JPH11190850A - Liquid crystal element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a uniform drive display over a whole display screen without influence by drive electrodes by forming the thickness of a partition part vertical to a substrate so that it becomes thinner as it goes away from a connection part of a liquid crystal drive voltage supply source. SOLUTION: As a material of a partition member 19, a photosensitive material such as acrylic photosensitive resin, etc., is desirable, which can be bonded to top and bottom substrates 11, 12, applicable in a state of the solution, and can also be patterned easily through a photo-lithographic process. The material film is cured by heating during a substrate sticking process. Moreover, a thickness of the partition member 19 vertical to the substrates is formed so as to be thinner as it goes away from a liquid crystal drive voltage supply source connected with the liquid crystal display element. And, in a rotary coating process of the material for forming the partition member 19, a temperature of the substrates is controlled by controlling the temperature of a substrate holder mounting the substrates thereon to form a temperature distribution on the substrates for forming the film thickness distribution on the material film to be formed on the substrates.

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 used for a liquid crystal display device or a liquid crystal optical shutter, and more particularly to a ferroelectric liquid crystal (FLC) or an antiferroelectric liquid crystal driven by utilizing the action of spontaneous polarization. The present invention relates to a liquid crystal element suitable for a liquid crystal element using a chiral smectic liquid crystal and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, various methods have been used for driving a liquid crystal element. Among them, a simple matrix method, which has a simple structure and is easy to enlarge a screen, is widely used.
As a liquid crystal in which the simple matrix method can be suitably used, there is a ferroelectric liquid crystal. A liquid crystal display device of a type that controls transmitted light in combination with a polarizing element using the refractive index anisotropy of the ferroelectric liquid crystal molecules is known as Clark and Lagerwal.
1) (JP-A-56-107216).
No. 4,367,942).

The ferroelectric liquid crystal generally has a chiral smectic C phase (SmC ^* ) or an H phase (SmH ^* ) in a specific temperature range, and in this state, the first phase responds to an applied electric field. It has one of an optically stable state and a second optically stable state, and maintains the state when no electric field is applied, that is, it has a bistable memory property. Shows a very fast response speed. Further, since it has excellent viewing angle characteristics, it is particularly suitable as a high-speed, high-definition, large-screen display element.

A liquid crystal exhibiting antiferroelectricity has been known as a technique for constructing a display element utilizing similar refractive index anisotropy and spontaneous polarization of liquid crystal molecules. This antiferroelectric liquid crystal generally has a chiral smectic CA phase (SmCA) in a specific temperature range. In this state, when there is no electric field, the average optical stable state is in the normal direction of the smectic layer. The average optical stable state is inclined from the layer normal direction by application. In addition, the antiferroelectric liquid crystal also performs switching by coupling of spontaneous polarization and electric field, so it shows a very fast response speed,
It is expected as a high-speed display element.

On the other hand, in order to obtain good switching characteristics in the ferroelectric liquid crystal, generally, the thickness of the liquid crystal layer must be
The helical pitch of liquid crystal molecules generated in the cholesteric phase, which is one of the liquid crystal phases, needs to be less than the pitch (generally, about 0.1 to several tens μm). Here, when the liquid crystal element is enlarged, a uniform liquid crystal layer thickness over the entire surface of the liquid crystal element, in other words, a gap between a pair of substrates sandwiching the liquid crystal (cell gap), is required to uniformly display the entire display area. ) Becomes more important. In general, a method of dispersing spacer particles having a uniform diameter in an element in order to make the distance between the substrates uniform and to enable a uniform display of the liquid crystal element is made.

On the other hand, as the size of the liquid crystal element becomes larger, it becomes difficult to maintain a uniform gap near the center of the liquid crystal element only by holding the upper and lower substrates around the liquid crystal element. Therefore, as a method for solving this, a particulate adhesive that adheres to the upper and lower substrates is sprayed so as not to widen the gap between the upper and lower substrates beyond the spacer particle diameter, and the particulate adhesive and the spacer particles are used together. Accordingly, a method of uniformly maintaining the gap is employed.

In recent years, a structure in which a dot-shaped or stripe-shaped partition member is provided outside a pixel for the purpose of improving orientation and impact resistance has been studied for practical use. The advantage of this structure is that by eliminating the particulate adhesive and spacer serving as nuclei of alignment defects from within the pixel, it is possible to obtain improved alignment and drive reliability.

Further, when this structure is applied to a ferroelectric liquid crystal or an antiferroelectric liquid crystal, the problem of shock resistance and the problem of void defects at the time of injection and at a low temperature can be simultaneously solved. Conventionally, the occurrence of void defects caused by the volume shrinkage of liquid crystal due to temperature change and the lack of impact resistance due to the low restoring force of the liquid crystal layer structure are a dilemma when focusing solely on the elasticity of the adhesive. It was a problem that occurred. However,
According to the study of the present inventors, when the layer direction of the partition member and the liquid crystal are made parallel, it is possible that the partition member has sufficient elasticity such that the liquid crystal does not flow while suppressing the generation of void defects by dividing the liquid crystal layer. It was confirmed that the problem in using the ferroelectric liquid crystal and the antiferroelectric liquid crystal was solved.

[0009]

In the case of realizing a large screen in the liquid crystal device having the above-mentioned structure,
As described above, the distance between the substrates can be maintained uniformly by using the particulate adhesive and spacer particles together.However, if the driving method is a simple matrix method, the delay in the liquid crystal element will be caused only by the transparent electrodes. As a result, the entire surface of the liquid crystal element cannot be driven under uniform driving conditions due to the influence of the delay.

Therefore, conventionally, an auxiliary metal electrode is arranged adjacent to the transparent electrode. However, when the auxiliary metal electrode is arranged in this manner, the transparent electrode and the auxiliary metal electrode (hereinafter, referred to as “drive electrode”) are formed. The drive electrodes generate heat due to the drive signals applied to the lines, and this heat generates a temperature gradient in the liquid crystal element in the direction in which the drive electrodes are arranged.

FIGS. 3 and 4 are diagrams schematically showing a temperature gradient on the display surface of the liquid crystal element generated by the heat generation of the drive electrode. In the figures, 31 is a liquid crystal element, and 32, 32a and 32b are information signal applying elements. A group 33 is a scanning signal applying element group.

As shown in FIG. 3, when the driving signal is supplied in two directions, the information signal applying element group 32 and the scanning signal applying element group 33 which are liquid crystal driving voltage supply sources are supplied along the arrows in the figure. The temperature increases as the distance increases, and decreases as the distance from the signal applying element group increases. In the case where the driving signal is supplied in three directions, as shown in FIG. 4, the temperature becomes higher as the position is closer to the scanning signal applying element group 33 and the temperature becomes lower as the distance increases.

As a result of the temperature gradient as described above, the minimum value (hereinafter referred to as "threshold") of the electric field intensity at which the ferroelectric liquid crystal switches between the two states of the uniform, and the electric field intensity at which the two states cannot be switched between (Hereinafter referred to as “crosstalk”) has a distribution in a direction indicated by an arrow in FIGS.

When the threshold value and the crosstalk are affected by the temperature gradient, the electric field intensity range in which the liquid crystal element can be displayed (hereinafter referred to as "driving margin") is also affected by the temperature gradient. As a result, the driving conditions of the liquid crystal in the liquid crystal element become different, and there arises a problem that the uniform driving display cannot be performed over the entire display surface.

In particular, in a liquid crystal device using a ferroelectric liquid crystal exhibiting the above-described alignment characteristics, the cell gap of the liquid crystal device is considerably narrower than that of a liquid crystal device using a liquid crystal that can be driven by another simple matrix system. Gradients are a bigger problem.

In order to solve the above problems, it has been proposed to change the magnitude of the electric field applied to the liquid crystal or the thickness of the liquid crystal layer according to the temperature gradient. As a specific method, it is intended to control the cell thickness distribution by the spray density of the spacer or the particulate adhesive, or the pressing pressure by a hot roller.

Among them, a method applicable to a cell using the above-mentioned partition member is pressing by a hot roller.
This method has a problem in the compatibility with the cell thickness distribution pattern and the adhesiveness and orientation since it is a separate step from the curing of the resin. Also, the hot roller press itself is an additional step.

An object of the present invention is to provide a method for manufacturing a liquid crystal element using a partition member which can meet a required cell thickness distribution pattern and can obtain a sufficient adhesive strength, and is affected by heat generated from a driving electrode. It is an object of the present invention to provide a liquid crystal element capable of performing uniform driving display over the entire display surface without using the same. Furthermore, in ferroelectric liquid crystal devices suitable for high-speed, high-definition, large screens, we will provide orientation, driving reliability, impact resistance, and low-temperature storage properties to provide inexpensive, high-performance liquid crystal devices. is there.

[0019]

According to the first aspect of the present invention, a pair of substrates each having a stripe-shaped transparent electrode are opposed to each other via a partition member such that the transparent electrodes are orthogonal to each other. A liquid crystal element comprising a pair of substrates bonded to each other, a liquid crystal interposed therebetween, an auxiliary metal electrode on at least one of the transparent electrodes, and a liquid crystal driving voltage supply connected to at least one of the four sides. In the step of spin-coating the partition member forming material on the one substrate, the temperature of the substrate is controlled by controlling the temperature of a substrate holder on which the substrate is mounted, whereby the partition member is formed. By forming a film thickness distribution on the forming material film and patterning the material film, the thickness of the partition member in the direction perpendicular to the substrate decreases as the distance from the connection portion of the liquid crystal driving voltage supply source decreases. And forming so that.

A second aspect of the present invention is that a pair of substrates each having a stripe-shaped transparent electrode are opposed to each other via a partition member such that the transparent electrodes are orthogonal to each other, and the pair of substrates are separated by the partition member. A liquid crystal element having an auxiliary metal electrode on at least one of the transparent electrodes, and a liquid crystal driving voltage supply connected to at least one of the four sides thereof. A liquid crystal element in which the thickness of the partition member in the vertical direction decreases as the distance from the connection portion of the liquid crystal drive voltage supply source decreases, and the liquid crystal element is manufactured by the method of manufacturing a liquid crystal element of the present invention. .

[0021]

FIG. 1 is a schematic partial sectional view of an embodiment of the liquid crystal device of the present invention. In the figure, 11 and 12 are substrates, 13 and 14 are transparent electrodes, 15 and 16 are auxiliary metal electrodes, 17 and 18 are alignment films, 19 is a partition member, and 20 is a liquid crystal compound.

In the present invention, a commonly used glass substrate is used as the substrates 11 and 12. However, the present invention is not limited to this, and plastics and the like are preferably used as long as they have necessary characteristics such as transparency and strength. Can be The transparent electrodes 13 and 14 are formed of a transparent conductive material such as ITO, and the transparent electrode 13 is formed in a stripe shape in a direction parallel to the plane of the paper and the transparent electrode 14 is formed in a stripe shape in a direction perpendicular to the plane of the paper. The auxiliary metal electrodes 15 and 16 are made of metal such as chromium or aluminum, and are formed adjacent to the transparent electrodes 13 and 14, respectively, or along the stripes thereon as shown in FIG. As the alignment films 17 and 18, a film obtained by rubbing a polyimide film or the like is used, but not limited to this, and a low energy alignment film such as an inorganic oxide film may be used. Also, the alignment films 17 and 18
May be the same or different.

As a material of the partition member 19 according to the present invention, a photosensitive material such as an acrylic photosensitive resin which can be applied in a solution state and which can be easily patterned by a photolithography process is used as a material for the partition member 19 finally bonded. It is preferable to use either a positive type or a negative type. The material film is cured by heating in the substrate bonding step.
Further, the thickness of the partition member 19 according to the present invention in the direction perpendicular to the substrate is formed so as to become thinner as the distance from the liquid crystal driving voltage supply source connected to the liquid crystal element increases. That is, the liquid crystal element of the present invention is configured such that the cell gap becomes narrower as the distance from the connection portion of the liquid crystal driving voltage supply source increases, thereby canceling out in-plane threshold value unevenness due to heat generation of the driving electrodes. Further, the partition member 19 according to the present invention.
Are formed in a desired shape such as a stripe shape or a dot shape, similarly to the conventional partition member.

In the liquid crystal device of the present invention, the transparent electrodes 13 and 14, the auxiliary metal electrodes 15 and 16,
After the formation of 7 and 18, the material for forming the partition member 19 is spin-coated on the substrate 12 while controlling the temperature of the substrate, the obtained material film is patterned, and a liquid crystal injection port is formed on the periphery of one substrate. After removing the sealing material, the two substrates are overlapped and subjected to a predetermined pressure and heat treatment to cure the sealing material and the partition member 19, and the liquid crystal is injected from a liquid crystal injection port by, for example, a capillary injection method, and the liquid crystal is injected. Obtained by sealing the inlet.

In the present invention, the temperature of the substrate is controlled by controlling the temperature of the substrate holder on which the substrate is placed, in the step of spin-coating the material for forming the partition member 19,
By forming the temperature distribution in the substrate surface, a film thickness distribution can be formed on the material film formed on the substrate. Specifically, for example, a substrate holder as shown in FIG. 2 is used. FIG. 2A is a schematic plan view, and FIG.
It is a cross section schematic diagram. In the figure, reference numeral 23 denotes a substrate position where the above-mentioned material for forming a partition member is spin-coated, and reference numeral 22 denotes a position where the temperature of the substrate is controlled.

The substrate holder shown in FIG. 2 is of a type in which liquid crystal driving voltage supply sources are arranged on four sides of a liquid crystal element.
Therefore, this is a member for forming the cell gap in the central portion to be the narrowest (the thickness of the partition member 19 in the direction perpendicular to the substrate is the smallest in the central portion). Can be simultaneously spin-coated. The temperature of the substrate holder can be controlled at a high speed by, for example, embedding a Peltier element in a predetermined pattern.

The effect of the present invention can be obtained as long as the liquid crystal used in the present invention needs to have a cell gap distribution in the simple matrix driving method described above. As described above, a chiral smectic liquid crystal such as a ferroelectric liquid crystal and an antiferroelectric liquid crystal is preferably used. For example, a liquid crystal composition comprising a fluorine-containing liquid crystal compound having a fluorocarbon terminal portion and a hydrocarbon terminal portion, wherein both terminal portions are bound by a central nucleus, and having a smectic intermediate phase or a potential smectic intermediate phase. It is also suitably used when using, for example.

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and the technology of the conventional liquid crystal element can be applied to the configuration other than the configuration defined in claim 1 or 3 of the present invention.

[0029]

Example 1 As a first example of the present invention, a liquid crystal device having the structure shown in FIG. 1 was manufactured.

First, a stripe-shaped I is placed on two glass substrates.
Forming a TO pattern and an auxiliary metal electrode in a predetermined process,
A polyimide film having a thickness of 5 nm was formed on one of the substrates, and rubbed in parallel with the stripe with a nylon-based rubbing cloth to form an alignment film. On the other substrate, as a low surface energy alignment film, a silica solution in which antimony-doped SnO ₂ fine particles were dispersed was applied to form a 100 nm inorganic oxide film.

Acrylic photosensitive resin ("CL-016S" manufactured by Tokyo Ohka Kogyo Co., Ltd.) is used as the partition member, and the temperature of the substrate holder (spinner head) is set at 5 degrees below the substrate temperature.
The spin coating was performed at 1000 rpm for 10 sec while maintaining the temperature at a high level, and prebaked at 90 ° C. for 180 sec. The resin film after prebaking had a central value of 2.7 μm, a film thickness difference of 10% of the central value, and a concave film thickness distribution at the center. After this was cooled to room temperature, it was cooled by a high pressure mercury lamp through a mask.
An ultraviolet ray of 00 mJ / cm ² (365 nm) was irradiated.
Next, after developing with a 5% aqueous solution of triethanolamine for 20 seconds, rinsing with pure water, a pitch of 100 μm, and a line width of 10
A stripe-shaped partition member having a thickness of 2.5 μm and an average height of 2.5 μm was obtained.

A sealing material is drawn on one peripheral edge of the substrate, and two substrates are superposed on each other so that the electrodes are opposed to each other so as to be orthogonal to each other, and pressed at 150 ° C. while pressing at 0.15 kg / cm ^2. The cells were cured by heating for an hour to obtain cells. The orientation direction is orthogonal to the partition member.

After the inside of the cell is evacuated and a ferroelectric liquid crystal is applied to the liquid crystal injection port, the pressure is returned to the atmospheric pressure, and the liquid crystal is injected into the cell at a temperature at which the liquid crystal is isotropic. The liquid crystal element was obtained by sealing with a sealing material.

Four sides of the driving element were mounted on the liquid crystal element by a predetermined process to complete an FLC module panel. The cell thickness of this panel had a median value of 1.9 μm, a maximum cell thickness difference of 0.2 μm, and a concave cell thickness distribution at the center. Thus, even though the temperature difference between the mounting end and the center of the panel due to heat generated during driving is about 5 ° C., the threshold thickness unevenness in the panel is offset by the cell thickness distribution, and the reduction of the driving margin is suppressed. did it.

Comparative Example The same material for forming a partition member as in Example 1 was spin-coated on the substrate coated with the low surface energy alignment film of Example 1 at a room temperature of the substrate holder. This was prebaked at 90 ° C. for 180 seconds in the same manner as in Example 1. The film thickness of the obtained material film was 3.0 μm at the median, and the film thickness difference was 10% of the median, forming a substantially flat film thickness distribution.

An FLC module panel was manufactured in the same manner as in Example 1 except for the following steps and the substrate on the opposite side.

The cell thickness of the panel is 2.1 μm at the median.
m, the maximum cell thickness difference was 0.2 μm, and the cell thickness distribution was almost flat. As a result, the temperature difference between the mounting end and the center of the panel due to heat generated during driving is about 5 ° C., and the driving margin is greatly reduced due to uneven threshold voltage in the panel.

[Example 2] A stripe-shaped ITO electrode and an auxiliary metal electrode were formed on two glass substrates, respectively.
An inorganic oxide ("MOF, Ti" manufactured by Tokyo Ohka Kogyo Co., Ltd.)
-Si ") and a polyimide film (" LP-6 "manufactured by Hitachi Chemical Co., Ltd.)
4)), a rubbing treatment was performed. afterwards,
A photosensitive resin film was formed on one of the substrates in the same manner as in Example 1, and was patterned in a stripe shape by a photolithography method to form a partition member between the electrodes.

The substrates were bonded so that the rubbing directions were parallel, baked under pressure in the same manner as in Example 1, liquid crystal was injected by a capillary injection method, and drive elements were mounted to obtain an FLC module panel. . The liquid crystal used in this example is a chiral smectic liquid crystal having a negative dielectric anisotropy.

Also in this embodiment, by forming a desired cell thickness distribution, a sufficient drive margin was obtained even with this type of panel generating a large amount of heat during driving.

[0041]

As described above, according to the present invention,
Threshold unevenness due to the in-plane temperature distribution of the liquid crystal element is offset by forming the thickness distribution of the partition member, and the liquid crystal element for uniform driving display over the entire display surface without being affected by the heat generated from the driving electrodes. Can be provided. In particular, when the present invention is applied to an FLC panel suitable for a high-speed, high-definition, large-screen, it has an effect on the heat generation from the drive electrode while achieving the improvement of the void defect at the time of injection, the improvement of the low-temperature storage property and the improvement of the impact resistance. Uniform drive display over the entire display surface without being performed can be realized. Further, according to the present invention, since the thickness distribution of the partition member can be easily formed by controlling the temperature of the substrate holder, it is possible to cope with a case where a large number of cells are taken from one substrate. It is possible to improve the productivity of the liquid crystal element as well as to improve the productivity and reduce the price.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of one embodiment of a liquid crystal element of the present invention.

FIG. 2 is a schematic view of an embodiment of a substrate holder used in the present invention.

FIG. 3 is an explanatory diagram of a temperature distribution of a liquid crystal element solved by the present invention.

FIG. 4 is an explanatory diagram of a temperature distribution different from FIG.

[Explanation of symbols]

 11, 12 Substrate 13, 14 Transparent electrode 15, 16 Auxiliary metal electrode 17, 18 Alignment film 19 Partition member 20 Liquid crystal compound 22 Temperature control position 23 Substrate position 31 Liquid crystal element 32, 32a, 32b Information signal applying element group 33 Scanning signal application Element group

Claims (9)

[Claims] 1. A pair of substrates each having a transparent electrode in the form of a stripe are opposed to each other via a partition member such that the transparent electrodes are orthogonal to each other, and the pair of substrates are adhered to each other with the partition member. A liquid crystal element sandwiched between the two substrates, an auxiliary metal electrode provided on at least one of the transparent electrodes, and a liquid crystal driving voltage supply source connected to at least one of the four sides thereof. In the step of spin-coating the partition member forming material, by controlling the temperature of the substrate by controlling the temperature of the substrate holder on which the substrate is mounted, to form a film thickness distribution on the partition member forming material film, By patterning the material film, the thickness of the partition member in a direction perpendicular to the substrate is formed so as to become thinner as the distance from the connection portion of the liquid crystal drive voltage supply source increases. Method for manufacturing a liquid crystal element. 2. The method according to claim 1, wherein the temperature of the substrate holder is controlled at a high speed by a Peltier device embedded in the substrate holder in a predetermined pattern. 3. A pair of substrates each having a stripe-shaped transparent electrode are disposed so as to face each other via a partition member such that the transparent electrodes are orthogonal to each other, and the pair of substrates are adhered to each other by the partition member. A liquid crystal element having an auxiliary metal electrode on at least one of the transparent electrodes, and a liquid crystal driving voltage supply connected to at least one of the four sides thereof. The thickness of the member
3. A liquid crystal element which becomes thinner as the distance from the connection portion of the liquid crystal drive voltage supply source increases, wherein the liquid crystal element is manufactured by the manufacturing method according to claim 1 or 2. 4. The liquid crystal device according to claim 3, wherein the partition member has a stripe shape. 5. The partition member according to claim 3, wherein the partition member has a dot shape.
The liquid crystal element according to the above. 6. The liquid crystal device according to claim 3, wherein the liquid crystal is a chiral smectic liquid crystal. 7. The liquid crystal according to claim 6, wherein the liquid crystal is a ferroelectric liquid crystal.
The liquid crystal element according to the above. 8. The liquid crystal device according to claim 6, wherein the liquid crystal is an antiferroelectric liquid crystal. 9. The liquid crystal has a fluorine-containing liquid crystal compound having a fluorocarbon terminal portion and a hydrocarbon terminal portion, both terminal portions of which are bound by a central nucleus and having a smectic intermediate phase or a potential smectic intermediate phase. The liquid crystal device according to claim 6, which is a liquid crystal composition.