JPS6017720A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To protect a TFT by an inorganic insulating layer, to stabilize characteristics, and also to prevent an adverse influence exerted on a device by an organic insulating layer, even if a crack is generated on the inorganic insulating layer, by forming additionally the organic insulating layer on the inorganic insulating layer. CONSTITUTION:An insulating layer for covering semiconductor layers 3 and 3' for constituting a thin film transistor TFT is formed by two layers, namely, an inorganic insulating layer 6a and an organic insulating layer 6b. A light shielding layer 9 and 9' are formed by forming a metal such as Al, etc. on the organic insulating layer 6b by a vapor depositing method, etc., and thereafter, leaving its metallic layer to a desired shape and size by means of photolithoetching, etc. An oriented layer 10 is formed so as to cover the organic insulating layer 6b and the light shielding layer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid crystal display device, and particularly to a liquid crystal display device having a thin film transistor (TPT) array for switching each pixel.

[Prior Art] A liquid crystal display device generally has a structure in which a liquid crystal is sandwiched between two substrates. Electrodes and other elements are formed on the liquid crystal side of this substrate, and display is performed by controlling the state of the liquid crystal using the elements. Electrodes are uniformly formed on the surface of one of the two substrates, and a plurality of electrodes in a small block pattern (pixel) having an appropriate shape are formed on the surface of the other substrate. In recent years, TF for switching for each pixel has been installed on the substrate surface on the pixel electrode side.
Attachment of the T-array is performed. FIG. 1 is a schematic cross-sectional view of a liquid crystal display device having such a TFT array, where S and S' are transparent substrates such as glass, 1 and 1' are gate electrodes, and 2 and 2' are transparent substrates such as glass. is an insulating layer, 3 and 3' are semiconductor layers, 4 and 4' are source electrodes, 5 and 5' are drain electrodes,
6 is an insulating and alignment layer, 7 is a liquid crystal, and 8 is a transparent electrode.

When a photoconductive semiconductor is used, it is preferable to avoid exposing it to light as much as possible in order to stabilize the switching characteristics.

For this purpose, a liquid crystal display device as shown in a schematic cross-sectional view in FIG. 2 is used. That is, here, in the device shown in FIG. 1, on the insulating and alignment layer 6 covering the TFT array, light shielding layers 9 and 9' are further formed at positions corresponding to the semiconductor layers. Metal is generally used for the light shielding layer.

In the above liquid crystal display devices, inorganic materials such as alumina, metal oxides such as titanium oxide, and silicon compounds such as silicon nitride and silicon dioxide have conventionally been used as the insulating layer. However, in order to cover TPT, a certain thickness or more is required, and these thin films of inorganic materials have the drawback that as the film thickness increases, film distortion increases and cracks are likely to occur. If a rack occurs like this, the TPT will also be destroyed at the same time, so the TP
T is not protected, resulting in deterioration of characteristics.
Therefore, it has been proposed to use organic materials that do not cause cracks, such as silicone resin, acrylic resin, cyclized polyisoprene, etc., as the insulating layer instead of inorganic materials.
However, the insulating layer made of a thin film of these organic materials does not have sufficient performance as a protective layer and has the disadvantage that the TFT characteristics become unstable.

Furthermore, in the above-mentioned liquid crystal display device, the insulating layer is oriented and also serves as an alignment layer, but when forming a light-shielding layer, alignment treatment must be performed afterward. Depending on the material of the light-shielding layer, the liquid crystal may not be oriented or it may have an orientation that is extremely different from that on the insulating layer, so the alignment of liquid crystals may be disturbed near the light-shielding layer.
This may adversely affect the display.

[Purpose of the present invention] In view of the above-mentioned prior art, the present invention provides a method that allows an insulating layer of TPT to exhibit sufficiently satisfactory performance over a long period of time, and that the alignment of liquid crystals is disturbed even in the vicinity of the light-shielding layer. An object of the present invention is to provide an improved liquid crystal display device that is free from the above problems.

Embodiment of the Present Invention FIG. 3 is a schematic cross-sectional view showing a preferred embodiment of the liquid crystal display device of the present invention.

For example, Si, CdS, CdSe, CdTe, Te"J is used as the semiconductor layers 3 and 3' constituting the TPT, and amorphous, polycrystalline, or fine quality Si is particularly preferably used. Amorphous St may contain an H atom or a halogen atom (particularly an F atom). Each of the H atom and the halogen atom may be contained alone in Qi, or both may be contained.

The content is preferably 0601 to 40 at% in total,
More preferably, it is 0.01 to 30 at%.

In this embodiment, the insulating layer covering the TFT array consists of two layers (ie 6a and 6b).

Reference numeral 6a is an inorganic insulating layer, which can be formed using an inorganic material such as a metal oxide, such as titanium oxide, alumina, or a silicon compound, such as silicon dioxide or silicon nitride, by a layer deposition method, a sputtering method, a CVD method, or the like. The thickness of the inorganic insulating layer should be at least enough to protect the channel portion of the TPT, and preferably 500 to 30 mm.
It is about 00A.

6b is an organic insulating layer. Thermosetting resins, thermoplastic resins, or synthetic resins are preferably used as materials for forming the organic insulating layer, but they can be substantially completely cured, and in that state they are substantially invisible. Any material may be used as long as it is transparent to light and can be subjected to alignment treatment.

Examples of the thermosetting resin include phenol resin, polyester resin, silicone resin, acrylic resin, and urethane resin. A crosslinking agent, a polymerizing agent, a sensitizer, etc. may be added to these thermosetting resins as necessary. Examples of thermoplastic resins include polycarbonate, polyethylene, and polystyrene.

Also in this case, a stabilizer or the like may be added if necessary.
Examples of synthetic rubber resins include cyclized polyisoprene,
Examples include cyclized polybutadiene. Also in this case, a crosslinking agent, sensitizer, etc. may be added as necessary.

The organic insulating layer is made by dissolving a thermosetting resin or a synthetic resin in a solvent and then coating it on the inorganic insulating layer, and applying heat or irradiation with electromagnetic waves such as ultraviolet rays or radiation, either alone or in combination, to form the resin. It is formed by crosslinking, combining, and curing.

When a thermoplastic resin is used, the organic insulating layer is formed by, for example, applying heat to the resin to melt it and applying it to the inorganic insulating layer, followed by cooling and hardening. The thickness of the organic insulating layer is also related to the thickness of the inorganic insulating layer,
Preferably it is 500-3000A. Note that if the sum of the layer thicknesses of the inorganic insulating layer and the organic insulating layer is too large, it may adversely affect the display, so the layer thickness is determined to be an appropriate layer thickness. The heating temperature is preferably 300° C. or lower when amorphous S+ is used for the semiconductor layer constituting the TPT. This is because when the temperature reaches 300° C. or higher, the amorphous Si layer may be thermally affected and the characteristics of the TPT may change or deteriorate.

The light shielding layers 9 and 9' are formed by forming a metal such as At on the organic insulating layer by vapor deposition or the like, and then leaving the metal layer in a desired shape and size by photolithography or the like.

io is an alignment layer, which is formed to cover the organic insulating layer 6b and the light shielding layer 9. Any material for the alignment layer 10 that is normally used in this type of device can be used. For example, CVD of polyparaxylylene
An organic alignment layer is formed by forming a film by a method or applying polyvinyl alcohol using a spinner, and then directly polishing the surface in a certain direction for alignment. Further, an inorganic alignment layer is formed by obliquely depositing an inorganic material.

Examples of the present invention are shown below.

Example 1: Plasma CV was further applied on the surface of the substrate on which the TFT array was formed.
A silicon nitride layer (2000 mm thick) of gold was formed using the D method. Next, on this silicon nitride layer, a cyclized polyisoprene resist (manufactured by Tokyo Ohka Co., Ltd. 0
DUR-110WR: i, acp) was applied with a spinner at 300 rpm, cured for 2 seconds with a high-pressure mercury lamp, and further cured for 15 minutes.
Baking was performed at 0°C for 20 minutes. As a result, approximately 1
A colorless and transparent organic insulating layer having a thickness of gm was formed. Furthermore, metal aluminum was deposited on top of the film and removed by etching except for the required portions to form a light-shielding layer.

On top of that, approximately 2
The film was deposited to a thickness of 0.00 OA, and its surface was subjected to orientation treatment.

Using the thus obtained display substrate, a liquid crystal display device was fabricated through the usual -[process.

Thus? 4) Place the liquid crystal display device in a hot and humid atmosphere (
When the device was continuously operated for 100 hours at 90'C, 190% RH), it exhibited good display characteristics during operation.

Example 2: Plasma CV was further applied on the substrate surface on which the TFT array was formed.
A silicon nitride layer (2000 mm thick) of gold was formed using the D method. Next, a cyclized polyisoprene resist (0D manufactured by Tokyo Ohka Co., Ltd.) dissolved in xylene was applied to this silicon nitride layer.
UR-110WR: 18 c p) was applied with a spinner at 300 rpm, cured for 2 seconds with a high-pressure mercury lamp, and further coated with 15 c p).
Baking was performed at 0'C for 20 minutes. As a result, a colorless and transparent organic insulating layer with a thickness of about 1 pm was formed. Furthermore, metallic aluminum was deposited on top of the layer and removed by etching other than the required portions to form a light-shielding layer.

On top of that, add 3000 ml of 5% aqueous solution of polyvinyl alcohol.
The coating was applied with a spinner at rpm and dried, and the surface thereof was subjected to orientation treatment to form an orientation layer with a thickness of about 2000'A. Using the thus obtained display substrate, a liquid crystal display device was manufactured through normal steps. The thus obtained liquid crystal display device was heated for 10 minutes in a high temperature and humid atmosphere (90°C, 90% RH).
When the device was operated for a continuous period of o hours, it was found that the display had good display characteristics during operation.

[Effects of the present invention] According to the present invention as described above, by further forming an organic insulating layer on the inorganic insulating layer, TPT
In addition, even if cracks occur, which is a drawback of conventional inorganic insulating layers, the presence of the organic insulating layer prevents any negative effects on the device. The occurrence of pinholes can be almost completely prevented, and a liquid crystal display device with stable performance over a long period of time can be provided. Furthermore, according to the present invention, the alignment layer is formed uniformly over the entire surface, covering the light-shielding layer, and the alignment treatment is applied uniformly over the entire surface, including on the light-shielding layer. It is possible to obtain uniform and good display characteristics over the entire surface without causing any distortion.

Further, according to the present invention, the alignment layer also covers the light-shielding layer and is formed with a smooth surface, so that uniform alignment treatment can be easily achieved. Furthermore, by forming an alignment layer over the entire surface of a TPT-formed substrate with many irregularities, the smoothing of the substrate is promoted, and there is also an effect of alleviating the phenomenon that the liquid crystal thickness changes due to irregularities and the alignment is disturbed.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of a conventional liquid crystal display device, and FIG. 3 is a cross-sectional view of a liquid crystal display device according to the present invention. 1: Gate electrode 2: Insulating layer 3: Semiconductor layer 4: Source electrode 5 Ni-drain electrode 6: Insulating layer 6a: Inorganic insulating layer 6b: Organic insulating layer 7: Liquid crystal 8: Transparent electrode 9: Light-shielding layer 10: Alignment layer S2 substrate

Claims (1)

[Claims] (1) In a liquid crystal display device in which a thin film transistor array is disposed on a substrate surface, the thin film transistor array is covered with an inorganic insulating layer, the inorganic insulating layer is covered with an organic insulating layer, and the thin film transistor array is covered with an organic insulating layer. is characterized in that a light shielding layer is formed at a position corresponding to the thin film transistor, and an alignment layer is further formed to cover the organic insulating layer and the light shielding layer. LCD display device.