JPH1115004A - Electrooptical device and production therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly hold a cell gap without using particle shaped spacers in the electrooptical device of a simple matrix driving system. SOLUTION: Stripe shaped reflection electrodes 110, 210 and oriented films 120, 220 are respectively formed on glass substrates 100, 200. Moreover, cell gap holding members 300 for holding a cell gap are provided on the glass substrate 100. After insulative coated film surfaces formed on the electrodes 110 are flattened by a chemical and mechanical grinding method, the gap cell holding members 300 are formed by being patterned. Since the cell gap holding members 300 are fixed to the substrate 100 and heights of them are made uniformly, they can hold the cell gap uniformly on the whole of the substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device of a simple matrix drive system and a method of manufacturing the same, which relates to means for maintaining a substrate gap (cell gap) of the display device.

[0002]

2. Description of the Related Art There are two types of matrix type liquid crystal display devices, a simple matrix type and an active matrix type. In the structure of the simple matrix liquid crystal display device, a substrate having a stripe electrode in the X direction and a substrate having a stripe electrode in the Y direction sandwich a liquid crystal layer. In the simple matrix, a voltage is directly applied to the liquid crystal by the opposing XY electrodes.

On the other hand, the active matrix type liquid crystal display device has an active element having a switching function in each pixel, and has a structure in which the active element controls on / off of a voltage applied to an electrode.
In general, the active matrix is superior in terms of image quality, but the simple matrix has a very simple structure as described above, and thus has excellent cost performance.

Further, in an electro-optical device such as a liquid crystal display device, a rod-shaped or spherical spacer is used in order to secure an interval (cell gap) between two substrates. The size of the cell gap is the thickness of the liquid crystal layer, and the thickness of the liquid crystal layer greatly affects characteristics of the liquid crystal display device such as color tone, contrast, and response speed.

[0005]

Conventionally, as a method of arranging a spacer for securing a cell gap on a substrate, there is a method of spraying on a substrate surface, and a method of printing an alignment film together with an alignment film material when printing the alignment film. .

[0006] However, it is difficult to completely prevent the dispersion density of the spacers from fluctuating by any of the spraying method and the printing method. For this reason, there arises a problem that the cell gap differs from place to place. In addition, there is a problem that the dispersion density of the spacer varies for each substrate, and the cell gap varies for each display device. In addition, there is a possibility that a plurality of spacers may be aggregated, and a plurality of aggregated spacers may be visually recognized as point defects.

In addition, when the liquid crystal is injected, there is a problem that the granular spacer is likely to flow due to the flow of the liquid crystal, the dispersion density is uneven, and the particles are aggregated.

In addition, since standard spacers are generally used, it is difficult to arbitrarily determine a cell gap. Generally, the cell gap of a liquid crystal display device manufactured or prototyped is about 4 to 6 μm for a transmission type and about 2 to 3 μm for a reflection type. In addition, a liquid crystal display device using a ferroelectric liquid crystal or an antiferroelectric liquid crystal, which has recently attracted attention, requires a fine cell gap of 2 μm or less due to its characteristics.

A ferroelectric liquid crystal has characteristics such as no crosstalk, a large viewing angle, and a high-speed switching characteristic that is three orders of magnitude faster than an STN liquid crystal, and can realize high definition and a large screen even with a simple matrix. In a liquid crystal panel using a ferroelectric liquid crystal, it is necessary to cancel the helical structure of the ferroelectric liquid crystal and to orient the liquid crystal.

[0010] However, in the conventional granular spacer, maintaining such a fine cell gap is difficult.
Very difficult. For example, in order to maintain a fine cell gap, the spherical spacers are also fine, and it is difficult to obtain a spacer having a very uniform grain size. Also, it is difficult to uniformly disperse and arrange the spacers one by one.

An object of the present invention is to provide a simple matrix type driving type electro-optical device having a cell gap holding member different from a conventional spacer and a method of manufacturing the same to solve the above-mentioned problems.

[0012]

In order to solve the above-mentioned problems, an electro-optical device according to the present invention is an electro-optical device of a simple matrix driving system having two opposing substrates. At least one is provided with a gap holding member for holding the gap between the pair of substrates, and a surface of the gap holding member facing the other substrate is flattened by chemical mechanical polishing. And

Further, in order to solve the above-mentioned problems, a method of manufacturing an electro-optical device according to the present invention is directed to a method of manufacturing an electro-optical device of a simple matrix type having two opposing substrates. Forming an electrode on each of the two substrates; and forming an insulating coating on the electrodes for at least one of the two substrates;
A step of chemically and mechanically polishing the surface of the insulating coating,
Patterning the polished insulating film to form a gap holding member for holding the gap between the pair of substrates.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic perspective view of an electro-optical device of a simple matrix driving system according to the present embodiment.

As shown in FIG. 1, opposing substrates 100,
200 has striped electrodes 110 and 21 respectively.
0, alignment films 120 and 220 are provided. Further, on the substrate 100 side, a cell gap holding member 300 is provided in order to maintain an interval (cell gap) between the substrates 100 and 200.
Is provided. The cell gap holding member 300 is an alternative to a conventional spacer, and is formed of an insulating material, and a plurality of the cell gap holding members are dispersedly provided over the entire substrate 100.

The cell gap holding member 300 is formed of the alignment film 12.
Formed before 0 is formed. The step of forming the cell gap holding member 300 is performed by using the substrate 10 on which the electrode 110 is formed.
The method includes a step of forming an insulating film on the substrate, flattening the surface of the insulating film by a chemical mechanical polishing method, and then patterning the surface.

As the insulating coating material constituting the gap holding member 300, a resin material having a specific gravity close to that of liquid crystal and a thermal expansion coefficient is preferable. For example, a resin material selected from polyimide, acrylic, polyamide or polyimide amide can be used. In addition, an ultraviolet curable resin or a thermosetting resin material which can be formed with little thermal influence on the substrate can be used.

As a method of patterning the insulating film, an etching method can be used. In the present embodiment, since the lower structure of the insulating film has a very simple structure, it is easy to obtain an etching selectivity with the insulating film, and the material of the insulating film has a wide selection range. As another patterning method, a method in which an insulating film is formed from a photosensitive material, and patterning is performed by exposure and development processing can be used.

The cell gap holding member 300 has a columnar shape, and a surface 300a facing the other substrate 200 is flattened by chemical mechanical polishing. For this reason, even if the substrates are bonded, generation of undulation can be suppressed or prevented. Further, the height of the cell gap holding member 300 can be appropriately set by the polishing process. Therefore 3
It is possible to uniformly and accurately hold even a narrow cell gap of not more than 2 μm, not more than 2 μm. The formation position and the number of the cell gap holding members 300 may be determined so that the cell gap can be held and display is not hindered.

[0020]

【Example】

Embodiment 1 In this embodiment, an example in which the present invention is applied to an STN reflective liquid crystal panel will be described. FIG. 1 is a schematic perspective view of the liquid crystal panel of the present embodiment. As shown in FIG. 1, a glass substrate 100 is provided with a stripe-shaped reflective electrode 110, an alignment film 120, and a cell gap holding member 300 that is distributed evenly over the entire substrate 100 and holds a cell gap. . On the other hand, the transparent electrode 21
0, an alignment film 220 is provided. Glass substrate 100
And 200 are opposed to each other with the alignment films 120 and 220 inside. The gap between the glass substrates 100 and 200 is secured by the cell gap holding member 300, and an STN liquid crystal (not shown) is sealed in the gap between the substrates.

Hereinafter, a method of manufacturing the reflection type liquid crystal panel of this embodiment will be described with reference to FIGS. First, a metal film forming the reflective electrode 110 is formed on the glass substrate 100. In this embodiment, an aluminum film is formed to a thickness of 400 nm by a sputtering method, and is patterned.
A stripe-shaped reflective electrode 110 is formed. Reflective electrode 1
Reference numeral 10 denotes a structure extending in a direction perpendicular to the paper surface (FIG. 2A).

Next, a film 10 made of an insulating material for forming the cell gap holding member 130 is formed. In this embodiment, the photosensitive polyimide film 10 is formed to a thickness of 3.5 μm by spin coating, and left (leveling) for 30 minutes at room temperature to adjust the thickness of the photosensitive polyimide film 10 to the entire surface of the active matrix substrate. To be uniform. Then, the glass substrate 100 having the photosensitive polyimide film 10 formed on the upper surface is pre-baked at 120 ° C. for 3 minutes (FIG. 2B).

Next, the upper surface of the photosensitive polyimide film 10 is flattened by a chemical mechanical polishing (CMP) process. In the present embodiment, a colloidal material in which silica (SiO ₂ ) fine powder is dispersed in an acidic solution in a CMP slurry is used. C
The conditions for the MP treatment were as follows: the substrate was 50 rpm, and the polishing cloth was 50
The rotation is performed at rpm, and the polishing time is 3 minutes. This CM
In the P treatment step, the upper layer of the photosensitive polyimide film 10 was polished by 1 μm so that the polished photosensitive polyimide film 20 had a thickness of 2.6 μm from the surface of the reflective electrode 110.

In this embodiment, a slurry in which silica fine powder is dispersed in an acidic solution is used as a slurry for the CMP treatment. However, aluminum oxide (Al ₂ O ₃ ), cerium oxide (CeO ₂ ), or the like is used. A material dispersed in an acidic solution may be used. It is desirable to change the slurry depending on the material to be subjected to the CMP treatment. Further, the optimum substrate rotation speed, polishing cloth rotation speed and time may be determined according to the material to be subjected to the CMP treatment and the polishing amount.

Photosensitive polyimide film 20 after CMP treatment
Determines the cell gap (substrate spacing). Therefore, the thickness of the photosensitive polyimide film 10 before the CMP treatment may be appropriately set based on the size of the cell gap and the polishing amount in the CMP treatment.

Further, even if the thickness of the photosensitive polyimide film 10 before the CMP process varies for each substrate, the polishing amount of the CMP process is adjusted to adjust the photosensitive polyimide film 20 for each substrate.
Can be made uniform in film thickness.

Next, as shown in FIG. 2D, the photosensitive polyimide film 20 is covered with a photomask 30 in order to pattern the CMP-processed photosensitive polyimide film 20. Although the photomask 30 is illustrated as being divided in FIG. 2D, it is actually integral and has a configuration in which a plurality of circular openings are provided.

In the state shown in FIG. 2D, ultraviolet light is irradiated. Thereafter, development processing is performed, and post-baking is performed at 280 ° C. for 1 hour. Thus, as shown in FIG. 2E, the portion of the photosensitive polyimide film 20 irradiated with the ultraviolet rays remains, and the columnar cell gap holding material 300 is formed.

Next, an alignment film 120 is formed. As the alignment film material, a polyimide vertical alignment film is used. This polyimide vertical alignment film is formed on the substrate 100 by spin coating, flexographic printing, or screen printing. In this embodiment, the alignment film 300 is formed by spin coating in order to reduce physical impact on the gap holding member 300. Thereafter, heating (baking) is performed by sending hot air of 180 ° C. to cure the polyimide. The thickness of the alignment film 120 after curing was set to 100 nm. (FIG. 2 (F)).

FIG. 5 is a top view of the substrate 100 in the state of FIG. In the present embodiment, the shape of the gap holding member 300 is a cylindrical shape whose bottom surface is a perfect circle having a diameter of 3 μm. Also,
The height is about 2.5 μm from the surface of the alignment film 120.
The gap holding members 300 are arranged regularly, and the arrangement density is set to 50 pieces / mm ² . Gap holding member 30
The arrangement density of 0 may be, for example, about 40 to 160 pieces / mm ^2, which is about the same as the dispersion density of the conventional spacer.
What is necessary is just to set according to the intensity | strength of the gap holding member 300.

Further, in this embodiment, the upper surface 300a of the cell gap holding member 300 is in contact with the transparent electrode 210 with all the cell gap holding members 300 on the reflective electrode 110 and the glass substrates 100 and 200 facing each other. It is formed at a position facing the same.

The surfaces of the glass substrates 100 and 200 (the surfaces in contact with the liquid crystal material) are periodically uneven due to the multilayer structure of the striped electrodes 110 and 210 and the like. When the glass substrates 100 and 200 face each other, the cell gap periodically changes due to the unevenness. Therefore, in the present embodiment, in response to the periodic change of the cell gap, as described above, all the cell gap holding members 300 are provided at positions where the cell gaps are substantially the same, and the height of the cell gap holding member 300 is raised. The cell gaps were made substantially the same by the CMP process so that the cell gap was maintained uniform over the entire substrate.

In FIG. 2F, the orientation film 120 causes
The illustration is made such that the side surface and the upper surface 300a of the gap holding member 300 are not covered. This is because, in the present embodiment, the photosensitive polyimide film 10 is formed by a spin coating method, and the thickness of the gap holding member 300 is several μm, the gap holding member 30 erected as shown in FIG.
This is because the alignment film 120 may not form a complete film on the 0 side surface or the upper surface 300a. Therefore, FIG.
(F) shows only the alignment film 120 which is formed on the horizontal surface of the glass substrate 100 and completely forms a film.

Next, processing for the glass substrate 200 will be described with reference to FIG. A color filter 230 is formed on the glass substrate 200, and then a protective film 240 made of an acrylic resin or an epoxy resin is formed on the color filter 230. In this embodiment, the protective film 240 is formed of an acrylic resin having a thickness of 1 μm. Note that, in FIG.
0 and the protective film 240 are omitted (FIG.
(A)).

Next, a transparent electrode 2 made of a transparent conductive film such as ITO (indium tin oxide) or SnO ₂ (tin oxide) is used.
Form 10. In this embodiment, an ITO film is formed by sputtering and patterned to form a striped transparent electrode 210. Then, an alignment film 220 made of a polyimide-based vertical alignment film is formed by the same process as the alignment film 120 (FIG. 3B).

Next, a rubbing treatment is applied to each of the alignment films 120 and 220. In the present embodiment, the length of the hair foot is 2-3 m.
The alignment films 120 and 220 are rubbed with a roller around which a buff cloth (fiber such as rayon or nylon) is wound. The rubbing direction is one diagonal direction of the glass substrates 100 and 200, and the rubbing directions of the alignment films 120 and 220 are orthogonal to each other with the glass substrates 100 and 200 facing each other.

In the glass substrate 100, since the gap holding member 300 protrudes from the alignment film 120, the gap holding member 300 may be damaged or peeled off. By adjusting the conditions such as the number of rotations of the roller and the number of times of rubbing, such a problem can be avoided.

Next, one of the glass substrates 100 and 200 is coated with a sealing material for bonding the substrates. In this embodiment, a sealing material made of an ultraviolet curable resin is applied to the peripheral portion on the glass substrate 200 side, leaving a liquid crystal injection port. Then, the glass substrates 100 and 200 are opposed to each other, and pressed so that the cell gap becomes the height of the gap holding member 300. In this state, ultraviolet rays are irradiated to cure the sealing material.

Next, the liquid crystal 400 is injected from the liquid crystal injection port. Thereafter, a sealant is applied to the liquid crystal injection port, and the sealant is cured by irradiating ultraviolet rays to completely seal the liquid crystal in the cell. Then, a retardation plate 510, a polarizer 520, and a forward scattering plate 530 were provided on the back surface of the glass substrate 200, respectively. Through the above steps, the full-color STN liquid crystal panel shown in FIG. 4 was completed.

FIG. 4 is a sectional view of the liquid crystal panel.
2, the stripe-shaped reflective electrode 110 extends in a direction horizontal to the plane of the paper, and the stripe-shaped transparent electrode 210 extends in a direction perpendicular to the plane of the paper.

In this embodiment, the gap holding member 30
0 is provided on the glass substrate 100 side because the glass substrate 20
This is because the color filter 230 is provided on the 0 side. The gap holding member 300 has been subjected to a chemical mechanical polishing process. Since the polishing process applies a physical force, the cell gap holding member 300 is provided on the side of the glass substrate 100 on which the color filter 230 is not provided in order to minimize the occurrence rate of defects.

In this embodiment, an example of a full-color panel is shown. However, since a color filter 230 is not required for a black-and-white display panel, a three-panel projection panel, or the like, in this case, either of the glass substrates 100, The cell gap holding member 300 may be provided at 200. That is, a substrate on which the cell gap holding member 300 is provided may be selected so that the incidence of defects in the manufacturing process is reduced.

In this embodiment, an example of a reflection type liquid crystal panel is shown. However, the cell gap holding member 300 of this embodiment can also be used for a transmission type panel.

In the present embodiment, the gap holding member 3
00 are arranged regularly, for example, as shown in FIG.
They may be arranged at random. Even in this case, since the position of the gap holding member 300 is determined by the photomask 30, it does not aggregate at one place unlike the conventional spacer.

In this embodiment, the bottom surface of the gap holding member 300 is a perfect circle. However, the bottom surface of the gap holding portion 300 may be elliptical, streamlined, or polygonal such as triangular or square. Any shape is allowed as long as the shape can control the gap and the strength can be obtained. Further, in the present embodiment, all the gap holding members 300 have the same shape, but the gap holding members 300 having a plurality of types of shapes may be formed on the same substrate. In this embodiment, since the shape of the bottom surface of the gap holding member 300 is determined by the photomask 30,
The shape of the bottom surface of the gap holding member 300 can be easily and accurately changed.

In this embodiment, the arrangement density of the plurality of cell gap holding members 300 is uniform, but the arrangement density of the gap holding members in a specific region may be increased for the purpose of, for example, increasing the strength. . In the present embodiment, since the arrangement density is determined by the photomask 30,
Changing the arrangement density of the gap holding members 300 can be easily and accurately performed.

[Second Embodiment] In the first embodiment, an example of an STN-liquid crystal panel has been described. However, the present invention can be applied to a liquid crystal panel using a ferroelectric liquid crystal. In this embodiment, in the reflective panel shown in FIGS.
It is formed in a cylindrical shape having a regular circular bottom having a diameter of 2 μm and a diameter of 2 μm. The manufacturing method, formation position, and arrangement density of the cell gap holding member 300 are the same as those in the first embodiment.

The size of the cell gap can be arbitrarily determined by the cell gap holding member 300, and the position of the cell gap can be controlled. Further, the surface facing the other substrate surface is flattened. Therefore, the cell gap holding member 300 can maintain a cell gap smaller than the helical pitch of the ferroelectric liquid crystal with high accuracy and uniformity over the entire substrate.

The ferroelectric liquid crystal has characteristics such as no crosstalk, a large viewing angle, and a high-speed switching characteristic that is three orders of magnitude faster than the STN liquid crystal, and realizes high definition and a large screen even with a simple matrix driving method. obtain. Therefore, by using the cell gap holding member 300 of the present embodiment, it is possible to provide a low-cost, high-definition, large-screen ferroelectric liquid crystal panel.

Further, an antiferroelectric liquid crystal can be used instead of the ferroelectric liquid crystal. Even when an antiferroelectric liquid crystal is used, the cell gap needs to be 2 μm or less so that the helical structure of the liquid crystal disappears. However, by using the cell gap member 300 of this embodiment, the cell gap is set to 1. It can be 5 μm or less.

[0051]

According to the electro-optical device of the present invention, a gap holding member fixed to at least one of the substrates is provided in place of the conventional spacer, so that the cell gap can be held with high accuracy and uniformity. .

That is, by chemically and mechanically polishing the surface of the insulating film constituting the gap holding member, the height of the gap holding member can be arbitrarily set, and the surface facing the other substrate is flattened. be able to. Further, since the gap holding member is manufactured by patterning the insulating film, the manufacturing position can be set arbitrarily. Because of these features, the gap holding member of the present invention
The cell gap can be accurately and uniformly maintained. Therefore, it is possible to provide a simple matrix driving type electro-optical device having good display characteristics.

Since the electro-optical device of the present invention has a simple matrix structure, the lower structure of the insulating film constituting the gap holding member is much simpler than the active matrix element substrate. Therefore, even when the surface of the insulating film is subjected to chemical mechanical polishing, the rate of occurrence of defects due to this polishing step is very small as compared with the active matrix element substrate. Therefore, it is possible to provide an electro-optical device of a simple matrix driving system at low cost, with good productivity, and with good display characteristics.

Further, since the electro-optical device of the present invention has a cell gap holding member, it is particularly necessary to maintain a cell gap of 3 μm or less, such as a reflection type liquid crystal panel or a projection liquid crystal panel, or a cell gap of 2 μm or less. It is suitable for an electro-optical device that maintains a fine cell gap, such as a ferroelectric liquid crystal panel or an antiferroelectric liquid crystal panel that requires maintenance.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a simple matrix type liquid crystal panel of the present embodiment.

FIG. 2 is a diagram showing a manufacturing process of a simple matrix type liquid crystal panel of the present embodiment.

FIG. 3 is a diagram showing a manufacturing process of the simple matrix type liquid crystal panel of the present embodiment.

FIG. 4 is a schematic sectional view of a simple matrix type liquid crystal panel of the present embodiment.

FIG. 5 is a top view showing the arrangement of the gap holding members of the present embodiment.

FIG. 6 is a top view showing another arrangement example of the gap holding member.

[Explanation of symbols]

 Reference Signs List 10 photosensitive polyimide film 20 photosensitive polyimide film planarized (CMP treatment) 30 photomask 100 glass substrate 110 reflective electrode 120 alignment film 200 glass substrate 210 transparent electrode 220 alignment film 230 color filter 240 protective film 300 gap holding member 400 Liquid crystal 510 Retardation plate 520 Polarizer 530 Forward scattering plate

Claims (8)

[Claims] 1. An electro-optical device of a simple matrix drive system having two opposing substrates, wherein at least one of the two substrates is provided with a gap holding member for maintaining a distance between the pair of substrates. An electro-optical device, wherein a surface of the gap holding member facing the other substrate is planarized by chemical mechanical polishing. 2. The electro-optical device according to claim 1, wherein the gap holding member is made of a resin material selected from the group consisting of polyimide, acrylic, polyamide, and polyimide amide. 3. The electro-optical device according to claim 1, wherein the gap holding member is made of an ultraviolet curable resin or a thermosetting resin material. 4. The electro-optical device according to claim 1, wherein the gap holding member has a columnar shape. 5. A method of manufacturing an electro-optical device of a simple matrix type driving method having two opposing substrates, comprising: forming an electrode on each of the two substrates; and forming at least one of the two substrates. A step of forming an insulating film on the electrode on the substrate; a step of chemically and mechanically polishing the surface of the insulating film; patterning the polished insulating film to form a gap between the pair of substrates; Forming a gap holding member for holding the electro-optical device. 6. The method according to claim 5, wherein the insulating film comprises:
A method for manufacturing an electro-optical device, comprising a resin material selected from polyimide, acrylic, polyamide and polyimide amide. 7. The insulating film according to claim 5, wherein
A method for manufacturing an electro-optical device, comprising a UV curable resin or a thermosetting resin material. 8. The method according to claim 5, wherein the gap holding member has a columnar shape.