JP2895699B2 - Active matrix display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix display device used for a projection type image display device for enlarging and projecting an image on a screen.

[0002]

2. Description of the Related Art In the above active matrix display element, picture element electrodes are generally arranged in a matrix on one of two opposing substrates to form a display unit called a picture element. Independent drive voltages are applied to these picture element electrodes via switching elements such as thin film transistors (hereinafter referred to as TFTs). When a driving voltage is applied to the picture element electrode, the optical characteristics of a display medium such as a liquid crystal sealed between the picture element electrode and the counter electrode provided on the other substrate change, and the display by the picture element is performed. I do. Then, images, characters, and the like are displayed by a plurality of picture elements.

In the TFT of the active matrix display element, a semiconductor layer such as amorphous silicon or polycrystalline silicon is formed. These semiconductor layers have a problem in that carriers are generally excited by light, and the off characteristic as a switching element is deteriorated. In order to solve this, an active matrix display element using a TFT as a switching element is provided with a light shielding film.

Conventionally, in an active matrix display element used for a direct-view display device such as a personal computer, a word processor, and a pocket television, Cr, Cr is used so that light reflected by a light shielding film does not lower display contrast. The light-shielding film is formed using a material having a low reflectance, such as Mo or Ta.

[0005]

However, in a projection type image display apparatus, which has attracted attention in recent years and enlarges and projects an image on a screen, intense light is irradiated from the side on which a light-shielding film is formed in order to increase luminance. When a light-shielding film is formed using a material having a low reflectance as described above, the light-shielding film absorbs light and increases the temperature of the display element, causing a display failure or reducing the reliability of the display device. There is a risk of doing so.

For this reason, Japanese Patent Application Laid-Open No. Sho 1-202430 proposes that a light-shielding film is formed using Al in order to increase the light reflectance and prevent the temperature of the display element from rising. . However, Al thin films are easily damaged by chemicals, and pinholes are easily generated by thermal atom transfer. Therefore, a sufficient non-defective product rate cannot be obtained in mass production. In addition, since the light-shielding film has a high reflectance even on the optical display medium side, light scattering occurs and TFT characteristics deteriorate, and scattered light causes a decrease in contrast, resulting in a problem that image quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to increase the luminance of a display screen by using strong irradiation light, prevent image quality from deteriorating, and manufacture at a high yield rate. It is an object of the present invention to provide an active matrix display element capable of performing the above-mentioned operations.

[0008]

An active matrix display element according to the present invention is formed by forming a pair of transparent insulating substrates opposed to each other with an optical display medium interposed therebetween and forming a matrix on one of the pair of substrates. An active matrix display element having a picture element electrode and a switching element connected to the picture element electrode, wherein the optical display medium of the one of the pair of substrates on which the picture element electrode is not formed On the side, a light-shielding film having an opening is formed so that the opening faces the picture element electrode, and substantially the entire surface of the light-shielding film has a high reflectance of A.
a first layer made of an alloy of l and a high melting point metal, and a second layer made of a material having a low reflectivity, wherein the second layer is disposed on the optical display medium side; Thereby, the above object is achieved.

[0009]

In the active matrix display element according to the present invention, the light-shielding film is formed with the opening thereof facing the pixel electrode, and has a two-layer structure. Since the first layer made of an alloy of high reflectivity Al and a high melting point metal is formed on the substrate side, the light reflectivity is high, the temperature rise of the substrate can be reduced, and chemicals and heat can be prevented. Is also stable. Also,
Since the second layer made of a material having a low reflectance is formed on almost the entire surface of the first layer on the optical display medium side, light scattering in the display element hardly occurs, and light irradiation to the TFT and scattered light are prevented. Can be prevented from lowering the contrast.

[0010]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view of an active matrix display element of the present invention, and FIG. 2 is an enlarged view of FIG.

The active matrix display element (hereinafter referred to as display element) 10 has a pair of transparent insulating substrates 1 and 5. As the transparent insulating substrates 1 and 5, a glass substrate is used. On one substrate 1,
The picture element electrodes 4 are formed in a matrix, and the TFT 2 is connected to each picture element electrode 4 as a switching element.
Further, between each pixel electrode 4, a gate bus line 3 and a source bus line 9 are provided so as to be orthogonal to each other.

On the other substrate 5, a light-shielding film 6 is formed so as to cover the periphery of the picture element electrode 4 and a portion other than the picture element electrode 4. The light shielding film 6 is made of an alloy of Al and a high melting point metal,
For example, it has a two-layer structure of a first layer 6a made of an alloy of Al98% -Ta2% (hereinafter referred to as Al-Ta) and a second layer 6b made of a material having a low reflectance, for example, Mo.
The light-shielding film 6 can be formed, for example, by continuously forming an Al-Ta thin film and a Mo thin film by a thin film forming technique such as a sputtering method, and providing openings in these thin films by a photolithography technique. .

An ITO (Indium-T) film is formed on the entire surface of the substrate 5 by sputtering so as to cover the light shielding film 6.
There is provided a counter electrode 7 made of in-oxide and an alignment film 8 which has been rubbed by baking a polyimide resin.

A liquid crystal layer (not shown) is sealed between the substrate 1 and the substrate 5 to form a display element 10.
In the present embodiment, the size of the display screen of the display element 10 is 75 mm diagonal and 190 μm × pixel pitch.
The width of the light-shielding film 6 was set to 88 μm × 104 μm and the aperture ratio was 30%. The display is performed in the twisted nematic mode. In the present embodiment, since the first layer 6a is provided,
On the display element surface, the visible light reflectance is about 80%.
Since the second layer 6b is provided, the visible light reflectance in the display element is about 60%. C used conventionally
The visible light reflectance of the light-shielding film made of r is about 60%, the light absorption of the light-shielding film is reduced to about half on the display element surface to which strong irradiation light is applied, and the scattered light is reduced within the display element by the conventional light-shielding property. It can be comparable to a membrane. In addition, the Al—Ta thin film has less damage to chemicals and the generation of pinholes due to thermal atom transfer than the Al thin film, and can provide a satisfactory non-defective product when mass-produced.

In the above embodiment, the first layer is made of Al 98%
Although -Ta 2% was used, a material other than Ta may be used as the refractory metal, and the composition is not limited to this. Also,
Although Mo was used for the second layer, any material having a low reflectance can be used.

FIG. 3 is a schematic diagram of a projection type image display device using the active matrix display element of the present embodiment. In this apparatus, a light source 11 having a parabolic reflector 12 is provided.
And a dichroic mirror for three-primary-color separation (hereinafter, referred to as a separation mirror) 14 in front of the light source 11.
R and 14B, a display element 10G and a mirror 15M are provided. A mirror 14M, a display element 10R, and a dichroic mirror for combining three primary colors (hereinafter, referred to as a combining mirror) 15B are shifted slightly from the front of the light source 11.
15G, a projection lens 16 and a screen 17 are provided. Disassembly mirror 14B and synthesis mirror 15B
The display element 10B is provided between the two. Condenser lenses 13R, 13G, and 13B are provided on the light incident side of each of the display elements 10R, 10G, and 10B. Here, the display elements 10R, 10G, 10B, the projection lens 1
The reason why the screen 6 and the screen 17 are arranged obliquely with respect to the optical axis is to irradiate light from the optimum visual direction in the twisted nematic mode and to eliminate trapezoidal distortion of the projection screen.

The white light emitted from the light source 11 is reflected directly or by the parabolic reflecting mirror 12, and travels to the decomposing mirrors 14R and 14B and the mirror 15M. Only the red (R) component light is reflected by the decomposition mirror 14R. The reflected light of the R component is reflected by the reflection mirror 14M, and the condenser lens 13R and the display element 1
Head to 0R. The display element 10R controls the transmission of the R component light and gives image information to the R component light. Display element 10R
The R component light transmitted through the mirrors 15A and 15B
G is transmitted and is displayed on the screen 17 by the projection lens 16.

On the other hand, of the green (G) component light and the blue (B) component light transmitted through the decomposing mirror 14R, the B component light is reflected by the decomposing mirror 14B,
3B and the display element 10B. Display element 10B
Controls the transmission of the B component light and gives image information to the B component light. The light of the B component transmitted through the display element 10B is reflected by the combining mirror 15B, is combined with the light of the R component transmitted through the display element 10R, passes through the combining mirror 15G, and is projected onto the screen 17 by the projection lens 16. Is displayed.

The G component light transmitted through the decomposing mirror 14B is transmitted to the condenser lens 13G and the display element 10B.
Reach G. The display element 10G controls transmission of G component light and gives image information to the G component light. Display element 10
The G component light transmitted through G is reflected by the combining mirror 15G, combined with the R component light and the B component light from the combining mirror 15B, and displayed on the screen 17 by the projection lens 16.

When the surface temperature of the display elements 10R, 10B, and 10G was measured in the projection type image display apparatus having the above-described structure, the temperature was about 40 ° C., and the display temperature was about 40 ° C. In comparison, the temperature rise was significantly reduced. In addition, good image quality was obtained without a decrease in contrast due to light scattering in the display element.

In the above embodiment, the light-shielding film is provided so as to cover the peripheral portion of the pixel electrode and the portion other than the pixel electrode. You may make it cover only a part.

[0023]

As is apparent from the above description, in the present invention, the light-shielding film has a two-layer structure, and the light-shielding film is made of Al on the substrate side.
Since the first layer made of an alloy of a metal and a high melting point metal is provided, an increase in temperature can be prevented, and an active matrix display element excellent in mass productivity can be obtained. In addition, since the second layer made of a material having a low reflectance is provided on the optical display medium side, it is possible to prevent deterioration in image quality due to light scattering. Therefore, it is possible to mass-produce a high-brightness and high-quality projection image display device at a high yield rate and to supply it at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an active matrix display element according to one embodiment of the present invention.

FIG. 2 is an enlarged view of FIG.

FIG. 3 is a schematic diagram of a projection type image display device using the active matrix display element of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 5 Transparent insulating substrate 2 TFT 3 Gate bus wiring 4 Picture element electrode 6 Shielding film 6a First layer 6b Second layer 7 Counter electrode 9 Source bus wiring 10R, 10G, 10B Active matrix display element 11 Light source 12 Paraboloid Reflector 13 Condenser lens 14R, 14B Dichroic mirror for three primary color separation 14M, 15M mirror 15B, 15G Dichroic mirror for three primary color synthesis 16 Projection lens 17 Screen

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Iida 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Miwa Kuroda 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56) References JP-A-5-11241 (JP, A) JP-A-3-269415 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/136 G02F 1 / 1343 G02F 1/1335 G09F 9/30

Claims (1)

(57) [Claims] 1. A pair of transparent insulating substrates disposed to face each other with an optical display medium interposed therebetween, a pixel electrode formed in a matrix on one of the pair of substrates, and connected to the pixel electrode. A switching element, and an active matrix display element comprising: a light-shielding film having an opening on the optical display medium side of a substrate on which a pixel electrode is not formed, of the pair of substrates;
The opening is formed so as to face the pixel electrode, and substantially the entire surface of the light-shielding film is made of a first layer made of an alloy of high-reflectivity Al and a high-melting-point metal, and a low-reflectance material. An active matrix display element having a two-layer structure with a second layer, wherein the second layer is disposed on the optical display medium side.