JPH08240795A - Liquid crystal element and its production - Google Patents

Abstract

PURPOSE: To provide a liquid crystal element having good driving characteristics such as contrast and response speed and to provide its production method by forming a liquid crystal/polymer separated structure by a simple process to improve shock resistance. CONSTITUTION: This element has a structure comprising a low mol.wt. liquid crystal 5 and a partitioning part 4 containing a high mol.wt. liquid crystal, and this structure is held between two substrates 2 which have transparent electrodes and are disposed with the electrodes facing each other. The low mol.wt. liquid crystal part is produced by dissociating a high mol.wt. liquid crystal with light. The production method of the liquid crystal element includes the following process. A high mol.wt. liquid crystal having such a structure that the liquid crystal groups are dissociated with light, or a liquid crystal material comprising this high mol.wt. liquid crystal and a low mol.wt. liquid crystal is supplied into the space between a pair of substrates at least one of which has a transparent electrode and which are disposed with the electrodes facing each other. The liquid crystal material is subjected to orientation. The high mol.wt. liquid crystal is irradiated with light from outside of the substrates so that the liquid crystal is partially dissociated with light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal element which can apply stress to various optical elements and is particularly applicable to a large screen display and a flexible liquid crystal element using a film substrate, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Liquid crystal panels are expected to be applied to large-screen displays because they can be driven with low electric power, are light in weight, and can be constructed as thin panels, and are being developed. Among them, the ferroelectric liquid crystal that responds to an electric field at a high speed and has excellent field-of-view characteristics has a memory property, so simple matrix drive is possible, and attention is focused on it as a material for realizing high-definition and large-screen liquid crystal display elements. Has been done. However, the ferroelectric liquid crystal has a problem that it is vulnerable to impact and uniform alignment in a large area is difficult. Therefore, as one of attempts to improve these problems, studies have been made to impart high impact resistance and orientation by polymerizing a ferroelectric liquid crystal (JP-A-55-21479). However, there is a problem that the viscosity increases due to the high molecular weight and the response speed becomes slow by about two digits. Further, it is disclosed that impact resistance can be improved by using a polymer-dispersed ferroelectric liquid crystal in which a ferroelectric liquid crystal is dispersed in a polymer (Japanese Patent Laid-Open No. 63-264724). However, in this polymer-dispersed ferroelectric liquid crystal, it is difficult to control the alignment of the ferroelectric liquid crystal that exists as droplets, and scattering occurs due to the difference in the refractive index between the ferroelectric liquid crystal and the polymer, which lowers the contrast. There is a problem of doing. On the other hand, a composition of a photo-curable polymer and a ferroelectric liquid crystal is sandwiched between a pair of substrates that have been subjected to an alignment treatment in order to improve impact resistance while maintaining the high-speed response of the ferroelectric liquid crystal. It has been proposed to irradiate light through a photomask and cure a polymer precursor according to a required pattern to form a phase-separated structure (JP-A-6-160818 and JP-A-6-186533).
issue). However, in this method, since the liquid crystal composition is a low molecular weight compound in the process before curing, the larger the area, the more problematic the production.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to construct a liquid crystal / polymer separation structure which improves impact resistance in a simple process, and to provide a liquid crystal device having good driving characteristics such as contrast and response speed. It is to provide the manufacturing method.

[0004]

The present invention will be summarized as follows. A first invention of the present invention relates to a liquid crystal element,
It has a structure composed of a partition wall containing polymer liquid crystals and a low molecular weight liquid crystal between two substrates having transparent electrodes so that their electrode surfaces are opposed to each other. It is characterized by being generated by photodissociation. A second invention of the present invention relates to a method for manufacturing a liquid crystal element, wherein a liquid crystal group is provided between the substrates arranged such that the electrode surfaces of a pair of substrates having at least one transparent transparent electrode face each other. A step of sandwiching a polymer liquid crystal having a structure that dissociates by light or a liquid crystal material composed of a composition of this polymer liquid crystal and a low molecular weight liquid crystal, a step of performing an alignment treatment of the liquid crystal material, and irradiating light from outside the substrate And partially photodissociating the polymer liquid crystal.

The present invention can facilitate the production of a large-screen liquid crystal device by utilizing a polymer liquid crystal to simplify the alignment treatment and, after forming the device, producing a high-speed response component. Since the manufactured liquid crystal element has a liquid crystal / polymer separation structure, it has good impact resistance, has good contrast and viewing angle, and can be driven at a response speed comparable to that of low-molecular ferroelectric liquid crystals. An area liquid crystal element can be realized. The present invention also provides a manufacturing method capable of realizing such a liquid crystal element. The advantage of the second invention of the present invention is that
In particular, after the photodissociation type polymer liquid crystal is dissociated, the liquid crystal region to be formed exhibits a ferroelectric liquid crystal phase, so that a liquid crystal device capable of high-speed response can be manufactured. In addition, light irradiation is performed by a method of limiting an irradiation region by using a photomask provided outside the substrate, whereby a large area can be easily processed at one time. Alternatively, by performing a method of scanning light such as a laser, it is not necessary to prepare a mask, and pixels can be easily formed. On the other hand, since the alignment method before light irradiation can be manufactured by a method that does not use an alignment film, a large area can be uniformly and easily treated, and can also be manufactured by a continuous process.
Further, a transmissive or reflective liquid crystal display element can be manufactured by disposing a polarizing plate on the outside of at least one of the pair of substrates.

Hereinafter, the present invention will be described in detail. First, the embodiments of the present invention are listed below. The first aspect of the present invention is as follows: (1) The liquid crystal region formed by dissociation of the polymer liquid crystal exhibits a ferroelectric liquid crystal phase. (2) A polarizing plate is arranged outside at least one of the pair of substrates. (3) The above-mentioned photodissociated polymer liquid crystal is a side chain polymer liquid crystal having polymethacrylic acid or polysilane as a main chain. (4) The polymer liquid crystal that undergoes photodissociation is a side chain polymer liquid crystal, and has a photodissociative group in a spacer portion that connects the main chain and the liquid crystal side chain portion. (5) As the photolabile group, -SS-, -CS-,
It is characterized by containing a -C (= O) -S- or -Si-Si- bond. (6) The polymer liquid crystal that undergoes photodissociation is a main chain polymer liquid crystal. (7) The above-mentioned photopolymerizable crosslinkable polymer liquid crystal is produced by photocrosslinking or dimerization, and is characterized by becoming a single liquid crystal molecule by a photoreaction. (8) The above-mentioned photodissociated polymer liquid crystal dissociates a liquid crystal group by a photooxidation reaction. The second invention of the present invention is as follows: (1) The alignment treatment of the liquid crystal material is performed by shear stress or stretching. (2) The light irradiation is performed by a method of limiting an irradiation area by using a photomask provided outside the substrate. (3) The light irradiation is performed by a method of scanning light such as a laser. (4) The light irradiation is performed by raising the temperature of the liquid crystal element so that the liquid crystal and the polymer liquid crystal do not phase separate.

The liquid crystal material of the present invention comprises a polymer liquid crystal that dissociates a liquid crystal group by light, or a composition of the polymer liquid crystal and a low molecular liquid crystal. As a method for applying this liquid crystal material, a bar coater as a solution is applied on the electrode surface of the substrate with a transparent electrode,
There are a method of applying by a roll coater and screen printing and drying the solvent, and a method of applying the material in a liquid crystal or liquid state without diluting it. The thickness of the liquid crystal material can be controlled by the concentration of the solution and the coating speed, but can also be set to a predetermined thickness by using a spacer. Further, the other substrate is placed so that the electrode surfaces face each other, and laminated by lamination. Although glass can be used as the substrate, it is desirable to use a resin that is light and durable against bending. Examples of such a substrate include polyether sulfone (PES), polyimide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polypropylene and the like. When used as a substrate, it is preferably one having a small birefringence. Known electrodes are used as the electrodes, specifically, indium oxide film (ITO film), gold, titanium, NE.
A conductive film such as an SA film can be used. When manufacturing an element for the purpose of matrix driving, electrodes are linearly patterned and used.

The polymer of the present invention which dissociates a liquid crystal group by light is
It is desirable that the reaction quantum yield for dissociating the liquid crystal group is high and that a by-product that deteriorates the characteristics of the liquid crystal phase is not generated. Such polymers include, for example, a side chain type polymer liquid crystal having a main chain (for example, methacrylic acid, polysilane, etc.) that dissociates by light, or a main chain of polyacrylic acid, polyether, polyester, polysiloxane, etc. It may have no dissociation property, and a bond [-S-S-, -C] that dissociates the liquid crystal group and the main chain by light in the side chain portion.
H ₂ -S-, -C (= O) -S-, -SC-(= S)-
Or -Si-Si- and the like], a side chain type polymer liquid crystal, or a polymer liquid crystal in which dissociation of a liquid crystal group due to photooxidation occurs. There is also a main chain type polymer liquid crystal that is dissociated into a liquid crystal group by light. Further, a material which is a cross-linked polymer liquid crystal produced by photo-crosslinking or dimerization and becomes a single liquid crystal molecule by a photoreaction may be used.

As the liquid crystal composition, in addition to the above-mentioned polymer liquid crystal, a low molecular weight liquid crystal composition is mixed and used in advance to such an extent that the manufacturability is not deteriorated, whereby liquid crystal temperature characteristics, tilt angle and spiral are obtained. The pitch, response speed, etc. can be improved.
At this time, the ratio of the low-molecular liquid crystal composition is 0 to 9 of all liquid crystal materials.
0%, preferably about 5-40% is suitable.

As an alignment method, it is possible to perform alignment using an alignment film that has been subjected to a rubbing treatment, but in the case of a film substrate, the method used for polymer liquid crystals can be used. That is, the method by stretching as described in JP-A-63-318526 and JP-A-2-123331.
Orientation can be achieved by using shear stress as described in Japanese Patent Laid-Open Publication No. 3-57727 or by applying bending stress as described in Japanese Laid-Open Patent Publication No. 3-5727. Alternatively, the orientation is possible by extrusion.

As a method of irradiating light, a photomask is installed on the outside of the substrate so as to shield the portion other than the pixel portion, and parallel light is radiated, or a desired pixel portion is radiated by scanning a laser or the like. There is a way to do it. Further, when further fine light irradiation is desired, it is possible to utilize light interference. The ratio of the irradiated area to the shielded area is preferably 100: 1 to 1: 1. That is, if the irradiated area is too large, the impact resistance is deteriorated, and conversely, if there are many shielded areas, many areas do not operate, which is not suitable for display. For this reason, it is desirable to have a structure in which each pixel is surrounded by a shielding portion, or a structure in which a polymer region is present in the pixel to the extent that it cannot be seen as scattering. It is also effective to raise the temperature of the liquid crystal cell during exposure so that the liquid crystal and the polymer liquid crystal do not phase separate. Furthermore,
A polarizing plate is installed outside the substrate to form a liquid crystal element, which can be used as a display element. As the configuration of the liquid crystal element, a simple matrix type configuration and an active matrix type configuration using a TFT, MIM or the like are possible.

[0012]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The product is identified by nuclear magnetic resonance spectrum (NMR)
And infrared absorption spectrum (IR). The molecular weight of the liquid crystal polymer was calibrated by gel permeation chromatography (GPC) using polystyrene as a standard. Liquid crystal phase and phase transition temperature are measured by differential scanning calorimeter (DS
C) Determined by measurement and observation with a polarizing microscope. The response speed is measured by 10 × 10 with 10 μm spacers scattered.
A cell was prepared using a 10 mm ITO glass substrate, an electric field (15 V / μm) was applied to this cell, and the average of the time required for 0 to 90% change in transmitted light amount and the time required for 100 to 10% at that time was returned. It was speed.

Example 1 FIG. 1 is a sectional view of a liquid crystal device of Example 1. This liquid crystal element comprises a PES film substrate 2 having transparent electrodes 3 arranged opposite to each other, a partition wall 4 containing a polymer liquid crystal and a liquid crystal layer 5 sandwiched between the PES film substrate 2 and a polarizing plate 1 outside the substrate. A plurality of linear electrodes are formed on each film element (FIG. 2), and the linear electrodes 3 on both substrates are orthogonal to each other in the element. Such an element is manufactured as follows. In FIG. 2, reference numeral 6 denotes an electrode (1) and 7 denotes an electrode (2).

(Synthesis of polymer liquid crystal) 1 mol (126 g)
1000 ml containing 5% p-hydrothiophenol
The aqueous caustic soda solution was cooled to 0 to 10 ° C., and 1.5 mol (136 g) of acryloyl chloride was added dropwise thereto with stirring. After the reaction, the organic layer was extracted with diethyl ether,
The organic layer was washed twice with 10% aqueous sodium carbonate solution and then four times with water, and dried over anhydrous sodium sulfate containing 0.2 g of iodine. From the crude product (115 g) obtained by removing the drying agent and distilling the solvent under reduced pressure, 33.2 g of p-hydroxyphenylthioacrylate was obtained by silica gel column chromatography several times. 18 g of p-hydroxyphenylthioacrylate and 25 g of pn-octyloxybenzoic acid were suspended in 200 ml of anhydrous methylene chloride, 0.5 g of dimethylaminopyridine and 21 g of dicyclohexylcarbodiimide were added thereto, and the suspension was added at room temperature for 12 hours.
I stirred it for a while. After the reaction, the solid is removed by filtration,
48 g of a crude product obtained by distilling off the solvent under reduced pressure was recrystallized three times from ethyl alcohol to obtain 26 g of p-thioacrylphenyl p-n-octyloxybenzoate. 10
g of p-n-octyloxybenzoate p-thioacrylphenyl was dissolved in 100 ml of tetrahydrofuran,
0.04 g of azoisobutyronitrile (AIBN) was added, and the mixture was stirred at 80 ° C. for 18 hours. After the reaction, it was generated by reprecipitation, and a polymer having a molecular weight of 7500 was obtained.

(Production of device) In a PES film having a thickness of 100 μm and formed with ITO of 50 nm, a width of 1 m
The linear electrode of 1 was formed by etching. Next, as a liquid crystal material, 0.50 g of the above-mentioned polymer liquid crystal and 0.50 g of the ferroelectric liquid crystal composition ZLI4237-100 (manufactured by Merck & Co., Inc.) were mixed and dissolved in toluene, and then uniformly coated on a substrate with a bar coater. It was applied to a thickness of 2 μm. Further, a counter substrate was laminated, and a shear stress was applied by shifting both substrates to orient the liquid crystal material. After that, a photomask (FIG. 3) that covers portions other than pixels was covered, and UV irradiation was performed for 30 minutes by parallel light from a high-pressure mercury lamp having an intensity of 30 mW / cm ² through the mask. When the cell after light irradiation was observed with a polarization microscope, it was confirmed that the low-molecular liquid crystal region was formed with the same regularity and the same size as the photomask pattern. The phase transition temperature of the liquid crystal material in the light irradiation part is as follows. Chiral smectic C phase 60 Smectic A phase 70 Nematic phase 90 Isotropic phase (° C.) It was confirmed that the device had good orientation even without being disturbed in orientation even when wound around a cylinder having a radius of curvature of 5 cm. The response speed was 100 μs.

Comparative Example 1 An element was prepared by using the same material and method as in Example 1 except that light irradiation was not performed, and the response speed was measured.
It was ms.

Comparative Example 2 In the same liquid crystal element as in Example 1, a liquid crystal material made of only a low molecular weight liquid crystal composition was used, but the impact resistance was very poor.

[0018]

According to the method of the present invention, a polymer / low molecular weight liquid crystal separation structure can be easily prepared by dissociating the high molecular weight liquid crystal with light only in the pixel portion and converting it into a low molecular weight liquid crystal that responds at high speed. You can The liquid crystal element manufactured by that method has excellent impact resistance and can respond at high speed. Also,
The area of the liquid crystal element can be easily increased.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid crystal device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an electrode pattern (matrix) of a liquid crystal element according to Example 1 of the present invention.

FIG. 3 is a diagram showing a pattern of a photomask of a liquid crystal element according to Example 1 of the present invention.

[Explanation of symbols]

1: polarizing plate, 2: substrate, 3: electrode, 4: partition wall (polymer liquid crystal), 5: liquid crystal layer, 6: electrode (1), 7: electrode (2)

Claims (14)

[Claims] 1. A structure having a partition wall containing polymer liquid crystals and a low-molecular liquid crystal is provided between the substrates provided so that the electrode surfaces of two substrates having transparent electrodes are opposed to each other. A liquid crystal device, which is produced by photodissociating the polymer liquid crystal. 2. The liquid crystal device according to claim 1, wherein a liquid crystal region formed by dissociation of the polymer liquid crystal exhibits a ferroelectric liquid crystal phase. 3. The liquid crystal device according to claim 1, wherein a polarizing plate is arranged outside at least one of the pair of substrates. 4. The liquid crystal device according to claim 1, wherein the photodissociated polymer liquid crystal is a side chain polymer liquid crystal having polymethacrylic acid or polysilane as a main chain. 5. The photo-dissociating polymer liquid crystal is a side-chain polymer liquid crystal, and has a photo-dissociative group in a spacer portion connecting a main chain and a liquid crystal side chain portion. The liquid crystal element described. 6. The —S as the photolabile group according to claim 5.
-S-, -C-S-, -C (= O) -S- or -S
The liquid crystal device according to claim 1, comprising an i-Si-bond. 7. The liquid crystal device according to claim 1, wherein the photodissociated polymer liquid crystal is a main chain polymer liquid crystal. 8. The cross-linked polymer liquid crystal that undergoes photodissociation is produced by photo-crosslinking or dimerization, and becomes a single liquid crystal molecule by photoreaction. Liquid crystal element. 9. The liquid crystal device according to claim 1, wherein the photodissociated polymer liquid crystal dissociates a liquid crystal group by a photooxidation reaction. 10. A polymer liquid crystal having a structure in which a liquid crystal group is dissociated by light between substrates provided so that electrode surfaces of a pair of substrates having transparent electrodes, at least one of which is transparent, or a polymer thereof. It includes a step of sandwiching a liquid crystal material composed of a liquid crystal and a low-molecular liquid crystal composition, a step of performing an alignment treatment of the liquid crystal material, and a step of irradiating light from outside the substrate to partially photodissociate the polymer liquid crystal. A method for manufacturing a liquid crystal element, comprising: 11. The alignment treatment of the liquid crystal material is shear stress,
Alternatively, it is performed by stretching.
0. A method for manufacturing a liquid crystal element according to 0. 12. The method of manufacturing a liquid crystal element according to claim 10, wherein the light irradiation is performed by a method of limiting an irradiation area by using a photomask provided outside the substrate. 13. The light irradiation is performed by a method of scanning light such as a laser.
A method for manufacturing a liquid crystal device according to item 1. 14. The method of manufacturing a liquid crystal device according to claim 10, wherein the light irradiation is performed by raising the temperature of the liquid crystal device so that the liquid crystal and the polymer liquid crystal are not phase-separated.