Source: https://patents.google.com/patent/KR100222272B1/en
Timestamp: 2020-05-30 19:40:28
Document Index: 270639614

Matched Legal Cases: ['Application No. 5', 'art 15', 'art 15', 'art 52', 'art 58', 'art 33', 'art 33']

KR100222272B1 - Lcd device and its manufacturing method - Google Patents
Lcd device and its manufacturing method Download PDF
KR100222272B1
KR100222272B1 KR1019950017649A KR19950017649A KR100222272B1 KR 100222272 B1 KR100222272 B1 KR 100222272B1 KR 1019950017649 A KR1019950017649 A KR 1019950017649A KR 19950017649 A KR19950017649 A KR 19950017649A KR 100222272 B1 KR100222272 B1 KR 100222272B1
KR1019950017649A
KR960015004A (en
와따루 호리에
마사유끼 오까모또
모또히로 야마하라
마꼬또 시오미
노부아끼 야마다
슈이찌 고자끼
1994-10-14 Priority to JP94-249595 priority
1995-02-23 Priority to JP95-035759 priority
1995-02-23 Priority to JP95-35759 priority
1995-06-24 Application filed by 마찌다 가쯔히꼬, 샤프 가부시키가이샤 filed Critical 마찌다 가쯔히꼬
1996-05-22 Publication of KR960015004A publication Critical patent/KR960015004A/en
1999-10-01 Publication of KR100222272B1 publication Critical patent/KR100222272B1/en
The liquid crystal device of the present invention includes a pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are sandwiched by the pair of electrode substrates. At least one of the recess and the recess is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and the liquid crystal molecules are axes perpendicular to the electrode substrate. It is oriented in the liquid crystal region axially symmetrically in the vicinity of at least one of the convex portions.
Liquid crystal device and its manufacturing method
1 is a cross-sectional view of a liquid crystal display device according to the present invention.
2 is a view of a liquid crystal display device of the present invention observed with a polarization microscope.
3 is a view of another liquid crystal display device of the present invention under a polarization microscope.
4 (a) and 4 (b) are cross-sectional views of another liquid crystal display device according to the present invention.
5 is a cross-sectional view of the liquid crystal cell of Example 4. FIG.
6 is a cross-sectional view of another liquid crystal display device according to the present invention.
7 is a cross-sectional view of another liquid crystal display device according to the present invention.
8 is a cross-sectional view of another liquid crystal display device according to the present invention.
9 is a cross-sectional view of another liquid crystal display device according to the present invention.
10 (a) and 10 (b) are cross-sectional views of another liquid crystal display device according to the present invention.
11 is a sectional view of a liquid crystal cell of Example 1;
12 is a sectional view of a liquid crystal cell of Example 2;
13 (a) to 13 (c) are sectional views showing the manufacturing process of one substrate of the liquid crystal display of FIG.
14 is a plan view of the liquid crystal cell of Example 6. FIG.
14 (a) to 14 (d) are sectional views showing the manufacturing process of a liquid crystal cell according to the present invention.
Fig. 15 is a schematic diagram showing precipitation of a liquid crystal phase from a mixture.
16 (a) to 16 (f) show the electro-optical characteristics of the liquid crystal display of Example 1. FIG.
17 (a) to 17 (f) show the electro-optical characteristics of the liquid crystal display of Comparative Example 1. FIG.
18 is a sectional view of a liquid crystal cell of Example 3;
19 is a sectional view of a liquid crystal cell of Example 5;
20 is a sectional view of a liquid crystal cell of Comparative Example 2. FIG.
21 (a) and 21 (b) are views of the liquid crystal cell of Comparative Example 2 observed with a polarization microscope.
22 (a) to 22 (c) and 22 (d) to 22 (f) are diagrams for explaining contrast change with time of the liquid crystal display device in the wide visual mode and the TN mode, respectively.
FIG. 23 is a diagram for explaining non-uniformity of display due to displacement of the alignment axis of liquid crystal molecules.
24 is a plan view of a resist pattern formed on a color filter substrate according to the present invention.
25 is a cross-sectional view taken along the line CC 'of FIG.
Fig. 26 is a sectional view showing an axisymmetric orientation model in the mode according to the present invention.
27 is a plan view of a resist pattern formed on a substrate having an active element according to the present invention.
28 is a cross-sectional view taken along the line AA ′ of FIG. 27.
29 is a sectional view of the liquid crystal cell of Salcy Example 7. FIG.
30 is a view of a liquid crystal cell of Example 7 observed with a polarization microscope.
31 is a sectional view of a liquid crystal cell of Example 9;
32 is a timing diagram of a source signal, a gate signal, and an opposing voltage applied to the pixel electrode of the liquid crystal display device of Example 10;
33 (a) to 33 (e) are sectional views showing the manufacturing process of the color filter substrate according to the present invention.
34 is a cross-sectional view of the color filter substrate of Comparative Example 3 in which the substrate is flat.
35 is a sectional view of a conventional color filter of Comparative Example 4. FIG.
36 (a) to 36 (c) are schematic views showing the position of forming the liquid crystal region in the manufacturing process of the liquid crystal cell of Example 11 and Comparative Examples 3 and 4. FIG.
37 (a) to 37 (c) are views of the liquid crystal cells of Example 11 and Comparative Examples 3 and 4 with a polarization microscope.
1,1a, 2: transparent substrate 3: pixel electrode
4 convex portion 5 first wall
6 counter electrode 7 polymer wall
8 liquid crystal region 9 liquid crystal molecule
10: disclination line 11: matting film
13: pixel 14: liquid crystal domain
16: concave portion 16, 16a, 17: alignment film
20: resist film 32: light shielding film
43: TFT 44: gate wiring
45: source wiring
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a flat panel display such as a portable information terminal, a personal computer, a word processor, an amusement machine, a television set, and a liquid crystal element that can be used in a display panel, window, wall, etc. employing a shutter effect, and a manufacturing method thereof. .
Background Art [0002] Twisted nematic (TN) and super twisted nematic (STN) types using nematic liquid crystals have already been put into practical use as liquid crystal devices such as liquid crystal display devices using electro-optic effects. These types of liquid crystal display elements require a polarizing film and an alignment process. A liquid crystal device such as a liquid crystal display device has a pretilt angle in the initial alignment state, and thus liquid crystal molecules stand in the direction of the pretilt angle when a voltage is applied to the liquid crystal as shown in FIG. 22 (b). Therefore, when such a liquid crystal display element is examined at different viewing angles A and B, the apparent refractive index of the liquid crystal molecules varies with time, thereby changing the display contrast or inverting the contrast with time at gray scale display levels. . This greatly degrades the display quality.
On the other hand, some liquid crystal display device uses a scattering phenomenon of the liquid crystal, and does not use a polarizing plate. These devices utilize dynamic scattering (DS) effects and phase transition (PC) effects.
Recently, a method of electrically controlling the transparent and turbid state of a liquid crystal by using birefringence of the liquid crystal has been proposed. This method does not require an alignment process as well as a polarizing plate. According to this method, basically, the normal refractive index of the liquid crystal molecules and the refractive index of the support medium are set equally. When the liquid crystal molecules are aligned by the application of a voltage, a transparent state is displayed, and when the liquid crystal molecules are not aligned, that is, a cloudy state due to light scattering when no voltage is applied is displayed.
The method comprises, for example, Japanese Patent Office 58-501631, in which a liquid crystal is contained in a polymer capsule, a liquid crystal, a co-curable resin or a thermosetting resin, mixed with the resin of this mixture, and the liquid crystal is precipitated from the resin to form a liquid crystal in the resin. It forms a drop and is disclosed in Japanese Patent Office 61-502128. The liquid crystal display elements obtained by these methods are called "polymer dispersion liquid crystal display elements".
Further, methods for improving the viewing angle characteristics of liquid crystal cells using polarizing plates are described in Japanese Patent Laid-Open Publications Nos. 4-338923 and 4-212928, which disclose polarizing plates in which the polymer dispersed liquid crystal display elements are orthogonal to each other. It is interspersed among the fields. The device greatly improves the visual characteristics. However, since this device uses the polarization cancellation caused by light scattering in principle, the brightness of this type of device is 1/2 as compared with that obtained by the device in TN mode, and thus its use value is low.
Further, another method for improving the viewing angle characteristic is described in Japanese Patent Laid-Open Publication No. 5-27242, in which the alignment state of the liquid crystal is disturbed by the polymer wall and the projections to form the liquid crystal domain randomly. However, in this method, since the domains are formed at random and the polymer material is present in the pixel portion, the light transmittance when no voltage is applied is lowered. In addition, the disc k is randomly generated at the boundary of the liquid crystal domain and does not disappear even when a voltage is applied. This lowers the black level when voltage is applied. For this reason, the contrast of the liquid crystal element of this type is lowered.
Another method of improving viewing angle characteristics is proposed in Japanese Patent Application Laid-Open No. 6-301015 and Japanese Patent Application No. 5-199285 assigned to the present applicant, in which the liquid crystal molecules are, for example, radially or concentrically ( Axially oriented).
The liquid crystal device greatly improves the visual characteristics as described above. However, in these liquid crystal elements, the alignment of the liquid crystals may be disturbed due to indeterminate factors such as residues of resist and scratches of the substrate. This inclines or displaces the axis of symmetry of the orientation of the liquid crystal molecules as shown in FIG. The figure is a view of the liquid crystal device observed with a polarizing microscope. In this case, when the liquid crystal element is observed at different times, the area of a region corresponding to a certain visual direction (a black-looking part) in one pixel becomes larger than other pixels. As a result, the average leakage rate of the pixels is different from the transmittance of other pixels. This is observed by the observer as non-uniformity (display stain) of the screen. Therefore, in the liquid crystal device, the axis of symmetry for the alignment of liquid crystal molecules must be strictly controlled.
In addition, it is necessary to stabilize the axisymmetric orientation in order to facilitate assembly of the liquid crystal element. Axisymmetric orientation is mainly disturbed by non-uniformity of surface free energy on the substrate.
The liquid crystal device of the present invention includes a pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are sandwiched by the pair of electrode substrates. At least one of the recess and the recess is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and the liquid crystal part is an axis perpendicular to the electrode substrate, and the recess and the recess part. It is oriented in the liquid crystal region axially in the vicinity of at least one of the above.
A liquid crystal device according to another aspect of the present invention includes a pair of opposing electrode substrates, a polymer wall and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are sandwiched by the pair of electrode substrates. . A main portion is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and the molecules are axially symmetrically oriented in the liquid crystal region near the main portion as an axis perpendicular to the electrode substrate.
A liquid crystal device according to another aspect of the present invention includes a pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are formed by the pair of electrode substrates. It is sandwiched. At least one of the recess and the recess is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and the liquid crystal molecules are an axis perpendicular to the electrode substrate. It is oriented in the liquid crystal region axially in at least one vicinity. Further, a flattened resin portion is formed on one or both surfaces of the pair of electrode substrates facing the liquid crystal region.
A liquid crystal device according to another aspect of the present invention includes a pair of opposing electrode substrates, a polymer wall and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are sandwiched by the pair of electrode substrates. . A main portion is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and liquid crystal molecules are axially symmetrically oriented in the vicinity of the main portion as an axis perpendicular to the electrode substrate. Further, a flattened resin portion is formed on one or both surfaces of the pair of electrode substrates facing the liquid crystal region.
In one embodiment of the present invention, the planarized electrode substrate includes a matrix LCD substrate, a substrate provided with a color filter, a substrate provided with an active element, and a substrate provided with a stripe electrode.
In another embodiment of the present invention, a color filter is formed on at least one of the pair of electrode substrates, and in the color filter corresponding to the liquid crystal region, recesses between the color filter portions are filled with a resin forming a resin portion and flattened. do.
In another embodiment of the present invention, an active driving element for driving a liquid crystal by applying a driving voltage to an electrode of the electrode substrate is formed on at least one of the pair of electrode substrates, and the active driving element and its wiring Are covered with the resin forming the resin portion and planarized.
In still another embodiment of the present invention, at least one of the recess portion and the convex portion is formed of a film having vertical alignment characteristics and horizontal alignment characteristics.
In another embodiment of the present invention, the liquid crystal storage is composed of a plurality of liquid crystal domains that divide one pixel, and a polymer wall is formed around each of the plurality of liquid crystal domains.
In another embodiment of the present invention, a colored additive is included in the polymer wall.
In another embodiment of the present invention, recesses and convex portions are formed axially or continuously near the axis of symmetry for the alignment of the liquid crystal molecules.
In another embodiment of the present invention, a region where the distance between the electrodes of the pair of electrode substrates is different from the distance in the other regions exists near the axis of symmetry for the alignment of the liquid crystal molecules.
In still another embodiment of the present invention, a first wall is formed on at least one surface of the pair of substrates facing the liquid crystal region to surround the liquid crystal region or the liquid crystal domain, and the height H of the first wall. And the height h of the convex portion has a relationship of H> h.
In another embodiment of the present invention, at least one of the electrode substrate has a color filter, the color filter includes a plurality of color filter portions corresponding to a plurality of pixels, each of the color filter portion facing the liquid crystal region In the surface of the recess is formed.
In another embodiment of the present invention, at least one of the electrode substrate is formed between the plurality of color filter portions and an overcoat layer covers the plurality of color filter portions and convex walls.
In another embodiment of the present invention, the convex wall has a light shielding property.
A liquid crystal device according to another aspect of the present invention includes a pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are formed by the pair of electrode substrates. It is sandwiched. An alignment film made of a polymer having an axisymmetric alignment axis is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and a liquid crystal molecule is an axis perpendicular to the electrode substrate and in the vicinity of at least one of recesses and convexities. Is oriented in the pixel symmetrically.
According to still another aspect of the present invention, there is provided a method of manufacturing a liquid crystal device, wherein a first wall is formed on at least one of the pair of electrode substrates, and at least one of recesses and convex portions is formed at a central portion of the region surrounded by the first wall. Forming or forming an alignment film having at least one of recesses and convex portions in a central portion of the region surrounded by the first wall, and arranging the pair of electrode substrates to face each other; Injecting a mixture containing at least liquid crystal and curable resin into the cell; And curing the curable resin at a temperature equal to or higher than the homogenization temperature of the mixture to phase separate the liquid crystal from the curable resin.
According to still another aspect of the present invention, there is provided a method of manufacturing a liquid crystal device, wherein a first wall is formed on at least one of the pair of electrode substrates, and at least one of recesses and convex portions is formed at a central portion of the region surrounded by the first wall. Forming or forming an oriented foil having at least one of recesses and convex portions in a central portion of the region surrounded by the first wall, and arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And first heating the mixture to a homogenization temperature of the mixture, followed by slow cooling of the mixture to phase-separate the liquid crystal from the curable resin, and curing the curable resin.
According to still another aspect of the present invention, there is provided a method of manufacturing a liquid crystal device, wherein a first wall is formed on at least one of the pair of electrode substrates, and a vertical alignment characteristic or a horizontal alignment characteristic is formed at the center of the region surrounded by the first wall. Forming at least one of a recessed portion and an iron portion formed of a film having a film and arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And heating the mixture to a homogenization temperature of the mixture, curing the curable resin by exposure, and then slowly cooling the mixture.
According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal device, wherein a first wall is formed on at least one of the pair of electrode substrates, and a polymer material having two or more different shapes is formed in an area surrounded by the first wall. Forming a alignment film having an axisymmetric alignment axis by phase-separating a mixed material comprising the same, and then manufacturing the cell by arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And heating the curable resin above the homogenization temperature of the mixture and phase separating the liquid crystal from the curable resin.
According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal device, wherein a first wall is formed on at least one of the pair of electrode substrates, and a polymer material having two or more different shapes is formed in an area surrounded by the first wall. Forming a alignment film having an axisymmetric alignment axis by phase-separating a mixed material comprising the same, and then manufacturing the cell by arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And first heating the mixture to a homogenization temperature of the mixture, slowly cooling the mixture to phase separate the liquid crystal from the curable resin, and curing the curable resin.
In the first embodiment of the present invention, the curable resin is cured while applying at least one of a voltage and a magnetic field to the cell.
In another embodiment of the present invention, an active driving element for driving a liquid crystal by applying a voltage to electrodes of the electrode substrates is formed on one side of the pair of electrode substrates, and applied to the active driving element when the curable resin is cured. The gate driving signal and the voltage are synchronized with the source driving signal voltage applied to the active driving element, and the duty ratio of the gate driving signal voltage is less than 1/2 of the duty ratio of the source driving signal voltage.
According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal device, comprising a pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are the pair of substrates. A liquid crystal element manufacturing method sandwiched by at least one of the above-mentioned pairs of electrode substrates, comprising: forming a plurality of color filter portions on a surface of the substrate; Forming a convex wall between the color filter portions; And forming recesses on the surface of the plurality of color filter portions facing the liquid crystal region by forming an overcoat layer covering the plurality of color filter portions and the convex wall.
In one embodiment of the present invention, the step of forming the recesses,
Applying a resist to cover the plurality of color filter units; And exposing and developing the resist to form convex walls between the plurality of color filter portions.
According to the present invention, recesses and / or convexities or main portions are formed on at least one surface of a pair of electrode substrates facing the display medium. When a mixture containing at least a liquid crystal and a curable resin is injected into a space between a pair of substrates and the liquid crystal and the curable resin (polymer) are phase separated, a liquid crystal precipitates in the recess or a liquid crystal region surrounds the convex portion. As a result, liquid crystal molecules are axially symmetrically oriented radially or concentrically, for example, as the axis of symmetry perpendicular to the substrate, near the recesses, near the irons, and near the major parts. Therefore, in order to obtain a uniform alignment of the liquid crystal, the position of the symmetry axis can be controlled by controlling the formation of recesses and convex portions. As used herein, the term "uniform orientation" means a state in which symmetry axes exist in each pixel in the same positional relationship and liquid crystal molecules are axially symmetric with respect to the symmetry axis.
In addition, in order to eliminate the orientation scattering factor of the liquid crystal molecules in the liquid crystal droplets, the surface of the other electrode substrate facing the substrate on which the recessed portions and / or the convex portions are formed thereon is flattened so that the liquid crystal droplets have the recessed portions described above or the like. It can only be oriented according to the convexity. For example, when a color filter having a color filter portion corresponding to each pixel is disposed on one side of the electrode substrate, and when a color filter having the color filter portion is disposed on one side of the electrode substrate, the color filter portions of the color filter are formed. Liquid crystals precipitate in the recesses formed therebetween. The reason is that liquid crystals tend to be precipitated at the portion where the cell thickness is thick. Thus, the axisymmetric orientation of the liquid crystal droplets is disturbed by the recesses between the color filter portions. This problem can be overcome by filling the recess with a resin to planarize the surface. Accordingly, the liquid crystal is precipitated only in the recesses or convex portions formed on the substrate facing the color filter portion. As another example, when an active driving element is formed on one side of the electrode substrate, many ends are formed on the surface by the multilayer structure of the active driving element and its wirings. The axisymmetric orientation of liquid crystal molecules in the liquid crystal droplets can be disturbed by these ends. This problem can be overcome by filling the end with resin to planarize the surface. Accordingly, the liquid crystal phase appears only at the recessed portion or the convex portion.
The liquid crystal molecules may be axially symmetrical by forming recesses (eg, conical) on the surface of each color filter portion facing the liquid crystal layer corresponding to each pixel. Such recesses can be formed by forming convexities between adjacent color filter portions and then forming an overcoat layer covering the color filter portions and the convex walls. The iron portion may be provided with light blocking characteristics by including a black dye in the material of the iron portion. The convex portion can be easily formed by lithography by the use of a photosensitive material such as a resist.
The recesses and / or convex portions are preferably formed of a film or material having vertical alignment characteristics for stable control of the axis for axisymmetric orientation.
The liquid crystal region may be covered by a single liquid crystal domain or a plurality of liquid crystals that divide one pixel. A polymer wall is formed around each liquid crystal region or around each liquid crystal domain so that the liquid crystal domain can be formed by surrounding pixels or dividing the pixels.
By discoloring the polymer wall with a colored additive such as black, the disclination line can be made invisible.
Concave portions and convex portions may be axisymmetrically and / or combustively formed around the opposite axis of the alignment of the liquid crystal molecules formed as described above. With such a configuration, the center or central portion of the recessed portion or the convex portion can be used as the axis for the axis realigning orientation, so that the orientation having the axes at the same position for all the pixels can be realized.
The recessed portion and the convex portion may be formed on an electrode. Alternatively, the substrate itself may be modified to have recesses and convexities, and electrodes may be formed on the modified substrate. In any case, the distance between the two electrodes of the pair of substrates at the portion where the recesses or convex portions are formed is different from the other portions. The alignment film may be formed on a modified substrate having recesses or recesses to obtain an alignment film having recesses or recesses. These are effective for stabilizing the orientation of liquid crystal molecules.
A first wall having a surface tension different from the other region may be formed on at least one surface of the pair of substrates facing the display medium. By forming the first wall, the axisymmetric orientation of the liquid crystal molecules can be stabilized without using a photoresist. In this case, if the height of the convex portion is higher than the first wall, a polymer pillar may be formed in the convex portion, thereby disturbing the orientation of the liquid crystal molecules.
The mixture comprising at least a liquid crystal and the curable resin may be phase separated by curing the curable resin to a temperature above that at which it is uniformly mixed with each other (hereinafter referred to as " uniform temperature). After heating, slow cooling may phase-separate liquid crystal and curable resin, and harden curable resin.
During phase separation, a voltage and / or a magnetic field may be applied to the cell so that the axis of symmetry for the alignment of the liquid crystal molecules is perpendicular to the substrate.
An alignment film made of a polymer film having an axisymmetric alignment axis is formed on at least one surface of the pair of substrates facing the display medium. The alignment axis of the liquid crystal molecules is almost the same as the alignment axis of the polymer of the alignment film. Thus, the liquid crystal can be axisymmetrically oriented about an axis, for example radially or concentrically, perpendicular to the substrate as the axis of symmetry.
The alignment layer may be formed by phase-separating a mixed material including two or more different types of polymer materials in a region surrounded by a first wall.
In addition, the signal voltage for driving the gate of the active driving element is synchronized with the signal voltage for driving its source, the former pulse width becomes less than half of the latter and the period, and the resin may be hardened while the voltage is applied. Therefore, the potential difference between the gate line and the pixel electrode formed on the same substrate is reduced, and the problem that the axisymmetric orientation of the liquid crystal molecules is disturbed by the potential of the gate line can be overcome.
Accordingly, the present invention provides a liquid crystal device capable of (1) realizing axisymmetric opposition of liquid crystal molecules to improve viewing angle dependence and control an axis for axisymmetric orientation to reduce display stains, and (2) such liquid crystals. Provided is a method of manufacturing a device.
1 is a cross-sectional view showing one pixel portion of a liquid crystal display device according to the present invention.
Referring to FIG. 1, a pixel electrode 3 made of indium tin oxide (ITO) or the like is formed on a transparent substrate 1 made of glass or the like. A convex portion 4 made of resist or the like is formed in the center of the pixel electrode 3, and a first wall 5 made of resist or the like is formed so as to surround the pixel.
As shown in FIG. 2, between the transparent substrates 1 and 2, a liquid crystal region 8 surrounded by the polymer wall 7 is formed corresponding to each pixel. The liquid crystal molecules in the liquid crystal region 8 (in the pixel) are oriented radially around the convex portion 4 as an axis perpendicular to the substrates 1 and 2, thereby obtaining a uniform alignment state.
As described above, the liquid crystal molecules are intentionally axisymmetrically arranged (for example, radial, concentric, and vortex) around the convex portion 4 in the liquid crystal region 8. In addition, the liquid crystal region 8 is substantially a mono-domain region. By this arrangement, the visual characteristic can be improved and the display spots, in particular, the display spots at the gray scale level can be reduced.
[Oriented State of Liquid Crystal Molecules in Domain]
When the liquid crystal display device of this embodiment is observed with a polarizing microscope, as shown in FIG. 2, the cross-shaped matting film pattern 11 is observed in the direction of the polarization axis of the polarizing plate in the liquid crystal region 8 surrounded by the polymer wall 7. do. The liquid crystal molecules are arranged in an axisymmetric (e.g., radial, concentric, and vortex) centered around the center disclination point 12 in the central portion of the liquid crystal region 8, and the liquid crystal region 8 is a monodomain region. It indicates that.
In the above-mentioned liquid crystal display element in the alignment state, the disclination line is formed outside the liquid crystal domain 4 when voltage is applied, but is not formed inside the liquid crystal domain 14. Therefore, it is possible to intentionally form a disclination line outside the pixel. In addition, by forming the disclination line or the disclination point under the light shielding layer, it is possible to improve the black level of the liquid crystal display device to improve the contrast of the display. In this case, the discoloration line can be made invisible by adding a colored (eg black) additive to the material of the polymer wall 7 or the material of the convex portion 4 and the first wall 5. Alternatively, by adding a liquid crystalline polymer to the polymer wall 7, it is possible to obtain an alignment state in which no disclination line is generated.
When a display voltage is applied to the liquid crystal element having the above-described alignment state, the liquid crystal molecules 9 are perpendicular to the substrates 1 and 2, for example, as shown in FIGS. 22 (a) to 22 (c). To stand up. At this time, the liquid crystal molecules 9 are standing at the respective positions of the initial radial or concentric circles. Therefore, the apparent refractive index seen from various directions becomes uniform, so that the visual characteristics of the liquid crystal element can be improved.
[Number of domains in one pixel]
It is preferable that the number of domains in each pixel is as small as possible. If there are a plurality of domains in one pixel, a disclination line is generated at the boundary of each of the domains, and the black level of the display is lowered. Therefore, it is preferable that the pixel 13 is covered by a single domain in which liquid crystal molecules are arranged axially symmetrically in the liquid crystal region 8. In this case, since the disclination line is formed outside the domain when voltage is applied, the disclination line is not formed inside the pixel 13.
In the case where the pixel 13 is rectangular, as shown in FIG. 3, the liquid crystal region 8 has two or more domains 14 in which liquid crystal molecules are arranged in axisymmetry. Further, the liquid crystal display element can have the same excellent visual characteristics as the liquid crystal display element having the monodomain liquid crystal region 8 as shown in FIG. In the case of the liquid crystal display device shown in FIG. 3, the rectangular pixel 13 can be divided into two by forming walls such as the polymer wall 7 and the first wall 5.
In addition, in the liquid crystal display device shown in FIG. 3, the direction of the disclination line formed at the boundary between the domains 14a and 14b of the pixel 13 coincides with the polarization axis of the polarizing plate, thereby eliminating the disclination upon application of voltage. You won't see the line.
Alternatively, a black mask BM may be formed in the pixel so as to conceal the disclination line formed at the boundary between the domains 14a and 14b of the pixel 13.
As described above, when the pixel is divided into a plurality of liquid crystal regions 8 or liquid crystal domains 14, it is necessary to align the alignment weights of the liquid crystal molecules in each liquid crystal region 8 or liquid crystal domain 14. .
[Method 1 for Orienting Liquid Crystal Molecules Asymmetrically]
By forming recesses, convexities, or both in at least one of the pair of substrates or the like, the position of the symmetry axis can be controlled to align the liquid crystal molecules in axisymmetry.
According to this method, the first wall 5 is first formed by patterning, and recesses, convexities, or both are formed in approximately the center of the region enclosed by the first wall, thereby forming regions having different cell gaps. A mixture containing at least liquid crystal and curable resin is injected into the cell. In the case where there is a region where the cell gap is different from other regions (except for the first wall 5 surrounding the pixel), the region acts as an axis of symmetry in the pixel, and the liquid crystal and the curable resin are affected by polymerization or temperature drop. (Or a polymer) phase-separates and liquid crystal precipitates in curable resin. The method of separating the liquid crystal is different depending on the following cases.
(1) When the cell gap of the region acting as the axis of symmetry of the pixels at the time of phase separation is small (convex portions are formed):
When the liquid crystal and the curable resin (or polymer) are phase separated by a polymerization reaction or a temperature drop, the convex portion 4 of the substrate 1 acts as a liquid crystal separation nucleus, as shown in FIG. Develops in a form surrounding the convex portion 4. As a result, the liquid crystal molecules are aligned in a radial or concentric shape around an axis perpendicular to the substrate, thereby obtaining an axisymmetric alignment of the liquid crystal molecules. At the same time, the axis of symmetry and the convex portion 4 can coincide. Therefore, the position of the symmetry axis of the alignment of the liquid crystal molecules can be controlled by controlling the position of the convex portion 4, and the liquid crystal molecules can be oriented in axisymmetry in the pixel.
It is preferable that the height of the convex portion 4 is less than 1/2 of the cell gap and lower than the height of the first wall 5 formed outside the pixel 13 so as to surround the pixel region 8. If the convex portion 4 is too high, a polymer pillar is formed on the convex portion 4. If the polymer pillar is too high, the orientation is disturbed by the polymer technique.
The convex portion 4 should have an appropriate size to act as a liquid crystal separation nucleus. Its size is preferably as small as possible. For example, 30 The following is good. If the convex portion 4 is too large, a polymer pillar is formed on the convex portion 4. Therefore, a voltage drop is generated, which causes a decrease in contrast.
The material of the iron portion 4 is not particularly limited in the present invention, but may be made of an organic material such as a resist and an inorganic material such as SiO 2 , Al 2 O 3, and ITO. When the resist material is used, the convex portion 4 can be easily formed. When ITO made of a transparent conductive film is used, as shown in Figs. 4A and 4B, the pixel electrode 3 made of ITO is formed on the substrate 1 on which the convex portion 4 is already formed. The iron part can be formed by forming (). Alternatively, as shown in FIG. 5, the alignment film 16 may be formed on the substrate 1 on which the convex portions 4 are already formed. In order to arrange the convex portion (the convex portion 4 covered with the pixel electrode or the alignment film) at the center of the liquid crystal alignment, it is preferable to use a material having vertical alignment. As such a material, for example, a resist material to which an F or Si-based additive is added may be used. In particular, the material whose surface free energy becomes 35 mN / m or less is preferable. In addition, the orientation stability can be increased when the first wall 5 and the convex portion formed around the pixel are formed of different materials.
Although the shape of the convex portion 4 is not particularly limited in the present invention, the convex portion 4 may be circular, square, rectangular, elliptical, star, cross, or the like. The convex portion 4 need not have the same size in the vertical direction, and may have an inclined portion as shown in FIG.
(2) When the cell gap of the region serving as the axis of symmetry of the upper lid is large (when the recess is formed):
When the liquid crystal and the curable resin (or polymer) are phase-separated by the polymerization reaction or the temperature drop (particularly due to the temperature drop), when the recessed portion 15 is formed on the substrate 1 as shown in FIG. In the curable resin, the top-neutral liquid crystal is stabilized by being spherical to minimize the surface energy of the recessed portion 15. As a result, the liquid crystal region 8 develops so that the liquid crystal precipitates in the recessed portion 15 and surrounds the recessed portion 15. Accordingly, the liquid crystal molecules are aligned in a radial or concentric form around the axis perpendicular to the substrate, so that the alignment of the axisymmetric states of the liquid crystal molecules is obtained. At the same time, the axis of symmetry and the recesses 15 can coincide. Therefore, the position of the axis of symmetry of the alignment of the liquid crystal molecules can be controlled by controlling the position of the recessed portion 15, and the liquid crystal can be oriented in axisymmetric in the pixel.
The depth of the recessed portion 15 is not particularly limited in the present invention. However, when an organic material such as resist 20 is used, the depth is preferably as small as possible so as to reduce the voltage drop that causes the contrast decrease.
It is preferable that the size of the recessed part 15 is large. However, the size depends somewhat on the size of the pixel. Preferably, about 40 of the pixel area It is enough.
The recess 15 is not particularly limited in the material of the present invention, but may be made of an organic material such as resist 20 or an inorganic material such as SiO 2 , Al 2 O 3, and ITO.
The shape of the recessed part 15 is not particularly limited in the present invention, but may be circular, square, rectangular, elliptical, star-shaped, or cross-shaped. The recessed portions 15 need not have the same size in the vertical direction and may have an inclined portion as shown in FIG.
(3) When both regions having a large cell gap and a small cell gap are formed in the pixel (both convex and concave portions are formed):
In the phase separation of the liquid crystal and the curable resin (or polymer) by the polymerization reaction or the temperature drop, if both the convex portion 4 and the concave portion 15 are present on the substrate 1, the liquid crystal is precipitated in the concave portion 15 and the pixel The liquid crystal region 8 develops so as to surround the recessed portion 4 in the central portion of the. Thus, by using the convex portion 4 as the symmetry axis, the position of the symmetry axis can be fixed with respect to all the pixels, so that the display spot can be reduced.
The convex and recessed portions may be formed axially symmetrically as shown in FIG. 9 or may be continuously formed as shown in FIG.
The surface height of the recess 15 and the convex portion 4 may be the same as the flat surface or may be different from each other.
(4) In the case where convex and / or recessed portions are formed on two substrates:
In the above cases (1)-(3), at least the recessed portion 15 or the recessed portion 4 is formed in one of the pair of substrates among the recessed portion 5, the recessed portion 4, and the first wall 5. . However, as shown in FIGS. 10 (a) and 10 (b), the first wall 5 is formed on the substrate 1, while the recessed portion 15 or the convex portion 4 is formed of the substrate ( 2) or on both substrates (1, 2).
When at least one of the recessed portion 15 and the convex portion 4 is formed on the substrate 1, as shown in FIGS. 5, 11 and 12, on another substrate, that is, on the counter substrate 2 An alignment film 17 is formed on the substrate. The alignment film 17 on the counter substrate 2 serves to planarize the unevenness of the counter substrate 2 or the passivation film (not shown) or to uniform the surface energy. Therefore, when phase-separating into the liquid crystal from the curable resin (or polymer), the liquid crystal is prevented from being separated at positions other than the above-mentioned recesses and convexities.
(5) When color filter is formed on the opposing substrate:
The case where a color filter having a plurality of color filter parts respectively corresponding to pixels is formed on a surface of an opposing substrate facing a substrate on which recesses or convex parts are formed. The color filter is formed between adjacent filter parts corresponding to pixels. Have a main point. When phase separating the liquid crystal from the curable resin (or polymer), the liquid crystal is separated in a region having a thick cell thickness as described above. Thus, the liquid crystal will tend to separate at the recesses formed between adjacent filter portions, and therefore the axisymmetric orientation of the liquid crystal molecules in the droplets cannot be obtained. This problem can be solved by filling the recess with a resist resin to planarize the surface of the color filter. Therefore, the cause of disturbing the orientation of the liquid crystal molecules in the droplets can be eliminated, and only the recesses or convex portions formed on the substrate facing the color filter may cause the appearance of the liquid crystal from the curable resin (or polymer) during phase separation of the liquid crystal. Can be limited
(6) When an active driving element is formed on the opposing substrate:
The case where the active driving element is formed on the planarized electrode substrate will be described. Since the active drive element and its wiring are multi-layered, many ends are formed. The ends may disturb the axisymmetric orientation of the liquid crystal molecules. However, this problem can be solved by filling the end with resin and flattening the surface. Therefore, the liquid crystal can be made to appear only in the recessed or convex portions.
[Method of forming recess, convex part and first wall]
The recess, the convex portion and the first wall can be formed by the following method.
(1) Method of using resist material:
The case where the substrate 1 has the convex portion 4 as shown in FIG. 1 will be described with reference to FIGS. 13 (a) to 13 (c).
First, as shown in FIG. 13 (a), a resist is applied to the substrate 1 and exposed and developed to form the convex portion 4 in the center of the pixel as shown in FIG. 13 (b). Next, as shown in FIG. 13 (c), another resist is applied, and exposed and developed to form the first wall 5 around the pixel. The convex portion 4 and the first wall 5 may be made of the same material. The same process can be used to form the recess.
After formation of the first wall 5, the material of the alignment film or the resist material is applied to the substrate 1 and solidified. The alignment film or resist has a thick portion near the first wall 5. As a result, as shown in FIG. 10 (b), the concave recessed portion 15 is obtained which becomes shallower as the pixel center portion is deepest and approaches the first wall 5.
(2) How to process the substrate itself:
When a plastic substrate is used, irregularities can be formed in the substrate itself by embossing or the like to form recesses, convex portions, or first walls. As shown in FIGS. 4A, 4B, and 5, a transparent electrode or an alignment film may be formed on a substrate having recesses or convexities.
(3) How to use inorganic materials:
Inorganic materials such as SiO 2 , Al 2 O 3, and ITO may be deposited on the substrate and patterned using a mask to form recesses, iron portions, or first walls.
(Method for forming a substrate having a color filter facing the substrate having recesses or convexities)
24 is a plan view of a resist pattern formed on a substrate on which a color filter is formed (hereinafter referred to as a color filter substrate) according to the present invention. 25 is a cross-sectional view taken along the line C-C 'of FIG. 24 and 25, the material of the light shielding film 32 is deposited on the glass substrate 31 and patterned to etch the material on the portion corresponding to the pixel region, thereby forming the light receiving portion. Other material portions that do not correspond to the pixel region are not etched to form the light shielding film 32. Next, R, G, and B color filter portions 33 are formed in the light receiving portion. A resist resin is applied to the color filter substrate having the color filter portion 33 and the resist resin deposited on the color filter portion 33 is peeled off to form the resist resin portion 34 on each light shielding film 32. In this manner, recesses between the adjacent color filter portions 33 are filled with the resist resin portion 34 to planarize the surface of the color filter substrate. By this flattening, the cause of disturbing the axisymmetric orientation of the liquid crystal molecules in the droplets can be eliminated, and the liquid crystal can be separated only at the recessed portions or convex portions disposed on the opposing substrate.
[Materials for Making Recesses and / or Irons]
As the resist material, conventional photoresist material may be used. Since recesses, convexities and first walls 5 remain in the cell, it is preferable to use photosensitive polyimide having excellent heat resistance. When the resist material is used, the liquid crystal material tends to remain on the resist in the appeal (e.g., the periphery 20 and the convex portion 4 of the recessed portion 15 in Fig. 9), so that the contrast decreases. Excitation resist material is preferred, for example, a color resist incorporating colored pigment in the resist material can be used.
In the axisymmetric alignment model shown in FIG. 26, it can be observed that the liquid crystal molecules 42 are vertically aligned near the axis of symmetry 41 of the axisymmetry. In view of this fact, in order to facilitate the axisymmetric alignment of liquid crystal molecules, it has been proposed to actively bring the liquid crystal molecules near the pixel center portion into a vertical alignment state. It is also proposed that the recessed portion 15 or the convex portion 4 be formed of a material having vertical alignment. As the material having the vertical alignment property, an organic film imparting photosensitivity to the polyimide having the vertical alignment property, an inorganic film obliquely deosited with a material such as SiO 2 , or the like may be used. Alternatively, the vertical alignment layer may be first formed on the substrate and then covered with the horizontal alignment layer except for a portion corresponding to the center portion of the pixel to expose the vertical alignment layer only at the pixel center portion.
[Method 2 for Orienting Liquid Crystal Molecules Asymmetrically]
As shown in FIG. 14 (a), an alignment film 16a made of a polymer having an axisymmetric alignment axis is formed on one of the substrates. In this configuration state, the liquid crystal molecules can be axially symmetrically aligned in a state where the alignment axis of the alignment film 16a and the alignment side of the liquid crystal molecules are substantially coincident.
[Axis Symmetrical Alignment Film Forming Method]
Referring to FIGS. 14 (b) to 14 (d), after formation of the first wall 5, a mixed material containing two different polymer materials is applied to the substrate 1a. Thereafter, the two kinds of polymer materials in the mixture are phase-separated in axisymmetry, that is, radially or concentrically, or the like to form an alignment film having an axisymmetric alignment axis.
A cell is formed using the substrate 1a having an axisymmetric alignment film, and a mixture of liquid crystal and curable resin (or polymer) is injected into the cell. Thereafter, when the mixed radish is subjected to polymerization or temperature drop, the liquid crystal is phase separated from the curable resin. As a result, the liquid crystal molecules are axially symmetrically aligned in a state where the alignment axis of the alignment film 16a and the alignment axis of the liquid crystal molecules are substantially coincident.
[How to form a polymer wall]
(1) A mixture containing at least liquid crystal and curable resin is injected into the cell, and the mixture is cured at a temperature equal to or higher than the homogenization temperature. Next, the liquid crystal and the curable resin (polymer) are phase separated to form a liquid crystal region surrounded by the polymer wall.
(2) A mixture containing at least liquid crystal and curable resin is injected into the cell. The mixture is heated above the homogenization temperature of the mixture and gradually cooled to phase separate the liquid crystal from the curable resin. Thereafter, the curable resin is cured to form a liquid crystal region surrounded by the polymer wall.
In the above methods (1) and (2), when a photocurable resin is used, it can be cured by irradiation of ultraviolet (or visible) light.
In any case, since recesses, convex portions, or alignment films are formed, the position where the liquid crystal is deposited and where the liquid crystal region and the polymer wall are formed can be controlled without generating the irradiation intensity distribution by the photomask.
[Method of Controlling Orientation by Polymeric Material]
(1) In order to effectively align the liquid crystal molecules in the alignment direction when voltage is applied, a neutralizing liquid crystal material such as a liquid crystalline photocurable resin having a functional group or a similar functional group in the molecule is added to the mixture of the curable resin and the liquid crystal. It is desirable to. Further, when the liquid crystal in the mixture is phase separated from the curable resin in the cell, in some cases, a curable resin may be formed that inhibits the effect of the vertical alignment on islands such as iron parts made of a material having a vertical alignment. Therefore, even if the curable resin is formed on the island, it is preferable that the vertical alignment of the island can be transferred to the liquid crystal phase.
(2) How to apply voltage or magnetic field during phase separation
It is important that the axisymmetric orientation of the liquid crystal molecules is formed in the pixel and that the axis of symmetry of the orientation is not widely displaced with respect to the substrate. According to the inventor's review, when the liquid crystal is phase-separated from the curable resin by applying a voltage and / or a magnetic field to at least a mixture containing the liquid crystal and the curable resin (or polymer), the axes of the axisymmetric alignment of the inverted molecules in the liquid crystal region are all pixels. It can be fixed in the vertical direction with respect to the substrate. This phenomenon is preferable because the axis of the axisymmetric orientation can be more reliably and stably controlled by using an island having vertical alignment such as an iron portion made of a vertical alignment material to orient the liquid crystal molecules. As shown in FIG. 15, in the case where the liquid crystal is in a small droplet state appearing in the uniform phase 19, the application of voltage and / or magnetic field is particularly effective. Therefore, the voltage and / or magnetic field can be weakened before the liquid crystal region 8 grows to cover the entire pixel. The voltage and magnetic field intensity must be greater than the threshold of the liquid crystal (value evaluated by the TN cell) and can be changed periodically.
Next, the case where it is formed on a substrate having an active element such as a thin film transistor (TFT) will be described.
27 is a plan view of a substrate with active elements in accordance with the present invention. FIG. 28 is a sectional view taken along the line A-A 'of FIG.
27 and 28, the drain electrode of the TFT 43 as an active driving element is connected to each pixel electrode. Therefore, in order to apply a voltage to the pixel electrode, an appropriate voltage is applied to the gate electrode connected to the gate wiring 44 so as to provide a voltage between the source wiring 45 and the pixel electrode, that is, between the source electrode and the drain electrode of the TFT 43. The connection must be in a conductive state. Therefore, when a phase is applied by applying a voltage to the mixture of liquid crystal and the curable resin, an electric potential difference is generated between the pixel electrode (drain electrode) and the gate wiring 44 on the same substrate. Will be affected by the potential of).
The present inventors have found that the problem of disturbing the axisymmetric orientation of the liquid crystal molecules described above can be solved by appropriately controlling the timing, time, and magnitude of the voltage to be described below which are applied to the gate electrode.
In order to minimize the potential difference between the pixel electrode formed on the same substrate and the gate wiring 44, the voltage applied to the pixel electrode of the cell is a signal voltage for driving the gate electrode of the active driving element when the curable resin is cured. It should be determined so that the pulse width of the signal voltage for driving the gate electrode is synchronized with the signal voltage for driving the source electrode of the active driving element to be 1/2 or less of the period of the signal voltage for driving the source electrode.
As the curable resin of the present invention, a photocurable resin or the like may be used. As the photocurable resin, for example, acrylic acid and acrylic acid ester having 3 or more long-chain alkyl groups or benzene rings having carbon atoms are recommended. More specifically, isobutyl acrylate, stearyl acrylate, lauryl acrylate, isoamyl acrylate, n-butyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, 2-ethyl Hexyl acrylate, n-stearyl methacrylate, cyclohexyl methacrylate, benzine methacrylate, 2-phenoxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate and the like. Moreover, in order to raise the physical strength of a polymer, polyfunctional resin more than bifunctional group is preferable. Examples of such resins include bisphenol A dimethacrylate, bisphenol A diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, trimethylol Propanetriacrylate, tetramethylolmethanetetraacrylate, neopentyldiacrylate, R-684 and the like. In addition, in order to clarify the phase separation of the liquid crystal in the curable resin, it is preferable to halogenate, in particular, chlorinate and fluorinate the monomer. Examples of each resin include 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-trifluoropropyl methacrylate, perfluorooctylethyl methacrylate, perchlorooctylethyl methacrylate, curfluorooctylethyl Acrylate, perchlorooctylethyl acrylate and the like are recommended.
[Photopolymerization inhibitor]
In order to enlarge the liquid crystal droplets, i.e., the liquid crystal region 8, it is preferable to add a compound which suppresses the polymerization reaction other than the curable resin to the mixture. The compound is, for example, a monomer or compound capable of stabilizing lycal by resonance effect after radical generation. Specifically, a polymerization inhibitor such as styrene derivatives such as styrene, p-chlorostyrene, p-phenylstyrene, and p-methylstyrene, and nitrobenzene may be used.
The mixture may comprise a photopolymerization initiator. The initiators can be used, such as, for example, Irgacure 184,651,907 (manufactured by Ciba Geiza), and Darocure 1173,1116,2956 (manufactured by E, Merek). In addition, sensitizers that can be polymerized into visible light can be added to the mixture to improve retention.
The addition amount of the polymerization initiator added to the mixture is not particularly limited in the present invention because it depends on the reactivity of each compound. However, for a mixture of liquid crystal and curable resin (including the liquid crystalline polymer material described later), 0.01-5 Range is preferred. Added amount 0.01 If less, the polymerization reaction does not occur sufficiently. And also 5 If this is the case, phase separation of the liquid crystal from the polymer occurs so quickly that it is difficult to control the phase separation. The liquid crystal droplet is small, so that the driving voltage is increased and the control of liquid crystal alignment on the substrate is weakened. In addition, when the liquid crystal region in the pixel is reduced and the irradiation intensity distribution is provided by using a photomask, a liquid crystal droplet is formed in the light shielding portion (outside the pixel). Therefore, the display contrast is lowered.
As the liquid crystal of the present invention, an organic mixture showing a liquid crystal state near room temperature is used. Such liquid crystals include nematic liquid crystals (liquid crystals for two-frequency driving; Cholesteric liquid crystals (sometimes, liquid crystals having selective reflection characteristics for visible light), smectic liquid crystals, ferroelectric liquid crystals, and discotic liquid crystals. Liquid crystals of this type can be used in combination. In particular, a nematic liquid crystal to which a cholesteric liquid crystal (chiral agent) is added is preferable in view of characteristics.
In addition, a liquid crystal material having excellent chemical reactivity is preferable because it involves a photopolymerization reaction during processing. Examples of such liquid crystal materials include ZLI-4801-000, ZLI-4801-001, ZLI-4792 and ZLI-4427 (manufactured by Merck).
[Polymerizable Liquid Crystal Material]
A liquid crystalline compound having a polymerizable functional group (hereinafter referred to as a polymerizable liquid crystal material; the material itself does not need to express liquid crystallinity) may be added to the mixture of the liquid crystal and the curable resin. Accordingly, the polymer in the polymer film can act to align the alignment direction of the liquid crystal molecules efficiently when voltage is applied. In addition, the disclination line occurring at the periphery of the liquid crystal region can be suppressed.
It is preferable that the selected liquid crystal material and the polymerizable liquid crystal material exhibit similar liquid crystal properties to each other. In particular, in F or Cl-based liquid crystal materials having different chemical environments, the polymerizable liquid crystal material is also preferably an F or Cl rP material.
Polymerizable liquid crystal materials that can be used include compounds represented by the following general formula (1).
In the formula (1), A is a polymerizable functional group such as CH 2 = CH-, CH 2 = CH-COO-, CH 2 = CCH 3 -COO-, and It represents a functional group which has unsaturated bond or distorted heterocyclic structure, such as these; B is a bonding group for bonding a polymerizable functional group and a liquid crystalline compound, for example, an alkyl chain (-(CH 2 ) N-), an ester bond (-COO-), an ether bond (-O-), and a polyethylene glycol chain (- A bonding group such as CH 2 CH 2 O-), and combinations thereof; LC represents a liquid crystalline compound. It is preferable that the bonding group B exhibit liquid crystallinity when the polymerizable liquid crystal material is mixed with the liquid crystal material. Thus, the bond group B has 6 or more bonds from the polymerizable functional group A to the hard part of the liquid crystalline material LC. The liquid crystal material LC is a compound represented by the following formula (2), a cholesterol ring, or a derivative thereof.
In Formula (2) G is a polar group such as a liquid crystal showing a dielectric anisotropy, such as -CN, -OCH 3, -Cl, -OCF 3, -OCCl 3, -H, and -R (R represents an alkyl group) Benzene rings, cyclohexane rings, paradiphenyl rings, and phenylcyclohexane rings having functional groups such as these. In addition, E is a functional group which binds D, G, and there are a single bond, -CH 2- , -CH 2 CH 2- , -O-, -C≡C-, and -CH = CH-. Finally, D is a functional group that binds to B, and is a part that determines the magnitude of dielectric anisotropy and refractive index anisotropy of liquid crystal molecules, such as a paraphenyl ring, a 1,10-diphenyl ring, a 1,4-cyclohexane ring, and 1,10-phenylcyclohexane ring, and the like.
[Mixing ratio of liquid crystal and polymerizable material]
The weight ratio of mixing the liquid crystal to the polymerizable material (including the curable resin and the polymerizable liquid crystal material) is 50:50 depending on the size of the appeal. 97: 3 is better and the more preferable range is 70:30 90:10. Liquid crystal material is 50 If less than this, the effect of the polymer wall is increased, the driving voltage of the cell is greatly increased, and there is no practical use. Liquid Crystal Material 97 As mentioned above, the physical strength of a polymer wall falls and stable performance is not acquired. The ratio of the polymerizable liquid crystal material in the total polymerizable materials in the above-mentioned ratio is 0.5 by weight. It is preferable to become above.
[Cell driving method]
The manufactured cell can be driven by simple matrix driving or an active matrix driving method using TFT or MTM. The driving method is not particularly limited in the present invention.
[Substrate material]
The substrate material furnace may be used as long as it is a transparent solid that can transmit visible light. In particular, glass, quartz, plastic, or polymer films can be used. Particularly suitable are plastic substrates which can form irregularities on the surface by embossing or the like. In addition, two kinds of different materials may be used to form a cell having a pair of substrates made of different materials. A pair of substrates made of the same material or different materials may have different thicknesses.
Now, Examples and Comparative Examples of the present invention will be described.
Referring to Figure 11, 1.1 On the pair of glass substrates 1 and 2 having a thickness of, transparent electrodes 3 and 6 made of ITO (a mixture of indium oxide and tin oxide: 500 kPa) are formed, respectively. On one glass substrate 1, a resist material (OMR 83 (manufactured by Tokyo Oka Kogyo Co., Ltd., Limited)) was used to form a convex portion 4 at the center of each pixel, and a first wall (on the pixel periphery). 5) were formed respectively. Under the resist, a light shielding layer of Mo thin film was formed. Hereinafter, the glass substrate 1 and the multilayer structure formed thereon are collectively referred to as a first substrate.
The other glass substrate 2 was coated with AL 4552 (manufactured by Japan Synthetic Rubber Company, Limited) to form an alignment layer 17 without rubbing treatment. The glass substrate 2 and the multi-layered structure formed thereon will be collectively referred to as a second substrate.
The first substrate and the second substrate, 6 corresponding to the cell thickness Sized spacers were sandwiched between them and attached to each other to form a cell.
In the cell, 0.1 g of R-684 (manufactured by Nippon Kayaku Co., Ltd.) as a photocurable resin, 0.1 g of p-phenylsterene as a photopolymerization inhibitor, 0.06 g of a compound having the structural formula (A) below, and a liquid crystal material ZLI-4792 [manufactured by Merck; 0.4 weight of S-811 Containing] 4.54 g and a mixture of 0.025 g of Irgacure 651 as a photopolymerization initiator were injected.
Thereafter, the temperature is 110, which is above the homogenization temperature of the mixture. And 2.5V, 60, in particular, between the electrodes 3,6. Under high pressure mercury lamp, applying a voltage of Of The resin was cured by irradiating ultraviolet light to the cell for 5 minutes from the first substrate 1 side at the position of. Then, the cell is 40 over 5 hours. And cooled to room temperature (25 After returning to), the cell was irradiated with ultraviolet light again to completely cure the resin.
As a result of observing the cells in this state with a polarization microscope, as shown in FIG. 2, the liquid crystal region 8 surrounded by the polymer wall 7 was formed in a mono-domain state for each pixel, It was shown that the liquid crystal molecules were axially symmetrically aligned with the portion 12 corresponding to the convex portion 4 as the symmetry axis. As a result, the cell appeared as if the position of the quenching shape 11 of the liquid crystal region was identical, and only the polymer wall 7 surrounding the pixel was rotated. This indicates that the droplet molecules are oriented on the whole axisymmetric.
Two polarizing plates whose polarization axes were orthogonal to each other were attached to both cells of the cell to produce a liquid crystal display device.
As a result of observing the liquid crystal display device thus produced under a flat microscope while applying voltage, it was confirmed that no disclination line was generated during application, and all pixels became black.
The evaluation of the electro-optical characteristics and the display unevenness of the thus produced liquid crystal display spores is shown in Tables 1 and 16 below. Table 1 also shows the results of Comparative Example 1 and Comparative Example 2 described later. Evaluation of the display unevenness obtained in Comparative Example 1 is shown in FIG. 17. The electro-optical characteristics blank two polarizing plates with the polarization axes parallel to each other (transmittance 100 ). In addition, in the "Reversal phenomenon at gray scale level" item of Table 1, a mark (circle) shows that inversion did not occur, The table shows a state where the reversal phenomenon can be easily observed, and the Δ table shows the state where the reversal phenomenon is barely observed.
Article 16 (a) Figures 16 (f) and 17 (a) As shown in FIG. 17 (f), the liquid crystal display device of Example 1 does not exhibit the inversion phenomenon as observed in the TN cell of Comparative Example 1, and increases the transmittance in the optical viewing direction during voltage saturation. Did not appear. In addition, as shown in Table 1, no display unevenness was observed at the gray scale level.
As in Example 1, a pair of glass substrates 1 and 2 in which transparent electrodes 3 and 6 made of ITO were formed were used. An orientation film was formed on both substrates, and rubbing was performed. This positive substrate, 6 corresponding to the cell thickness The spacers of the size were sandwiched between the substrates and attached to each other such that the alignment directions of the alignment films were perpendicular to each other to form a cell.
In the cell, the liquid crystal material ZLI-4792 (manufactured by Merck, Inc.) used in Example 1 weighed 0.4 wt. ), And the cells were attached to the outer surfaces of the two polarizing plates so that their polarization axes were perpendicular to each other, thereby producing a liquid crystal display device.
The evaluation of electro-optical characteristics and stains of the liquid crystal display device fabricated as described above are shown in Tables 1 and 17 (a). It is shown in FIG. 17 (f).
In the second embodiment, as shown in FIG. 12, the cell was fabricated in the same manner as in the first embodiment except that the recessed portion 15 was formed in the center of each pixel in the second embodiment. The same mixture as used in was injected into the space between the pair of substrates.
Between the transparent electrodes (3, 6) of the cell thus produced 2.5V, 60 The cell was heated to a temperature higher than the homogenization temperature of the mixture while applying a voltage of an effective voltage of. Thereafter, the cell was slowly cooled to precipitate the liquid crystal. After precipitation of the liquid crystal, voltage application was stopped. After the liquid crystal phase spread to almost all pixels, the cell was irradiated with ultraviolet light to cure the resin.
In the liquid crystal display device thus produced, it was observed that the liquid crystal molecules were oriented in the axisymmetric shape around the recessed portion 15 in the liquid crystal region. No visible stains were observed at the gray scale level.
In Example 3, the liquid crystal display device was manufactured in the same manner as in Example 1, except that the convex portion 4 was formed in the center of each pixel and the recessed portion 15 was formed around the convex portion 4. .
In the liquid crystal display device thus produced, it was observed that the liquid crystal molecules were oriented in the axisymmetric image centering on the convex portion 4 in the liquid crystal region. No visible stains were observed at the gray scale level.
In this embodiment 4, as shown in FIG. 5, in this embodiment 4, the spin coating of the alignment film 16 on the substrate 1 to cover the convex portion 4 and the first wall 5 is performed. The cell was produced in the same manner as in Example 1 except that it was formed by In addition, the same mixture as used in Example 1 was injected into the space between the pair of substrates. Curing of the resin was performed in the same manner as described in Example 2.
The phase separation process of the mixture of this example under gradual temperature drop was investigated, and the liquid crystal phase appeared in the region of thick cell thickness (concave portion 15) and spread out from the region. It was confirmed that the liquid crystal droplets were grown while being positioned and intentionally controlled so that the position of the axis of the axisymmetric alignment of the liquid crystal molecules coincided with the convex portion 4 of the center portion of the pixel. Such liquid crystal droplets formed in a region having a thicker cell thickness have a more spherical shape than liquid crystal droplets formed in a region having a thin cell thickness. Such spherical liquid crystal droplets have relatively little interfacial energy and are considered stable. Therefore, the liquid crystal phase appears from the region having the largest cell thickness, and the position of the axis of symmetry of the alignment of the liquid crystal molecules is limited.
In the fifth embodiment, as shown in FIG. 19, the rectangular pixel 13 is divided into two and the substrate 1 is made using black resist (CFPR-BK501S (manufactured by Tokyo Oka Kogyo Co., Ltd.). A cell was fabricated in the same manner as in Example 1 except that the first wall 21a and the convex portion 21b were formed thereon.
As a result of observing the cell thus fabricated with a polarization microscope, two liquid crystal domains in a monodomain state were formed in each pixel, and the liquid crystal molecules in each domain were aligned on the axis symmetrical with the symmetry axis of the part where the liquid crystal molecules were used in the convex portion 21b. Was observed.
In the liquid crystal display device thus fabricated, it was observed that the liquid crystal molecules were axially symmetrically oriented about the convex portion 21b in the liquid crystal region. No display unevenness was observed at the gray scale level.
In this Comparative Example 2, as shown in FIG. 20, the cell was fabricated in the same manner as in Example 1 except that the center portion of the pixel was flat in this example. The same mixture as used in Example 1 was injected into the space between the pair of substrates and cured as in Example 1.
As a result of observing the cell thus produced by a polarizing microscope, it was observed that most of the liquid crystal regions had an axisymmetric orientation. However, in some liquid crystal regions 8, the position of the axis of symmetry 18 is displaced as shown in FIG. 21 (a), while in another liquid crystal region 8, as shown in FIG. 21 (b). No axis of symmetry was formed. Further, no noticeable display unevenness is observed upon application of voltage, especially at the gray scale level.
In the sixth embodiment, as shown in Fig. 14 (a), except that the alignment film 16a having the axisymmetric alignment axis is formed on the substrate 1a in the sixth embodiment, Cells were fabricated in the same manner. The alignment film 16a was formed as follows.
Figure 14 (b) Referring to Fig. 14 (d), after forming the first wall 5 on the substrate 1a, the mixed material 22 containing two different polymer materials (such as polyimide) is prepared. It applied to the board | substrate 1a so that 1 wall 5 may be covered, it dried, and phase-separated, and baked.
On the substrate 1a, two conventional polymer materials were phase-separated from each pixel into an axisymmetric phase, whereby an alignment film 16a in which the axisymmetric phase had an orientation axis was obtained. A mixture containing a liquid crystal material and a curable resin material as described in Example 1 was injected into a space formed between a pair of substrates, and under the processing conditions as described in Example 1, the liquid crystal molecules were axially symmetrical. The liquid crystal display element orientated with the above was produced.
As a result of observing the thus-produced liquid crystal display device with a polarizing microscope, it was observed that the liquid crystal molecules were aligned in the axisymmetric phase with an alignment pattern substantially the same as the alignment weight of the alignment film 16a. At the gray scale level, no visible stain was observed.
In the seventh embodiment, in order to stably form the alignment side in the axisymmetric manner, the case where the convex portion formed in the center portion of the pixel is made of a material having vertical alignment is described.
As shown in FIG. 29, the glass substrate (thickness: 1.1 The convex part 52 was formed in the center part of the pixel on the board | substrate 51 which has the transparent electrode formed of ITO (mixture of indium oxide and tin oxide; thickness 500 micrometers) formed on the (). The convex portion 52 was made of a resist having a vertical orientation (resist obtained by adding a curable material to JALS 204). The first wall 53 was formed using a resist material (OMR 83 (manufactured by Tokyo Okagyo Kogyo Co., Ltd., Limited)) outside the pixel portion so as to surround the convex portion 52. At this time, a light shielding layer made of Mo thin film was formed under the resist. Subsequently, the substrate 51 and the structure formed thereon are collectively referred to as a first substrate.
AL 4552 (manufactured by Japan Synthetic Rubber Company, Limited) was applied to the other substrate 54 to form an alignment film 55 without performing a rubbing treatment. Hereinafter, the substrate 54 and the structure formed thereon are collectively referred to as a second substrate.
The first substrate and the second substrate, 5 corresponding to the cell thickness Sized spacers were sandwiched between them and attached to each other to form a cell. In the cell, 0.1 g of R-684 (manufactured by Nippon Kayaku Co., Ltd.), 0.1 g of p-phenylstyrene, 0.06 g of the compound of formula (A) described above, ZLI-4792 (from Merck) Manufactured; 0.4 weight S-811 ), And a mixture of 0.02 g of Irgacure 651 as a photopolymerization initiator was injected.
Then, the temperature of the cell 110 The cell was then cooled to room temperature, 5V, 60 While applying the voltage of the effective value of 50 60 Heated again. At this temperature, ON-OFF of the voltage was repeated, and the liquid crystal was oriented in the axisymmetric phase. The cell is then 30 over 7 hours. It was cooled slowly until.
In this state, liquid crystal molecules of each pixel were oriented in the axisymmetric image. This indicates that the convex portion of Example 7 made of a material having vertical alignment property is effective in improving stability of axisymmetric alignment of liquid crystal molecules. In this state, under high pressure mercury lamp Of Ultraviolet light was irradiated to the cell for 20 minutes from the first substrate side at the position of to cure the resin.
The cell may then be cooled to a temperature below room temperature and irradiated with ultraviolet light again to promote separation of the unreacted portion of the liquid crystal and the photocurable resin.
As a result of observing the thus prepared liquid crystal cell with a polarization microscope, as shown in FIG. 30, the liquid crystal molecules were axisymmetrically centered on the islands of the resist (iron parts made of a material having a vertical orientation) in a monodomain state for each pixel. It was oriented as. This axisymmetric orientation was observed in almost all liquid crystal regions.
Two polarizing plates whose polarization sides were orthogonal to each other were disposed on both outer surfaces of the cell to complete a liquid crystal display device surrounded by a polymer wall. As a result of observing the liquid crystal cell with a polarizing microscope while applying a voltage thereto, it was observed that even when voltage was applied, no disclination line was generated and all pixels became black.
Evaluation of the electro-optical characteristics and display unevenness of the produced liquid crystal cell is shown in Table 2 below. It can be seen from Table 2 that the liquid crystal cell of Example 7 does not exhibit the inversion phenomenon as observed in the TN cell, nor does it show an increase in transmittance in the wide visual direction at the time of voltage saturation. In this measurement, the two polarizing plates having the polarization axes parallel to each other were blanked (transmittance 100 ). No visible stains were observed at the gray scale level. In the "Reversal phenomenon at gray scale level" item in Table 2, a circle indicates that no reversal phenomenon has occurred.
This Example 8 shows the case where the high temperature exposure-slow cooling method is used as a method of manufacturing the liquid crystal cell of Example 7. As shown in FIG.
As described in Example 7, a mixture containing a liquid crystal material and a photocurable resin material was injected into the space portion between the pair of substrates. This cell is called the liquid crystal equalization temperature of 110 Heated to 10, then 10 While maintaining the temperature of 2.5V, 60 A voltage having an effective value of was applied between the transparent electrodes. At the same time, under the high temperature mercury lamp 10 Of Ultraviolet light was irradiated to the cell for 4 minutes from the first substrate side at the position of to cure the curable resin. 50 60 At the temperature, the voltage ON (above the voltage at which the liquid crystal operates) -OFF was repeated. Next, the cell over 30 hours 30 It was cooled slowly to the temperature of. The temperature is then room temperature (25 ), The ultraviolet-ray was irradiated to the cell again using the same ultraviolet irradiation device, and hardening of curable resin was completed.
Evaluation of the electro-optical characteristics and the display unevenness of the thus produced liquid crystal cell is shown in Table 2 above.
In the ninth embodiment, the case where the islands of two convex portions having the vertical alignment property are formed in the central portion of the pixel on the two substrates will be described.
Referring to FIG. 31, the convex portion 57 having the vertical alignment property is formed on one of the substrates as in the first substrate of Example 7, and on the alignment film of the other substrate at a position corresponding to the convex portion 57. The convex part 58 was formed in the. In this way, a liquid crystal cell was produced as in Example 7. In the produced liquid crystal cell, ie, the liquid crystal display element, the liquid crystal molecules were stably oriented in the axisymmetric state, and no display unevenness was observed at the gray scale level.
Example 7 In the ninth embodiment, liquid crystal molecules are axially oriented in each pixel with the central portion of the pixel as the center of symmetry. Since the liquid crystal molecules are oriented in all directions, deterioration of contrast along the viewing direction, which is a problem in the conventional liquid crystal display device, can be improved. Further, since an island having vertical alignment is formed in the center portion of each pixel, the axisymmetric alignment of the liquid crystal molecules is stabilized, and the position of the axis of the axisymmetric alignment in each pixel can be clearly determined. Thereby, it is possible to reduce the display unevenness seen when the time is changed. Thus, a wide-angle liquid crystal display device that provides a uniform and high contrast image can be realized.
Example 7 In the ninth embodiment, the convex portions having vertical alignment are formed in the center portion of each pixel, but instead of such concave portions, concave portions may be formed, or convex portions and concave portions may be formed.
In the tenth embodiment, an active driving element is formed on a substrate on which a convex portion or a concave portion for forming a stable axisymmetric alignment axis is formed for each pixel, and a color filter substrate is used as an opposing substrate thereof. Signal and the timing voltage of the counter voltage are applied.
As shown in FIGS. 27 and 28, Cr was deposited and patterned on the glass substrate 46 to form the gate wiring 44. Then, amorphous silicon was deposited by a plasma CVD apparatus so as to be a gate insulating film, and amorphous silicon was crystallized by laser annealing. The polysilicon was patterned into islands to form a semiconductor layer, and then P-doped amorphous silicon was deposited on the semiconductor layer by plasma CVD and patterned to cover the semiconductor layer. Then, ITO was deposited and patterned to form a pixel electrode. Thereafter, Cr and Al were deposited and patterned into predetermined shapes. These were etched in the order of Al, Cr, and P-doped amorphous silicon to form source and drain electrodes. Silicon nitride was deposited by plasma CVD to form a protective film. Finally, the protective film at the periphery of the substrate was etched to form an electrode lead-out portion to complete the TFT substrate. A resist material (OMR 83) was applied to this TFT substrate by spin coating. Covers the pixel electrode area and 10 from the center of each pixel The light-shielding mask to which the diameter area | region is exposed was overlaid on the board | substrate with which the resist was apply | coated, ultraviolet light was irradiated to the board | substrate from the light-shielding mask side, and the uncured part was etched. Thus, a wall 47 is formed in a region other than the pixel electrode, and 10 is formed in the center of the pixel electrode. A convex portion 48 of diameter was formed in a pattern of islands of resist.
As described above, the convex portions (or recesses) of the island pattern are formed on the surface of the liquid crystal region side of the first substrate. Thus, in each liquid crystal region, liquid crystal molecules can be axially symmetrically aligned with the convex portion or its vicinity as the vertical axis.
As for the second substrate, as shown in FIGS. 24 and 25, the light shielding film 32 was formed in the gap between the regions on the opposing substrate corresponding to the pixels formed on the first substrate. Then, a resin layer was formed in the regions, thereby forming a color filter unit 33 colored with R, G, and B regularly. A resist material (OMR 83) was applied to the second substrate thus produced by spin coating. Next, a light shielding mask exposing a region other than the color filter unit 33 was superimposed on the coated substrate, and the uncured portion was etched by irradiating ultraviolet light to the substrate from the light shielding mask side. Thus, regions other than the color filter portion 33 were filled with the resist resin 34 to planarize the surface. In other words, the color filter part 33 was formed on the board | substrate 31, and the remaining area | region other than the color filter part 33 was filled with the resist resin 34, and the surface was made flat.
As described above, in the liquid crystal display device in which liquid crystal molecules are axially symmetrically aligned in each pixel, the surface of at least one substrate (second substrate in the tenth embodiment) is flattened.
The first and second substrates thus fabricated were 6 as cell thickness. Spacers of size were sandwiched between the substrates and attached to each other to form a cell. Certain locations on the first and second substrates are not covered with resist to form ITO electrodes for electrical connection, and these electrodes are electrically connected with carbon paste (TU-100-5S; manufactured by Asahi Kagaku Corporation). do. A mixture containing the liquid crystal material and the curable resin material described in Example 1 was injected into the cell. 110 cells While maintaining this temperature, the signal voltage shown in FIG. , A square wave voltage of 2.5 V, duty 1/2 is applied, and the frequency is 120 in synchronization with the gate electrode source voltage. , A square wave voltage with a time range of 60V and 60V for the other 10V is applied. At the same time, the light intensity is 10 from pneumatic mercury lamps. Of Ultraviolet light was irradiated to the cell from the first substrate side to cure the curable resin. Thereafter, the cell was 40 over 5 hours. Slow cooled to room temperature (25 ), The cell was irradiated with ultraviolet light again using the same ultraviolet irradiation device to complete curing of the curable resin.
As a result of observing the thus produced liquid crystal cell with a polarizing microscope, as shown in FIG. 2, it was observed that the liquid crystal molecules were axially symmetrically oriented about islands of the resist in a monodomain state for each pixel. This axisymmetric orientation has been achieved in almost all liquid crystal regions. The evidence is that when the two polarizing plates of which the polarization axes are orthogonal to each other are fixed and the liquid crystal cell is rotated, the position of the Schlierene pattern in the liquid crystal region is constant and only the polymer wall 7 around the pixel appears to rotate. Judging from the facts.
Two polarizing plates whose polarization axes were orthogonal to each other were disposed on both outer surfaces of the liquid crystal cell to complete a liquid crystal display cell surrounded by a polymer wall. As a result of observing the cell with a polarizing microscope while applying a voltage thereto, it was observed that even when voltage was applied, the disclination line did not occur and all the pixels became black. This liquid crystal cell did not show the inversion phenomenon as observed in the TN cell (Comparative Example 1), nor did it show an increase in transmittance at the wide time at voltage saturation. In this measurement, the two polarizing plates of which the polarization axes are parallel to each other are blanked (transmittance 100 ). No visible stains were observed at the gray scale level.
Typically, there is a need between adjacent color filter parts. At the time of phase separation of the liquid crystal and the curable resin, the liquid crystal tends to be precipitated at the portion where the cell thickness is thick. Therefore, since liquid crystal droplets tend to be formed in the request between the color filter portions, the axisymmetric orientation of the liquid crystal molecules is inhibited by the recesses. This problem can be solved by filling the recess with a resist material to planarize the surface of the color filter substrate. By this flattening treatment, the liquid crystal can be separated only at the convex portions of the substrate on the opposite side. In the case of the active drive element, many end portions are formed by the multi-layered structure of the active drive element and its wiring portion, and thus the axisymmetric orientation of the liquid crystal molecules in the liquid crystal droplets is hindered. This problem can be solved by filling the recessed portion formed by this end with a resin to flatten the surface.
The signal voltage for driving the gate of the active driving element is synchronized with the signal voltage for driving the source of the active driving element, and the pulse width of the gate driving signal voltage is less than half the period of the source driving signal voltage. The resin is cured while being applied. Therefore, the problem that the potential difference between the pixel electrode and the gate wiring on the same substrate is reduced, and the problem that the axisymmetric orientation of the liquid crystal molecules is disturbed due to the potential of the gate wiring can be solved.
As described above, in the liquid crystal display device of this embodiment, the position of the axis of the axisymmetric alignment of the liquid crystal molecules can be clearly determined, the display unevenness observed when changing the vision can be minimized, and a uniform and high contrast image is provided. A wide viewing angle liquid crystal display device can be realized.
Thus, according to the present invention, the liquid crystal molecules in each liquid crystal region are axially symmetrically aligned. Therefore, the variation in contrast seen in the conventional liquid crystal display device can be minimized. Since the position of the axis of symmetry in each pixel can be controlled and the axis of symmetry can be perpendicular to the substrate, the display unevenness observed when changing the vision can be reduced. Thus, a wide-angle liquid crystal display device that provides a uniform and high contrast image can be realized. Moreover, disclination lines are formed outside the pixels or become less visible. By this, the display quality can be improved.
In addition, as islands having vertical alignment, convex portions or concave portions are formed in the center portion of each pixel. Therefore, axisymmetry is stabilized, and the position of the axis of axisymmetric orientation in each pixel can be clearly determined. This reduces the display unevenness observed when the time of day is changed. In addition, a wide-angle liquid crystal display device that provides a uniform and high contrast image can be realized.
Furthermore, by planarizing the surface of the electrode substrate directed to the other substrate, the orientation of the liquid crystal droplets is prevented from being disturbed by recesses on the substrate. For example, when a color filter is formed on an electrode substrate, resin is filled in the recesses between the color filter portions to make the surface flat. Thus, the liquid crystal phase appears only in the recesses or convex portions formed on the other substrate facing the color filter. As another embodiment, when the active driving element is formed on the electrode substrate, many ends are formed on the surface by the multilayer structure of the active driving element and its wiring portion. Even in this case, the ends thereof are filled with resin in order to flatten the surface. Thus, the liquid crystal phase appears only in the recesses or convex portions formed in the central portion of each pixel. Therefore, the position of the axis of the axisymmetric alignment in each pixel can be clearly determined, the display unevenness observed when changing the vision can be minimized, and a wide-angle liquid crystal display device providing a uniform and high contrast image can be realized. .
The gate driving signal voltage of the active driving element is synchronized with the source driving signal voltage of the active driving element, the period of the gate driving signal voltage is half of the period of the source driving signal voltage, and the pulse width of the gate driving signal voltage is the source. It is less than half of the period of the drive signal voltage, and the resin is cured while applying a voltage. Since the gate signal wiring is arranged near each pixel electrode, the potential of the gate signal voltage affects the potential near the pixel electrode. When the time of the signal voltage applied to the gate electrode is shorter than the time when the source driving signal voltage is applied to the pixel electrode, the potential near the pixel electrode is less affected by the gate signal voltage. Therefore, the potential difference between the pixel electrode and the gate wiring on the same substrate can be alleviated, and the problem that the axisymmetric orientation can be disturbed by the potential of the gate wiring can be eliminated. Therefore, the position of the axis of the axisymmetric alignment of the liquid crystal in each pixel can be clearly determined, the display unevenness observed when changing the time can be minimized, and a wide viewing liquid crystal display device providing a uniform and high contrast image can be realized. have.
In Example 11, a method of simply forming recesses in the color filter portion to control the position of the axis of symmetry of the alignment of the liquid crystal molecules will be described.
Figure 33 (a) Referring to Fig. 33 (e), a method of manufacturing the color filter substrate 60 of this embodiment will be described.
First, as shown in FIG. 33 (a), the color filter 63 is formed on the substrate 62. FIG. The color filter 63 has color filter portions 63a, 63b, 63c corresponding to red (R), green (G), and blue (B), respectively. The color filter portions are formed to correspond to the respective pixels. In the present invention, the method for forming the color filter 63 is not particularly limited, and an electrodeposition method, a film deposition method, a printing method, a color-resist method and the like can be used.
Next, as shown in FIG. 33 (b), a resist 64 is applied onto the substrate 62 to cover the color filter portions 63a, 63b, and 63c. Thereafter, as shown in FIG. 33 (c), the resist 64 is exposed and developed so that the convex wall 65 made of resist can be formed in a portion (a region other than the color filter portion) outside the pixel portion. . It is important that the convex wall 65 formed on the substrate 62 be higher than the color filter portions 63a, 63b, 63c so as to protrude further toward the liquid crystal layer.
A thin overcoat layer 66 is then formed over the substrate 62 with the convex walls 65, as shown in FIG. 33 (d). Due to the surface tension (meniscus) of the liquid overcoat material and the protrusion of the convex wall 65, recesses (conical portions) are formed on the respective color filter portions 63a, 63b, 63c. As shown in FIG. 33 (e), a transparent electrode 67 is formed on the overcoat layer 66 formed on the substrate 62. If necessary, an insulating layer, an alignment film, or both may be formed on the transparent electrode 67. In this way, the color filter substrate 60 is produced.
[Overcoat material]
As the material for forming the recesses, conventional overcoat materials can be used. In the present invention, the overcoat layer is covered with the transparent electrode and finally remains in the liquid crystal cell. Therefore, it is preferable to use polyimide, epoxy acrylate, etc. which are excellent in heat resistance as an overcoat material.
It is preferable that the number of domains in each pixel is as small as possible. If a plurality of domains exist in one pixel, a disclination line is formed at each boundary of the domains, thereby lowering the black level of the display. Therefore, it is preferable that the pixel portion is covered by a single domain in which liquid crystal molecules are arranged in axisymmetry. In this case, since the domain is formed on the outer circumference of the disc when the voltage is applied, it rarely invades the inside of the pixel portion.
As shown in FIG. 3, when a color liquid crystal display element having rectangular pixels 13 is fabricated according to the method of Example 11, the liquid crystal region 8 has liquid crystal molecules in the axially symmetrical form in each domain. It may have two or more liquid crystal domains 14a and 14b arranged. In this case, two color filter parts are formed so as to correspond to the two liquid crystal domains 14a and 14b in the pixel 13. Thereafter, Figure 33 (a) According to the process shown in FIG. 33 (e), corresponding to the two liquid crystal domains 14a and 14b in the pixel 13, a main portion for controlling the position of the axis of symmetry of the alignment of the liquid crystal molecules can be formed. It is also possible to impart light blocking properties to the material forming the convex wall 65 so that the convex wall 65 functions as a black mask BM.
The substrate 62 may be made of a transparent solid that transmits visible light. In particular, glass, quartz, plastics and the like can be used.
Now, a method of manufacturing the color filter substrate 60 of Example 11 is shown in FIG. 33 (a). This will be described in more detail with reference to FIG. 33 (e).
Organic substrate 62 using killer resist (thickness: 1.1 ), Color filter portions 63a, 63b, 63c corresponding to R, G, and B are formed in each pixel. Then, a resist 64 (V259PA (manufactured by Nippon Steel Chemical Company, Limited)) is applied to the substrate 62 so as to cover the color filter portions 63a, 63b, and 63c. The resist 64 is exposed and developed so that a convex wall 65 made of resist is formed outside the pixel. Its convex wall 65 is about 1 more than the pixel part It is formed so as to protrude. A thin overcoat layer 66 (V259 (manufactured by Nippon Steel Chemical Company, Limited)) is formed on the substrate 62 with the convex walls 65 to form conical recesses on the pixel portion. Then, on this substrate 62, 50 A transparent electrode 67 made of ITO (a mixture of indium oxide and tin oxide) having a thickness of is formed, and an insulating film SiO 2 is formed thereon.
As a comparative example 3, the color filter substrate 70 shown in FIG. 34 was produced as follows. As in the case of the color filter substrate 60 of the eleventh embodiment described above, after the color filter portion 63 is formed on the glass substrate 62, the color filter portion 63 is covered on the substrate 62. Thick overcoat layer 66 was formed. In order to obtain a flat surface directed to the liquid crystal, the surface of the overcoat layer 66 was polished, and a transparent electrode 67 was formed on the overcoat layer 66 to complete the color filter substrate 70.
As a comparative example 4, the color filter substrate 80 shown in FIG. 35 was produced as follows. The color filter substrate 80 has recesses between the adjacent color filter portions 63.
First, as in the color filter substrate 60 described above, the color filter unit 63 is formed on the glass substrate 62. Then, a thin overcoat layer 66 was formed on the substrate with the color filter portion 63 without filling the adjacent color filter portions 63 with a resist. Since the overcoat layer 66 is thin, recessed portions were formed between the color filter portions 63. A transparent electrode 67 was formed on the overcoat layer 66 to complete the color filter substrate 80.
On the other hand, a substrate having a TFT (TFT substrate) was fabricated, and a resist wall made of resin material (OMR 83 (manufactured by Tokyo Oka Kogyo Co., Ltd., Limited)) was formed around each pixel on the TFT substrate. Beads for keeping the cell thickness constant were incorporated into the resist wall in such a way that no bead surface would come out of the resist wall.
The liquid crystal cells of Example 11 and Comparative Examples 3 and 4 were produced using the color filter substrates 60, 70, 80 and TFT substrates, respectively.
0.1 g of R-684 (manufactured by Nippon Kayaku Co., Ltd.), 0.1 g of p-phenylstyrene, 0.06 g of the compound of formula (A) described above, ZLI-4792 (manufactured by Merck, Inc.) as a liquid crystal material; S 0.4 Weight -811 Containing) 2.74 g and 0.02 g of Irgacure 651 as a photoinitiator were mixed, and the mixture of an ultraviolet curable resin and a liquid crystal was obtained. The obtained mixture was injected into the liquid crystal cell described above.
The liquid crystal cell is 100 to maintain the homogeneous state of the mixture. Was maintained. The cell was then cooled to cause phase separation of the mixture. After the phase separated liquid crystal phase spread to all the pixels, the cell was heated again. 5 V, 60 between the electrodes of the cell with the size of the liquid crystal region about 1/4 of the pixel size The voltage of the effective value of was applied. Then, the voltage was gradually lowered. As a result, the orientation of the liquid crystal molecules in the liquid crystal region became the axisymmetric alignment state.
Chapter 36 (a) 36 (c) shows how the liquid crystal phase was precipitated from the curable resin in Example 11 and Comparative Examples 3 and 4, respectively. The liquid crystal region tends to be formed in a portion where the cell thickness is thick. Therefore, in the eleventh embodiment, the liquid crystal region is formed in the center of the pixel as shown in Fig. 36 (a). On the other hand, in the comparative example 3, as shown in FIG. 36 (b), the position where a liquid crystal region is formed is not constant but changes for every pixel. In Comparative Example 4, as shown in FIG. 36 (c), the liquid crystal region partially extends into the pixel and is formed outside the pixel.
After that, the cell was cooled to room temperature, and the high pressure water lamp was used. Of The ultraviolet light of the light intensity of was irradiated to the cell from the TFT substrate side for 30 minutes to cure the curable resin.
Chapter 37 (a) 37 (c) shows the result of observing the obtained cell with a polarizing microscope.
In Example 11, as shown in FIG. 37 (a), the position of the axis of symmetry of the alignment of the liquid crystal molecules is controlled to the center of each pixel in all the pixels. In Comparative Example 3 The symmetry axis of the axisymmetric orientation of the liquid crystal molecules in the pixel of was largely displaced as shown in Fig. 37 (b). As a result, in Example 11, display unevenness was not observed and good display quality was obtained. In Comparative Example 3, display unevenness was observed at a gray scale level and a low viewing angle. In Comparative Example 4, the liquid crystal molecules were approximately 30 of all pixels. Since only the pixel of was oriented axially symmetrically, the heavily stained display was obtained.
According to this embodiment, the liquid crystal display element has a recessed portion in the color filter provided in each pixel. Liquid crystal molecules are aligned in axisymmetric with the center of each pixel as the symmetry axis. Thus, the position of the axis of the axisymmetric alignment of the liquid crystal molecules in each pixel can be clearly determined, the display unevenness observed when changing the time can be minimized, and a wide-angle liquid crystal display device providing a uniform and high contrast image is realized. Can be. Moreover, the killer filter portion according to the present invention can be manufactured in the same manufacturing process as in the conventional color filter portion, thereby providing an excellent price performance ratio.
Various other modifications will be apparent to those skilled in the art and such modifications can be readily made by them without departing from the scope and spirit of the invention. Therefore, the scope of the claims appended hereto should not be limited to the description herein, but rather the claims should be construed broadly.
A pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are formed in a liquid crystal element sandwiched by the pair of electrode substrates. At least one of the convex portions is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and the liquid crystal molecules are an axis perpendicular to the electrode substrate and in the vicinity of at least one of the recesses and the convex portions. A liquid crystal element oriented in the liquid crystal region in axisymmetric.
A pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the highly fragmented wall, wherein the polymer wall and the liquid crystal region are faced with the liquid crystal region in a liquid crystal element sandwiched by the pair of electrode substrates. A main column is formed on at least one surface of a pair of electrode substrates, and the liquid crystal molecules are aligned in the liquid crystal region in the axisymmetrical vicinity of the main part with an axis perpendicular to the electrode substrate.
A pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region are formed in a liquid crystal element sandwiched by the pair of electrode substrates. At least one of the convex portions is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and a liquid crystal molecule is an axis perpendicular to the electrode substrate, in the vicinity of at least one of the recessed portions and the convex portions. And a flattened resin portion formed on one or both surfaces of the pair of electrode substrates oriented in the liquid crystal region with axis symmetry and facing the liquid crystal region.
A liquid crystal region surrounded by an opposite pair of electrode substrates, a polymer wall, and the polymer wall, wherein the polymer wall and the liquid crystal region are sandwiched by the pair of electrode substrates. The main portion is formed on at least one surface of the pair of electrode substrates, and the liquid crystal molecules are axially symmetrically oriented in the vicinity of the main portion as the axis perpendicular to the electrode substrate, and the surface facing the liquid crystal region. A liquid crystal element in which a flattened resin portion is formed on one or both surfaces of a pair of electrode substrates.
4. The liquid crystal device of claim 3, wherein a color filter is formed on at least one of the pair of electrode substrates, and is filled with a resin to form recesses and resin portions between the color filter portions of the color filter corresponding to the liquid crystal region. .
4. The method of claim 3, wherein an active driving element for driving a liquid crystal by applying a driving voltage to an electrode of the electrode substrate is formed on at least one of the pair of electrode substrates, and the active driving element and the wirings are formed of resin. A liquid crystal device covered with a resin and flattened.
The liquid crystal device according to claim 1, wherein at least one of the recessed portion and the convex portion is formed of a film having vertical alignment characteristics or horizontal alignment characteristics.
The liquid crystal device of claim 1, wherein the liquid crystal region is composed of a plurality of liquid crystal domains that divide one pixel, and a polymer wall is formed around each of the plurality of liquid crystal domains.
The liquid crystal device of claim 8, wherein a colored additive is included in the polymer wall.
The liquid crystal device according to claim 1, wherein recesses and convex portions are formed axially or continuously near a symmetry axis for orientation of the liquid crystal molecules.
The liquid crystal device according to claim 1, wherein a region where a distance between electrodes of the pair of electrode substrates is different from a distance in the other regions exists near a symmetry axis for orientation of the liquid crystal molecules.
A first wall is formed on at least one surface of the pair of substrates facing the liquid crystal region so as to surround the liquid crystal region or the liquid crystal domain, and the height H of the first wall and the convex portion are formed. The height h is a liquid crystal element having a relationship of H> h.
A pair of opposing electrode substrates, a polymer wall, and a liquid crystal region surrounded by the polymer wall, wherein the polymer wall and the liquid crystal region have an axisymmetric alignment axis in the liquid crystal element sandwiched by the pair of electrode substrates. An alignment film made of high rich is formed on at least one surface of the pair of electrode substrates facing the liquid crystal region, and the liquid crystal molecules are axisymmetrically in the vicinity of at least one of the recesses and the convex portions as an axis perpendicular to the electrode substrate. Liquid crystal element oriented in the pixel
2. The apparatus of claim 1, wherein at least one of the electrode substrates has a color filter, the color filter includes a plurality of color filter portions corresponding to a plurality of pixels, and the recessed portion is formed on a surface of each color filter portion facing the liquid crystal region. Formed liquid crystal element.
15. The liquid crystal device according to claim 14, wherein at least one of the electrode substrates includes a convex wall formed between the plurality of color filter portions, and an overcoat layer covering the plurality of color filters and the convex wall.
The liquid crystal device of claim 15, wherein the convex wall has light blocking characteristics.
A first wall is formed on at least one of the pair of electrode substrates, and at least one of recesses and convex portions is formed in the center of the region surrounded by the first wall, or in the center of the region surrounded by the first wall. Forming an alignment film having at least one of recesses and recesses, and arranging the pair of electrode substrates so as to face each other; Injecting a mixture containing at least a liquid crystal and a curable resin into the cell; And hardening the curable resin at a temperature equal to or higher than the homogenization temperature of the mixture to phase-separate the liquid crystal from the curable resin.
A first wall is formed on at least one of the pair of electrode substrates, and at least one of recesses and convex portions is formed in the center of the region surrounded by the first wall, or in the center of the region surrounded by the first wall. Manufacturing a cell by forming an alignment film having at least one of recesses and recesses and arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And first heating the mixture to a homogenization temperature of the mixture, followed by slow cooling of the mixture to phase-separate the liquid crystal from the curable resin, and curing the curable resin.
A first wall is formed on at least one of the pair of electrode substrates, and at least one of recesses and convex portions formed of a film having a vertical alignment characteristic or a horizontal alignment characteristic is formed in a central portion of the permanent region surrounded by the first wall; Manufacturing a cell by arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And heating the mixture to a homogenization temperature of the mixture, curing the curable resin by exposure, and then slowly cooling the mixture.
An alignment film having an axisymmetric alignment side is formed by forming a first wall on at least one of the pair of electrode substrates, and phase-separating a mixed material including a polymer material of two or more different shapes in a region surrounded by the first wall. Forming a cell by arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And curing the curable resin above the homogenization temperature of the mixture and phase separating the curable resin into liquid crystal from the curable resin.
A first wall is formed on at least one of the pair of electrode substrates, and a mixed material including polymer materials of two or more different shapes is separated in a region surrounded by the first wall to form an alignment layer having an axisymmetric alignment axis. Then, manufacturing the cell by arranging the pair of electrode substrates to face each other; Injecting at least a mixture of liquid crystal and curable resin into the cell; And first heating the mixture to a homogenization temperature of the mixture, slowly cooling the mixture to phase separate the liquid crystal from the curable resin, and curing the curable resin.
18. The method of claim 17, wherein the curable resin is cured while applying at least one of a voltage and a magnetic field to the cell.
23. The gate driving circuit of claim 22, wherein an active driving element for driving a liquid crystal by applying a voltage to electrodes of the electrode substrates is formed on one side of the pair of electrode substrates, and the gate is applied to the active driving element when the curable resin is cured. And a driving signal voltage is synchronized with a source driving signal voltage applied to the active driving device, and the duty ratio of the gate driving signal voltage is less than 1/2 of the duty ratio of the source driving signal voltage.
A pair of electrode substrates facing each other, a polymer wall, and a liquid crystal region surrounded by the polymer film, wherein the polymer wall and the liquid crystal region are a manufacturing method of a liquid crystal element sandwiched by the pair of substrates. At least one of the board | substrates is a process of forming a some color filter part in the surface of the said board | substrate; Forming a convex wall between the color filter portions; And forming recesses on surfaces of the plurality of color filter units.
25. The method of claim 24, wherein the forming of the recesses comprises: applying a resist covering the plurality of color filter portions; And exposing and developing the resist to form convex walls between the plurality of color filter portions.
4. The liquid crystal device according to claim 3, wherein at least one of the recessed portion and the convex portion is formed of a film having vertical alignment characteristics or horizontal alignment characteristics.
3. The liquid crystal device of claim 2, wherein the liquid crystal region is composed of a plurality of liquid crystal domains dividing one pixel, and a polymer wall is formed around each of the plurality of liquid crystal domains.
4. The liquid crystal device according to claim 3, wherein the liquid crystal region is composed of a plurality of liquid crystal domains dividing one pixel, and a polymer wall is formed around each of the plurality of liquid crystal domains.
The liquid crystal device according to claim 4, wherein the liquid crystal region is composed of a plurality of liquid crystal domains dividing one pixel, and a polymer wall is formed around each of the plurality of liquid crystal domains.
29. The liquid crystal device of claim 28, wherein a colored additive is included in the polymer wall.
4. The liquid crystal device according to claim 3, wherein recesses and convex portions are formed axially or continuously near the symmetry axis for the alignment of the liquid crystal molecules.
4. The liquid crystal device according to claim 3, wherein an area in which the distance between the electrodes of the pair of electrode substrates is different from the distance in the other areas exists near the axis of symmetry for the alignment of the liquid crystal molecules.
The first wall is formed on at least one surface of the pair of substrates facing the liquid crystal region so as to surround the liquid crystal region or the liquid crystal domain, and the height H of the first wall and the convex portion are defined. The height h is a liquid crystal device having a relationship of H> h.
19. The method of claim 18, wherein the curable resin is cured while applying at least one of a voltage and a magnetic field to the cell.
20. The method of claim 19, wherein the curable resin is cured while applying at least one of a voltage and a magnetic field to the cell.
21. The method of claim 20, wherein the curable resin is cured while applying at least one of a voltage and a magnetic field to the cell.
The method of claim 21, wherein the curable resin is cured while applying at least one of a voltage and a magnetic field to the cell.
35. The gate driving circuit of claim 34, wherein an active driving element for driving a liquid crystal by applying a voltage to electrodes of the electrode substrates is formed on one side of the pair of electrode substrates and is applied to the active driving element when the curable resin is cured. And a driving signal voltage is synchronized with a source driving signal voltage applied to the active driving device, and the duty ratio of the gate driving signal voltage is less than 1/2 of the duty ratio of the source driving signal voltage.
36. The gate driving circuit of claim 35, wherein an active driving element for driving a liquid crystal by applying a voltage to electrodes of the electrode substrates is formed on one side of the pair of electrode substrates and is applied to the active driving element when the curable resin is cured. And a driving signal voltage is synchronized with a source driving signal voltage applied to the active driving device, and the duty ratio of the gate driving signal voltage is less than 1/2 of the duty ratio of the source driving signal voltage.
37. The gate of claim 36, wherein an active driving element for driving a liquid crystal by applying a voltage to electrodes of the electrode substrates is formed on one side of the pair of electrode substrates and is applied to the active driving element when the curable resin is cured. And a driving signal voltage is synchronized with a source driving signal voltage applied to the active driving device, and the duty ratio of the gate driving signal voltage is less than 1/2 of the duty ratio of the source driving signal voltage.
38. The gate driving circuit of claim 37, wherein an active driving element for driving a liquid crystal by applying a voltage to electrodes of the electrode substrates is formed on one side of the pair of electrode substrates and is applied to the active driving element when the curable resin is cured. And a driving signal voltage is synchronized with a source driving signal voltage applied to the active driving device, and the duty ratio of the gate driving signal voltage is less than 1/2 of the duty ratio of the source driving signal voltage.
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