JP2002122855A - Transmissive liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the quality of transmitted image due to re-reflection in the case where returned light is made incident on a liquid crystal panel in a transmissive liquid crystal display device. SOLUTION: In the transmissive liquid crystal display device consisting of a pair of mutually confronted substrates 10, 14 and a liquid crystal 15 held between the pair of the substrates, on at least one substrate 10, a low reflectance layer 21 such as a polysilicon layer is formed at least just below a metal wiring 12 arranged on the substrate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type liquid crystal display device used for a liquid crystal projector or the like, which prevents deterioration of image quality due to re-reflection of light reflected from an optical system outside the liquid crystal panel on the liquid crystal panel. And a transmission type liquid crystal display device.

[0002]

2. Description of the Related Art As shown in FIG.
The light emitted from the light source 2 is separated into three colors of red (R), green (G), and blue (B) by the dichroic mirror 3, and the light is separated into the transmission type liquid crystal panel 4 for each of the RGB colors. The mainstream is to form a magnified projected image through a projection lens 7 by combining the light with a dichroic prism 6 and color-combining it. In the figure, reference numeral 8 denotes a total reflection mirror, and reference numeral 9 denotes a condenser lens.

FIG. 4 is a schematic plan view of the transmissive liquid crystal panel 4. As shown, the transmissive liquid crystal panel 4 has a central effective pixel area 5A and a peripheral area 5B outside the effective pixel area.
It is divided into and. The pixels are arranged vertically and horizontally in the effective area 5A, the peripheral area 5B is shielded from light, and a drive circuit is arranged.

[0004]

In recent years, light sources have made remarkable progress, and the liquid crystal projector 1 performs display with a large amount of light source. However, the improvement of the anti-reflection technique on the surface of the dichroic prism 6 or the projection lens 7 is not sufficient. Therefore, with an increase in the amount of light from the light source 2,
As shown in FIG. 5, the surface reflection light (hereinafter, referred to as “return light”) at the dichroic prism 6 and the projection lens 7 increases, and the return light re-enters the liquid crystal panel 4, causing some adverse effects. Have been.

[0005] For example, when return light is incident on a pixel transistor such as a TFT of the liquid crystal panel 4, there is a problem that a light leakage current causes a decrease in contrast and a decrease in image quality such as flicker.

Further, when the return light is re-reflected by the metal wiring forming the driving circuit in the peripheral area 5B, the periphery of the projected normal image becomes white or the metal wiring pattern of the driving circuit is projected. And image quality is degraded.

Conventionally, as a method for preventing the occurrence of light leakage current due to return light, as shown in FIG. 6, a TFT substrate (drive substrate) of a liquid crystal panel 4 is provided so as to block the incidence of return light on a pixel transistor. In FIG. 10, a light-shielding metal layer 1 is formed above a pixel transistor (TFT) 11 and a metal wiring 12.
3, the light-shielding metal layer 13 is provided on the opposite substrate 14 as shown in FIG.
A light-shielding metal layer is provided on both the upper side and the lower side of the pixel 1 so as to shield light except for the pixel opening region (see Japanese Patent Application Laid-Open No.
00-131716). 6 and 7 show a TFT substrate 1 on which a TFT having a top gate structure is formed.
The liquid crystal panel 4A, 4B has a liquid crystal 15 sandwiched between the liquid crystal panel 0 and the counter substrate 14, and symbols G, S, and D represent a gate, a source, and a drain, respectively, and a symbol 16
Denotes an active layer made of polysilicon;
Reference numeral 9 denotes an insulating layer, and reference numeral 20 denotes a transparent substrate.

However, even if the light-shielding metal layer 13 is provided, the occurrence of light leakage current can be prevented, but the deterioration of image quality due to the return light being reflected back by the drive circuit in the peripheral area 5B of the liquid crystal panel 4 is prevented. It is not possible. In particular, when the light-shielding metal layer 13 is provided in the peripheral region 5B, there is a problem that the pattern of the metal wiring 12 is projected or the outside of the effective display becomes white due to a difference in reflectance between the metal wiring 12 and the light-shielding metal layer 13. .

[0009] In order to solve such a problem, an object of the present invention is to prevent image quality from being deteriorated due to re-reflection from metal wiring even if return light is incident on a liquid crystal panel.

[0010]

According to the present invention, there is provided a transmissive liquid crystal display comprising a pair of opposed substrates and a liquid crystal sandwiched between the pair of substrates.
Provided is a transmission type liquid crystal display device characterized in that at least one substrate has a low-reflectance layer provided at least immediately below metal wiring provided on the substrate.

The present invention also relates to a method of manufacturing a transmissive liquid crystal display device in which liquid crystal is sandwiched between a TFT substrate and a counter substrate, wherein in the step of forming the TFT substrate, at least metal wiring on the transparent substrate is formed. There is provided a manufacturing method characterized by sequentially laminating a low-reflectance layer and an insulating layer in a region directly below.

The present invention also relates to a method of manufacturing a transmissive liquid crystal display device in which a liquid crystal is sandwiched between a TFT substrate and a counter substrate. In the method of forming a TFT substrate, a gate line is formed by patterning a polysilicon layer. At the same time, there is provided a manufacturing method characterized by forming a low-reflectance layer at least in a region directly below the metal wiring.

According to the present invention, since a low-reflectance layer such as a polysilicon layer is provided at least immediately below the metal wiring in the liquid crystal panel, the amount of return light that is re-reflected by the liquid crystal panel is greatly reduced. be able to. Further, even when the return light passes through the polysilicon layer and is reflected again by the metal wiring layer, the re-reflected light passes through the polysilicon layer twice, so that the return light is significantly attenuated and exits the liquid crystal panel. Therefore, it is possible to prevent the wiring pattern from being recognized in the image formed by the liquid crystal panel.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or equivalent components.

FIG. 1 is a sectional view of an example of a liquid crystal panel used in a transmission type liquid crystal display device of the present invention. The liquid crystal panel 4X has a liquid crystal 15 sandwiched between a TFT substrate 10 and a counter substrate 14, and the TFT substrate 10
6 is similar to the conventional liquid crystal panel shown in FIG. 6 in that a light shielding metal layer 13 is provided above the TFT 11 and the metal wiring 12, but a low reflectance layer 21 and an insulating layer 2 are provided on a transparent substrate 20.
2 are sequentially stacked, and the active layer 16 of the TFT 11 is sequentially stacked thereon.

The low-reflectivity layer 21 has a low reflectance of 0 to 50% and an absorptivity to visible light of 20 to 50%.
It is preferable to use a material having a reflectance as high as about 100%. For example, it is preferable to form a polysilicon layer having a reflectance of about ３ of a metal and an absorptivity of 50%. In addition, as the low reflectance layer 21, a metal having a low reflectance, for example, WS
An i-layer or the like may be formed.

In the present invention, the area where the low-reflectance layer 21 is formed is at least immediately below the metal wiring 12. However, since the reflectance of the light-shielding metal layer 13 may be higher than that of the metal wiring 12, the liquid crystal panel 4X shown in FIG. It is also preferable to form it directly below the light-shielding metal layer 13 as described above. Further, in the peripheral region 5B (see FIG. 4) of the liquid crystal panel, it may be formed on the entire surface of the transparent substrate 20.

The low reflectance layer 21 has a thickness of 10 nm to 10 nm.
It is preferably set to μm.

When this liquid crystal panel 4X is used as a liquid crystal panel of a liquid crystal projector as shown in FIG. 3 and the TFT substrate 10 is set so as to face the projection lens 7, return light from the dichroic prism 6 and the projection lens 7 causes And the amount of light is reduced even if the light is re-reflected by the low reflectance layer 21. Further, when the return light reaches the metal wiring 12 or the light-shielding metal layer 13 and is re-reflected there, the re-reflected light passes through the low-reflectance layer 21 twice before exiting the liquid crystal panel. Is sufficiently reduced. Therefore, according to the liquid crystal panel 4X,
The degradation of image quality due to re-reflection of return light can be significantly suppressed.

The manufacturing method of the liquid crystal panel 4X is as follows.
In the step of forming the TFT substrate 10, before forming the TFT 11 on the transparent substrate 20, the low reflectance layer 2 is formed on at least a region directly below the metal wiring 12 on the transparent substrate 20.
A known method can be followed except that the TFT 1 and the insulating layer 22 are sequentially laminated and then the TFT 11 is formed. For example,
An amorphous silicon film is formed on a glass substrate by CVD, and the amorphous silicon is crystallized by dehydrogenation annealing to form a polysilicon layer as the low reflectance layer 21. In addition, a polysilicon layer may be formed by an LP-CVD method.

An insulating layer 22 is formed on the polysilicon layer.
It is preferable to form SiO ₂ , SiN _x or the like by a CVD method or the like.

The light-shielding metal layer 13 is formed of W, Mo, Pt, Pd, T
a thin film of i, Cr, Al, WSi, etc.
Preferably, it is formed to have a thickness of 0 μm.

FIG. 2 is a sectional view of a liquid crystal panel 4Y of a different mode used in the transmission type liquid crystal display device of the present invention. The liquid crystal panel 4X of FIG. 1 is different from the liquid crystal panel 4X of FIG. However, this low-reflectance layer 21 is formed by forming a gate line G by patterning a polysilicon layer in the step of forming the TFT substrate 10.
In that they are formed simultaneously with the formation of As described above, the low reflectance layer 21 is formed on the TFT substrate 10.
Is preferably formed by patterning the polysilicon layer at the same time as the gate line G because it is not necessary to increase the number of manufacturing steps of the liquid crystal panel.

In addition to the illustrations, the invention may take various forms. For example, the low-reflectance layer 21 is preferably provided on the substrate on which the return light is incident, of the pair of substrates constituting the liquid crystal panel. May be provided in any of the above.

Further, the configuration of the present invention can be applied to either an active matrix type or a passive matrix type.

[0026]

According to the transmission type liquid crystal display device of the present invention,
It is possible to prevent the deterioration of the quality of the transmitted image due to the re-reflection of the return light incident on the liquid crystal panel. Therefore, for example, when the transmission type liquid crystal display device of the present invention is used in a liquid crystal projector, even if the light amount of the light source is greatly increased, the wiring pattern of the peripheral circuit of the liquid crystal panel is not projected, and a good projected image is obtained. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal panel used in a transmission type liquid crystal display device of the present invention.

FIG. 2 is a sectional view of a liquid crystal panel used in the transmission type liquid crystal display device of the present invention.

FIG. 3 is a block diagram of a liquid crystal projector.

FIG. 4 is a schematic plan view of a transmission type liquid crystal panel.

FIG. 5 is an explanatory diagram of a problem of a conventional liquid crystal projector.

FIG. 6 is a cross-sectional view of a conventional liquid crystal panel.

FIG. 7 is a sectional view of a conventional liquid crystal panel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal projector, 2 ... Light source, 3 ... Dichroic mirror, 4 ... Transmissive liquid crystal panel, 4X, 4Y ... Transmissive liquid crystal panel used in the transmissive liquid crystal display of this invention, 5A ... Effective pixel area, 5B ... Surrounding area, 6 ...
Diclock prism, 7: Projection lens, 10: T
FT substrate, 11 ... pixel transistor (or TFT),
12: metal wiring, 13: light shielding metal layer, 14: counter substrate, 15: liquid crystal,

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA34Y FA37Y FB09 FD06 GA02 LA03 2H092 GA05 JA24 KA05 MA07 MA12 MA28 NA02 NA22 PA09 RA05 5C094 AA02 BA03 BA16 BA43 CA19 CA24 DA14 DA15 EA04 EA07 EB02 ED11 HA10

Claims (7)

[Claims] 1. A transmissive liquid crystal display device comprising a pair of opposed substrates and a liquid crystal sandwiched between the pair of substrates,
A transmissive liquid crystal display device, wherein a low-reflectance layer is provided on at least one of the substrates at least immediately below a metal wiring provided on the substrate. 2. The transmission type liquid crystal display device according to claim 1, wherein the low reflectance layer is made of polysilicon. 3. The substrate provided with the low-reflectance layer is TF
3. The transmissive liquid crystal display device according to claim 1, which is a T substrate, wherein a low reflectance layer, an insulating layer, and an active layer of the TFT are sequentially laminated on a transparent substrate in the TFT substrate. 4. A substrate provided with a low-reflectance layer is made of TF
A TFT substrate, wherein the TFT substrate has a low-reflectance layer
2. The transmission type liquid crystal display device according to claim 1, wherein the gate lines of the FT are formed simultaneously by patterning the polysilicon layer. 5. A method for manufacturing a transmission type liquid crystal display device in which liquid crystal is sandwiched between a TFT substrate and a counter substrate, comprising:
In a process for forming a T substrate, a low reflectivity layer and an insulating layer are sequentially laminated at least in a region directly below a metal wiring on a transparent substrate. 6. The method according to claim 5, wherein a polysilicon layer is formed as the low reflectance layer. 7. A method of manufacturing a transmissive liquid crystal display device in which a liquid crystal is sandwiched between a TFT substrate and a counter substrate, comprising:
In the step of forming a T substrate, a low reflectivity layer is formed at least in a region immediately below a metal wiring simultaneously with a gate line by patterning a polysilicon layer.