JPH065343B2 - Liquid crystal element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal element used in a liquid crystal display element, a liquid crystal-optical shutter, or the like, and more specifically, by improving the initial alignment state of the liquid crystal element, The present invention also relates to a liquid crystal element having improved driving characteristics.

[Summary of Disclosure] The present specification and drawings show a compound represented by the following general formula (I) on at least one substrate in a liquid crystal device having a cell structure in which a smectic liquid crystal is sealed between a pair of substrates provided with electrodes. (In the formula, n represents an integer of 1 to 4) General formula (I) Disclosed is a technique for forming a uniform monodomain smectic phase by providing an orientation control film containing OH as an alcohol component of a polyester polymer.

[Prior Art] Conventionally, liquid crystal devices have been mainly used in M.P. Schadt and W. Helfrich's Applied Physics Let
ters) Vol. 18 No. 4 (February 15, 1971) P.127-128
The TN (Twisted Nematic) method is adopted. As a method of efficiently ensuring the alignment control of this TN method, the substrate interface in contact with the nematic liquid crystal is SiO or S by oblique vapor deposition.
There is known a method of forming an organic resin such as polyimide or polyamide by rubbing io ₂ or one side.

Since this TN method does not have high-speed response and memory effect, when designing a high-density pixel display panel using the TN method, for example, an active matrix substrate in which thin film transistors (TFT) are arranged in an array is required. . However, in such an active matrix drive type display panel using TN liquid crystal, since the TFT used has a complicated structure, the number of manufacturing steps is large, and high manufacturing cost is a bottleneck. However, there is a problem that it is difficult to form a thin film semiconductor (for example, polysilicon or amorphous silicon) forming a TFT over a large area.

As a solution to these problems, NAClark and S.
Ferroelectric liquid crystal elements proposed in T. Largerwall U.S. Pat. No. 4,367,924 are known.

Ferroelectric liquid crystals have a bistable state consisting of a first optical stable state and a second optical stable state with respect to an electric field. Therefore, unlike the liquid crystal element used in the above-mentioned TN type liquid crystal, for example, the liquid crystal is aligned in the first optically stable state with respect to one electric field vector and the second optical liquid crystal is oriented with respect to the other electric field vector. The liquid crystal is aligned in a stable state. In addition, this type of liquid crystal responds to an applied electric field very quickly in accordance with the above-mentioned 2
It has the property of taking one of the two stable states and maintaining that state when no electric field is applied. By utilizing such a property, a considerable substantial improvement can be obtained with respect to many of the problems of the above-mentioned conventional TN type element.

[Problems to be Solved by the Invention] However, in order for the ferroelectric liquid crystal to exhibit a predetermined characteristic, the liquid crystal injected between the pair of parallel substrates is irrelevant to the above-mentioned 2 It is necessary that the molecular arrangement is such that the exchange between the two stable states effectively occurs. Ferroelectric liquid crystal exhibits its behavior in the chiral smectic phase, and the liquid crystal molecular layer having this chiral smectic phase is perpendicular to the substrate surface, and therefore the region where the liquid crystal molecular axes are arranged substantially parallel to the substrate surface (monodomain ) Needs to be formed. However, in general, smectic phase liquid crystals have drawbacks of poorer alignment controllability and alignment stability than nematic phase liquid crystals, and in reality, sufficient properties have not been obtained.

In the experiments conducted by the inventors, it was found that a uniform monodomain smectic phase can be formed and a characteristic of a ferroelectric liquid crystal can be exhibited by using a specific alignment control film. Therefore, an object of the present invention is to provide a smectic phase having a uniform monodomain over the entire surface, particularly a chiral smectic C phase (SmC ^* ), an H phase (SmH ^* ), and an I phase (SmI) exhibiting ferroelectricity.
^The purpose of the present invention is to provide an alignment control film for forming a liquid crystal exhibiting an F phase (SmF ^* ) or a G phase (SmG ^* ).

[Means and Actions for Solving Problems] According to the present invention, in a liquid crystal element having a cell structure in which liquid crystal is sealed between a pair of substrates provided with electrodes, at least one of the pair of substrates is used. Is the following general formula (I)
There is provided a liquid crystal element having an alignment control film containing the compound represented by the above as an alcohol component of a polyester polymer.

General formula (I) (In the formula, n represents an integer of 1 to 4) FIG. 1 shows an embodiment of a liquid crystal element according to the present invention, in which 1 is a substrate, 2 is indium oxide or tin oxide provided on the substrate. , An electrode made of a transparent conductive film such as indium oxide-tin oxide, 3 is an alignment control film, and 4 is a liquid crystal substance.

In the polyester-based polymer used for the orientation control film 3,
The polyester-forming component is selected from compounds represented by general formula (I) as alcohol, preferably tris (2-hydroxyethyl) isocyanurate, and acid as terephthalic acid, isophthalic acid or benzophenonedicarboxylic acid. , And can be mixed with each other.

In the compound represented by the general formula (I), up to 80 equivalent% of the total number of hydroxyl groups can be replaced by the following polyhydric alcohol.

Examples of polyhydric alcohols are ethylene glycol, glycerin, pentaerythritol, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, sorbit, mannite, dipentaerythritol, butanediol-1, Four,
Trimethylene glycol, propylene glycol, pentanediol 1,5, neopentylene glycol, butene-
2-diol-1,4, butyne-2-diol-1,4,2,2,4,4-
Tetraethyl-1,3-cyclobutanediol, hydroquinone dibetahydroxyethyl ether, 1,4 cyclohexanedimethanol and the like can be mentioned.

In addition, the terephthalic acid, isophthalic acid, or benzophenone dicarboxylic acid moiety is 50% of the total number of carboxyl groups.
Up to the equivalent% can be replaced by the following polycarboxylic acids.

As the polycarboxylic acid, adipic acid, orthophthalic anhydride, hemmerytic acid, trimesic acid, trimellitic acid, succinic acid, tetrachlorophthalic anhydride, hexachloroendomethylenetetrahydrophthalic acid, maleic acid, sebacic acid, citric acid and the following (Imide)-(acid) and the like.

The formation of (imide)-(acid) is carried out by acid anhydride and diamine. Examples of acid anhydrides include trimellitic anhydride, pyromellitic dianhydride, and benzophenone.
-2,3,2 ', 3'-tetracarboxylic dianhydride, 2,
3,6,7-Naphthalene dianhydride, 3,4,3 ', 4'-
Diphenyltetracarboxylic dianhydride is included.
As the diamine, methylene dianiline, benzidine, 3,3'-diaminodiphenyl, 1,4-diaminonaphthalene, p-phenylenediamine, α, ω-nonamethylenediamine, 4,4'-diaminodiphenyl ether, 4 ,Four
-Dimethylheptamethylenediamine-1,7, diaminodiphenylketone, diaminodiphenylketone, bis- (4-aminophenyl) -α, α'-p-xylene, m-phenylenediamine, xylenediamine, hexamethylenediamine, ethylenediamine, Examples include 4,4′diaminodicyclohexylmethane and diaminodiphenyl sulfone.

(Imido)-(acid) is formed from 2 moles of acid anhydride with respect to 1 mole of diamine. For example, the following (imide)-(acid) is formed by the reaction of 2 mol of trimellitic anhydride with 1 mol of 4,4'-diaminodiphenyl ether or 4,4'-diaminodiphenylmethane.

R is -O- or -CH ₂ - terephthalic acid, isophthalic acid, and benzophenone dicarboxylic acid is used in the reaction in the form of such free acid, acyl halide or alkyl ester.

In the polyester formation, it is preferable to use an alcohol group in excess of the acid group, and usually, the number of hydroxyl groups in the alcohol component is 1.0 to 1.6 times the total number of carboxyl groups in the acid component.

As the solvent used in the polyester forming reaction, N-methylpyrrolidone, dimethylacetamide, dimethylpyrrolidone, dimethylsulfoxide, N-methylcaprolactam, xylene, cresylic acid, p-cresol, pm-cresoler mixture, dimethyl sulfone, and a mixed solvent. Used. Examples of the mixed solvent include a mixture of N-methylpyrrolidone and dimethylacetamide and / or dimethylformamide, a mixture of N-methylpyrrolidone-dimethylacetamide / toluene (6: 3: 4), a mixture of N-methylpyrrolidone and xylene, and the like. Is mentioned.

The obtained polyester polymer solution can be diluted with an aliphatic hydrocarbon and an aromatic hydrocarbon such as toluene, xylene, octane, decane, dodecane, and tetradecane. It is also possible to mix and use 1 to 5% of a melamine-formaldehyde resin, a phenol resin or the like.

"ISONEL" is a commercially available polyester polymer containing the compound of the general formula (I) as an alcohol component.
(Made by Schenectady Chemicals Incorporated), "ISOMID" (made by Nippon Shokubai Chemical Co., Ltd.), etc.

A coating solution containing these polyester-based polymers is applied onto a substrate provided with a transparent electrode by a spinner coating method or a screen printing method, and the solvent may be removed at a temperature of 150 to 300 ° C to form a film. it can.

After film formation, 20 to 200 g / cm ² cotton cloth or the like, preferably 100 g / cm ²
By rubbing under static pressure in the vicinity to form an alignment control film, and by filling a liquid crystal substance between the substrates, a liquid crystal display panel can be obtained. The general film thickness of the orientation control film 3 is
It is 100Å to 1 µ, preferably 500Å to 2000Å.

As the smectic liquid crystal used in the present invention, those exhibiting ferroelectricity are preferable, for example, SmC ^* , SmH ^* , SmI ^* , SmF ^*.
A liquid crystal composition having a chiral smectic phase such as or SmG ^* can be used.

An example of a liquid crystal showing a chiral smectic phase used in the liquid crystal element of the present invention is shown below.

These liquid crystals may be used alone or as a mixture of two or more kinds, or may be used as a mixture with another smectic liquid crystal or a collective (chiral nematic) liquid crystal.

FIG. 2 is a schematic drawing of an example of a cell for explaining the operation of the ferroelectric liquid crystal. 11a and 11b are substrates (glass plates) coated with a transparent electrode made of a thin film such as In ₂ O ₃ , SnO ₂ or ITO (Indium Tin Oxide), between which the liquid crystal molecular layer 12 is perpendicular to the glass surface. Oriented so that SmC ^* , Sm
Liquid crystals with a chiral smectic phase such as H ^* , SmF ^* , SmI ^* and SmG ^* are enclosed. A thick line 13 represents a liquid crystal molecule, and the liquid crystal molecule 13 has a helical structure when no voltage is applied. The liquid crystal molecule 13 has a dipole moment (P ₁ ) 14 in the direction orthogonal to the molecule. When a voltage of a certain threshold value or more is applied between the electrodes on the substrates 11a and 11b, the helical structure of the liquid crystal molecules 13 is unraveled,
The liquid crystal molecules 13 can change the orientation direction so that all the dipole moments (P ₁ ) 14 are oriented in the electric field direction. The liquid crystal molecule 13 has an elongated shape and exhibits refractive index anisotropy in the major axis direction and the minor axis direction thereof. Therefore, for example, if crossed Nicols polarizers are placed above and below the glass surface, the voltage application polarity is It can be easily understood that the liquid crystal optical modulation element changes its optical characteristics depending on the situation.

The liquid crystal cell used in the liquid crystal element of the present invention preferably has a sufficiently thin thickness (for example, 10 μm or less). As the liquid crystal layer becomes thin in this way, an electric field is reduced as shown in FIG. Even when the voltage is not applied, the helical structure of the liquid crystal molecule is unwound and becomes a non-helical structure, and the dipole moment P thereof is either upward (17a) or downward (17b). When an electric field Ea or Eb having a polarity equal to or greater than a certain threshold is applied to such a cell by the voltage applying means 19a and 19b, the dipole moment corresponds to the electric field vector of the electric field Ea or Eb. Then upwards
17a or downward 17b, and the liquid crystal molecule is changed to the first stable state 18a or the second stable state 18a accordingly.
Oriented to either one of b.

As described above, there are two advantages of using such a ferroelectric liquid crystal as a liquid crystal element. The first is that the response speed is extremely fast, and the second is that the alignment of the liquid crystal molecules has bistability.

The second point will be described with reference to FIG. 3. When the electric field Ea is applied, the liquid crystal molecules are aligned in the first stable state 18a, but this state is stable even when the electric field is cut off. When a reverse electric field Eb is applied, the liquid crystal molecules are oriented in the second stable state 18b to change the orientation of the molecules, but they remain in this state even when the electric field is cut off. Further, as long as the applied electric field does not exceed a certain threshold value, the respective alignment states are still maintained.

In order to effectively realize such bistability and high response speed, it is preferable that the cell is as thin as possible.

Even when forming an element with a liquid crystal having such a ferroelectric property, as described above, the Sm
A cell with a high monodomain property in which layers having a chiral smectic phase such as C ^* , SmH ^* , SmF ^* , SmI ^* SmG ^* are arranged perpendicularly to the substrate surface and liquid crystal molecules are aligned substantially parallel to the substrate surface. Is difficult to form, and it is the main purpose of the present invention to provide a solution to this point.

FIGS. 4A and 4B show an embodiment of the liquid crystal element of the present invention. FIG. 4 (A) is a plan view of the liquid crystal element of the present invention, and FIG. 4 (B) is its A ₁ -A ₂ sectional view.

In the cell structure 100 shown in FIG. 4 (B), a pair of glass plates or plastic plate substrates 101a and 101b (only one side may be a plastic substrate) are held by a spacer 109 at a predetermined interval, and the pair of substrates is used. Glue for sealing 11
It has a cell structure adhered at 0, and an electrode group (for example, a scanning voltage applying electrode group in the matrix electrode structure) composed of a plurality of transparent electrodes 102a is further formed on the substrate 101a, for example, in a strip pattern. It is formed in a predetermined pattern. On the substrate 101b, an electrode group (for example, a signal voltage applying electrode group in the matrix electrode structure) including a plurality of transparent electrodes 102b intersecting the transparent electrode 102a is formed.

On the substrates 101a and 101b, alignment control films 103a and 103b each containing a polyester polymer containing the compound represented by the general formula (I) as one component are provided.
The liquid crystal layer 104 injected into the cell structure 100 is SmC ^* , SmH ^* SmF ^* , SmI ^* due to the alignment control films 103a and 103b ^.
Chiral smectic phases such as SmG ^* are formed.

EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 A solution (a) having the following composition was applied onto a glass substrate provided with a stripe ITO film having a pitch of 100 μm and a width of 62.5 μm as an electrode under conditions of 1000 rpm for 5 seconds and 3000 rpm for 25 seconds with a spinner coating solution. The coating was applied and heated and dried at a temperature of 200 ° C. for 30 minutes and further at a temperature of 250 ° C. for 90 minutes to form a coating film.

Solution composition (a) ISOMID RL (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) 1.0g N-methylpyrrolidone 9.0g Next, a pair of glass substrates with a coating film are unidirectionally rubbed under a pressure of 100g / cm. Then, the pair of rubbed glass substrates were superposed so that the upper and lower rubbing directions were parallel to each other, and the periphery thereof was sealed except for a portion serving as an injection port. The distance between the two glass substrates at this time was 1 μm.

Next, p-decyloxybenzylidene-p'-amino-2-methylbutyl cinnamate (DOBAMBC) was heated to an isotropic phase, which was injected into the cell prepared above under reduced pressure from the injection port, I closed the entrance. The cell was cooled by slow cooling, and a pair of polarizers were placed in a crossed Nicol state while maintaining the temperature at about 70 ° C. Microscopic observation revealed that SmC ^* with a monodomain non-helical structure was formed. I was able to confirm that

Example 2 40 g of terephthalic acid, 17 g of ethylene glycol, 63 g of tris (2-hydroxyethyl) isocyanurate, and 63 g of reaction catalyst lead naphthenate (Pb 15% by weight) were placed in a four-necked froth equipped with a thermometer, a stirrer, and a cooling tube. ) 4g under nitrogen atmosphere
While continuously removing the distillate from the system at 170 ° C to 220 ° C, the mixture was heated and stirred for 8 hours, 31 g of terephthalic acid was added, and the mixture was further heated and stirred at 230 ° C.
After the reaction, 320 g of metacresol was added until the viscosity of 0% became Y1 / 2 to z with a Gardner viscometer, and after cooling to 40 ° C, 6 g of tetrabutyl titanate was added and filtered to obtain a product (A).

Next, using this polyester polymer, a solution having the following composition
Adjusted (b).

Solution composition (ii) Product 1.5 g n-methylpyrrolidone 12.0 g A liquid crystal element was produced in the same manner as in Example 1 except that this solution (ii) was used. Then, it was confirmed by the same method as in Example 1 that SmC ^* having a non-helical structure of the monodomain was formed.

[Effects of the Invention] As described above, according to the present invention, a uniform monodomain smectic phase, particularly a chiral smectic phase exhibiting ferroelectricity can be formed over the entire surface.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the liquid crystal element of the present invention. 2 and 3 are perspective views showing a liquid crystal cell used in the present invention. FIG. 4 (A) is a plan view showing an embodiment of the liquid crystal element of the present invention, and FIG. 4 (B) is a sectional view taken along line A ₁ -A ₂ . 1, 11a, 11b, 101a, 101b: Substrate 2, 102a, 102b: Electrode 3, 103a, 103b: Alignment control film 4, 104: Liquid crystal layer 15: Liquid crystal molecule layer 16: Liquid crystal molecule 17, 17a, 17b: Dipole Moment (17a: Upward, 17b: Downward) 18a: First stable state 18b: Second stable state 19a, 19b: Voltage applying means 100: Cell structure 109: Spacer member 110: Adhesive (seal member) 111a, 11b: Polarizer.

Claims (6)

[Claims] 1. In a liquid crystal device having a cell structure in which liquid crystal is sealed between a pair of substrates provided with electrodes, at least one of the pair of substrates is a compound represented by the following formula (I): In the formula, n represents an integer of 1 to 4) General formula (I) A liquid crystal device having an alignment control film containing as an alcohol component of a polyester polymer. 2. The liquid crystal element according to claim 1, wherein the alignment control film is subjected to a rubbing treatment. 3. The liquid crystal device according to claim 1, wherein the liquid crystal is a smectic liquid crystal. 4. The liquid crystal device according to claim 3, wherein the smectic liquid crystal is a ferroelectric liquid crystal. 5. The liquid crystal device according to claim 4, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal. 6. The liquid crystal device according to claim 5, wherein the chiral smectic liquid crystal forms a phase having a non-helical structure.