JPH0943636A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high numerical aperture and bright display without adding a novel process or companied with the defective orientation of a liquid crystal in a liquid crystal display device of an active matrix driving system. SOLUTION: An insulated-light shielding layer 19 is formed on a TFT 10 and wirings installed on an active matrix substrate side. The light shielding layer 19 is further extended onto a pixel electrode 18 to form apertures which are narrower than a light shielding layer 32 on the counter substrate side. Thus, the formation of the apertures in the patterning process for a bonding pad and the patterning of the light shielding layer with high accuracy are possible, thereby allowing the fomation of the wide apertures, thereby increasing the numerical aperture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and particularly to a thin film transistor (hereinafter referred to as "TFT").
The present invention relates to an active matrix drive type liquid crystal display device using the.

[0002]

2. Description of the Related Art FIG. 3 shows a sectional view of a cell of a conventional active matrix drive type liquid crystal display device. In the figure, 1 is a flat first substrate provided with an active matrix circuit,
A TFT 10 including a source 13 (or drain), a channel region 11, a drain (or source) 12, a gate electrode 17, and a gate insulating film 14 is formed. TF
The drain 12 of T10 is connected to the pixel electrode 18, the source 13 is connected to the metal wiring 16, and the alignment layer 20 is formed on the surface. Reference numeral 15 is an insulating layer that insulates the gate electrode 17 from the channel region 11. Reference numeral 2 is a second substrate which constitutes a counter substrate, on which a common electrode 31, a light-shielding film 32, and an alignment film 30 are formed, which are bonded to an active matrix substrate via a spacer, and the liquid crystal 3 is held in the space. Polarizing plates 4 are provided outside the first substrate 1 and the second substrate 2, respectively.

[0003]

It is difficult to manufacture a high-definition and high-density liquid crystal display device having a large number of pixels with the above-mentioned conventional structure. The reason is as follows.

In the active matrix type liquid crystal display device, the bonding accuracy between the first substrate and the second substrate is 1
It is as large as μm. On the other hand, in order to prevent malfunction due to light, the TFT and the wiring are covered with a light shielding layer. In FIG. 3, the light shielding film 32 corresponds to this. That is, although formed on the second substrate, TFTs and wirings to be shielded are formed on the first substrate, and in order to bond them within the above accuracy, the shielded region must be formed wider than necessary. In addition, the aperture ratio was low and it was difficult to obtain a bright display.

In order to increase the aperture ratio within the above-mentioned bonding accuracy, a light-shielding layer may be formed on the first substrate. In that case, the alignment accuracy of the light-shielding layer and the TFT or wiring is reduced by patterning the light-shielding layer. If an exposure device is used, it can be suppressed to about 0.1 μm. However, when the light shielding layer is provided on the first substrate, there are the following problems.

First, a new film forming / patterning step is added to newly provide the light shielding layer, which increases the manufacturing cost.

Secondly, since a metal or a conductive metal compound is generally used for the light-shielding layer, such a light-shielding layer acts as a stray capacitance with respect to the capacitance sandwiching the liquid crystal,
It disturbs the alignment of the liquid crystal.

An object of the present invention is to solve the above problems and provide a liquid crystal display device having a high aperture ratio and a bright display without causing an increase in manufacturing cost and liquid crystal alignment defects.

[0009]

A liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal is sandwiched between an active matrix substrate using a thin film transistor as a switching element and a counter substrate having a common electrode. Each have a light-shielding layer, and the light-shielding layer provided on the active matrix substrate forms an opening by partially covering the wiring, the entire surface of the thin film transistor, and the pixel electrode, and is less than the opening of the light-shielding layer provided on the counter substrate side. The opening of the light shielding layer provided on the active matrix substrate is narrower.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view (one pixel) of an embodiment of a liquid crystal display device of the present invention. FIG. 2 is an equivalent circuit thereof. In the figure, the same reference numerals as in FIG. 3 indicate the same parts as in FIG. A feature of the present invention is that an insulating light-shielding layer 19 is provided on the TFT 10 and the pixel electrode 18, and that the opening of the light-shielding layer 19 is narrower than the opening of the light-shielding layer 32 and determines the opening area of the pixel. There is something to do.

The purpose of light shielding in the liquid crystal display device is
Secondly, it is to prevent the leak current of the TFT due to the light irradiation, and secondly to prevent the alignment disorder of the liquid crystal due to the step of the film around the pixel electrode 18 and the seepage of the electric field from the adjacent pixel. At this time, it is necessary to shield the TFT or the region where the alignment disorder is large with a light-shielding layer having a high light-shielding effect, but the region where the alignment disorder is small may have some light-shielding effect.

In the liquid crystal display device of the present invention, by using a material having a high light-shielding effect such as metal for the light-shielding layer 32 on the counter substrate side, it is possible to sufficiently shield the TFT 10 and the peripheral portion of the TFT 10 where alignment disorder is large. Further, the light-shielding layer 19 formed on the active matrix substrate has an insulating property, and the light-shielding effect is low, but the region shielded only by the light-shielding layer 19 is only the region on the pixel electrode 18 in which the alignment disorder is small. Withstand use.

In the present invention, since the light-shielding layer 19 shields light in the region where the alignment disorder is small, the opening of the light-shielding layer 32 is
It is not necessary to follow the bonding accuracy between the counter substrate and the active matrix substrate as in the conventional case, and the patterning of the light-shielding layer 19 that determines the opening region has a higher positioning accuracy than the bonding accuracy of the two substrates. The area for absorbing the light does not need to be enlarged, and an opening wider than the conventional one can be formed.

Further, since the light shielding layer 19 is insulative,
Since it also functions as a protective film for the region covered by the light shielding layer 19 and the opening can be patterned in the same step as the patterning of the bonding pad, it is not necessary to add a new step. Further, in the structure in the opening, the pixel electrode 18
Since only the alignment film 20 is present on the upper side, the upper and lower substrates have the same structure with respect to the liquid crystal as a center, there is no asymmetry of the applied voltage, and burn-in of liquid crystal molecules due to the residual DC component applied to the liquid crystal, etc. Problems are prevented.

In the present invention, an insulating material is used for the light-shielding layer 19. Specifically, a metal nitride oxide is suitable, for example, Ta _x O _y N _1-xy , Ti _x O _y N _{1-. xy} is preferably used. A resin such as an acrylic carbon resin obtained by adding carbon to an acrylic resin such as PMMA can also be used.

The liquid crystal display device of the present invention is preferably manufactured by a conventional manufacturing method. Therefore, the light shielding layer 19 is the first
It is obtained by forming the TFT 10 and the pixel electrode 18 on the substrate 1 by a conventional method, forming an insulating film, and then patterning.

For example, when Ta _x O _y N _1-xy is used, the film forming conditions are a total pressure of 7.5 mTorr, a substrate temperature of 200 ° C., a power of 2 kw, an Ar flow rate ratio of 40%, and an N ₂ flow rate ratio of 36%. A film having a film thickness of 200 nm is formed with an O ₂ flow rate ratio of 24% to obtain a light shielding layer 19 having a transmittance of 5%. Further, the transmittance and the resistivity of the light shielding layer 19 can be set by changing the O ₂ flow rate and the N ₂ flow rate.

When an acrylic carbon resin is used, since the resin functions like a negative resist, patterning can be performed by coating, exposing, and developing by spin coating. TMAH or sodium carbonate is used for development.

After forming the light-shielding layer 19, the opening is determined by resist patterning and dry etching. During this patterning, the pads for wire bonding are continuously opened.

After that, the liquid crystal display device of the present invention is completed through processes such as dicing, alignment film formation, rubbing, printing of a sealing material, bonding with a counter substrate, and liquid crystal injection.

[0021]

As described above, according to the present invention,
A liquid crystal display device having a high aperture ratio and a bright display is provided without increasing manufacturing cost by adding new steps and without lowering display characteristics. Therefore, a high-definition and high-density liquid crystal display device with an increased number of pixels is realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of one pixel of a liquid crystal display device of the present invention.

FIG. 2 is an equivalent circuit of one pixel of the liquid crystal display device of the present invention.

FIG. 3 is a cross-sectional view of one pixel of a conventional liquid crystal display device.

[Explanation of symbols]

 1 1st substrate 2 2nd substrate 3 Liquid crystal 4 Polarizing plate 10 TFT 11 Channel region 12 Drain 13 Source 14 Gate insulating film 15 Insulating layer 16 Metal wiring 17 Gate electrode 18 Pixel electrode 19 Light-shielding layer 20, 30 Alignment film 31 Common electrode 32 Shading layer

Claims (3)

[Claims] 1. A liquid crystal display device comprising a liquid crystal sandwiched between an active matrix substrate using a thin film transistor as a switching element and a counter substrate having a common electrode, both substrates having a light-shielding layer. The provided light-shielding layer partially covers the wiring, the entire surface of the thin film transistor, and the pixel electrode to form the opening, and the opening of the light-shielding layer provided on the active matrix substrate is more than the opening of the light-shielding layer provided on the counter substrate side. Liquid crystal display device characterized by being narrower. 2. The liquid crystal display device according to claim 1, wherein the light shielding layer contains a metal nitride oxide. 3. The liquid crystal display device according to claim 1, wherein the light shielding layer contains an acrylic carbon resin.