JPH11190848A - Liquid crystal element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly drive the liquid crystal element which uses chiral smectic liquid crystal to make a display on the display surface without being affected by the heat generation of a driving electrode. SOLUTION: A partition wall member is formed of a photosensitive resin composition on one of a couple of substrates having striped transparent electrodes, auxiliary metal electrodes, and orientation films formed respectively, the substrates are put one over the other so that the transparent electrodes cross each other, and the partition member is hardened by being heated and pressed while a pressure distribution is formed so that a specific distribution of thickness perpendicular to the substrate of the partition wall member is formed.

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 source on at least one of the four sides. Wherein the thickness of the partition member in a direction perpendicular to the substrate decreases as the distance from the liquid crystal drive voltage supply source increases.

A second aspect of the present invention is a method of manufacturing a liquid crystal device in which a pair of substrates are opposed to each other via a partition member, the pair of substrates are bonded by the partition members, and a liquid crystal is sandwiched in the gap. And forming a partition member made of a heat-curable member on one of the substrates, forming a pressure distribution in the substrate surface in the substrate bonding step, and heating and press-curing the partition member, thereby forming the partition member. Wherein the thickness in the direction perpendicular to the substrate becomes thinner as the distance from the liquid crystal drive voltage supply source increases.

[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.

In the present invention, the partition member 19 is formed of a material which is formed into a predetermined pattern shape, is easily deformed and hardened by a heating and pressing operation in a substrate bonding step, and is hardened to bond the upper and lower substrates. Specifically, a photosensitive material such as an acrylic photosensitive resin is preferable, and either a positive type or a negative type can be used. Further, in the present invention, the partition member 19 may be either a stripe shape or a dot shape, and is appropriately selected.

In the manufacturing process of the present invention, the substrates 11, 1
After forming the transparent electrodes 13 and 14, the auxiliary metal electrodes 15 and 16, and the alignment films 17 and 18 on the substrate 2, the partition member 1 is formed on the substrate 12.
9, a sealing material is drawn on the periphery of one of the substrates except for the liquid crystal injection port, and the two substrates are superimposed and subjected to a predetermined pressurization and heating treatment to cure the sealing material and the partition member 19, thereby forming a liquid crystal injection member. This is a step of injecting liquid crystal from the inlet by, for example, a capillary injection method or the like and sealing the liquid crystal inlet.

In the present invention, by forming a pressure distribution in the surface of the substrate in the pressurizing and heating treatment step,
A predetermined distribution is formed in the thickness of the partition member 19 in a direction perpendicular to the substrate. Specifically, a pressure distribution can be formed by using a pressure distribution forming member as shown in FIG. FIG. 2A is a schematic plan view, and FIG.
It is a cross section schematic diagram. The members include cushioning materials 21a, 21b
A rigid body 22 made of metal, plastic, or the like is interposed therebetween, and the thickness of the rigid body 22 corresponds to the thickness distribution of the partition member 19 of the liquid crystal element to be formed. In the figure, 23 corresponds to the substrate position of the liquid crystal element to be bonded. When this member is placed on the superimposed substrate, the rigid body 22 is located at the center of the substrate of the element. And the thickness of the partition member 19 is reduced. Thereby, the thickness of the partition member 19 in the direction perpendicular to the substrate is formed to be thinnest at the center of the substrate and thicker toward the periphery.
Note that this pressure distribution forming member is a form used when two liquid crystal elements each having a signal applying element group disposed on each of four sides of the liquid crystal element are arranged side by side and bonded together. Set the shape, thickness and position of.

The effect of the present invention can be obtained as long as the liquid crystal used in the present invention needs to have a distribution in the cell gap 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 conventional liquid crystal element technology can be applied to configurations other than the configuration limited in claim 1 or 8 of the present invention. .

[0028]

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.
Auxiliary metal electrodes (three-layer structure of Al / Mo / Al, along the TO pattern (thickness 700 mm) and each ITO line,
A thickness of 1800 °) was formed by sputtering, and a polyimide film having a thickness of 5 nm was formed on one of the substrates, and rubbed parallel to the stripes with a nylon 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.

An acrylic photosensitive resin ("CL-016S" manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as a partition member.
Spin coat at 10 rpm for 10 sec.
Prebaked for 0 sec. The central value of the thickness of the resin film after prebaking was 3.0 μm, and the film thickness difference was 10% of the central value, resulting in a substantially flat film thickness distribution. After cooling to room temperature, 200 mJ / cm through a mask by a high pressure mercury lamp.
² (365 nm) ultraviolet light was applied. Next, development was performed with a 5% aqueous solution of triethanolamine for 20 seconds, followed by rinsing with pure water to obtain a striped partition member having a pitch of 100 μm, a line width of 10 μm, and an average height of 2.5 μm.

A drawing in which a sealing material is drawn on one peripheral edge of the above-mentioned substrate, two substrates are arranged so as to face each other so that electrodes are orthogonal to each other, and are overlapped, and a portion corresponding to the central portion of the cell sandwiches a convex rigid body. 2 at 150 ° C. while applying a pressure of 0.15 kg / cm ² from above the pressure distribution forming member shown in FIG.
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 the 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, and the liquid crystal injection port is used as a sealing material. And sealing was performed to obtain a liquid crystal element. The liquid crystal used in this example is a fluorine-containing liquid crystal composition, and the layer tilt angle δ = 0 ° C. at 20 ° C.
° and tilt angle = 27 °. In addition, the layer tilt angle and the tilt angle of the liquid crystal composition in this example are values measured by the following measuring methods.

[Measurement of tilt angle δ of liquid crystal layer] Basically,
The method performed by Clark and Lagerwal (Jap
an Display '86, Sep. 30 to 0 ct.
2, 1986, 456-458) or the method of Ouchi et al. (JJAP 27 (5) (1988) 725-725).
728). As a measuring device, a rotating cathode type X-ray diffractometer (manufactured by MAC Science Co., Ltd.) is used. In order to reduce the absorption of X-rays to the glass substrate of the liquid crystal cell, a microsheet (80, manufactured by Corning) is used as the substrate.
μm).

[Measurement of tilt angle] ± 30 to ± 50 V, 1
While applying an AC (alternating current) of 100 Hz to between the upper and lower substrates of the liquid crystal element through electrodes, the liquid crystal element disposed therebetween is rotated in parallel with the polarizing plate under crossed Nicols, and at the same time, photomultiplier (Hamamatsu) The second extinction position (the position at which the transmittance becomes lowest) and the second extinction position are determined while detecting the optical response using a photonics company. Then, 1/2 of the angle from the first extinction position to the second extinction position at this time is defined as the tilt angle.

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 substrate as in Example 1 was manufactured.
An FLC module panel was manufactured in the same steps as in Example 1 except that the pressure distribution forming member shown in FIG. 2 was not used.

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 to each other, baked under pressure using a pressure distribution forming member in the same manner as in Example 1, and then liquid crystal was injected by a capillary injection method to mount a driving element. Thus, an FLC module panel was obtained. The liquid crystal used in this example is a chiral smectic liquid crystal having a negative dielectric anisotropy.

Also in the present embodiment, by forming a desired cell thickness, 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. Furthermore, it is possible to cope with a case where a large number of cells are obtained from one substrate, and it is possible to improve the performance of the liquid crystal element and 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 one embodiment of a pressure distribution forming member 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 21a, 21b Buffer material 22 Rigid body 23 Substrate position 31 Liquid crystal element 32, 32a, 32b Information signal applying element group 33 Scan signal applying element group

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinjiro Okada 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

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 having an auxiliary metal electrode on at least one transparent electrode and a liquid crystal driving voltage supply source on at least one of the four sides thereof, wherein the liquid crystal element is provided in a direction perpendicular to the substrate. The thickness of the partition member is
A liquid crystal element, which becomes thinner as the distance from the liquid crystal drive voltage supply source increases. 2. The liquid crystal device according to claim 1, wherein the partition member has a stripe shape. 3. The partition member according to claim 1, wherein the partition member has a dot shape.
The liquid crystal element according to the above. 4. The liquid crystal device according to claim 1, wherein the liquid crystal is a chiral smectic liquid crystal. 5. The liquid crystal according to claim 4, wherein said liquid crystal is a ferroelectric liquid crystal.
The liquid crystal element according to the above. 6. The liquid crystal device according to claim 4, wherein said liquid crystal is an antiferroelectric liquid crystal. 7. 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 linked by a central nucleus and having a smectic intermediate phase or a potential smectic intermediate phase. The liquid crystal device according to claim 4, which is a liquid crystal composition. 8. A method for manufacturing a liquid crystal element, comprising: a pair of substrates arranged to face each other with a partition member interposed therebetween, the pair of substrates being adhered to each other by a partition member, and a liquid crystal being sandwiched in a gap therebetween. A partition member made of a heat-curable member is formed on the substrate, and a pressure distribution is formed in the substrate surface in the substrate bonding step, and the partition member is heated and pressurized and cured, whereby a direction perpendicular to the substrate of the partition member is formed. Wherein the thickness of the liquid crystal element is reduced as the distance from the liquid crystal driving voltage supply source increases. 9. The liquid crystal according to claim 8, wherein said means for forming a pressure distribution in the surface of the substrate superimposes a rigid body having a thickness distribution on the substrate via a buffer material, and uniformly presses the entire surface of the substrate from above. Device manufacturing method.