JPS5842448B2 - lcd display panel - Google Patents

Description

[Detailed description of the invention] The present invention relates to a liquid crystal display panel.

Furthermore, the present invention relates to the surface shape and surface treatment of a semiconductor substrate used as one substrate constituting a display cell.

Recently, the progress of display devices has been remarkable.

Among them, display devices using liquid crystals have many advantages such as low voltage drive, low power consumption, thinness, and long life, and are used today as display devices for various devices including wristwatches and calculators.

On the other hand, the above-mentioned advantages of liquid crystal display devices are being utilized for applications such as character displays and televisions.

When the number of rows and columns of a matrix display increases in this way, it is effective to use a conductor substrate as one of the substrates that make up the display cell, and to statically drive the liquid crystal using active elements placed on the substrate. be.

The present invention relates to this static drive type liquid crystal display device.

A conventional liquid crystal display panel is shown in FIG.

FIG. 1 shows a structural diagram of a conventional liquid crystal display panel, and numeral 1 in the figure is a semiconductor substrate containing active elements or passive elements.

Liquid crystal drive electrodes 2 are arranged in a matrix on the surface of the semiconductor substrate.

5 is a spacer, and a transparent conductive film 4 is formed on the upper glass plate 3.

6 is a liquid crystal. FIG. 2 is a cross-sectional view of the semiconductor substrate.

The area surrounded by the two-dot chain line in FIG. 2 corresponds to one pixel.

Each pixel contains one transistor and one capacitor.

In the figure, 7 is, for example, an n-type silicon substrate, 8 is a p-type diffusion layer, and 9 is an n-type diffusion layer.

10 is a field oxide film, 11 is a SiO2 film, and 12 is a doped polysilicon film.

13 is a CvD SiO2 film, and 14 is an aluminum film for forming electrodes and wiring.

15 is a protective film, which is usually a CvDSiO2 film.

Section A in FIG. 2 is a part of a transistor, and section B is a part of a capacitor.

As is clear from FIG. 2, when a semiconductor substrate is manufactured by a normal process, a step difference of about 1 to 3 microns occurs on the surface of the semiconductor substrate.

This varies somewhat depending on the shape of the element incorporated into the semiconductor substrate and the manufacturing process, but generally the surface has large irregularities.

Therefore, if a semiconductor substrate with a highly uneven appearance as shown in FIG. 2 is used and the surface is subjected to orientation treatment by tilted vapor deposition of SiO, etc., an SiO film will be formed as shown in FIG. 3. There are surfaces where the SiO film is formed and surfaces where the SiO film is not formed.

In FIG. 3, 16 is a semiconductor substrate with an uneven surface, 17 is a
The evaporation direction 18 of SiO particles, which are deposited obliquely at an angle θ=70 to 89°, is a SiO film formed on a semiconductor substrate.

As is clear from the figure (the more severe the irregularities on the surface of the semiconductor substrate 16, the smaller the proportion of the surface on which the SiO film is formed).

As shown in FIG. 3, if the proportion of the surface on which the SiO film for alignment is not formed is large, this portion does not contribute to actual display, so the contrast is significantly reduced and the function as a display device is degraded.

The present invention eliminates the drawbacks of the conventional liquid crystal display panel, and its purpose will be explained below with reference to specific examples.

Generally, the surfaces of two substrates constituting a liquid crystal display panel require horizontal or vertical alignment treatment depending on the display method and type of liquid crystal.

There are various methods for orientation treatment.

Examples include a rubbing method, an inclined vapor deposition method, and a dipping method using a silane coupling agent.

However, from the viewpoint of uniformity of properties and quality, the tilted deposition method is the best.

In the tilted evaporation method, SiO or Teflon is deposited in vacuum at an angle of 70° to 89° to the substrate, creating countless long thin lines on the substrate surface at intervals of hundreds to thousands of angstroms. This is used to form and orient liquid crystals.

In the case of tilted deposition on a glass substrate, as shown in Figure 4,
Since the surface of the glass plate 190 is flat, the tilted vapor deposition film 20 adheres to the entire surface.

- When using an old-fashioned conductor board, the semiconductor substrate has a surface level difference of 1.0μ or more, as described above.
．． When there is a step of 0 μm, if deposition is performed at an angle of 80° on the surface, no obliquely deposited film will be formed in a region of 5.8 μm on one side of the step.

The present invention was invented to solve this problem, and provides a display panel with high contrast and easy viewing.

Specifically, the feature is that when the surface of the semiconductor substrate is flattened in the area contributing to the display and tilted vapor deposition is performed, the proportion of the area to which the tilted vapor deposition film does not adhere is reduced due to the step difference.

FIG. 5 is a cross-sectional structural diagram of a semiconductor substrate in which the surface level difference is reduced.

The numbers 7 to 14 in FIG. 5 correspond to the numbers in FIG. 2.

Reference numeral 21 in FIG. 5 is a layer for flattening the surface of the semiconductor substrate, which is the key point of the present invention.

Further, a transparent conductive film layer or a metal layer 22 is formed on the layer 21 as a liquid crystal drive electrode.

This liquid crystal drive electrode is connected to the lower wiring 14 by a through hole.
is connected to.

The layer 21 for flattening the surface of the semiconductor substrate is preferably made of polyimide resin, low melting point glass, or other insulating material.

In the case of polyimide resin, a polyimide film having a thickness of about 1 to 5 μm is formed on the surface of the semiconductor substrate by applying polyimide varnish and a spinner.

In this case, in order to improve the adhesion between the base and the polyimide film, a silane coupling agent may be applied to the base semiconductor substrate in advance.

Thereafter, it is cured at a temperature of 350 to 550°C.

Through-holes may be photo-etched using hydrazine solution or NaOH'#.

After that, liquid crystal driving electrodes may be formed.

Polyimide is used as a planarizing material for semiconductor substrates because it has the highest heat resistance among organic resins, can be formed to a film thickness of about 10 μm without cracking, and has excellent passivation effects. is very useful.

However, the present invention is not limited to polyimide coatings, and may be low melting point glasses, such as lead glass containing PbO2 as a main component, or zinc glass containing Zn02 as a main component.

Furthermore, phosphorus glass containing p2o as a main component may also be used.

Regardless of the material used, the present invention will be satisfied if the level difference on the surface of the semiconductor substrate after formation is 0.5 μm or less.

If an alignment film is formed by tilted vapor deposition on the flattened semiconductor surface formed by the above method, almost all areas of the display area will be covered, as shown in 20 in FIG. 5 or 20 in FIG. Since the alignment process can be performed, the contrast of the liquid crystal display panel can be greatly improved, and a display panel that is easy to see can be made possible.

In FIG. 6, 23 is a semiconductor substrate whose surface is flattened, and 24 is a liquid crystal drive electrode.

By using the flattened semiconductor substrate according to the present invention, the contrast of the liquid crystal display panel has been improved several times compared to the conventional one.

Although the present invention has mainly been described as a semiconductor substrate including a MOS type transistor, the present invention is not limited to this, and may be a substrate including a TPT (thin film transistor), and may also be applied to an SO8 substrate. Needless to say, it will happen.

Furthermore, it goes without saying that the semiconductor substrate may include only efficient elements or only passive elements.

When the liquid crystal display cell of the present invention is applied to a liquid crystal display television, it provides high contrast and is very effective.

The liquid crystal in this case may be a twisted nematic liquid crystal with a low driving voltage, or may be a liquid crystal obtained by mixing a nematic liquid crystal with a dichroic dye.

In any case, by using a semiconductor substrate with a flat surface, the thickness of the liquid crystal can be made uniform, and the contrast can be improved.

As described above, the present invention relates to a liquid crystal display panel characterized in that the surface of a semiconductor substrate used as one substrate of the display panel is flattened in order to improve the contrast of the liquid crystal display panel. This is something that can be expected to improve significantly.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the cross-sectional structure of a liquid crystal display cell. FIG. 2 is a cross-sectional structural diagram showing the surface unevenness of a conventional semiconductor substrate. FIG. 3 is a diagram showing an alignment process for a substrate with severe surface irregularities. FIG. 4 is a diagram showing the alignment treatment on glass with a flat surface. FIG. 5 is a cross-sectional structure showing a semiconductor substrate with a flattened surface according to the present invention. FIG. 6 is a diagram showing an orientation treatment for a substrate with a flattened surface according to the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Liquid crystal drive electrode, 3... Upper glass plate, 4... Transparent conductive film, 5... Spacer, 6...Liquid crystal, γ...n-type silicon substrate, 8...p
Green type diffusion layer, 9...n Green type diffusion layer, 10...
... Field oxide film, 11 ... Gate oxide film, 12 ... Doped polysilicon film, 13.
...CVDSiO2 film, 14...2nd layer wiring, 15...CVDSiO2 film, 16...
...Semiconductor substrate with severe unevenness, 17...Tilted vapor deposition direction, 18...Tilted vapor deposited film, 19...
...Glass plate, 20...Tilted vapor deposition film, 21...
...Layer for flattening the semiconductor surface, 22...
Liquid crystal drive electrode, 23...Semiconductor substrate with a flattened surface, 24...Liquid crystal drive electrode.

Claims (1)

[Claims] 1. In a liquid crystal display panel using a semiconductor substrate in which a plurality of active elements and passive elements are arranged in a matrix on one substrate constituting a display cell, the semiconductor substrate is subjected to surface flattening treatment. A crystal panel characterized in that an electrode film is formed in a matrix on the surface of the semiconductor substrate corresponding to the active element and the passive element, and the surface of the semiconductor substrate is covered with an alignment film. 2. The surface planarization treatment of the semiconductor substrate surface is performed by coating a varnish-like insulating material with a film thickness of 1 to 5 μm on the highly uneven semiconductor substrate, as claimed in claim 1. The liquid crystal display panel described. 3. The liquid crystal display panel according to claim 1, wherein the alignment treatment film on the surface of the semiconductor substrate is a tilted evaporation film of SiO. 4. The liquid crystal display panel according to claim 1, wherein the liquid crystal in the liquid crystal display panel has a twisted nematic structure. 5. Claim 1, wherein the liquid crystal in the liquid crystal display panel is composed of a pleochroic dye and a nematic liquid crystal.
Liquid crystal display panel described in section.