JPH0968710A - Ferroelectric liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal display device which exhibits good shock resistance, min. value in a voltage-memory pulse width curve and good bistable switching. SOLUTION: This ferroelectric liquid crystal display device has a structure formed by holding a composite consisting of a ferroelectric liquid crystal material and high-polymer material between substrates 9 and 10 having at least electrode films 2a, 2b and oriented films 4a, 4b. The pretilt directions of the ferroelectric liquid crystal molecules at the boundary of both substrates 9 and 10 are the same and the ferroelectric liquid crystal maternal has a chevron layer structure. The bending direction of this chevron structure and the pretilt directions of the ferroelectric liquid crystal molecules at the boundary of both substrates are the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a ferroelectric liquid crystal. More specifically, the present invention relates to a display device using a composite composed of a ferroelectric liquid crystal and a polymer material.

[0002]

2. Description of the Related Art Ferroelectric liquid crystal displays normally utilize a liquid crystal phase called a chiral smectic C phase. In this liquid crystal phase, the liquid crystal molecules form a layered structure, and the liquid crystal molecules are aligned with respect to this layer. The liquid crystal molecules have a molecular arrangement having a spiral structure in the bulk state, but in a liquid crystal cell thinner than the spiral pitch, the spiral is unwound, and a bistable molecular arrangement as shown in FIG. 1 is taken. Ferroelectric liquid crystal has spontaneous polarization (Ps) in a direction perpendicular to the layer, and when an electric field is applied in that direction, liquid crystal molecules are rearranged so that the spontaneous polarization is aligned in the direction of the electric field. By combining this with a pair of polarizing plates (polarizer and analyzer), bright and dark display can be performed (NAClark and S.
T. Lagerwall, Appl. Phys. Lett., 36, 899 (1980)).

[0003] The rearrangement of the ferroelectric liquid crystal is caused by a direct interaction between an electric field and spontaneous polarization of liquid crystal molecules.
High-speed response of liquid crystal molecules on the order of microseconds becomes possible. In addition, the liquid crystal molecule has a property of keeping a tilted state with respect to the layer before the electric field is cut off even after the electric field is cut off. This is the so-called memory property. By utilizing the characteristics of high-speed response and memory property, information can be displayed at high speed for each scanning line, so that it is possible to manufacture a simple matrix type display having a large display capacity.

FIG. 2 shows the basic structure of the ferroelectric liquid crystal display 11. ITO (Indium Tin 0xide) electrode film 2a,
A substrate 9 including a glass substrate 1a having an insulating film 3a and an alignment film 4a and a polarizing plate 12a, and ITO (Indium Tin 0x).
ide) electrode substrate 2b, insulating film 3b and alignment film 4b, and a substrate 10 composed of a glass plate 1b and a polarizing plate 12b. The cell thickness is about 5 μm, and the cells are bonded together via the seal member 6. A liquid crystal material 7 is sealed between the substrates 9 and 10. A polymer film such as polyimide is usually used for the alignment films 4a and 4b, and the surfaces thereof are rubbed. A drive circuit is connected to the electrode films 2a and 2b.

A ferroelectric liquid crystal display has the same structure as a conventional simple matrix type liquid crystal display except that the cell thickness is as thin as about 1.5 μm and the liquid crystal is a ferroelectric liquid crystal.

A major problem of the ferroelectric liquid crystal display device is that
It is difficult to obtain a stable display device because it is vulnerable to shock and pressure (N. Wakita et al., Abstr. 4th Int.
ernational Conference on Ferroelectric Liquid Crys
tals, 367 (l993)). In general, liquid crystal molecules in a liquid crystal cell easily flow due to pressure or shock. The initial molecular alignment of the liquid crystal molecules is disturbed by the flow of the liquid crystal molecules. The reason why the ferroelectric liquid crystal display device is weak against shock and pressure is that the once disturbed alignment of the ferroelectric liquid crystal molecules does not spontaneously return to the original alignment. Therefore, in order to improve the shock resistance of the ferroelectric liquid crystal element, it is necessary to prevent the liquid crystal molecules from flowing in the liquid crystal cell due to the shock.

The following method has been proposed as a method for preventing the flow of liquid crystal molecules due to shock. One method is to use a polymer-dispersed ferroelectric liquid crystal material (H. Molsen, R. Bardon, HSKitzerow, The 13th in
ternational disp1ay reserch conference, Proc of Eu
ro Display '93, Strasbourg, 1993, p.113).

Using this method, a material or device satisfying the requirements required for a practical display such as response speed, contrast and usable temperature range has not yet been produced.

As another method, a method of adding a polymer liquid crystal to a ferroelectric liquid crystal has been proposed (G. Lester, H. Cole.
s, A. Murayama, Ferroelectrics, 148, 389 (1993)). In this method, there is a problem that the orientation of the ferroelectric liquid crystal molecules is lowered and the response speed of the liquid crystal molecules is slowed by the addition of the polymer liquid crystal.

In recent years, a method has been proposed in which a polymer formed by photopolymerization and a ferroelectric liquid crystal are phase-separated by irradiating a mixture of a ferroelectric liquid crystal and a photocurable prepolymer with ultraviolet rays. (Fujikake et al. Proceedings of the 41st Joint Lecture on Applied Physics No.3, ll20 (l994)). This method
Since the formed polymer is fine, it has an advantage that light scattering does not occur. Further, neither improvement nor shock resistance is disclosed or suggested in the above document. further,
The mixture of the ferroelectric liquid crystal and the photo-curable prepolymer is heated to the nematic phase (75 ° C.) and aligned with the polyimide film to cause phase separation between the polymer and the ferroelectric liquid crystal. Is fixed with a polymer without taking the original smectic C phase. As a result, there arises a problem that sufficient molecular orientation of ferroelectric liquid crystal molecules cannot be obtained.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and provides good ferroelectric liquid crystal molecule alignment, good display characteristics, and shock resistance. It is an object of the present invention to provide the ferroelectric liquid crystal display device which is satisfied at the same time.

[0012]

In order to solve the above problems, the inventors of the present invention have earnestly studied a method for improving shock resistance while maintaining the alignment state of a ferroelectric liquid crystal, and as a result, a liquid crystal material has been obtained. And a photopolymerizable monomer material in a mixture, a specific ferroelectric liquid crystal alignment state is formed and then the monomer is photopolymerized, or an isotropic mixture of the liquid crystal material and the photopolymerizable monomer material is formed. After that, the monomer is photopolymerized and then cooled to a temperature at which the liquid crystal material has a specific alignment state, so that the flow state of the liquid crystal molecules is suppressed while maintaining the alignment state of the ferroelectric liquid crystal, and the resistance of the liquid crystal display device is improved. It has been found that shock resistance can be improved. Further, when the ferroelectric liquid crystal material has a specific structure and the ferroelectric liquid crystal molecules having a negative dielectric anisotropy have a specific alignment state, high writing speed, high contrast, wide operating temperature range, etc. It has been found that a ferroelectric liquid crystal display device excellent in respect of the above can be obtained.

That is, the present invention has a structure in which a composite of a ferroelectric liquid crystal material and a polymer material is sandwiched between substrates having at least an electrode film and an alignment film, and the substrate and the ferroelectric The directions of pretilt of the ferroelectric liquid crystal molecules at the interface with the liquid crystal material are the same, the ferroelectric liquid crystal material has a chevron layer structure, and the bending direction of the chevron layer structure and the ferroelectricity at the interface. The pretilt direction of the liquid crystal molecules is the same. Thereby, the above object is achieved.

In a preferred embodiment of the present invention, the alignment film is an organic polymer film, and a pretilt angle is given by rubbing.

In a preferred embodiment of the present invention, the ferroelectric liquid crystal material has a negative dielectric anisotropy and exhibits a local minimum value in the voltage-memory pulse width curve.

In a preferred embodiment of the present invention, the content of the polymer material is 10% by weight or less based on the total weight of the composite.

The present invention also includes the following steps: a step of bonding substrates having at least an electrode film and an alignment film; a step of sandwiching a mixture of a ferroelectric liquid crystal material and a photopolymerizable monomer material between the substrates; Heating the mixture to a temperature at which the mixture becomes an isotropic liquid, and then cooling the mixture to a temperature at which the ferroelectric liquid crystal material in the mixture exhibits a chiral smectic C phase; and in the mixture A method for producing a ferroelectric liquid crystal display device, comprising the step of photopolymerizing a photopolymerizable monomer material in the mixture to polymerize it in a temperature range in which the ferroelectric liquid crystal material exhibits a chiral smectic C phase. . Thereby, the above object is achieved.

In a preferred embodiment of the present invention, at a temperature at which the ferroelectric liquid crystal material in the mixture exhibits a chiral smectic C phase, the ferroelectric liquid crystal molecules at the interface between the substrate and the ferroelectric liquid crystal material are The pretilt directions are the same, the ferroelectric liquid crystal material has a chevron layer structure, and the bending direction of the chevron layer structure is the same as the pretilt direction of the ferroelectric liquid crystal molecules at the interface. .

Furthermore, the present invention provides the following steps: a step of bonding substrates having at least an electrode film and an alignment film;
Sandwiching a mixture of a ferroelectric liquid crystal material and a photopolymerizable monomer material between the substrates; heating the mixture to a temperature at which the mixture becomes an isotropic liquid, and then exposing the mixture to light at the temperature. A step of photopolymerizing a polymerizable monomer material to polymerize it; a temperature at which a ferroelectric liquid crystal material in the composite exhibits a chiral smectic C phase when a composite of the ferroelectric liquid crystal material and the generated polymer is formed. The method of manufacturing a ferroelectric liquid crystal display device, which includes the step of:

In a preferred embodiment of the present invention, the alignment film in the above manufacturing method is an organic polymer film, and a pretilt angle is given by rubbing.

In a preferred embodiment of the present invention, the ferroelectric liquid crystal material in the above manufacturing method has a negative dielectric anisotropy, and exhibits a minimum value in the voltage-memory pulse width curve.

In a preferred embodiment of the present invention, the content of the photopolymerizable monomer material in the above production method is
It is not more than 10% by weight of the total weight of the mixture.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

As used herein, the term "composite" includes a ferroelectric liquid crystal material and a polymer formed by photopolymerization. The polymer may be a linear polymer or a crosslinked polymer, or may be a mixture thereof. Further, the composite may contain an unreacted material of a photopolymerizable monomer that is a raw material of the polymer.

The polymer in the composite has a network structure, and this network structure stabilizes the orientation of the ferroelectric liquid crystal molecules. When the polymer is a linear polymer, a physical network structure is formed by the entanglement of polymer chains. Further, when the polymer is a cross-linked polymer, a network structure is formed by a chemical bond.

(Preferable Alignment State of Liquid Crystal Molecules) When a ferroelectric liquid crystal display device was first proposed, the ferroelectric liquid crystal phase had a "bookshelf layer structure" in a direction perpendicular to the substrate (FIG. 3 (a)).
Was considered to be taking. However, subsequent studies have revealed that the ordinary ferroelectric liquid crystal phase has a “chevron layer structure” as shown in FIG.

In the ferroelectric liquid crystal display device in which the upper and lower substrates are provided with pretilt angles in the same direction, the inventors of the present invention have four alignment states of liquid crystal molecules due to the difference in the molecular arrangement of the liquid crystal molecules in the chevron layer structure. (C1U, C1T, C
2U, C2T). C1 and C2 are defined based on the pretilt direction of the ferroelectric liquid crystal molecules and the bending direction of the chevron layer structure, respectively. C1 is the case where the pretilt direction of the ferroelectric liquid crystal molecules is opposite to the bending direction of the chevron layer structure. C2 is the case where the pretilt direction of the ferroelectric liquid crystal molecules and the bending direction of the chevron layer structure are the same. Of these four orientation states, C1U which is practically important
A molecular orientation model of (C1-uniform) orientation and C2U (C2-uniform) orientation is shown in FIG. Figure 4 (a)
Shows a view of the liquid crystal display element as seen from a cross section. The elliptical shape in FIG. 4 (a) is a liquid crystal molecule having a pretilt angle θp, C
1 and C2 indicate C1U and C2U orientations, respectively. FIG. 4 (b) shows more detailed molecular orientations of the C1U orientation and the C2U orientation. FIG. 4C shows a view of a portion corresponding to the liquid crystal layer shown in FIG. 4A as seen from a direction perpendicular to the substrate.

When the dielectric anisotropy of the ferroelectric liquid crystal material is positive or near 0, a large fluctuation occurs in the liquid crystal molecules due to the bias voltage in the C2U orientation. Therefore, in this case, a liquid crystal display device having high contrast cannot be obtained. However, when the ferroelectric liquid crystal material has a negative dielectric anisotropy (Δε <0), this liquid crystal material has a peculiar τ-Vmin characteristic (where τ is a response speed and V is an applied voltage). Show. Then, if this characteristic is used, C is generated by the AC stabilization effect.
Even in the 2U orientation, the liquid crystal display device can have high contrast. The AC stabilization effect means that in a normal ferroelectric liquid crystal material, the response speed (τ) of the liquid crystal material monotonically increases as the voltage (V) is increased, whereas the ferroelectric liquid crystal material When the dielectric anisotropy is negative and the spontaneous polarization is not so large, the response speed (τ) exhibits a minimum value (τ-Vmin) with respect to a certain voltage (V). This is because the effect of dielectric anisotropy increases as the effective value of voltage increases.

Usually, the C1 orientation appears on the high temperature side, and the C2 orientation becomes more stable as the temperature decreases. In addition, the C1U orientation is changed to the C2 orientation or the C2 orientation by driving the liquid crystal display device.
Easy to change to 1T orientation. Therefore, since the C1 orientation is unstable with respect to temperature change, the C2U orientation is an orientation state that is more advantageous for ensuring a wide operating temperature range of the liquid crystal display device. Further, comparing the response speeds of the liquid crystal material in the C2U orientation and the C1U orientation, the response speed of the liquid crystal material in the C2U orientation is faster and the memory effect is larger.

Therefore, the τ-Vmin mode using the C2U orientation of the ferroelectric liquid crystal material having a negative dielectric anisotropy is that writing can be performed at high speed in a liquid crystal display device, high contrast can be obtained, and wide operation. It is preferable in that a temperature range can be obtained.

In order to obtain a uniform C2U orientation, it is necessary to impart a pretilt angle to the substrate. The pretilt angle is usually 0 to 20 °, preferably 3 to 8
A moderate pretilt angle of ° is preferred.

(Orientation control method) As a method of imparting a pretilt angle to a substrate, a rubbing method of rubbing a polymer material or an inorganic material on a substrate for forming a liquid crystal cell and rubbing it with a fiber, or a compound having a low surface tension is used. Vertical alignment method for coating, Si
An oblique alignment method using oblique vapor deposition of O ₂ or the like, a horizontal alignment film not subjected to rubbing treatment, or a non-treated substrate (a substrate having a transparent electrode provided on the substrate) may be used. In the present invention, the rubbing method is preferred. In particular, C2 alignment of the liquid crystal material is likely to occur when the alignment film rubbed to achieve a medium pretilt angle is parallel rubbed (a method of manufacturing by laminating the alignment films so that the rubbing directions are substantially parallel to each other). It is preferable in terms. As the alignment film,
Organic polymer membranes are preferred. As the polymer for forming the film, polyimide, polyvinyl alcohol, etc. may be used. For example, as the polyimide, AL1054,
A medium pretilt angle can be realized by using AL3356, AL5357 (all of which are made of Japan Synthetic Rubber) or the like.

(Preferable Method of Manufacturing Ferroelectric Liquid Crystal Display Device) As a preferable method of manufacturing the ferroelectric liquid crystal display device of the present invention, first, a substrate having at least a transparent electrode and a parallel-rubbed alignment film is formed with a spacer. It is installed through a gap to form a cell. Next, a mixture of the ferroelectric liquid crystal material and the photopolymerizable monomer material is injected. Then, after heating to a temperature at which the mixture becomes an isotropic liquid,
The mixture is cooled to a temperature at which the liquid crystal material exhibits a chiral smectic C phase, and then the photopolymerizable monomer material is photopolymerized in a temperature range in which the liquid crystal material exhibits a chiral smectic C phase, for example, by irradiating the cell with UV light. To form a polymer, or after heating the mixture to a temperature at which it becomes an isotropic liquid, the photopolymerizable monomer material is photopolymerized at this temperature, and then the ferroelectric liquid crystal material and the produced polymer are mixed. The ferroelectric liquid crystal display liquid crystal display device of the present invention can be suitably manufactured also by the step of cooling the composite consisting of the above to a temperature at which the ferroelectric liquid crystal material in the composite exhibits the chiral smectic C phase. Preferably, the mixture is cooled to a temperature at which a proper alignment state of liquid crystal molecules is formed, and then photopolymerization is performed in that state. In this case, since the alignment state of the liquid crystal molecules is less likely to be disturbed, a composite of the liquid crystal material and the polymer material having an appropriate alignment state can be obtained.

The cell thickness is 1.0 μm to 2.0.
μm is preferred.

The time for photopolymerizing the photopolymerizable monomer material is usually 1 to 20 minutes.

(Ferroelectric Liquid Crystal Material) Ferroelectric liquid crystal materials used in the present invention include SCE8 (manufactured by Hoechst), ZLI-4237-000 (manufactured by Merck), ZLI-5014-000 (manufactured by Merck). ) And CS-1014 (manufactured by Chisso Corporation). These liquid crystal materials may be mixed and used. As described above, a ferroelectric material having a negative dielectric anisotropy is preferable because the advantage of the τ-Vmin mode using the C2U orientation can be utilized. Since the characteristics of the composite according to the present invention depend on the combination of the ferroelectric liquid crystal material and the polymer material (photopolymerizable monomer material) forming the composite, the desired dielectric constant can be set according to the required characteristics. Alternatively, a ferroelectric liquid crystal material having a magnitude of spontaneous polarization can be appropriately selected.

(Photopolymerizable Monomer) As the photopolymerizable monomer material used in the present invention, for example, acrylic acid or acrylate having a C3 or longer long-chain alkyl group or aromatic group can be used. Examples of these are isobutyl acrylate, stearyl acrylate, lauryl acrylate, isoamyl acrylate,
n-butyl acrylate, tridecyl acrylate, 2
-Ethylhexyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-phenoxyethyl acrylate; these acrylates replaced by methacrylates; and halides of these monomers (especially chlorinated or fluorinated monomers), for example 2,2 , 3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,4,4,4-hexachlorobutyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2 3,3-tetrachloropropyl methacrylate, perfluorooctylethyl methacrylate, perchlorooctylethyl methacrylate, perfluorooctylethyl acrylate,
Mention may be made of perchlorooctylethyl acrylate. These monomers may be used alone or in combination of two or more.

The content of the photopolymerizable monomer material in the mixture of the ferroelectric liquid crystal material and the photopolymerizable monomer material is
1-10% by weight, in particular 2-5, relative to the total weight of the mixture
% By weight is preferred. The concentration of the photopolymerizable monomer material is 10
When the content exceeds the weight%, the force that regulates the movement of liquid crystal molecules becomes too strong and the response speed of the liquid crystal display device becomes slow. In addition, the alignment state of the liquid crystal material deteriorates. If it is less than 1% by weight, the effect of shock resistance cannot be obtained. Further, in order to increase the physical strength of the polymer, a polyfunctional monomer having two or more functional groups may be copolymerized. Examples of polyfunctional monomers include bisphenol A dimethacrylate, bisphenol A diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, Tetramethylolmethane tetraacrylate may be used.

If necessary, a chlorinated or fluorinated polymer or oligomer may be mixed with the above-mentioned monomer before use. Further, a monomer having a structure similar to that of the ferroelectric liquid crystal material may be copolymerized.

(Photopolymerization Initiator) The photopolymerizable monomer material of the present invention may contain a photopolymerization initiator, if desired. Examples of the photopolymerization initiator include Irgacure 651, Irgacure 184
(Manufactured by Ciba Geigy), and Darocure 1137 (manufactured by Merck). The photopolymerization initiator is preferably added in an amount of 0 to 1% by weight based on the total weight of the mixture of the liquid crystal material and the photopolymerizable monomer material composition, if necessary. If it is more than 1% by weight, the polymerization rate becomes too fast,
And promotes side reactions.

By using a composite of a ferroelectric liquid crystal material having a C2U orientation and a polymer material in a liquid crystal display device, a ferroelectric liquid crystal display device exhibiting high-speed writing, high contrast and a wide operating temperature range can be obtained. To be

In a mixture of a ferroelectric liquid crystal material and a photopolymerizable monomer material, a specific ferroelectric liquid crystal alignment state is formed, and then the monomer is photopolymerized to obtain a good ferroelectric liquid crystal alignment. The state is obtained.

[0043]

【Example】

 (Example 1) On substrates 1a and 1b such as glass,
The ITO films 2a and 2b are formed respectively, and photolithography is performed.
Patterned in stripes by a technique such as chromatography
did. On top of each of these,₂Insulating film 3a
And 3b are laminated, and then the polyimide alignment films 4a and 4a are laminated.
And 4b (pre-tilt angle = 5 °) are applied and rubbed
Was. Next, rubbing the substrate la and the other substrate 1b
Attached with a cell thickness of 1.5 μm so that the directions are parallel.
During this period, the ferroelectric liquid crystal (FLC1,
The ferroelectric liquid crystal material of No. 9 shows negative dielectric anisotropy).
A mixture containing 0% by weight and 1.0% by weight of a photopolymerizable monomer material.
Compound A was injected between the substrates. This liquid crystal display device is 100
The mixture A is heated to ℃ to make it an isotropic liquid state.
Irradiate with ultraviolet rays (14 mW / cm²). This liquid crystal
The display element was cooled to room temperature and observed under a polarizing microscope.
By the way, it can be seen that the liquid crystal material has a good C2 orientation.
Was.

A drive experiment was conducted by applying the drive waveform shown in FIG. 5 to the ferroelectric liquid crystal. Set Vd = 5V, Vs
Pulse widths different in pulse width τ are applied, and the minimum pulse width for bistable switching is plotted in FIG. 6 (◯).
FIG. 6 shows that the liquid crystal display device of Example 1 exhibits a minimum value in the voltage-memory pulse width curve and exhibits good bistable switching.

In addition, a liquid crystal element was placed on a metal base using Shimadzu AGA-100A, and a cylindrical metal body having a diameter of 1 cm was lowered at 0.5 mm / min to apply a pressure to Example 1. When the shock resistance of the liquid crystal element was evaluated, the liquid crystal element showed 0.6 to 1.3 kgf / c.
It showed a good shock resistance of m ² .

[0046]

[Table 1]

(Example 2) Example 2 except that the mixture A of Example 1 was changed to a mixture B containing 97.0% by weight of a ferroelectric liquid crystal (FLC1) and 3.0% by weight of a photopolymerizable monomer material. A ferroelectric liquid crystal display device was prepared and evaluated in the same manner as in 1. FIG. 6 shows the minimum pulse width for bistable switching with respect to Vs (■). FIG. 6 shows that the liquid crystal display device of Example 2 exhibits a minimum value in the voltage-memory pulse width curve and exhibits good bistable switching.

The liquid crystal display device of the second embodiment has a 1.9.
It showed a good shock resistance of ˜2.5 kgf / cm ² .

Comparative Example 1 A ferroelectric liquid crystal display device was manufactured in the same manner as in Example 1 except that the photopolymerizable monomer was not used. However, no light irradiation was performed. 6 and 7 show the minimum pulse width for bistable switching with respect to Vs (●). This liquid crystal display also showed a C2 orientation at room temperature and a minimum value in the voltage-memory pulse width curve, but the shock resistance was poor at 0.6 kgf / cm ² .

Example 3 Mixture A in Example 1
Is made into an isotropic liquid state, and ultraviolet rays are irradiated in this state. After making the mixture A into an isotropic liquid state, the mixture is cooled to room temperature, the liquid crystal material is aligned in C2, and up-down is aligned. A ferroelectric liquid crystal display device was prepared and evaluated in the same manner as in Example 1 except that irradiation with ultraviolet rays was changed in this state.

FIG. 7 shows the minimum pulse width for bistable switching with respect to Vs (◯). FIG. 7 shows that the liquid crystal display device of Example 3 exhibits a minimum value in the voltage-memory pulse width curve and exhibits good bistable switching.

In addition, the liquid crystal display device of the third embodiment has 1.3 to
It showed a good shock resistance of 1.9 kgf / cm ² .

(Example 4) In Example 2, the mixture B was used.
Is made into an isotropic liquid state, and ultraviolet rays are irradiated in this state. After making the mixture B into an isotropic liquid state, the mixture B is cooled to room temperature to align the liquid crystal material with C2 orientation, and after aligning up-down, A ferroelectric liquid crystal display device was prepared and evaluated in the same manner as in Example 2 except that irradiation with ultraviolet rays was changed in this state.

FIG. 7 shows the minimum pulse width for bistable switching with respect to Vs (■). FIG. 7 shows that the liquid crystal display device of Example 4 exhibits a minimum value in the voltage-memory pulse width curve and exhibits good bistable switching.

In addition, the liquid crystal display device of the fourth embodiment is 1.9-.
It showed a good shock resistance of 2.0 kgf / cm ² .

[0056]

According to the present invention, the shock resistance is good, and the voltage-memory pulse width curve exhibits a minimum value.
Then, a ferroelectric liquid crystal display device exhibiting good bistable switching can be obtained.

Further, in a mixture of a ferroelectric liquid crystal material and a photopolymerizable monomer material, a specific ferroelectric liquid crystal alignment state is formed, and then the monomer is photopolymerized to obtain a good ferroelectric liquid crystal. It exhibits good shock resistance while maintaining the orientation state of.

[Brief description of drawings]

FIG. 1 is a switching schematic diagram showing the operating principle of a ferroelectric liquid crystal.

FIG. 2 is a structure (cross-sectional view) of a ferroelectric liquid crystal display element.

FIG. 3 is a schematic view of a layer structure of liquid crystal.

FIG. 4 is a schematic diagram of a molecular orientation model.

FIG. 5 is an explanatory diagram of drive waveforms used in the example of the present invention.

FIG. 6 is a schematic diagram of Examples 1-2 and Comparative Example 1 of the present invention.
3 is a voltage-memory pulse width curve of the liquid crystal display device of FIG.

FIG. 7 shows Examples 3 to 4 of the present invention and Comparative Example 1
3 is a voltage-memory pulse width curve of the liquid crystal display device of FIG.

[Explanation of symbols]

 1a, 1b Glass substrate 2a, 2b Electrode film 3a, 3b Insulating film 4a, 4b Alignment film 6 Sealing member 7 Liquid crystal material 9, 10 Substrate 11 Ferroelectric liquid crystal display device 12a, 12b Polarizing plate

Front Page Continuation (72) Inventor, Paul Gas, England Oxford Oex 4 4 GF, Oxford Science Park, Edmond Halley Road, Sharp Laboratories of Europe, Limited

Claims (10)

[Claims] 1. A ferroelectric liquid crystal display device having a structure in which a composite of a ferroelectric liquid crystal material and a polymer material is sandwiched between a pair of substrates having at least an electrode film and an alignment film. The direction of the pretilt of the ferroelectric liquid crystal molecules at the interface between the substrate and the ferroelectric liquid crystal material is the same, the ferroelectric liquid crystal material has a chevron layer structure, and there is no bending of the chevron layer structure. A ferroelectric liquid crystal display device in which the direction and the pretilt direction of the ferroelectric liquid crystal molecules at the interface are the same. 2. The alignment film is an organic polymer film, and a pretilt angle is given by rubbing.
The ferroelectric liquid crystal display device according to claim 1. 3. The ferroelectric liquid crystal display device according to claim 1, wherein the ferroelectric liquid crystal material has a negative dielectric anisotropy and exhibits a minimum value in a voltage-memory pulse width curve. 4. The ferroelectric liquid crystal display device according to claim 1, wherein the content of the polymer material is 10% by weight or less based on the total weight of the composite. 5. A method of manufacturing a ferroelectric liquid crystal display device, which comprises the following steps: a step of bonding a substrate having at least an electrode film and an alignment film; a ferroelectric liquid crystal material and a photopolymerizable monomer between the substrates. Sandwiching the mixture with the material;
Heating the mixture to a temperature at which the mixture becomes an isotropic liquid, and then cooling the mixture to a temperature at which the ferroelectric liquid crystal material in the mixture exhibits a chiral smectic C phase; and in the mixture A step of photopolymerizing the photopolymerizable monomer material in the mixture to polymerize it in a temperature range in which the ferroelectric liquid crystal material exhibits a chiral smectic C phase;
The manufacturing method including. 6. The pretilt direction of the ferroelectric liquid crystal molecules at the interface between the substrate and the ferroelectric liquid crystal material is the same at a temperature at which the ferroelectric liquid crystal material in the mixture exhibits a chiral smectic C phase. The ferroelectric liquid crystal material has a chevron layer structure, and the bending direction of the chevron layer structure and the pretilt direction of the ferroelectric liquid crystal molecules at the interface are the same. Production method. 7. A method of manufacturing a ferroelectric liquid crystal display device, comprising the steps of: bonding a substrate having at least an electrode film and an alignment film; a ferroelectric liquid crystal material and a photopolymerizable monomer between the substrates. Sandwiching the mixture with the material;
Heating the mixture to a temperature at which the mixture becomes an isotropic liquid, and then photopolymerizing the photopolymerizable monomer material in the mixture at this temperature to polymerize; A ferroelectric liquid crystal material in the composite is a chiral smectic C, which is a composite of a liquid crystal material and a generated polymer.
Cooling to a temperature exhibiting a phase; 8. The alignment film is an organic polymer film, and a pretilt angle is given by rubbing.
The manufacturing method according to claim 5, 6 or 7. 9. The manufacturing method according to claim 5, 6, 7 or 8, wherein the ferroelectric liquid crystal material has a negative dielectric anisotropy and exhibits a minimum value in a voltage-memory pulse width curve. 10. The method according to claim 5, 6 or 7, wherein the content of the photopolymerizable monomer material is 10% by weight or less based on the total weight of the mixture.