JPH0667204A - Liquid crystal display device and its manufacture - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device having high display quality which eliminates characteristic variation of a TFT due to light irradiation and is excellent on the orientation of liquid crystal molecules at a display part, and its manufacturing method. CONSTITUTION:An active matrix type liquid crystal display device has a liquid crystal held between two substrates 15a and 15b, and the TFT 16 and a pixel electrode 9 are provided on the substrate 15a. A light shielding film 11 is formed except at the display part of the pixel electrode 9 on the substrate 15a. The light shielding film 11 in the upper part of the TFT 16 is made thick enough not to cause the TFT 16 to vary in characteristic owing to light and the film thickness of the light shielding film 11 at other parts is so set that the orientation of liquid crystal molecules at the display part excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device having a thin film transistor (TFT) array.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display element is a cathode ray tube (C
It is used in various fields because it has an advantage that the thickness (depth) can be remarkably reduced as compared with RT) and that power consumption during driving can be reduced.

In recent years, an active matrix type liquid crystal display device has been widely used which can display a high quality image in color even when the number of scanning lines is increased as in a television or a computer.

An active matrix type liquid crystal display device having a conventional TFT array is shown in FIGS. 3 and 4.

This liquid crystal display device has a gate electrode 31, a gate insulating film 32, an amorphous silicon semiconductor film 33, an n ⁺ amorphous silicon film 34, and a source electrode 3 on a substrate 45a.
5, 36, the source bus line 37, the drain electrode 38, the pixel electrode 39, the protective film 40, the light shielding film 41, and the alignment film 44 are laminated to form one cell substrate. The transparent electrode 42, the insulating film 43, and the alignment film 44 are laminated on the substrate 45b facing the cell substrate to form the other cell substrate. Liquid crystal is sealed between the cell substrates to form a liquid crystal cell. In FIG. 4, the shaded portion is the light shielding film 41.
Is a part where is formed.

In the liquid crystal display device as described above, TFTs 46 using amorphous silicon are provided in a matrix as switching elements for driving the picture elements.
Amorphous silicon has photosensitivity, and when it is irradiated with intense light, the characteristics as a semiconductor change and the leak current increases. In addition, light leakage may occur between the bus line and the pixel electrode. In order to prevent this, a light shielding film 41 is formed on one of the cell substrates 45a on which the TFT 46 is provided, and the TFT 46 and the bus line and the pixel electrode are not exposed to strong light. There is.

[0007]

In the liquid crystal display device as described above, the light shielding film 41 is formed with a uniform thickness on the portion of the substrate 15a other than the display portion of the picture element electrode 39. Therefore,
If the film thickness of the light shielding film 41 is increased to reduce the light transmittance in order to reduce the influence of light on the TFT 46, the film thickness of other portions also increases. This increases the step between the pixel electrode and the light-shielding film, disturbing the alignment of liquid crystal molecules in the display section,
The display image was adversely affected such as disclination. Conversely, if the film thickness is reduced so as not to adversely affect the alignment of liquid crystal molecules, the light transmittance increases,
There is a problem that the characteristics of the TFT 46 are changed because the TFT 46 cannot be shielded sufficiently.

The present invention has been made in order to solve the above-mentioned problems, and there is no change in the characteristics of the TFT due to light irradiation, and the alignment of the liquid crystal molecules in the display section is good, and a high display quality liquid crystal display is provided. An object of the present invention is to provide a device and a manufacturing method thereof.

[0009]

In a liquid crystal display device of the present invention, a liquid crystal is sandwiched between two substrates, and thin film transistors and pixel electrodes are provided in a matrix on one substrate. In the active matrix type liquid crystal display device in which a light-shielding film is formed to cover the one substrate portion other than the display portion, the light-shielding film makes the film thickness in the upper portion of the thin film transistor thicker than other portions. The above-mentioned object is achieved thereby.

The light-shielding film is made of polyimide, polyamide,
You may use what contains at least 1 sort (s) of polyamic acid, acryl, and those derivatives, and at least 1 sort (s) of carbon, a dye, and a pigment.

The liquid crystal display device manufacturing method of the present invention is an active matrix liquid crystal display device in which liquid crystal is sandwiched between two substrates and thin film transistors and pixel electrodes are provided in a matrix on one substrate. In the manufacturing method of, the step of forming a lower light-shielding film to cover the one substrate portion other than the display portion of the pixel electrode, and a portion on the lower light-shielding film and above the thin film transistor. And a step of forming an upper light-shielding film, whereby the above object is achieved.

According to the method of manufacturing a liquid crystal display device of the present invention, an active matrix type liquid crystal display device in which liquid crystal is sandwiched between two substrates and thin film transistors and pixel electrodes are provided in a matrix on one substrate. And a step of forming a first light-shielding film that covers the one substrate portion excluding the display portion of the thin film transistor and the pixel electrode, and a first light-shielding film that covers the upper portion of the thin film transistor. And a step of forming a second light-shielding film having a larger film thickness, thereby achieving the above object.

According to the method of manufacturing a liquid crystal display device of the present invention, an active matrix type liquid crystal display device in which liquid crystal is sandwiched between two substrates and thin film transistors and pixel electrodes are provided in a matrix on one substrate. In the manufacturing method of 1., a step of forming a light shielding film covering the one substrate portion other than the display portion of the pixel electrode, and a step of thinning the thickness of the light shielding film in a portion other than above the thin film transistor. Therefore, the above object is achieved.

[0014]

In the present invention, the light-shielding film formed to cover the TFT is formed thicker than other portions. Therefore, sufficient light shielding can be obtained for the TFT, and the alignment of the liquid crystal molecules in the display section can be maintained well.

[0015]

EXAMPLES The present invention will be described below based on examples.

(Embodiment 1) FIG. 1 is a vertical sectional view showing an embodiment of the liquid crystal display device of the present invention, and FIG. 2 is a plan view. In this liquid crystal display element, a light-shielding film 11 is provided so as to cover a portion of the substrate 15a other than the display portion of the pixel electrodes 9 arranged in a matrix (hatched portion in FIG. 2). The light-shielding film 11 is thicker in the upper portion of the TFT 16 (hatched portion in FIG. 2) provided in a matrix than in other portions.

A method of manufacturing this liquid crystal display device will be described with reference to FIGS.

First, as shown in FIG. 6A, glass,
A gate electrode 1 made of aluminum, tantalum, titanium, copper or the like is formed on a substrate 15a made of quartz or the like by sputtering. Next, as shown in FIG.
The gate insulating film 2 made of silicon nitride, silicon oxide or the like is formed by a plasma CVD method or the like. Subsequently, the amorphous silicon semiconductor film 3 and the n ⁺ -amorphous silicon semiconductor film 4 are formed by the plasma CVD method. After that, as shown in FIGS. 6C and 6D, the source bus line 7, the source electrodes 5 and 6 and the drain electrode 8 made of aluminum, tantalum, titanium, copper or the like are formed by sputtering or the like. As described above, the TFT 16 that switches the pixel electrode 9 is formed.

Next, as shown in FIG. 6D, a transparent conductive film (ITO) containing indium oxide as a main component is used,
The pixel electrode 9 is formed by sputtering or the like. If necessary, a protective film 10 made of silicon nitride, silicon oxide or the like is formed thereon by sputtering or the like. This protective film 10 has an effect of preventing the characteristic deterioration of the TFT 16 when the insulating property of the light shielding film 11 is not sufficiently high or when the light shielding film 11 contains ionic impurities.

Then, as shown in FIG. 6 (e), a light-shielding film is formed.
Forming 11.

As a material for forming the light shielding film 11,
Resin is used and the product is color mosaic CK200.
0 (trade name: manufactured by Fuji Hunt Electronics Technology Co., Ltd.), and polyimide, polyamide, polyamic acid, acryl or their derivatives colored with carbon, dye, pigment or the like can be used.

The light shielding film 11 can be formed by the following method.

First, the substrate 15a other than the display portion of the picture element electrode 9
A method of forming the light shielding film 11 including a step of forming a lower light shielding film so as to cover the portion and a step of forming an upper light shielding film on the lower light shielding film and above the TFT 16 will be described.

First, the substrate 15a other than the display portion of the picture element electrode 9
A resin is applied to the portion with a predetermined thickness. This is pre-baked, exposed and developed, and then main-baked. As described above, the lower light shielding film is formed. Further, resin is applied to the upper portion of the TFT 16 with a predetermined thickness. This is pre-baked, exposed and developed, and then main-baked. As described above, the upper light-shielding film is formed.

For example, when the color mosaic CK2000 is used, it is as follows.

First, the substrate 15a other than the display portion of the picture element electrode 9
3000r by spin coating the above resin on the part
Apply at pm for 20 seconds. This is pre-baked, exposed and developed, and then main-baked. Further, the above resin is applied to the upper portion of the TFT 16 by spin coating at 3000 rpm for 20 seconds. This is pre-baked, exposed and developed, and then main-baked. In this case, the film thickness of the light shielding film 11 above the TFT 16 is about 1 μm, and the visible light transmittance at 550 nm is about 0.25%. Further, the film thickness of the light-shielding film 11 other than on the TFT 16 is about 0.5 μm, and the visible light transmittance at 550 nm is about 5%.

Next, a step of forming a first light-shielding film by covering the portion of the substrate 15a excluding the display portion of the TFT 16 and the picture element electrode 9 and a step of covering the upper portion of the TFT 16 with the first light-shielding film. A method of forming the light shielding film 11 including a step of forming a second light shielding film having a large film thickness will be described.

First, the display portion of the pixel electrode 9 and the TFT 16
Resin is applied to a portion of the substrate 15a other than the above with a predetermined thickness.
This is pre-baked, exposed and developed, and then main-baked. As described above, the first light shielding film is formed. Next, a resin is applied to the upper portion of the TFT 16 with a predetermined thickness. This is calcined,
After exposure and development, main baking is performed. As described above, the second light shielding film is formed.

For example, the case of using the color mosaic CK2000 is as follows.

First, the display portion of the pixel electrode 9 and the TFT 16
The above resin is applied to the portion of the substrate 15a other than the above by spin coating at 3000 rpm for 20 seconds. This is pre-baked, exposed and developed, and then main-baked. As described above, the first light shielding film is formed. Next, the above resin is applied to the upper portion of the TFT 16 by spin coating the resin at 1000 rpm,
Apply in 20 seconds. This is pre-baked, exposed and developed,
The main firing is performed. As described above, the second light shielding film is formed. In this case, the film thickness of the light shielding film 11 above the TFT 16 is about 1 μm.
Therefore, the visible light transmittance at 550 nm is about 0.25.
%. Further, the film thickness of the light-shielding film 11 other than on the TFT 16 is about 0.5 μm, and the visible light transmittance at 550 nm is about 5%.

Next, the substrate 15a other than the display portion of the picture element electrode 9
A method of forming the light-shielding film 11 including a step of forming the light-shielding film covering the portion and a step of reducing the film thickness of the light-shielding film in the portion other than above the TFT 16 will be described.

First, the substrate 15a other than the display portion of the picture element electrode 9 is formed.
A resin is applied to the portion with a predetermined thickness. This is pre-baked, exposed and developed, and then main-baked. The light shielding film is formed by the above. After that, the light-shielding film other than above the TFT 16 is thinned. For example, a photoresist is applied to the surface of the light-shielding film and covered with a pattern mask. After that, by exposing and etching, the film thickness of the light shielding film 11 other than on the TFT 16 can be reduced.

For example, the case of using the color mosaic CK2000 is as follows.

First, the resin is spin-coated on a portion of the substrate 15a other than the display portion of the pixel electrode 9 to form 100
Apply at 0 rpm for 20 seconds. This is pre-baked, exposed and developed, and then main-baked. The light shielding film is formed by the above. Next, on the surface of the light shielding film, for example, OFPR-800
A photoresist such as (Tokyo Ohka Co., Ltd.) is applied and covered with a pattern mask. After that, expose it to P
Etching is performed with E-3 (manufactured by Tokyo Ohka Co., Ltd.) or the like to reduce the film thickness of the light-shielding film 11 other than on the TFT 16. In this case, the film thickness of the light shielding film 11 above the TFT 16 is about 1 μm, and the visible light transmittance at 550 nm is about 0.25%. Further, the film thickness of the light-shielding film 11 other than on the TFT 16 is about 0.5 μm, and the visible light transmittance at 550 nm is about 5%.

Even when the light shielding film 11 is formed by any of the above methods, the film thickness of the light shielding film 11 above the TFT 16 is formed to be thicker than the other film thicknesses.

Therefore, the film thickness 11 of the light-shielding film is sufficient to shield the TFT 16 in the upper part of the TFT 16 and does not affect the alignment of the liquid crystal molecules in the display part in the other parts. be able to.

After that, the alignment film 14 made of polyimide is
It is formed by a printing method or the like. As the alignment film, polyimide, polyamide or the like can be used. From the above,
One cell substrate of the active matrix type liquid crystal display device is prepared in which the light shielding film 11 having different film thickness is formed on the portion above the TFT 16 on the substrate 15a and the other portion.

Next, the transparent electrode 12 made of ITO or the like is formed on the substrate 15b by sputtering or the like. If necessary to prevent leakage, an insulating film 13 made of silicon nitride or the like may be further laminated. After that, the alignment film 14 is formed by a printing method or the like. As the alignment film, polyimide, polyamide or the like can be used as in the above. By the above, the other cell substrate is formed.

In that state, both cell substrates are subjected to orientation treatment,
After spraying the spacers, both substrates were bonded together, the periphery was sealed, liquid crystal was injected, and the injection port was sealed to obtain a liquid crystal cell. The liquid crystal used here is, for example, ZLI-
1552, ZLI-4217, ZLI-4353 and the like (manufactured by Merck Japan Co., Ltd.) can be used, and as the spacer, for example, SP-2045 (manufactured by Sekisui Fine Chemical Co., Ltd.) can be used.

The details of this embodiment are as follows. The light shielding film 11 was formed by the above three methods.

Insulating Substrates 15a and 15b: Glass Gate Electrode 1: Tantalum, Thickness 3000 Å Gate Insulation Film 2: Silicon Nitride, Thickness 3000 Å Semiconductor Film 3: Amorphous Silicon (a-Si), Thickness 300 Å Semiconductor Contact Film 4 : N ⁺ -amorphous silicon (n ⁺ -a-Si), thickness 450 angstrom source electrodes 5 and 6 and drain electrode 8: titanium, thickness 2,000 angstrom picture element electrode 9: ITO, thickness 1000 angstrom protective film 10: silicon oxide, Thickness 1000 Å Light-shielding film 11: Color mosaic CK2000, thickness 1 μm above TFT 16, thickness 0.5 μm except above TFT 16 Transparent electrode 12: ITO, thickness 1000 Å Insulation film 13: Silicon nitride, thickness 000 angstrom Alignment film 14: Polyimide, thickness 800 angstrom In this liquid crystal display device, the TFT 16 does not change its characteristics due to the influence of light even when the light shielding film 11 is formed by any method. The liquid crystal molecules were well aligned. Therefore, good display quality was obtained.

Example 2 A liquid crystal display device was produced in the same manner as in Example 1 except that the light-shielding film was made of polyamide containing pigment.

In this liquid crystal display device, the TFT 16 did not change its characteristics due to the influence of light, and the liquid crystal molecules in the display portion were well oriented. Therefore, good display quality was obtained.

In the above embodiment, polysilicon may be used as the material of the semiconductor film.

[0045]

According to the liquid crystal display device of the present invention, the characteristics of the TFT are not changed by light, and the liquid crystal molecules in the display section are well aligned. Therefore, a good display quality can be obtained for a direct-view display, a high-definition projector, and the like. Further, according to the method for manufacturing a liquid crystal display device of the present invention, the TFT
The light-shielding film in the upper portion and the light-shielding film in other portions can be formed with different thicknesses. Therefore, the film thickness of the light-shielding film above the TFT can be made sufficient for light-shielding the TFT, and the light-shielding film in the other part can not adversely affect the alignment of liquid crystal molecules in the display section.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a main part of an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a plan view showing a main part of an embodiment of the liquid crystal display device of the present invention.

FIG. 3 is a vertical cross-sectional view showing a main part of a conventional liquid crystal display device.

FIG. 4 is a plan view showing a main part of a conventional liquid crystal display device.

FIG. 5 is a process drawing showing a manufacturing process of a liquid crystal display device of the present invention.

FIG. 6 is a diagram showing a manufacturing process of the liquid crystal display device of the present invention.

[Explanation of symbols]

1 gate electrode 2 gate insulating film 3 amorphous silicon semiconductor film 4 n ⁺ -amorphous silicon film 5, 6 source electrode 8 drain electrode 9 pixel electrode 11 light-shielding film 12 transparent electrode 14 alignment film 15a, 15b substrate 16 TFT

Claims (5)

[Claims] 1. A liquid crystal is sandwiched between two substrates, thin film transistors and pixel electrodes are provided in a matrix on one substrate, and the one substrate portion other than the display portion of the pixel electrodes is covered. An active matrix liquid crystal display device having a light-shielding film formed therein, wherein the light-shielding film is formed such that the film thickness in the upper portion of the thin film transistor is thicker than the other portions. 2. A method for manufacturing an active matrix type liquid crystal display device in which a liquid crystal is sandwiched between two substrates, and thin film transistors and pixel electrodes are provided in a matrix on one substrate. A step of forming a lower light-shielding film covering the one substrate portion other than the display portion, and a step of forming an upper light-shielding film on a portion above the lower light-shielding film and above the thin film transistor. A method for manufacturing a liquid crystal display device, comprising: 3. A method of manufacturing an active matrix type liquid crystal display device, wherein liquid crystal is sandwiched between two substrates, and thin film transistors and pixel electrodes are provided in a matrix on one substrate. Excluding the display area of pixel electrodes,
Forming a first light-shielding film over the one substrate portion; forming a second light-shielding film over the thin film transistor and having a thickness larger than that of the first light-shielding film; A method for manufacturing a liquid crystal display device including the following. 4. A method for manufacturing an active matrix type liquid crystal display device, wherein liquid crystal is sandwiched between two substrates, and thin film transistors and pixel electrodes are provided in a matrix on one substrate. And a step of forming a light-shielding film to cover the one substrate portion other than the display portion, and a step of thinning the light-shielding film in a portion other than above the thin film transistor. 5. The light-shielding film contains at least one of polyimide, polyamide, polyamic acid, acrylic and derivatives thereof, and at least one of carbon, dye and pigment. Liquid crystal display device.