JPH11337968A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device with a driver circuit in one body having a small size, a large aperture ratio and high reliability by forming signal lines and pixel electrodes as separated layers by using a polyimide as an interlayer insulating film. SOLUTION: A pixel driving transistor 209, pixel electrode 210, scanning lines included in a first wiring layer 211 with the pixel driving transistor 209 and a gate electrode of a driver circuit 203, and signal lines included in a second wiring layer 212 are formed in a display region 202. The first wiring layer 211 and the second wiring layer 212 are insulated from each other by a first interlayer insulating film 213, and the second wiring layer 212 and the pixel electrode 210 are insulated by a second interlayer insulating film 214. The second interlayer insulating film 214 is removed in the area on the driver circuit 203 and the area under the seal 206. Therefore, the aperture rate can be increased. Since a polyimide can be formed by a spin coating method, the surface of the element substrate can be formed flat, which prevents disturbance in the alignment of a liquid crystal. Thus, a display of high quality can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an active matrix type liquid crystal display device in which a driver circuit is integrally formed, in which display is performed using liquid crystal sealed between two substrates.

[0002]

2. Description of the Related Art An example of a conventional active matrix type liquid crystal display device with a built-in driver circuit (hereinafter simply referred to as a liquid crystal display device) will be described with reference to FIG. FIG. 1A is a schematic external view of a conventional liquid crystal display device, FIG. 1B is a longitudinal sectional view taken along line AA of FIG. 1A, and FIG.
It is a BB longitudinal sectional view of (a). A driver circuit 1 for a display area 102, scanning lines and signal lines is provided on an element substrate 101.
03 and 104, and external connection terminals 105 are formed, the opposing substrate 106 is bonded to the element substrate 101 with a seal 107, and a liquid crystal 108 is interposed between the element substrate 101 and the opposing substrate 106.
Is enclosed.

[0005] A common electrode 109 is provided on the counter substrate 106, and the common electrode 109 is connected to a common terminal 110 on the element substrate 101 by a conductive agent 111. Also,
A light-blocking layer 112 is provided on the counter substrate 106.
A pixel driving transistor 113 is provided in the display region 102 of the element substrate 101, and a pixel electrode 114 is connected to the pixel driving transistor 113. The first wiring layer 115 including the pixel driving transistor 113, the gate electrode of the driver circuit 103 (104), and the scanning line is separated from the second wiring layer 117 by an interlayer insulating film 116, and the second wiring layer 117 is provided at a necessary place. 117 is connected. Second wiring layer 1
Reference numeral 17 includes a signal line in the display area, and is provided in the same layer as the pixel electrode 114. The upper layer of the second wiring layer 117 is provided with a liquid crystal protective insulating film 118 in order to prevent the signal of the second wiring layer 117 from leaking directly to the liquid crystal. LCD protective insulation film 1
Reference numeral 18 is usually removed from the pixel electrode 114. An alignment film 119 is further provided on the element substrate 101 and the counter substrate 106.

In the liquid crystal display device shown in FIG. 1, the pixel electrode 114 and the signal line (second wiring layer 117) are in the same layer, and it is necessary to secure a certain gap to avoid a short circuit. Does not contribute to display. This hinders an increase in the aperture ratio and definition of the liquid crystal display device. In order to solve this problem, an interlayer insulating film is further provided on the signal line, and a pixel electrode is provided thereon to insulate the pixel electrode and the signal line, thereby reducing a distance between the pixel electrode and the signal line, or In some cases, a method such as overlapping pixel electrodes is used. As the interlayer insulating film on the signal line, an organic thin film such as SiO2 or polyimide is used. The interlayer insulating film on the signal line
The simplicity of the formation method, the small dielectric constant (to reduce the coupling capacitance between the signal line and the pixel electrode), the ease of thickening due to small stress (for the same reason as the dielectric constant),
Furthermore, since the flatness of the film surface is easily improved as compared with SiO2, it is advantageous to use polyimide from the viewpoint of good display quality.

[0005]

In the conventional liquid crystal display device as shown in FIG. 1, the driver itself is located outside the seal, so that the device itself becomes large. There has been a problem that the driver circuit is easily damaged during handling in the course of manufacturing and a failure is easily caused. In addition, since the driver circuit is outside the seal, there are many wires (signal lines and scanning lines) that cross the seal, and moisture penetrates into the liquid crystal through the interface between the driver circuit and the wire that connects to the display area and the seal. There was a problem of deterioration.

[0006]

According to the liquid crystal display device of the present invention, an element driving thin film transistor, a signal line and a scanning line formed on an element substrate are covered with an organic film, and a pixel electrode is provided on the organic film. The signal line and the pixel electrode are insulated, and the driver circuit is formed on the pixel electrode side from the seal that joins the element substrate and the counter substrate. The organic circuit is not provided on the driver circuit, and the opposing substrate faces the driver circuit. It is characterized in that there is no upper common electrode.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an active matrix type liquid crystal display device with a built-in driver circuit according to the present invention and a manufacturing process thereof will be described in detail based on embodiments.

FIG. 2 shows the structure of the liquid crystal display device of this embodiment. FIG. 2A is a plan view of the liquid crystal display device of the present embodiment, and FIGS. 2B and 2C respectively show A in FIG. 2A.
It is a longitudinal section in -A and BB. On a transparent element substrate 201, a display area 202, a driver circuit 203,
An external connection terminal 204, a common terminal 205, wiring for connecting these, and the like are formed. A seal 206 joins the element substrate 201 and the counter substrate 207, and a liquid crystal 208 is sealed between the two substrates. Driver circuit 20
3 is provided between the seal 206 and the display area 202.
By doing so, the driver circuit 203 is moved to the display area 202.
The size of the liquid crystal display device can be reduced as compared with the case where it is located further outside. The display area 202 includes a pixel driving transistor 209,
The first wiring layer 21 together with the pixel electrode 210, the pixel driving transistor 209, and the gate electrode of the driver circuit 203
1 and the signal lines included in the second wiring layer 212 are formed, and the first wiring layer 211 and the second wiring layer 2 are formed.
Reference numeral 12 denotes a first interlayer insulating film 213, and the second wiring layer 212 and the pixel electrode 210 are insulated by a second interlayer insulating film 214. The portion of the second interlayer insulating film 214 above the driver circuit 203 and below the seal 206 is removed. This is because the second interlayer insulating film 214 mainly made of polyimide causes permanent polarization due to the electric field of the wiring of the driver circuit 203 and disturbs the orientation of the liquid crystal over a large area in the long term. The purpose is to prevent the deterioration of the liquid crystal and to prevent moisture and impurities from entering the liquid crystal through the polyimide. On the element substrate 201, an alignment film 215 for further aligning the liquid crystal is formed. The common terminal 205 and the common electrode 216 on the counter substrate 207 are electrically connected by a conductive agent 217, and the potential of the common electrode 216 is controlled. On the counter substrate 207, in addition to the common electrode 216, an alignment film 215 and a light-shielding film 2 if necessary.
18 and a color filter are formed in advance. (The color filter is omitted in this embodiment.) The portion of the common electrode 216 on the counter substrate 207 that overlaps the seal 206 and the portion that faces the driver circuit 203 are removed. This prevents the wiring other than the common terminal 205 on the element substrate 201 and the common electrode 216 from being short-circuited due to dust or the like in the seal 206 or the driver circuit 203.

Next, a manufacturing process of the liquid crystal display device of the present embodiment will be described with reference to FIG. FIG. 3 is a view for explaining a manufacturing process in a longitudinal section of a portion corresponding to FIG. 2B illustrating the structure of the liquid crystal display device of the present embodiment.

First, a pixel driving transistor 302 and a driver circuit 303 are formed on an element substrate 301. Scan line and pixel drive transistor 302 and driver circuit 3
At this time, a first wiring layer 304 including a gate electrode 03, a first interlayer insulating film 305, and a second wiring layer 306 including a signal line are formed at this time (FIG. 3A). In this embodiment, the pixel transistor 302 and the driver circuit 303 are composed of polycrystalline silicon thin film transistors. Although polycrystalline silicon is used for the first wiring layer 304, metal silicide or metal may be used, and the first interlayer insulating film 305 is made of a silicon oxide film (SiO ₂ ) or a silicon nitride film (Si ₃ N ₄ ). ,
Or a multilayer film thereof. Normally, an aluminum (Al) alloy (including copper and silicon) is used for the second wiring layer 306.

Next, a second interlayer insulating film 307 is formed on the element substrate 301, and a pixel electrode 308 is formed thereon.
A second interlayer insulating film 307 for the pixel driving transistor 302
Connect through the contact hole opened in the above. Further, an alignment film 309 is formed (FIG. 3B). The process of FIG. 3B will be described in more detail. In the present embodiment, after the second interlayer insulating film 307 (here, polyimide) is formed by spin coating, the pixel electrode 308 and the pixel transistor 3 are formed.
02 is formed by photolithography, but the second wiring layer 306 is not exposed at this time. In other words, at this point, the second interlayer insulating film 307 is still over the driver circuit 303 and under the seal.
Remains. Next, a pixel electrode 308 is formed, and then a second portion of the portion below the driver circuit 303 and below the seal is formed.
The interlayer insulating film 307 is removed.

This is because when indium tin oxide (ITO) is used for the pixel electrode 308 and an aqua regia-based etchant (aqueous solution containing nitric acid and hydrochloric acid) is used for the etching,
This is because when the second wiring layer 306, that is, Al is exposed, Al is attacked by the etching agent of ITO. When the ITO (that is, the pixel electrode 308) is formed by etching in a plasma containing, for example, hydrogen or methane, the second wiring layer 306 is formed.
May be exposed, so that the second interlayer insulating film 3
The 07 molding step can be performed once. The second interlayer insulating film 307 is a polyimide thin film here, but other resin thin films can be used as long as they have relatively high heat resistance and are transparent. Further, the second interlayer insulating film 307 may be a multilayer film of polyimide and SiO ₂ or Si ₃ N ₄ . In this case, the polyimide must be removed from the second interlayer insulating film 307 on the driver circuit 303 and under the seal, and polyimide may be left or removed. The alignment film 309 is also a polyimide thin film, and is formed using a printing technique (flexographic printing or the like), and is formed only on a portion necessary for aligning the liquid crystal. The formation of the alignment film 309 may be performed by a spin coating method.

The element substrate 301 on which the alignment film 309 is formed is bonded to the counter substrate 311 by a seal 310, and the liquid crystal 312 is sealed (FIG. 3C). Further, an external circuit is connected to an external connection terminal to complete a liquid crystal display device.

[0014]

In the liquid crystal display device of the present invention, the aperture ratio can be increased by forming the signal line and the pixel electrode in separate layers using polyimide as an interlayer insulating film, and the polyimide is formed by a spin coating method. Since the surface of the element substrate is flat, there is no disturbance in the alignment of the liquid crystal, and a high-quality display can be obtained. Furthermore, since the driver circuit on the element substrate is closer to the display area than the seal, hundreds of signal lines and scanning lines extending from the driver circuit to the pixel area do not cross the seal, and the wiring that crosses the seal from the external connection terminal The power supply line, clock line, video signal line, etc. connected to the driver circuit can be reduced to at most several tens of lines, which is much lower than before, so that the amount of water entering from the wiring that crosses the seal and the seal interface can be significantly reduced, and the reliability is high. In addition, since the driver circuit is inside the seal, the device can be made smaller than when the driver circuit is outside the seal. In addition, in the handling after the element substrate and the opposing substrate are joined (for example, in a dicing process). There is no damage to the driver circuit.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a conventional active matrix type liquid crystal display device with a built-in driver circuit.

FIG. 2 is a structural diagram of an active matrix liquid crystal display device having a driver circuit according to the present invention.

FIG. 3 is a process chart illustrating a method for manufacturing an active matrix liquid crystal display device with a built-in driver circuit according to the present invention.

[Description of References] 101, 201, 301 ... Element substrates 102, 202 ... Display areas 103, 104, 203, 303 ... Driver circuits 105, 204 ... External connection terminals 106, 207, 311 ... Counter substrates 107, 206, 310 ... Seals 108, 208, 312 Liquid crystal 109, 216 Common electrode 110, 205 Common terminal 111, 217 Conductive agent 112, 218 Light-shielding layer 113, 209, 302 Pixel drive transistor 114, 210, 308 Pixel electrode 115 , 211, 304 ... first wiring layer 116 ... interlayer insulating film 117, 212, 306 ... second wiring layer 118 ... liquid crystal protective insulating film 119, 215, 309 ... alignment film 213, 305 ... first interlayer insulating film 214, 307... Second interlayer insulating film

Claims (2)

[Claims] 1. A pixel electrode arranged at least in a matrix, a pixel driving thin film transistor connected to each of said pixel electrodes, a set of signal wiring and a set of scanning wiring connected to said pixel driving thin film transistor, An element substrate having a driver circuit for driving signal lines and scanning lines, an opposing substrate having a common electrode, opposing the element substrate, and an active matrix comprising liquid crystal sealed between the element substrate and the opposing substrate In the liquid crystal display device, an organic film is provided on the pixel driving thin film transistor on the element substrate, on the signal wiring and on the scanning wiring, the pixel electrode is provided on the organic film, and the driver circuit is provided on the element substrate. And the opposing electrode are joined to the pixel electrode side with respect to the sealing portion for sealing the liquid crystal at the same time. The liquid crystal display device which is the road and the sealing portion and the organic film is not, the portion opposed to the driver circuit, characterized in that there is no said common electrode on the counter substrate. 2. The liquid crystal display device according to claim 1, wherein said organic film is a polyimide film.