JP2005062668A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display whose visibility angle characteristic is improved. <P>SOLUTION: The liquid crystal display includes a 1st optical anisotropic layer, a 2nd optical anisotropic layer, a polarizing film, and a driving liquid crystal cell, and the 1st optical anisotropic layer has a layer formed of a composition containing at least a discotheque liquid crystal compound. In this layer, the disk surface of a discotheque liquid-crystalline molecule slants to a layer plane and the retardation (Re) value of the 1st optical anisotropic layer at a waveform of 550 nm which is defined by an equation (I) Re=(n<SB>x</SB>-n<SB>y</SB>)×d (n<SB>x</SB>is the refractive index in the layer plane in a phase-delay-axis direction, n<SB>y</SB>is the refractive index in the layer plane in a phase-advance-axis direction, and (d) is the thickness of the optical anisotropic layer); and the direction of an axis formed by projecting on the layer plane the optical axis of the discotheque liquid crystal molecule in the 1st optical anisotropic layer is not orthogonal to the mean direction of an axis formed by projecting on the layer plane of the optical axis of the liquid crystal molecule in the driving liquid crystal cell in black display. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device useful as various displays (for example, reflective and transflective liquid crystal display devices used for OA equipment and portable terminals).

  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. Reflective and transflective liquid crystal display devices usually have a λ / 4 plate. 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 has also been disclosed (see, for example, Patent Documents 5 to 7).

When a λ / 4 plate is used in a reflective liquid crystal display device, it is designed to maintain about a quarter wavelength at the time of vertical incidence in order to obtain a dark display. However, since the reflection type liquid crystal display device normally uses outside light such as room light or outdoor light, the light is not only incident vertically but rather is incident from an oblique direction. Even when the reflection type liquid crystal display device is designed as described above, when light is incident obliquely, a deviation from a quarter wavelength occurs, so that the contrast is lowered depending on the viewing angle. Further, in the transmission mode of the transflective liquid crystal display device, the contrast is lowered when viewed from an oblique direction due to the refractive index anisotropy of the liquid crystal molecules. As means for improving such viewing angle dependency, a technique using a compensation element including a liquid crystal film in which nematic hybrid alignment of liquid crystal molecules exhibiting positive uniaxiality is fixed is disclosed (for example, Patent Document 6). And 7) In the transflective liquid crystal display device using the elliptically polarizing plate including the liquid crystal film, there is a problem that the viewing angle in a specific direction is not improved.
JP-A-10-68816 JP-A-10-90521 JP-A-10-68816 JP-A-10-90521 JP 2001-4837 A JP 2002-31717 A JP 2002-31426 A

  An object of the present invention is to provide a liquid crystal display device with improved viewing angle characteristics.

The problems of the present invention have been solved by the following means.
(1) A liquid crystal display device including a first optical anisotropic layer, a second optical anisotropic layer, a polarizing film, and a driving liquid crystal cell, wherein the first optical anisotropic layer is at least a discotic liquid crystal. The disc surface of the discotic liquid crystal molecule is inclined with respect to the layer plane, and the first optically anisotropic layer has the following formula ( The retardation (Re) value at a wavelength of 550 nm defined by I) is 70 to 200 nm, and the optical axis of the discotic liquid crystalline molecule in the first optically anisotropic layer is projected onto the layer plane. A liquid crystal display device characterized in that the direction and the average direction of the axes obtained by projecting the optical axes of the liquid crystal molecules in the driving liquid crystal cell during black display onto the layer plane are not orthogonal.
_{Re = (n x -n y)} × d (I)
(Wherein, n _x is a refractive index in a slow axis direction of the optically anisotropic layer plane, n _y is a refractive index in a fast axis direction of the optically anisotropic layer plane, d is the optical anisotropy The thickness of the layer.)
(2) The liquid crystal display device according to (1), wherein an angle formed by the disc surface of the discotic liquid crystalline molecule and the layer plane changes in the layer depth direction.

(3) The liquid crystal display device according to (1) or (2), wherein the second optically anisotropic layer has an in-plane retardation value of 200 to 300 nm at a wavelength of 550 nm.
(4) The liquid crystal display according to any one of (1) to (3), wherein the second optically anisotropic layer includes a stretched polymer film, and an in-plane retardation value at a wavelength of 550 nm is 200 to 300 nm. apparatus.
(5) The liquid crystal display device according to any one of (1) to (3), wherein the second optically anisotropic layer includes a rod-like liquid crystal compound, and an in-plane retardation value at a wavelength of 550 nm is 200 to 300 nm. .
(6) The liquid crystal display device according to any one of (1) to (5), wherein the first optically anisotropic layer has two optically anisotropic layers formed from a composition containing a discotic liquid crystal compound. .
(7) The in-plane slow axis direction of each of the two layers is substantially parallel, and the total Re value of each optically anisotropic layer defined by the formula (I) is 70 to The liquid crystal display device according to (6), which is in a range of 200 nm.
(8) The liquid crystal display device according to any one of (1) to (7), wherein the liquid crystal display device is in an ECB or TN mode.
(9) The liquid crystal display device is a transflective type, and the first optical anisotropic layer, the second optical anisotropic layer, and the polarizing film are more than the driving liquid crystal cell when viewed from the observer side. The liquid crystal display device according to any one of (1) to (8), which is located behind.

  According to the present invention, a liquid crystal display device with improved viewing angle characteristics can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail.
[Liquid Crystal Display]
The liquid crystal display device of the present invention includes any aspect such as a reflective type, a transflective type, and a transmissive type liquid crystal display device. The liquid crystal display device of the present invention includes a specific first optical anisotropic layer, a second optical anisotropic layer, a linearly polarizing film, and a driving liquid crystal cell. As long as it has these essential members, the liquid crystal display device of the present invention is not particularly limited with respect to other configurations, and if necessary, other polarizing plates, other retardation plates, reflective layers, light diffusion layers, You may have members, such as a backlight, a front light, a light control film, a light-guide plate, a prism sheet, and a color filter.

  The driving 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 having the property of aligning the liquid crystal itself, a substrate itself lacking alignment ability, but a transparent substrate provided with an alignment film having the property of aligning liquid crystal, etc. Can also 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 in contact with the liquid crystal layer, 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 crystalline compounds, high-molecular liquid crystalline compounds, and mixtures thereof that can constitute various liquid crystal cells. Moreover, a pigment | dye, a chiral agent, a non-liquid crystalline compound, etc. can also be added to these in the range which does not impair liquid crystallinity.

  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 arrangement positions of the first optically anisotropic layer, the second optically anisotropic layer, and the linearly polarizing film are not particularly limited, but these members preferably function as an elliptically polarizing plate as a whole. In addition, it is preferable that these essential members are arranged on the same side with the driving liquid crystal cell as the center. It may be arranged on either the upper side or the lower side, or may be arranged on both sides.

  The liquid crystal display device according to the present invention uses at least one elliptically polarizing plate made of a laminate of a first optically anisotropic layer, a second optically anisotropic layer, and a linearly polarizing film. The direction of the axis in which the optical axis of the discotic liquid crystal molecule forming the first optically anisotropic layer is projected onto the layer plane, and the optical axis of the liquid crystal molecule in the driving liquid crystal cell during black display are projected onto the layer plane. The average direction of the axes is not orthogonal. Specifically, the direction of the axis in which the optical axis of the discotic liquid crystal molecules forming the first optically anisotropic layer is projected onto the layer plane, and the optical axis of the liquid crystal molecules in the driving liquid crystal cell during black display are expressed. The angle formed by the average direction of the axes projected on the layer plane is preferably within 45 °, more preferably within 30 °, and most preferably within 15 °. The director of the liquid crystal molecules in the driving 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.

  The liquid crystal display device in the present invention is preferably a reflective type or a transflective type liquid crystal display device. A reflective liquid crystal display device usually 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. When the present invention is applied to a reflective liquid crystal display device, the first and second optically anisotropic layers are disposed between the reflector and the liquid crystal cell or between the liquid crystal cell and the linearly polarizing film. On the other hand, a transflective liquid crystal display device usually has a liquid crystal cell, a polarizing plate disposed closer to the viewer than the liquid crystal cell, and at least one plate disposed between the polarizing plate and the liquid crystal cell. A retardation plate and at least a transflective layer disposed behind the liquid crystal layer as viewed from the observer, and at least one retardation plate behind the transflective layer as viewed from the observer; It has a polarizing plate. 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. When the present invention is applied to a transflective liquid crystal non-display device, the first and second optically anisotropic layers are arranged between the liquid crystal cell and the polarizing plate closer to the observer, or between the liquid crystal cell and the observer side. It arrange | positions between the polarizing plates farther from.

  The liquid crystal display device of the present invention preferably has a TN mode or ECB mode driving liquid crystal cell. Further, it is preferably a transflective liquid crystal display device. In such an embodiment, the first and second optical anisotropic layers are further used behind the liquid crystal cell when viewed from the observer side. preferable.

Hereinafter, the first and second optically anisotropic layers and the linearly polarizing film used in the liquid crystal display device of the present invention will be described in detail, and the relationship thereof will be described in detail.
[First optically anisotropic layer]
In the present invention, the first optically anisotropic layer has a layer formed from a composition containing at least a discotic liquid crystalline compound. Discotic liquid crystal molecules generally have an optically negative uniaxial property. The discotic liquid crystalline molecules contained in the first optically anisotropic layer are oriented with the disc surface tilted with respect to the layer plane, and the tilt angle (of the layer plane and the discotic liquid crystalline molecules). It is preferable that the angle formed with the disk surface is changed (hybrid orientation) in the depth direction of the optically anisotropic layer. The optical axis of the discotic liquid crystalline molecule exists in the normal direction of the disk surface. The discotic liquid crystalline molecule has birefringence in which the refractive index in the disc surface direction is larger than the refractive index in the optical axis direction. The first optically anisotropic layer is preferably formed by aligning discotic liquid crystalline molecules with an alignment film and fixing the aligned discotic liquid crystalline molecules. The discotic liquid crystalline molecules are preferably fixed by a polymerization reaction. The average angle formed by the disc surface of the discotic liquid crystal molecules and the phase difference plate plane is preferably in the range of 15 to 85 °, and more preferably in the range of 25 to 75 °.

The in-plane retardation value (Re) in the normal direction of the layer plane of the optically anisotropic layer is defined by the following formula (I).
_{Re = (n x -n y)} × d (I)
Wherein, n _x is a refractive index in a slow axis direction in the plane of the optically anisotropic layer, n _y is a refractive index in a fast axis direction in the plane of the optically anisotropic layer, d is the optical This is the thickness of the anisotropic layer.
The Re value of the first optically anisotropic layer at a wavelength of 550 nm is in the range of 70 to 200 nm, and preferably in the range of 80 to 180 nm.

  The first optically anisotropic layer may be composed of a plurality of layers, and in such an embodiment, different optically anisotropic layers other than the layer in which the discotic liquid crystalline molecules are aligned may be included. The total Re value of the laminated body may be in the above range.

  Discotic liquid crystalline molecules are disclosed in 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)). 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. Discotic liquid crystalline molecules having a discotic core, a linking group and a polymerizable group are described in JP-A No. 2002-236215.

  The optically anisotropic layer can be formed by applying a coating liquid containing a discotic liquid crystalline compound and, if necessary, a polymerizable initiator and optional components on the alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), 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 thickness of the optically anisotropic layer is preferably 0.5 to 100 μm, and more preferably 0.5 to 30 μm.

The aligned discotic liquid crystal molecules are fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and 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. Light irradiation for polymerization of discotic liquid crystalline molecules is preferably performed using ultraviolet rays. Irradiation energy is preferably 20~5000mJ / 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. A protective layer may be provided on the optically anisotropic layer.

  In forming the optically anisotropic layer, by using an additive as a coating aid, 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 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. The compound used as the additive is not particularly limited, and may be a low molecular compound or a high molecular compound. It is preferable to use a fluorine-containing surfactant or a silicon compound. By these additives, the unevenness of the optical characteristics of the optically anisotropic layer is reduced, and the unevenness of the display characteristics when used in a liquid crystal display device is improved.

  The first optically anisotropic layer may be formed by laminating two or more optically anisotropic layers containing discotic liquid crystals. That is, when the discotic liquid crystal layer is formed on the support, the coating amount may be adjusted so that a desired retardation is manifested by a single coating, The coating amount may be adjusted so as to be reduced, and a desired retardation may be finally expressed by laminating them. In the laminated body of optically anisotropic layers including two or more discotic liquid crystals, it is preferable that the slow axis directions in each plane are substantially parallel.

In the case where the optically anisotropic layer containing the discotic liquid crystal is composed of two or more laminates, examples of the production method include the following.
An optically anisotropic layer containing a discotic liquid crystal formed on a transparent support and an optically anisotropic layer containing a discotic liquid crystal formed on a separately prepared transparent support are bonded with an adhesive or the like. . It is preferable that two layers of the same optically anisotropic layer obtained by adjusting the coating amount so as to be half of the desired retardation are laminated to express the desired retardation, but a plurality having different retardations. These optically anisotropic layers may be laminated to develop a desired retardation. The transparent support may be optionally peeled off during or after the bonding process.
An optically anisotropic layer containing two or more discotic liquid crystals may be sequentially formed on the same support. Specifically, after the discotic liquid crystal molecules are aligned and fixed on the transparent support, the discotic liquid crystal molecules are further aligned and fixed on the transparent support to develop a desired retardation. It is preferable to express a desired retardation by stacking two discotic liquid crystal layers, but three or more layers may be stacked. The transparent support may be optionally peeled after the laminate is formed.

  1A is a single-layer structure, FIGS. 1B and 1C are cross-sectional schematic views of a first optically anisotropic layer having a two-layer structure, and a schematic view of the orientation state of discotic liquid crystalline molecules. FIG. The first optically anisotropic layer may be composed of a single layer as shown in FIG. 1 (a), or may be composed of two layers as shown in FIGS. 1 (b) and (c). Good. In an embodiment composed of a single layer, as shown in FIG. 1A, the angle formed by the disc surface of the discotic liquid crystalline molecule and the layer plane increases from the lower interface in the depth direction of the layer toward the upper interface. It may be decreased or decreased. Further, in the embodiment composed of two layers, as shown in FIG. 1B, two layers having the same change tendency in the depth direction of the layer formed by the angle between the disc surface of the discotic liquid crystalline molecules and the layer plane are formed. Alternatively, as shown in FIG. 1 (c), two layers having opposite changes in the depth direction of the layer having the angle may be stacked.

[Alignment film]
The alignment film has a function of defining the alignment direction of the liquid crystalline molecules forming the optically anisotropic layer. The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known. The alignment film is preferably formed by polymer rubbing treatment. Polyvinyl alcohol is a preferred polymer. Particularly preferred is a modified polyvinyl alcohol to which a hydrophobic group is bonded. Since the hydrophobic group has an affinity with the discotic liquid crystalline molecule of the optically anisotropic layer, the discotic liquid crystalline molecule can be uniformly aligned by introducing the hydrophobic group into polyvinyl alcohol. The hydrophobic group is bonded to the main chain end or side chain of polyvinyl alcohol. The hydrophobic group is preferably an aliphatic group having 6 or more carbon atoms (preferably an alkyl group or an alkenyl group) or an aromatic group. When a hydrophobic group is bonded to the main chain terminal of polyvinyl alcohol, it is preferable to introduce a linking group between the hydrophobic group and the main chain terminal. Examples of the linking group include —S—, —C (CN) R ¹ —, —NR ² —, —CS—, and combinations thereof. R ¹ and R ² are each a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (preferably an alkyl group having 1 to 6 carbon atoms).

When a hydrophobic group is introduced into the side chain of polyvinyl alcohol, a part of the acetyl group (—CO—CH ₃ ) of the vinyl acetate unit of polyvinyl alcohol is substituted with an acyl group having 7 or more carbon atoms (—CO—R). ³ ). R ³ is an aliphatic group or aromatic group having 6 or more carbon atoms. Commercially available modified polyvinyl alcohol (eg, MP103, MP203, R1130, manufactured by Kuraray Co., Ltd.) may be used. The saponification degree of the (modified) polyvinyl alcohol used for the alignment film is preferably 80% or more. The degree of polymerization of (modified) polyvinyl alcohol is preferably 200 or more. The rubbing process is performed by rubbing the surface of the alignment film several times in a certain direction with paper or cloth. It is preferable to use a cloth in which fibers having uniform length and thickness are uniformly planted. Even if the discotic liquid crystalline molecules in the optically anisotropic layer are aligned using the alignment film, the alignment state of the discotic liquid crystalline molecules can be maintained even if the alignment film is removed. That is, the alignment film is indispensable in the production of the retardation plate in order to orient the discotic liquid crystalline molecules, but is not essential in the produced retardation plate. When the alignment film is provided between the transparent support and the optically anisotropic layer, it is preferable to further provide an undercoat layer (adhesive layer) between the transparent support and the alignment film.

  When an optically anisotropic layer composed of two or more liquid crystalline molecules is laminated, the plurality of optically anisotropic layers may be sequentially formed on the same support. At that time, an alignment film may be provided sequentially between the optically anisotropic layers, or an alignment film function may be provided in the components constituting the optically anisotropic layer without providing an alignment film separately between the optically anisotropic layers. By adding a molecule having the optically anisotropic layer, the optically anisotropic layer laminated on the optically anisotropic layer can be brought into a desired orientation state. The material of the alignment film can be selected according to the required optical properties and the type of liquid crystalline molecules used.

  The layer formed by fixing the nematic hybrid alignment of the discotic liquid crystal compound is asymmetrical with respect to the layer plane because the tilt angle of the liquid crystal molecules is different between above and below the thickness direction. Therefore, for example, the viewing angle improvement effect when used in a liquid crystal display device differs depending on whether the liquid crystal molecules closer to the polarizing plate have a higher tilt angle or a lower tilt angle. The tilt angle on the support side and the air interface side of the layer formed by fixing the nematic hybrid orientation can be controlled by selecting an air interface alignment agent to be added to the alignment film or layer. The side can be at a high tilt angle and vice versa. Furthermore, even if the same alignment film and air interface alignment agent are used, a hybrid alignment film in which the high tilt angle side and the low tilt angle side are turned upside down can be formed by transferring it to another substrate after being formed on a temporary support. Can be obtained.

[Second optically anisotropic layer]
The liquid crystal display device of the present invention has the first optical anisotropic layer and further a second optical anisotropic layer. The in-plane retardation value (Re) at a wavelength of 550 nm in the normal direction of the layer plane of the second optically anisotropic layer is preferably 200 to 300 nm, and more preferably 220 to 280 nm.

  In the present invention, the optical axis of the second optically anisotropic layer may be inclined with respect to the layer plane as in the case of the first optically anisotropic layer. Are preferably parallel. Such an optically anisotropic layer may be a stretched polymer film or a layer formed by immobilizing a substantially horizontal (homogeneous) aligned liquid crystal compound.

  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 10 °. The liquid crystalline molecules are preferably fixed in an aligned state, and more preferably fixed by polymerization. As long as the optical characteristics are satisfied, the type of the liquid crystalline compound is not particularly limited. For example, after forming a low molecular weight liquid crystalline compound in a nematic orientation in a liquid crystal state, an optically anisotropic layer obtained by fixing by photocrosslinking or thermal crosslinking, or after forming a polymer liquid crystalline compound in a nematic orientation in a liquid crystal state, An optically anisotropic layer obtained by fixing the orientation by cooling can be used. In the present invention, even when a liquid crystalline compound is used for the optically anisotropic layer, the optically anisotropic layer is a layer formed by fixing the compound by polymerization or the like, and thus becomes a layer. After that, it is no longer necessary to show liquid crystallinity.

  In an embodiment in which the second optically anisotropic layer is formed by fixing the orientation of liquid crystalline molecules, the second optically anisotropic layer can be formed from a composition containing a liquid crystalline compound. As the liquid crystal compound, a rod-like liquid crystal compound or a discotic liquid crystal compound is preferably used, and a rod-like liquid crystal compound is particularly preferably used. The liquid crystalline compound is preferably fixed in a nematic alignment state, and more preferably fixed by a polymerization reaction. Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only the above low-molecular liquid crystalline compounds but also high-molecular liquid crystalline compounds can be used. It is more preferable to fix the alignment of the rod-like liquid crystal compound by polymerization. As the polymerizable rod-like liquid crystal compound, Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 5,622,648, US Pat. No. 5,770,107, International Publication No. WO 95/22586, No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, No. 7-110469, The compounds described in JP-A No. 11-80081 and JP-A No. 2001-328773 can be used. The method for fixing the alignment of the liquid crystal compound is the same as the example given in the description of the fixation of the discotic liquid crystal compound.

  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 uniaxial or biaxial stretching. Uniaxial stretching is preferably longitudinal uniaxial stretching utilizing the difference in peripheral speed between two or more rolls, or tenter stretching in which both sides of the polymer film are gripped and stretched in the width direction. Biaxial optical anisotropy may be developed by stretching the polymer film in the longitudinal direction and the transverse direction. 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 400 nm, and most preferably 30 to 100 nm.

Whether the second optically anisotropic layer is a liquid crystal film or a polymer film, the Nz factor defined by the following formula is preferably in the range of 0.5 to 2.0.
_{Nz = (n x -n z)} / (n x -n y)
In the formula, nx and ny are in-plane main refractive indexes of the optically anisotropic layer, and nz is a main refractive index in the thickness direction.

[Lamination of optically anisotropic layer]
The slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer are preferably laminated so that they are neither parallel nor orthogonal. Specifically, the angle formed by the slow axis of the first optically anisotropic layer and the slow axis of the second optically anisotropic layer is preferably 5 to 85 ° and is preferably 10 to 80 °. More preferably, the angle is 15 to 75 °.

When the retardation of the first optically anisotropic layer and the second optically anisotropic layer and Re ₁ and Re _2, respectively, | it is in the range of 0 to 100 nm | Re ₁ -Re _2/2 Is preferable, and the range of 0 to 80 nm is more preferable.

Examples of the method for producing a laminated retardation plate composed of the first optically anisotropic layer and the second optically anisotropic layer include the following examples.
The first optically anisotropic layer formed on the transparent support and the separately prepared second optically anisotropic layer can be bonded with an adhesive or the like by a known method. The transparent support may be optionally peeled off during or after the bonding process.
When the second optically anisotropic layer is made of a polymer film, the film may be used as a support for forming the first optically anisotropic layer. Specifically, a laminated phase difference plate is obtained by forming an alignment film on a polymer film that exhibits optical anisotropy by stretching, and forming a first optical anisotropic layer thereon.
When the second optically anisotropic layer is a layer in which a liquid crystalline compound is fixed, the first optically anisotropic layer and the second optically anisotropic layer are sequentially formed on the same support. It may be formed. Specifically, after forming the second optical anisotropic layer in which the liquid crystal molecules are aligned and fixed on the transparent support, the discotic liquid crystal molecules are aligned and fixed on the second optically anisotropic layer, whereby the laminated retardation plate is formed. can get. Further, after forming the first optical anisotropic layer containing the discotic liquid crystal, the second optical anisotropic layer may be formed thereon. The transparent support may be optionally peeled after the laminate is formed.

[Transparent support]
The first optical anisotropic layer or the second optical anisotropic layer may have a support, and may be sequentially formed on the same support as described above. The first and second optically anisotropic layers are composed of a support and a layer formed from a composition containing a liquid crystal compound, and exhibit the above desired optical characteristics as a whole. Also good. The support used is preferably transparent. 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 transparent support is preferably 10 to 500 μm, and more preferably 30 to 200 μm.

  In order to improve adhesion between the transparent 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 ray) is applied to the transparent support. Treatment, flame treatment, etc.). An ultraviolet absorber may be added to the transparent 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 transparent support, it is preferable to use a polymer film having a small wavelength dispersion. The transparent support preferably 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. Furthermore, the thickness direction retardation (Rth) defined by the following formula is preferably 100 nm or less, more preferably 80 nm or less, and most preferably 60 nm or less.
_{Rth = {(n x + n} y) / 2-n z} × d
In the formula, _nx and _ny are in-plane main refractive indices of the polymer film, _nz is the main refractive index in the thickness direction, and d is the thickness (nm) of the polymer film. The in-plane and thickness direction retardation values of the triacetyl cellulose film can be measured with a birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instruments).

  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. As the cyclic polyolefin, a polymer obtained by hydrogenation reaction of a ring-opening polymer of tetracyclododecene or a ring-opening copolymer of tetracyclododecene and norbornene described in JP-B-2-9619 Can be used from the series of Arton (manufactured by JSR), Zeonex, and Zeonore (manufactured by Nippon Zeon). The polymer film is preferably formed by a solvent cast method.

  On the other hand, a retardation plate in which in-plane retardation and thickness direction retardation are expressed by stretching a polymer film may be used as the support. Since the sum of the in-plane retardation of the retardation plate and the in-plane retardation of the discotic liquid crystal layer formed thereon may be within the Re range, the discotic liquid crystal layer can be thinned. preferable.

[Elliptically polarizing plate]
When the first optically anisotropic layer, the second optically anisotropic layer, and the linearly polarizing film are combined to form an elliptically polarizing plate, it can be easily used as a reflective or transflective liquid crystal display device. Can be incorporated into the device.

  The liquid crystal display device of the present invention includes an elliptically polarizing plate comprising a laminate of the first optically anisotropic layer, the second optically anisotropic layer, and the linearly polarizing film including the discotic liquid crystal. A preferred form of the elliptically polarizing plate is a linearly polarizing film, a second optically anisotropic layer, and a first optically anisotropic layer laminated in this order. The order to do is not asked.

  The angle formed by the slow axis of the first optical anisotropic layer containing the discotic liquid crystal and the slow axis of the second optical anisotropic layer is preferably in the range of 5 to 85 °. Furthermore, the angle formed by the slow axis of the first optically anisotropic layer and the transmission axis or absorption axis of the linearly polarizing film is 0 to 45 °, and the slow axis of the second optically anisotropic layer is The angle formed by the phase axis and the transmission axis or absorption axis of the linearly polarizing film is preferably 50 to 90 °. Alternatively, the angle formed by the slow axis of the first optically anisotropic layer and the transmission axis or absorption axis of the linearly polarizing film is 50 to 90 °, and the slow axis of the second optically anisotropic layer is The angle formed by the phase axis and the transmission axis or absorption axis of the linearly polarizing film is preferably 0 to 45 °. However, the angle is not limited to the above range, and it is arbitrarily determined so that a good display can be obtained in consideration of the Re value of each optically anisotropic layer and the parameters of the liquid crystal cell of the liquid crystal display device to be used. Can be adjusted. FIG. 2 shows a schematic cross-sectional view of a retardation plate in which the first optical anisotropic layer A and the second optical anisotropic layer B are laminated. FIG. 3 is a schematic cross-sectional view of an elliptically polarizing plate obtained by further laminating a linear polarizing film P. The linearly polarizing film P may be laminated on the first optically anisotropic layer A side or on the second optically anisotropic layer B side. However, as shown in FIG. 2 is preferably laminated on the optically anisotropic layer B side.

  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. When a protective film is used, 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 addition, the transparent support used for forming the optically anisotropic layer containing liquid crystal molecules and the second optically anisotropic layer made of a polymer film can function as a protective film on one side of the polarizing film. .

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.
[Example 1]
(Production of retardation plate)
A saponification treatment is performed on the surface of a 40 μm-thick triacetylcellulose film, and a coating solution having a composition of 20 parts by mass of the following modified polyvinyl alcohol, 1.0 part by mass of glutaraldehyde, 360 parts by mass of water, and 120 parts by mass of methanol. And dried with hot air at 80 ° C. to form a film having a thickness of 1 μm. Next, the surface of the formed film was rubbed to obtain an alignment film. The in-plane retardation (Re) of the triacetylcellulose film used here was 1 nm, and the retardation in the thickness direction (Rth) was 10 nm.

On the rubbing treatment surface of the formed alignment film, a coating solution having the following composition was applied with a wire bar.
─────────────────────────────────
Coating liquid composition of discotic liquid crystal layer ─────────────────────────────────
The following discotic liquid crystal (1) 32.6% by mass
Fluorine-containing compound (1) 0.12% by mass
Fluorine-containing compound (2) 0.03% by mass
The following modified trimethylolpropane triacrylate 3.2% by mass
Sensitizer below 0.4% by mass
The following photopolymerization initiator 1.1% by mass
Methyl ethyl ketone 62.6% by mass
─────────────────────────────────

  This was affixed to a metal frame and heated in a thermostatic chamber at 130 ° C. for 3 minutes to align the discotic liquid crystalline molecules. Next, using a 120 W / cm high-pressure mercury lamp at 130 ° C., UV irradiation is performed for 1 minute to polymerize the discotic liquid crystalline molecules to form an optically anisotropic layer having a thickness of 4.6 μm. did. The in-plane slow axis direction of the optically anisotropic layer was expressed in a direction orthogonal to the rubbing direction, and the in-plane retardation of the retardation plate A measured at 550 nm was 150 nm. In the layer, the angle formed by the disc plane of the discotic liquid crystal molecules and the support plane changes continuously in the thickness direction, and is 5 ° on the alignment film side and 85 ° on the air interface side. The angle was found to be 45 °. That is, it was found that the produced retardation plate A functions as the first optically anisotropic layer of the present invention.

  Arton film (manufactured by JSR) was uniaxially stretched to produce three types of retardation plates B, C, and D. The in-plane retardation at 550 nm was 258 nm, 98 nm, and 250 nm, respectively. In addition, the optical axes of these retardation plates were parallel to the film plane, and the Nz factor was 1.0.

(Ellipse polarizing plate)
A roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a linearly 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 triacetylcellulose film used here had a thickness of 40 μm, Re of 2 nm, and Rth of 20 nm.

  The prepared retardation plate A (first optical anisotropic layer), retardation plate B (second optical anisotropic layer), and polarizing plate (including a linearly polarizing film) are bonded together with an adhesive, and an elliptical shape is obtained. A polarizing plate was produced. Moreover, the phase difference plate C, the phase difference plate D, and the polarizing plate were bonded together with the adhesive, and the other elliptically polarizing plate was obtained.

(Liquid crystal display device)
An ECB type transflective liquid crystal display device having the arrangement shown in FIG. 4 was manufactured. The alignment film of the liquid crystal cell was made of polyimide, and the rubbing direction was made parallel in the vertical direction. The cell gap of the transmissive part is 4.0 μm, the cell gap of the reflective part is 2.0 μm, and nematic liquid crystal with Δn = 0.086 and dielectric anisotropy of +10.0 is injected into this space part. did. The two types of elliptically polarizing plates produced as described above were arranged as shown in FIG. The manufactured liquid crystal display device includes an upper polarizing plate P2, a retardation plate D, a retardation plate C, a liquid crystal cell composed of an upper and lower substrate and a liquid crystal layer sandwiched between the substrates, a retardation plate A ( The liquid crystal display device was composed of a first optically anisotropic layer), a retardation plate B (second optically anisotropic layer), and a lower polarizing plate P1 (including a linearly polarizing film). The arrows in the polarizing plates P1 and P2 indicate the respective transmission axes, the arrows in the phase difference plates A to D indicate the respective slow axes, and the arrows in the substrate indicate the rubbing direction of the rubbing process applied to the respective opposing surfaces. Indicates.

About the elliptically polarizing plate which consists of lower side polarizing plate P1, phase difference plate B, and phase difference plate A, a cross-sectional schematic diagram and the orientation form of the discotic liquid crystal molecule in the optically anisotropic layer of phase difference plate A are typically shown. As shown in FIG. As shown in FIG. 5, in the optically anisotropic layer of the phase difference plate A, the angle formed by the disc surface of the discotic liquid crystal molecule and the support plane changes continuously in the thickness direction, and the discotic liquid crystal molecule is In the layer, the film was fixed in an oriented state with a tilt angle of 5 ° on the alignment film side, an air interface side tilt angle of 85 °, and an average tilt angle of 45 °.
In FIG. 5, T represents a triacetyl cellulose film used as a support for the optically anisotropic layer in the production of the retardation plate A, and the same applies to FIGS.

  6 is a schematic cross-sectional view of a part of the liquid crystal display device fabricated in FIG. 6, showing the tilted alignment state of the liquid crystal molecules in the liquid crystal cell during black display and the discotic liquid crystal in the optically anisotropic layer of the phase difference plate A. It shows with the schematic diagram of the inclination orientation state of a molecule | numerator. An axis obtained by projecting the optical axis of the liquid crystal molecules in the liquid crystal cell during black display onto the layer plane, and an axis obtained by projecting the optical axis of the discotic liquid crystalline molecules in the optically anisotropic layer of the retardation plate A onto the layer plane. Intersected at 5 ° and was not orthogonal.

[Example 2]
Two optically anisotropic layers made of a discotic liquid crystalline compound having a film thickness of 2.3 μm were formed in the same manner as in Example 1 except that the coating amount was changed. The in-plane slow axis direction of the optically anisotropic layer appears in a direction perpendicular to the rubbing direction, and the laminate of the triacetylcellulose film and the optically anisotropic layer as a whole has an in-plane letter at a wavelength of 550 nm. 75 nm of foundation was shown. Further, the angle formed by the disc surface of the discotic liquid crystalline molecule and the plane of the support continuously changes in the thickness direction, 5 ° on the alignment film side and 85 ° on the air interface side, and the average inclination angle is 45. It turned out to be °. Two of the optically anisotropic layers were bonded together using an adhesive to obtain a retardation plate A ′ having two optically anisotropic layers containing discotic liquid crystals. The retardation plate A ′ as a whole had a retardation at a wavelength of 550 nm of 150 nm. That is, it was found that this retardation plate A ′ functions as the first optical anisotropic layer in the present invention.
Next, a lower elliptical polarizing plate was produced using the retardation plate A ′ instead of the retardation plate A and the same retardation plate B and polarizing plate as used in Example 1. FIG. 7 shows a schematic cross-sectional view of the lower elliptically polarizing plate produced in FIG. 7 together with a schematic view of the orientation of the discotic liquid crystal molecules in the two optically anisotropic layers of the phase difference plate A ′.

  Furthermore, it replaces with the lower elliptical polarizing plate used in Example 1, the lower elliptical polarizing plate produced above in FIG. 7, the same upper elliptical polarizing plate as used in Example 1, and for Example 1 is used. Using the same liquid crystal cell as in Example 1, an ECB type transflective liquid crystal surface device having the structure shown in FIG. FIG. 8 is a schematic cross-sectional view of a part of the manufactured liquid crystal display device, showing the tilted alignment state of the liquid crystal molecules in the liquid crystal cell during black display and the discotic liquid crystal molecules in the optically anisotropic layer of the retardation plate A ′. It shows with the schematic diagram of the inclination orientation state. An axis in which the optical axis of the liquid crystal molecules in the liquid crystal cell during black display is projected onto the layer plane, and an axis in which the optical axis of the discotic liquid crystalline molecules in the optically anisotropic layer of the phase difference plate A ′ is projected onto the layer plane. Intersected at 5 ° and was not orthogonal.

[Example 3]
The Arton film was stretched to obtain a retardation plate having an in-plane retardation at 550 nm of 100 nm. After the surface of the retardation plate is subjected to corona discharge treatment, a coating solution containing a modified polyvinyl alcohol is applied in the same manner as in Example 1 to form a film having a thickness of 1 μm, and the surface of the film is rubbed (formed later). A rubbing treatment in a direction perpendicular to the slow axis of the retardation plate was performed to obtain an alignment film. A coating liquid containing a discotic liquid crystalline compound having the following composition was applied onto the rubbing surface of this alignment film, and after alignment aging, the film was fixed by UV irradiation to form an optically anisotropic layer having a thickness of 2.5 μm. Formed.
─────────────────────────────────
Coating liquid composition of discotic liquid crystal layer ─────────────────────────────────
Discotic liquid crystal (1) 32.6% by mass
Cellulose acetate butyrate 0.8 mass%
0.03% by mass of the fluorine-containing compound (2)
The above modified trimethylolpropane triacrylate 3.2% by mass
Sensitizer 0.4% by mass
The photopolymerization initiator 1.1% by mass
Methyl ethyl ketone 61.9% by mass
─────────────────────────────────

  The in-plane retardation of this discotic liquid crystal layer alone at 550 nm is 50 nm, and the angle formed by the disc surface of the discotic liquid crystal molecules and the support plane changes continuously in the thickness direction, and 5 ° on the alignment film side. It was found that the air interface side was 55 ° and the average inclination angle was 30 °. Further, the in-plane slow axis direction of the discotic liquid crystal layer was a direction orthogonal to the rubbing direction and parallel to the slow axis direction of the ARTON film. The total in-plane retardation of the laminate of Arton film and discotic liquid crystal layer was 150 nm. That is, this laminate was found to function as the first optical anisotropic layer in the present invention. An ECB-type transflective liquid crystal surface device was produced in the same manner as in Example 1 by using this arton film and discotic liquid crystal layer laminate instead of the retardation plate A used in Example 1.

[Comparative Example 1]
The Arton film was uniaxially stretched to obtain a retardation plate having an in-plane retardation at 550 nm of 150 nm. The optical axis of the retardation plate was parallel to the film plane, and the Nz factor was 1.0. Instead of the phase difference plate A used in Example 1, a transflective liquid crystal surface device was produced in the same manner as in Example 1 using the phase difference plate produced here, and the contrast ratio was measured.

[Comparative Example 2]
An ECB type transflective liquid crystal display device is manufactured in the same manner as in Example 1 using a liquid crystal film prepared by fixing a rod-like liquid crystal with nematic hybrid alignment according to Example 1 described in JP-A-2002-31426. Produced.

  For each of the manufactured liquid crystal display devices, the backlight is turned on, and the brightness ratio (white display / black display) of white display (1.0 V application) and black display (3.3 V application) is used as the contrast ratio. The contrast ratio was measured by changing the polar angle. Table 1 shows polar angles at which the contrast ratio is 10. The larger the polar angle, the better the viewing angle.

It is the figure which showed the cross-sectional schematic diagram of the 1st optically anisotropic layer which consists of a single layer or two layers with the schematic diagram of the orientation state of a discotic liquid crystalline molecule. In the laminated phase difference plate of the present invention, it is a sectional view showing a typical aspect of a laminated phase difference plate comprising an optically anisotropic layer containing a discotic liquid crystal and a second optically anisotropic layer. It is sectional drawing which shows the typical aspect of the elliptically polarizing plate of this invention. FIG. 3 is a diagram illustrating an arrangement of each film and a liquid crystal cell in the liquid crystal display device of Example 1. 3 is a schematic cross-sectional view showing the arrangement of each film and the tilt direction of the discotic liquid crystal in the lower elliptical polarizing plate of Example 1. FIG. FIG. 3 is a schematic cross-sectional view showing the arrangement of each film, the discotic liquid crystal tilt direction, and the liquid crystal molecule tilt direction during black display in the liquid crystal display device of Example 1. It is a cross-sectional schematic diagram which shows the arrangement | positioning of each film in the elliptically polarizing plate of Example 2, and the inclination direction of a discotic liquid crystal. It is a cross-sectional schematic diagram which shows arrangement | positioning of each film in the liquid crystal display device of Example 2, the inclination direction of a discotic liquid crystal, and the inclination direction of the liquid crystal molecule at the time of black display.

Explanation of symbols

A, A ′ retardation plate having optically anisotropic layer containing discotic liquid crystal (first optically anisotropic layer)
B retardation plate (second optically anisotropic layer)
P, P1, P2 Polarizing plate (Linear polarizing film)
C, D Phase difference plate T Triacetyl cellulose film

Claims (3)

A liquid crystal display device including a first optical anisotropic layer, a second optical anisotropic layer, a polarizing film, and a driving liquid crystal cell, wherein the first optical anisotropic layer contains at least a discotic liquid crystalline compound. The disc surface of the discotic liquid crystalline molecules is inclined with respect to the layer plane, and the first optically anisotropic layer has a wavelength of 550 nm and has the following formula ( The retardation (Re) value defined by I) is 70 to 200 nm, and the direction of the axis of the optical axis of the discotic liquid crystalline molecule in the first optically anisotropic layer projected onto the layer plane; A liquid crystal display device, characterized in that the average direction of the axes obtained by projecting the optical axes of liquid crystal molecules in a driving liquid crystal cell during black display onto a layer plane is not orthogonal.
_{Re = (n x -n y)} × d (I)
(Wherein, n _x is a refractive index in a slow axis direction of the optically anisotropic layer plane, n _y is a refractive index in a fast axis direction of the optically anisotropic layer plane, d is the optical anisotropy The thickness of the layer.) 2. The liquid crystal display device according to claim 1, wherein an angle formed by a disc surface of the discotic liquid crystal molecule and a layer plane in the layer changes in a depth direction of the layer. The liquid crystal display device according to claim 1, wherein the second optically anisotropic layer has an in-plane retardation value of 200 to 300 nm at a wavelength of 550 nm.

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