JPH01306820A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve video characteristics and prolong the life of liquid crystal by connecting a light shield conductor film provided between a scanning signal line or video signal line and the liquid crystal electrically to a common transparent picture element electrode. CONSTITUTION:The light shield conductor films LS2 are provided on the scanning signal line GL and video signal line DL. The light shield conductor film LS2 is constituted to size larger than the width of the scanning signal line GL and video signal line DL, e.g. a mask matching deviation quantity or more. Further, the light shield conductor films LS2 are so constituted not overlapping with the transparent picture element electrode ITO 1 or overlapping with it slightly. Then the light shield conductor films LS2 are connected electrically to the common transparent picture element electrode at the peripheral part (nearby a liquid crystal sealed part) of the liquid crystal display device by interposing a conductive material such as a silver paste material. Consequently, a light leak at the scanning signal line or video signal line part is reduced and the video characteristics and the life of the liquid crystal are improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid crystal display device, and is particularly effective when applied to a liquid crystal display device in which pixels are arranged at the intersection of a scanning signal line and a video signal line. It is related to technology.

[Conventional technology]

The display of each pixel in the liquid crystal display section is performed using thin film transistors (TPT).
) Active matrix type liquid crystal display devices are known. This liquid crystal display device has liquid crystal sealed in a space between a lower transparent glass substrate and an upper transparent glass substrate. A pixel consisting of a transparent pixel electrode and a thin film transistor that controls the voltage applied thereto is provided on the inner surface (liquid crystal side) of the lower transparent glass substrate. A common transparent pixel electrode facing the transparent pixel electrode is provided on the inner surface (liquid crystal side) of the upper transparent glass substrate.

Each pixel is arranged within a region surrounded by two scanning signal lines extending in the column direction and two video signal lines extending in the row direction. The gate electrode of the thin film transistor of each pixel is connected to one of the two scanning signal lines. The drain electrode (or source electrode) of the thin film transistor of each pixel is connected to one of the two video signal lines. Source electrode (or drain electrode) of thin film transistor
is connected to the transparent pixel electrode.

Regarding liquid crystal display devices, for example, Japanese Patent Application No. 1986-1
No. 44913.

[Problem to be solved by the invention]

During the development of a liquid crystal display device, the present inventor discovered that the scanning signal line (in some cases, the video signal line) or its vicinity is illuminated, causing so-called light leakage, which deteriorates image characteristics such as contrast. I found out.

The inventor of the present invention found that, depending on the setting of the potential (common potential) applied to the common transparent pixel electrode, the distance between the common transparent pixel electrode and the scanning signal line is approximately 5. It is considered that the cause is that the liquid crystal (negative type) is driven by the electric field generated between the two electrodes since a DC voltage component of about -20 [V] diameter is added.

Further, the present inventors have discovered a problem in that the direct current voltage component applied between the common transparent pixel electrode and the scanning signal line causes poor alignment, etc., and deteriorates the lifespan of the liquid crystal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a technique capable of improving image characteristics and extending the life of a liquid crystal in a liquid crystal display device.

Another object of the present invention is to provide a technique that can reduce the number of manufacturing steps to achieve the above object.

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 to solve the problem]

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

In a liquid crystal display device, a light-shielding conductor film is provided between a scanning signal line or a video signal line and a liquid crystal, and the light-shielding conductor film and a common transparent pixel electrode are electrically connected.

Further, the light-shielding conductor film is formed in the same manufacturing process as the light-shielding film provided on the channel formation region of the thin film transistor of the pixel.

Further, each of the light-shielding conductor film and the light-shielding film is electrically isolated.

[For production]

According to the above-mentioned means, since light leakage in the scanning signal line or video signal line portion is reduced, the video characteristics can be improved, and the liquid crystal between the scanning signal line or video signal line and the common transparent pixel electrode can be improved. Since the DC voltage component applied to the liquid crystal is reduced, the life of the liquid crystal can be improved.

Furthermore, since the light-shielding conductor film can be formed in the step of forming the light-shielding film, the number of manufacturing steps can be reduced by the amount corresponding to the step of forming the light-shielding conductor film.

Furthermore, since the light shielding film is placed in a floating state to reduce the electric field effect therefrom, the characteristics of the thin film transistor can be improved.

Hereinafter, the configuration of the present invention will be described together with an embodiment in which the present invention is applied to an active matrix color liquid crystal display device.

In addition, in all the figures for explaining the embodiment, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

〔Example〕

Figure 1 shows one pixel of the liquid crystal display section of an active matrix color liquid crystal display device, which is an embodiment of the present invention.
2 (a sectional view taken along the section line ``--'' in FIG. 1).

As shown in FIGS. 1 and 2, the liquid crystal display device has a
It has a pixel composed of a thin film transistor TPT and a transparent pixel electrode ITO1.

The lower transparent glass substrate SUB 1 has a thickness of about 1.1 [mm].

The thin film transistor TPT mainly includes a gate electrode GT, a gate insulating film G1 . It is composed of an i-type semiconductor layer AS, a drain electrode (or source electrode) SDI, and a source electrode (or drain electrode) Sn2.

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

The scanning signal lines OL extend in the column direction in FIG. 1, and a plurality of scanning signal lines OL are arranged at predetermined intervals in the row direction.

The i-type semiconductor layer AS is used as a channel formation region of the thin film transistor TPT. The i-type semiconductor layer As is formed of an amorphous silicon film or a polycrystalline silicon film.

The drain electrode SDI and the source electrode SD2 are each provided on the i-type semiconductor layer AS to be separated from each other. Each of the drain electrode SDI and the source electrode SD2 is configured such that when the bias polarity of the circuit changes, the source and drain are interchanged in operation. Drain electrode S01. Each of the source electrodes SD2 is formed, for example, by sequentially laminating a Cr layer and an AQ layer from the lower layer side in contact with the i-type semiconductor layer AS. The 01 layer is formed as a barrier layer to prevent reaction between the i-type semiconductor layer AS and the AQ layer. The AQ layer is a low resistance material that increases signal transmission speed and is used as a main wiring material.

A transparent pixel electrode ITO1 provided for each pixel is connected to one source electrode SD2 of the thin film transistor TPT. The transparent pixel electrode IT○1 constitutes one of the pixel electrodes of the liquid crystal display section. The other drain electrode SDI is integrated with and connected to a video signal line (vertical signal line) DL. The video signal lines DL extend in the row direction in FIG. 1, and a plurality of video signal lines DL are arranged at predetermined intervals in the column direction.

As shown in Figure 1, one pixel consists of two scanning signal lines G.
It is arranged in an area surrounded by L and two video signal lines DL. The thin film transistor of one pixel arranged in this area is connected to one of the two scanning signal lines GL and 2.
It is connected to each of the video signal lines DL of one of the books.

A protective film PSVI is provided over the thin film transistor TPT and the transparent pixel electrode IT01. Protective film PSV1
is formed mainly to protect the thin film transistor TPT from moisture, etc., and is formed of a silicon oxide film or a silicon nitride film that is highly transparent and has good moisture resistance.

A light shielding film LSI is provided over at least the channel formation region of the thin film transistor TPT, with a protective film PSVI interposed therebetween, so that external light does not enter the i-type semiconductor layer AS used as the channel formation region. Light shielding film L
The SI is formed of a material having light-shielding properties, such as an AQ layer, a Cr layer, or a composite layer thereof.

The liquid crystal LC includes a lower alignment film ORI for setting the orientation of liquid crystal molecules in a space formed between the lower transparent glass substrate 5UBI and the upper transparent glass substrate 5UB2.1. It is defined and sealed in each of the upper alignment films RI2.

The lower alignment film 0RII is formed on the protective film PSVI on the lower transparent glass substrate 1 side. The lower alignment film 0R11 is made of, for example, a photosensitive polyimide resin material.

On the inner surface (liquid crystal side) of the upper transparent glass substrate 5UB2, a color filter FIL, a protective film PSv2, a common transparent pixel electrode ITO2, and the upper alignment film 0RI2 are sequentially laminated.

The common transparent pixel electrode ITO2 is a transparent pixel electrode ITOI provided for each pixel on the lower transparent glass substrate 5UBI side.
It is configured integrally with another common transparent pixel electrode ITO2 that is opposite to and adjacent to the common transparent pixel electrode ITO2. In other words, the common transparent pixel electrode ITO
2 is provided over substantially the entire inner surface of the upper transparent glass substrate 5UB2.

Although the arrangement of the color filter FIL is not shown, it is composed of three color filters: a red filter (R), a green filter (G), and a blue filter (B). Each color filter is arranged at a position opposite to each pixel. The color filter FIL can be formed by, for example, dyeing a film mainly made of acrylic resin for each pixel with a dye.

The protective film PSV2 is provided to prevent the dyes used to dye the color filters FIL into different colors from leaking into the liquid crystal LC. The protective film PSV2 is made of a transparent resin material such as acrylic resin or epoxy resin.

This liquid crystal display device has a lower transparent glass substrate 5UBl side,
Each layer on the upper transparent glass substrate 5UB2 side is formed separately, and then the upper and lower transparent glass substrates 5UBI and 5UB2 are formed separately.
It is assembled by overlapping the two and sealing the liquid crystal LC between them.

Lower transparent glass substrate SUB 1, upper transparent glass substrate 5
A polarizing plate POL is formed on the outer surface of each UB2.

The liquid crystal display device configured in this way is shown in FIGS. 1 and 2.
As shown in the figure, a light shielding conductor film LS2 is provided on each of the scanning signal line OL and the video signal line DL. The light-shielding conductor film LS2 is configured to have a slightly larger size (for example, a size larger than the mask misalignment amount or more) than the respective width dimensions of the scanning signal line OL and the video signal line DL. In addition, the light-shielding conductor film LS2 is made of transparent pixel electrode ITO.
Construct it so that it does not overlap with 1 or so that it has a slight shape.

The light-shielding conductor film LS2 is connected to the scanning signal line GL and the video signal line D.
It is sufficient that the protective film PS■1 and the lower alignment film 0RII are provided between each of L and the liquid crystal LC.
is established between.

The light-shielding conductive film LS2 is made of the same layer (same conductive layer) as the light-shielding film LSI provided on the channel formation region of the thin film transistor TPT, and is formed in the same manufacturing process. That is, the light-shielding conductor film LS2 includes a Cr layer, an AQ
It is made of a material that has a light-shielding property such as a layer and is electrically conductive. This light-shielding conductor film LS2 is electrically isolated from the light-shielding film LSI, and the light-shielding film LSI is configured in an electrically floating state. Although not shown, the light-shielding conductor film LS2 is connected to the common transparent pixel electrode ITO2 in the peripheral area of the liquid crystal display device (near the liquid crystal sealing area) with a conductive material such as a silver paste interposed therebetween. electrically connected. Since a common potential is applied to the common transparent pixel electrode IT○2 as shown in FIG. 3 (driving waveform diagram of the liquid crystal display device), the same potential as the common potential is applied to the light-shielding conductor film LS2. It is configured as follows. As shown in FIG. 3, the common transparent pixel electrode IT02,
Each of the light-shielding conductive films LS2 has a voltage of -10 to -15 [V, for example.
A fixed potential in the range of ] is applied. The scanning signal line OL is
For example, high level is 5[V], low level is -20[V]
] (for example, 1/24 every 63 μS)
A pulse signal of 0 [μs]) is applied. Video signal line D
For example, a video signal having a high level of 1.5 EV] and a low level of -11.5 [V] is applied to L.

In this way, in the liquid crystal display device, the scanning signal lines GL,
By providing a light-shielding conductor film LS2 between each of the video signal lines DL and the liquid crystal LC, and electrically connecting the light-shielding conductor film LS2 and the common transparent pixel electrode ITO2, the scanning signal line GL and the video signal Since each part of the line DL is covered to reduce light leakage, image characteristics such as contrast can be improved, and the scanning signal line GL and the video signal line DL are
Since the potential difference between each portion of the liquid crystal and the common transparent pixel electrode ITO2 is reduced and the DC voltage component applied to the liquid crystal LC is reduced, the life of the liquid crystal LC due to alignment defects etc. can be improved.

Further, the light-shielding conductor film LS2 is a light-shielding film L provided on the channel formation region of the thin film transistor TPT of the pixel.
Since the light shielding conductor film LS2 can be formed in the same manufacturing process as the SI, the light shielding conductor film LS2 can be formed in the process of forming the light shielding film LSI.

The number of manufacturing steps for a liquid crystal display device can be reduced.

Furthermore, by electrically separating each of the light-shielding conductor film LS2 and the light-shielding film LS1, the light-shielding film LSI is placed in a floating state, thereby reducing the electric field effect. Unnecessary channel formation can be prevented and the characteristics of the thin film transistor TPT can be improved.

As above, the invention made by the present inventor has been specifically explained based on the above embodiments. However, 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.

For example, the present invention does not necessarily need to be provided on both the scanning signal line and the video signal line, and may be provided on one of the scanning signal line and the video signal line where the lighting phenomenon occurs.

〔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, it is possible to improve not only the image characteristics but also the life of the liquid crystal.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one pixel of a liquid crystal display section of an active matrix color liquid crystal display device which is an embodiment of the present invention. FIG. FIG. 3 is a diagram of driving waveforms of the liquid crystal display device. In the figure, 5UB1... upper transparent glass substrate, 5UB2...
・・Lower transparent glass substrate, LC・Liquid crystal, TPT・・
・Thin film transistor, ITOI...transparent pixel electrode, ■
TO2...common transparent pixel electrode, GT...gate electrode, OL...scanning signal line, SDI...drain electrode,
SD2...source electrode, DL...video signal line, LS
l: Light-shielding film, LS2: Light-shielding conductor film. \, -knee/ Figure 1 Figure 3

Claims (1)

[Claims] 1. A liquid crystal display in which a plurality of pixels are arranged at the intersection of a scanning signal line and a video signal line, and a common transparent pixel electrode is arranged at a position facing the plurality of pixels with a liquid crystal interposed therebetween. In the device, a light-shielding conductive film electrically separated from the scanning signal line or video signal line is provided between the scanning signal line or video signal line and the liquid crystal, and the light-shielding conductive film and the common transparent pixel are connected to each other. A liquid crystal display device characterized by electrically connecting electrodes. 2. The pixel is composed of a thin film transistor and a transparent pixel electrode, a light shielding film is provided between the channel formation region of the thin film transistor and the liquid crystal, and the light shielding conductor film is the same conductive film as the light shielding film. A liquid crystal display device according to claim 1, characterized in that the liquid crystal display device is comprised of: 3. The liquid crystal display device according to claim 2, wherein each of the light-shielding conductor film and the light-shielding film are electrically isolated.