JP2000250043A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the display contrast, to widen the viewing angle and to obtain fast display by continuously verying the tilt angle to the major axes of rodlike liquid crystal molecules in such a manner it reaches a max. near two alignment films and a min. in the middle between the alignment films. SOLUTION: As for rodlike liquid crystal molecules 1a to 1h used for a liquid crystal layer 1, rodlike nematic liquid crystal molecules having negative dielectric anisotropy are used. The alignment films 2a, 2b have a function to align the rodlike liquid crystal molecules 1a to 1h. The rubbing direction of the alignment films 2a, 2b is substantially parallel to each other. The rodlike liquid crystal molecules 1a, 1h near the substrates 4a, 4b are aligned so that the tilt angle of the major axis direction becomes max. (almost perpendicular to the layer). The rodlike liquid crystal molecules 1d, 1e in the middle portion between the two alignment films 2a, 2b (near the line X-X) are aligned so that the tilt angle of the major axis direction becomes min. (almost horizontal). The directions of two polarizers 17, 18 are substantially perpendicular to each other, and the direction of each polarizing axis makes substantially 45 deg. angle from the rubbing direction of the alignment films 2a, 2b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lower polarizing element, a lower substrate,
A transmission type liquid crystal display device in which a lower transparent electrode, a lower alignment film, an upper alignment film, an upper transparent electrode, an upper substrate, and an upper polarizing element are arranged in this order, and a rod-like nematic liquid crystal molecule is sealed in a gap between the two alignment films. About.

[0002]

2. Description of the Related Art A transmission type liquid crystal display device comprises a liquid crystal cell and two polarizing elements disposed on both sides thereof. The liquid crystal cell is composed of rod-like liquid crystal molecules and two substrates for enclosing the molecules. The substrate is provided with a transparent electrode for applying a voltage to the rod-like liquid crystalline molecules and an alignment film for aligning the rod-like liquid crystalline molecules. Various display modes have been proposed for liquid crystal cells in which the alignment state of rod-like liquid crystal molecules is different. As a transmission type liquid crystal display device, TN (Twis
ted Nematic), IPS (In-Plane Switching), FL
C (Ferroelectric Liquid Crystal), OCB (Optica)
lly Compensatory Bend), STN (Supper Twisted Ne)
matic) or VA (Vertically Aligned) mode has already been proposed.

[0003] US Pat. No. 4,583,825 describes that
A transmission type liquid crystal display device using the above OCB mode liquid crystal cell is disclosed. In the OCB mode liquid crystal cell,
The rod-like liquid crystal molecules are symmetrically oriented with the middle of the two alignment films as the symmetry plane, and the tilt angle in the major axis direction of the rod-like liquid crystal molecules is minimized (nearly horizontal alignment) near the two alignment films and the two. It changes continuously so that it becomes maximum (substantially vertical alignment) in the middle of one alignment film. Since the rod-like liquid crystal molecules are symmetrically aligned as described above, the OCB mode liquid crystal cell has a self-optical compensation function. Therefore, a transmissive liquid crystal display device using an OCB mode liquid crystal cell is characterized by a wide viewing angle.

[0004] US Pat. No. 5,410,422 discloses that O
An improved invention of a transmission type liquid crystal display device using a symmetric type liquid crystal cell such as a CB mode is disclosed. US Patent 541
FIG. 12 of the specification of No. 0422 shows a symmetric liquid crystal cell other than the known OCB mode liquid crystal cell (FIG. 12C), in which rod-like liquid crystal molecules are symmetrically aligned with the middle of two alignment films as the symmetry plane. And the tilt angle in the major axis direction of the rod-like liquid crystal molecules changes continuously so that it becomes maximum near the two alignment films (almost vertical alignment) and minimum between the two alignment films (almost horizontal alignment). The liquid crystal cell is shown (FIG. 12B).

[0005]

SUMMARY OF THE INVENTION US Pat.
FIG. 12B of the specification No. 2 shows that the rod-like liquid crystal molecules are symmetrically oriented with the middle of the two alignment films as the symmetry plane, and the inclination angle in the major axis direction of the rod-like liquid crystal molecules is near the two alignment films. The liquid crystal cell continuously changes so as to have a maximum (substantially vertical alignment) and a minimum (substantially horizontal alignment) between the two alignment films is shown in the figure. No description is given in US Pat. No. 5,410,422 at all about how the liquid crystal display device is aligned and how it is specifically configured.

An object of the present invention is to provide a liquid crystal display device having a high display contrast, a wide viewing angle, and capable of high-speed display. Further, an object of the present invention is that the rod-like liquid crystal molecules are symmetrically oriented with the middle of the two alignment films as the symmetry plane, and the inclination angle of the rod-like liquid crystal molecules in the major axis direction is near the two alignment films. Another object of the present invention is to specifically realize a liquid crystal display device using a liquid crystal cell which continuously changes so as to have a maximum (substantially vertical alignment) and a minimum (substantially horizontal alignment) between two alignment films.

[0007]

The object of the present invention has been attained by the following liquid crystal display devices (1) to (3). (1) A lower polarizing element, a lower substrate, a lower transparent electrode, a lower alignment film, an upper alignment film, an upper transparent electrode, an upper substrate, and an upper polarizing element are arranged in this order, and rod-like nematic liquid crystal molecules are disposed in a gap between the two alignment films. Wherein the rod-shaped nematic liquid crystal molecules have negative dielectric anisotropy, the rubbing directions of the two alignment films are substantially parallel, and the rod-shaped nematic liquid crystal molecules are Are symmetrically oriented with the middle of the two alignment films as the symmetry plane, and the long-axis tilt angle of the rod-shaped nematic liquid crystalline molecule is maximum near the two alignment films and minimum in the middle of the two alignment films. Are continuously changed so that the directions of the polarization axes of the two polarizing elements are substantially orthogonal, and
A liquid crystal display device wherein the angle between the direction of each polarization axis and the rubbing direction of the alignment film is substantially 45 °. (2) The liquid crystal display according to (1), wherein an optically anisotropic element having negative birefringence is arranged between the lower polarizing element and the lower substrate or between the upper substrate and the upper polarizing element. apparatus. (3) The liquid crystal display according to (2), wherein the optically anisotropic element is a layer formed from discotic liquid crystal molecules.

[0008] No particular name is defined for the liquid crystal cell (from the lower substrate to the upper substrate) in the alignment state defined in the above (1). In this specification, the liquid crystal cell in this alignment state is referred to as a splay alignment cell. In this specification, “substantially perpendicular”, “substantially parallel” or “substantially 45 °” means that the angle is within a range of less than ± 5 ° from a strict angle. This range is preferably less than ± 4 °, more preferably less than ± 3 °, even more preferably less than ± 2 °, and most preferably less than ± 1 °.

[0009]

According to the present invention, according to the specific structure defined in the above (1), the rod-like liquid crystal molecules are symmetrically oriented with the middle of the two alignment films as the symmetry plane. The inclination angle in the major axis direction is maximum near the two alignment films (almost vertical alignment) and minimum between the two alignment films (almost horizontal alignment).
Thus, a liquid crystal display device using a liquid crystal cell that changes continuously as shown in FIG. When the inventor examined the performance of this liquid crystal display device, it has a wide viewing angle. It is considered that a wide viewing angle is obtained by the self-optical compensation function of the symmetric liquid crystal cell. Further, when this liquid crystal display device was compared with a liquid crystal display device using an OCB mode liquid crystal cell which is a conventionally known symmetric liquid crystal cell, it was found that the display contrast was high and the response speed was high. As a result, the liquid crystal display device of the present invention has a high display contrast, a wide viewing angle, and
The feature is that high-speed display is possible. The liquid crystal display device of the present invention is characterized by having a wide viewing angle, but the viewing angle can be further expanded by using an appropriate optically anisotropic element. According to the study of the present inventor, an optically anisotropic element suitable for this liquid crystal display device is an optically anisotropic element having negative birefringence, and specifically formed from discotic liquid crystal molecules. Turned out to be a layer. By using such an optically anisotropic element in the liquid crystal display device of the present invention, a very wide viewing angle can be achieved.

[0010]

FIG. 1 is a cross-sectional view schematically showing the orientation of a liquid crystal compound in a splay alignment liquid crystal cell. As shown in FIG. 1, the splay alignment liquid crystal cell includes a lower substrate (4
a), a lower transparent electrode (3a), a lower alignment film (2a), a liquid crystal layer (1), an upper alignment film (2b), an upper transparent electrode (3b), and an upper substrate (4b). Have. As the rod-like liquid crystal molecules (1a to 1h) used in the liquid crystal layer (1), rod-like nematic liquid crystal molecules having negative dielectric anisotropy are used. The alignment films (2a, 2b) have a function of aligning the rod-like liquid crystal molecules (1a to 1h). RDa and RDb are rubbing directions of the alignment film. As shown in FIG. 1, the rubbing directions of the two alignment films are substantially parallel. The transparent electrodes (3a, 3b) have a function of applying a voltage to the rod-like liquid crystal molecules (1a to 1h).

When the voltage applied to the splay alignment liquid crystal cell is low, as shown in off of FIG.
The rod-shaped liquid crystalline molecules (1a to 1d) on the a) side and the upper substrate (4
The rod-like liquid crystalline molecules (1e to 1h) on the b) side are oriented substantially in the opposite direction (vertically symmetric) with the middle (XX) of the two alignment films as the plane of symmetry. In addition, the substrates (4a, 4a,
b) The rod-like liquid crystal molecules (1a, 1h) in the vicinity are oriented so that the tilt angle in the long axis direction becomes maximum (substantially vertical), and the rod-like liquid crystal in the middle of the two alignment films (near XX). Sex molecules (1
d, 1e) are oriented such that the inclination angle in the long axis direction is minimum (substantially horizontal). The intermediate rod-like liquid crystal molecules (1b, 1c, 1f, 1g) have their tilt angles in the major axis direction continuously changing. As shown in on in FIG. 1, when the applied voltage is high, the rod-like liquid crystalline molecules (1a, 1h) near the substrates (4a, 4b) remain aligned almost vertically. Further, the rod-like liquid crystal molecules (1d, 1e) in the middle (near XX) of the two alignment films also remain substantially horizontally aligned.
The liquid crystal molecules (1b, 1c, 1f, 1g) located in the middle of the liquid crystal molecules change their orientation with an increase in the voltage, and they are more horizontally oriented than in the off state. However, the rod-like liquid crystal molecules (1a to 1d) on the lower substrate (4a) side of the liquid crystal cell and the rod-like liquid crystal molecules (1e to 1h) on the upper substrate (4b) side are located in the middle (X) of the two alignment films. The orientation in the substantially opposite direction (vertically symmetric) with -X) as the plane of symmetry is the same as in the off state.

FIG. 2 is a schematic diagram of a liquid crystal display device using a splay alignment liquid crystal cell. The liquid crystal display device shown in FIG. 2A includes a splay alignment liquid crystal cell (10), a pair of polarizing elements (11a, 11b) provided on both sides of the liquid crystal cell, and a backlight (BL). The splay alignment liquid crystal cell (10) corresponds to the liquid crystal cell shown in FIG. Upper and lower rubbing directions (RDa, RD) of the liquid crystal cell (10)
b) is in the same direction (parallel). Lower polarizing element (11
The angle between the direction of the polarization axis (a) in (a) and the rubbing direction (RDa, RDb) of the alignment film of the liquid crystal cell (10) is 4
5 ゜. The direction of the polarization axis of the upper polarizing element (11a) (P
Ab) and the rubbing direction (R) of the alignment film of the liquid crystal cell (10).
Da, RDb) is also 45 °. The direction (PAa) of the polarization axis of the lower polarizing element (11a) and the direction (PAb) of the polarization axis of the upper polarizing element (11a) are orthogonal to each other, and are in a crossed Nicols arrangement. FIG. 2 (b)
Is a splay alignment liquid crystal cell (1).
0), a pair of polarizing elements (1
1a, 11b), a pair of optically anisotropic elements (12a, 12b) and a backlight (BL) arranged between a liquid crystal cell and a polarizing plate. Optically anisotropic element (12
a, 12b) may be arranged only on one side. Splay alignment liquid crystal cell (10) and polarizing elements (11a, 11a)
The arrangement of b) is the same as that of FIG. When the optically anisotropic element is a layer formed from discotic liquid crystal molecules, the arrows (RDc, RDd) shown on the optically anisotropic elements (12a, 12b) indicate the rubbing direction of the liquid crystal molecules. Is equivalent to

FIG. 3 is a conceptual diagram showing optical compensation of a splay alignment liquid crystal cell by an optically anisotropic element. If the splay alignment liquid crystal cell is optically compensated using an optically anisotropic element having negative birefringence, the viewing angle of the splay alignment liquid crystal cell can be further increased. The optically anisotropic element is preferably a layer formed from the discotic liquid crystal molecules shown in FIG. In FIG. 3A, the splay alignment liquid crystal cell (10) is replaced with an optically anisotropic element (12a, 12a) formed from discotic liquid crystal molecules.
Optically compensated by b). Optically anisotropic element (12
The rubbing directions (RDc, RDd) of the rubbing directions (RDa, RDd) of the splay alignment liquid crystal cell (10)
RDb), the rod-like liquid crystal molecules of the liquid crystal cell (10) and the optically anisotropic element (12
The discotic liquid crystal molecules a) and 12b) correspond (a to f) to optically compensate.

As shown in FIG. 3B, as an optically anisotropic element, an optically compensatory sheet having a layer formed of discotic liquid crystalline molecules on a polymer film having optical anisotropy is used. When used, the splay alignment liquid crystal cell can be more effectively optically compensated. In FIG. 3B, the splay-aligned liquid crystal cell (10) is made of a layer (12a, 12b) formed of discotic liquid crystalline molecules and a polymer film (13a, 13) having optical anisotropy.
b) cooperates with optical compensation. Liquid crystal cell (1
0) and the optically anisotropic element (12a, 1)
2b) Correspondence with discotic liquid crystalline molecules (a
To f) are the same as those in FIG. For the rod-like liquid crystal molecules that are substantially horizontally aligned at the center of the splay alignment liquid crystal cell (10), a polymer film (1) is further added.
The optical anisotropy of 3a, 13b) is designed to correspond (g, h). In addition, the polymer film (13
The ellipses described in a and 13b) are refractive index ellipses caused by the optical anisotropy of the polymer film.

[Splay Alignment Liquid Crystal Cell] The substrate and the transparent electrode used for the splay alignment liquid crystal cell are the same as other known alignment mode liquid crystal cells. Commercial products (for example, ITO
A glass substrate provided with a transparent electrode) may be used.
As the alignment film, a vertical alignment film having a function of substantially vertically aligning rod-like liquid crystalline molecules near the alignment film is used. Examples of the vertical alignment film of rod-like liquid crystal molecules include a solution coating type (including a liquid crystal dissolution injection type), a plasma polymerization type, and a sputtering type alignment film. Examples of solution-applied vertical alignment agents include lecithin, stearic acid, octadecylmalonic acid, hexadecyltrimethylammonium bromide,
Octadecylamine hydrochloride, monobasic chromium carboxylate complex (eg, chromium myristate complex, chromium perfluorononanoate complex) and organic silane (eg,
N, N-dimethyl-N-octadecyl-3-aminopropyltrimethoxysilyl chloride). Examples of plasma-polymerized vertical alignment agents include hexamethyldisiloxane, perfluorodimethylcyclohexane, and tetrafluoroethylene. Examples of the vertical alignment agent of the sputtering type include polytetrafluoroethylene. A rubbing process is performed on the formed vertical alignment film as shown in FIG. In the splay alignment liquid crystal cell, even in the vicinity of the alignment film where the tilt angle becomes the maximum, the rod-like liquid crystal molecules are not tilted completely vertically (90 °) but pretilt in a certain direction. The pretilt direction of the rod-like liquid crystal molecules matches the direction of the rubbing treatment. The rubbing treatment can be performed in the same manner as a known treatment for an alignment film.

Two substrates provided with a transparent electrode and a vertical alignment film are bonded via a spacer so that the rubbing directions are parallel. In the gap created by the spacer,
A splay alignment liquid crystal cell is prepared by injecting rod-like liquid crystal molecules. As the rod-like liquid crystal molecules, nematic liquid crystal molecules having negative dielectric anisotropy are used. Examples of rod-like liquid crystalline molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenyl Includes pyrimidines, phenyldioxane, tolanes and alkenylcyclohexylbenzonitrile. The rod-like liquid crystal molecule is composed of two or more rings, a linking group connecting the rings, and a substituent thereof. It is known that the dielectric anisotropy is greatly affected by the linking group and the substituent. As a nematic liquid crystal molecule having a negative dielectric anisotropy, an alkylcyclohexylcarbonitrile compound is typical, and a commercially available product (for example, MJ95785, M
X94296, MJ941296) can also be used. It is preferable that the difference in retardation between on and off of the splay alignment liquid crystal cell be approximately half the wavelength of light. The splay alignment liquid crystal cell can be used in either a normally white mode in which black display is performed when on or a normally black mode in which black display is performed when off.

[Polarizing Element] A polarizing element generally comprises a polarizing film and protective films disposed on both sides thereof. However, when an optically anisotropic element (described later) is used, a polymer film of the optically anisotropic element can function as a protective film on the liquid crystal cell side. As the transparent protective film provided separately from the polymer film of the optically anisotropic element, it is preferable to use an optically isotropic polymer film described later, particularly, a triacetyl cellulose film. The polarizing film includes an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally manufactured using a polyvinyl alcohol-based film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film. The directions of the polarization axes of the two polarizing elements are made substantially orthogonal. The angle between the direction of each polarization axis and the rubbing direction of the alignment film of the liquid crystal cell is adjusted to be substantially 45 °.

[Optical Anisotropic Element] The splay alignment liquid crystal cell is characterized by having a wide viewing angle, but the viewing angle can be further expanded by using an appropriate optically anisotropic element. One or two optically anisotropic elements are arranged between the liquid crystal cell and one or both polarizing elements. The optically anisotropic element preferably has negative birefringence as the optical property. Further, it is preferable that the inclination angle of the optical axis with respect to the normal direction of the film is changed so as to be minimum on the liquid crystal cell side and maximum on the polarizing element side. The change in the tilt angle may be discontinuous. Further, the inclination angle of the optical axis is preferably 40 to 80 °. Furthermore, the average direction of the orthogonal projection of the optical axis onto the liquid crystal cell and the rubbing direction of the liquid crystal cell are preferably substantially parallel (0 °) or substantially antiparallel (180 °). The optically anisotropic element includes (1) an optically anisotropic polymer film,
(2) a laminate of an optically isotropic polymer film and an optically anisotropic layer formed from liquid crystal molecules, and (3) an optically anisotropic polymer film and an optically formed layer formed from liquid crystal molecules. It can be classified into a laminate with an anisotropic layer. The optically anisotropic polymer films (1) and (3) may be composed of a laminate of an optically anisotropic polymer film and an optically isotropic polymer film. In the laminate of (2) and (3), the polymer film is disposed on the polarizing film side (outside), and the optically anisotropic layer is disposed on the liquid crystal cell side (inside). Hereinafter, an optically isotropic polymer film, an optically anisotropic polymer film, and an optically anisotropic layer formed from liquid crystal molecules will be described in this order.

[Optically Isotropic Polymer Film] The optically isotropic polymer film preferably has a light transmittance of 80% or more. Specifically, the optical isotropy has an in-plane retardation (Re) of preferably 10 nm or less, more preferably 5 nm or less.
The thickness direction retardation (Rth) is 40 n
m or less, more preferably 20 nm or less. The in-plane retardation (Re) and the retardation in the thickness direction (Rth) are respectively defined by the following equations. Re = (nx−ny) × d Rth = [{(nx + ny) / 2} −nz] × d where nx and ny are in-plane refractive indices of the polymer film, and nz is a thickness direction of the polymer film. Is the refractive index, and d is the thickness of the polymer film. As the optically isotropic polymer, the cellulose ester is preferably a cellulose ester, more preferably acetyl cellulose, and most preferably triacetyl cellulose. The polymer film is preferably formed by a solvent casting method. The thickness of the optically isotropic polymer film is preferably from 20 to 500 μm, more preferably from 50 to 200 μm.
In order to improve the adhesion between the optically isotropic polymer film and the layer provided thereon (adhesive layer, alignment film or optically anisotropic layer), the polymer film is subjected to a surface treatment (eg, glow discharge treatment, corona discharge). Treatment, ultraviolet (UV) treatment, and flame treatment). On the polymer film,
An adhesive layer (undercoat layer) may be provided.

[Optically Anisotropic Polymer Film] The optically anisotropic polymer film preferably has a light transmittance of 80% or more. Specifically, the term “anisotropic” means that the in-plane retardation (Re) is preferably 20 nm or more, and more preferably 40 nm or more. The thickness direction retardation (Rth) is 60 nm.
It is preferably at least 80 nm, more preferably at most 80 nm. As the optically anisotropic polymer film used in combination with the optically anisotropic layer formed from liquid crystal molecules as in the above (3), conventionally, a main chain such as polycarbonate, polysulfone or polyethersulfone has been used. A film having a substantially optically positive uniaxial property and comprising a polymer having an aromatic ring on the side has been used.
However, when the present inventor studied a splay alignment cell, a film substantially having optical negative uniaxiality was obtained.
It has been found that the splay alignment cell is suitable for optical compensation. A film substantially having an optical negative uniaxial property is
It can be formed from a polymer having an aromatic ring on the side chain such as polystyrene. In a polymer film having "substantially optically uniaxial", one optical axis is stronger than the other optical axis and can be regarded as substantially uniaxial even though it shows biaxiality. Polymer films are included. Preferably, the optical axis is substantially parallel to the plane of the polymer film. In other words, it is particularly preferable to use a polymer film having a refractive index ellipse shown in FIG.

The optically anisotropic polymer film is preferably formed from a styrene-based polymer. Styrene polymers include styrene and other vinyl monomers (eg,
Copolymers with acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylamide, methacrylamide) and polymers of styrene derivatives (monomers in which the benzene ring of styrene is substituted) are included.
Optical anisotropy can be obtained by stretching a polymer film. The stretching direction and the direction of the optical axis are substantially parallel. Since the polymer film preferably has optical uniaxiality, uniaxial stretching is preferable. The direction of the optical axis is
Preferably, it is substantially parallel to the rubbing direction of the liquid crystal cell. The thickness of the optically anisotropic polymer film is 20
To 500 μm, preferably 50 to 200 μm.
More preferably, it is μm. In order to improve the adhesion between the optically anisotropic polymer film and the layer provided thereon (adhesive layer, alignment film or optically anisotropic layer), the polymer film is subjected to a surface treatment (eg, glow discharge treatment, corona discharge). Treatment, ultraviolet (UV) treatment, and flame treatment). An adhesive layer (undercoat layer) on the polymer film
May be provided.

[Optical Anisotropic Layer Formed from Liquid Crystalline Molecules] As the liquid crystal molecules, rod-like liquid crystal molecules or discotic liquid crystal molecules are preferable, and discotic liquid crystal molecules are particularly preferable. Examples of rod-like liquid crystal molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxane, tolan and alkenylcyclohexylbenzonitrile are preferably used. Not only low molecular liquid crystal molecules as described above but also high molecular liquid crystal molecules can be used. The high-molecular liquid crystal molecules are polymers having side chains corresponding to the low-molecular liquid crystal molecules described above. An optical compensatory sheet using high-molecular liquid crystalline molecules is described in JP-A-5-53016.

It is preferable that the discotic liquid crystal molecules are fixed in the layer while keeping the alignment state. More preferably, the discotic liquid crystalline molecules are fixed by a polymerization reaction. Discotic liquid crystalline molecules are described in various literatures (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vo.
l. 71, page 111 (1981); edited by The Chemical Society of Japan, quarterly chemistry review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2
(1994); B. Kohne et al., Angew. Chem. Soc. Chem. C
omm., page 1794 (1985); J. Zhang et al., J. Am. Che
m. Soc., vol. 116, page 2655 (1994)). Regarding the polymerization of discotic liquid crystalline molecules,
It is described in JP-A-8-27284. In order to fix the discotic liquid crystal molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystal molecules. However, when a polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain an oriented state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystal molecule is preferably a compound represented by the following formula (I).

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

[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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In the formula (I), the divalent linking group (L)
Is an alkylene group, alkenylene group, arylene group,-
It is preferably a divalent linking group selected from the group consisting of CO-, -NH-, -O-, -S- and a combination thereof. The divalent linking group (L) includes an alkylene group, an alkenylene group, an arylene group, -CO-, -NH-,-
More preferably, the group is a group obtained by combining at least two divalent groups selected from the group consisting of O- and -S-. The divalent linking group (L) is most preferably a group obtained by combining at least two divalent groups selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, -CO- and -O-. The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The arylene group preferably has 6 to 10 carbon atoms. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group, a halogen atom, a cyano, an alkoxy group, an acyloxy group). Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (P). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group.

L1: -AL-CO-O-AL- L2: -AL-CO-O-AL-O- L3: -AL-CO-O-AL-O-AL- L4: -AL-CO-O -AL-O-CO-L5: -CO-AR-O-AL-L6: -CO-AR-O-AL-O-L7: -CO-AR-O-AL-O-CO-L8: -CO -NH-AL-L9: -NH-AL-O-L10: -NH-AL-O-CO-L11: -O-AL-L12: -O-AL-O-L13: -O-AL-O- CO-

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

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

[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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The polymerizable group (P) is an unsaturated polymerizable group (P
1, P2, P3, P7, P8, P15, P16, P1
7) or an epoxy group (P6, P18), more preferably an unsaturated polymerizable group,
Ethylenically unsaturated polymerizable groups (P1, P7, P8, P1
5, P16, P17). In the formula (I), n is an integer of 4 to 12. Specific numbers are determined according to the type of discotic core (D). The combination of a plurality of L and P may be different, but is preferably the same.

Two or more discotic liquid crystal molecules may be used in combination. For example, the polymerizable discotic liquid crystal molecules and the non-polymerizable discotic liquid crystal molecules described above can be used in combination. The non-polymerizable discotic liquid crystal molecule is preferably a compound in which the polymerizable group (P) of the polymerizable discotic liquid crystal molecule is changed to a hydrogen atom or an alkyl group. That is, the non-polymerizable discotic liquid crystalline molecule is preferably a compound represented by the following formula (II). (II) D (-LR) _{n wherein} D is a discotic core; L is a divalent linking group; R is a hydrogen atom or an alkyl group;
Is an integer of 4 to 12. An example of the discotic core (D) of formula (II) is that LP (or PL) is replaced by LR (or R
Except for changing to L), it is the same as the example of the polymerizable discotic liquid crystal molecule described above. Further, a divalent linking group (L)
Is the same as the example of the polymerizable discotic liquid crystal molecule described above. The alkyl group represented by R has 1 to 4 carbon atoms.
It is preferably 0, more preferably 1 to 30. A chain alkyl group is more preferable than a cyclic alkyl group, and a straight-chain alkyl group is more preferable than a branched chain alkyl group. R is particularly preferably a hydrogen atom or a linear alkyl group having 1 to 30 carbon atoms.

The optically anisotropic layer is composed of liquid crystal molecules or the following polymerizable initiators and optional additives (eg, plasticizers, monomers, surfactants, cellulose esters, 1,3,5-
It is formed by applying a coating solution containing a triazine compound and a chiral agent) on the alignment film. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethylsulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, ,
Chloroform, dichloromethane), ester (eg, methyl acetate, butyl acetate), ketone (eg, acetone, methyl ethyl ketone), ether (eg, tetrahydrofuran,
1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The application of the coating solution can be performed by a known method (eg, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method).

The polymerization reaction of liquid crystal molecules includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. Photopolymerization reactions are preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (U.S. Pat.
Nos. 1 and 2367670), acyloin ether (described in US Pat. No. 2,448,828),
α-hydrocarbon-substituted aromatic acyloin compounds (U.S. Pat.
No. 722512), polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), and a combination of a triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 35493).
No. 67), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat.
9850) and an oxadiazole compound (described in US Pat. No. 4,221,970).
The amount of the photopolymerization initiator used is preferably 0.01 to 20% by weight, more preferably 0.5 to 5% by weight of the solid content of the coating solution. Light irradiation for the polymerization of discotic liquid crystalline molecules preferably uses ultraviolet light. The irradiation energy is 20 mJ / cm ^{2 to} 5
0 J / cm ² , preferably 100 to 800
More preferably, it is mJ / cm ² . Light irradiation may be performed under heating conditions to promote the photopolymerization reaction. The thickness of the optically anisotropic layer is preferably from 0.1 to 20 μm, more preferably from 0.5 to 15 μm, and most preferably from 1 to 10 μm.

The alignment state of the liquid crystal molecules in the optically anisotropic layer is, specifically, the type of the liquid crystal molecules, the type of the alignment film, and the additives (eg, plasticizers) in the optically anisotropic layer. , Binders and surfactants). As the alignment state of the discotic liquid crystal molecules in the optically anisotropic layer, the average tilt angle between the disc surface of the discotic liquid crystal molecules and the plane of the polymer film is 5 to 85 °, and the discotic liquid crystal molecules In general, when the distance between the molecule and the polymer film surface is increased, the alignment (hybrid alignment) is performed so that the inclination angle between the discotic liquid crystal molecules and the plane of the polymer film increases. However, the present inventor studied the splay alignment cell, and found that the average tilt angle between the discotic liquid crystal molecules and the plane of the polymer film was 5 to 85 °, and that the discotic liquid crystal molecules and the polymer film surface were not aligned. When the distance between the discotic liquid crystal molecules and the plane of the polymer film decreases, the orientation (reverse hybrid orientation) is more suitable for the optical compensation of the splay alignment cell. There was found.

In order to realize the above-mentioned reverse hybrid alignment, a vertical alignment film for discotic liquid crystal molecules described later is used, and a cellulose ester or a fluorine-containing surfactant is further added to the optically anisotropic layer. Is preferred. Furthermore, it is preferable to align the discotic liquid crystalline molecules while blowing hot air on the surface of the optically anisotropic layer opposite to the alignment film. The direction of the warm air is preferably parallel to the plane of the polymer film and parallel to the rubbing direction of the alignment film. Cellulose esters include lower fatty acid esters of cellulose and nitrocellulose. Preferred are lower fatty acid esters of cellulose. The “lower fatty acid” in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms.
The number of carbon atoms is preferably 2 to 5, more preferably 2 to 4. A substituent (eg, hydroxy) may be bonded to the fatty acid. Two or more fatty acids may form an ester with cellulose. Examples of lower fatty acid esters of cellulose include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose hydroxypropionate,
Includes cellulose acetate propionate and cellulose acetate butyrate. Cellulose acetate butyrate is particularly preferred. The butyrylation degree of cellulose acetate butyrate is preferably 30% or more, and more preferably 30 to 80%.
The acetylation degree of cellulose acetate butyrate is 3
It is preferably 0% or less, more preferably 1 to 30%. The cellulose ester is preferably used in an amount of 0.1 to 5% by weight based on the amount of the discotic liquid crystalline molecules.

The fluorinated surfactant comprises a hydrophobic group containing a fluorine atom, a nonionic, anionic, cationic or amphoteric hydrophilic group and an optional linking group. The fluorinated surfactant comprising one hydrophobic group and one hydrophilic group is represented by the following formula (III). (III) Rf-L ⁵ -Hy wherein, Rf is selected from the group consisting monovalent hydrocarbon radicals substituted with a fluorine atom, L ⁵ is a single bond or a divalent linking group,
Hy is a hydrophilic group. Rf in formula (III) functions as a hydrophobic group. The hydrocarbon group is preferably an alkyl group or an aryl group. The alkyl group preferably has 3 to 30 carbon atoms, and the aryl group preferably has 6 to 30 carbon atoms. Some or all of the hydrogen atoms contained in the hydrocarbon group are substituted with fluorine atoms. It is preferable to replace 50% or more of the hydrogen atoms contained in the hydrocarbon group with a fluorine atom, more preferably 60% or more, and 70% or more.
It is more preferable to replace the above, and it is most preferable to replace 80% or more. The remaining hydrogen atoms may be further substituted with another halogen atom (eg, chlorine atom, bromine atom). Examples of Rf are shown below.

[0051] _{Rf1: n-C 8 F 17} - Rf2: n-C 6 F 13 - Rf3: Cl- (CF 2 -CFCl) 3 -CF 2 - Rf4: H- (CF 2) 8 - Rf5: H- _{(CF 2) 10 - Rf6:} n-C 9 F 19 - Rf7: pentafluorophenyl _{Rf8: n-C 7 F 15} - Rf9: Cl- (CF 2 -CFCl) 2 -CF 2 - Rf10: H- (CF _{2) 4 - Rf11: H- (} CF 2) 6 - Rf12: Cl- (CF 2) 6 - Rf13: C 3 F 7 -

In the formula (III), the divalent linking group is an alkylene group, an arylene group, a divalent heterocyclic residue, -CO
—, —NR— (R is an alkyl group having 1 to 5 carbon atoms or a hydrogen atom), —O—, —SO ₂ — and a divalent linking group selected from the combination thereof. preferable. An example of a L ⁵ of the formula (III) below. The left side is bonded to a hydrophobic group (Rf), and the right side is a hydrophilic group (Hf).
y). AL represents an alkylene group, AR represents an arylene group, and Hc represents a divalent heterocyclic residue. In addition, the alkylene group, the arylene group, and the divalent heterocyclic residue may have a substituent (eg, an alkyl group).

[0053] L0: single bond _{L51: -SO 2 -NR- L52: -AL} -O- L53: -CO-NR- L54: -AR-O- L55: -SO 2 -NR-AL-CO-O- L56: -CO-O- L57: -SO 2 -NR-AL-O- L58: -SO 2 -NR-AL- L59: -CO-NR-AL- L60: -AL-O-AL- L61: - _{hc-AL- L62: -SO 2 -NR} -AL-O-AL- L63: -AR- L64: -O-AR-SO 2 -NR-AL- L65: -O-AR-SO 2 -NR- L66 : -O-AR-0-

Hy in the formula (III) is a nonionic hydrophilic group,
It is any of an anionic hydrophilic group, a cationic hydrophilic group, and an amphoteric hydrophilic group. Nonionic hydrophilic groups are particularly preferred. Examples of Hy in the formula (III) are shown below.

Hy1:-(CH ₂ CH ₂ O) _n -H (n
Is an integer of 5 to _{30) Hy2 :-( CH 2 CH 2} O) n -R 1 (n is 5 to 3
0 integer, R ¹ is an alkyl group having 1 to 6 carbon _{atoms) Hy3 :-( CH 2 CHOHCH 2)} n -H (n is 5 to 30 integer) Hy4: -COOM (M represents a hydrogen atom, an alkali metal atom or dissociated state) Hy5: -SO ₃ M (M is a hydrogen atom, an alkali metal atom or dissociated _{state) Hy6 :-( CH 2 CH 2 O} ) n -CH 2 CH 2 CH 2
-SO ₃ M (n is 5 to 30 integer, M is a hydrogen atom or an alkali metal _{atom) Hy7: -OPO (OH) 2} Hy8: -N + (CH 3) 3 · X - (X represents a halogen atom) Hy9 : -COONH ₄

Nonionic hydrophilic groups (Hy1, Hy2, H
y3) is preferred, and a hydrophilic group (Hy1) composed of polyethylene oxide is most preferred. Specific examples of the fluorine-containing surfactant represented by the formula (III), shown with reference to examples of the above Rf, L ⁵ and Hy.

FS-1: Rf1-L51 (R = C ₃ H ₇ )
-Hy1 (n = 6) FS- 2: Rf1-L51 (R = C 3 H 7) -Hy1 (n
= 11) FS-3: Rf1 -L51 (R = C 3 H 7) -Hy1 (n
= 16) FS-4: Rf1 -L51 (R = C 3 H 7) -Hy1 (n
= 21) FS-5: Rf1 -L51 (R = C 2 H 7) -Hy1 (n
= 6) FS-6: Rf1 -L51 (R = C 2 H 7) -Hy1 (n
= 11) FS-7: Rf1 -L51 (R = C 2 H 7) -Hy1 (n
= 16) FS-8: Rf1 -L51 (R = C 2 H 7) -Hy1 (n
= 21) FS-9: Rf2 -L51 (R = C 3 H 7) -Hy1 (n
= 6) FS-10: Rf2 -L51 (R = C 3 H 7) -Hy1 (n
= 11) FS-11: Rf2 -L51 (R = C 3 H 7) -Hy1 (n
= 16) FS-12: Rf2 -L51 (R = C 3 H 7) -Hy1 (n
= 21) FS-13: Rf3 -L52 (AL = CH 2) -Hy1 (n
= 5) FS-14: Rf3 -L52 (AL = CH 2) -Hy1 (n
= 10) FS-15: Rf3 -L52 (AL = CH 2) -Hy1 (n
= 15) FS-16: Rf3 -L52 (AL = CH 2) -Hy1 (n
= 20) FS-17: Rf4 -L53 (R = C 3 H 7) -Hy1 (n
= 7) FS-18: Rf4 -L53 (R = C 3 H 7) -Hy1 (n
= 13) FS-19: Rf4 -L53 (R = C 3 H 7) -Hy1 (n
= 19) FS-20: Rf4 -L53 (R = C 3 H 7) -Hy1 (n
= 25)

FS-21: Rf5-L52 (AL = CH ₂ )
-Hy1 (n = 11) FS- 22: Rf5-L52 (AL = CH 2) -Hy1 (n
= 15) FS-23: Rf5 -L52 (AL = CH 2) -Hy1 (n
= 20) FS-24: Rf5 -L52 (AL = CH 2) -Hy1 (n
= 30) FS-25: Rf6-L54 (AR = p-phenylene)-Hy
1 (n = 11) FS-26: Rf6-L54 (AR = p-phenylene) -Hy
1 (n = 17) FS-27: Rf6-L54 (AR = p-phenylene) -Hy
1 (n = 23) FS-28: Rf6-L54 (AR = p-phenylene) -Hy
1 (n = 29) FS-29: Rf1-L55 (R = C ₃ H ₇ , AL = C
_{H 2) -Hy1 (n = 20} ) FS-30: Rf1-L55 (R = C 3 H 7, AL = C
_{H 2) -Hy1 (n = 30} ) FS-31: Rf1-L55 (R = C 3 H 7, AL = C
_{H 2) -Hy1 (n = 40} ) FS-32: Rf1-L56-Hy1 (n = 5) FS-33: Rf1-L56-Hy1 (n = 10) FS-34: Rf1-L56-Hy1 (n = 15) FS-35: Rf1-L56-Hy1 (n = 20) FS-36: Rf7-L56-Hy1 (n = 8) FS-37: Rf7-L56-Hy1 (n = 13) FS-38: Rf7- L56-Hy1 (n = 18) FS-39: Rf7-L56-Hy1 (n = 25)

FS-40: Rf1-L0-Hy1 (n = 6) FS-41: Rf1-L0-Hy1 (n = 11) FS-42: Rf1-L0-Hy1 (n = 16) FS-43: Rf1 -L0-Hy1 (n = 21) FS-44: Rf1-L51 (R = C 3 H 7) -Hy2 (n
_{^{= 7, R 1 = C 2}} H 5) FS-45: Rf1-L51 (R = C 3 H 7) -Hy2 (n
_{^{= 13, R 1 = C 2}} H 5) FS-46: Rf1-L51 (R = C 3 H 7) -Hy2 (n
_{^{= 20, R 1 = C 2}} H 5) FS-47: Rf1-L51 (R = C 3 H 7) -Hy2 (n
_{^{= 28, R 1 = C 2}} H 5) FS-48: Rf8-L52 (AL = CH 2) -Hy1 (n
= 5) FS-49: Rf8 -L52 (AL = CH 2) -Hy1 (n
= 10) FS-50: Rf8 -L52 (AL = CH 2) -Hy1 (n
= 15) FS-51: Rf8 -L52 (AL = CH 2) -Hy1 (n
= 20) FS-52: Rf1-L57 (R = C ₃ H ₇ , AL = CH ₂ C
_{H 2) -Hy3 (n = 5} ) FS-53: Rf1-L57 (R = C 3 H 7, AL = CH 2 C
_{H 2) -Hy3 (n = 7} ) FS-54: Rf1-L57 (R = C 3 H 7, AL = CH 2 C
_{H 2) -Hy3 (n = 9} ) FS-55: Rf1-L57 (R = C 3 H 7, AL = CH 2 C
_{H 2) -Hy3 (n = 12} ) FS-56: Rf9-L0-Hy4 (M = H) FS-57: Rf3-L0-Hy4 (M = H) FS-58: Rf1-L58 (R = C 3 H ₇ , AL = C
_{H 2) -Hy4 (M = K} ) FS-59: Rf4-L59 (R = C 3 H 7, AL = C
_{H 2) -Hy4 (M = Na} )

FS-60: Rf1-L0-Hy5 (M = K) FS-61: Rf10-L60 (AL ¹ = CH ₂ , AL ² = CH ₂ C)
_{H 2) -Hy5 (M = Na} ) FS-62: Rf11-L60 (AL 1 = CH 2, AL 2 = CH 2 C
_{H 2) -Hy5 (M = Na} ) FS-63: Rf5-L60 (AL 1 = CH 2, AL 2 = CH 2 C
_{H 2) -Hy5 (M = Na} ) FS-64: Rf1-L58 (R = C 3 H 7, AL = CH 2 CH 2 C
_{H 2) -Hy5 (M = Na} ) FS-65: Rf1-L51 (R = C 3 H 7) -Hy6 (n
= 5, M = Na) FS -66: Rf1-L51 (R = C 3 H 7) -Hy6 (n
= 10, M = Na) FS -67: Rf1-L51 (R = C 3 H 7) -Hy6 (n
= 15, M = Na) FS -68: Rf1-L51 (R = C 3 H 7) -Hy6 (n
= 20, M = Na) FS -69: Rf1-L58 (R = C 2 H 5, AL = CH 2
_{CH 2) -Hy7 FS-70:} Rf1-L58 (R = H, AL = CH 2 CH 2 CH 2)
-Hy8 (X = I) FS- 71: Rf11-L61 ( below _{Hc, AL = CH 2 CH 2} C
H ₂₎ -Hy6 (M dissociation)

[0061]

Embedded image

FS-72: Rf1-L62 (R = C ₃ H ₇ , AL ¹ = CH ₂ C
^{_{H 2, AL 2 = CH 2}} CH 2 CH 2) -Hy6 (M = Na) FS-73: Rf12-L0-Hy5 (M = Na) FS-74: Rf13-L63 (AR = o- phenylene) -Hy
6 (M = K) FS-75: Rf13-L63 (AR = m-phenylene) -Hy
6 (M = K) FS-76: Rf13-L63 (AR = p-phenylene) -Hy
6 (M = K) FS- 77: Rf6-L64 (R = C 2 H 5, AL = CH 2 CH 2) -
Hy5 (M = H) FS-78: Rf6-L65 (AR = p-phenylene, R = C _{2
H 5) -Hy1 (n = 9} ) FS-79: Rf6-L65 (AR = p- phenylene, R = C _{2
H 5) -Hy1 (n = 14} ) FS-80: Rf6-L65 (AR = p- phenylene, R = C _{2
H 5) -Hy1 (n = 19} ) FS-81: Rf6-L65 (AR = p- phenylene, R = C _{2
H 5) -Hy1 (n = 28} ) FS-82: Rf6-L66 (AR = p- phenylene) -Hy
1 (n = 5) FS-83: Rf6-L66 (AR = p-phenylene) -Hy
1 (n = 10) FS-84: Rf6-L66 (AR = p-phenylene) -Hy
1 (n = 15) FS-85: Rf6-L66 (AR = p-phenylene) -Hy
1 (n = 20)

A fluorine-containing surfactant having two or more fluorine-containing hydrophobic groups or hydrophilic groups may be used. Examples of the fluorinated surfactant having two or more hydrophobic groups or hydrophilic groups are shown below.

[0064]

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FS-86: n1 + n2 = 12, FS-87: n1 + n2
= 18, FS-88: n1 + n2 = 24

[0066]

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FS-89: n1 + n2 = 20, FS-90: n1 + n2
= 18, FS-91: n1 + n2 = 40

[0068]

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FS-92: n = 5, FS-93: n = 10, F
S-94: n = 15, FS-95: n = 20

[0070]

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Two or more fluorine-containing surfactants may be used in combination. For fluorinated surfactants, see various references (eg, Hiroshi Horiguchi, “New Surfactants”, Sankyo Publishing (1975), MJ
Schick, Nonionic Surfactants, Marcell Dekker In
c., New York, (1967), JP-A-7-13293)
There is a description. The amount of the fluorinated surfactant is preferably in the range of 0.01 to 30% by weight, more preferably 0.1 to 10% by weight, more preferably 0.5 to 10% by weight, based on the amount of the discotic liquid crystal molecules. More preferably, the content is from 5 to 5% by weight.

[Vertical Alignment Film for Discotic Liquid Crystalline Molecules] In order to vertically align discotic liquid crystal molecules, it is important to lower the surface energy of the alignment film. Specifically, the surface energy of the alignment film is reduced by the functional group of the polymer, and thereby the discotic liquid crystal molecules are in a standing state. As the functional group that lowers the surface energy of the alignment film, a fluorine atom and a hydrocarbon group having 10 or more carbon atoms are effective. In order to make a fluorine atom or a hydrocarbon group exist on the surface of the alignment film, it is preferable to introduce a fluorine atom or a hydrocarbon group into a side chain rather than a main chain of the polymer. The fluorine-containing polymer preferably contains fluorine atoms at a ratio of 0.05 to 80% by weight, more preferably 0.1 to 70% by weight, and more preferably 0.5 to 65% by weight. More preferably, it is most preferably contained at a ratio of 1 to 60% by weight. The hydrocarbon group is an aliphatic group, an aromatic group, or a combination thereof. The aliphatic group may be cyclic, branched, or linear. The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not show strong hydrophilicity, such as a halogen atom. The number of carbon atoms in the hydrocarbon group is preferably from 10 to 100, more preferably from 10 to 60, and most preferably from 10 to 40. The main chain of the polymer preferably has a polyimide structure or a polyvinyl alcohol structure.

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

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

[0075]

Embedded image

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

[0077] L1: -O-CO- L2: -O -CO- alkylene group -O- L3: -O-CO- alkylene group -CO-NH- L4: -O-CO- alkylene group -NH-SO ₂ -Arylene group-O-L5: -arylene group-NH-CO-L6: -arylene group-CO-O-L7: -arylene group-CO-NH-L8: -arylene group-O-L9: -O-CO -NH-arylene group -NH-CO-

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

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

[0080]

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

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

[0083]

[Example 1] (Preparation of splay alignment liquid crystal cell) A vertical alignment film (RN783, manufactured by Nissan Chemical Co., Ltd.) was provided on a glass substrate provided with an ITO transparent electrode, and a rubbing treatment was performed. Was. 10
Two substrates were stacked via a spacer of μm such that the alignment films faced each other. The orientation of the substrate was adjusted so that the rubbing directions of the alignment films were parallel. A rod-like nematic liquid crystalline molecule having negative dielectric anisotropy (MJ
95785, manufactured by Merck) by a vacuum injection method.
A liquid crystal layer was formed. The tilt angle of the rod-like liquid crystal molecules near the alignment film was 80 °. Δn of the liquid crystalline molecule is 0.081
3, and the value of Δnd of the liquid crystal layer was 813 nm.

(Preparation of Optically Anisotropic Element) Thickness 100 μm
A 0.1 μm-thick gelatin layer was formed on a m-acetylacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.). A solution of the following modified polyvinyl alcohol was applied on the gelatin layer, dried with hot air at 80 ° C., and then subjected to a rubbing treatment to form an alignment film.

[0085]

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A coating solution having the following composition was coated on the alignment film in # 1.
2 was applied using a wire bar coater, attached to a metal frame, and heated in a thermostat at 120 ° C. for 3 minutes to align the discotic liquid crystal compound.

<< Coating Liquid for Optically Anisotropic Layer >> ───────────────────────────────── The following discotic liquid crystal compound 1.9 g Ethylene oxide modified trimethylolpropanetri Acrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 0.2 g Cellulose acetate butyrate having a degree of acetylation of 2.0% and a degree of butyrylation of 52.0% (CAB-551-0.2, Eastman Chemical) 0.04 g Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 0.06 g Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 0.02 g Methyl ethyl ketone 3.43 g ──────────────── ────────────

[0088]

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With the coating layer heated to 120 ° C., 12
Ultraviolet rays were irradiated for 1 minute using a high-pressure mercury lamp of 0 W / cm to polymerize the terminal vinyl groups of the discotic liquid crystalline compound and fix the alignment state. Then, it was left to cool to room temperature. Thus, an optically anisotropic layer was formed, and an optically anisotropic element was produced. The thickness of the optically anisotropic layer is 4.
It was 0 μm. When the retardation of the optically anisotropic element was measured with an ellipsometer (AEP-100, manufactured by Shimadzu Corporation), the average tilt angle of the optical axis was 6
0 °, and the Rth retardation value was 340 nm.

(Preparation of Polarizing Element) A polarizing film was prepared by adsorbing iodine on a stretched polyvinyl alcohol film. Using a polyvinyl alcohol-based adhesive, two 100 μm-thick triacetyl cellulose films (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) were attached to both sides of the polarizing film to produce a polarizing element.

(Preparation of Liquid Crystal Display Device) Two optically anisotropic elements were attached to both sides of the splay alignment liquid crystal cell so that the triacetyl cellulose film faced the cell substrate. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer were arranged in parallel. Two polarizing elements were attached to the outside of the optically anisotropic layer to produce a liquid crystal display. The directions of the polarization axes of the polarizing elements were orthogonal to each other, and the polarization axis and the rubbing direction of the liquid crystal cell were arranged at an angle of 45 °. 1 in the liquid crystal cell of the liquid crystal display
Applying a rectangular wave voltage of kHz, white display 2V, black display 6V
Normally white mode. Using the ratio of the transmittance between the white display and the black display as the contrast ratio, the viewing angle at which a contrast ratio of 10 was obtained in the upper, lower, left, and right directions was measured. The results are shown in Table 1.

Example 2 (Preparation of Optically Anisotropic Element) On a 100 μm-thick triacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.), the following modified polyimide N-methyl- A 2-pyrrolidone solution was applied, dried at 80 ° C. for 5 minutes, and further heated at 180 ° C. for 60 minutes, and then subjected to a rubbing treatment to form an alignment film.

[0093]

Embedded image

A coating solution having the following composition was coated on the alignment film in # 8.
And heated for 10 minutes while blowing air at a speed of 10 m / s and a temperature of 130 ° C. in parallel with the surface of the support and also in the rubbing direction to align the discotic liquid crystal compound. .

<< Coating Liquid for Optically Anisotropic Layer >>デ ィ ス Discotic liquid crystalline compound used in Example 1 91 parts by weight Acetylation degree 0.5% by weight of cellulose acetate butyrate (CAB-551-0.2, manufactured by Eastman Chemical Co.) having a butyrylation degree of 52.0% 2.0% by weight ethylene oxide-modified trimethylolpropane triacrylate (V # 360) 9 parts by weight Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) 3 parts by weight Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1 part by weight 120 parts by weight methyl ethyl ketone ──────────────── ──────────────────

While the coating layer was heated to 130 ° C., it was irradiated with 600 mJ / cm ² ultraviolet rays using a high-pressure mercury lamp.
The terminal vinyl group of the discotic liquid crystalline compound was polymerized to fix the alignment state. Then, it was left to cool to room temperature.
Thus, an optically anisotropic layer was formed, and an optically anisotropic element was produced. Examination of the orientation state of the discotic liquid crystalline molecules in the optically anisotropic layer revealed that the average tilt angle between the disc surface of the discotic liquid crystalline molecules and the plane of the polymer film was 70 °. When the distance between the molecule and the polymer film surface increases,
Alignment (reverse hybrid alignment) was performed so that the tilt angle between the discotic liquid crystal molecules and the plane of the polymer film was small. The measured Δnd of the optically anisotropic element was 400 nm.

(Preparation of Liquid Crystal Display) Two optically anisotropic elements were attached to both sides of the splay alignment liquid crystal cell prepared in Example 1 so that the optically anisotropic layer faced the cell substrate. Was. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer were arranged to be antiparallel. A liquid crystal display device was manufactured by attaching two polarizing elements manufactured in Example 1 to the outside of the optically anisotropic element. The directions of the polarization axes of the polarizing elements were orthogonal to each other, and the polarization axis and the rubbing direction of the liquid crystal cell were arranged at an angle of 45 °. A rectangular wave voltage of 1 kHz is applied to the liquid crystal cell of the liquid crystal display device,
A normally white mode of 2 V for white display and 6 V for black display was set. Using the ratio of the transmittance between the white display and the black display as the contrast ratio, the viewing angle at which a contrast ratio of 10 was obtained in the upper, lower, left, and right directions was measured. The results are shown in Table 1.

Example 3 (Preparation of Optically Anisotropic Element) A polystyrene film having a thickness of 60 μm was used as an optically anisotropic polymer film. The polystyrene film showed optically negative uniaxiality, and the optical axis was parallel to the film plane. Also,
The Re retardation of the film was 200 nm. As in Example 2, an alignment film was formed on a polystyrene film. The rubbing direction of the alignment film is parallel to the direction of the optical axis of the polystyrene film. A coating solution of the composition used in Example 2 was applied on the alignment film using a # 4 bar coater, and a wind at a speed of 10 m / s and a temperature of 130 ° C. was parallel to the surface of the support and parallel to the rubbing direction. And heated for 10 minutes to align the discotic liquid crystalline compound. While the coating layer was heated to 130 ° C., ultraviolet rays of 600 mJ / cm ² were irradiated using a high-pressure mercury lamp to polymerize the terminal vinyl groups of the discotic liquid crystal compound and fix the alignment state. Then, it was left to cool to room temperature. Thus, an optically anisotropic layer was formed, and an optically anisotropic element was produced. Examination of the orientation state of the discotic liquid crystalline molecules in the optically anisotropic layer revealed that the average tilt angle between the discotic liquid crystalline molecules and the plane of the polymer film was 50 °, and that the discotic liquid crystalline When the distance between the molecule and the surface of the polymer film is increased, the orientation (reverse hybrid alignment) is such that the inclination angle between the disc surface of the discotic liquid crystalline molecule and the plane of the polymer film becomes smaller. When the Δnd of the optically anisotropic element was measured, it was 200 nm.

(Preparation of Liquid Crystal Display) Two optically anisotropic elements were attached to both sides of the splayed liquid crystal cell prepared in Example 1 so that the optically anisotropic layer faced the cell substrate. Was. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer were arranged to be antiparallel. A liquid crystal display device was manufactured by attaching two polarizing elements manufactured in Example 1 to the outside of the optically anisotropic element. The directions of the polarization axes of the polarizing elements were orthogonal to each other, and the polarization axis and the rubbing direction of the liquid crystal cell were arranged at an angle of 45 °. A rectangular wave voltage of 1 kHz is applied to the liquid crystal cell of the liquid crystal display device,
A normally white mode of 2 V for white display and 6 V for black display was set. Using the ratio of the transmittance between the white display and the black display as the contrast ratio, the viewing angle at which a contrast ratio of 10 was obtained in the upper, lower, left, and right directions was measured. The results are shown in Table 1.

Example 4 (Preparation of Optically Anisotropic Element) An optically anisotropic element was prepared by uniaxially stretching a polycarbonate film having a thickness of 60 μm and then stretching it in the thickness direction of the film. The Re retardation of the optically anisotropic element was 100 nm.
The Nz factor defined by the following equation was 0.5. Nz = (nx−nz) / (nx−ny) where nx and ny are in-plane principal refractive indices (nx
>Ny); nz is the refractive index in the thickness direction; and
d is the thickness.

(Preparation of Liquid Crystal Display Device) On both sides of the splay alignment liquid crystal cell prepared in Example 1, two optically anisotropic elements prepared in Example 3 and an optically anisotropic layer were formed on a cell substrate. Pasted to face each other. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer were arranged to be antiparallel. One sheet of the optically anisotropic element manufactured as described above was attached to one outer side of the optically anisotropic element manufactured in Example 3. The arrangement was such that the angle between the rubbing direction of the liquid crystal cell and the nx direction of the optically anisotropic element was 45 °. A liquid crystal display device was manufactured by attaching two polarizing elements manufactured in Example 1 to the outside of the optically anisotropic element.
The directions of the polarization axes of the polarizing elements were orthogonal to each other, and the polarization axis and the rubbing direction of the liquid crystal cell were arranged at an angle of 45 °. A 1 kHz rectangular wave voltage was applied to the liquid crystal cell of the liquid crystal display device to set a normally white mode of 2 V for white display and 6 V for black display. Using the ratio of the transmittance between the white display and the black display as the contrast ratio, the viewing angle at which a contrast ratio of 10 was obtained in the upper, lower, left, and right directions was measured. The results are shown in Table 1.

Example 5 (Preparation of Optically Anisotropic Element) A 100 μm thick polystyrene film was used as an optically anisotropic polymer film. The polystyrene film showed optically negative uniaxiality, and the optical axis was parallel to the film plane. The Re retardation of the film measured with light having a wavelength of 550 nm was 200 nm. As in Example 2, an alignment film was formed on a polystyrene film. The rubbing direction of the alignment film is parallel to the direction of the optical axis of the polystyrene film. A coating solution having the composition used in Example 2 was applied on the alignment film using a # 3 bar coater, and air at a speed of 10 m / s and a temperature of 130 ° C. was parallel to the surface of the support,
Heating was carried out for 10 minutes while applying in parallel with the rubbing direction to align the discotic liquid crystal compound. While the coating layer was heated to 130 ° C., ultraviolet rays of 600 mJ / cm ² were irradiated using a high-pressure mercury lamp to polymerize the terminal vinyl groups of the discotic liquid crystal compound and fix the alignment state. Then, it was left to cool to room temperature. Thus, an optically anisotropic layer was formed, and an optically anisotropic element was produced. Examination of the orientation state of the discotic liquid crystalline molecules in the optically anisotropic layer revealed that the average tilt angle between the discotic liquid crystalline molecules and the plane of the polymer film was 50 °, and that the discotic liquid crystalline When the distance between the molecule and the surface of the polymer film increases, the orientation of the discotic liquid crystalline molecules is adjusted so that the tilt angle between the disc surface and the plane of the polymer film decreases (reverse hybrid alignment).
Was. When the Δnd of the optically anisotropic element was measured, it was 160 nm.

(Preparation of Elliptically Polarizing Plate) Iodine was adsorbed to a stretched polyvinyl alcohol film to prepare a polarizing film. The optically anisotropic element was bonded to one side of the polarizing film using a polyvinyl alcohol-based adhesive so that the optically anisotropic layer was on the outside. The angle between the polarization axis of the polarizing film and the rubbing direction of the optically anisotropic element is 4
It was arranged to be 5 mm. An elliptically polarizing plate was prepared by laminating a 100 μm thick triacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) to the other side of the polarizing film.

(Preparation of Liquid Crystal Display) On the both sides of the splay alignment liquid crystal cell prepared in Example 1, the above-mentioned elliptically polarizing plate was formed using an acrylic adhesive, and the optically anisotropic layer was opposed to the liquid crystal cell. To form a liquid crystal display device. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer were arranged to be antiparallel. A 1 kHz rectangular wave voltage was applied to the liquid crystal cell of the liquid crystal display device to set a normally white mode of 2 V for white display and 6 V for black display. Using the ratio of the transmittance between the white display and the black display as the contrast ratio, the viewing angle at which a contrast ratio of 10 was obtained in the upper, lower, left, and right directions was measured. The results are shown in Table 1.

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[Table 1] Table 1 視野 Sample viewing angle number Upper lower Left Right ──────────────────────────────────── Example 1 70 ゜ 71 ゜ 76 ゜ 76 ゜ Example 2 72 ゜ 73 ゜ 76 ゜ 76 ゜ Example 3 75 ゜ 76 ゜ 80 ゜ 80 ゜ Example 4 81 ゜ 82 ゜ 80 ゜ 80 ゜ Example 5 70 ゜ 70 ゜ 75 ゜ 75 ゜────────────────────────────

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing the orientation of a liquid crystalline compound in a splay alignment liquid crystal cell.

FIG. 2 is a schematic diagram of a liquid crystal display device using a splay alignment liquid crystal cell.

FIG. 3 is a conceptual diagram showing optical compensation of a splay alignment liquid crystal cell by an optically anisotropic element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal layer 1a-1h Rod-like liquid crystalline molecule 2a Lower alignment film 2b Upper alignment film 3a Lower transparent electrode 3b Upper transparent electrode 4a Lower substrate 4b Upper substrate 10 Splay alignment liquid crystal cell 11a Lower polarizing element 11b Upper polarizing element 12a, 12b Anisotropic element 13 Polymer film BL Backlight PAa Direction of polarization axis of lower polarizing element PAb Direction of polarization axis of upper polarizing element RDa, RDb Rubbing direction of alignment film of liquid crystal cell RDc, RDd Rubbing of optically anisotropic element Direction XX Middle of two alignment films (symmetric plane)

Claims (3)

[Claims] 1. A lower polarizing element, a lower substrate, a lower transparent electrode, a lower alignment film, an upper alignment film, an upper transparent electrode, an upper substrate, and an upper polarizing element are arranged in this order, and a rod-like nematic liquid crystal is disposed in a gap between the two alignment films. Liquid crystal display device in which conductive molecules are encapsulated, wherein the rod-shaped nematic liquid crystal molecules have negative dielectric anisotropy, the rubbing directions of the two alignment films are substantially parallel, and the rod-shaped nematic liquid crystal is Molecules are symmetrically oriented with the middle of the two alignment films as the symmetry plane, and the tilt angle in the major axis direction of the rod-like nematic liquid crystalline molecule is the largest in the vicinity of the two alignment films and the middle between the two alignment films. Is continuously changed to be the minimum, the directions of the polarization axes of the two polarizing elements are substantially orthogonal,
The angle between the direction of each polarization axis and the rubbing direction of the alignment film is substantially 45 °. 2. An optically anisotropic element having negative birefringence is disposed between the lower polarizing element and the lower substrate or between the upper substrate and the upper polarizing element. Liquid crystal display. 3. The liquid crystal display device according to claim 2, wherein the optically anisotropic element is a layer formed from discotic liquid crystalline molecules.