JPH04104227A - liquid crystal display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix liquid crystal display device useful for use in flat panel televisions, flat display information terminals, and the like.

[Conventional technology]

The structure of a pixel portion of an active matrix substrate equipped with a storage capacitor element (also referred to as a storage capacitor element or an auxiliary capacitor element) in a conventional liquid III display device is described in, for example, Japanese Patent Laid-Open No. 1-255831. .

FIG. 2 shows an example of a pixel portion of an active matrix substrate with a valley volume kit of a conventional liquid crystal display device, and although the structure of the thin film transistor is different from that of the prior art, it is essentially the same as the prior art. .

In the conventional example shown in FIG. 2, the gate electrode/scanning l1A 602 of the thin film transistor with an inverted staggered structure is made of a metal film, and the - side electrode of the storage capacitor is made of a transparent conductive film 603. It is formed on a transparent insulating substrate (not shown in FIG. 2). On top of this, a SiNx film (not shown in FIG. 2) is formed which serves as a gate insulating film, a dielectric for storage capacitance elements, and an interlayer insulating film for two-layer wiring.

Furthermore, a thin film semiconductor layer 606, which is an active layer of a thin film transistor, and a transparent pixel electrode 607 are formed thereon. The transparent pixel electrode 607 also serves as the other electrode of the storage capacitor element. A source electrode 608 of the thin film transistor is electrically connected to a transparent pixel electrode 607, and a drain electrode 609 is connected to each other and also serves as a signal line.

From the perspective of display quality, normally white,
It is desirable to perform a transmissive liquid crystal display in mode. In this case, it is necessary to eliminate the leakage of light from the transparent region 610 other than the transparent pixel electrode 607 in the active matrix substrate of FIG. 2. For this purpose, in the prior art, a second
A light shielding layer 611 as shown by the hatched area in FIG. 3 is provided on a transparent insulating substrate using, for example, a Cr film.

In FIG. 3, a region 610 to be shielded from light on the first substrate is indicated by a two-dot chain line.

The alignment accuracy between the region 610 on the first substrate to be light-shielded and the light-shielding layer 611 on the second substrate is determined by the alignment accuracy when bonding the first substrate and the second substrate. is much lower than the alignment accuracy of photolithography, for example, about 5 μm. Further, since the light shielding layer 611 is provided on the second substrate, the thickness of the liquid crystal layer is, for example, 7 μm in order to ensure a wide viewing angle.
In this case, in order to block the incident light from an angle of 35 degrees,
It is necessary to provide the light-shielding layer 611 so as to overlap the region 610 to be light-shielded by 3 μm. Therefore, in FIG. 3, a large design margin of 8 μm in total is provided for the misalignment margin and for the overlap to block obliquely incident light.

Another example of the planar structure of the pixel portion of the active matrix substrate with storage capacitor of the conventional liquid crystal display device is shown in FIG.

The planar structure of the pixel section shown in FIG.
It is essentially the same as that shown in Japanese Patent No. 55831.

The conventional example shown in FIG. 4 differs from the conventional example shown in FIG. 2 only in that one electrode of the storage capacitor element is composed of a transparent conductive film 603 and a non-transparent metal film 604. Everything else is exactly the same. For the same reason as described for the conventional example shown in FIG. 2, the conventional example shown in FIG. 4 also uses a Cr film, for example, on the second transparent insulating substrate, and A light shielding layer 611 as shown in is provided. In FIG. 5, a region 610 on the first substrate that should be shielded from light is indicated by a two-dot chain line. The light shielding layer 611 in FIG. 5 is the same as the light shielding layer 611 in FIG.
Same as 1.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, no consideration was given to reducing the area occupied by the light shielding layer 611, and there was a problem that the aperture ratio was low. In particular, this problem becomes serious when the pixel pitch is reduced for high-definition display, that is, when the pixel area is reduced.

Of course, the aperture ratio can be increased by expanding the outer edge of the pixel electrode 607 outward in FIGS. 2 and 4. However, since the pixel electrode is usually at the same level in cross-sectional structure as either the signal line or the scanning line, the pixel electrode 6
When the outer edge of 07 was expanded outward, the gap between the pixel electrode and the signal line or between the pixel electrode and the scanning line became narrower, and there was a problem that the short-circuit failure rate due to foreign matter etc. increased. .

Specifically, in the case of the conventional examples shown in FIGS. 2 and 4, if the outer edge of the pixel electrode 607 facing the drain electrode/signal line 609 is expanded outward, the cross-sectional structure on the SiNx film is the same. Since the gap between the drain electrode/signal line 609 and the pixel electrode 607, which are located at the same level, becomes smaller, there is a problem in that the defect rate due to a short circuit between the two increases.

Further, the same problem occurs when the pixel electrode and the signal line are at the same level in terms of cross-sectional structure, and the pixel electrode and the scanning line are at the same level in terms of cross-sectional structure.

In other words, in this case, if the outer edge of the pixel electrode facing the scanning line is expanded outward, the gap between the scanning line and the pixel electrode becomes smaller, which increases the defective rate due to short circuits between the two. The object of the present invention is to provide a liquid crystal display device that has a high yield rate in the manufacturing process and has a high aperture ratio in the pixel portion, that is, a liquid crystal display device that has a low manufacturing cost and that has a high display quality. Our goal is to provide high quality liquid crystal display devices.

Note that in the above description, the expressions "same level" and "different levels" are used, but the level referred to here does not necessarily mean a height level.

For example, when two electrodes are both on one insulating film or both are under one insulating film, these two electrodes are said to be at the same level, and the two electrodes are said to be at the same level. When one electrode is present and another electrode is under the insulating film, the two electrodes are said to be at different levels.

[Means to solve the problem]

If the transparent pixel electrode also serves as one of the pair of electrodes constituting the storage capacitance element, and the other electrode of the pair of electrodes is at least partially translucent, the aperture ratio will be lower than in the case where it is not. It is obvious that this structure becomes high, so the present invention assumes this structure as well as the conventional examples shown in FIGS. 2 and 4.

Based on the above premise, in order to achieve the above object, in the present invention, of a pair of electrodes constituting a storage capacitance element, the electrode that is not a pixel electrode is separated from a light-transmitting conductive film and a non-light-transmitting film. a part of the non-transparent conductive film,
It extends along the outer edge of the pixel electrode and overlaps part or all of the outer edge in terms of planar structure.

[Effect]

Of the pair of electrodes that constitute the storage capacitance element, the electrode that is not the pixel electrode is composed of a light-transmitting conductive film and a non-light-transmitting conductive film, and a part of this non-light-transmitting conductive film is As for the structure, by overlapping the outer edge of the pixel electrode and extending along the outer edge, the light shielding layer can be provided in the region overlapping the outer edge of the pixel electrode on the first substrate.

When the drain electrode/signal line and the pixel electrode are at the same level in cross-sectional structure as in the conventional example shown in FIGS. 2 and 4, the light-shielding layer made of the non-light-transmitting conductive film is The pixel electrode is separated by an insulating layer, which is a dielectric for the capacitive element.
Therefore, since the drain electrode/signal line is separated from the insulating layer, the conductive light-shielding layer is placed so as to overlap the outer edge of the pixel electrode facing the drain electrode/signal line, without causing an increase in the short-circuit failure rate. The second substrate can be provided on the first substrate in such a manner as to extend outside the outer edge.

Therefore, it is possible to narrow the light-transmitting portion of the first substrate other than the transparent pixel electrode, that is, the area of the first substrate that is shielded from light by the light-shielding layer on the second substrate. That is, the area of the light shielding layer on the second substrate can be reduced.

The same can be said of the case where the pixel electrode and the drain electrode/signal line are at different levels in terms of cross-sectional structure, and the pixel electrode and the gate electrode/scanning line are at the same level in terms of cross-section. That is, without causing an increase in the short-circuit failure rate, the conductive light-shielding layer is formed such that the outer edge of one pixel electrode overlaps the outer edge facing the gate electrode/scanning line, and is spread outside the outer edge. It can be provided on one substrate. Therefore, also in this case, the light-transmitting portion other than the transparent pixel electrode on the first substrate, that is,
The area on the first substrate to be light-shielded by the light-shielding layer on the second substrate can be narrowed. That is, the area of the light shielding layer on the second substrate can be reduced.

The alignment accuracy between the conductive light-shielding layer on the first substrate and the pixel electrode is the alignment accuracy of photolithography for large substrates, that is, about 1 μm.

Therefore, a design overlap margin of 2 μm between the conductive light-shielding layer and the pixel electrode is sufficient, and as mentioned above,
This is sufficiently small compared to the design margin of 8 μm between the light-shielding layer on the second substrate and the region to be light-shielded on the first substrate, so providing the conductive light-shielding layer increases the aperture ratio. It is not a factor that reduces the

That is, providing the conductive light-shielding layer on the first substrate does not cause a reduction in the aperture ratio, and the area of the light-shielding layer on the second substrate can be reduced, so that the aperture ratio can be increased. I can do it. As mentioned above, this does not lead to an increase in the short-circuit failure rate.

Further, in the present invention, since the conductive light-shielding layer is a part of one of the pair of electrodes constituting the storage capacitor, the light-shielding layer is provided on the first substrate separately from the one-side electrode. The structure is simpler than in the case of the conventional method, and the area for forming the capacitive element is also used for shielding light, so the aperture ratio can be increased.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 6 below.

This will be explained with reference to FIG.

FIG. 1 shows a planar structure of a pixel portion of an active matrix substrate in a liquid crystal display device according to an embodiment of the present invention.

In this embodiment, the pixel pitch is the same as in the conventional example shown in FIGS. 2 and 4, and the thin film transistor, pixel electrode, signal line, and scanning line are formed with the same structure and dimensions, and the storage capacitor is A pair of 1s that make up an element! The structure of one of the poles is different. Figure 6 is A of Figure 1.
It is an A' sectional view.

On the first transparent insulating substrate 601, a gate electrode/scanning line 602. In addition, one electrode for the storage capacitor element consisting of an indium tin oxide (ITO) transparent conductive film 603 and a non-light-transmitting metal film 604 is first formed. In the embodiment shown in FIG. 1, after a transparent conductive film 603 is formed and processed, a gate electrode/scanning line 602 and a non-light-transmitting metal film 604 are simultaneously formed using, for example, a Cr film. However, the gate electrode/scanning line 602 and the non-transparent metal film 6
The transparent conductive film 603 may be formed after the formation of the transparent conductive film 603. In addition, if necessary, an electrode/scanning line 602 is provided to the gate 1.
It goes without saying that the metal film 604 and the metal film 604 may be made using different metal materials.

Next, on this, a SiNx film 605 is formed which serves as a gate insulating film, a dielectric for storage capacitance elements, and an interlayer insulating film for two-layer wiring. Furthermore, a semiconductor thin film 606 and a transparent pixel electrode 607, which are active layers of a thin film transistor, are formed on this.

This transparent pixel electrode 607 also serves as the other electrode constituting the storage capacitor element. Similarly to the conventional example shown in FIGS. 2 and 4, a source electrode 608 and a drain electrode/signal line 609 are formed. Thereon, as is well known, a protective film (not shown) and an alignment film (not shown) are formed to complete the active matrix substrate.

In FIG. 1, the area formed by the non-light-transmitting metal film 604 among the electrodes constituting the storage capacitor element is indicated by diagonal lines. In this embodiment, the non-transparent metal crotch 604 extends along the outer edge of the transparent pixel electrode 607 and overlaps with three sides facing the drain electrode/signal line 609 among the four sides of the outer edge of the rectangle. ing.

The metal film 604 and the drain electrode/signal line 609 are Si
Since they are at different levels across the Nx film 605, the metal film 604 can be connected to the pixel electrode 6 without increasing the short-circuit failure rate.
It was possible to extend it outward from the outer edge of 07, that is, to bring it closer to the drain electrode/signal L; A609. Therefore, as shown in FIG. 1, it is possible to make the transparent portion 610 other than 1tJfi in the transparent pixel' on the first substrate significantly smaller than in the conventional example shown in FIGS. 2 and 4. did it. That is, the light shielding layer on the second substrate is
As shown by the shaded area 611 in the figure, it is significantly smaller than the conventional example.

As described above, according to this embodiment, it is possible to easily obtain a liquid crystal display device with a high yield rate in the manufacturing process and a high aperture size in the pixel portion at a low cost.

However, in the above embodiment, the first of the three sides is
The two sides in the figure also face the gate electrode 602, and the metal film 604 is at the same level as the gate electrode 602, so there is a limit to expanding the metal film 604 from the upper side of the pixel electrode in the -L direction. However, even if this is taken into account, the above-mentioned effects of this embodiment are still significant.

FIGS. 8 to 8 show plan views of pixel portions of other five embodiments of the present invention.
It is shown in FIG. In these embodiments, the cross-sectional structure is exactly the same as in the embodiments described above. Further, the symbols shown in the figures are the same as those in the above-described embodiment. In these embodiments as well, as in the above-mentioned embodiments, the liquid crystal display device has a high yield rate in the manufacturing process and has a large aperture in the pixel portion.

That is, it was possible to realize a liquid crystal display device with low manufacturing cost and high display quality.

In addition to the above effects, in the embodiment shown in FIG.
Another effect was obtained at the same time: the resistance of the wiring connecting the storage capacitor elements (hereinafter referred to as storage capacitor wiring resistance) could be lowered. Further, in the embodiment shown in FIGS. 10 and 11, the gate electrode/scanning line 609 and the metal film 6
Another advantage is that the short-circuit failure rate between the second embodiment and the fourth embodiment can be lowered compared to the embodiment shown in FIG. Also, the 12th
In the illustrated embodiment, the storage capacitor elements are electrically connected by the ITO film 603, so after forming the electrodes 603 and 604 on one side of the storage capacitor element, heat treatment and plasma treatment steps are performed in oxygen. There is also the advantage that variations and fluctuations in storage capacitance wiring resistance can be reduced when

In the above embodiments, an example of a thin film transistor with an inverted staggered structure was shown as an active element constituting an active matrix, but the effects of the present invention do not depend on the type and structure of the active element; Similar effects were obtained using two-terminal elements such as coplanar thin film transistors and metal-insulator-metal (MIM) diodes.

Further, in the above embodiment, the transparent pixel electrode and the signal line are at the same level, but according to the present invention, the same effect can be obtained even when the transparent pixel electrode and the scanning line are at the same level. Obtained.

In addition, in the above embodiment, a non-light-transmitting metal film, such as a Cr film, was used as an example of the non-light-transmitting conductive film constituting a part of the electrode on one side of the storage capacitance element. If so, the same effect could be obtained by using any kind of conductive film, for example, another metal film, an impurity semiconductor film exhibiting metallic conduction, a metal silicide film, etc.

In addition, in Example 2, an indium tin oxide (ITO) transparent conductive film was used as a transparent conductive film constituting a part of the electrode on the C side of the storage capacitance element.
3 film, Sn○2 film doped with Fe or sb, Z n O film doped with AQ or Si, Cd2S n O,
A similar effect was obtained even when a transparent conductive film such as a (CTO) film, a CdIn, 04(CIO) film, or a thin light-transmitting metal film was used.

In addition, in the embodiment described in "-", a SiNx film was used as the dielectric for the capacitive element, but SjO film, SiOx film, AQ20. Similar effects were obtained using other insulating films such as a film, a Ta2O film, a TaOx film, and the like. This means that
The same applies to the gate 1 insulating film of the thin film transistor and the interlayer insulating film for the insulation film edge film layer wiring for the MIM diode.

Next, a method for driving the display device of the present invention will be explained.

FIG. 13 shows an example of the configuration of a liquid crystal display system according to the present invention. The system includes an information processing system 218 such as a workstation, personal computer, word processor, etc., and a display system 200. The display system 200 includes a liquid crystal display module 202. Light source 201. Light source adjustment circuit 2
03゜Image data generation circuit 204A and timing (control circuit 204 composed of number generation circuit 204B)
, LCD brightness, contrast adjustment circuit 216, storage capacitor drive voltage generation circuit 205. It is constituted by a common electrode drive voltage generation circuit 206.

The liquid crystal display module 202 includes a liquid crystal display device (
(hereinafter also referred to as liquid crystal panel) 217. It is composed of a signal circuit 207 that generates a signal voltage, and a scanning circuit 208 that generates a scanning voltage.

The liquid crystal panel 217 includes thin film transistors 211 . Storage capacity 212, LCD 2
14. Signal line 2 for driving the thin film transistor
10 and a scanning line 209.

The Vstg voltage generated by the storage capacitor drive voltage generation circuit 205 and the Vc generated by the common electrode voltage generation circuit 206.
The OW voltage is applied to the storage capacitor common line 215 and the common electrode terminal 213, respectively, but these may have the same voltage level and phase and are not particularly limited.

Further, the connection method between the storage capacitor 212 and the storage capacitor common line 215 may be the connection example shown in FIG. 14, and is not particularly limited. Furthermore, a signal line 210 and a signal circuit 20
7, the signal lines may be pulled out alternately in the vertical direction and each signal line is connected to the signal circuit 207A and the signal circuit 207B, as in the connection example shown in FIG. 15, and is not particularly limited. It's not something.

FIG. 16 shows one embodiment of the liquid crystal display module 202. The liquid crystal display module 202 includes a liquid crystal panel 217. Signal circuit boards 227-234. Scanning circuit boards 222-224. Common electrode voltage vcoIl extraction substrates 225, 226 . Common electrode voltage Vcow and storage capacitance voltage 'Jstg extraction substrates 235, 23
6. It is composed of a signal supply board 220. The liquid crystal panel 217 consists of a first substrate 217A on which thin film transistors and the like are formed, and a second substrate 217B on which a common electrode and the like are formed, and a liquid crystal material is sealed between the two substrates.

Image data signals, power supply voltage, etc. are supplied to the signal supply board 220 via a signal cable 221.

A common electrode voltage ■coI11 is applied to the common electrode terminal 238. Further, the storage capacitor voltage Vstg is applied to the storage capacitor common line 2]5 via the storage capacitor voltage terminal 237.

Note that it is convenient for mounting if the drawer substrates 225, 226, 235° 236 are made of a flexible substrate such as an organic film.

Signal circuit boards 227-243. and scanning circuit board 22
An example of Nos. 2 to 224 is shown in FIG.

The circuit board 239 is made by fixing an integrated circuit element 239A on which a signal circuit or a scanning circuit is formed on an organic film or the like on which pattern wirings 239B and 239C are applied.

The pattern wiring 239B is an output terminal for a scanning voltage or a signal voltage, and the pattern wiring 239C is an input terminal for an image data signal and a power supply voltage for operating the integrated circuit element 239A.

FIG. 18 shows an example of a system to which the liquid crystal display according to the present invention is applied.

FIG. 18(A) shows an example in which a liquid crystal display is applied to the display section of a desktop computer. It is composed of a keyboard 2 and a liquid crystal display 3.

Compared to displays using conventional cathode ray tubes (hereinafter abbreviated as CRT), they are lighter and can be installed in a smaller area.

In particular, its features can be applied to systems that allow multiple operators to work simultaneously on a single computer 1 using multiple keyboards 2 and liquid crystal displays 3, as well as knee-rest type computers that require further weight reduction. is fully demonstrated.

Therefore, by using a liquid crystal display in the display section of a computer, it is possible to realize a lightweight, space-saving personal computer such as a notebook type computer.

FIG. 18(B) shows another application example of a liquid crystal display, in which a liquid crystal display is used as a part of the light shutter of a projection type display. The system consists of a projection section 4 including a liquid crystal display and an optical system. It consists of a screen 5 and a video signal processing section (not shown). The video signal input from the outside is converted by the video signal processing section into a signal format necessary for display on the liquid crystal display, such as a non-interlaced RGB digital signal, and an image is displayed on the liquid crystal display. This display image is focused on the screen E through the optical system.

Among these components, the optical shutter is the main factor that determines the dimensions of the optical system, and by using a liquid crystal display that can fit a large number of pixels into a small panel, the optical shutter can be made smaller. can be achieved, and the entire optical system can also be made smaller.

In addition, by using the small size and lightweight characteristics of liquid crystal displays, small color monitors and large wall-mounted televisions can be realized.

In addition, it can also be applied to large computer terminal devices, overhead projectors, computer-based learning devices, computer game devices, and the like.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to realize a liquid crystal display device that has a high quality product rate in the manufacturing process and has a high aperture ratio of the pixel portion, so that the manufacturing cost is low. Furthermore, it becomes possible to provide a liquid crystal display device with good display quality, which is useful for various image display device applications.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a pixel section according to an embodiment of the present invention, FIGS. 2 and 4 are plan views of a pixel section according to the prior art, and FIGS. 3 and 5 are respectively FIGS. 2 and 4. 6 is a cross-sectional view taken along line AA' in FIG. 1, and FIG. 7 is a plan view of the light shielding layer on the second substrate corresponding to the pixel portion in FIG. A plan view of the upper light-shielding layer, FIGS. 8 to 12 are plan views of pixel portions of other embodiments of the present invention, and FIG. 13 is a configuration of a liquid crystal display system using the liquid crystal display device of the present invention. 14 and 15 are configuration diagrams of other embodiments of the liquid crystal display module, FIG. 16 is a plan view of one embodiment of the liquid crystal display module corresponding to FIG. 15, and FIG. 17 is a signal diagram. 18(A) is a conceptual diagram of a desktop computer using the liquid crystal display device of the present invention, and FIG. 18(B) is a plan view of an embodiment of the circuit board and the scanning circuit board. FIG. 2 is a conceptual diagram of the projection display device used. 1... Computer body, 2... Keyboard, 3.
Liquid crystal display, 4... Projection unit, 5... Screen, 200... Display system, 201... Light source, 202... Liquid crystal display module, 203...
Light source adjustment circuit, 204... control circuit, 204
A...Image data generation circuit, 204B...Timing signal generation circuit, 205...Storage capacitor drive I! Il voltage generation circuit, 206... Common electrode drive voltage generation circuit, 207...
Signal circuit, 208-Scanning circuit, 209 Scanning line, 21
0 ・Signal line, 211 Thin film transistor, 212 ・Storage capacitor, 213 Common electrode terminal, 214 Liquid crystal, 215 ・
...Chichimu capacitance common line, 216...Brightness and contrast adjustment circuit, 217...Liquid crystal panel, 218...Information processing system, 22o...Signal supply board, 221...
Signal cable, 222-224...Scanning circuit board, 22
5,226・Common electrode voltage extraction board, 227~2
34...Signal circuit board, 235.236...-Common electrode voltage and capacitance voltage extraction board, 237.Storage capacitance voltage terminal, 238.Common electrode terminal, 239.Circuit board, 239A..Integrated circuit element, 239B , 239C・
- Pattern wiring, 601... first translucent insulating substrate,
602...Gate electrode/scanning line, 603...ITO film,
604...Non-transparent metal membrane, 605...SiNx film,
606...Semiconductor thin film, 607...Transparent pixel electrode, 6
08・Source electrode, 609・Train electrode and signal line,
610 - Region of the first substrate to be light-shielded. Eizu Me〆Zuu Ku〃 Eye■ Closed whisper map 2θθ Komazu 39b 23γC Me times

Claims (1)

[Claims] 1. A two-dimensional array of active elements, wiring for supplying signals to the active elements, and a transparent conductor electrically connected to each of the active elements, on a first transparent insulating substrate. a photosensitive pixel electrode and a capacitive element electrically connected to the pixel electrode; a counter electrode is provided on a second transparent insulating substrate; the first and second insulating substrates are opposed to each other; In a liquid crystal display device in which a liquid crystal material is sealed in a gap formed between insulating substrates, the pixel electrode also serves as one electrode of a pair of electrodes constituting the capacitive element, and the other electrode is transparent. It is composed of a conductive film and a non-light-transmitting conductive film, and at least a portion of the non-light-transmitting conductive film extends along an outer edge of the pixel electrode and overlaps at least a portion of the outer edge in a planar structure. A liquid crystal display device characterized by: 2. A direct view type or projection type image display device having the liquid crystal display device according to claim 1.