JPH04127128A - Active matrix display device - Google Patents

Abstract

PURPOSE:To cut off light which is made incident on a switching element and to prevent a leak between electrodes by providing an insulating light shield layer which covers the switching element on a substrate where the switching element is formed. CONSTITUTION:This device is equipped with a couple of insulating substrates 22 and 23 made of glass, quartz, etc., picture element electrodes 7 which are arrayed on one substrate 22 in matrix, a-TFT 25 as switching elements connected to the picture element electrodes 7. The insulating light shield layer 21 which covers each switching element 25 is formed. The light shield layer 21 is made of colored resin and formed by, for example, a spin coating method and the light shield layer 21 prescribes the gap between the couple of substrates 22 and 23. Consequently, the light which is made incident on the switching element 25 is cut off by the light shield layer 21 which covers the switching element 25 and the light shield layer 21 has insulating performance, so a leak between switching elements 25 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an active matrix display device, and in particular,
The present invention relates to an active matrix display device having an amorphous silicon thin film transistor as a switching element.

(Prior Art) FIG. 9 shows a cross-sectional view of the vicinity of a switching element of an active matrix display device that has been commonly used in the past. A schematic sectional view of the entire display device is shown in FIG. This display device includes a pair of insulating substrates 22 and 23, and pixel electrodes 7 arranged in a matrix on one substrate 22.
and an amorphous silicon thin film transistor (hereinafter referred to as [a
- TFTJ) 25.

A cross-sectional structure near the a-TFT 25 formed on the substrate 22 will be explained using FIG. 9. A gate electrode 1 is formed on a substrate 22, and the gate electrode 1 is covered with a gate insulating film 2 formed on the entire surface of the substrate 22. A semiconductor layer 3 made of amorphous silicon (hereinafter referred to as ra-3iJ) is formed on the gate insulating film 2 above the gate electrode 1. A contact layer 4.4 made of n3-3i is formed on the semiconductor layer 3.

A source electrode 5 is formed on one contact layer 4,
A train electrode 6 is formed on the other contact layer 4.

A part of the picture element electrode 7 is folded over the drain electrode 6 . The gate electrode 1 is connected to the gate bus wiring (not shown),
The source electrode 5 is connected to a source bus line (not shown). A protective film 8 is formed on the a-TFT 25, and an alignment film 12 is further formed on the entire surface of the substrate 22.

On the other substrate 23, a light shielding film 13 is formed which faces the a-TFT 25 and the portion between the picture element electrode 7 and the bus wiring. ``The light shielding film 13 is covered with the counter electrode 9 formed on the entire surface of the substrate 23. Furthermore, the counter electrode 9
An insulating film 10 and an alignment film 11 are formed thereon.

As shown in FIG. 10, a liquid crystal layer 20 is sealed between substrates 22 and 23, and the distance between substrates 22 and 23, that is, the cell thickness, is defined by a spacer 24. The spacer 24 is a small piece or ball of a certain size made of glass, plastic, ceramic, etc.
and 23 are sprinkled on one of the substrates before bonding them together.

The liquid crystal layer 20 is sealed with a sealing resin 26, and the liquid crystal injection port is sealed with a sealing resin 25.

In this display device, as a switching element, an a-T having an inverted staggered structure in which a gate electrode l is formed on the substrate 22 side is used.
FT is used. TFTs with an inverted staggered structure have the advantage that high quality TFTs can be obtained relatively easily with a high yield in the manufacturing process. However, since the a-3T used as the semiconductor layer 3 has photosensitivity, the inverted staggered a-TFT 25 is sensitive to light when strong light is irradiated from the direction indicated by the arrow 27 in FIG. , there is a problem that the characteristics as a semiconductor change. In order to prevent such an influence, the light shielding film 13 is provided.

The light shielding film 13 is originally provided to prevent light from leaking from the portion between the bus wiring and the picture element electrode 7. In the display device shown in FIG. 9, the light shielding film 13 has the function of preventing the above-mentioned light from leaking and the function of preventing light from entering the a-TFT 25.

(Problem to be solved by the invention) However, in recent years, insulating film forming technology has progressed, and the picture element electrode 7
By forming an insulating film between the pixel electrode 7 and the bus wiring, it is possible to form the picture element electrode 7 and the bus wiring in an overlapping manner. Therefore, it is no longer necessary to provide the light shielding film 13 for the purpose of preventing light leakage from the portion between the picture element electrode 7 and the bus wiring.

In addition, in a display device provided with the light-shielding film 13, in consideration of the positional shift that occurs when the substrates 22 and 23 are bonded together, the light-shielding film 13 is placed between the a-TFT 25, the pixel electrode 7, and the bus wiring. The width is approximately 10 μm larger than the width of the . Therefore, there is also the problem that the aperture ratio of the display device is reduced.

In order to solve the problem of misalignment, it has been considered to provide a metal light-shielding film with an insulating film sandwiched between the a-TFTs 25, but this tends to cause leakage between the source and drain electrodes, and the display device There is a problem in that it tends to cause a decrease in yield.

Furthermore, since the spacers 24 scattered to make the cell thickness constant as described above are also present on the picture element electrodes 7, there is a problem that display unevenness occurs due to agglomeration of the spacers 24. Projection type display devices also have the problem that image quality is degraded by spacers on picture element electrodes.

Furthermore, since a step is formed due to the difference in height between the a-TFT 25 and the picture element electrode 7, the spacer 24
There is a problem that the cell thickness is not uniform depending on whether the cell is located on T25 or on the picture element electrode 7.

The present invention solves these problems, and an object of the present invention is to provide an active matrix display device having a light shielding film that does not reduce the aperture ratio. Another object of the present invention is to provide an active matrix display device that does not cause display unevenness or deterioration in image quality due to spacers. Yet another object of the invention is to provide an active matrix display having uniform cell thickness.

(Means for Solving the Problems) An active matrix display device of the present invention includes a pair of insulating substrates, pixel electrodes arranged in a matrix on one of the pair of substrates, and an active matrix display device having a switching element connected to a picture element electrode, an insulating light-shielding layer covering the switching element being formed on one of the substrates; The purpose is achieved.

Further, the light shielding layer may define an interval between the pair of substrates.

Further, a configuration may be adopted in which a spacer for defining an interval between the pair of substrates is embedded in the light shielding layer.

(Function) In the active matrix display device of the present invention, light incident on the switching element is blocked by the light blocking layer covering the switching element. Since the light shielding layer has insulating properties, no leakage occurs between the electrodes of the switching element.

Furthermore, if the thickness of the light-shielding layer is set to a predetermined value, the cell thickness can be defined by the light-shielding layer, and there is no need to use a spacer. Further, the cell thickness can be made uniform.

Furthermore, by embedding the spacer in the light-shielding layer, a display device in which no spacer is present on the picture element electrode can be obtained, and image quality does not deteriorate due to the presence of the spacer on the picture element electrode. Furthermore, the cell thickness can also be made uniform.

(Example) Examples of the present invention will be described below.

FIG. 1 shows a sectional view of the vicinity of a switching element of an embodiment of an active matrix display device according to the present invention. A schematic sectional view of the entire display device is shown in FIG. This display device includes a pair of insulating substrates 22 and 23, picture element electrodes 7 arranged in a matrix on one substrate 22, and picture element electrodes 7 arranged in a matrix on one substrate 22.
a-TFT25 as a switching element connected to
has.

The cross-sectional structure near the a-TFT 25 formed on the substrate 22 will be explained using FIG. 1. A gate electrode 1 is formed on an insulating substrate 22 made of glass, quartz, etc.
The gate electrode 1 is covered with a gate insulating film 2 formed over the entire surface of the substrate 22. The gate electrode 1 is made of aluminum, tantalum, titanium, copper, etc., and the gate insulating film 2 is made of silicon nitride, silicon oxide, etc. A semiconductor layer 3 made of a-3t is formed on the gate insulating film 2 above the gate electrode 1. A contact layer 4.4 made of n" type a-3i is formed on the semiconductor layer 3. A source electrode 5 is formed on one contact layer 4, and a drain electrode is formed on the other contact layer 4. An electrode 6 is formed.The source electrode 5 and the drain electrode 6, like the gate electrode 1, are made of aluminum, tantalum, titanium,
Made of copper, etc. As a result of the above, the inverted staggered a-TFT2
5 are configured.

I To (Indium t
In.

A part of the picture element electrode 7 made of a material such as xide) is overlapped. In addition, the gate electrode 1 is a gate bus wiring (not shown)
In addition, the source electrode 5 is connected to a source bus wiring (not shown). A protective film 8 made of silicon nitride, silicon oxide, etc. is formed on the a-TFT 25 .

A light shielding layer 21 made of colored resin is formed on the protective film 8. In order to prevent leakage between the source electrode 5 and the drain electrode of the a-TFT 25, the light shielding layer 21 needs to have insulating properties.

In this example, Color Mosaic CK (trade name) manufactured by Fuji Hunt Electronics Technology Co., Ltd. was used as the light shielding layer 21. Other examples include polyimide, polyamide,
Resins such as polyamic acid and acrylic, carbon, dyes,
It is also possible to use one colored with a pigment or the like.

The transmittance of the light shielding layer 21 in the visible light range of 400 nm to 700 rv is preferably 5% or less.

In a normal liquid crystal display device, ultraviolet rays and infrared rays are cut by a filter, so it is only necessary to consider transmission 4 of only visible light. In this example, the colored resin layer serving as the light shielding layer 21 was formed using a spin cord. The thickness of the pale yellow resin layer is 2 μm. The circumference of the colored resin layer can be adjusted by changing the rotation speed and time of the spin cord. For example, when color mogaik CK is coated for 10 seconds at 1400 rpm, a colored resin layer with a thickness of about 1 μm is obtained, and the permeability of this colored resin layer at 550 nm is about 4.9%. After the colored resin layer was pre-baked, exposed to light and developed, it was finally fired to form the light-shielding layer 21.

Incidentally, it is also possible to adopt a configuration in which the above-mentioned protective film 8 is not provided, but if the insulation of the light-shielding layer 21 is not high, for example, the light-shielding layer 2
If ionic impurities are included in 1, a-
In order to prevent the characteristics of the TFT 25 from deteriorating, it is preferable to provide a protective film 8.

An alignment film 12 that regulates the alignment of liquid crystal molecules is formed on the entire surface of the substrate 22, covering the light shielding layer 2I.

The insulating substrate 23 facing the insulating substrate 22 is
Similarly, it is made of glass, quartz, etc. Couple electrodes 9 made of ITO are formed on the entire surface of the substrate 23. Further, an insulating film 10 and an alignment film 11 are formed on the solar electrode 9. The alignment films 11 and 12 are made of optomer AL10.
51 (manufactured by Japan Synthetic Rubber Co., Ltd.).

As shown in FIG. 2, a liquid crystal layer 20 is sealed between substrates 22 and 23. ZLI-22 is used in the liquid crystal layer 20.
93 (manufactured by Merck Japan) was used. Substrate 22 and substrate 2
3, that is, the cell thickness is defined by the spacer 24. The spacer 24 is a small piece or ball made of glass, plastic, ceramic, etc. and has a certain size, and is sprinkled on one of the substrates before the substrates 22 and 23 are bonded together. The liquid crystal layer 20 is sealed with a sealing resin 26, and the liquid crystal injection port is sealed with a sealing resin 25.

In the active matrix display device of this embodiment, light entering the a-TFT 25 from the direction indicated by the arrow 27 in FIG. 1 is blocked by the light blocking layer 21 formed covering the a-TPT. In order to examine the light blocking effect of the light blocking layer 21, changes in the threshold value of the a-TFT 25 due to light irradiation aging were measured. The display device used in the measurements was a normally white mode projection active matrix liquid crystal display device.

A filter for cutting ultraviolet rays and infrared rays is provided on the light incident side of the display device. The measurement results are shown in FIG. In FIG. 8, the horizontal axis is the light irradiation aging time t (time), and the vertical axis is the change in gate low voltage at which the blue light transmittance becomes 10% of the maximum transmittance. ■I. , t indicates that the change in a-TPT characteristics due to long-term image projection is large. 8th
As shown in the figure, it can be seen that the change in the a-TPT characteristics of the display device of this example is smaller than that of the conventional display device.

Further, the light shielding layer 21 is a substrate 2 on which a-TPT is formed.
Since the substrates 22 and 23 are formed on the substrate 2, the positional shift that occurs when the substrates 22 and 23 are bonded together does not occur. Therefore, the aperture ratio does not decrease. Further, since the light shielding layer 21 is made of an insulating resin, no leakage occurs between the source electrode 5 and the drain electrode 6.

Actual W Shadow A sectional view of the vicinity of the a-TPT 25 of another embodiment of the active matrix display device of the present invention is shown in FIG. In this embodiment, an interlayer insulating film 14 is formed between the gate insulating film 2 and the picture element electrode 7.

The interlayer insulating film 14 is formed on a source bus wiring (not shown) connected to the source electrode 5, and the picture element electrode 7 is superimposed on the source bus wiring with the interlayer insulating film 14 in between.

In the a-TFT 25, the interlayer insulating film 14 is formed on the source electrode 5 and the drain electrode 6, and the drain electrode 6 and the pixel electrode 7 are electrically connected by the contact pole electrode 5 formed on the interlayer insulating film 14. ing. Further, the picture element electrode 7 is also overlapped on the source electrode 5. With such a configuration, the area of the picture element electrode 7 can be increased, and the aperture ratio of the display screen can be improved.

Changes in light irradiation aging time t and gate low voltage Vtho when this embodiment is applied to a normally white mode projection type active matrix liquid crystal display device. , is shown in Figure 8. As shown in FIG. 8, it can be seen that the change in the a-TPT characteristics of the display device of this example is smaller than that of the conventional display device.

Inuarashi Goji In the above-mentioned Examples 1 and 2, the spacer 2 is placed on the light shielding layer 21.
The cell thickness is different between the portion where No. 4 exists and the portion where No. 4 does not exist. Depending on the birefringence of the liquid crystal material and the display mode, even more precise cell thickness control is required. This embodiment can be applied to such a case.

FIG. 4 shows a cross-sectional view of the vicinity of the a-TFT 25 of this embodiment. A schematic sectional view of the entire display device is shown in FIG. This display device is similar to Example 1 except that the thickness of the light shielding layer 21 is large and the spacer 24 is not used.
It is similar to In this embodiment, the distance between the substrates 22 and 23, that is, the cell thickness, is defined by the light shielding layer 21.

In this example, the same color mosaic CK as described above was used as the colored resin, and the rotation speed during the spin cord was set to 3 Orpm.
By doing so, the thickness of the light shielding layer 21 was set to 5 μm.

In this embodiment, since the cell thickness is defined by the light shielding layer 21, there is no need to use a spacer. Therefore, display unevenness and image quality deterioration due to spacers do not occur.

FIG. 8 shows the relationship between the light irradiation aging time t and the gate low voltage change vthoot when this embodiment is applied to a normally white mode projection type active matrix liquid crystal display device. As shown in FIG. 8, it can be seen that the change in a-TPT characteristics of the display device of this example is also smaller than that of the conventional display device.

This example is based on a-T having the structure shown in FIG. 3 of Example 2.
It can also be applied to display devices having PT.

If the Soaran Takumi clay cell thickness exceeds 5 μm or if the structure shown in Example 3 cannot be applied due to restrictions due to the material of the light shielding layer 21, it is necessary to use a spacer.

However, as described above, the presence of the spacer on the picture element electrode may reduce the deterioration of image quality in a projection display device or the like. The display device of this embodiment can be used in such cases.

FIG. 6 shows a cross-sectional view of the vicinity of the a-TFT 25 of this embodiment. A schematic sectional view of the entire display device is shown in FIG. This display device is similar to Example 1 except that spacers 24 are embedded in the light shielding layer 21.

The spacer 24 can be embedded in the light shielding layer 21 by the following two methods.

(2) A method of forming the light shielding layer 21 in the same manner as described above using a colored resin in which spacers 24 are dispersed in advance.

■Spacers 24 are added to the colored resin layer before forming the light shielding layer 21.
A method of forming a light shielding layer 21 by applying pressure and embedding the resin layer, and then performing main firing of the resin layer.

In this example, the latter method, which is superior in terms of patterning accuracy, was used. The spacer 24 does not need to be embedded in all the light shielding layers 21 located on each a-T F T,
It is sufficient that the number can maintain the cell thickness. Furthermore, if the spacer 24 is colored, the light shielding properties can be further improved. In this example, a display device in which the spacer 24 was not colored and a display device in which the spacer 24 was colored black were manufactured.

FIG. 8 shows the relationship between the light irradiation aging time t and the gate low voltage change Vthoot when this embodiment is applied to a normally white mode projection type active matrix liquid crystal display device. As shown in FIG. 8, it can be seen that the change in the a-TPT characteristics of the display device of this example is smaller than that of the conventional display device. Further, it can be seen that the light shielding properties are higher when the spacer 24 is colored.

This example is based on a-T having the structure shown in FIG. 3 of Example 2.
It can also be applied to display devices having PT.

Table 1 shows the non-uniform cell occurrence rates obtained for the display devices of Examples 1.3 and 4. In Table 1, the incidence of display devices having non-uniformity in the distance between the substrates 22 and 23 of 1 μm or more is shown as the non-uniform cell occurrence rate. Furthermore, a-TFT
The difference in height due to the difference in height between the pixel electrode 7 and the pixel electrode 7 is approximately 0. It is 8 μm.

Table 1 In the display device of Example 3, it is somewhat difficult to uniformly apply the colored resin to a thickness of 5 μm, so the uniform cell generation rate is higher than that of the display device of Example 4 using the spacer 24. However, in both Examples 3 and 4, the spacer 24
The non-uniform cell generation rate is lower than that of the display device of Example 1, in which the particles were dispersed in the same manner as before.

(Effects of the Invention) The active matrix display device of the present invention has an insulating light-shielding layer that covers the switching elements on the substrate on which the switching elements are formed, and therefore blocks light that enters the switching elements. Moreover, no leakage occurs between the electrodes of the switching element. Further, since the active matrix display device of the present invention has a light shielding layer that defines the distance between the substrates constituting the display device, or a light shielding layer in which a spacer that defines the distance is embedded, the spacer on the picture element electrode image quality will no longer deteriorate due to
Cell thickness can be made uniform.

Therefore, according to the present invention, an active matrix display device with high image quality can be obtained with high yield.

4. Nona Se H Fig. 1 is a sectional view of Example 1 of the active matrix display device of the present invention, Fig. 2 is a schematic sectional view of the entire display device of Fig. 1, and Fig. 3 is an implementation of the present invention. 4 is a sectional view of Example 3 of the present invention, FIG. 5 is a schematic sectional view of the entire display device of FIG. 4, and FIG. 6 is a sectional view of Example 4 of the present invention. , FIG. 7 is a schematic cross-sectional view of the entire display device shown in FIG. 6, FIG. 8 is a diagram showing changes in the threshold value of a-TFT due to light irradiation aging, and FIG. 9 is a cross-sectional view of a conventional active matrix display device. , FIG. 10 is a schematic cross-sectional view of the entire display device of FIG. 9.

1... Gate electrode, 2... Gate insulating film, 3...
Semiconductor layer, 4... Contact layer, 5... Source electrode, 6... Drain electrode, 7... Picture element electrode, 8...
Protective film, 9... Counter electrode, 20... Liquid crystal layer, 21.
...Light shielding layer, 22゜23...Insulating substrate, 24...
Spacer, 25...a-TFT.

that's all Figure 1 Figure 2 40th Fifth figure Figure 6 Figure 7 Figure 8 Agenk poetry book (time)

Claims (1)

[Scope of Claims] 1. A pair of insulating substrates, picture element electrodes arranged in a matrix on one of the pair of substrates, and a switching element connected to the picture element electrodes; An active matrix display device comprising: an insulating light shielding layer covering the switching element formed on the one substrate. 2. The active matrix display device according to claim 1, wherein the light shielding layer defines a distance between the pair of substrates. 3. The active matrix display device according to claim 1, wherein a spacer for defining an interval between the pair of substrates is embedded in the light shielding layer.