JPH10333132A - Substrate flatening method, liquid crystal display panel and liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance productivity and to make a device flat by easily eliminating unevenness by applying a flatening substance on the entire surface of a substrate surface. SOLUTION: The flatening substance is applied on the entire surface of the substrate surface. In the case that the unevenness 15 of scratches is caused by a jig for instance on the glass substrate 12 of a completed liquid crystal display panel, the flatening substance is applied on the surface of the glass substrate 12 having the unevenness 15. As the flatening substance, for instance SOG(Spin On Glass) film 34 is used. Organic SOG film is used as the SOG film 34, and is applied on the substrate surface having the unevenness 15 by a spinner. Then, a hot plate is prebaked, so that flatened film is formed. Also, a process is repeated until the desired thickness of the flatened film is obtained. The flatened film is formed by baking by a baking furnace after a thickness reaches a desired film thickness, so that the unevenness 15 of the substrate surface is eliminated and the substrate surface is made flat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for flattening a substrate by using a flattening material to make unevenness on the surface of the substrate, a liquid crystal display panel and a liquid crystal projector produced by using the flattening method.

[0002]

2. Description of the Related Art In recent years, a liquid crystal projector for enlarging and projecting a display of a liquid crystal display panel having a size of several inches on a screen has been developed. FIG. 10 is a schematic sectional view of a liquid crystal projector using a general liquid crystal display panel.

As shown in FIG. 1, light from a light source 16 is U
The blue light B transmitted through the V cut filter 17 and reflected by the dichroic mirror 18 is separated into the transmitted green light G and red light R. One reflected blue light B
Is reflected by the total reflection mirror 19, passes through the condenser lens 20, enters the liquid crystal display panel 21, then passes through the dichroic mirror 22, and further passes through the dichroic mirror 2.
3 and converge on the projection lens 24.

The other transmitted green light G and red light R are
The green light G is reflected by the next dichroic mirror 25, and the red light R is transmitted. The reflected green light G passes through the condenser lens 26 and enters the green liquid crystal display panel 27, is reflected by the dichroic mirror 22, further passes through the dichroic mirror 23, and passes through the projection lens 24.
The other transmitted red light R is transmitted through the condenser lens 28 and transmitted through the liquid crystal display panel 29 for green, and then reflected by the total reflection mirror 30 to be reflected by the dichroic mirror 23.
And is condensed on the projection lens 24.

Thus, each of the liquid crystal display panels 21,
The images 27 and 29 are synthesized on the screen 31 and are enlarged and projected. At this time, in the liquid crystal display panel used in the above-described liquid crystal projector, in a process until the liquid crystal display panel is completed, a point-like or linear scratch, that is, unevenness occurs on the substrate due to contact with a jig or the like.

Here, a description will be given of a flaw generated on a glass substrate used for a liquid crystal display panel and a conventional method for flattening the flaw. FIG. 11 is a plan view of a liquid crystal display panel having a scratched glass substrate, and FIG.
11 shows a cross-sectional view of the liquid crystal display panel along the line AA in FIG. As shown in FIGS. 11 and 12, a sealing material 14, which is an adhesive material having adhesive properties, is provided between a pair of glass substrates 1, 12 provided with electrodes 7, 13 around the glass substrates 1, 12. The two substrates 1 and 12 are adhered to each other with a material 14. These two glass substrates 1, 1
The liquid crystal 11 is filled in a gap formed by the
Is filled to form a liquid crystal display panel.

As shown in FIG. 11, a thin film transistor (hereinafter, referred to as "TFT") for driving liquid crystal is provided on a glass substrate 12 at the outermost side of the liquid crystal display panel.
Called. ), And contact with the jig during the process of bonding both substrates with the jig
In some cases, the glass is shaved to cause dot-like or linear scratches 15.

However, when the flaws are focused on the optical system of the liquid crystal projector, they are magnified and projected at the time of projecting the projector. Therefore, point-like or linear flaws are magnified and projected on the screen to significantly degrade the display quality. Become. Here, a case where a glass substrate of a liquid crystal display panel used for a liquid crystal projector is damaged will be described.

FIG. 13 is a partial schematic view of a liquid crystal projector when a glass substrate of a liquid crystal display panel is damaged.
As shown in FIG. 13, the light traveling from the light source direction passes through the condenser lens 20, passes through the liquid crystal display panel 21, is further focused on the projection lens 24, and is enlarged and projected on the screen 31. At this time, when the flaw 15 on the glass substrate 12 of the liquid crystal display panel 21 is focused (dotted line a in the figure)
In this case, the scratch 15 is magnified and projected together with the actual display 33 and is projected 15a on the screen 31, which has a very bad influence on the display.

Therefore, conventionally, as shown in FIG. 14, in order to eliminate the scratches generated on the glass substrate 12, that is, the irregularities 15,
A method has been employed in which the surface of the glass substrate 12 is polished to a depth equal to or greater than the depth of the scratch using a CMP (Chemical Mechanical Polishing) apparatus or the like (indicated by a dotted line in the figure).
However, in this conventional method, it takes a very long time for each substrate to polish and flatten the unevenness of the glass substrate 12 (for example, about one hour on average), so that there is a problem that the productivity is very low. Was. In addition, this conventional method has a problem that the glass substrate is easily damaged.

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned conventional drawbacks, and it is intended to eliminate the scratches, i.e., irregularities generated on the surface of a substrate easily and with good productivity and to make the surface flat. It is an object of the present invention to provide a method for flattening a substrate, and a liquid crystal display panel and a liquid crystal projector produced by the flattening method.

[0012]

According to the first aspect of the present invention, a flattening material is applied to the entire surface of the substrate. According to a second aspect of the present invention, in the substrate flattening method according to the first aspect, the flattening material is a material in which the refractive index of the flattening material is substantially equal to the refractive index of the substrate to be coated. .

According to a third aspect of the present invention, in the substrate flattening method according to the first or second aspect, the substrate is made of glass or acrylic resin. According to a fourth aspect of the present invention, in the substrate flattening method according to any one of the first to third aspects, the flattening material is an SOG film or an acrylic resin. According to a fifth aspect of the present invention, a liquid crystal material is filled in a gap formed by a pair of substrates which are opposed to each other and have unevenness on one of the substrates, and an adhesive material provided on a peripheral portion of the pair of substrates. In this liquid crystal display panel, a surface flattening substance is applied to the entire surface of a substrate having irregularities among the pair of substrates.

According to a sixth aspect of the present invention, a liquid crystal material is filled in a gap formed by a pair of substrates facing each other and having unevenness on one of the substrates, and an adhesive material provided on the periphery of the pair of substrates. In the filled liquid crystal display panel,
The entire surface of the substrate having the unevenness of the pair of substrates is coated with a surface flattening substance having substantially the same refractive index as the substrate.

According to a seventh aspect of the present invention, there is provided a liquid crystal projector using the liquid crystal display panel according to the fifth or sixth aspect. That is, since the invention according to claim 1 is characterized in that a flattening substance is applied to the entire surface of the substrate, scratches generated on the substrate surface can be chemically and mechanically applied to the conventional substrate surface. Compared to the polishing method, it can be eliminated very easily, the process can be simplified, and the productivity is very good. Further, there is very little risk of damaging the substrate as compared with chemical mechanical polishing.

According to a second aspect of the present invention, in the method of flattening a substrate according to the first aspect, the flattening material is a material having a refractive index of the flattening material substantially equal to a refractive index of the substrate to be coated. So, in the part of the scratch that occurred on the substrate surface,
Light incident on the substrate is not reflected or diffused, and does not adversely affect display. According to a third aspect of the present invention, in the method for flattening a substrate according to the first or second aspect, since the substrate is made of glass or acrylic resin, a high light transmittance can be obtained. , A bright display can be obtained. Further, since the substrate is made of glass or acrylic resin, an applicable flattening substance can be easily selected.

The invention described in claim 4 is the first to third aspects of the present invention.
In the substrate flattening method according to the above, the flattening material,
Since it is an SOG film or an acrylic resin, any film can be easily applied by a spinner, and by adjusting the rotation speed of the spinner, the viscosity of the flattening material, the number of times the flattening material is applied, and the like. A desired film thickness can be easily obtained. In the case of acrylic resin, it can be easily cured by ultraviolet irradiation.

According to a fifth aspect of the present invention, a liquid crystal material is filled in a gap formed by a pair of substrates facing each other and having unevenness on one of the substrates, and an adhesive material provided on the periphery of the pair of substrates. In the filled liquid crystal display panel,
Since a surface flattening substance is applied to the entire surface of the substrate having irregularities of the pair of substrates, air bubbles enter when the polarizing plate is attached to the substrate surface because the substrate surface can be flattened. It does not lose the polarization function.

According to a sixth aspect of the present invention, a liquid crystal material is filled in a gap formed by a pair of substrates facing each other and having irregularities on one of the substrates, and an adhesive material provided on the periphery of the pair of substrates. In the filled liquid crystal display panel,
Since the entire surface of the substrate having the unevenness of the pair of substrates is coated with a surface flattening substance having substantially the same refractive index as the substrate, light incident on the panel may diffuse or reflect on the uneven portion. Since it can be prevented, the transmitted light can be made uniform over the entire surface of the substrate.

The invention according to claim 7 is a liquid crystal projector using a liquid crystal display panel in which a surface flattening substance is applied to the entire surface of at least one of the pair of substrates. Even if point-like or linear scratches occur on the substrate during the manufacturing process of the substrate on which the TFT is provided, and the scratches are enlarged and projected in a state where the optical system of the projector is in focus, a point-like or linear scratch on the screen There is no significant reduction in display quality due to the enlarged projection of the scratches. Further, since the liquid crystal projector uses a liquid crystal display panel in which a surface flattening substance having a refractive index substantially equal to that of the substrate is applied to the entire surface of at least one of the pair of substrates, light incident on the panel is uneven. Since diffusion and reflection at the portion can be prevented, transmitted light can be made uniform over the entire surface of the substrate, so that point-like or linear flaws are magnified and projected on the screen, and the display quality does not significantly deteriorate.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of a liquid crystal display panel when the substrate flattening method of the present invention is applied to a liquid crystal display panel, and FIG. 2 is an exploded perspective view of the liquid crystal display panel. FIG. 3 is a cross-sectional view taken along the line AA in FIGS. As shown in FIG. 2, on one glass substrate 1,
A plurality of gate lines 3 partially provided with a gate electrode 2;
A plurality of drain lines 5 which are orthogonal to the respective gate lines 3 and partially include a drain electrode 4, and a TFT 6 is formed near an intersection of the respective lines 3 and 5,
The TFT 6 includes a part of the gate electrode 2 of the gate line 3, a part of the drain electrode 4 of the drain line 5, and a source electrode 8 connected to the display electrode 7. A polarizing plate 16 is provided on a surface of one of the glass substrates on which the display electrode is not formed. In the figure, for convenience,
Although three gate lines and five drain lines are used, actually, for example, 768 gate lines and 1024 drain lines are used.

As shown in FIG. 3, subsequently, on the TFT 6 and the display electrode 7, polyimide, SiO 2 for aligning the liquid crystal 11 on the surface in contact with the liquid crystal 11 via the insulating film 9.
An alignment film 10 made of, for example, is formed. Next, on the other glass substrate 12, a counter electrode 13 faces each display electrode 7 formed on the one glass substrate 1, and a region where the display electrode 7 on the one glass substrate 1 is formed. That is, the counter electrode 13 is formed on the entire surface corresponding to the display region.
An alignment film 10 made of an organic resin such as polyimide for orienting the liquid crystal 11 is formed on the surface of the substrate in contact with the liquid crystal 11 as in the case of one substrate.

The two substrates, one glass substrate 1 and the other glass substrate 12, are adhered by applying a sealing material 14 as an adhesive material having adhesive properties around the display area 32. Then, the liquid crystal 11 is filled in the gap formed by the substrates 1 and 12 and the sealing material 14 to complete the liquid crystal display panel. In the liquid crystal display panel completed in this way, the surface of the glass substrate is damaged by contact with a jig or the like in each step, for example, a step of forming a TFT which is a step before panel completion, or a step of bonding both substrates. It may adhere and cause irregularities on the surface of the glass substrate.

In the present embodiment, a case is shown in which irregularities 15 of scratches caused by a jig are generated on a glass substrate 12 of a completed liquid crystal display panel. Therefore, unevenness 1
A flattening substance is applied to the surface of the glass substrate 12 with 5. SOG (Spin On Glass) film 3 as a planarizing material
4 will be described.

The formation of the SOG film is as follows. S
As the OG film, an organic SOG film (for example, having a viscosity of 20 cp) is used, and the OG film is applied to the uneven substrate surface by a spinner. Thereafter, the film is pre-baked at 120 ° C. for 1 minute using a hot plate, so that 2000 to 3000 ° C.
Can be formed. These steps may be repeated until the desired flattening film thickness is reached. The thickness of the flattening film is not less than the depth of the unevenness, and may be any thickness that can be applied to the entire surface of the substrate and makes the surface flat. When the desired film thickness is reached, baking is performed in a baking furnace at 200 ° C. for 30 minutes to form a flattened film, and the substrate surface is flattened without unevenness.

Hereinafter, the application of the flattening substance in each manufacturing process of the liquid crystal display panel will be described. First, a case where a flattening material is applied after a step of forming a TFT which is a step before completion of a liquid crystal display panel will be described. FIG. 4 is a cross-sectional view in which a TFT of a liquid crystal front panel is formed on a substrate, and then an organic SOG film is formed on a surface where the TFT is not formed.

In the case of the irregularities 15 on the glass substrate 1 generated in the step of forming the TFT, the whole of the TFT 6 and the display electrode 7 is covered with a resist film 36 to protect it. And 15
After curing the resist film 36 at 0 ° C. for 30 minutes, the TFT 6
The SOG film 37 is formed as described above with the glass substrate 1 on which is formed as above. Then, the resist film 36 is removed, and baking is performed at 300 ° C. for 30 minutes in a baking furnace.

Thus, an SOG film can be formed on the surface of the substrate, and the surface becomes flat. After forming the TFT, the TF
After the polyimide for aligning the liquid crystal is formed on the substrate on which the T is formed, the baking in the baking furnace is preferably performed at 250 ° C. for 30 minutes in order to prevent the polyimide from being deteriorated by heat. Here, “after the TFT is formed” includes the case where the TFT and each line are formed and an insulating film is formed thereon.

Next, a case where a flattening substance is applied after the step of bonding both substrates will be described. FIG. 5 is a cross-sectional view showing a case where a planarizing substance is applied after both substrates are bonded. As shown in FIG.
For example, a resist film 36 is formed on the surface of the substrate 1 in order to protect the substrate 1 in which the generation of the resist 1 has not occurred. After that, the SOG film 37 is formed as in the case after the step of forming the TFT. Then, after removing the protective resist film 36, S
The OG film 37 is cured. This is the state where the resist film 36 is removed in FIG. The curing temperature of the SOG film 37 is set to a temperature at which the liquid crystal does not deteriorate, for example, 200 ° C.

It is not always necessary to form a resist film or the like for protection, and it is also possible to form an SOG film with the scratched surface facing up. If both surfaces are scratched, an SOG film may be applied to both substrates in order without covering with a resist film. <Second Embodiment> A case in which an acrylic resin is applied instead of the above-described SOG film to a substrate having irregularities will be described below.

FIG. 6 is a sectional view showing a case where an acrylic resin is formed on a substrate having irregularities. As shown in the figure, an acrylic resin film 38 (TB3042
(ThreeBond Co., Ltd., viscosity 20 cp)). Thereafter, ultraviolet light (365 nm) is irradiated with 1500 mJ / cm 2 39 to form a flattening film of about 2000 to 3000 °.

These steps may be repeated until the desired flattening film thickness is reached. As in the first embodiment, the thickness of the flattening film is not less than the depth of the unevenness, and may be any thickness that can be applied to the entire surface of the substrate and makes the surface flat. In this manner, the surface of the substrate having unevenness due to the scratch can be made flat. Here, when an acrylic resin, which is an ultraviolet curable resin, is used as a flattening substance as in the present embodiment, there is a concern that the liquid crystal may be deteriorated by ultraviolet rays. The application of the oxide film is more preferably the SOG film used in the first embodiment.

The same effect can be obtained by changing the viscosity of the flattening substance, the number of times of application, and the like for obtaining a desired film thickness in each of the above-described embodiments. Further, in the above embodiment, the resist film 36 is formed on the substrate having no unevenness. However, a film or the like which can protect the substrate surface and can be easily peeled off after the formation of the flattening film may be attached.

Further, in this embodiment, the case where the flattening film is formed on the substrate on which the TFT is formed has been described. However, as shown in FIG. Can be applied in the same manner, and the same effect can be obtained. Furthermore, the so-called active matrix liquid crystal display device having a TFT has been described. However, the present invention can be similarly applied to a simple matrix liquid crystal display device, and the same effects can be obtained.

FIG. 8 is a cross-sectional view when applied to a simple matrix type liquid crystal display device. First, one glass substrate will be described. On one glass substrate 1, ITO
A transparent electrode 40 made of (Indium Tin Oxide) or the like is formed by being patterned in a stripe shape. An alignment film 10 made of an organic resin such as polyimide for aligning the liquid crystal 11 is formed on a surface in contact with the liquid crystal 11 thereon.
The direction of the stripe of the transparent electrode 40 is arranged at right angles to the direction of the stripe of the color filter 41 described later.

Then, outside the one glass substrate 1,
That is, the polarizing plate 16 is disposed on the side not in contact with the liquid crystal 11 so as to be in a crossed Nicol position with the polarizing plate 16 provided on the other glass substrate 12. Next, the other glass substrate 12 will be described. On the other glass substrate 12, red,
A color filter 41 having green, blue, and black colors, a transparent insulating film 42, a transparent electrode 43, and an alignment film 10 are sequentially formed.

When irregularities are formed on the other glass substrate 12, a flattening film (SOG film or acrylic resin film) is applied on the other glass substrate 12 in the same manner as in the case of the active matrix type liquid crystal display device described above. I do. Then, the unevenness can be eliminated, and the polarizing plate 16 to be stuck on the substrate can be stuck uniformly without containing bubbles at the time of stuck.

Here, a case where the liquid crystal panel manufactured by the substrate flattening method of the present invention is used for a liquid crystal projector will be described. FIG. 9 is a partial schematic view of a liquid crystal projector when a glass substrate of a liquid crystal display panel is damaged. As shown in FIG. 9, the light traveling from the light source direction passes through the condenser lens 20, passes through the liquid crystal display panel 21, is further focused on the projection lens 24, and is enlarged and projected on the screen 31. At this time, even when the flaw 15 on the glass substrate 12 of the liquid crystal display panel 21 is focused (dotted line b in the drawing), the flaw 15 is enlarged and projected together with the actual display 33 and projected on the screen 31. There is no adverse effect on the display, and a high-quality display can be obtained.

[0039]

As described above, according to the present invention, when a scratch is generated on the substrate surface during the manufacturing process, the unevenness of the scratch can be eliminated by applying a flattening substance to the entire surface of the substrate. Since the substrate surface can be flattened, the productivity is higher and the unevenness can be easily eliminated as compared with the conventional substrate polishing.

According to the present invention, when used in a liquid crystal display panel or a liquid crystal projector, a high quality display can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a liquid crystal display panel.

FIG. 2 is a schematic perspective view showing an embodiment of the present invention.

FIG. 3 is a sectional view showing an embodiment of the present invention.

FIG. 4 is a sectional view showing an embodiment of the present invention.

FIG. 5 is a sectional view showing an embodiment of the present invention.

FIG. 6 is a sectional view showing an embodiment of the present invention.

FIG. 7 is a sectional view showing an embodiment of the present invention.

FIG. 8 is a sectional view showing an embodiment of the present invention.

FIG. 9 is a schematic partial sectional view showing an embodiment of the present invention.

FIG. 10 is a schematic sectional view of a general liquid crystal projector.

FIG. 11 is a plan view of the liquid crystal display panel.

FIG. 12 is a sectional view of a liquid crystal display panel.

FIG. 13 is a schematic partial sectional view showing a conventional embodiment.

FIG. 14 is a cross-sectional view of a conventional liquid crystal display panel.

[Explanation of symbols]

 Reference Signs List 1 glass substrate 12 glass substrate 15 unevenness 16 polarizing plate 34 SOG film 38 acrylic resin film 39 ultraviolet irradiation

Claims (7)

[Claims] 1. A method for flattening a substrate, comprising applying a flattening substance to the entire surface of the substrate. 2. The method according to claim 1, wherein the planarizing material is a material having a refractive index of the planarizing material substantially equal to a refractive index of a substrate to be coated. 3. The method according to claim 1, wherein the substrate is made of glass or acrylic resin. 4. The method according to claim 1, wherein the planarizing material is an SOG film or an acrylic resin. 5. A liquid crystal display panel in which a liquid crystal material is filled in a gap between a pair of substrates facing each other and having unevenness on one of the substrates and an adhesive material provided on the periphery of the pair of substrates. 3. The liquid crystal display panel according to claim 1, wherein a surface flattening substance is applied to all surfaces of the substrate having irregularities among the pair of substrates. 6. A liquid crystal display panel in which a liquid crystal material is filled in a gap formed by a pair of substrates facing each other and having unevenness on one of the substrates and an adhesive material provided on the periphery of the pair of substrates. 3. The liquid crystal display panel according to claim 1, wherein a surface flattening substance having substantially the same refractive index as that of the substrate is applied to the entire surface of the substrate having irregularities among the pair of substrates. 7. A liquid crystal projector using the liquid crystal display panel according to claim 5 or 6.