JP2004302446A - Retardation plate and compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation plate (optical compensation sheet) using a liquid crystal compound excellent in both wavelength dispersion property and refractive index anisotropy. <P>SOLUTION: The retardation plate includes an optical anisotropic layer formed from a compound represented by the formula (I): [(R<SP>1</SP>)a-M-(L<SP>1</SP>)]b-(L<SP>2</SP>), wherein R<SP>1</SP>represents alkyl in which -CH<SB>2</SB>- can be substituted by -O-, -S-, -C(=O)-, -N(R<SP>2</SP>)-, -CH=CH- or -C≡C-; R<SP>2</SP>represents H or alkyl; M represents a group consisting of three or more aromatic rings; L<SP>1</SP>represents a single bond or divalent alkylene in which -CH<SB>2</SB>- can be substituted by -O-, -S-, -C(=O)- or -N(R<SP>2</SP>)-; L<SP>2</SP>represents a b-valent cyclic group or a b-valent group of alkene or alkyne; (a) represents the number of the symbols R<SP>1</SP>substituted on M; and b represents an integer of 2-6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a retardation plate using a novel liquid crystal.

The STN type liquid crystal display device includes an STN type liquid crystal cell, two polarizing plates, and one or two optical compensation sheets (retardation plates) provided between the STN type liquid crystal cell and the polarizing plate.
The liquid crystal cell is composed of a rod-like liquid crystal molecule, two substrates for enclosing it, and an electrode layer for applying a voltage to the rod-like liquid crystal molecule. In the STN type liquid crystal cell, an alignment film for aligning rod-like liquid crystalline molecules is provided on two substrates. Further, the rod-like liquid crystalline molecules are twisted and aligned at 180 to 360 degrees using a chiral agent. The STN type liquid crystal display device is characterized in that a large-capacity clear display is possible by time-division driving even with a simple matrix electrode structure without active elements (thin film transistors and diodes).

  In an STN liquid crystal display device without a retardation plate, the display image is colored blue or yellow due to the birefringence of rod-like liquid crystal molecules. The coloring of the display image is inconvenient for both monochrome display and color display. The retardation plate is used for eliminating such coloring and obtaining a bright and clear image. The retardation plate may also be given a function of expanding the viewing angle of the liquid crystal cell. As a retardation plate, a stretched birefringent film has been conventionally used. Patent Document 1 and Patent Document 2 describe a retardation plate for an STN type liquid crystal display device using a stretched birefringent film.

Patent Document 3 discloses a discotic liquid crystal having a large refractive index anisotropy, but the wavelength dispersion characteristic is deteriorated and the performance improvement is insufficient. In general, the wavelength dispersion characteristic and the refractive index anisotropy are in a trade-off relationship. When the refractive index anisotropy is increased, the wavelength dispersion characteristic is deteriorated. The development of technology to break away from this trade-off has been desired.
Further, Non-Patent Document 1, Non-Patent Document 2 and Non-Patent Document 3 disclose a bis-type discotic liquid crystal, but have not disclosed optical performance at all. In addition, these liquid crystals are not suitable for practical use as an optical member because they have a long conjugated system and are colored yellow or contain mercury. Further, Patent Document 4 discloses a general formula of a compound obtained by converting triphenylene into a bis-type, and these all have many aromatic rings (mainly benzene rings) in the side chain of the triphenylene ring. The molecule has a very large molecular weight. For this reason, there are problems such as high viscosity and slow orientation, and low refractive index anisotropy due to a large molecular weight.

JP-A-7-104284 JP-A-7-13021 JP 2001-166147 A JP-A-8-327822 Molecular Crystals and Liquid Crystals, 357, 55 (2001) Organic Letters, 4, 157 (2002) Liquid Crystals, 29, 899 (2002)

  An object of the present invention is to provide a liquid crystal material excellent in both wavelength dispersion characteristics and refractive index anisotropy, and a retardation plate (optical compensation sheet) using the compound.

The above object is achieved by a retardation plate and a liquid crystal compound having the following constitution.
1. A retardation plate having an optically anisotropic layer formed from a compound represented by the following general formula (I) on a support.
Formula (I)
^{[(R 1) a-M-} (L 1)] b- (L 2)
In the above general formula (I):
R ¹ represents an alkyl group having 1 to 20 carbon atoms. The —CH ₂ — group in the alkyl group is substituted with —O—, —S—, —C (═O) —, —N (R ² ) —, —CH═CH—, —C≡C—. However, -O- and -O- are not directly bonded.
R ² represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.
M represents a group consisting of three or more aromatic rings.
L ¹ represents a single bond or a divalent alkylene group having 1 to 10 carbon atoms. The —CH ₂ — group in the alkylene group may be substituted with —O—, —S—, —C (═O) —, —N (R ² ) —, but —O— and —O— -And are not directly bonded.
L ² represents a cyclic, alkene or alkyne b-valent group.
a represents the number of R ¹ substituting for M. b represents an integer of 2 to 6.
2. 2. The retardation plate as described in 1 above, wherein in the compound represented by the general formula (I), a plurality of Ms are not conjugated by multiple bonds.
3. 3. The retardation plate as described in 1 or 2 above, wherein M in the general formula (I) is a group having a triphenylene ring.
4). 4. The retardation plate as described in any one of 1 to 3 above, wherein the compound represented by formula (I) exhibits liquid crystallinity.
5). 5. The retardation plate as described in any one of 1 to 4 above, wherein the compound represented by formula (I) is a liquid crystalline compound having a polymerizable group.
6). 2. The retardation plate as described in 1 above, wherein the compound represented by the general formula (I) is a compound represented by the general formula (II).
Formula (II)

In general formula (II):
R ¹ and L ¹ have the same meaning as those in formula (I).
L ⁴ represents a cyclic, alkene or alkyne divalent group.
e represents the number substituted on the triphenylene ring.
Note that the two triphenylene rings bonded through L ¹ and L ⁴ are not conjugated.
7). Compound represented by the above general formula (II).
8). 8. The compound according to 7 above, wherein the compound represented by the general formula (II) is a liquid crystalline compound having a polymerizable group.

  The retardation plate (optical compensation sheet) of the present invention uses a discotic liquid crystalline compound having excellent wavelength dispersion characteristics and refractive index anisotropy for the optically anisotropic layer, so that it has a wide viewing angle and color. There is little change in taste.

  The retardation plate of the present invention has an optically anisotropic layer formed from a compound represented by the general formula (I) on a support.

  In the present invention, the term “formed from” means that the optically anisotropic layer contains a compound represented by the general formula (I) and a polymer of the compound represented by the general formula (I). It means at least one when it contains. For example, when the compound of the present invention has a polymerizable group (preferably when the compound of the present invention has a polymerizable group at the terminal), the optically anisotropic layer is a polymer of the compound represented by the general formula (I) Such an embodiment is also included in the present invention.

First, the liquid crystal compound represented by the general formula (I) of the present invention will be described.
R ¹ represents an alkyl group having 1 to 20 carbon atoms, in which —CH ₂ — groups are —O—, —S—, —C (═O) —, —N (R ² ) —, —CH. ═CH—, —C≡C— may be substituted. However, -O- and -O- are not directly bonded. R ² represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms (preferably a methyl group).
R ¹ may have a substituent, and the substituent is preferably a polymerizable group. As the polymerizable group, a polymerizable ethylenically unsaturated group or a ring-opening polymerizable group is preferable. Examples of the polymerizable ethylenically unsaturated group include the following (M-1) to (M-5).

In the formula, R represents a hydrogen atom or a substituent, preferably a hydrogen atom or an alkyl group, particularly preferably a hydrogen atom or a methyl group.
Among (M-1) to (M-5), (M-1) and (M-2) are preferable, and (M-1) is particularly preferable.
The ring-opening polymerizable group is preferably a cyclic ether group, more preferably an epoxy group or an oxetane group, and particularly preferably an epoxy group.
M represents a group composed of three or more aromatic rings, and more specifically is a group represented below.
M ¹ -[(L ³ )-(M ² )] a ¹
Here, M ¹ and M ² each independently represent a group having an aromatic ring, and specific examples thereof include the following groups.

L ³ represents a single bond or a C 1-10 divalent alkylene group, and the —CH ₂ — group in the alkylene group is —O—, —S—, —C (═O) —, — Although it may be substituted with NH-, -O- and -O- are not directly bonded.
a ¹ represents an integer of 0 to 3, preferably 0, 1, 2 and particularly preferably 0 or 1.
L ^{1 in the} general formula (I) has the same meaning as L ³ .
L ^{2 in the} general formula (I) represents a cyclic or alkene or alkyne polyvalent group. Specific examples include the followings in addition to the specific examples of M ¹ and M ² , and function as a divalent to hexavalent group by bonding at an arbitrary position.

^{Also, - (L 1) b- (} L 2) - (L 1) b- plurality of M mutually bonded through a group is not conjugated to each other.

  The compound represented by the general formula (I) of the present invention may have a substituent, and examples of the substituent include an alkyl group (for example, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group), and an alkenyl group. (For example, vinyl group, allyl group, 2-butenyl group, 3-pentenyl group and the like), alkynyl group (for example, propargyl group, 3-pentynyl group and the like), substituted or unsubstituted amino group ( For example, an unsubstituted amino group, a methylamino group, a dimethylamino group, a diethylamino group, and the like), an alkoxy group (for example, a methoxy group, an ethoxy group, a butoxy group, and the like), an acyl group (for example, an acetyl group, Formyl group, pivaloyl group, etc.), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbo group) An acyloxy group (for example, an acetoxy group), an acylamino group (for example, an acetylamino group), an alkoxycarbonylamino group (for example, a methoxycarbonylamino group) Sulfonylamino group (for example, methanesulfonylamino group), sulfamoyl group (for example, sulfamoyl group, methylsulfamoyl group, dimethylsulfamoyl group, etc.), carbamoyl group (for example, unsubstituted) Carbamoyl group, methylcarbamoyl group, diethylcarbamoyl group and the like), alkylthio group (for example, methylthio group, ethylthio group and the like), sulfonyl group (for example, mesyl group and the like), sulfinyl group (for example, Me Ureido group (eg, unsubstituted ureido group, methylureido group, etc.), phosphoric acid amide group (eg, diethylphosphoric acid amide group), hydroxy group, Mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, imino group, heterocyclic group (for example, aliphatic heterocyclic ring having a hetero atom such as nitrogen atom, oxygen atom, sulfur atom) Group such as piperidyl group and morpholino group) and silyl group (such as trimethylsilyl group). These substituents may be further substituted with these substituents. Further, when two or more substituents are present, they may be the same or different. If possible, they may be bonded to each other to form a ring.

Among the compounds represented by the general formula (I) of the present invention, a compound represented by the following general formula (II) is preferable.
Formula (II)

In general formula (II):
R ¹ and L ¹ have the same meanings as those in formula (I).
L ⁴ represents a cyclic, alkene, or alkyne divalent group.
e represents the number substituted on the triphenylene ring.
Here, the two triphenylene rings bonded through L ¹ and L ⁴ are not conjugated.

A plurality of R ¹ , M, and L ¹ present in the general formula (I) or the general formula (II) may be the same or different, but may be the same from the viewpoint of ease of synthesis. preferable.

As described above, the compound represented by the general formula (I) or the general formula (II) of the present invention does not have an aromatic ring other than the portion represented by M and L ² or L ⁴ in the formula. By applying such a design, the molecular weight is reduced, the orientation speed is improved, and the refractive index anisotropy is increased. Such a design makes it difficult to develop liquid crystallinity (especially ND phase) particularly in the case of discotic liquid crystals, but we have made it possible to achieve liquid crystallinity by incorporating the design of bis-type. We succeeded in paralleling the issues of speed and refractive index anisotropy.

  Specific examples of the compound of the present invention are shown below, but the present invention is not limited thereto.

These liquid crystal compounds represented by the general formula (I) have a discotic molecular structure and are discotic liquid crystal compounds. As described in JP-A-11-92420 discloses such, inter alia, when aligned, preferably on a compound expressed N _D phase (discotic nematic phase) is used as an optical element.

The compounds of the present invention include, for example, Liquid Crystals, 29, 899 (2002), Organic Letters, 4, 157 (2002), Molecular Crystals and Liquid Crystals, 357, 55 (2001), It can be synthesized with reference to the method described in the above. Although the typical synthesis example of the compound of this invention is shown below, this invention is not limited to these.
(Synthesis Example 1) Synthesis of Exemplified Compound (1)

(1-a) (7.41 mmol) and (1-b) (3.37 mmol) were mixed in methylene chloride (100 ml), and the reaction solution was cooled to 10 ° C. or lower. Triethylamine (11.3 mmol) was added dropwise thereto. Further, 50 mg of (1-c) was added, followed by reaction at room temperature for 12 hours. The reaction was stopped with 1M hydrochloric acid, the reaction solution was washed twice with 1M hydrochloric acid, and the organic layer was concentrated. The resulting residue was recrystallized from ethyl acetate to obtain Exemplified Compound (1) in 59% yield. The phase transition temperature was as follows.
Cry 186 ° C ND 230 ° C Iso

  (Synthesis Example 2) Synthesis of Exemplified Compound (7)

(7-a) (1.05 mmol) and (7-b) (0.477 mmol) were mixed in methylene chloride (20 ml) and cooled to 10 ° C. or lower. (7-c) (10 mg) and triethylamine (1.6 mmol) were added there. Thereafter, the reaction solution was brought to room temperature and reacted for 10 hours. The reaction was stopped with 1M hydrochloric acid, and the reaction solution was washed with 1M hydrochloric acid. After the organic layer was concentrated, the residue was purified by silica gel column chromatography (eluent: methylene chloride / hexane = 1/1) to obtain Exemplified Compound (7) in a yield of 74%. The phase transition temperature was as follows.
Cry 230 ° C ND 250 ° C Iso

(Synthesis example 3) The synthesis | combination of exemplary compound (3) It synthesize | combined by the method similar to exemplary compound (1). When the phase transition behavior of this product was measured using a polarizing microscope, it showed a columnar phase from 147 ° C. when the temperature was lowered.

(Synthesis Example 4) Synthesis of Exemplified Compound (6)
The compound was synthesized in the same manner as for the exemplary compound (7). When the phase transition behavior of this product was measured using a polarizing microscope, it showed an ND phase from 164 ° C. when the temperature was lowered.

(Synthesis example 5) The synthesis | combination of exemplary compound (11) It synthesize | combined by the method similar to exemplary compound (1). It was as follows when the phase transition behavior of this thing was measured using the polarization microscope.
Cry 138 ° C ND 192 ° C Iso

Synthesis Example 6 Synthesis of Exemplary Compound (15)
The compound was synthesized in the same manner as for the exemplary compound (7). It was as follows when the phase transition behavior of this thing was measured using the polarization microscope.
About 50 ° C ND 152 ° C Iso

(Synthesis Example 7) Synthesis of Exemplified Compound (16)
The compound was synthesized in the same manner as for the exemplary compound (7). When the phase transition behavior of this product was measured using a polarizing microscope, it showed an ND phase from 94 ° C. when the temperature was lowered.

[Method for producing optically anisotropic layer]
The liquid crystal compound of the present invention is once heated to the liquid crystal phase formation temperature and then cooled while maintaining the alignment state, thereby fixing the alignment state in the liquid crystal state without impairing (agreeing to “fix”) Can do. The liquid crystal compound of the present invention can also be fixed by heating the composition to which the polymerization initiator has been added to the liquid crystal phase formation temperature, followed by polymerization and cooling.
When the alignment state is finally fixed, the liquid crystal compound of the present invention no longer needs to exhibit liquid crystallinity. For example, when a polymerizable compound is used as the liquid crystal compound, as a result, the polymerization or crosslinking reaction proceeds by reaction with heat, light, etc., and the liquid crystallinity may be lost by increasing the molecular weight.

[Phase difference plate]
The retardation plate of the present invention forms an optically anisotropic layer containing a liquid crystal compound represented by the general formula (I) with its alignment state fixed on an alignment film provided on a transparent support. Can be produced.
Here, the optically anisotropic layer is prepared by adding other additives as necessary to the liquid crystal compound of the present invention to prepare a liquid crystal composition as a coating liquid, and applying the composition onto the alignment film, Thus, it can be obtained by fixing the liquid crystal in the alignment state.
The thickness of the optically anisotropic layer formed from the liquid crystal compound is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and most preferably 0.5 to 10 μm. .

[Additive for optically anisotropic layer]
Examples of additives that can be added to the liquid crystal compound in forming the optically anisotropic layer include an air interface alignment controller, a repellency inhibitor, a polymerization initiator, and a polymerizable monomer.

(Air interface orientation control agent)
The liquid crystal compound is aligned at the air interface at the pretilt angle of the air interface. There are three types of pretilt angles: a pretilt angle formed by the nx refractive index direction and the air interface, a pretilt angle formed by the ny refractive index direction and the air interface, and a pretilt angle formed by the nz refractive index direction and the air interface. Since the degree of this pretilt angle varies depending on the type of compound, it is necessary to arbitrarily control the pretilt angle at the air interface according to the purpose.
For controlling the pretilt angle, for example, an external field such as an electric field or a magnetic field or an additive can be used, but an additive is preferably used.
Examples of such an additive include a substituted or unsubstituted aliphatic group having 6 to 40 carbon atoms or a substituted or unsubstituted aliphatic substituted oligosiloxanoxy group having 6 to 40 carbon atoms in the molecule. A compound having two or more is preferable, and a compound having two or more in the molecule is more preferable. For example, a hydrophobic excluded volume effect compound described in JP-A No. 2002-20363 can be used as the air interface alignment control agent.

  The addition amount of the alignment control additive on the air interface side is preferably 0.001% by mass to 20% by mass, more preferably 0.01% by mass to 10% by mass, and 0.1% by mass with respect to the liquid crystal compound. % To 5% by mass is most preferred.

(Anti-repellent agent)
As a material for adding to the liquid crystal compound and preventing repelling at the time of application of the liquid crystal composition, generally a polymer compound can be suitably used.
The polymer to be used is not particularly limited as long as the tilt angle change and orientation of the liquid crystal compound are not significantly inhibited.
Examples of the polymer are described in JP-A-8-95030, and particularly preferred specific polymer examples include cellulose esters. Examples of cellulose esters include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose, and cellulose acetate butyrate. In order not to disturb the alignment of the liquid crystal compound, the amount of the polymer used for the purpose of preventing repellency is generally in the range of 0.1 to 10% by mass with respect to the liquid crystal compound, and in the range of 0.1 to 8% by mass. It is more preferable that it is in the range of 0.1 to 5% by mass.

(Polymerization initiator)
In the present invention, the liquid crystal compound is preferably fixed in a monodomain alignment, that is, in a substantially uniform alignment state. Therefore, when a polymerizable liquid crystal compound is used, the liquid crystal compound is obtained by a polymerization reaction. Is preferably fixed.
The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator, a photopolymerization reaction using a photopolymerization initiator, and a polymerization reaction by electron beam irradiation. In order to prevent the support and the like from being deformed or altered by heat. Also, a photopolymerization reaction and a polymerization reaction by electron beam irradiation are preferable.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Description), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850), oxadiazole compounds (U.S. Pat. No. 4,212,970), and the like. The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystal compound is preferably performed using ultraviolet rays. The irradiation energy is preferably 10mJ~50J / cm ^2, further preferably 50mJ~800mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. Further, since the oxygen concentration in the atmosphere is related to the degree of polymerization, when the desired degree of polymerization is not reached in the air, it is preferable to reduce the oxygen concentration by a method such as nitrogen substitution. A preferable oxygen concentration is preferably 10% or less, more preferably 7% or less, and most preferably 3% or less.

(Polymerizable monomer)
A polymerizable monomer may be added to the liquid crystal composition.
The polymerizable monomer used together with the liquid crystal compound is not particularly limited as long as it has compatibility with the liquid crystal compound and does not significantly change the tilt angle or inhibit the alignment of the liquid crystal compound. Among these, compounds having a polymerization active ethylenically unsaturated group such as a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group are preferably used. The addition amount of the polymerizable monomer is generally in the range of 0.5 to 50% by mass and preferably in the range of 1 to 30% by mass with respect to the liquid crystal compound. In addition, it is particularly preferable to use a monomer having two or more reactive functional groups because an effect of improving the adhesion between the alignment film and the optically anisotropic layer can be expected.

(Coating solvent)
As the solvent used for preparing the liquid crystal composition, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, toluene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides, esters and ketones are preferred. Two or more organic solvents may be used in combination.

[Application method]
The optically anisotropic layer is formed by preparing a liquid crystal composition coating solution using the above solvent, coating the alignment liquid on the alignment film, and aligning the liquid crystal compound. The coating liquid can be applied by a known method (for example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, or a die coating method).

[Alignment film]
The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.
As long as a desired orientation can be imparted to the liquid crystal compound of the optically anisotropic layer provided on the orientation film, the orientation film may be any layer, but in the present invention, it is formed by rubbing treatment or light irradiation. An alignment film is preferred. In particular, an alignment film formed by a rubbing treatment of a polymer is particularly preferable. The rubbing treatment can be generally carried out by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. In the present invention, in particular, by the method described in the liquid crystal manual (Maruzen Co., Ltd.). Preferably it is done. The thickness of the alignment film is preferably 0.01 to 10 μm, and more preferably 0.05 to 3 μm.

[Rubbing density of alignment film]
Since there is a relationship between the rubbing density of the alignment film and the pretilt angle of the liquid crystal compound at the interface of the alignment film, the pretilt angle decreases as the rubbing density increases, and the pretilt angle increases as the rubbing density decreases. By changing the rubbing density, the pretilt angle can be adjusted.
As a method for changing the rubbing density of the alignment film, a method described in “Liquid Crystal Handbook” edited by the Liquid Crystal Handbook Editorial Committee (Maruzen Co., Ltd., 2000) can be used. The rubbing density (L) is quantified by the formula (A).
Formula (A): L = Nl (1 + 2πrn / 60v)
In the above formula (A), N is the number of rubbing, I is the contact length of the rubbing roller, r is the radius of the roller, n is the number of rotations of the roller (rpm), and v is the stage moving speed (second speed).
In order to increase the rubbing density, the rubbing frequency should be increased, the contact length of the rubbing roller should be increased, the radius of the roller should be increased, the rotation speed of the roller should be increased, and the stage moving speed should be decreased, while the rubbing density should be decreased. To do this, you can reverse this.

[Transparent support]
The transparent support of the retardation plate of the present invention is not particularly limited as long as it is mainly optically isotropic and has a light transmittance of 80% or more, but a polymer film is preferred.
Specific examples of the polymer include cellulose esters (eg, cellulose diacetate, cellulose triacetate), norbornene polymers, poly (meth) acrylate esters, and the like, and many commercially available polymers are preferably used. Is possible. Among these, cellulose esters are preferable from the viewpoint of optical performance, and lower fatty acid esters of cellulose are more preferable. Here, the lower fatty acid refers to a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). As the lower fatty acid ester of cellulose, cellulose triacetate is particularly preferable. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. In addition, even a conventionally known polymer such as polycarbonate or polysulfone, which easily develops birefringence, has a reduced birefringence by modifying the molecule described in WO00 / 26705. It can also be used.

(Cellulose ester)
Hereinafter, the cellulose ester (especially cellulose setate) preferably used as the transparent support will be described in detail.
As the cellulose ester, it is preferable to use cellulose acetate having an acetylation degree of 55.0 to 62.5%. In particular, the acetylation degree is preferably 57.0 to 62.0%. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more. The cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7, more preferably 1.3 to 1.65, and most preferably 1.4 to 1.6. preferable.
In the cellulose ester obtained by a general method, the hydroxyl groups at the 2nd, 3rd and 6th positions of cellulose are not evenly distributed by 1/3 of the total substitution degree. There is a tendency to become smaller. In the present invention, it is preferable that the substitution degree of the 6-position hydroxyl group of cellulose is larger than the 2-position and 3-position. The hydroxyl group at the 6-position with respect to the total substitution degree is preferably 30% or more and 40% or less and is preferably substituted with an acyl group, more preferably 31% or more, and particularly preferably 32% or more. The substitution degree at the 6-position is preferably 0.88 or more. The 6-position hydroxyl group may be substituted with an acyl group having 3 or more carbon atoms (eg, propionyl, butyryl, valeroyl, benzoyl, acryloyl) in addition to the acetyl group. The degree of substitution at each position can be determined by NMR. Cellulose esters having a high degree of substitution at the 6-position hydroxyl group are described in Synthesis Example 1 described in paragraph Nos. 0043 to 0044 of JP-A No. 11-5851, Synthesis Example 2 described in paragraph Nos. 0048 to 0049, and paragraph numbers 0051 to 0052. It can be synthesized with reference to the method of Synthesis Example 3 described.

(Retardation increasing agent)
In order to adjust the retardation of a polymer film used as a transparent support, particularly a cellulose acetate film, an aromatic compound having at least two aromatic rings can be used as a retardation increasing agent. When using such a retardation increasing agent, a retardation increasing agent is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acetate. The retardation increasing agent is preferably used in a range of 0.05 to 15 parts by mass, and more preferably in a range of 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acetate. Two or more aromatic compounds may be used in combination.
The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable, More preferred are a benzene ring and a 1,3,5-triazine ring. It is particularly preferred that the aromatic compound has at least one 1,3,5-triazine ring.

The number of aromatic rings that the aromatic compound has is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. .
The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c). Such retardation increasing agents are described in WO01 / 88574A1, WO00 / 2619A1, JP-A Nos. 2000-1111914, 2000-275434, and Japanese Patent Application No. 2002-70009.

(Deposition of cellulose acetate film)
The cellulose acetate film is preferably produced by a solvent cast method from the prepared cellulose acetate solution (dope). The above-mentioned retardation increasing agent may be added to the dope.
The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. For casting and drying methods in the solvent casting method, U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.
The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

It is also possible to form a film by casting two or more layers of dope using the prepared cellulose acetate solution (dope). The dope is cast on a drum or band and the solvent is evaporated to form a film. The dope before casting is preferably adjusted in concentration so that the solid content is 10 to 40%. The surface of the drum or band is preferably finished in a mirror state.
When casting a plurality of cellulose acetate solutions, a solution is prepared by casting a solution containing cellulose acetate from a plurality of casting openings provided at intervals in the traveling direction of the support, and laminating them. May be. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. Alternatively, the cellulose acetate solution may be cast from two casting ports to form a film. For example, each of JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-134933. The method described in the publication can be used. Further, a cellulose acetate film casting method in which a flow of a high-viscosity cellulose acetate solution is wrapped with a low-viscosity cellulose acetate solution and the high-viscosity and low-viscosity cellulose acetate solutions are simultaneously extruded as described in JP-A-56-162617. A method may be used.

  The retardation of the cellulose acetate film can be further adjusted by stretching treatment. The draw ratio is preferably in the range of 0 to 100%. When stretching the cellulose acetate film of the present invention, tenter stretching is preferably used, and in order to control the slow axis with high accuracy, the difference between the left and right tenter clip speeds, the separation timing, etc. can be made as small as possible. preferable.

(Additive)
A plasticizer can be added to the cellulose ester film in order to improve mechanical properties or increase the drying rate. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalates include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and di-2-ethylhexyl phthalate (DEHP). . Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by mass of the amount of cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

Degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added to the cellulose ester film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by mass, bleed-out (bleeding) of the deterioration preventing agent to the film surface may be observed.
As a particularly preferred example of the deterioration preventing agent, butylated hydroxytoluene (BHT) can be mentioned. The ultraviolet ray preventing agent is described in JP-A-7-11056.

(Surface treatment, other physical properties)
The cellulose acetate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. In addition, as described in JP-A-7-333433, it is preferable to provide an undercoat layer.
From the viewpoint of maintaining the flatness of the film, the temperature of the cellulose acetate film in these treatments is preferably Tg (glass transition temperature) or less, specifically 150 ° C. or less.

As for the surface treatment of the cellulose acetate film, it is particularly preferable to carry out an acid treatment or an alkali treatment, that is, a saponification treatment for cellulose acetate, from the viewpoint of adhesion to an alignment film or the like.
Hereinafter, the alkali saponification treatment will be specifically described as an example.
The alkali saponification treatment is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried.
Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution. The specified concentration of hydroxide ions is preferably in the range of 0.1 to 3.0N, and more preferably in the range of 0.5 to 2.0N. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.

The surface energy of the cellulose acetate film is preferably 55 mN / m or more, and more preferably in the range of 60 to 75 mN / m.
The surface energy can be obtained by a method similar to the method for calculating the surface energy of the optically anisotropic layer described above.

  The thickness of the cellulose acetate film is usually preferably in the range of 5 to 500 μm, preferably in the range of 20 to 250 μm, more preferably in the range of 30 to 180 μm, and particularly preferably in the range of 30 to 110 μm.

[Use of retardation plate]
The retardation plate of the present invention can be used for an elliptically polarizing plate in combination with a polarizing film. Furthermore, it contributes to the expansion of the viewing angle by being applied to a transmissive, reflective, and transflective liquid crystal display device in combination with a polarizing film.
The elliptically polarizing plate and liquid crystal display device using the retardation plate of the present invention will be described below.

(Ellipse polarizing plate)
An elliptically polarizing plate can be produced by laminating the retardation plate of the present invention and a polarizing film. By using the retardation plate of the present invention, an elliptically polarizing plate capable of expanding the viewing angle of a liquid crystal display device can be provided.
Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The polarization axis of the polarizing film corresponds to a direction perpendicular to the stretching direction of the film.

  The polarizing film is laminated on the optically anisotropic layer side of the retardation plate. It is preferable to form a transparent protective film on the surface opposite to the side on which the retardation film of the polarizing film is laminated. The transparent protective film preferably has a light transmittance of 80% or more. As the transparent protective film, generally a cellulose ester film, preferably a triacetyl cellulose film is used. The cellulose ester film is preferably formed by a solvent cast method. The thickness of the transparent protective film is preferably 20 to 500 μm, and more preferably 50 to 200 μm.

(Liquid crystal display device)
By using the retardation plate of the present invention, a liquid crystal display device with an enlarged viewing angle can be provided. TN mode liquid crystal cell retardation plates (optical compensation sheets) are described in JP-A-6-214116, US Pat. Nos. 5,583,679, 5,646,703, and German Patent 3,911,620A1. Further, a retardation plate for liquid crystal cells in IPS mode or FLC mode is described in JP-A-10-54982. Furthermore, a retardation plate for an OCB mode or HAN mode liquid crystal cell is described in US Pat. No. 5,805,253 and International Publication WO 96/37804. Furthermore, a retardation plate for an STN mode liquid crystal cell is described in JP-A-9-26572. A VA mode liquid crystal cell retardation plate is described in Japanese Patent No. 2866372.

With reference to the above-mentioned publication, liquid crystal cell retardation plates (optical compensation sheets) of various modes can be produced. The retardation plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Super Twisted Nematic), VA (Vertically Aligned), and HAN. It can be used for liquid crystal display devices of various display modes such as (Hybrid Aligned Nematic) mode.
The liquid crystal display device includes a liquid crystal cell, a polarizing element, and a phase difference plate (optical compensation sheet). A polarizing element generally comprises a polarizing film and a protective film. As the polarizing film and the protective film, those described for the elliptically polarized light can be used.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, ratios, operations and the like shown in the following examples can be appropriately changed without departing from the technical idea of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

Example 1 [Production of high Δn (high refractive index anisotropy) type retardation plate]
(Preparation of alignment film)
An alignment film (SE-150 (manufactured by Nissan Chemical Industries, Ltd.)) was applied on a glass substrate, heated at 100 ° C. for 10 minutes, and at 200 ° C. for 1 hour, and then rubbed to form an alignment film layer. The thickness of the obtained alignment film layer was 0.1 μm.

(Formation of optically anisotropic layer)
A dichloromethane solution of exemplary compound (1), which is a liquid crystal compound of the present invention, was applied onto the rubbed alignment film prepared above using a # 4 wire bar. Then, after putting in a 200 degreeC thermostat and hold | maintaining for 1 minute, when the sample was cooled quickly, orientation was fixed in the glass state, the optically anisotropic layer was formed, and the phase difference plate was obtained. The thickness of the optically anisotropic layer was 1.4 μm.

Example 2 [Production of low wavelength dispersion type retardation plate]
(Formation of optically anisotropic layer)
A dichloromethane solution of Exemplified Compound (7), which is a liquid crystal compound of the present invention, was applied onto the alignment film produced by the same method as in Example 1 using a # 4 wire bar. Thereafter, the sample is placed in a constant temperature bath at 260 ° C. and held for 1 minute, then placed in a constant temperature bath at 230 ° C. and held for 1 minute, and then the sample is quickly cooled. Was formed, and a phase difference plate was obtained. The thickness of the optically anisotropic layer is 2.0 μm.

Comparative Example 1 [Production of Comparative Retardation Plate]
(Formation of optically anisotropic layer)
A dichloromethane solution of the following comparative liquid crystal compound (1) is applied onto the alignment film produced in the same manner as in Example 1 using a # 4 wire bar. Then, after putting in a thermostat of 190 degreeC and hold | maintaining for 1 minute, when the sample was cooled rapidly, orientation was fixed in the glass state and the phase difference plate was obtained. The thickness of the optically anisotropic layer is 2.0 μm.

  Comparative liquid crystal compound (1)

[Evaluation of retardation plate]
(Measurement of Δn)
Δn of the phase difference plates obtained in Examples 1 and 2 and Comparative Example 1 was determined by using an ellipsometer (APE-100, manufactured by Shimadzu Corporation) and an observation angle using a wavelength of 632.8 nm. Retardation is measured by changing, and calculating with the method described in Designing Concepts of the Discotic Negative Compensation Films SID98 DIGEST, assuming a refractive index ellipsoid model. The results are shown in Table 1.

(Measurement of chromatic dispersion)
The wavelength dependence of retardation in the normal direction of the sheet surface of the retardation plate obtained in Examples 1 and 2 and Comparative Example 1 was measured using KOBRA (manufactured by Oji Scientific Instruments). The value of chromatic dispersion is represented by a value obtained by dividing the retardation value at 478 nm by the retardation value at 747 nm. The results are shown in Table 1.

(Measurement of alignment completion time)
In Examples 1 and 2 and Comparative Example 1, the time required for each liquid crystal compound to disappear from the alignment defect and become monodomain alignment from the start of heating is measured. While observing a polarizing microscope (OPTIPHOTO2, manufactured by Nikon Co., Ltd.), the temperature is maintained and the maturing is advanced to measure the time. The results are shown in Table 1.

(Production of liquid crystal display device)
A polyimide alignment film was provided on a glass substrate on which an ITO transparent electrode was provided, and a rubbing treatment was performed. Two substrates are stacked with a 5 μm spacer so that the alignment films face each other. The two substrates are arranged so that the rubbing directions of the alignment films are orthogonal. A rod-like liquid crystal molecule (ZL4792, manufactured by Merck & Co., Inc.) is injected into the gap between the substrates to form a rod-like liquid crystal layer. Δn of the rod-like liquid crystal molecules is 0.0969. Two prepared retardation plates were attached to both sides of the TN liquid crystal cell manufactured as described above so that the optically anisotropic layer faced the substrate of the liquid crystal cell. Furthermore, two polarizing plates were affixed to the outside of them to produce a liquid crystal display device. The rubbing direction of the alignment film of the phase difference plate and the rubbing direction of the alignment film of the liquid crystal cell adjacent thereto are arranged so as to be antiparallel. Moreover, it arrange | positioned so that the absorption axis of a polarizing plate and the rubbing direction of a liquid crystal cell may become parallel. A voltage is applied to the liquid crystal cell of the liquid crystal display device, and the transmittance ratio between white display and black display in white display 2 V and black display 5 V is used as a contrast ratio, and a region with a contrast ratio of 10 in the vertical and horizontal directions and no gradation inversion is viewed. Measured as a corner. In addition, the angle dependency of the hue during white display and black display was visually observed. The results are shown in Table 1.

From the results shown in Table 1, the discotic liquid crystal compound of the present invention used in Example 1 has a larger Δn value than the conventionally known discotic liquid crystal compound used in Comparative Example 1. I understand that. By increasing Δn, the thickness of the optically anisotropic layer can be reduced, and further, the time required for orientation can be shortened. Furthermore, it can be seen that, despite the increase in Δn, the value of the wavelength dispersion is not different from that of the conventional discotic liquid crystalline compound, so that the performance of the retardation plate is maintained.
It can also be seen that the discotic liquid crystal compound of the present invention used in Example 2 has a smaller wavelength dispersion than the conventionally known discotic liquid crystal compound used in Comparative Example 1. By this effect, the color change which is one of the performances of the phase difference plate is improved. Furthermore, although the wavelength dispersion is reduced, the value of Δn is not different from that of the conventional discotic liquid crystal compound, so that the film thickness and the alignment time can be maintained.

Example 3 [Production of retardation plate]
(Preparation of transparent support)
The following components were put into a mixing tank and heated and stirred to prepare a cellulose acetate solution (dope).

[Cellulose acetate solution composition]
Cellulose acetate having an acetylation degree of 60.9% 100 parts by mass Triphenyl phosphate 6.5 parts by mass Biphenyl diphenyl phosphate 5.2 parts by mass The following retardation increasing agent (1) 0.1 part by mass The following retardation increasing agent ( 2) 0.2 parts by mass Methylene chloride 310.25 parts by mass Methanol 54.75 parts by mass 1-butanol 10.95 parts by mass

  Retardation raising agent (1)

  Retardation increasing agent (2)

  The obtained dope was cast from a casting port onto a drum cooled to 0 ° C. The film is peeled off at a solvent content of 70% by mass, both ends in the width direction of the film are fixed with a pin tenter, and the stretch rate in the width direction (direction perpendicular to the machine direction) is in a region where the solvent content is 3 to 5% by mass. Was dried while maintaining an interval of 3%. Then, it is further dried by transporting between the rolls of the heat treatment apparatus, and the stretching ratio in the machine direction is substantially 0% in the region exceeding 120 ° C. (in consideration of 4% stretching in the machine direction when stripping). A cellulose acetate film having a thickness of 100 μm was prepared by adjusting the ratio of the stretching ratio in the width direction to the stretching ratio in the machine direction to be 0.75. When the retardation of the produced film was measured at a wavelength of 632.8 nm, the retardation in the thickness direction was 40 nm, and the in-plane retardation was 4 nm. The produced cellulose acetate film was used as a transparent support.

(Formation of first undercoat layer)
On the transparent support, a coating solution having the following composition was applied at 28 ml / m ² and dried to form a first undercoat layer.

[First undercoat layer coating solution composition]
Gelatin 5.42 parts by mass Formaldehyde 1.36 parts by mass Salicylic acid 1.60 parts by mass Acetone 391 parts by mass Methanol 158 parts by mass Methylene chloride 406 parts by mass Water 12 parts by mass

(Formation of second undercoat layer)
On the first undercoat layer, 7 ml / m ² of a coating solution having the following composition is applied and dried to form a second undercoat layer.

[Second undercoat layer coating solution composition]
The following anionic polymer 0.79 parts by mass Citric acid monoethyl ester 10.1 parts by mass Acetone 200 parts by mass Methanol 877 parts by mass Water 40.5 parts by mass

  Anionic polymer

(Formation of back layer)
On the opposite side of the transparent support, a coating solution having the following composition was applied at 25 ml / m ² and dried to form a back layer.

[Back layer coating composition]
Cellulose diacetate with an acetylation degree of 55% 6.56 parts by mass Silica matting agent (average particle size: 1 μm) 0.65 parts by mass Acetone 679 parts by mass Methanol 104 parts by mass

(Formation of alignment film)
The following modified polyvinyl alcohol and glutaraldehyde (5% by mass of the modified polyvinyl alcohol) were dissolved in a methanol / water mixed solvent (volume ratio = 20/80) to prepare a 5% by mass solution.
Modified polyvinyl alcohol

This solution was applied onto the second undercoat layer, dried with hot air at 100 ° C. for 120 seconds, and then rubbed to form an alignment film layer. The film thickness of the obtained alignment film layer is 0.5 μm.
The rubbing direction of the alignment film is parallel to the casting direction of the transparent support.

(Formation of optically anisotropic layer)
An optically anisotropic layer coating solution having the following composition is applied onto the rubbed alignment film prepared above using a # 4 wire bar.

[Optical anisotropic layer coating solution]
Liquid crystal compound of the present invention (Exemplary compound (9)) 100 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.9 parts by mass Photopolymerization initiator
(Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) 3.3 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1.1 parts by mass Methyl ethyl ketone 250 parts by mass

The film coated with the optically anisotropic layer was placed in a thermostatic bath at 130 ° C., heated to 125 ° C. over about 20 seconds, held for 60 seconds, and then cooled to 80 ° C. over about 20 seconds. . While maintaining the same temperature, 200 mJ / cm ² of ultraviolet light was irradiated to fix the alignment state of the optically anisotropic layer. The mixture was allowed to cool to room temperature to obtain a retardation plate. The thickness of the formed optically anisotropic layer is 1.74 μm.

Example 4 [Production of retardation plate]
An optically anisotropic layer coating solution having the following composition is applied onto the rubbed alignment film prepared in Example 3 using a # 4 wire bar.

[Optical anisotropic layer coating solution]
Liquid crystal compound of the present invention (Exemplary compound (11)) 100 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.9 parts by mass Photopolymerization initiator (Irgacure 907, Japan) Ciba Geigy Co., Ltd.) 3.3 parts by mass Sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 1.1 parts by mass Methyl ethyl ketone 250 parts by mass

The film coated with the optically anisotropic layer was placed in a thermostatic bath at 145 ° C., heated to 140 ° C. over about 20 seconds, held for 60 seconds, and then cooled to 95 ° C. over about 30 seconds. . While maintaining the same temperature, 200 mJ / cm ² of ultraviolet light was irradiated to fix the alignment state of the optically anisotropic layer. The mixture was allowed to cool to room temperature to obtain a retardation plate. The formed optically anisotropic layer has a thickness of 1.71 μm.

Example 5 [Production of retardation plate]
An optically anisotropic layer coating solution having the following composition is applied onto the rubbed alignment film prepared in Example 3 using a # 4 wire bar.

[Optical anisotropic layer coating solution]
Liquid crystal compound of the present invention (Exemplary compound (15)) 100 parts by mass Ethylene oxide-modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.9 parts by mass Photopolymerization initiator (Irgacure 907, Japan) Ciba Geigy Co., Ltd.) 3.3 parts by mass Sensitizer (Kayacure DETX, Nippon Kayaku Co., Ltd.) 1.1 parts by mass Methyl ethyl ketone 250 parts by mass

The film coated with the optically anisotropic layer was placed in a thermostatic bath at 130 ° C., heated to 125 ° C. over about 20 seconds, held for 60 seconds, and then cooled to 80 ° C. over about 20 seconds. . While maintaining the same temperature, 200 mJ / cm ² of ultraviolet light was irradiated to fix the alignment state of the optically anisotropic layer. The mixture was allowed to cool to room temperature to obtain a retardation plate. The thickness of the formed optically anisotropic layer is 1.75 μm.

Comparative Example 2 [Production of Comparative Retardation Plate]
An optically anisotropic layer coating solution having the following composition was applied to the alignment film prepared in Example 3 using a # 4 wire bar.
[Optical anisotropic layer coating solution]
Discotic liquid crystal compound (Comparative liquid crystal compound (2)) 100 parts by mass Ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.) 9.9 parts by mass Photopolymerization initiator (Irgacure 907, Nippon Ciba-Geigy Co., Ltd.) 3.3 parts by mass Sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 1.1 parts by mass Cellulose acetate butyrate (CAB 551.0.2, manufactured by Eastman Chemical Co., Ltd.) 2 .2 parts by mass (CAB 531.1, manufactured by Eastman Chemical Co., Ltd.) 0.55 parts by mass Methyl ethyl ketone 250 parts by mass

  Comparative liquid crystal compound (2)

The film coated with the optically anisotropic layer was placed in a thermostatic bath at 130 ° C., heated to 125 ° C. over about 20 seconds, held for 60 seconds, and then cooled to 80 ° C. over about 20 seconds. . While maintaining the same temperature, 200 mJ / cm ² of ultraviolet light was irradiated to fix the alignment state of the optically anisotropic layer. The mixture was allowed to cool to room temperature to obtain a retardation plate. The thickness of the formed optically anisotropic layer is 1.75 μm.

  The retardation plates of Examples 3, 4 and 5 and the retardation plate of Comparative Example 2 are placed on both sides of the produced TN liquid crystal cell, and the two retardation plates are liquid crystal cell substrates. Affixed to face. A voltage was applied to the liquid crystal cell of the liquid crystal display device, and the contrast ratio of the white display and the black display in the white display 2V and the black display 5V and the evaluation of the angle dependency of the color were visually evaluated. As a result, the phase difference plates of Examples 3, 4, and 5 using the discotic liquid crystalline compound of the present invention showed less change in color than the case of Comparative Example 2.

Claims (8)

A retardation plate having an optically anisotropic layer formed from a compound represented by the following general formula (I) on a support.
Formula (I)
^{[(R 1) a-M-} (L 1)] b- (L 2)
In the above general formula (I):
R ¹ represents an alkyl group having 1 to 20 carbon atoms. The —CH ₂ — group in the alkyl group is substituted with —O—, —S—, —C (═O) —, —N (R ² ) —, —CH═CH—, —C≡C—. However, -O- and -O- are not directly bonded.
R ² represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.
M represents a group consisting of three or more aromatic rings.
L ¹ represents a single bond or a divalent alkylene group having 1 to 10 carbon atoms. The —CH ₂ — group in the alkylene group may be substituted with —O—, —S—, —C (═O) —, —N (R ² ) —, but —O— and —O— -And are not directly bonded.
L ² represents a cyclic, alkene or alkyne b-valent group.
a represents the number of R ¹ substituting for M. b represents an integer of 2 to 6.   2. The retardation plate according to claim 1, wherein in the compound represented by the general formula (I), a plurality of Ms are not conjugated by multiple bonds.   The retardation plate according to claim 1 or 2, wherein M in the general formula (I) is a group having a triphenylene ring.   The phase difference plate according to claim 1, wherein the compound represented by the general formula (I) exhibits liquid crystallinity.   The phase difference plate according to claim 1, wherein the compound represented by the general formula (I) is a liquid crystalline compound having a polymerizable group. The phase difference plate according to claim 1, wherein the compound represented by the general formula (I) is a compound represented by the general formula (II).
Formula (II)

In general formula (II):
R ¹ and L ¹ have the same meanings as those in formula (I).
L ⁴ represents a cyclic, alkene or alkyne divalent group.
e represents the number substituted on the triphenylene ring.
Note that the two triphenylene rings bonded through L ¹ and L ⁴ are not conjugated. A compound represented by the following general formula (II).
Formula (II)

In general formula (II):
R ¹ and L ¹ have the same meanings as those in formula (I).
L ⁴ represents a cyclic, alkene or alkyne divalent group.
e represents the number substituted on the triphenylene ring.
Note that the two triphenylene rings bonded through L ¹ and L ⁴ are not conjugated.   8. The compound according to claim 7, wherein the compound represented by the general formula (II) is a liquid crystalline compound having a polymerizable group.