JPH1010318A - Optical anisotropic body and liquid crystal display - Google Patents

Abstract

(57) Abstract: Provided is an optically anisotropic film having excellent optical compensation performance, which can obtain a desired alignment structure by a simple method, and a liquid crystal display device having excellent viewing angle characteristics using the same. . In an optically anisotropic body having a substrate having ridge-shaped unevenness on its surface and a layer containing an optically anisotropic compound, the ridge-shaped unevenness is formed by a valley line 2 of a concave portion and a ridge line 1 of a convex portion. Are formed substantially parallel and periodically, and the average value of the period is 200
0.5 μm or less and μm or less, and the valley line 2 of the ridge-shaped unevenness
When the average value of the height difference between the ridge line 1 of the convex portion and the average value of the period of the ridge-shaped unevenness is not more than 5 times and 0.3 times or more, and when cut on a plane perpendicular to the ridge line 1 of the convex portion, The cross-sectional shape of the ridge-shaped unevenness is a shape connected by a combination of straight lines and / or curved lines. When the distance between the ridge line 1 and the valley lines 2 on both sides thereof is projected on the base material surface, one projection line is formed. Is an optically anisotropic body in which an optically anisotropic compound layer is formed directly or through one or more intermediate layers on the substrate having the ridge-like irregularities, which is twice or more of the other projection line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a twisted nematic (hereinafter sometimes referred to as TN) type liquid crystal display device and a thin film transistor (hereinafter sometimes referred to as TFT).
Type liquid crystal display element or super twist nematic (hereinafter, referred to as
It may be written as STN. TECHNICAL FIELD The present invention relates to an optically anisotropic film used for a liquid crystal display device, and a liquid crystal display device using the optically anisotropic film.

[0002]

2. Description of the Related Art TN-type, STN-type or TFT-TN-type liquid crystal display elements have advantages such as lightness, thinness, and low cost, and are widely used as flat displays.
However, the viewing angle is narrower than other light emitting type flat displays and cathode ray tubes, so that there is a limit in expanding the use. In a liquid crystal cell of a liquid crystal display device, when no voltage is applied, the liquid crystal molecules are twisted. When a voltage is applied, the liquid crystal molecules are tilted at the interface between the substrates, and the liquid crystal molecules are vertically aligned toward the inside of the cell. ing. In the STN-type liquid crystal display device, a polymer film having uniaxial orientation is generally used together to cancel birefringence exhibited by a liquid crystal cell. However, the birefringence due to a part of the liquid crystal molecules being perpendicular to the substrate and the rest being inclined with respect to the substrate causes a narrow viewing angle in all twisted liquid crystal display devices including the STN type. Cause. These disadvantages are considerably improved by using an optically anisotropic body having optical anisotropy also in the vertical direction in the STN type and by changing the optical anisotropy in the in-plane and vertical directions in the TN type. . However, since the liquid crystal molecules in the liquid crystal cell in the driven state are known to have components that are tilted and aligned in addition to the vertically aligned state, the liquid crystal molecules have a molecular axis parallel or perpendicular to the substrate normal. With a compensating film, the refractive index anisotropy of the liquid crystal cannot be completely compensated when viewed from an oblique direction, so that the viewing angle characteristics have not yet reached a satisfactory level.

In order to compensate for the birefringence of the tilted liquid crystal, attempts have been made to improve the viewing angle characteristics of a liquid crystal display device by using an optically anisotropic member whose optical axis is tilted from the film surface. For example, Japanese Patent Application Laid-Open No. 3-276123 discloses a birefringent layer in which liquid crystal molecules or main-chain type polymer liquid crystal are tilt-aligned in a liquid crystal cell and the maximum refractive index direction is tilted from the substrate. JP-A-3-276124 exemplifies a birefringent layer in which oblique deposition is performed on both surfaces of a liquid crystal cell and the major axis direction of the liquid crystal molecules is distributed in the thickness direction. Japanese Patent Laid-Open No. 4-46312 discloses that a cholesteric liquid crystal having a low twist rotation number is used to compensate for a tilt alignment component, thereby improving a viewing angle characteristic of a TFT type or STN type liquid crystal display device. . Further, Japanese Patent Application Laid-Open No. Hei 5-157913 discloses that the stretching method of a polymer film is devised to have an optical axis inclined from the plane of the film to improve the viewing angle characteristics of the STN type liquid crystal display device. ing. JP-A-6-75116 exemplifies that a viewing angle characteristic of a liquid crystal display device is improved by using a polymer film whose optical axis is inclined from the film normal direction. Japanese Patent Application Laid-Open No. 6-250166 discloses that the viewing angle characteristic of a liquid crystal display device is improved by applying an electric field to a liquid crystal cell containing cholesteric liquid crystal, using a liquid crystal element in which the cholesteric liquid crystal is tilted and aligned. Is illustrated.

[0004] Next, Society for Information Display
International Symposium Digest of Technical Papers
(1993) p. 277 describes the field of view of a TN-type liquid crystal display device by using two optical anisotropic bodies whose optical axes are inclined from the film normal direction and an optical anisotropic body having an optical axis in the film plane. It is reported that the angular characteristics can be improved in principle.

Many attempts have been made to control the alignment of liquid crystal molecules because the alignment of the liquid crystal molecules in the display cell has a large effect on the display quality. Is generally used to control the orientation. As the alignment film, for example, a polymer film of polyimide or the like is provided on the substrate to obtain horizontal alignment, and the surface is rubbed with a cloth or the like, and then the low-molecular liquid crystal is aligned, or the substrate is made of SiO ₂ , SiO, MgO, A method of obliquely depositing an inorganic substance such as MgF ₂ and using it as an inclined alignment film, a method of using a stretched polymer film, and the like are known (Basics and Applications of Liquid Crystals, pp. 97-100, Industrial Research Council, 1991). .

Further, as a method for obtaining the tilt alignment of the low molecular liquid crystal, an organic alignment film such as polyimide, SiO 2
₂ , oblique deposition of inorganic substances such as SiO, MgO, and MgF ₂ is known. These alignment films have the function of making the alignment of the liquid crystal molecules in the liquid crystal display element uniform and giving a pretilt, and realize the display quality improved compared to the prior art.

However, with these methods, it is difficult to easily obtain an alignment structure necessary for compensating the liquid crystal in the liquid crystal cell at the time of driving.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optically anisotropic film having an excellent optical compensation performance, which can obtain a desired orientation structure by a simple method, and an excellent viewing angle characteristic using the same. It is to provide a liquid crystal display device.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have found that an optically anisotropic material has been formed on a substrate on which ridges of a specific shape are regularly formed. The present inventors have found that an optically anisotropic body having a desired orientation structure can be easily obtained by forming a film containing an acidic compound, and have completed the present invention. Next, the present invention will be described in detail.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to [1] an optically anisotropic body having a substrate having ridge-shaped irregularities on its surface and a layer containing an optically anisotropic compound, wherein the ridge-shaped irregularities are The valley line of the concave portion and the ridge line of the convex portion are formed substantially in parallel and periodically, and the average value of the period is 200 μm or less and 0.5 μm or more, and the valley line of the ridge-shaped unevenness and the ridge line of the convex portion. The average value of the height difference is not more than 5 times and not more than 0.3 times the average value of the period of the ridge-shaped unevenness, and when cut on a plane perpendicular to the ridgeline of the convex portion, the cross-section of the ridge-shaped unevenness The shape is a shape connected by a combination of straight lines and / or curves, and when the distance between the ridge line and the valley lines on both sides thereof is projected on the substrate surface, one projected line is at least twice as large as the other projected line. The optically anisotropic compound layer is formed directly on the substrate having the ridge-shaped irregularities or via one or more intermediate layers. The present invention relates to an optically anisotropic body formed as described above.

[0011] Further, the present invention provides [2] a cross section of one ridge including a convex portion, which is perpendicular to the ridge line, a straight line connecting points on two valley lines and a point on the ridge line from a point on one valley line. 3. The optical anisotropic body according to claim 1, wherein a figure surrounded by a line passing through to a point on the other valley line forms a substantially triangular shape. The present invention also relates to [3] the optically anisotropic material according to [1] or [2], wherein the orientation is fixed by polymerization of the optically anisotropic compound. Furthermore, in the present invention, [4] a polymerizable low molecule is added to the optically anisotropic compound, and the orientation is fixed by polymerizing the optically anisotropic compound and the polymerizable low molecule or only the polymerizable low molecule. The present invention relates to the optically anisotropic body described in [1] to [3].

Furthermore, the present invention relates to [5] the optically anisotropic material according to [1] to [3], wherein the optically anisotropic compound is a liquid crystal having a nematic phase or a smectic phase.
The present invention also relates to [6] a liquid crystal display device using the optically anisotropic material according to any one of [1] to [5].

[0013]

Next, the present invention will be described in detail. The substrate having ridge-shaped irregularities used in the present invention has ridge-shaped irregularities on at least one surface, and the valley line of the concave portion and the ridge line of the convex portion have a constant period parallel to one direction. It was formed. Since it is desirable that the average period of the ridge-shaped unevenness is not visible, it is 200 μm or less and 0.5 μm or more, preferably 50 μm or less and 0.5 μm or more, and more preferably 20 μm or less and 0.8 μm or more. The height difference of the ridge-shaped unevenness is such that the average value of the difference between the position of the bottom point of the concave portion and the position of the apex of the convex portion is 0.1 times or more, preferably 5 times or less, and preferably 3 times or less the period of the ridge-shaped unevenness. It is 0.2 times or more. Also, as the shape of the ridge-shaped unevenness, when cut on a plane perpendicular to the ridge line of the convex portion, the shape of the ridge-shaped uneven cross-section,
It is a shape connected by a combination of straight lines and / or curves, and when the distance between the ridge line and the valley lines on both sides is projected on the base material surface, one distance is more than twice the other distance, and is preferably Is 4 times or more, more preferably 6 times or more.

Further, the ridge-shaped unevenness is formed into a structure suitable for orienting the optically anisotropic compound in a desired orientation. For example, as shown in FIG. 1, in a cross section of one ridge including a convex portion, which is perpendicular to the ridge line, a straight line connecting points on two valley lines and a point on one valley line passes through a point on the ridge line to the other. When the figure surrounded by the line connecting the points on the valley line is substantially triangular, that is, when the cross-sectional shape of the ridge-shaped irregularities is a sawtooth shape, the larger area projected on the bottom surface of the base material The inclination orientation of the inclination angle corresponding to the inclination angle of the wall surface of the ridge-shaped unevenness with respect to the base material can be realized. Further, as shown in FIG. 2, there is also an example in which the cross section perpendicular to the ridge line is a wavy line. The inclination angle of the wall surface of the larger ridge-shaped unevenness with respect to the substrate projected on the substrate bottom surface is appropriately set depending on the liquid crystal cell to be compensated. The angle is preferably 5 ° or more and 60 ° or less, more preferably 10 ° or more and 50 ° or less, since the influence of the other single-sided wall becomes large and uniform orientation is difficult to obtain.

In a cross section perpendicular to the ridge line of one ridge including a convex portion, when a vertex and a bottom point are connected by a curve, the curvature may be positive or negative, or may change from positive to negative or from positive to negative. It may change from negative to positive. The orientation of the optically anisotropic compound can be changed by changing the inclination angle of the longer line segment projected on the bottom of the substrate in each line connecting the vertex and the bottom points on both sides thereof. The curvature of the longer line of the line projected onto the bottom of the substrate or the structure of change in the curvature may be set according to the orientation of the liquid crystal molecules in the liquid crystal cell to be compensated.

The ridges may be formed by any known method as long as the ridges can be formed regularly and without defects. Specifically, a method of directly molding a substrate on which ridge-shaped irregularities are formed, a method of transferring the shape of ridge-shaped irregularities by press molding, and passing a substrate heated above the glass transition point between rolls. Examples thereof include a method of transferring the ridge-shaped unevenness formed on the roll surface, a method of printing a photo-curable resin or a thermosetting resin in the ridge-shaped unevenness, and then polymerizing and curing. Among these, from the viewpoints of productivity and solvent resistance, a method of printing a photocurable resin or a thermosetting resin in the form of ridges and projections and then polymerizing and curing the resin is preferable. The thermosetting resin or photocurable resin used here does not lose its shape when coated with an optically anisotropic material, or decomposes or reacts with the optically anisotropic material during use to degrade its properties. If there is no, there is no limitation, and known ones can be used. Examples of the thermosetting resin material or the photocurable resin material include urethane acrylate, ester acrylate, glycidyl ether, acryl-silicon, and organosiloxane resins, oligomers, and monomers.

Also, a method of directly molding a substrate having ridge-shaped irregularities, a method of transferring the shape of ridge-shaped irregularities by press molding, and a method of passing a substrate heated to a glass transition point or higher between rolls. In the case of the method of transferring the shape of the ridge-shaped unevenness formed on the roll surface, the difference between the position of the bottom point of the recessed portion of the ridge-shaped unevenness and the average value of the apex of the protrusion is the difference between the average value of the protrusions of the base film. If the thickness is too large with respect to the thickness at the apex, the strength of the film is reduced. Therefore, the thickness is preferably 50% or less, more preferably 30% or less, of the thickness of the base film.
Further, in the case of a method of polymerizing and curing the photocurable resin or the thermosetting resin after printing the shape of the ridge-shaped unevenness, if the thickness of the photocurable resin or the thermosetting resin layer is too large, the coefficient of thermal expansion is too large. Or because the difference in coefficient of water expansion causes warpage of the film, the thickness at the apex of the ridge-shaped unevenness of the photocurable resin or thermosetting resin layer is the bottom point of the ridge-shaped unevenness of the concave portion. 1 or more times the difference between the average value of the position and the vertex of the convex part 5
It is preferably at most 1.1 times, more preferably at least 1.1 times and at most 3 times.

For the purpose of increasing the orientation of the optically anisotropic compound, or improving the adhesion between the layer containing the optically anisotropic compound and the substrate having the ridged irregularities, the ridged irregularities are used. One or more intermediate layers may be provided between the layer and the layer containing the optically anisotropic compound so as not to disturb the shape of the ridge-like unevenness. The material and forming method of the intermediate layer are a method of applying a water-soluble polymer such as polyvinyl alcohol, a polyvinyl alcohol-polyethylene vinyl alcohol copolymer, pullulan, and dextrin; or a polyimide, a polyamide, a polyurethane, and an acrylic oligomer. And a method in which an oligomer or monomer such as an acryl-silicon-based or organopolysiloxane-based resin is applied, and the oligomer or monomer is three-dimensionally crosslinked by thermal polymerization or photopolymerization.

When the intermediate layer is coated on a substrate having regularly formed ridge-like irregularities, the surface of the substrate is treated with a plasma from the viewpoint of improving the uniformity of the intermediate layer and the adhesion to the substrate. The surface tension of these polymer films may be increased by a known surface modification technique such as treatment, corona treatment, ultraviolet irradiation, treatment using an acid or alkali. Examples of the method for applying the intermediate layer include a roll coating method, a gravure coating method, a microgravure coating method, a Meyer bar coating method, a bar coating method, a spin coating method, a spray coating method, a printing method, and a dipping method. Among these, when the base material is a polymer film, a roll coating method, a microgravure coating method, a gravure coating method, or a bar coating method is preferable because a uniform film thickness can be obtained with good productivity. When the substrate is an inorganic substrate such as a glass plate, a spin coating method is preferably used in addition to the above method.

In this case, the total thickness of the intermediate layer may be at least the thickness of a monomolecular film. If the thickness is too large, the shape of the ridge-like irregularities of the base is disturbed, and the desired inclined orientation structure cannot be obtained. Therefore, it is preferably 1 μm or less, more preferably 0.1 μm.
It is 5 μm or less, particularly preferably 0.2 μm or less.

When the intermediate layer is made of a thermosetting resin such as polyimide, the intermediate layer is cured by heat treatment. The heat treatment temperature can be appropriately selected according to the material of the intermediate layer used. When a compound having photocurability is used as the intermediate layer, it is cured by irradiation with light. In the case of a resin having both thermosetting and photocuring properties, heat treatment or light irradiation may be performed.

Further, the substrate on which ridge-shaped irregularities are regularly formed, and the substrate on which an intermediate layer is further formed,
Rubbing may be performed using a rubbing roll, if necessary, for the purpose of strengthening the orientation of the optically anisotropic body. The material of the roller used for rubbing is not particularly limited, and a known buff cloth or flocking roller is used. There is no particular limitation on the amount of the rubbing roller pressed into the alignment film, the number of rotations of the roller, the moving speed of the roller relative to the base material, the number of rubbing, and the like.

The substrate may be any substrate as long as the object of the present invention is not hindered. In particular,
Glass and a polymer film are mentioned. Among them, a polymer film is preferable from the viewpoint of handling properties. When a polymer film is used as a substrate, it is preferable that the polymer does not change in optical properties or shape at a use temperature or a temperature in an assembling step. In particular, a polymer having a somewhat high glass transition temperature or a polymer to which a plasticizer is added is preferably a polymer having a somewhat high flow temperature. The preferred lower limit of the glass transition temperature or softening temperature of the polymer of the base material is determined within a range where the liquid crystal display device is not deformed such as a change in optical properties or film shrinkage within a temperature range to be exposed when the liquid crystal display device is assembled and used. it can. Specifically, the glass transition temperature or softening temperature required for the substrate is 8
It is preferably at least 0 ° C, more preferably at least 90 ° C. Examples of the polymer satisfying these conditions include polycarbonate, polysulfone, polyarylate, polyether sulfone, cellulose acetate, cellulose acetate, cellulose acetate, ethylene vinyl alcohol copolymer, and polyethylene naphthalate. , Polysulfone or cellulose triacetate. On the other hand, if the substrate is too thin, the workability and handling properties are poor, and if the substrate is too thick, the attached liquid crystal cell becomes thick, which is not preferable. The thickness of the substrate is preferably 10 μm or more and 1000 μm or less, and more preferably 30 μm or more and 500 μm or less.

In the present invention, it is preferable to use a polymer having a small birefringence as the substrate. However, if it is used for a display system utilizing birefringence such as an STN type or electric field control birefringence (hereinafter sometimes referred to as ECB) type liquid crystal display device, an optically anisotropic material coated and aligned thereon is used. It is preferable that the birefringence combined with the hydrophilic compound has an appropriate value within a range that can be matched with the liquid crystal cell.

Here, a plasticizer may be added to the polymer in order to lower the glass transition temperature or softening temperature of the polymer and suppress the orientation. The type and amount of the plasticizer are not particularly limited as long as the object of the present invention is not impaired. In addition, the purpose is to impart mechanical strength to the base material, to improve the handleability, or to improve the adhesiveness when bonding to a panel of a liquid crystal display device (hereinafter, sometimes referred to as LCD). For this purpose, additives may be used in the polymer. The type and amount of the additive are not particularly limited as long as the purpose of the present invention is not impaired.

In the present invention, any optically anisotropic compound can be used as long as the object of the present invention is not hindered, and is appropriately selected depending on the liquid crystal cell to be compensated. Among them, a liquid crystal compound is preferable from the viewpoint of controllability of alignment. Among them, a liquid crystalline compound containing a polymerizable group is preferable from the viewpoint of polymerization fixation after alignment. As the liquid crystal compound used for the optically anisotropic substance, a low molecular liquid crystal, a liquid crystal oligomer, a high molecular liquid crystal, and the like can be given. The liquid crystalline compound may be used as a single component, or a mixture of plural compounds having different molecular weights and structures may be used.

The phase of the liquid crystal is not particularly limited, and various phases such as a nematic phase, a smectic phase and a cholesteric phase can be used. The type of liquid crystal differs depending on the type of liquid crystal cell to be compensated. ST
In the case of an N-type liquid crystal cell or an ECB-type liquid crystal cell, it is preferable to use an optical anisotropic body in which a nematic liquid crystal or a smectic liquid crystal is aligned, a combination thereof, or an optical anisotropic body including these. Also,
For compensating the optical rotation of the liquid crystal cell, a chiral agent or a cholesteric liquid crystal may be added to give a twist orientation of 90 ° or more and 300 ° or less. In the case of a TN type liquid crystal cell or a TFT type liquid crystal cell, use any one of or an optical anisotropic body containing a mixture of a cholesteric liquid crystal or a nematic liquid crystal and a chiral agent and orienting them. Is preferred.

The low-molecular liquid crystal used in the present invention includes:
Examples represented by the following general formula (1) are exemplified.

Embedded image Wherein R ₁ is an alkyl group or an alkoxy group having 1 to 6 carbon atoms. Ar ₁ , Ar ₂ and Ar ₃ each independently represent a 1,4-phenylene group, a 1,4-cyclohexylene group, a pyridine-2,5-diyl group, a pyrimidine-2,5
-Diyl groups or derivatives of these groups. Sp ₁ ,
Sp ₂ is each independently -COO-, -OCO-,-
NCH -, - CHN -, - CH 2 -CH 2 -, - CH 2
-O-C - ,, - O- CH 2 -, - N = N -, - C≡C
—, A single bond (corresponding to a direct bond between Ar ₁ and Ar ₂ , or Ar ₂ and Ar ₃ ), or a group represented by the following general formula (2). k ₁ is an integer of 0 or 1 (when k ₁ is 0, this corresponds to a direct bond between Ar ₂ and B ₁ ). B ₁ is a hydrogen atom, a cyano group, a halogen, an alkyl group or an alkoxy group having 1 to 6 carbon atoms,
Acrylate group, methacrylate group, the following general formula (a)
Or a group represented by the following general formula (b). ]

Embedded image

Embedded image

Embedded image (Where R ₃ represents -H or the following formula;

Embedded image R ₄ represents —H or a methyl group; R ₅ represents —H or R
_And R ₆ is a straight or branched C 1 -C 2
0 alkyl group or linear or branched C 1
And 20 to 20 alkoxycarbonyl groups, and when branched, may have an asymmetric carbon atom. )

Examples of the liquid crystal oligomer include side-chain type liquid crystal oligomers and main-chain type liquid crystal oligomers, and examples of the polymer liquid crystal include side-chain type polymer liquid crystals and main-chain type polymer liquid crystals. From the viewpoints of time and time, a side chain type liquid crystal oligomer or a side chain type polymer liquid crystal is preferable. Examples of the side chain type liquid crystal oligomer or side chain type liquid crystal polymer include those having one or more kinds of repeating units represented by the following general formula (3).

Embedded image [In the formula, A is a group represented by the following general formula (4) or (5). In the general formula (4), -Si-O- is a main chain of the general formula (3) and may be cyclic or linear. In the general formula (5), —C—CH ₂ — is the main chain of the general formula (3), and the COO group binds to Sp ₃ .
In the general formula (3), when A is the general formula (4), R ₂
Is an alkyl group having 1 to 6 carbon atoms or a phenylene group. In the general formula (3), when A is the general formula (5), R ₂ is an alkyl group or an alkoxy group having 1 to 6 carbon atoms.
In the general formula (3), Ar ₄ , Ar ₅ , and Ar ₆ each independently represent a 1,4-phenylene group, a 1,4-cyclohexylene group, a pyridine-2,5-diyl group, a pyrimidine-2,5, -Diyl groups or derivatives of these groups.

Sp_ThreeIs an alkyl group having 2 to 8 carbon atoms or
It is an alkoxy group. Sp_Four, Sp _FiveAre independent
To -COO-, -OCO-, -NCH-, -CHN-,
-CH_Two-CH_Two-, -CH_Two-O-, -O-CH
_Two-, -N = N-, -C≡C-, a single bond (Ar_FourAnd Ar
_FiveOr Ar_FiveAnd Ar₆Corresponds to a direct connection
You. ) Or a group represented by the general formula (2).
k_TwoIs an integer of 0 or 1 (k_TwoIs 0 when Ar_Five
And B_TwoIs directly linked. ). B_TwoIs hydrogen
Atom, cyano group, halogen, alkyl group having 1 to 6 carbon atoms
Or alkoxy group, acrylate group, methacrylate
A group represented by the general formula (a) or the general formula (b)
Group. ]

[0031]

Embedded image

Embedded image

The total number of repeating units represented by the general formula (3) is preferably 4 or more and 100 or less, more preferably 4 or more and 21 or less in the side chain type liquid crystal oligomer. Next, in the polymer liquid crystal, the total number of repeating units represented by the general formula (3) is preferably 50 or more and 2000 or more.
0 or less, and more preferably 50 or more and 10,000 or less. These side chain type liquid crystal oligomers or side chain type polymer liquid crystals may be used alone or as a mixture. Further, the side chain group of the side chain type liquid crystal oligomer or the side chain type liquid crystal polymer does not need to be single, and may be a copolymer having different side chains.

When the optically anisotropic substance is used as an optical compensator for a liquid crystal cell, it is preferable that the molecular weight of the liquid crystal compound be small, since the transition temperature is low and the optical properties greatly change due to the temperature change. If it is large, it is not practical because the viscosity of the liquid becomes high and the time required for alignment becomes long.
Therefore, when used in a system that does not like the change of the optical property value due to a temperature change, and when using a low-molecular liquid crystal, it has a polymerized group in order to continue to maintain the orientation after polymerization after polymerization. Preferably, one is used. In this case, the number average molecular weight of the liquid crystal is preferably from 1200 to 10000 in terms of polystyrene when it is non-polymerizable, and is preferably 10,000 or less when it is polymerizable. In the case where the optical characteristic of the compensating partner changes due to a temperature change and it is necessary to perform optical compensation in accordance with the change, refer to Japanese Patent Application Laid-Open
By selecting a liquid crystalline compound and a production method as described in JP-A-5839, an optically anisotropic body having such characteristics can be produced.

The liquid crystal compound preferably contains a polymer group from the viewpoint of fixing the alignment. However, even if the compound does not contain a polymer group and the ratio of the polymer group is small, the low molecular weight compound containing the polymer group can be fixed. It can be preferably used if it is added as much as possible. Specifically, from the viewpoint of fixing the orientation, it is preferable to add the polymerizable group so as to have an average of 0.5 or more polymerizable groups per molecule, more preferably 1 or more, and particularly preferably 1 molecule or more. It is added so as to have 1.5 or more polymerizable groups. Further, if the weight ratio of the low molecular weight compound containing a polymerizable group is too large, the orientation is disturbed. Therefore, the weight ratio is preferably 20% by weight or less, more preferably 15% by weight or less. Also, low molecular weight compounds containing a polymerizable group, if the molecular weight is too high, the viscosity increases,
Since the alignment takes time, the molecular weight is 1000
Those having 0 or less are preferable. The low molecular weight compound containing a polymerizable group may be any compound as long as it does not disturb the orientation of the liquid crystal, but a photocurable or thermosetting compound is preferably used. Examples of the photo-curable or thermo-curable compound include urethane acrylate, ester acrylate, glycidyl ether, acryl-silicon or organosiloxane resins, oligomers or monomers.

As for the method of laminating on the alignment base material, as long as the shape of the alignment base material and the ridge-like unevenness is not damaged, the lamination can be performed by an existing method. Specifically, a method of applying the liquid crystal compound in a solution state and a method of applying the liquid crystal compound in an isotropic phase state are exemplified, and a method of applying from a solution state is preferable. Examples of the coating method include a usual roll coating method, a gravure coating method, a bar coating method, a microgravure coating method, a Meyer bar coating method, a spin coating method, a spray coating method, a printing method, and a dipping method. Among these, a roll coating method, a gravure coating method, a bar coating method, and a micro gravure coating method are preferable because a uniform film thickness can be obtained with good productivity on a polymer substrate. When the substrate is an inorganic substrate such as a glass plate, a spin coating method is preferably used in addition to the above method.

When the liquid crystal compound is applied in the form of a solution, the concentration of the optically anisotropic compound depends on the application method,
It is appropriately determined according to the coating solution viscosity and the coating thickness.
100% by weight is preferred. The thickness of the optically anisotropic compound layer is determined by the refractive index anisotropy of the optically anisotropic compound, the orientation form, and the desired optical properties. From the viewpoint of cost and uniformity of the coated product, the thickness is 0.1 to 10 μm. And more preferably 0.3 to 7 μm. Also, the front retardation Δnd of the optically anisotropic film
(Δn is the birefringence, d is the thickness of the optically anisotropic film)
Is set according to the characteristics of the liquid crystal cell to be compensated. Specifically, it is preferable to set the value of 1 according to the liquid crystal cell to be compensated.
It is selected from values of 0 nm or more and 3000 nm or less. More preferably, it is selected from 20 nm or more and 2000 nm or less.

Heat treatment is performed to align the liquid crystal compound. The heat treatment temperature is Tt (° C.), the transition temperature from the crystal phase or glass phase of the liquid crystal compound to the liquid crystal phase is Tg (° C.),
If the temperature at which the deformation of the base material or the alignment film occurs is written as Tk (° C.), the heat treatment temperature is (Tg + 30) ≦ Tt ≦ (T
The range shown by k-10) is preferable, and (Tg + 40)
The range represented by ≦ Tt ≦ (Tk-20) is more preferable. If the heat treatment time is too short, the desired orientation structure is not realized, and if the heat treatment time is too long, it is industrially undesirable.
It is preferably from 1 minute to 1 hour, more preferably from 0.2 minute to 10 minutes. By the above heat treatment, the liquid crystalline compound is oriented to a desired orientation structure. The heating rate and cooling rate in the heat treatment are not particularly limited.

In order to control the orientation of the liquid crystal compound, an electric or magnetic field may be applied during the heat treatment.

After orientation, in order to fix the orientation, it is preferable to carry out polymerization while maintaining the orientation. Examples of the method for fixing the orientation include photopolymerization by light irradiation or the like, radiation polymerization by γ-rays or the like, and thermal polymerization. Among these polymerization methods, photopolymerization and thermal polymerization are preferred from the viewpoint of simplicity of the process, and photopolymerization is more preferred from the viewpoint of good orientation retention. When performing photopolymerization or thermal polymerization, it is preferable to add a polymerization initiator. As the polymerization initiator, a known one can be appropriately used as long as it does not hinder the alignment of the liquid crystal compound.

When photopolymerization is performed, the irradiation light intensity
Optimal value according to the thickness of the system and the type of liquid crystal oligomer used
May be selected, but preferably 0.01 to 5.0 J /
cm ^TwoAnd more preferably 0.1 to 3.0.
J / cm^TwoIt is. Irradiation light amount is 0.01 J / cm^TwoThan
If the amount is small, the reaction of the polymerizable group may be insufficient.
5.0 J / cm^TwoIf it is larger, the deterioration of optical properties and
There is a problem from the viewpoint of manufacturing cost.

The optically anisotropic body of the present invention may be provided with a normal transparent hard coat layer or gas barrier layer on one or both sides for the purpose of protecting the surface and securing the adhesiveness of the adhesive. The hard coat layer or gas barrier layer is not particularly limited, but is preferably a photocurable or thermosetting resin,
Urethane acrylate, ester acrylate, glycidyl ether, acryl-silicon or organosiloxane resins, oligomers or monomers are preferably used. Also in the case of performing photopolymerization or thermal polymerization of the hard coat layer or the gas barrier layer, it is preferable to add a polymerization initiator. Known polymerization initiators can be used as long as they do not hinder the alignment of the liquid crystal compound.
In addition, curing may be performed under the same method and conditions as those described above.

The liquid crystal display device of the present invention is a liquid crystal display device having a liquid crystal display cell, at least one or more optically anisotropic film, and at least one or more polarizing film.
In the liquid crystal display device of the present invention, there are no particular restrictions on the location and the number of optically anisotropic films, and any location may be used between the polarizing film and the liquid crystal display cell. The angle between the absorption axis of the polarizing film, the rubbing direction of the liquid crystal display cell and the stretching axis of the optically anisotropic film, and the like are determined so that the contrast, viewing angle characteristics and display color tone are optimized.

[0043]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The measuring methods and devices used in the following synthesis examples, examples and comparative examples are as follows. The phase transition temperature of the liquid crystal compound was determined by differential thermal scanning analysis (DSC) and observation of the alignment state with a polarizing microscope. That the obtained optically anisotropic film has a negative refractive index anisotropy, the angle between the ridge-like irregularities formed on the substrate surface is 0 °, 90 °,
There is a direction in which retardation increases in at least three directions when tilted toward the viewer when viewed from the viewer with a straight line at 180 °, 270 ° and on a plane parallel to the bottom surface of the substrate as an axis. I confirmed from that. The oblique orientation of the obtained optically anisotropic film was confirmed from the fact that the retardation of the optically anisotropic film measured from directly above was not the minimum. In addition, the measurement of the retardation was performed using a Senarmon method with a light of 546 nm using a polarizing microscope.

Reference Example 1 (Synthesis of CLC-A) In the same manner as in the method described in JP-B-63-41400, vinyl monomers represented by the following formulas (6) and (7) were mixed at a mixing ratio of 7: 3. By reacting with pentamethylcyclopentasiloxane, a cyclic pentasiloxane liquid crystal compound (CL
CA) was obtained.

Embedded image

Embedded image The glass transition temperature of this CLC-A was 14 ° C., the transition temperature to an isotropic phase was 114 ° C., and a cholesteric phase was shown at 14 ° C. to 114 ° C. As a result of extrapolating from the measured value of the selective reflection wavelength of the composition of CLC-A and the nematic liquid crystal, the selective reflection wavelength of CLC-A alone was 280 nm. From this wavelength, the cholesteric phase helical pitch of CLC-A is calculated to be 0.2 μm.

COMPARATIVE EXAMPLE 1 A liquid crystal display device having a structure in which a TFT liquid crystal cell is sandwiched between polarizing plates is used to display black and white stripes. Observations were made on the coloring of the display. As a result, the inverted display is observed when viewed from the angle of 60 ° or more with respect to the normal direction toward the lower side, and the white display is colored yellow when viewed from above or below. Looked.

Example 1 An acrylate-based ultraviolet-curable resin was formed on a triacetylcellulose base material so as to have regular ridge-like irregularities in the cross-sectional shape shown in FIG. The UV-curable resin was cured to obtain an alignment substrate. A 20% by weight solution of CLC-A in toluene was applied onto the alignment substrate. After evaporating the solvent, the mixture was heated to 80 ° C. to orient CLC-A to obtain an optically anisotropic film. When the retardation value of this film was measured while tilting the film about an axis parallel to the ridge-shaped unevenness, the tilt angle-retardation characteristic shown in FIG. 4 was shown.

Example 2 TFT used to display black and white stripes used in Comparative Example 1
TF of a liquid crystal display device in which a liquid crystal cell is sandwiched between polarizing plates
When the optically anisotropic film obtained in Example 1 is inserted between the T liquid crystal cell and the upper polarizing plate as shown in FIG. 5, when the black and white stripe display is viewed from an oblique direction,
Observation was made on the region where the display of black and white was inverted and the coloring of the display. As a result, when viewed from an angle of 60 ° or more with respect to the normal direction toward the upper side and 60 ° or more with respect to the normal direction toward the upper left, the display becomes dark, and the stripe cannot be distinguished. Since the inversion display was eliminated and the whitening of the black display and the coloring of the display were suppressed, the viewing angle was widened as compared with the TFT liquid crystal display device without the compensator of Comparative Example 1 alone.

Comparative Example 2 The same CLC-A toluene used in Example 1 as 20 w
% Solution was spin-coated on a glass substrate laminated with rubbed polyvinyl alcohol. The obtained liquid crystal oligomer film was cloudy, and was not oriented at all when observed with a polarizing microscope. Next, the liquid crystal oligomer film was heated at 80 ° C. for 5 minutes, and then irradiated with ultraviolet rays using a high-pressure mercury lamp so that the integrated light amount became 0.5 J / cm ² .

The thickness of the obtained optically anisotropic film was 2 μm.
m was 2.5 times the cholesteric phase spiral pitch, and no coloring due to selective reflection of visible light was observed. The rotation axis is the direction perpendicular to the rubbing direction and including the substrate surface,
As a result of measuring the retardation, it showed the retardation characteristics shown in FIG. 6, and the cholesteric phase spiral axis was oriented substantially parallel to the substrate normal.

Comparative Example 3 The optically anisotropic film obtained in Comparative Example 2 was inserted between a polarizing plate and a TFT liquid crystal cell displaying a black and white stripe, and the same observation as in Example 2 was performed. As a result, the inverted display is observed when viewed from the angle of 60 ° or more with respect to the normal direction toward the lower side, and the white display is colored yellow when viewed from above or below. The display characteristics were not so much improved as compared with the case where the optically anisotropic body was not attached (Comparative Example 1).

[0051]

The optically anisotropic body of the present invention has an orientation for compensating for birefringence caused by the orientation of liquid crystal molecules in a liquid crystal cell, and the orientation involves a complicated substrate manufacturing process such as oblique evaporation. It is an optically anisotropic body that can obtain a desired alignment structure by a simple process without using it and exhibits excellent optical compensation performance. By applying the optically anisotropic body to a TN-type, TFT-type, or STN-type liquid crystal display device, the display characteristics of the liquid crystal display device, particularly, the viewing angle characteristics can be significantly improved, so that the industrial value is large.

[Brief description of the drawings]

FIG. 1 is a straight line connecting two valleys and a line connecting a point on one valley through a point on the ridge to a point on the other valley. FIG. 3 is a perspective view showing a case where a figure surrounded by is substantially triangular.

FIG. 2 is a perspective view showing a case where a cross section perpendicular to the ridge line of the ridge-shaped unevenness is a wavy line.

FIG. 3 is a diagram showing a cross-sectional structure of ridge-shaped irregularities formed on the surface of an alignment base material used in Example 1.

FIG. 4 is a view showing retardation characteristics in Example 1.

FIG. 5 shows a polarizing plate, a TFT liquid crystal cell,
FIG. 3 is a perspective view showing a positional relationship of an optically anisotropic body.

FIG. 6 is a diagram showing retardation characteristics in Comparative Example 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ridge line 2 ... Valley line 3 ... Upper polarizing plate 4 ... Optically anisotropic body in Example 1 (triacetyl cellulose surface is on the upper polarizing plate side) 5 ... TFT liquid crystal cell 6. ..Lower polarizing plate 7: Triacetyl cellulose base material 8: Cured product of ultraviolet curable resin 9: CLC-A

Claims (9)

[Claims] 1. An optically anisotropic body having a substrate having ridge-shaped irregularities on its surface and a layer containing an optically anisotropic compound, wherein the ridge-shaped irregularities have a valley line of a concave portion and a ridge line of a convex portion. It is formed almost parallel and periodically, and the average value of the period is 200 μm
0.5 μm or more, the average value of the height difference between the ridge line of the ridge-shaped unevenness and the ridge line of the convex portion is not more than 5 times the average value of the period of the ridge-shaped unevenness and 0.3 times or more, and When cut along a plane perpendicular to the ridge line of the convex portion, the cross-sectional shape of the ridge-shaped unevenness is a shape connected by a combination of straight lines and / or curves, and is based on the distance between the ridge line and the valley lines on both sides thereof. When projected onto a material surface, one projection line is at least twice as large as the other projection line, and the optical anisotropy is formed directly on the substrate having the ridge-shaped irregularities or through one or more intermediate layers. An optically anisotropic body comprising a compound layer formed thereon. 2. The optically anisotropic body according to claim 1, wherein the intermediate layer is an alignment film. 3. A cross section of one ridge including a convex portion, which is perpendicular to the ridge line, passes through a straight line connecting points on two valley lines and a point on one valley line through a point on the ridge line and a point on the other valley line. 3. The optically anisotropic body according to claim 1, wherein a figure surrounded by a line connecting the points forms a substantially triangle. 4. The optically anisotropic body according to claim 1, wherein the optically anisotropic compound is a liquid crystalline compound. 5. The optically anisotropic body according to claim 1, wherein the orientation is fixed by polymerization of the optically anisotropic compound. 6. An optically anisotropic compound is added with a polymerizable low molecule, and the orientation is fixed by polymerizing the optically anisotropic compound and a polymerizable low molecule or only the polymerizable low molecule. The optically anisotropic body according to claim 1, wherein: 7. The optically anisotropic body according to claim 1, wherein the optically anisotropic compound is a cholesteric liquid crystal. 8. The optically anisotropic material according to claim 1, wherein the optically anisotropic compound is a liquid crystal having a nematic phase or a smectic phase. 9. A liquid crystal display device using the optically anisotropic material according to claim 1.