and a retardation plate, a reflection layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, a color filter, and the like as necessary. Although comprised from a member, in this invention, there is no restriction | limiting in particular except the point which makes it essential to use the said elliptically polarizing plate. Further, the use position of the elliptically polarizing plate is not particularly limited, and may be one place or a plurality of places. The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used. The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate in which the substrate itself has a property of orienting liquid crystals, a transparent substrate in which an alignment film having the property of orienting liquid crystals is provided, but the substrate itself lacks the alignment ability. Either can be used. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate with which the liquid crystal layer is in contact, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film. The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal substances, polymer liquid crystal substances, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired.

  In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later. As the liquid crystal cell system, a TN (Twisted Nematic) system, a STN (Super Twisted Nematic) system, an ECB (Electrically Controlled Birefringence) system, an IPS (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, Alignment), PVA (Patterned Vertical Alignment), OCB (Optically Compensated Birefringence), HAN (Hybrid Aligned Nematic), ASM crocell) method, halftone gray scale method, domain division method, or display method using ferroelectric liquid crystal or antiferroelectric liquid crystal. The driving method of the liquid crystal cell is not particularly limited, and a passive matrix method used for STN-LCD and the like, and an active matrix method using an active electrode such as a TFT (Thin Film Transistor) electrode and a TFD (Thin Film Diode) electrode, Any driving method such as a plasma addressing method may be used. A field sequential method that does not use a color filter may be used.

  The elliptically polarizing plate in the present invention is preferably used for a reflection type and a transflective liquid crystal display device. The reflective liquid crystal display device has a configuration in which a reflector, a liquid crystal cell, and a polarizing plate are laminated in this order. The retardation plate is disposed between the reflecting plate and the polarizing film (between the reflecting plate and the liquid crystal cell or between the liquid crystal cell and the polarizing film). The reflector may share the liquid crystal cell and the substrate. The transflective liquid crystal display device includes an electro-liquid crystal cell, a polarizing plate disposed closer to the viewer than the liquid crystal cell, and at least one retardation plate disposed between the polarizing plate and the liquid crystal cell. And at least a transflective layer disposed behind the liquid crystal layer as viewed from the viewer, and at least one retardation plate and a polarizing plate behind the transflective layer as viewed from the viewer. Have In this type of liquid crystal display device, it is possible to use both a reflection mode and a transmission mode by installing a backlight.

  In the liquid crystal display device, at least one retardation plate and a polarizing plate function as an elliptical polarizing plate. The liquid crystal display device of the present invention uses the elliptically polarizing plate of the present invention in at least one place. In the present invention, it is not always necessary to integrate the polarizer and the retardation plate of the present invention into an elliptically polarizing plate, and then incorporate it into the liquid crystal display device. The first optical anisotropic layer and the polarizer are not included. Each of them incorporated into the liquid crystal display device and finally the elliptically polarizing plate of the present invention is included in the scope of the liquid crystal display device of the present invention. A preferred embodiment of the liquid crystal display device of the present invention includes a direction in which a director of liquid crystal molecules in a liquid crystal cell at the time of black display is projected onto a layer parallel plane, and an orientation of liquid crystal molecules aligned in the first optical anisotropic layer. This is an aspect in which the direction in which the director is projected onto the layer parallel plane is substantially parallel. Here, in the present invention, “substantially parallel” means that the difference in angle between the two directions is −5 degrees to less than 5 degrees, preferably −2 degrees to less than 2 degrees, more preferably −1 degree to 1 degree. It will be within. The director of the liquid crystal molecules in the liquid crystal cell can be adjusted to a desired direction by the rubbing direction of the alignment film provided on the opposing surface of the substrate.

  In the liquid crystal display device of the present invention, a broadband λ / 4 plate can be used on the opposite side of the liquid crystal cell in order to efficiently convert the elliptically polarized light transmitted through the cell into linearly polarized light. One retardation plate may be used in order to achieve wide bandwidth, or two or more retardation plates may be appropriately combined with the magnitude of retardation and the slow axis angle. In order to increase the bandwidth, an optical film having a small wavelength dispersion is desirable as a retardation plate. Specifically, a liquid crystalline film or a polymer stretched film may be used as a material for the retardation plate. As the polymer stretched film, a polymer material exhibiting uniaxiality or biaxiality, for example, a stretched film such as polycarbonate (PC), polymethacrylate (PMMA), polyvinyl alcohol (PVA), norbornene-based polymer may be used. it can. For example, in terms of low wavelength dispersion, a uniaxially stretched Arton (manufactured by JSR) film is preferable.

  The phase difference plate and the elliptically polarizing plate of the present invention are not limited to the above applications, and can be used for various other applications. For example, it can be used for an antireflection film such as a host-guest type liquid crystal display device, a touch panel, an electroluminescence (EL) element, a reflection type polarizing plate, and the like.

The present invention will be described more specifically with reference to the following examples. The materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples. The in-plane and thickness direction retardation values of the triacetylcellulose film can be measured with a birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instruments).
[Example 1]
(Production of retardation plate)
A glass substrate having a width of 100 mm and a length of 150 mm is spin-coated with a diluted polymer solution having the following structural formula, heated at 80 ° C. for 1 hour, at 180 ° C. for 1 hour, and further at 250 ° C. for 1 hour to a thickness of 0.5 μm Then, a rubbing treatment (rubbing treatment with a rubbing cloth rotating at a rotation speed of 1500 rpm) was applied to the surface to obtain an alignment film.

On the rubbing surface of this alignment film, a coating solution having the following composition is spin-coated, dried and heated (alignment aging), and further irradiated with ultraviolet rays to form an optically anisotropic layer B1 having a thickness of 4.83 μm. did. The optically anisotropic layer B1 had a slow axis in a direction orthogonal to the rubbing direction. The retardation value (Re550) at 550 nm was 150 nm. When the average tilt angle was measured by applying the crystal rotation method, the tilt angle of the lower alignment film interface was 45 °, the tilt angle of the upper air interface side was 45 °, and the average tilt angle was 45 °. It was found that the film was uniformly tilted.
────────────────────────────────
Coating liquid composition of optically anisotropic layer B1 ─────────────────────────────────
The following discotic liquid crystalline compound 32.6% by mass
Cellulose acetylate butyrate 0.7% by mass
Modified trimethylolpropane triacrylate 3.2% by mass
0.4% by mass of the following sensitizer
1.1% by mass of the following photopolymerization initiator
Methyl ethyl ketone 62.0% by mass
0.03 mass% of the following fluorine-containing compounds
────────────────────────────────

An optically anisotropic layer C1 functioning as a third optically anisotropic layer was used as a transparent support with a triacetylcellulose film having a thickness of 60 μm. The Rth value of the triacetyl cellulose film at 589.3 nm measured with a birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instruments) was 80 nm. The optically anisotropic layer B1 produced as described above and this triacetylcellulose film were bonded with an adhesive to obtain a laminate of the optically anisotropic layer B1 and the optically anisotropic layer C1.
An optically anisotropic layer A1 made of an uniaxially stretched Arton film (manufactured by JSR) was used as the second optically anisotropic layer. The optical axis was parallel to the film plane, the retardation value measured at 550 nm was 260 nm, and the Nz factor was 1.0. The laminate of the optically anisotropic layer B1 and the optically anisotropic layer C1 produced above and the ARTON film (optically anisotropic layer A1) were bonded together with an adhesive. At this time, the optically anisotropic layer A1, the optically anisotropic layer B1, and the optically anisotropic layer C1 are arranged in this order, and the slow axes of the optically anisotropic layer A1 and the optically anisotropic layer B1 intersect each other by 60 °. It was pasted together.

(Production of elliptically polarizing plate)
A roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizing film. A 3% aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) was bonded to a saponified triacetyl cellulose film as an adhesive to obtain a polarizing plate having both surfaces protected by triacetyl cellulose. The Rth value of the triacetyl cellulose film used here was 30 nm.

  Subsequently, the produced retardation plate (laminated body of optically anisotropic layer A1, optically anisotropic layer B1 and optically anisotropic layer C1) and a polarizing plate were bonded with an adhesive to prepare an elliptically polarizing plate. At this time, the optically anisotropic layer A1 and the polarizing plate are bonded so that they are in contact with each other, and the angle between the transmission axis of the polarizing plate and the slow axis of the optically anisotropic layer A1 and the optically anisotropic layer B1 is 75 °. 15 °. That is, the produced elliptically polarizing plate was an elliptically polarizing plate having the layer structure shown in FIG. 1 and having β of 15 ° and α of 60 ° in FIG.

[Example 2]
(Production of retardation plate)
In the same manner as in Example 1, a polymer dilution liquid having the above structure was applied on a glass substrate to form a film. The surface of this film was rubbed (rubbing with a rubbing cloth rotating at 2000 rpm) to obtain an alignment film. Next, using the coating liquid having the same composition as that used in the production of the optically anisotropic layer B1 in Example 1, the optically anisotropic layer B2 (first film) having a thickness of 2.55 μm as in Example 1. Optically anisotropic layer). The optically anisotropic layer B2 had a slow axis in the direction orthogonal to the rubbing direction. The retardation value (Re550) at 550 nm was 150 nm. When the average tilt angle is measured by applying the crystal rotation method, the discotic liquid crystal molecules are uniform with a tilt angle of 80 ° at the lower alignment film interface, a tilt angle of 80 ° at the upper air interface side, and an average tilt angle of 80 °. It was found that it was tilted.

  A retardation plate and an elliptically polarizing plate were produced in the same manner as in Example 1 except that the produced optically anisotropic layer B2 was used instead of the optically anisotropic layer B1. That is, an elliptically polarizing plate having the same layer structure as shown in FIG. 1 and having β of 15 ° and α of 60 ° in FIG. 2 was produced.

[Example 3]
In the same manner as in Example 1 (however, the coating amount is different), an optically anisotropic layer B1 having a thickness of 2.42 μm (the discotic liquid crystal molecules are uniformly tilted at an upper and lower interface tilt angle of 45 ° and an average tilt angle of 45 °). Two oriented layers (retardation at 550 nm was 75 nm) were prepared on a glass substrate. A retardation plate in the same manner as in Example 1 except that the laminate (total retardation is 150 nm) obtained by laminating the two optically anisotropic layers B1 is used instead of the optically anisotropic layer B1. , And an elliptically polarizing plate were produced. That is, the produced elliptically polarizing plate has the same layer configuration as shown in FIG. 1 (however, the first optical anisotropic layer is composed of two layers), and β in FIG. 2 is 15 °, α Was an elliptically polarizing plate of 60 °.

[Example 4]
In the same manner as in Example 1 (however, the coating amount is different), an optically anisotropic layer B1 having a thickness of 2.42 μm (the tilt angle of the upper and lower interfaces is 45 °, the average tilt angle is 45 °, uniform tilt orientation, at 550 nm) Retardation is 75 nm) and in the same manner as in Example 2 (however, the coating amount is different), and an optically anisotropic layer B2 having a thickness of 1.28 μm (the tilt angle at the upper and lower interfaces is 80 °, and the average tilt angle is 80 °). And uniform gradient orientation, and the retardation at 550 nm was 75 nm). A retardation plate and an ellipse are formed in the same manner as in Example 1 except that the laminate of the produced optically anisotropic layers B1 and B2 (as a whole, the retardation is 150 nm) is used instead of the optically anisotropic layer B1. A polarizing plate was produced. That is, the produced elliptically polarizing plate has the same layer configuration as shown in FIG. 1 (however, the first optical anisotropic layer is composed of two layers), and β in FIG. 2 is 15 °, α Was an elliptically polarizing plate of 60 °.

[Example 5]
The surface of a triacetyl cellulose film having an Rth of 40 nm is saponified, and a diluted solution of polyvinyl alcohol (MP-203 manufactured by Kuraray Co., Ltd.) is applied thereon to form a film, and a rubbing process is performed on the film surface. Thus, an alignment film was obtained. On the rubbing-treated surface of this alignment film, a coating solution having the following composition is spin-coated, dried and heated (alignment aging), and further irradiated with ultraviolet rays to form a second optically anisotropic layer having a thickness of 1.73 μm. A2 was formed. The optically anisotropic layer A2 had a slow axis in the rubbing direction. The retardation value (Re550) at 550 nm was 260 nm, and Nz was 1.0. When the average tilt angle was measured by applying the crystal rotation method, it was found that the average tilt angle in the film was horizontally oriented substantially at 0 °.
────────────────────────────
Composition of coating solution for optically anisotropic layer A2────────────────────────────
The following rod-like liquid crystalline compound 14.5% by mass
0.15% by mass of the above sensitizer
0.29% by mass of the photopolymerization initiator
Methyl ethyl ketone 85.06 mass%
0.03 mass% of the above fluorine-containing compound
─────────────────────────────

  A laminate of the optically anisotropic layer B2 and the optically anisotropic layer C1 produced in the same manner as in Example 2 and the optically anisotropic layer A2 were bonded together with an adhesive. At this time, the optically anisotropic layer A2, the optically anisotropic layer B2, and the optically anisotropic layer C1 are arranged in this order, and the slow axes of the optically anisotropic layer A2 and the optically anisotropic layer B2 intersect each other by 60 °. It was pasted together.

(Production of elliptically polarizing plate)
The polarizing plate is a surface that is protected on only one side with triacetylcellulose, and the surface of the polarizing plate that is not protected (polarizing film made of stretched polyvinyl alcohol) and the optically anisotropic layer A2 (triacetylcellulose film surface) ) Were bonded with an optically isotropic adhesive to produce an elliptically polarizing plate. At this time, the angles formed by the transmission axis of the polarizing plate and the slow axes of the optically anisotropic layer A2 and the optically anisotropic layer B2 were 75 ° and 15 °, respectively. That is, the produced elliptically polarizing plate had the same layer configuration as shown in FIG. 1, and was an elliptically polarizing plate having β of 15 ° and α of 60 ° in FIG.

[Comparative Example 1]
In Example 1, in place of the optically anisotropic layer B1, a polymer liquid crystal is hybrid-aligned with an average tilt angle of 24 ° (upper interface tilt angle 3 ° / lower interface tilt angle 44 °), manufactured by Mitsubishi Nippon Steel. A retardation plate and an elliptically polarizing plate were produced in the same manner except that the NH film was used.

[Comparative Example 2]
In the same manner as in Example 1, a polymer dilution liquid having the above structure was applied on a glass substrate to form a film. The surface of this film was rubbed (rubbing with a rubbing cloth rotating at 500 rpm) to obtain an alignment film. Next, an optically anisotropic layer B3 having a thickness of 20 μm was formed in the same manner as in Example 1 by using a coating liquid having the same composition as that used in the production of the optically anisotropic layer B1 in Example 1. The optically anisotropic layer B3 had a slow axis in the direction orthogonal to the rubbing direction. The retardation value (Re550) at 550 nm was 150 nm. When the average tilt angle was measured using the crystal rotation method, the tilt angle at the lower alignment film interface was 20 °, the tilt angle at the upper air interface side was 20 °, and the average tilt angle was 20 °. I found out.

  A retardation plate and an elliptically polarizing plate were produced in the same manner as in Example 1 except that the produced optically anisotropic layer B3 was used instead of the optically anisotropic layer B1.

[Comparative Example 3]
In Example 5, a retardation plate and an elliptically polarizing plate were produced in the same manner except that an Arton film having a retardation of 150 nm was used instead of the optically anisotropic layer B2.

[Evaluation]
(Viewing angle measurement)
ECB transflective display devices each incorporating the elliptically polarizing plates produced above were produced. First, a pair of 0.7 mm thick glass substrates were arranged to face each other with a gap of 4 μm. An ITO electrode was formed on the glass substrate on the observer side, and an aluminum reflective electrode with projections and depressions was formed on the other glass substrate as a counter electrode of the ITO electrode. An alignment film obtained by rubbing the surface of the polyimide film was formed on the opposing surfaces of the upper and lower substrates. The rubbing angles of the alignment films on the upper and lower substrates were made parallel (twist angle 0 degree). A nematic liquid crystal having Δn = 0.086 and a dielectric anisotropy of +10.0 was injected into the gap of the glass substrate to produce a liquid crystal cell (LC).

  Using this liquid crystal cell, a liquid crystal display device having a layer structure shown in FIG. 3 was produced. Below the liquid crystal cell LC, the elliptically polarizing plate prepared in Examples 1 to 5 (in the figure, the first optical anisotropy is B, the second optical anisotropy layer is A, the third optical anisotropy) The direction of the director of the first optically anisotropic layer B1 or B2 (direction perpendicular to the slow axis) is the rubbing direction of the upper and lower substrates of the liquid crystal cell LC. It was arranged so that it was parallel. That is, the direction in which the director of the liquid crystal molecules in the liquid crystal cell LC during black display is projected onto the plane parallel to the layer, and the director of the discotic liquid crystal molecules uniformly tilted in the first optically anisotropic layer. Bonding was performed so that the direction projected on the plane parallel to the layers was substantially parallel. Similarly, the elliptically polarizing plates prepared in Comparative Examples 1 to 3 were arranged to prepare a liquid crystal display device.

  In addition, it is the same as the ARTON film used in the examples, and each of the optically anisotropic layer D having a retardation of 150 nm and the optically anisotropic layer E having a thickness of 260 nm has a slow axis of D and E of 60 °. Laminate so as to cross each other, and further laminate a linearly polarizing plate P2 so that the transmission axis and the slow axis of the optically anisotropic layer E intersect at 15 °. The slow axis of the optically anisotropic layer D was arranged in parallel with the rubbing direction of the upper and lower substrates of the liquid crystal cell LC. FIG. 3 shows the relationship between the slow axis d of the optically anisotropic layer D on the upper side of the liquid crystal cell, the slow axis e of the optically anisotropic layer E, and the transmission axis p2 of the polarizing plate P2. In the manufactured liquid crystal display device, the crossing angle β between the slow axis e of the optically anisotropic layer E and the transmission axis p2 of the linearly polarizing plate P2 is 15 °, and the slow axis e of the optically anisotropic layer E is And the slow angle d of the optically anisotropic layer D was 60 °.

  Subsequently, transmission luminance from the lower side of the liquid crystal display device was measured using a spectral radiance meter under ordinary indoor fluorescent lamp illumination. At this time, with the liquid crystal display device placed horizontally, the polar angle is fixed every 10 ° in the direction of 0 to 80 ° from the normal line, and the azimuth angle of the liquid crystal display device is changed every 10 ° at each angle. The brightness was measured while the liquid crystal display device was on and off, and the contrast ratio, which is the ratio of the brightness when the liquid crystal display device was on and off, was calculated. The values obtained by adding the contrast ratios for all polar angles and azimuths in all directions were scored and listed in Table 1. The larger this value is, the larger the contrast ratio is with a wide viewing angle, and the viewing angle characteristics of the display device with a wide viewing angle can be evaluated.

  From the results shown in Table 1, the liquid crystal display device having the elliptically polarizing plate of Examples 1 to 5 having the optically anisotropic layer of the present invention is a liquid crystal having the elliptically polarizing plate of Comparative Examples 1 to 3 each having a corresponding configuration. It can be seen that the contrast ratio is higher than that of the display device and the viewing angle characteristics are improved.

It is sectional drawing which shows the typical aspect of the elliptically polarizing plate of this invention. It is a top view which shows the direction of the slow axis of the optically anisotropic layer of the elliptically polarizing plate of FIG. 1, and the direction of the polarization transmission axis of a polarizing film. It is a schematic sectional drawing which shows the layer structure of the liquid crystal display device produced in the Example. FIG. 4 is a plan view showing the direction of the slow axis of the upper optically anisotropic layer (E, D) of FIG. 3 and the direction of the polarization transmission axis of the upper polarizing film (P2).

Explanation of symbols

A Second optically anisotropic layer B First optically anisotropic layer C Third optically anisotropic layer P Linearly polarizing film P1 Lower linearly polarizing film P2 Upper linearly polarizing film T1 Protective film T2 for linearly polarizing film Protective film LC of linearly polarizing film Liquid crystal cell D Upper optical anisotropic layer E composed of arton film (150 nm) Upper optical anisotropic layer a composed of arton film (260 nm) a slow axis of the second optical anisotropic layer b Slow axis of the first optically anisotropic layer d Slow axis of the upper optically anisotropic layer made of the Arton film (150 nm) e Slow axis p of the upper optically anisotropic layer made of the Arton film (260 nm) _1, p ₂ polarization transmission axis

Claims (10)

The discotic liquid crystalline molecules are uniformly tilted nematically oriented with an average tilt angle of 35 to 85 ° with respect to the layer plane, and the tilt angle on one interface side in the layer is substantially equal to the tilt angle on the other interface side. An optically anisotropic layer having a phase difference of 80 to 200 nm at a wavelength of 550 nm. An optically anisotropic layer having two or more optically anisotropic layers, wherein at least one layer is the optically anisotropic layer according to claim 1. The first optical anisotropic layer which is the optical anisotropic layer according to claim 1, a phase difference at a wavelength of 550 nm is 200 to 350 nm, and an Nz factor (the following formula) is 0.5 to 2.0. A retardation plate having a second optically anisotropic layer.
Nz factor = (nx−nz) / (nx−ny)
[Where nx and ny are in-plane main refractive indexes, and nz is the main refractive index in the thickness direction. ] The retardation plate according to claim 3, wherein the second optically anisotropic layer is formed by horizontally aligning liquid crystalline molecules having positive optical anisotropy. The retardation plate according to claim 3, wherein the second optically anisotropic layer is made of a stretched polymer film. The retardation plate according to any one of claims 3 to 5, further comprising a third optical anisotropic layer having a thickness direction retardation Rth (the following formula) of 0 to 300 nm at a wavelength of 589.3 nm.
Rth = ((nx + ny) / 2−nz) × d
[Where nx and ny are in-plane main refractive indexes, nz is the main refractive index in the thickness direction, and d is the thickness (nm). ] The phase difference plate according to claim 6, wherein the third optically anisotropic layer is a layer formed of a material selected from liquid crystalline molecules, triacetylcellulose and / or cyclic polyolefin. The elliptically polarizing plate which has a polarizer and the phase difference plate of any one of Claims 3-7. A TN type or ECB type liquid crystal display device having the elliptically polarizing plate according to claim 8. The direction of the average axis of the liquid crystal molecule director in the liquid crystal cell when displaying black is projected on the plane parallel to the layer, and the direction of the discotic liquid crystal molecules uniformly tilted in the first optically anisotropic layer The liquid crystal display device according to claim 9, wherein a direction projected onto the parallel plane is substantially parallel.

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