JPH10293309A - Manufacture of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal element manufacturing method capable of providing a liquid crystal element of high orientation stability and sticking durability of liquid crystal material through a simplified process, keeping the phase transition temperature of the liquid crystal material from changing and making recovery of the liquid crystal solution facile. SOLUTION: A liquid crystal cell formed by sandwiching a ferroelectrical liquid crystal material and a thermoplastic resin having a glass transition temperature Tg lower than the smectic phase transition temperature between a pair of electrode substrates is heated up to the isotropic transition temperature of the ferroelectrical liquid crystal material. The heated liquid crystal cell is cooled down to the temperature lower than the glass transition temperature Tg of the thermoplastic resin. The ferroelectrical liquid crystal material is then oriented by applying shearing force between the substrates of the cooled liquid crystal cell, and after heating the liquid crystal cell up to the thermoplastic resin glass transition temperature, a pair of substrates are fusion fixed by the thermoplastic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a liquid crystal display element suitably used in the field of optoelectronics.

[0002]

2. Description of the Related Art Since liquid crystal display elements are thin and lightweight, their use and improvement in the field of optoelectronics have been actively studied. The current mainstream of liquid crystal display elements uses a glass substrate as a substrate for forming a liquid crystal cell, but the manufacturing method involves a complicated method such as vacuum injection of liquid crystal after assembling the cell first. Has been taken. Also, the completed liquid crystal panel is vulnerable to impact,
Even if the glass substrate is broken, or if the glass substrate is not broken, there is a problem of strength such that liquid crystal easily flows when a finger is pressed and display is disturbed.

On the other hand, recently, a liquid crystal display element using a plastic substrate which is hard to be broken and which is easy to manufacture and process is being developed, but in this case, display disturbance due to pressing or the like has not been solved. Various proposals have been made as a method of solving such a strength problem. For example, Japanese Patent Application Laid-Open No. 5-27246 describes a method for improving the mechanical strength of a liquid crystal panel by connecting opposing substrates with columns of an ultraviolet curable resin uniformly distributed. In this method, a UV curable resin monomer is dissolved in a liquid crystal and injected into a cell, and then the UV curable resin monomer is cured by UV irradiation to form a column. It is difficult to grow as described above, and sufficient mechanical strength cannot be obtained.

JP-A-1-250930 discloses that a solution prepared by dissolving a non-liquid crystalline polymer and liquid crystal in a solvent is applied to one substrate, dried at room temperature, and further dried at 60 ° C. A method for manufacturing a scattering type liquid crystal display device by stacking them is described. In this method, the non-liquid crystalline polymer and the liquid crystal are used in a weight ratio of non-liquid crystalline polymer: liquid crystal of 100: 100 to 100: 300. When the amount of the non-liquid crystal polymer is large, the non-liquid crystal polymer can be directly visually observed in a birefringent liquid crystal display element, or the light transmittance is reduced due to unnecessary light scattering, so that it is not applicable. It is.

Japanese Patent Application Laid-Open No. 5-61051 discloses a liquid crystal display device in which a spacer and a column-shaped thermosetting polymer that is in contact between upper and lower substrates are disposed in a liquid crystal layer. However, there is no description of the distribution state of the columnar thermosetting polymer, and it is unclear whether the mechanical strength can be sufficiently improved and good display characteristics can be maintained. The column of the thermosetting polymer is formed by applying a mixture of a liquid crystal, a spacer, and a spherical thermosetting polymer having a diameter larger than that of the spacer to one of the substrates, and then arranging the opposing substrate to apply pressure and heat. It is formed by doing. Therefore, a step of forming the thermosetting polymer into a sphere is required in advance,
There is a problem that it is necessary to select a material capable of forming a spherical object.

JP-A-6-59246 discloses that 0.6
Liquid crystal droplet of 0.1 to 2.0 μm and 0.1 to 0.5 for holding the liquid crystal droplet
A light modulation element in which a liquid crystal layer is made of a polymer material having a partition wall thickness of μm and has a light modulation function of scattering and transmitting light is described. In this device, since the liquid crystal is an independent layer, alignment cannot be controlled, and only scattering and non-scattering display can be performed. Even if a polarizing plate is arranged outside the device, practical display cannot be performed. In Comparative Example 1, the liquid crystal and the polymer material composition were in an isotropic phase, that is, in a state where they were mutually compatible,
Although a relatively transparent element is obtained by curing with ultraviolet light, the polymer material cannot grow to a sufficient size and the mechanical strength does not improve sufficiently because the phase separation progresses only when the polymer material cures. . In this method, it is necessary to select a polymer material compatible with the liquid crystal.

Japanese Patent Application Laid-Open No. 60-153025 discloses a liquid crystal display device in which a plastic film substrate is used as a substrate, and a mechanical strength is improved by fixing a spherical gap material to an alignment control film. However, it is difficult to fix the gap material without impairing the orientation of the orientation control film, and since only the spherical gap material is fixed, the bonding area is small, and the strength against strong pressing is insufficient. is there.

[0008] Japanese Patent Application Laid-Open No. 7-56145 discloses 0.1
By adding 10 to 10% by weight of a polymer material to the liquid crystal layer,
A non-scattering type liquid crystal display device having a steep display voltage threshold characteristic is described. However, there is no mention of improving the mechanical strength of the obtained liquid crystal display element, and there is no description of how to distribute the polymer material. Also, as described in the detailed description of the publication, simply adding an ultraviolet-curing resin and irradiating the substrate with ultraviolet light after injecting it between the substrates does not result in a resin having a sufficient size and a mechanical strength. Does not improve.

JP-A-8-6075 describes a method in which a mixture with an uncured curable resin is sandwiched in a phase-separated state, and the curing method is heat or light irradiation.
However, in this method, it is difficult to recover the liquid crystal solution (the pot life is short), there is a possibility that the remaining liquid crystal is solidified, and there is a problem that the burning life is short.

Japanese Patent Application Laid-Open No. Hei 8-29797 discloses that
A method is described in which a liquid crystal material and a photocurable material are mixed, the temperature is raised to a temperature higher than the phase transition temperature of the liquid crystal, and phase separation is performed. However, this method has problems that bistable is not obtained and that it takes time for the resin to cure.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and can provide a liquid crystal display device having high alignment stability and image sticking durability of a liquid crystal material by a simple process. Easy recovery of liquid crystal solution,
It is another object of the present invention to provide a method for manufacturing a liquid crystal display element that does not change the phase transition temperature of a liquid crystal material.

[0012]

According to the present invention, a ferroelectric liquid crystal material and a thermoplastic resin are sandwiched between a pair of substrates with electrodes separated from each other. In a method for manufacturing a liquid crystal display element, a liquid crystal cell is formed by sandwiching a ferroelectric liquid crystal material and a thermoplastic resin having a glass transition temperature (Tg) lower than its smectic phase transition temperature between a pair of substrates with electrodes. Heating the liquid crystal cell to the isotropic transition temperature of the ferroelectric liquid crystal material;
A step of cooling the heated liquid crystal cell below the glass transition temperature (Tg) of the thermoplastic resin, and applying a shearing force while applying an electric field as needed between the substrates of the cooled liquid crystal cell; While aligning the ferroelectric liquid crystal material,
Heat the liquid crystal cell to the glass transition temperature of the thermoplastic resin,
And fusing and fixing a pair of substrates with the thermoplastic resin.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method for manufacturing a liquid crystal display device according to the present invention will be specifically described below. In the method for manufacturing a liquid crystal display element of the present invention, a liquid crystal cell is formed by sandwiching a ferroelectric liquid crystal material and a thermoplastic resin having a glass transition temperature (Tg) lower than its smectic phase transition temperature between a pair of substrates with electrodes. Forming and heating the liquid crystal cell to the isotropic transition of the liquid crystal to further promote the phase separation state of the thermoplastic resin (phase separation state promotion step); and forming the heated liquid crystal cell into a thermoplastic resin glass. A step of cooling below the transition temperature (Tg) (cooling step), and in the state after the phase separation, applying a shearing force while applying an electric field between a pair of substrates of the liquid crystal cell to align the liquid crystal. At the same time, the liquid crystal cell is heated to around the glass transition temperature of the thermoplastic resin, and the pair of substrates is fused and fixed with the thermoplastic resin to stabilize the orientation of the liquid crystal (alignment and fusion fixing step). Great classification That.

1. Phase separation state promoting step As a method of forming a liquid crystal cell by sandwiching a ferroelectric liquid crystal material between a pair of substrates, for example, an injection method, a coating lamination method, and the like can be given. Here, when a long plastic substrate is used, coating and lamination can be efficiently manufactured by the following steps. (1) Film-forming step A solution (concentration: 5 to 60% by weight) obtained by dissolving a ferroelectric liquid crystal material and a thermoplastic resin in an organic solvent is applied by a bar coater method.
Apply to one substrate using direct gravure roll method, microgravure method, spray method printing method, etc.
A film can be formed by evaporating the solvent. The thickness is usually 0.5 to 10 μm, preferably 1 to
It is preferable to set the thickness in a range of about 4 μm.

(2) Laminating Step One of the substrates obtained above and the opposing substrate are laminated by pressing with a roll to form a liquid crystal cell. Here, the roll to be pressed may be heated.

(3) Heating Step of Liquid Crystal Cell The liquid crystal cell obtained by the laminating step is heated to a temperature higher than the isotropic transition point of the liquid crystal material to promote the phase separation state of the thermoplastic resin. The heating speed of the heating is preferably about 1 to 10 ° C./minute, and the heating time requires time until the liquid crystal completely undergoes isotropic transition.

2. Cooling step After that, the temperature is gradually cooled to around room temperature. The slow cooling speed is 0.
The temperature is preferably about 1 ° C. to 5 ° C./min. By performing the heating and the slow cooling, the phase separation state of the thermoplastic resin is further promoted. When a long plastic substrate is used, application of a liquid crystal material to one substrate and lamination of a counter substrate can be performed continuously, which is preferable in terms of productivity.

3. Alignment Step and Fusion Fixing Step (1) Alignment Step of Liquid Crystal Material It is preferable to perform uniaxial horizontal alignment treatment such that the normal of the smectic layer of the ferroelectric liquid crystal material is in the longitudinal direction of the liquid crystal display element. The orientation treatment method is not particularly limited, and a rubbing method, an oblique deposition method, a shearing method, or an orientation method by bending deformation can be used. In particular, when a plastic substrate is used, it is preferable to use an orientation method based on bending deformation and a bending orientation method while applying a voltage.

The orientation by the bending deformation can be performed by using various devices and methods. Usually, a method of performing the bending deformation while moving the substrate using at least one free rotating roller, preferably A method of performing bending deformation while continuously moving between at least two free rotating rollers can be suitably used.

The degree of bending of the substrate in the bending deformation processing is preferably set to a degree expressed by a radius of curvature, usually in the range of 5 to 1000 mm, preferably 10 to 500 mm. If the radius of curvature is less than 10 mm, the substrate may be damaged, or the electrode of the fine pattern may be broken. On the other hand, if it exceeds 500 mm, a sufficient shear stress is not applied to the liquid crystal material portion, and a good alignment state is obtained. There may not be. Further, in the orientation method based on bending deformation while applying a voltage, the applied voltage may be either AC or DC, and is applied continuously or intermittently. The preferred electric field strength is 0.1 to 150 MV / m, particularly preferably 5 to MV / m.
150 MV / m. In this case, the electric field strength is 0.1 MV
/ M, the orientation becomes insufficient, and conversely 150 MV
/ M causes dielectric breakdown of the liquid crystal cell. Further, the thermoplastic resin that has been phase-separated by the shearing force during the bending orientation process and fused between the substrates in a columnar shape is divided as if the column was broken.

(2) Fusion fixing step In this step, the thermoplastic resin separated by the liquid crystal alignment is fused again in a columnar manner between a pair of substrates, whereby the alignment of the liquid crystal material is broken by physical stress applied to the substrates. This is a step aimed at preventing the above. The liquid crystal cell after the alignment is heated to a temperature near the softening point of the thermoplastic resin or Tg.
The heating speed of heating is preferably about 1 to 10 ° C./min.
Further, the heating time requires time until the thermoplastic resin is fused between the pair of substrates. Then, it is gradually cooled to around room temperature. The slow cooling speed is preferably about 0.1 ° C. to 5 ° C./min. By performing the heating and the slow cooling, the columns (about 10 to 200 μm in diameter) of the thermoplastic resin are re-formed between the substrates,
A pair of substrates are fixed. In addition, at this time, when the orientation of the liquid crystal material is disturbed due to distortion of the substrate due to heating,
An electric field may be applied to prevent this. The electric field is
AC or DC may be used, and the applied electric field is 0.1 to 1
It is 50 MV / m, particularly preferably 5 to 150 MV / m.

4. Components Hereinafter, components used in the method for manufacturing a liquid crystal display element of the present invention will be specifically described. (1) Ferroelectric Liquid Crystal Material The ferroelectric liquid crystal material used in the present invention is not particularly limited as long as it is a low molecular or high molecular ferroelectric liquid crystal material showing a chiral smectic C phase (SmC *). There are ferroelectric low-molecular liquid crystal materials, ferroelectric high-molecular liquid crystal materials, and mixtures thereof. Examples of the ferroelectric low-molecular liquid crystal material include one or more ferroelectric low-molecular liquid crystal materials, and a mixture of one or more ferroelectric low-molecular liquid crystal materials and another low-molecular liquid crystal material. And a ferroelectric low-molecular liquid crystal material. Examples of the ferroelectric polymer liquid crystal material include one or more ferroelectric polymer liquid crystal materials, one or more ferroelectric low-molecular liquid crystal materials and one or more ferroelectric high Ferroelectric polymer liquid crystal materials composed of molecular liquid crystal materials, ferroelectric polymer liquid crystal materials composed of one or more ferroelectric low molecular liquid crystal materials and one or more other polymer liquid crystal materials, etc. Can be mentioned. That is, as the ferroelectric polymer liquid crystal material, a ferroelectric polymer liquid crystal material (homopolymer or copolymer or a mixture thereof) in which polymer molecules themselves exhibit ferroelectric liquid crystal properties, a ferroelectric polymer liquid crystal material Mixture with other polymer liquid crystal materials and / or ordinary polymers, mixture of ferroelectric polymer liquid crystal material and ferroelectric low molecular weight liquid crystal material, ferroelectric polymer liquid crystal material and ferroelectric low molecular weight liquid crystal Such as a mixture of a material with a high-molecular liquid crystal material and / or a normal polymer, or a mixture of these with a normal low-molecular liquid crystal material,
All polymeric liquid crystal materials exhibiting ferroelectricity can be used. Among the ferroelectric polymer liquid crystal materials, for example, a side chain type ferroelectric polymer liquid crystal material can be suitably used, and particularly, a side chain type ferroelectric polymer liquid crystal material having a chiral smectic C phase is used. It can be suitably used. Examples of the ferroelectric liquid crystal polymer include an acrylate main chain liquid crystal polymer, a methacrylate main chain liquid crystal polymer, a chloroacrylate main chain liquid crystal polymer, an oxirane main chain liquid crystal polymer, a siloxane main chain liquid crystal polymer, and a siloxane-olefin main liquid crystal. It includes a chain liquid crystal polymer and an ester main chain liquid crystal polymer.

[0023]

Embedded image

[0024]

Embedded image

[0025]

Embedded image

[0026]

Embedded image

The repeating unit of the ferroelectric liquid crystal polymer may have a side chain skeleton replaced with a biphenyl skeleton, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, or a phenyl 4-phenylbenzoate skeleton. Is a pyrimidine ring, a pyridine ring, a pyridazine ring, a pyrazine ring, a tetrazine ring,
It may be substituted with a cyclohexane ring, a dioxane ring, a dioxaborinane ring, or may be substituted with a halogen group such as fluorine or hydrochloric acid or a cyano group, a 1-methylalkyl group, a 2-fluoroalkyl group, a 2-chloroalkyl group,
2-chloro-3-methylalkyl group, 2-trifluoromethylalkyl group, 1-alkoxycarbonylethyl group, 2-alkoxy-1-methylethyl group, 2-alkoxypropyl group, 2-chloro-1-methylalkyl group ,
It may be replaced by an optically active group such as a 2-alkoxycarbonyl-1-trifluoromethylpropyl group, and the length of the spacer may vary within a range of 2 to 30 methylene chains. The ferroelectric liquid crystal polymer preferably has a number average molecular weight of 1,000 to 200,000. Examples of the ferroelectric low-molecular liquid crystal compound include Schiff base ferroelectric low-molecular liquid crystal compounds, azo and azoxy ferroelectric low-molecular liquid crystal compounds, biphenyl and aromatics ester ferroelectric low-molecular liquid crystal compounds, and halogens. And a ferroelectric low-molecular liquid crystal compound having a ring substituent such as a cyano group or a heterocyclic ring.

[0028]

Embedded image

[0029]

Embedded image

[0030]

Embedded image

[0031]

Embedded image

The above compound is a typical ferroelectric low molecular weight liquid crystal compound, and the above ferroelectric low molecular weight liquid crystal compound is not limited to these structural formulas. Further, in the present invention, other liquid crystal polymers, olefin resins, acrylic resins, methacrylic resins, polystyrene resins, polyester resins, It is also possible to use a mixture of resins such as a polycarbonate resin, a styrene-butadiene copolymer, and a vinylidene chloride-acrylonitrile copolymer. Further, a spacer may be mixed to keep the film thickness of the liquid crystal uniform. Further, a dichroic dye may be mixed in order to obtain a guest-host type liquid crystal display element. As dichroic dyes,
Dyes of anthraquinone type, azo type, diazo type, merocyanine type and the like can be mentioned.

(2) Thermoplastic resin Molecular weight, type and glass transition temperature Examples of the thermoplastic resin used in the present invention include those having the following molecular weight, type and glass transition temperature. a) Molecular weight The molecular weight is preferably in the range of 1,000 to 10,000. If it is less than 1,000, the solubility of the liquid crystal material increases, and the phase transition temperature of the liquid crystal material changes, which is not preferable. Further, since the force for fixing the pair of substrates is weak, it is difficult to stabilize the alignment of the liquid crystal material. Also, 10
If it exceeds 000, the glass transition temperature becomes high and exceeds the phase transition temperature of the liquid crystal material, which is not preferable. b) Type of resin Examples of the type of resin include polystyrene, polyisoprene,
Examples thereof include polymethyl methacrylate. c) Glass transition temperature It is necessary that the temperature is lower than the smectic phase transition temperature of the ferroelectric liquid crystal to be used. Preferably, the temperature is lower by about 5 to 10 ° C. than the smectic phase transition temperature in view of the alignment stability of the liquid crystal.

Composition Ratio The composition ratio of the thermoplastic resin to the whole liquid crystal composition is preferably 1 to 50% by weight. If it is less than 1% by weight, the orientation of the liquid crystal material cannot be stabilized. Also,
If it exceeds 50% by weight, the contrast is lowered and the display quality is lowered.

(3) Pair of Substrates The pair of substrates used in the present invention is not particularly limited, and various materials such as a glass substrate or a plastic substrate with a transparent electrode used for a liquid crystal display device can be used. Can be used. Usually, a substrate made of a plastic material having plasticity can be suitably used in terms of productivity, versatility, workability, and the like. Examples of the plastic material include a crystalline polymer such as uniaxially or biaxially stretched polyethylene terephthalate, an amorphous polymer such as polysulfone, polyether sulfone, and polyarylate;
Examples thereof include polyolefins such as polyethylene and polypropylene, and polyamides such as polycarbonate and nylon. Of these, uniaxially or biaxially stretched polyethylene terephthalate, polyether sulfone and the like are particularly preferred.

(4) Electrode The material for forming the liquid crystal driving electrode group (scanning electrode, signal electrode) formed on the substrate used in the present invention is not particularly limited as long as it is a conductive material. is not.
Specifically, for example, a transparent electrode such as indium oxide or an ITO (Indium Tin Oxide) film made of indium oxide and tin oxide can be used.

(5) Polarizing Plate In the present invention, a polarizing plate may be used if necessary. As this polarizing plate, an ordinary commercial product can be used. In the case of a guest-host type in which a dye is mixed in the liquid crystal composition, only one polarizing plate is required for display.

(6) Insulating Film In the present invention, an insulating film may be provided on the electrodes, if necessary, in order to prevent conduction between the electrodes of the pair of substrates. There is no particular limitation on this insulating film.

[0039]

EXAMPLES The present invention will be described more specifically with reference to the following examples.

1. Preparation of Coating Solution Ferroelectric high-molecular liquid crystal material, ferroelectric low-molecular liquid crystal material, SmC low-molecular liquid crystal material, polystyrene PSt (thermoplastic resin molecular weight Mw 36) shown in [Formula 9] to [Formula 13], respectively.
80 softening temperature 60 ° C.) at the following ratio (parts by weight) (isotropic transition temperature of liquid crystal composition 90 ° C.), and further, methyl ethyl ketone (MEK) was added thereto to obtain a liquid crystal composition solution having a concentration of 30% by weight. Produced. Ferroelectric polymer liquid crystal 1.5 g Ferroelectric low molecular liquid crystal 0.6 g SmC low molecular liquid crystal (I) 0.3 g 〃 (II) 0.3 g 〃 (III) 0.3 g Polystyrene 0.3 g .2 μm polytetrafluoroethylene (P
The solution was filtered through a TFE) membrane filter, and poured into a glass container containing a 1.9 μm silica spacer in advance to prepare a coating solution.

[0041]

Embedded image

[0042]

Embedded image

[0043]

Embedded image

[0044]

Embedded image

[0045]

Embedded image

2. Preparation of Device The above coating solution was applied to a polyethersulfone (PES) substrate with an ITO electrode (34 cm wide and 60 cm long) which had been coated with an insulating film on its surface and sufficiently dried. After evaporation of the solvent, the same type of PES substrate was bonded and laminated. The device thus prepared was placed in a constant temperature bath at 50 ° C., heated at an odor of 2 ° C./min, held at 90 ° C. for 10 minutes, and then heated at a rate of 1 ° C./min.
Cooled to ° C. By this operation, it was confirmed that the domain of polystyrene grew from 2 μm to 20 μm. Thereafter, while applying an electric field of AC 60 V and 10 Hz, a uniaxial horizontal alignment treatment was performed by applying a bending deformation in a certain direction using three rolls. The device manufactured for this purpose was evaluated for bistability under crossed Nicols and found to be very good, with M = 100%. However, the measurement result of the intensity of the orientation was t = 20 mm, and the orientation was easily broken by weak pressing with a finger. Then, in order to further improve the stability of orientation, the following operation was performed to fix the upper and lower substrates with polystyrene. 50 ° C
And heated at an odor of 1 ° C./min, kept at 60 ° C., a temperature at which polystyrene softens, for 10 minutes, and then gradually cooled to 50 ° C. at a rate of 1 ° C./min. During this operation, by applying an electric field of AC 4 V and 0.1 Hz, the fluctuation of the orientation due to heat could be prevented. Furthermore, when taking out from 50 ° C to room temperature, AC 75V, 60H
By applying an electric field of z, the in-plane uniformity of the orientation direction of the liquid crystal could be improved. When the bistability of the device thus obtained was evaluated, a good result of M = 98% was obtained. Moreover, the measurement result of the intensity of orientation is t = 14 mm
The orientation was not broken even if it was strongly pressed with a finger. In this way, a liquid crystal display element which was excellent in bistability and which did not break even when the orientation was pressed with a finger could be produced.

[Comparative Example] Preparation of Coating Solution Polystyrene PSt (thermoplastic resin Mw 10,000, softening point 96 ° C.) was mixed in the following ratio with the ferroelectric polymer liquid crystal, ferroelectric low molecular liquid crystal, and SmC low molecular liquid crystal used in Examples (liquid crystal composition). 90 ° C)
Methyl ethyl ketone (MEK) was added to these to prepare a liquid crystal composition solution having a concentration of 30% by weight. Ferroelectric polymer liquid crystal 1.5 g Ferroelectric low molecular liquid crystal 0.6 g SmC low molecular liquid crystal (I) 0.3 g 〃 (II) 0.3 g 〃 (III) 0.3 g Polystyrene 0.3 g .2 μm polytetrafluoroethylene (P
The solution was filtered through a TFE) membrane filter, and poured into a glass container containing a 1.9 μm silica spacer in advance to prepare a coating solution.

2. Preparation of Device The above coating solution was applied to a polyethersulfone (PES) substrate with an ITO electrode (34 cm in length and 60 cm in length) which had been previously coated with an insulating film and sufficiently dried. After evaporation of the solvent, the same type of PES substrate was bonded and laminated. The device thus prepared was placed in a constant temperature bath at 50 ° C., heated at an odor of 2 ° C./min, held at 90 ° C. for 10 minutes, and then heated at a rate of 1 ° C./min.
Cooled to ° C. In this operation, no growth of the polystyrene domain was observed, and promotion of phase separation could not be confirmed. Therefore, the heating temperature was set at 100 ° C., which exceeds the softening point of polystyrene of 96 ° C., and heating was performed for 10 minutes.
As a result, growth from 2 μm to about 8 μm could be confirmed. Thereafter, while applying an electric field of AC 60 V and 10 Hz, a uniaxial horizontal alignment treatment was performed by applying a bending deformation in a certain direction using three rolls. The device thus manufactured was evaluated for bistability under crossed Nicols and found to be very good, with M = 100%. However, the measurement result of the orientation strength was that the orientation was easily broken by weakly pressing the finger with t = 25 mm. So further,
An operation of fixing the upper and lower substrates with polystyrene was performed in order to increase the stability of the orientation as in the example. 5
Place in a thermostat at 0 ° C., heat at 1 ° C./min, hold at 96 ° C., the temperature at which polystyrene softens, for 10 minutes,
Thereafter, it was gradually cooled to 50 ° C. at a rate of 1 ° C./min. But,
Since the temperature reached by heating exceeded the isotropic transition point of the liquid crystal, the orientation of the liquid crystal was broken, and as a result, the liquid crystal display element could not be played. Further, in consideration of the phase transition temperature of the liquid crystal, the same operation was carried out at a heating ultimate temperature of 85 ° C. As a result, since the temperature attained by heating was lower than the softening point of polystyrene, fusion of polystyrene between the substrates did not occur, and the strength of orientation was unchanged at t = 25 mm. Therefore, when the substrate was pressed with a finger, the orientation was easily broken.

[0049]

As described above, according to the present invention, it is possible to provide a liquid crystal display device having high alignment stability and image sticking durability of a liquid crystal material by a simple process, and to easily recover a liquid crystal solution. A method for manufacturing a liquid crystal display element without changing the phase transition temperature of a liquid crystal material can be provided. This is because, in the present invention, since the liquid crystal material and the thermoplastic resin are phase-separated from the beginning of mixing, the thermoplastic resin phase easily grows as a core. That is, when the liquid crystal material and the thermoplastic resin are mixed, the thermoplastic resin once dissolves in the liquid crystal material, but is basically phase-separated, so that the thermoplastic resin precipitates in the subsequent processing and grows easily. .

Claims (1)

[Claims] 1. A method of manufacturing a liquid crystal display device comprising a ferroelectric liquid crystal material and a thermoplastic resin sandwiched between a pair of electrode-attached substrates in a state where they are separated from each other. A liquid crystal cell is formed by sandwiching a dielectric liquid crystal material and a thermoplastic resin having a glass transition temperature (Tg) lower than its smectic phase transition temperature, and heating the liquid crystal cell to the isotropic transition temperature of the ferroelectric liquid crystal material. And cooling the heated liquid crystal cell below the glass transition temperature (Tg) of the thermoplastic resin. While applying an electric field between the cooled liquid crystal cell substrates as necessary, Applying a force to orient the ferroelectric liquid crystal material, heating the liquid crystal cell to the glass transition temperature of the thermoplastic resin, and fusing and fixing a pair of substrates with the thermoplastic resin. Method.