JPH05241183A - Liquid crystal display body - Google Patents

Abstract

PURPOSE:To provide a liq. crystal display body not causing whitening, uneven display, etc., and ensuring high display grade. CONSTITUTION:A liq. crystal layer is held between upper and lower substrates 2, 1 with separate electrodes on the insides and the sealing parts of the substrates 2, 1 are made electric conductive. A metal pad 3 for electric conduction having >=2/3 of the sealing length is fitted to the sealing part of at least the substrate 1 and electric conductive spacers 5 and electric nonconductive spacers 4 are all owed to exist only between the sealing parts.

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, and more particularly to a substrate facing an electrode having electrodes on the inner side of a liquid crystal layer, and a conductive portion for connecting an electrode on one substrate to an electrode on the other substrate. The present invention relates to a liquid crystal display body.

[0002]

2. Description of the Related Art Generally, a liquid crystal display has an electrode on its inner surface and a liquid crystal layer provided between two opposing substrates. However, when the electrodes are connected to an external circuit, the electrodes are removed from each of the two substrates. It is easier to provide a conductive part inside the liquid crystal body and connect one substrate to the other electrode, and to connect only one substrate to an external circuit than to draw out.

As such means, JP-A-59-28186
In the publication, a conductive spacer having a diameter equal to that of a spacer for maintaining a cell gap is mixed with a sealing agent to achieve conduction between the upper and lower substrates, and the cell gap is determined except for the conductive portion.
That is, it is disclosed that the non-conductive spacer dispersed in the display portion is used.

However, as the pixel density becomes higher, that is, the pixel area becomes narrower due to the demand for high-quality images in recent years, in the above-mentioned conventional method, the spacers dispersed in the display portion disturb the alignment of the liquid crystal, resulting in white blank. Occurs, and the display quality is degraded. Furthermore, even if a conductive spacer is mixed with the sealant, there are only two electrode pads for external circuit connection, so if the resistance of the transparent electrode is high, the distance between the electrode pad and each pixel can be reduced. There was also a problem in that the resistance was different due to the difference and uneven display occurred.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems of the prior art and to provide a liquid crystal display having a high display quality in which white spots and display unevenness do not occur.

[0006]

That is, according to the present invention, there are provided substrates which face each other with electrodes on the inner surface sandwiching a liquid crystal layer, and conductive portions for connecting electrodes on one substrate to electrodes on the other substrate. In the liquid crystal display having the above, the seal portion is a conductive portion, a metal conduction pad having a seal length of ⅔ or more is provided at a seal corresponding portion of at least one substrate, and the conductive spacer and the non-conductive portion are provided only in the seal portion. A liquid crystal display characterized by the presence of a polar spacer.

For the liquid crystal display of the present invention, a semiconductor substrate having a single crystal Si layer manufactured by the following method can be used in addition to the substrate which is usually used. Then, the liquid crystal element, the liquid crystal drive circuit, and other peripheral drive circuits can be simultaneously formed on the same substrate. The method will be described below. (Hereinafter, referred to as “method for producing semiconductor substrate using porous Si”.) The single crystal Si layer of the semiconductor substrate is formed by using a porous Si substrate obtained by making the single crystal Si substrate porous.

According to observation with a transmission electron microscope, pores having an average diameter of about 600 Å are formed in this porous Si substrate, and the density thereof is less than half that of single crystal Si. Nevertheless, its single crystallinity is maintained, and it is possible to epitaxially grow a single crystal Si layer on top of the porous layer. However, at 1000 ° C. or higher, rearrangement of internal holes occurs and the characteristics of enhanced etching are impaired. Therefore, for the epitaxial growth of the Si layer, the molecular beam epitaxial growth method, plasma CV
Low temperature growth such as D method, thermal CVD method, photo CVD method, bias sputtering method, liquid crystal growth method, etc. is suitable.

Here, a method of epitaxially growing a single crystal layer after making P-type Si porous will be described.

First, a Si single crystal substrate is prepared, and H
It is made porous by the anodization method using the F solution. The density of single crystal Si is 2.33 g / cm ³ , but the density of the porous Si substrate changes to 0.6 to 1.1 g / cm ³ by changing the HF solution concentration to 20 to 50% by weight. Can be made. This porous layer is P because of the following reasons.
It is easily formed on the mold Si substrate.

Porous Si was discovered in the research process of electrolytic polishing of semiconductors, and Si in anodization is used.
In the dissolution reaction of 1), holes are required for the anodic reaction of Si in the HF solution, and the reaction is shown as follows.

Si + 2HF + (2-n) e ⁺ → SiF ₂ + 2H ⁺ + n
e ⁻ SiF ₂ + 2HF → SiF ₄ + H ₂ SiF ₄ + 2HF → H ₂ SiF ₆ or Si + 4HF + (4-λ) e ⁺ → SiF ₄ + 4H ⁺ + λ
e ⁻ SiF ₄ + 2HF → H ₂ SiF ₆ Here, e ⁺ and e ⁻ represent a hole and an electron, respectively. Further, n and λ are the numbers of holes necessary for dissolving Si1 atoms, respectively, and porous Si is formed when the condition of n> 2 or λ> 4 is satisfied.

From the above, P-type Si in which holes are present
Can easily be said to be porous.

On the other hand, it has been reported that high-concentration N-type Si can also be made porous, so that it can be made porous regardless of whether it is P-type or N-type.

Further, since the porous layer has a large amount of voids formed therein, the density is reduced to less than half. As a result, the surface area increases dramatically compared to the volume,
Its chemical etching rate is significantly increased as compared with the etching rate of a normal single crystal layer.

The conditions for making single crystal Si porous by anodization are shown below. The starting material of porous Si formed by anodization is not limited to single crystal Si, and Si having another crystal structure may be used.

Applied voltage: 2.6 (V) Current density: 30 (mA · cm ^-2 ) Anodizing solution: HF: H ₂ O: C ₂ H ₅ OH = 1:
1: 1 time: 2.4 (hour) Thickness of porous Si: 300 (μm) Porosity: 56 (%) Single crystal Si thin film prepared by epitaxially growing Si on the porous Si substrate thus formed. To form.
The thickness of the single crystal Si thin film is preferably 50 μm or less, more preferably 20 μm or less.

Next, after the surface of the single crystal Si thin film is oxidized, a substrate that will eventually form a substrate is prepared,
The oxide film on the surface of the single crystal Si and the above substrate are bonded together. Alternatively, after the surface of a newly prepared single crystal Si substrate is oxidized, it is attached to the single crystal Si layer on the porous Si substrate. The reason for providing this oxide film between the substrate and the single crystal Si layer is that, for example, when glass is used as the substrate, the interface level generated by the underlying interface of the Si active layer is higher than that of the glass interface. This is because the level can be lowered and the characteristics of the electronic device can be significantly improved. Furthermore, only the single crystal Si thin film from which the porous Si gas has been removed by etching by selective etching described below may be attached to a new substrate. The bonding is such that the surfaces are sufficiently adhered so that they cannot be easily peeled off by Van der Waals force only by bringing them into contact with each other at room temperature, but this is further 200 to 900 ° C, preferably 600 to 900 ° C. Heat treatment under a nitrogen atmosphere at the temperature of and bond them completely.

Further, a Si ₃ N ₄ layer is deposited as an etching prevention film on the whole of the above-mentioned two bonded substrates, and only the Si ₃ N ₄ layer on the surface of the porous Si substrate is removed.
Apiezon wax may be used instead of the Si ₃ N ₄ layer. Then, the porous Si substrate is entirely removed by a method such as etching to obtain a semiconductor substrate having a thin film single crystal Si layer.

A selective etching method for electroless wet etching only this porous Si substrate will be described.

As an etching solution which does not have an etching action on crystalline Si and can selectively etch only porous Si, a buffered material such as hydrofluoric acid, ammonium fluoride (NH ₄ F) or hydrogen fluoride (HF) is used. Hydrofluoric acid, mixed solution of hydrofluoric acid or buffered hydrofluoric acid with hydrogen peroxide solution, hydrofluoric acid with alcohol or buffered hydrofluoric acid, hydrofluoric acid with hydrogen peroxide solution and alcohol or buffer A mixed solution of dehydrofluoric acid is preferably used. Etching is performed by moistening the substrate bonded to these solutions. The etching rate depends on the solution concentration and temperature of hydrofluoric acid, buffered hydrofluoric acid, and hydrogen peroxide solution. By adding hydrogen peroxide solution, the oxidation of Si can be accelerated and the reaction rate can be increased as compared with that without addition. By further changing the ratio of hydrogen peroxide solution, the reaction rate can be increased. Can be controlled. Further, by adding alcohol, it is possible to instantaneously remove the bubbles of the reaction product gas due to etching from the etching surface without stirring, and it is possible to uniformly and efficiently etch the porous Si.

The HF concentration in the buffered hydrofluoric acid is set in the range of preferably 1 to 95% by weight, more preferably 1 to 85% by weight, further preferably 1 to 70% by weight, based on the etching solution. The NH ₄ F concentration in the buffered hydrofluoric acid is set in the range of preferably 1 to 95% by weight, more preferably 5 to 90% by weight, further preferably 5 to 80% by weight, based on the etching solution.

The HF concentration is preferably set in the range of 1 to 95% by weight, more preferably 5 to 90% by weight, further preferably 5 to 80% by weight, based on the etching solution.

The H ₂ O ₂ concentration depends on the etching solution.
It is preferably 1 to 95% by weight, more preferably 5 to 90% by weight, still more preferably 10 to 80% by weight, and is set within a range in which the effect of the hydrogen peroxide solution is exhibited.

The alcohol concentration is preferably 80% by weight, more preferably 60% by weight, based on the etching solution.
Hereafter, it is more preferably set to 40% by weight or less and within the range in which the effect of the alcohol is exhibited.

The temperature is preferably set in the range of 0 to 100 ° C, more preferably 5 to 80 ° C, further preferably 5 to 60 ° C.

As the alcohol used in this step, in addition to ethyl alcohol, isopropyl alcohol or the like which can be practically used in the manufacturing process and which is desired to have the above-mentioned alcohol addition effect can be used.

In the semiconductor substrate thus obtained, a single crystal Si layer equivalent to that of an ordinary Si wafer is flatly and uniformly thinned to have a large area over the entire substrate.

The single crystal Si layer of this semiconductor substrate is separated by a partial oxidation method or etched into an island shape, and is doped with impurities to form a p- or n-channel transistor.

[0030]

The present invention will be described in detail below with reference to examples.

(Embodiment 1) FIG. 1 is a sectional view of a liquid crystal display of this embodiment, and FIG. 2 is a top view of a lower substrate.

S on which electrodes for driving the liquid crystal are formed
After the orientation process is performed on the TFT substrate (hereinafter referred to as “lower substrate”) made of i-wafer and the color filter substrate (hereinafter referred to as “upper substrate”) made of low thermal expansion low alkali glass, the thickness of the liquid crystal layer is adjusted. A sealing agent 6 in which non-conductive spacers 4 and conductive spacers 5 having almost the same diameter are mixed is formed on the lower substrate by screen printing in a predetermined pattern, and the upper and lower substrates are bonded to each other and pressure-heat-cured to perform cell assembly. It was After that, the surface of the upper substrate opposite to the surface on which the TFT is formed is covered with a hydrofluoric acid-resistant rubber except under the liquid crystal pixel portion, and a mixed solution of hydrofluoric acid, acetic acid, and nitric acid is used to remove Si up to the insulating layer. The wafer was partially removed, and a transmissive liquid crystal image display device by light transmission was completed.

Neither non-conductive spacers nor conductive spacers are dispersed in the pixel portion 8. The cell gap is determined by the non-conductive spacer 4. A metal conductive connection pad 3 made of AL is provided on the seal portion of the lower substrate 1 except for the electrode pad 9. Therefore, conduction between the upper and lower substrates is achieved by the common transparent electrode 7 / conductive spacer 5 / metal conductive connection pad 3.

Since there is no spacer in the pixel portion 8,
No white spots due to disordered alignment of the liquid crystal were generated, and good display quality was obtained. Further, since the upper and lower connection pads 3 are provided at ⅔ or more of the seal length, it is possible to uniformly connect to the lower electrode from the periphery of the display area of the upper substrate, so that the connection reliability is improved. Furthermore, the resistance of the portion (common transparent electrode 7) corresponding to each pixel on the upper substrate is evenly connected from the periphery of the display area, so that variations are reduced and display unevenness does not occur.

The TFT substrate made of the above Si wafer was manufactured by the above-described method for manufacturing a semiconductor substrate using porous Si.

The upper substrate 2 was manufactured by the following method.

As a black matrix on a low thermal expansion low alkali glass substrate, a chromium dioxide film was first formed by a sputtering method, and a predetermined pattern was photoetched. Next, red, blue, and green filters were formed by a pigment dispersion method, a topcoat layer was provided, and then an ITO layer was further formed by a sputtering method to complete.

Example 2 A liquid crystal display was produced in the same manner as in Example 1 except that the metal layer 10 made of Cr was laminated also on the upper substrate 2 at the seal portion as shown in FIG.

Since the connecting portions of the upper and lower substrates are the metal layer 10 / conductive spacer 5 / metal conductive connecting pad 3, the connection reliability is further improved and the display quality is high as compared with the case where the transparent electrode is used. An image was obtained.

(Example 3) Polycrystalline silicon was formed on quartz glass as an upper substrate (TFT substrate), and a field effect transistor was formed on the polycrystalline silicon thin film and connected to form a complementary element and its integration. A circuit was prepared, and a pixel switching element and a drive circuit necessary for a liquid crystal image display device were formed.

Further, as a black substrate on a quartz glass substrate as a lower substrate, a chromium dioxide film was first formed by a sputtering method, and a predetermined pattern was photoetched. Next, red, blue, and green filters were formed by a dyeing method, a topcoat layer was provided, and then an ITO layer was further formed by a sputtering method to complete.

A conductive spacer 5 is formed by using the upper and lower substrates.
A liquid crystal display was produced in the same manner as in Example 1 except that the diameter of the non-conductive spacer 4 was increased by 3%.

Since the diameter of the conductive spacers 5 is large, the deformation of the conductive spacers 5 is larger than that of the non-conductive spacers 4 when the cell gap is created by applying pressure when the cells are assembled, and the space between the upper and lower substrates is increased. The connection is better.

In this embodiment, the difference in diameter between the conductive spacer 5 and the non-conductive spacer 4 is set to 3%, but it may be 5% or less.

Example 4 A liquid crystal display was produced in the same manner as in Example 1 except that a hard silica spacer was used as the non-conductive spacer and a soft plastic spacer was used as the conductive spacer, and the spacer diameter was changed. ..

The diameter of the non-conductive spacer was selected so that a predetermined cell gap was obtained, and the diameter of the conductive spacer was 3% larger than the diameter of the non-conductive spacer. When a cell gap is created by applying pressure during cell assembly, the non-conductive spacer has a large diameter and is more soft, so that the deformation is large and the electrical connection between the upper and lower portions is good. Moreover, the cell gap was accurately formed by the non-conductive spacer.

In this embodiment, the difference in diameter between the conductive spacer 5 and the non-conductive spacer 4 is set to 3%, but it may be 5% or less.

[0048]

As described above, according to the present invention, since there is no spacer in the pixel portion, white spots do not occur.
In addition, by providing the upper and lower connection pads for ⅔ or more of the seal length, it is possible to connect to the lower electrode uniformly from the periphery of the display area, which improves the connection reliability and lowers the resistance of the upper electrode (common transparent electrode). It can be realized and display unevenness does not occur. Further, since the non-conductive spacer is cheaper than the conductive spacer, a liquid crystal display having high display quality can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display body of the present invention.

FIG. 2 is a schematic top view of a lower substrate of a liquid crystal display body of the present invention.

FIG. 3 is a sectional view of a liquid crystal display body of the present invention.

Claims (1)

[Claims] 1. A liquid crystal display body having substrates facing each other with electrodes on the inner surface sandwiching a liquid crystal layer, and conductive parts for connecting electrodes on one substrate to electrodes on the other substrate. As a conductive portion, at least one of the seal portions of the substrate is provided with a metal conduction pad having a seal length of 2/3 or more,
A liquid crystal display characterized in that a conductive spacer and a non-conductive spacer are present only in the seal portion.