JPH0513287B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] A liquid crystal display device of the present invention, particularly a thin film transistor (TFT) for performing switching for each pixel.
The present invention relates to a liquid crystal display device having an array.

[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 with these 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 solidly formed on the surface of the other substrate. In recent years, on the surface of the substrate on the pixel electrode side, a switch for switching for each pixel has been installed.
Attachment of a TFT 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, the first
In the device shown in the figure, light shielding layers 9 and 9' are further formed on the insulating and alignment layer 6 covering the TFT array 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 the TFT, the film needs to be thicker than a certain level, and these thin films of inorganic materials have the disadvantage that the thicker the film, the greater the film distortion and the tendency for cracks to occur. When such a crack occurs, the TFT is also destroyed at the same time.
The TFT is not protected, leading to deterioration of its 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, and in this alignment treatment, Depending on the material of the light-shielding layer, the alignment may not be applied or the alignment state may be extremely different from that on the insulating layer, so that the alignment of liquid crystals may be disturbed in the vicinity of the light-shielding layer, which may adversely affect the display.

[Object of the present invention] In view of the above-mentioned prior art, the present invention provides a TFT
An object of the present invention is to provide an improved liquid crystal display device in which the insulating layer of the invention can exhibit sufficiently satisfactory performance over a long period of time, and the alignment of the liquid crystal is not disturbed even in the vicinity of the light-shielding layer. .

[Summary of the present invention] The present invention provides: a thin film transistor array substrate including a semiconductor layer and a metal light shielding layer that blocks incident light from entering the semiconductor layer; a counter substrate disposed opposite to the thin film transistor array substrate; In a liquid crystal device having a liquid crystal disposed between two substrates, a first coating formed of an inorganic insulating material is provided on the semiconductor layer and covers the semiconductor layer in direct contact with the semiconductor layer, and a first coating is provided on the first coating. , a second coating formed of an organic insulating material covering the first coating is provided;
The liquid crystal device is characterized in that the metal light-shielding layer is provided on the coating, and an alignment layer is further provided to cover the second coating and the metal light-shielding layer.

[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, etc. are used as the semiconductor layers 3 and 3' constituting the TFT, and amorphous or polycrystalline Si is particularly preferably used. Amorphous Si contains H atoms or halogen atoms (especially F
atoms). Each of the H atom and the halogen atom may be contained alone or both may be contained. Its content is preferably 0.01 total
~40 at%, more preferably 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 vapor deposition method, a sputtering method, a CVD method, or the like. The thickness of the inorganic insulating layer is preferably at least enough to protect the channel portion of the TFT, and is preferably about 500 to 3000 Å.

6b is an organic insulating layer. Thermosetting resins, thermoplastic resins, or synthetic rubber-based 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 transparent to visible light. Any material may be used as long as it is transparent and can be subjected to alignment treatment. Examples of the thermosetting resin include phenolic resin, polyester resin, silicone resin, acrylic resin, and urethane resin. These thermosetting resins contain crosslinking agents, polymerization agents,
A sensitizer or the like may be added. 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 formed by dissolving a thermosetting resin or a synthetic rubber resin in a solvent and then coating it on the inorganic insulating layer, and applying heat or irradiation of electromagnetic waves such as ultraviolet rays or radiation to the resin either alone or in combination. It is formed by crosslinking, polymerizing, and curing. When a thermoplastic resin is used, the organic insulating layer is formed by applying heat to the resin, melting the resin, coating the resin on the inorganic insulating layer, and then cooling and hardening the resin. The thickness of the organic insulating layer is related to the thickness of the inorganic insulating layer, but is preferably 500 to 3000 Å. 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 Si is used for the semiconductor layer constituting the TFT. This means that at temperatures above 300°C, amorphous Si
This is because the characteristics of the TFT may change or deteriorate due to thermal effects on the layer.

The light shielding layers 9 and 9' are formed by forming a metal such as Al 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.

Reference numeral 10 denotes an alignment layer, which is formed to cover the organic insulating layer 6b and the light shielding layer 9. The material for the alignment layer 10 can be any of those normally used in this type of device. For example, an organic alignment layer is formed by forming a film of polyparaxylylene by a CVD method or by coating polyvinyl alcohol with 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: A silicon nitride layer (2000 Å thick) was further deposited on the surface of the substrate on which the TFT array was formed using the plasma CVD method.
was formed. Next, a cyclized polyisoprene resist (ODUR-11OWR: 18cp manufactured by Tokyo Ohka Co., Ltd.) dissolved in xylene was applied on this silicon nitride layer.
The coating was applied using a spinner at 3000 rpm, cured for 2 seconds using a high-pressure mercury lamp, and then baked at 150°C for 20 minutes.
As a result, a colorless and transparent organic insulating layer with a thickness of approximately 1 μm 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. Polyparaxylylene was deposited on it to a thickness of about 2000 Å by low-pressure CVD, and the surface was subjected to orientation treatment. Using the thus obtained display substrate, a liquid crystal display device was manufactured through normal steps.

When the thus obtained liquid crystal display device was operated continuously for 1000 hours in a high temperature and humid atmosphere (90° C., 90% RH), it exhibited good display characteristics during operation.

Example 2 A silicon nitride layer (2000 Å thick) was further formed using plasma CVD on the surface of the substrate on which the TFT array was formed.
was formed. Next, a cyclized polyisoprene resist (ODUR-11OWR: 18cp manufactured by Tokyo Ohka Co., Ltd.) dissolved in xylene was applied on this silicon nitride layer.
The coating was applied with a spinner at 3000 rpm, cured for 2 seconds using a high-pressure mercury lamp, and then baked at 150°C for 20 minutes.
As a result, a colorless and transparent organic insulating layer with a thickness of approximately 1 μm 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. A 5% aqueous solution of polyvinyl alcohol was applied thereon using a spinner at 3000 rpm, dried, and the surface was subjected to orientation treatment to form an orientation layer with a thickness of about 2000 Å. Using the display substrate thus obtained, a liquid crystal display device was manufactured through normal steps. When the thus obtained liquid crystal display device was operated continuously for 1000 hours in a high temperature and humid atmosphere (90° C., 90% RH), it exhibited 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, the inorganic insulating layer protects the TFT and stabilizes the characteristics, and Even if clutching occurs, which is a drawback of conventional inorganic insulating layers, the presence of an organic insulating layer prevents any negative effects on the device and almost completely prevents the occurrence of pinholes. A liquid crystal display device having stable performance over time is 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, so that disturbances in liquid crystal alignment can be prevented even near 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, since the alignment layer is formed to have a smooth surface by covering the light-shielding layer, a uniform alignment process can be easily achieved. Furthermore, by forming an alignment layer over the entire surface of a TFT-forming substrate with many irregularities, the smoothing of the substrate is promoted, and there is also the effect of alleviating the phenomenon in which the liquid crystal thickness changes due to irregularities and the alignment is disturbed.

[Brief explanation of drawings]

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... 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, S...Substrate.

Claims (1)

[Scope of Claims] 1. A thin film transistor array substrate including a semiconductor layer and a metal light shielding layer that blocks incident light from entering the semiconductor layer, a counter substrate disposed opposite to the thin film transistor array substrate, and between the pair of substrates. In a liquid crystal device having a liquid crystal disposed in a liquid crystal device, a first coating formed of an inorganic insulating material is provided on the semiconductor layer and covers the semiconductor layer in direct contact with the semiconductor layer, and the first coating is provided on the first coating. A second film made of an organic insulating material is provided to cover the first film.
A liquid crystal device comprising: the metal light-shielding layer provided on the second film; and an alignment layer covering the second film and the metal light-shielding layer. 2. The liquid crystal device according to claim 1, wherein the semiconductor layer is a layer formed of amorphous silicon. 3. The liquid crystal device according to claim 1, wherein the semiconductor layer is a layer formed of polycrystalline silicon.