JPH0713198A - Liquid crystal display substrate - Google Patents

Abstract

PURPOSE:To prevent the malfunction of semiconductor switching elements by photoirradiation. CONSTITUTION:This liquid crystal substrate is constituted by forming the semiconductor switching elements TFTs on the liquid crystal side surface of the first transparent substrate SUB1 of the respective transparent substrates arranged to face each other via a liquid crystal LC and forming a light shielding film BM for prohibiting the incident of the incident light through the second transparent substrate SUB2 on the semiconductor switching elements TFTs on the liquid crystal side surface of the other second transparent substrate SUB2. The liquid crystal display substrate is used by arranging a back light on the first transparent substrate side. A layer to absorb light is laminated on the liquid crystal side surface of the light shielding film BM.

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 substrate,
For example, the present invention relates to a liquid crystal display substrate for forming an image in charge of each color when a color image is displayed on a screen by superimposing images for red (R), green (G), and blue (B).

[0002]

2. Description of the Related Art In this type of liquid crystal display substrate, a backlight is arranged on the side opposite to the screen, and the liquid crystal display substrate is driven to display while the light of the backlight is being transmitted, so that it is displayed on the screen. For example, an image in charge of red (R) is formed.

Therefore, the light intensity of the backlight is
It is incomparably larger than that of liquid crystal substrates used for other purposes.

On the other hand, in recent years, as the liquid crystal display substrate,
A so-called active matrix type liquid crystal display substrate having a semiconductor switching element (TFT) formed by, for example, a thin film technique for each pixel has come to be used.

As such a liquid crystal display substrate,
For example, if there is a first transparent substrate and a second transparent substrate which are arranged to face each other with a liquid crystal in between, and a backlight is arranged on the side of the first transparent substrate, the surface of the first transparent substrate on the liquid crystal side. It is known that a semiconductor switching element is formed in the. In this case, the semiconductor switching element has a so-called inverted staggered structure in which, for example, an Al layer constituting the gate electrode thereof also serves as a light shielding film so that light from the backlight does not malfunction.

And, on the liquid crystal side surface of the second transparent substrate,
A light shielding film for blocking light irradiation from the external light to the semiconductor switching element is formed so as to cover the semiconductor switching element.

An active matrix type liquid crystal display device using thin film transistors is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-309921 and "1.
2.5-inch active matrix color LCD ", Nikkei Electronics, pages 193-210, 1986 12
Known on the 15th of March, published by Nikkei McGraw-Hill, Inc.

[0008]

However, it has been found that the liquid crystal display substrate having such a structure still has a malfunction due to light irradiation in the semiconductor switching element.

That is, of the light from the backlight,
It has been found that this is due to the presence of light incident on the light shielding film formed on the second transparent substrate side after passing through the first transparent substrate and the liquid crystal.

When the light of the backlight incident on the light-shielding film is present, this light is reflected on the surface of the light-shielding film formed of a metal layer having an excellent light-shielding property, and this reflected light is incident on the semiconductor switching element. This is because it will end up.

As described above, when the semiconductor layer forming the semiconductor switching element is irradiated with light, so-called photoconductivity is generated in the semiconductor layer, which causes the semiconductor switching element to malfunction.

Therefore, the present invention has been made under such circumstances, and an object thereof is to provide a liquid crystal display substrate capable of preventing malfunction of a semiconductor switching element due to light irradiation. is there.

[0013]

In order to achieve such an object, the present invention is basically based on one of the first transparent substrates of the respective transparent substrates arranged to face each other with a liquid crystal interposed therebetween. A semiconductor switching element is formed on the surface on the liquid crystal side, and light incident through the second transparent substrate on the surface on the liquid crystal side of the other second transparent substrate is incident on the semiconductor switching element. In a liquid crystal display substrate in which a light-blocking film that blocks light is formed, and a backlight is disposed on the first transparent substrate side, the liquid-crystal-side surface of the light-blocking film absorbs light. It is characterized in that the layers are laminated.

[0014]

In the liquid crystal display substrate configured as described above, among the light from the backlight, the light that passes through the first transparent substrate and the liquid crystal and enters the light-shielding film formation region on the second transparent substrate side is the light-shielding film. Will be absorbed by the light absorbing layer laminated on the surface of the.

Therefore, the light is not reflected on the light-shielding film and does not enter the semiconductor switching element formed on the first transparent substrate side, and malfunction of the semiconductor switching element due to light irradiation is prevented. become able to.

[0016]

FIG. 2 is a circuit diagram showing an embodiment of an equivalent circuit of a liquid crystal display substrate according to the present invention, showing a circuit of a portion corresponding to one pixel among a large number of pixels arranged in a matrix. ing. Although the figure is a circuit diagram, it is drawn corresponding to the actual geometrical arrangement.

In the figure, data lines (video signal lines) DL extending in the y direction in the figure are arranged in parallel in the x direction, and gate lines (scanning signal lines) GT extending in the x direction.
Are arranged side by side in the y direction.

A region surrounded by the data line DL and the gate line GT corresponds to one pixel,
A thin film transistor TFT is arranged in a part of the periphery of this region. The thin film transistor TFT has a so-called MOS structure, and its gate electrode is connected to the gate line GT and the source electrode is connected to the data line DL.

That is, the gate line GT (in the figure, GT
n) while the signal is given to the data line DL
The signal from (DLn in the figure) is the thin film transistor T
It will be output to the drain electrode of the FT.

The drain electrode of the thin film transistor TFT is connected to the pixel electrode, and thereby a voltage is applied to the liquid crystal arranged between the pixel electrode and another pixel electrode (common electrode COM) arranged to face the pixel electrode. It is like this.

Then, the drain electrode of the thin film transistor TFT and the gate line (in the figure, G
The storage capacitor element Cadd is connected between Tn-1) and Tn-1). The storage capacitor element Cadd is formed for the purpose of reducing the influence of the gate potential change on the potential (midpoint potential) of the pixel electrode when the thin film transistor TFT switches.

FIG. 1 is a sectional view showing an embodiment of a liquid crystal display substrate according to the present invention, showing a section of a portion corresponding to one pixel.

In the figure, a first transparent substrate SUB1 and a second transparent substrate SUB2 which are opposed to each other with the liquid crystal LC interposed therebetween are arranged.

The first transparent substrate SUB1 is constructed as follows.

First, a silicon oxide film SIO1 is formed on the entire surface of the liquid crystal side surface of the first transparent substrate SUB1 by, for example, a dipping process.

Then, as described above, the silicon oxide film SIO is formed.
The gate line GT (which extends from the front side to the back side in the drawing) made of, for example, an Al film, and one electrode Cad of the storage capacitor Cadd are formed on the surface on which 1 is formed.
d1 is formed.

Further, for example, a silicon nitride film GI is formed on the surface of the silicon oxide film SIO1 on which the gate line GT and the electrode Cadd1 are formed. The silicon nitride film GI also serves as the gate insulating film of the thin film transistor TFT, which will be described in detail later, and is therefore set to have a film thickness having such a function.

Further, a pixel electrode ITO1 made of a transparent conductive film is formed on the surface of the silicon nitride film GI so as to overlap with the electrode Cadd1 in a part of its periphery. As a result, the overlapping portion of the electrode Cadd1 and the pixel electrode ITO1 constitutes the storage capacitor element Cadd having the silicon nitride film GI interposed therebetween as a dielectric.

Further, a semiconductor layer AS made of, for example, amorphous silicon is provided in a part of the periphery of the pixel electrode ITO1 and this semiconductor layer AS serves as a semiconductor layer constituting the thin film transistor TFT. . In this case, the gate electrode is a partial region of the gate line GT arranged via the silicon nitride film GI.
This is why the thin film transistor TFT is called a so-called inverted stagger structure.

A drain electrode SD1 and a source electrode SD2 are formed on the thin film transistor TFT, the drain electrode SD1 is connected to the data line DL, and the source electrode SD2 is connected to the pixel electrode ITO1.

The drain electrode SD1 and the data line DL are formed integrally with each other, and like the source electrode SD2, they are, for example, a Cr layer d ₂ and an Al layer d _3.
It has a sequentially laminated structure. The Cr layer d ₂
A high-concentration semiconductor layer d _{1 serving as a} contact layer is interposed at a connection portion between the semiconductor layer AS and the semiconductor layer AS.

Further, such a thin film transistor TF
A protective film PSV1 made of, for example, silicon nitride is formed on the surface of the silicon nitride film GI on which the T and the pixel electrode ITO1 are formed, and an alignment film ORI1 is formed on the surface of the protective film PSV1.

A silicon oxide film SIO1 and a deflection film POL1 are laminated on the entire surface of the opposite surface of the first transparent substrate SUB1 thus surface-treated.

The second transparent substrate SUB2 is constructed as follows.

First, a silicon oxide film SIO2 is formed on the entire surface of the second transparent substrate SUB2 on the liquid crystal side by, for example, a dipping process.

A light-shielding film BM made of, for example, a Cr layer is formed in one region of the surface of the silicon oxide film SIO2. The reason why the Cr layer is used as the material of the light shielding film BM is that the light shielding property is perfect. The light-shielding film BM is for preventing the light from passing through the second transparent substrate SUB2 and entering the thin film transistor TFT formed on the first transparent substrate SUB1 side, and is superimposed on the formation region of the thin film transistor TFT. Is formed.

In this embodiment, in particular, the light absorption layer FIL is formed on the surface of the light shielding film BM so as to cover the light shielding film BM. The light absorption layer FIL is made of, for example, a synthetic resin layer, and the synthetic resin layer contains, for example, a black dye.

Further, the light shielding film BM and the light absorption layer FIL
Of the silicon oxide film S other than the region where the laminated body of
On the IO2 surface, a transparent synthetic resin layer WHI for eliminating the step due to the laminated body is formed.

The protective film P made of a silicon nitride film is formed on the surfaces of the light absorption layer FIL and the synthetic resin layer WHI.
The SV2 is formed, and the common pixel electrode ITO2 made of a transparent conductive film is formed on the surface of the protective film PSV2. An alignment film ORI2 is formed on the surface of the common pixel electrode ITO2.

A silicon oxide film SIO2 and a deflecting film POL2 are laminated on the entire surface of the opposite surface of the second transparent substrate SUB2 thus surface-treated.

The first transparent substrate SUB having the above structure
The first and second transparent substrates SUB2 are arranged to face each other with the liquid crystal LC in between. A spherical spacer BZ is mixed in the liquid crystal LC, and the first transparent substrate SUB1
The distance between the second transparent substrate SUB2 and the second transparent substrate SUB2 is uniform.

In this liquid crystal display substrate, the backlight is arranged so as to enter from the first transparent substrate SUB1 side.

The liquid crystal display substrate having such a structure passes through the first transparent substrate SUB1 and the liquid crystal LC of the light from the backlight and passes through the light shielding film B on the second transparent substrate SUB2 side.
Light incident on the formation region of M (shown by a solid arrow in FIG. 1)
Will be absorbed by the light absorption layer FIL that absorbs the light stacked on the surface of the light shielding film BM.

Therefore, the light is not reflected by the light shielding film BM and is not incident on the thin film transistor TFT formed on the first transparent substrate SUB1 side (FIG. 1).
There is no light irradiation as shown by the dotted arrow in),
It is possible to prevent malfunction of the thin film transistor TFT due to light irradiation.

3 to 6 show the second transparent substrate SU.
It is process drawing which shows one Example of the manufacturing method of B2.

Step 1. (FIG. 3) First, the second transparent substrate SUB2 is prepared, and the silicon oxide film SIO2 is formed on at least the main surface of the liquid crystal side.

Then, a Cr layer is formed on the entire surface of the silicon oxide film SIO2, and the Cr layer is subjected to selective etching by a photolithography technique to leave the remaining Cr.
The layer is the light-shielding film BM.

Further, a synthetic resin film containing, for example, a black pigment is formed on the entire surface of the silicon oxide film SIO2 on which the light shielding film BM is formed.

Step 2. (FIG. 4) This synthetic resin film FIL is subjected to selective etching by a photolithography technique to leave the synthetic resin film formed on the surface of the light shielding film BM, which is used as a light absorbing layer.

Step 3. (FIG. 5) A transparent synthetic resin film WH1 containing no pigment is formed on the entire surface of the silicon oxide film SIO2 on which the light absorption layer FIL is formed, and selective etching is performed by a photolithography technique. , Light absorption layer FIL
The synthetic resin film WH1 is left in the region where is not formed.

Here, the synthetic resin film WH1 is formed such that the surface thereof is substantially flush with the surface of the light absorption layer FIL, whereby the synthetic resin film WH1 is a region where the light absorption layer FIL is not formed. Is formed to be embedded in the.

Step 4. (Figure 6) Thus the entire surface of the second transparent substrate SUB2 light absorption layer FIL and synthetic resin film WH1 is formed, a transparent electrode ITO ₂ consisting of the protective film PSV2 and ITO made of silicon nitride.

In the above-mentioned embodiments, the synthetic resin film containing the black pigment is used as the light absorption layer FIL, but the invention is not limited to this. Pigments of other colors may be contained, and no synthetic resin film is used.

[0054]

As is apparent from the above description,
According to the liquid crystal display substrate of the present invention, malfunction of the semiconductor switching element due to light irradiation can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a liquid crystal display substrate according to the present invention, showing a cross section of a portion corresponding to one pixel.

FIG. 2 is a circuit diagram showing an embodiment of an equivalent circuit of a liquid crystal display substrate according to the present invention, showing a circuit of a portion corresponding to one pixel among a large number of pixels arranged in a matrix.

FIG. 3 is a step 1. showing an embodiment of a method for manufacturing a liquid crystal display substrate according to the present invention. FIG.

FIG. 4 is a step 2. showing an embodiment of a method for manufacturing a liquid crystal display substrate according to the present invention. FIG.

FIG. 5 is a step 3. showing an embodiment of a method for manufacturing a liquid crystal display substrate according to the present invention. FIG.

FIG. 6 is a process showing an embodiment of a method of manufacturing a liquid crystal display substrate according to the present invention. FIG.

[Explanation of symbols]

 SUB1 first transparent substrate SUB2 second transparent substrate TFT thin film transistor BM light shielding film FIL light absorption layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Owada 3300 Hayano, Mobara, Chiba Prefecture, Electronic Devices Division, Hitachi, Ltd. (72) Inventor Masahiko Suzuki 3300, Hayano, Mobara City, Chiba Hitachi, Ltd. Electronic Device Business Department

Claims (1)

[Claims] 1. A semiconductor switching element is formed on the liquid crystal side surface of one of the first transparent substrates of the respective transparent substrates arranged to face each other with a liquid crystal interposed therebetween, and the liquid crystal of the other second transparent substrate is formed. A light-shielding film is formed on a side surface of the first transparent substrate to prevent light incident through the second transparent substrate from entering the semiconductor switching element. In the liquid crystal display substrate, the liquid crystal display substrate is characterized in that a light absorbing layer that absorbs light is laminated on the liquid crystal side surface of the light shielding film.