JPH0764110A - Active matrix substrate - Google Patents

Abstract

PURPOSE:To embody a reflection type liquid crystal display device which prevents reflection at parts exclusive of pixel electrodes without subjecting the device to intricate processes and has bright and high image quality by forming black insulating layers which do not allow the transmission of light on thin-film transistors(TFTs) and signal wirings. CONSTITUTION:The insulating layers 11 consisting of a black resin, etc., are formed on the TFTs and electrodes 8 for storage capacitances. Namely, the entire surface of the substrate 1 is uniformly coated the black resin which covers the TFTs, the electrodes 8 for storage capacitances and wirings for signals and permits photolithography. The black resin consits of the photosensitive resin incorporated the pigment, such as carbon black. The black resin is prebaked at 80 deg.C after the coating and is then formed with holes communicating with drain electrodes 7 by using an exposure device and is further post baked at 130 deg.C, by which the resin is stabilized. As a result, the source electrodes 6 and drain electrodes 7 existing in the lower part of the pixel electrodes 2 and the signal insulation connected thereto are shielded by the insulating layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix substrate, and more particularly to an active matrix substrate which can be preferably used in a reflection type liquid crystal display device or the like.

[0002]

2. Description of the Related Art A conventional active matrix substrate is shown in FIGS.
2 is a plan view of the pixel electrode portion of the active matrix substrate, and FIG. 3 is a sectional view taken along line XX in FIG. Two
Reference numeral 1 is a substrate made of glass or the like, on which a gate electrode 22 of a thin film transistor, an insulating film 23 to be a gate insulating film, an amorphous silicon layer 24, a source electrode 25, a drain electrode 26, and a protective film 27 are sequentially laminated. Was configured. A pixel electrode 28 made of a transparent conductive film or the like is connected to the drain electrode 26,
The storage capacitor electrode 2 is provided at the substantially central portion of the pixel electrode 28.
9 and the storage capacitor wiring 30 are formed. Note that FIG.
Inside, 31 is an image signal wiring, and 32 is a scanning signal wiring.

This active matrix substrate is used in a liquid crystal device of a transmissive display mode using a twisted nematic liquid crystal, and light is a thin film transistor portion including a gate electrode 22, a source electrode 25, a drain electrode 26 and the like, a storage capacitor electrode. 29, the image signal wiring 31, and the scanning signal wiring 32 are shielded from light, and there is a drawback that the effective efficiency of light is extremely low at an aperture ratio of about 40% as a display device.

Although a reflection type liquid crystal device in which a reflection plate (not shown) is arranged on the back surface side of such an active matrix substrate has been put into practical use, it has a small aperture ratio as described above and further has a polarizing plate (not shown). (Shown) is required, resulting in a significantly dark display screen.

In order to avoid such a problem, a phase transition type guest-host liquid crystal that does not require a polarizing plate has been proposed, and an active matrix substrate that reflects light at a pixel electrode has been proposed. This reflection type active matrix substrate is shown in FIG. In FIG. 4, reference numeral 41 denotes a substrate made of glass or the like, on which a gate electrode 42 of a thin film transistor, an insulating film 43 to be a gate insulating film, an amorphous silicon layer 44, a source electrode 49, a drain electrode 4 are formed.
6 are sequentially stacked to form a thin film transistor. An insulating layer 47 made of a translucent resin such as an acrylic resin is formed on the source electrode 45 and the drain electrode 46, and a pixel electrode 48 connected to the drain electrode 46 is formed on the insulating layer 47. Is. This pixel electrode 4
8 is formed of a metal thin film such as aluminum for reflecting incident light. In such a structure,
Since the pixel electrode 48 can be used as it is as a reflective electrode, a large aperture ratio can be obtained.

However, in the above method, when a voltage is applied to the pixel electrode 48 and the liquid crystal becomes in a transmissive state, the source electrode 45 adjacent to the pixel electrode 48 or an image formed continuously with the source electrode 45. Since light is also reflected by the signal wiring (not shown), there is a problem in that the outline of the pixel electrode 48 is visually unclear and the image quality is deteriorated. Although it is possible to form the black matrix 51 on the substrate 49 on which the counter electrode 50 is formed in order to prevent such image quality deterioration, the aperture ratio with a wide bending angle is greatly reduced.

[0007]

The active matrix substrate according to the present invention has been considered in view of the above problems, and is characterized in that a gate electrode connected to a scanning signal wiring is provided. A plurality of thin film transistors each having a source electrode and a drain electrode connected to the image signal wiring are provided over a substrate, an insulating layer is formed over the plurality of thin film transistors, and a pixel electrode connected to the drain electrode is formed over the insulating layer. In the active matrix substrate provided with, the insulating layer is formed of a black insulating layer that does not transmit light.

[0008]

With the above structure, the source electrode and the drain electrode located under the pixel electrode and the signal wiring connected to these are shielded by the insulating layer. Therefore, it is possible to prevent reflection from other than the pixel electrode without significantly sacrificing the aperture ratio and through a more complicated process than the conventional method, and it is possible to realize a bright and high-quality reflective liquid crystal display device. .

[0009]

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of an active matrix substrate according to the present invention, and 1 and 2 are substrates made of glass or the like.

A thin film transistor is formed by sequentially laminating a gate electrode 3 of a thin film transistor, an insulating film 4 serving as a gate insulating film, an amorphous silicon layer 5, a source electrode 6 and a drain electrode 7 on a substrate 1. The substrate 1 on which the thin film transistor is formed does not necessarily have to be translucent. Although not shown, image signal wirings formed continuously on the source electrode 6 and scanning signal wirings formed continuously on the gate electrode 2 are formed in a matrix. Further, the drain electrode 7 and the extended portion thereof do not need to be a transparent conductive film, and the shape thereof does not need to have the same width as a pixel electrode described later. Therefore, it is advantageous in manufacturing.

A storage capacitor electrode 8 and a storage capacitor wiring 9 are formed adjacent to the drain electrode 7. The gate electrode 3, the source electrode 6, the drain electrode 7, the storage capacitor electrode 8, and the storage capacitor wiring 9 are each formed of aluminum (Al), chromium (Cr), titanium (Ti), nickel (Ni), or the like. And is formed by a vacuum vapor deposition method, a sputtering method, or the like.

A counter electrode 10 made of a transparent conductive film or the like is formed on the substrate 2 arranged to face the substrate 1.

An insulating layer 11 made of black resin or the like is formed on the thin film transistor and the storage capacitor electrode 8. That is, the thin film transistor, the storage capacitor electrode 8,
A photolithographic black resin that covers the signal wiring (not shown) is uniformly coated on the entire surface of the substrate 1. This black resin is made of, for example, a photosensitive resin containing a pigment such as carbon black. Examples of the photosensitive resin include an acrylic resin in which ethylsolve acetate is contained in a solvent. For coating, a spin coat method or a roll coater method can be used. After coating with black resin and prebaking at 80 ℃,
A hole communicating with the drain electrode 7 is formed using an exposure device, and post-baked at 130 ° C. to stabilize the resin.

Next, aluminum or the like is deposited to a thickness of 1 μm,
By patterning with photolithography, the pixel electrode 1
Form 2. When depositing a metal thin film of aluminum or the like, if the substrate temperature is set low, for example, 100 ° C. or lower, the surface of the metal thin film becomes pear-shaped irregularities, which is suitable as an electrode having scattering characteristics. In addition, the pixel electrode 12
Is preferably patterned so as not to largely overlap the wiring portion other than the drain electrode 7 and the storage capacitor electrode 8. That is, when the pixel electrode 12 is formed on a wiring other than the drain electrode 7 and the storage capacitance electrode 8, a capacitance is formed between the pixel electrode 12 and the other wiring, which increases the load during driving.

The pixel electrode 12 having the above structure
Forming with a μm pitch makes it possible to obtain an aperture ratio of 80% or more.

[0016]

As described above, according to the active matrix substrate of the present invention, a black insulating layer that does not transmit light is formed on the thin film transistor and the signal wiring, and the pixel electrode is formed on the black insulating layer. Since the light emitting element is formed, light is not reflected by the signal wiring and the like, so that blackening can be maintained and the contrast can be kept high, and good image quality can be obtained.
In addition, since the thin film transistor is also covered with the black resin, it is possible to prevent the deterioration of the image quality caused by the stray light or the like entering the thin film transistor. Furthermore, in the case of transparent resin, if the design is made at the very end of the wiring, the gap between the pixel wirings will be exposed due to the process capability during manufacturing, and the lower part of the substrate will be visible. In the case of the invention, that too can be avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an active matrix substrate according to the present invention.

FIG. 2 is a diagram showing a conventional active matrix substrate.

3 is a cross-sectional view taken along line XX of FIG.

FIG. 4 is a diagram showing another conventional active matrix substrate.

[Explanation of symbols]

1, 2 ... Substrate, 3 ... Gate electrode, 6 ... Source electrode, 7 ... Drain electrode, 11 ... Insulating layer, 1
2 ... Pixel electrode

Claims (1)

[Claims] 1. A gate electrode connected to a scanning signal line,
A plurality of thin film transistors each having a source electrode and a drain electrode connected to an image signal wiring are provided over a substrate, an insulating layer is formed over the plurality of thin film transistors, and a pixel electrode connected to the drain electrode is formed over the insulating layer. In the provided active matrix substrate, the insulating layer is formed of a black insulating layer that does not transmit light.