JPS63221322A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent a thin film transistor from damage due to the presence of spacer members and to improve the yield of a liquid crystal display device by providing the spacer members to an area where the thin film transistors are not present. CONSTITUTION:A transparent electrode 6 connected to a source drain electrode 5B is formed by forming the thin film transistor T on the surface of the inside of a glass substrate 1 having a lower transparent part. Then a protecting film comprising oxidized Si film is formed on the whole surface of said glass substrate 1 so as to cover the transistor T. Further, a shielding film 8 is formed on the upper part of the protecting film 7 corresponding to a channel area of the transistor T. Moreover, a lower orientation film 9 is formed in an effective area except the area for forming a sealing material, and spacer members 10 are dispersed uniformly at the same time. The lower orientation film 9 in an area wherein the transistor T is present is removed by developing the lower orientation film 9 being present in the area contg. the transistor T after exposing it using a photomask 20, and the spacer members 10 in the same area are removed at the same time. The removal of the spacer members 10 is performed particularly exactly by executing plasma etching after performing development.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a technique that is effective when applied to a liquid crystal display device, and particularly to a liquid crystal display device in which the display of each pixel of a liquid crystal display section is controlled by a thin film transistor. be.

[Prior art]

The display of each pixel in the liquid crystal display section is performed using thin film transistors (TPT).
) is known.

This liquid crystal display device is constructed by filling a space between a lower transparent glass substrate and an upper transparent glass substrate with liquid crystal. On the inner surface (liquid crystal side) of the lower transparent glass substrate,
A transparent electrode (pixel electrode) is provided for each pixel, and a thin film transistor is provided for each pixel and controls the voltage applied thereto. A common transparent electrode (common pixel electrode) facing the transparent electrode is provided on the inner surface (liquid crystal side) of the upper transparent glass substrate.

A spacer member is provided between the lower transparent glass substrate and the upper transparent glass substrate, and this spacer member forms a space in which the liquid crystal is enclosed. The spacer member is formed of glass fiber, alumina grains, beads, etc. having a uniform size. The spacer member is configured to define the thickness or gap of the liquid crystal. In other words, the spacer member is provided to properly control the shutter and contrast of the liquid crystal display section. The spacer members are uniformly distributed between the transparent glass substrates.

Regarding liquid crystal display devices, see 1, for example, Nikkei Electronics, September 10, 1984 issue, ρP, 211-2.
40.

[Problem that the invention seeks to solve]

As a result of failure analysis of the liquid crystal display section of the liquid crystal display device described above, the present inventor discovered that the spacer member frequently causes so-called point defects in which pixel portions become defective. The point defects occur frequently in the area where the spacer member is formed in the region where the thin film transistor is present.According to the study conducted by the present inventor, it is believed that the point defects are due to the following causes. The spacer member presses the thin film transistor because the area where the thin film transistor is present has a smaller spatial dimension than the area where the thin film transistor is not present by an amount corresponding to the thickness of the thin film transistor. This causes breakdown of the interlayer insulating film, resulting in a short circuit between the gate electrode and the source or drain electrode of the thin film transistor.

Such point defects in the liquid crystal display portion reduce the yield of the liquid crystal display device.

An object of the present invention is to provide a technique that can improve the yield of liquid crystal display devices.

Another object of the present invention is to provide a liquid crystal display device i.

An object of the present invention is to provide a technique that can prevent destruction of a thin film transistor due to pressure on a spacer member.

Another object of the present invention is to provide a technique that achieves the above object and can reduce the number of manufacturing steps for a liquid crystal display device.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of one typical invention disclosed in this application is as follows.

A liquid crystal display device in which a space for sealing liquid crystal is formed by a spacer member is characterized in that the spacer member is provided in a region where the thin film transistor does not exist.

[Effect]

According to the above-described means, the spacer member does not press the thin film transistor, and the destruction of the thin film transistor can be avoided, so that point defects in the liquid crystal display section can be reduced.

As a result, the yield of liquid crystal display devices can be improved.

The configuration of the present invention will be explained below along with one embodiment.

Note that throughout the description of the embodiments, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

[Embodiments of the invention]

A main part of a liquid crystal display section of a liquid crystal display device according to an embodiment of the present invention is shown in FIG. 1 (a cross-sectional view of the main part).

As shown in FIG.
A thin film transistor T is provided on the inner surface (liquid crystal side) of a lower transparent glass substrate 1 having a thickness of approximately 1.

The thin film transistor T mainly includes a gate electrode 2, an insulating film 3 used as a gate insulating film, an i-type semiconductor layer 4 used as a channel formation region, and a pair of source/drain electrodes 5A and 5B.

For example, in order to prevent disconnection, the gate electrode 2
It is formed from a composite film in which an MO layer is laminated on a Cr layer. The gate electrode 2 is integrated with and connected to a scanning line (horizontal signal line).

The i-type semiconductor layer 4 is formed of an amorphous silicon film or a polycrystalline silicon film.

A pair of source/drain electrodes 5A and 5B are provided on the i-type semiconductor layer 4 and spaced apart from each other.

The source/drain electrodes 5A and 5B are configured so that when the bias polarity of the circuit changes, the source and drain are interchanged in operation. In other words, the thin film transistor T is
Like FET, it is bidirectional.

The source/drain electrodes 5A and sB are arranged in order from the lower layer side in contact with the i-type semiconductor layer 4: an n-type semiconductor layer with a high impurity concentration;
The on'' type semiconductor layer, which is formed by sequentially stacking a Cr layer and an AQ layer, is formed of an amorphous silicon film or a polycrystalline silicon film, and is made of an amorphous silicon film or a polycrystalline silicon film to reduce the contact resistance value with the i-type semiconductor layer 4. The Cr layer is formed as a barrier layer to prevent reaction with the A1 layer.

The A12 layer has a low resistance value to increase signal transmission speed, and is also used as a wiring material.

One source/drain electrode 5B of thin film transistor T
A transparent electrode (pixel electrode; ITO
)6 is connected. The transparent electrode 6 constitutes one of the pixel electrodes of the liquid crystal display section.

The other source/drain electrode 5A is integrated with and connected to a video signal line (vertical signal line).

A protective film 7 is provided on the thin film transistor T and the transparent electrode 6. The protective film 7 is mainly formed to protect the thin film transistor T from moisture and the like, and is formed of a silicon oxide film or a silicon nitride film that is highly transparent and has good moisture resistance.

A shielding film 8 is provided above the protective film 7 on the thin film transistor layer to prevent external light from entering the i-type semiconductor layer 4 used as a channel region. The shielding film 8 is formed of, for example, a Cr layer.

In the film transistor T, when a positive bias is applied to the gate electrode 2, the channel resistance between the source and drain decreases, and when the bias is reduced to zero.

The channel resistance is configured to be large.

That is, the thin film transistor T is configured to control the voltage applied to the transparent electrode 6.

The liquid crystal 11 is defined in a space formed between the lower transparent glass substrate 1 and the upper transparent glass substrate 12 by a lower alignment film 9 that sets the orientation of liquid crystal molecules, an upper alignment film 16, and a spacer member 10. It is enclosed.

The lower alignment film 9 is formed on the protective film 7 on the lower transparent glass substrate 1 side. The lower alignment film 9 is made of, for example, a photosensitive material such as photosensitive polyimide resin.

The spacer member 10 is formed on and covered with the lower alignment film 9. The spacer member 10 is made of, for example, glass fiber, alumina particles, beads (glass particles or resin particles), and has a uniform size. The spacer member 10 is configured to define the thickness of the liquid crystal 11, that is, the gap.

On the inner surface (liquid crystal side) of the upper transparent glass substrate 12,
A color filter 13, a protective film 14, a common transparent electrode (common pixel electrode; ITO) 15, and the upper alignment film 16 are sequentially laminated.

The common transparent electrode 15 faces the transparent electrode 6 provided for each pixel on the lower transparent glass substrate 1 side, and is configured integrally with other adjacent common transparent electrodes 15.

The color filter 13 is formed by dyeing a dyed base material made of a resin material such as acrylic resin with a dye for each pixel. Dyeing is done using photolithography technology.

The protective film 14 is provided to prevent the dyes used to dye the color filters 13 into different colors from leaking into the liquid crystal 11. For example, the protective film 14 may be one.

It is made of transparent resin material such as acrylic resin or epoxy resin.

This liquid crystal display device has a lower transparent glass substrate 1 side.

Each layer on the upper transparent glass substrate 12 side is formed separately,
Thereafter, the upper and lower transparent glass substrates 12 and 1 are placed one on top of the other, and the liquid crystal 11 is sealed between them, thereby assembling the device.

In this way, in the liquid crystal display device in which the spacer member 10 forms a space in which the liquid crystal 11 is enclosed (a space that defines a gap), the spacer member 10 is provided in a region where the thin film transistor T is not present. In other words, the spacer member 10 is located in the region where the thin film transistor T is present, especially in the region where the thin film transistor T is present.
A liquid crystal constructed in this manner, in which the gate electrode Zt is not provided in the white part where the i-type semiconductor layer 4 and the source/drain electrodes 5A and 5B are formed (the region where the gap of the liquid crystal 11 is smaller than other parts). In the display device, since the spacer member 10 does not press the thin film transistor T, the thin film transistor T can be prevented from being destroyed. In other words, the liquid crystal display device can eliminate breakage of the glabellar insulating film 3 of the thin film transistor T and prevent short circuits between the source/drain electrode 5A or 5B and the gate electrode 2. Therefore, since the liquid crystal display device can reduce point defects in the liquid crystal display portion, the yield can be improved.

Note that the central portion of FIG. 1 shows a cross section of one pixel portion. The left side shows a cross section of the left edge portion of the transparent glass substrates 1 and 12 where the lead wiring is present. The right side is
Transparent glass substrate! The right edge portion of 12 and 12 shows a cross section of a portion where no lead wiring is present.

The sealing material 17 shown on the left and right sides of FIG. 1 is configured to seal the liquid crystal 11, and is designed to seal the entire periphery of the transparent glass substrates 1 and 12 except for the liquid crystal sealing opening (not shown). is formed along. The sealing material 17 is made of, for example, epoxy resin.

The transparent electrode 15 on the upper transparent glass substrate 12 side is connected to the lead wiring layer formed on the lower transparent glass substrate 1 side by a silver paste material 18 at at least one place. This lead wiring layer includes the aforementioned gate electrode 2,
It is formed in the same manufacturing process as the source/drain electrodes 5A and 5B.

the alignment film 9.16, the transparent electrode 6, the common transparent electrode 15,
Protective film7. Each layer of the insulating film 3 is formed inside the sealing material 18. The polarizing plate 19 includes a lower transparent glass substrate 1,
They are formed on the outer surface of each of the upper transparent glass substrates 12.

Next, a method for forming the spacer member 10 of the liquid crystal display device will be briefly explained with reference to FIG. 2 (a sectional view of a main part of the liquid crystal display section in a predetermined manufacturing process). In one embodiment of the present invention, an example will be described in which a spacer member 10 is formed on the lower transparent glass substrate 1 side.

First, on the inner surface of the lower transparent glass substrate 1.

A transparent electrode 6 forms a thin film transistor T and is then connected to the source/drain electrode 5B of the thin film transistor T.
form.

Next, a protective film 7 is formed on substantially the entire surface of the lower transparent glass substrate 1 (for example, the entire surface excluding the connection terminal portion of the liquid crystal display section) so as to cover the thin film transistor T. As the protective film 7, for example, a silicon oxide film formed by sputtering (or mask sputtering) is used.

Next, a shielding film 8 is formed on the protective film 7 corresponding to the channel region of the thin film transistor T.

Next, as shown in FIG. 2, the lower alignment film 9 is formed in the effective area excluding the area where the sealing material (17) is formed, and the spacer members 10 are uniformly dispersed. The lower alignment film 9 is
As mentioned above, it is formed from photosensitive polyimide resin. Since the sealing material has low adhesion to the lower alignment film 9 and the hermetic sealing of the liquid crystal 11 may deteriorate, it is preferable that the lower alignment film 9 is not formed in the sealing material forming area.

Next, as shown in FIG. 2, the lower alignment film 9 in the region where the thin film transistor T is present is exposed to light using a photomask 20. After this, since the lower alignment film 9 is formed of a photosensitive material, development is performed to remove the lower alignment film 9 in the region where the thin film transistor T is present.
The spacer member 10 in that area can be removed.

The spacer member 10 can be removed more reliably by further performing plasma etching after development. Note that the photomask 2o used is, for example, one in which a shielding film 20B of Cr or the like is formed on a transparent glass substrate 20A.

By performing each step in this manner, the spacer member 10 in the region where the thin film transistor T is present can be removed. Moreover, the spacer member 10
Since it is formed of a photosensitive material, only one photolithography step is required, and other steps such as the step of forming a photoresist film are not required. That is, the manufacturing process for removing the spacer member 10 in the region where the thin film transistor T is present can be substantially reduced.

Moreover, when the lower alignment film 9 is not formed of a photosensitive material,
The spacer member 10 can be removed by forming a photoresist film, exposing it to light, and then developing it.

Further, the spacer member 10 can be formed on the upper transparent glass substrate 12 side together with the upper alignment film 16, as shown in FIG. 3 (a sectional view of a main part in a predetermined manufacturing process). In particular, the spacer member 10 is placed on the upper transparent glass substrate 12 side.
In the case of forming the spacer member 10, the spacer member 10 can be formed on a flat surface where the thin film transistor T is not present, so that the accuracy of the process of removing the predetermined spacer member 10 can be improved.

Further, when the spacer member 10 is formed on the upper transparent glass substrate 12 side, since the thin film transistor T is not present, the thin film transistor T is not destroyed in the process of coating the upper alignment film 16 and the spacer member 10. Furthermore, when forming the spacer member 10 on the upper transparent glass substrate 12 side, since the thin film transistor T is not present,
When performing a contact exposure process, the thin film transistor T is no longer pressed and destroyed by the photomask. In other words, according to another embodiment of the present invention, the thin film transistor T is not destroyed before the liquid crystal display device is assembled.

Further, the spacer member 10 is arranged on the lower transparent glass substrate 1 side,
It can be formed on each of the upper transparent glass substrate 12 sides.

Furthermore, when removing the lower alignment film 9 in the region where the thin film transistor T is present, light leakage may easily occur in the channel region. The size of the film may be made slightly larger.

Further, in the step of removing the lower alignment film 9 in the region where the thin film transistor T is present (removing the spacer member 1a), the lower alignment film 9 is formed on substantially the entire surface of the lower transparent glass substrate 1 side, and the formation The subsequent step may be performed in the same manufacturing process as the step of removing the lower alignment film 9 in the region where the sealing material 18 is formed. In this case, the step of removing the spacer member 10 in the region where the thin film transistor T is present. This can also be used as the step of removing the lower portion 1!19 of the region where the sealing material 18 is formed, so that the number of manufacturing steps can be reduced.

As above, the invention made by the present inventor has been specifically explained based on the above embodiments, but the present invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist thereof. Of course.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

In a liquid crystal display device, destruction of thin film transistors caused by a spacer member can be prevented and the yield thereof can be improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a liquid crystal display section of a liquid crystal display device according to an embodiment of the present invention; FIG. 2 is a cross-sectional view of a main part of the liquid crystal display section in a predetermined manufacturing process; FIG. 3 is a cross-sectional view of a main part in a predetermined manufacturing process of a liquid crystal display device according to another embodiment of the present invention. In the figure, 1.12...transparent glass substrate, 9,15...
Alignment film, 10... Spacer member, 11... Liquid crystal, T
. . . thin film transistor, 20 . . . photomask. ,,＜′)

Claims (1)

[Claims] 1. In a liquid crystal display device in which a space is formed between a lower transparent glass substrate on which a thin film transistor is formed and an upper transparent glass substrate, a space is formed by interposing a spacer member, and a liquid crystal is sealed in this space. . A liquid crystal display device, wherein the spacer member is provided in a region where the thin film transistor does not exist. 2. The liquid crystal display device according to claim 1, wherein the spacer member is formed on the lower transparent glass substrate side, the upper transparent glass substrate side, or each. 3. The spacer member is formed covered with an alignment film that controls the orientation of liquid crystal molecules of the liquid crystal, and the spacer member in the region where the thin film transistor is present is removed at the same time as the alignment film is removed. A liquid crystal display device according to claim 1 or 2, characterized in that: 4. The liquid crystal display device according to claim 3, wherein the alignment film is formed of a photosensitive material. 5. Removal of the alignment film in the area where the thin film transistor is present is performed in the same process as removal of the alignment film in the sealing material forming area provided around the edges of the lower transparent glass substrate and the upper transparent glass substrate. A liquid crystal display device according to claim 3 or 4.