JPS595228A - Image display device - Google Patents

Abstract

PURPOSE:To prevent the incidence of light to a semiconductor device and to enable the uniform display of an image without unevenness, by providing an opaque conductive layer which shields the light made incident to the semiconductor layer. CONSTITUTION:The incidence of incident light 15 or 15' to a semiconductor layer 7 is prevented in the case of using an image display as a transmission type or reflection type in the image display device using a liquid crystal 6 to be driven by plural thin film transistors and switching elements formed on a transparent insulation substrate 10, wherein an opaque conductive film 12 of a metallic film or the like is formed in a stripe shape on the transistors through an insulation film 13 and is disposed in parallel with a gate electrode 1 in order to shield the incident light 15. The light 15 is reflected by the film 12 or metallic films 2, 3 for source-drain electrodes, so that the incidence thereof to the layer 7 is prevented. The width of the layer 7 and the thickness of a gate insulation film 8 are required to be taken into consideration with respect to the width of the electrode 1 for shielding the incident light 15'.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to shielding light incident on TPTs (Thin Film Transistors) in a matrix array in which a plurality of TPT (Thin Film Transistor) switching elements are arranged on a transparent insulating substrate.

The configuration of an image display device that drives a liquid crystal is to arrange multiple rows of gate electrode groups in the horizontal direction (1-2), and to arrange multiple rows of gate electrode groups (1-2) in the vertical direction perpendicular to the gate electrode groups (1-2).
The structure of one pixel consists of a TFT section, a liquid crystal driving electrode section, and a part of a capacitor.

An image is displayed by applying electro-optical modulation to the liquid crystal by applying a video signal and a gate signal to necessary pixels. The driven liquid crystal accumulates charge by its own capacitance component. L7 Kashi, (1)
The resistance component of the liquid crystal leaks charge, (2) TP
Due to leakage current flowing through the semiconductor layer at the time of T OF)i', unevenness occurs in image display. As a countermeasure against these problems, by connecting a charge storage capacitor in parallel to the liquid crystal, it becomes possible to lengthen the drive retention time of the liquid crystal by the charge accumulated in the capacitor.

By the way, as a semiconductor film that constitutes TPT.

Cd5e (cadmium selenide), amorphous silicon, and polycrystalline silicon, which have light-sensitive conductivity.

When single-crystal silicon or the like is used, leakage current increases when the TPT is turned off due to light incident on the semiconductor layer.

As a result, there is no significant adverse effect on the image display device, such as display unevenness in images.

[7 Therefore, in order to display images uniformly and evenly,
It is necessary to prevent light from entering the semiconductor layer and to minimize leakage current when the TPT is turned off. The present invention has been made for the purpose of almost completely shielding a semiconductor layer from incident light. In order to clearly explain the present invention, a conventional method will be described. FIG. 1 shows an equivalent circuit of the conventional method, and FIGS. 2 and 5 are cross-sectional views thereof.

In the drawings following Figure 1, (1) is a gate line, (2) is a signal line, (3) is a drain electrode of TF'I', (4) is a TPT, (5) is a charge storage capacitor, (6) is a liquid crystal layer, (7) is a semiconductor layer, (8) is a 5i
Gate insulating film such as Oz, Si3 N4, (9) is a transparent substrate such as glass or plastic on the front side, (II is an insulating substrate such as glass, plastic, ceramics, etc. on the back side, 01
) is a transparent conductive film such as In2O3, 5n02,
, Cr, Mo, Ni, etc. metal film or 7〈 is an opaque conductive film such as a conductive organic thin film, 01 is 5i02, Si3N
4, an i-edge film made of polyimide or the like, 04 is a conductive film for a capacitor, α mark indicates incident light from the front side, and (1s') indicates incident light from the back side.

In the present invention, this opaque conductive film B is a highly reflective metal film as in the previous example, a highly reflective film deposited on a transparent conductive film such as It1203.5r102, and a highly adhesive light-shielding film. It is a conductive film with high light-shielding properties that has high reflectivity or high light-absorptive properties, such as a two-layered film, a colored conductive organic thin film, etc., and among them, a metal film is easy to form and has a high light-shielding property. So nice.

The conductive film for the capacitor is a transparent conductive film when the device of the present invention is used as a transmission type, but it may be transparent or opaque when used as a reflection type.

As for the transparent substrate and the insulating substrate, the ones mentioned above can be used, and if necessary, the surface is coated with 5IO2, Δt203, Zr.
Forming a layer of insulating material such as 0z1. Used to throat.
For the liquid crystal layer, various mixtures of nematic liquid crystals can be used, including dynamic scattering mode, twisted nematic mode, phase transition mode, and dichroic dyes may be added to create guest host mode. A more complex display can also be achieved by forming two layers on the liquid crystal f4.

If these image display devices are of a transmission type, and the semiconductor layer (7) is of a transmissive type, then the light incident on the semiconductor layer (7) from the direction of the opposing glass substrate (9) that holds the liquid crystal layer (6) between them is zero. Transparent insulating substrate (10 transmitted through 1., -C incident light (15')
Used as a reflective type (if the incident light is 0)
υ exists 1.

[Therefore, the detailed description of the present invention will be made in the case where the image display device is a transmissive type or a reflective type e). In this case, countermeasures against incident light 0υ or incident light (15') will be described.

FIG. 4 is an equivalent circuit diagram of one pixel according to the present invention.

A plan view is shown in Fig. 5, a sectional view taken along line A-A' in Fig. 5 is shown in Fig. 6, and an enlarged view of the part surrounded by a circle in Fig. 6 is shown in Fig. 7. As shown in the figure.

According to this device, in order to block the incident light α→, an opaque conductive film such as a metal film (1) is formed in a stripe shape on the transistor via an insulating film α], and It is arranged parallel to the gate electrode.The material of the opaque conductive film is as described above (At, Cr, M, etc.).

It is sufficient that the film has a high light-shielding property such as a film having a film thickness of several hundred holes to several thousand holes. Incident light (at 1:0, it is reflected by the opaque conductive film 0) or the metal for the drain electrode (2), (3), and is almost completely prevented from entering the semiconductor layer (7). The effect can be improved by making the width of the twisted opaque conductive film α equal to or slightly wider than the width of the gate electrode (1).
,big.

Next, regarding shading of incident light (15'), it is necessary to consider the width of the semiconductor layer (7) and the thickness of the gate insulating film (8) with respect to the width of the gate electrode (1). be.

It is preferable that the width of the semiconductor layer (7) and the gate electrode (1) be the same, or that the semiconductor layer (7) be slightly larger in terms of high-resolution image display performance. This is because - the area ratio of the gate electrode in the pixel can be reduced. However, (2) in these cases, no light shielding effect of the gate electrode (1) can be expected at all with respect to the incident light (15').

As clearly seen in the partially enlarged view of FIG. 7, the present invention has been developed by making the width of the gate electrode (1) slightly thicker than the width of the semiconductor layer (7) in order to block the incident light (1s'). The light-shielding effect of the gate electrode is utilized by the gate electrode.The gate is composed of an opaque conductive material such as A, T, Cr, Ni, Mo, etc.-h, and its film thickness is several It is from a hundred λ to several thousand X.

The light shielding effect by the gate electrode is caused by the distance between the semiconductor layer (7) and the gate electrode (1) as shown in the partially enlarged view of FIG.
Regarding the relationship between X and the film thickness Y of the gate insulating film (8), when X=Y, the leakage current when the TFT is turned off is improved by about one order of magnitude. In the case of ~ direction X: Y: 5: 1, this light shielding effect is even more remarkable than when
The leakage current when it is OFF is almost 7 (increased by 1.7).

For these reasons, it is preferable to set the value of y/x to 1 or less [2, especially if the value is about 002 or more, the value of y/x is preferably 1 or less,
') has a great effect of shielding the semiconductor layer (7) from light. Alternatively, if the width of the semiconductor layer is a≦b-1DC, sufficient light shielding can be achieved. Of course, only the left side of the gate electrode in the 9th frame 1+ in FIG. 6 is enlarged in FIG. 7, but the right side of the gate electrode also has the same shape as the 71st C1. Now, in general, 'J
'FT is formed with the structure of IGFET (insulated cathedral field effect transistor). For this reason, failures due to dielectric breakdown of the base insulating film due to static or atmospheric conditions are likely to occur. Especially in image display devices, I (3fi'ET type T)
When a plurality of PTs are arranged on a substrate, in order to display an image, defects caused by electrostatic breakdown of the gate insulating film of the TPT increase point defects or line defects within the image display area.d) Image Display performance is significantly deteriorated.

At the same time, breakdown of the feed line film due to static electricity also occurs at a portion of the so-called crossover between the gate lines and gate lines that are perpendicular to each other. During the trial production of the TPT matrix array, it is necessary to take great care when arranging the substrate (7). Met.

The present invention is also a countermeasure against static electricity, and there is a characteristic in the arrangement of the metal film 11'J, which is a light-shielding film, as described above (Q).

In the apparatus according to the present invention, a plan view of the substrate σ) end is shown in FIG. 8, and FIG.
'Cross-sectional structure between 1. 1. Opaque conductive side film (11 layers in one pixel, formed in a stripe shape). In addition, an opaque conductive film (1) is an insulating film α as shown in FIGS.
] or the gate electrode (
1) Pull it out upwards. By forming the terminal portion of the image display device in this structure, it becomes possible to arbitrarily short-circuit between the gate electrode, the opaque conductive film as the light-shielding film 7, and the ground electrode. Short circuit method and 1. conductive tape.

The roughness may be a conducting wire of 0η or the like.

During nodding of the substrate, or during alignment processing (rahing) of the liquid crystal C=), [7] By shorting the gate electrode, the opaque conductive side, and the north between the electrodes, keeping it at ground potential, or any potential. Static electricity damage can be prevented. For example, the gate insulating film (8) is sandwiched between the gate electrode (1) and the north electrode (2) that covers the semiconductor layer (7). Due to Rahing, the opaque conductive film α2. Alternatively, even if static electricity is generated in the polymer OQ, which is the light distribution processing layer, if the opaque conductive film α→, the north electrode (2), and the gate electrode (1) are short-circuited to the outside, they all have the same potential. Then,
Therefore, electrostatic breakdown of the gate insulating film sandwiched between them can be prevented.

The orthogonal chain portion (crossover part) between the gate electrode (1) and the north electrode (2) has a similar effect.

Although the explanation is omitted in the text, in other embodiments, (1) the thickness of the insulating film α1 is approximately the same as the thickness of the gate insulating film (8). It is possible to use carriers in the upper and lower portions of the TPT semiconductor layer (7) as a double gate structure. (Ii) On the other hand, if the insulating film (1→) is made sufficiently thicker than the gate insulating film (8), a normal single gate structure can be obtained.

Further, the structure of the terminal portion of the opaque conductive film which is the light shielding film according to the present invention may be short-circuited when forming the opaque conductive film Q2 as shown in FIG.

As explained above, the image display device formed according to the present invention has the effect of blocking incident light, and also has the function of preventing dielectric breakdown due to static electricity.1. This method is effective in achieving a high-quality one-image display device.

[Brief explanation of the drawing]

FIG. 1 is an equivalent circuit diagram of a conventional image display device. FIG. 2 is a cross-sectional structural diagram of a conventional image display device. FIG. 3 is a cross-sectional structural diagram of a conventional image display device. FIG. 4 is an equivalent circuit diagram of an image display device using the present invention. FIG. 5 is a plan view of an image display device using the present invention. FIG. 6 is a cross-sectional structural diagram of an image display device using the present invention. FIG. 7 is an enlarged cross-sectional structural view of the circled portion in FIG. 6. FIG. 8 is a plan view of a terminal portion of an image display device using the present invention, and FIG. 9 is a cross-sectional structural diagram of the image display device using the present invention. FIG. 10 is a cross-sectional structural diagram of an image display device using the present invention. 1. Kate line 2, signal line 3, drain electrode 4, TFT (thin film transistor) 5, charge storage capacitor 6, liquid crystal layer 7, semiconductor layer 8, gate insulating film 9, transparent substrate 10, insulating substrate 11, transparent conductive film 12, Opaque conductive film 13, Insulating film 14, Conductive film for capacitor 15, Incident light 15c, Incident light 16, Alignment treatment film (polymer) 17, Conductive tape or conductive wire 8413 710 reviews for F8 Kawasaki 2. ] - Full sale - H mouth j JE "Sales: July 27, 1982 Name of image display device 3, relationship with the person making the amendment Patent applicant address 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name (
004) Asahi Glass stock ratio 4, agent voluntary amendment 6, number of inventions increased by amendment None 7, Ura iE
fshio J elephant 8, hiil: Contents (1) Specification page 4, line 1 “Signal line J [source 1
Correct to No. 4 line J. (2) On page 1, line 18 of the specification, "metal film" is corrected to "metal film." (3) Correct page 4, line 20 of the specification [Signal U・RnJ] to [Source signal line]. (7I) Figure 6 is corrected as shown in the attached sheet. More than 7.5'

Claims (3)

[Claims] (1) An image display device using a liquid crystal driven by a plurality of thin film transistor switching elements formed on a transparent insulating substrate, characterized by comprising an opaque conductive film that blocks light incident on the semiconductor layer. Display device. (2) In the structure of a thin film transistor, the width of the semiconductor layer is made narrower than the width of the gate electrode, thereby blocking light incident from the direction of the gate electrode. image display device. (3) The light-shielding film disposed on the thin film transistor is drawn out in a stripe shape to the edge of the substrate, and is formed as an extraction electrode, and is also connected to the gate electrode through the insulating film.
An image display device according to claim 1 or 2, characterized in that the image display device has a structure arranged in a heel.