JP2756206B2 - Reflective liquid crystal display device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device which performs display by reflecting incident light and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, applications of liquid crystal display devices to word processors, laptop personal computers, pocket televisions, and the like have been rapidly advancing. In particular, among the liquid crystal display devices, a reflection type liquid crystal display device that performs display by reflecting light incident from the outside is notable because a backlight is not required, so that power consumption is low, and it is possible to obtain a thin and lightweight structure. I have.

Conventionally, a reflection type liquid crystal display device has a TN
(Twisted nematic) method and STN (super twisted nematic) method are used. However, in these methods, a half of the light intensity of natural light is inevitably used for display by a polarizing plate. There is a problem of darkening.

To solve this problem, there has been proposed a display mode in which natural light is effectively used without using a polarizing plate. An example of such a mode is a phase change type guest-host system. (DL White and and
G. FIG. N. Taylor: J. Appl. Phys. 4
54718 1974). In this mode, a cholesteric-nematic phase transition phenomenon caused by an electric field is used. A reflection type multi-color display in which a micro color filter is further combined with this method has been proposed (Proceedings of the display).
SID Vol. 29157 1988). In order to obtain a brighter display in a mode that does not require such a polarizing plate, it is necessary to increase the intensity of light scattered in a direction perpendicular to the display screen with respect to incident light from a wide angle.
For that purpose, it is necessary to create a reflector having optimal reflection characteristics. According to the above-mentioned document, the surface of a substrate made of glass or the like is roughened with an abrasive, and the time of etching with hydrofluoric acid is changed to control the surface unevenness, and a silver reflective film is formed on the unevenness. The formed reflector is described.

[0005] However, the reflector described in the above document has an uneven portion formed by damaging the glass substrate with an abrasive, so that it is impossible to form an uneven portion having a uniform shape. Further, there is a problem that the reproducibility of the shape of the uneven portion is poor. Therefore, it is not possible to obtain a reflection type liquid crystal display device having a uniform shape and a reflection plate having good reflection characteristics with good reproducibility.

As a method for solving this problem, a film is formed, a plurality of fine irregularities having a predetermined shape are formed on the substrate surface by etching, and a reflective film such as silver is formed thereon. There has been proposed a method of forming a reflection plate. 5 and 6 show the structure of an active matrix type reflection type liquid crystal display device having such a structure of the reflection plate.

FIG. 5 shows a substrate 1a on the active matrix side.
6 is a sectional view taken along line YY ′ of FIG. Here, a thin film transistor (hereinafter abbreviated as TFT) is used as a switching element used in this method.

A plurality of gate wirings 6a made of chromium, tantalum or the like are provided on a substrate 1a made of glass or the like, and a gate electrode 6b is provided branching from the gate wiring 6a. The gate wiring 6a functions as a scanning line. A gate insulating film 7 made of silicon nitride (SiNx), silicon oxide (SiOx), or the like is formed on the entire surface of the substrate 1a so as to cover the gate electrode 6b. On the gate insulating film 7 above the gate electrode 6b, amorphous silicon (hereinafter referred to as a-
A semiconductor layer 8 made of polycrystalline silicon (abbreviated as p-Si), CdSe, or the like is formed. On one end of the semiconductor layer 8, a source electrode 10b made of titanium, molybdenum, aluminum or the like is formed so as to overlap. As shown in FIG. 5, the source electrode 10b is branched from the source wiring 10a. At the other end of the semiconductor layer 8, a drain electrode 11 made of titanium, molybdenum, aluminum or the like is formed similarly to the source electrode 10b. A first film 2 is formed on the upper layer except for the portion on the drain electrode 11, and this is processed into a number of fine irregularities by using an etching method. A reflective film 5 made of a metal such as aluminum or silver is superimposed on an end of the drain electrode 11 opposite to the semiconductor layer 8. This reflection film 5 becomes a pixel electrode. The gate electrode 6b, the gate insulating film 7, the semiconductor layer 8, the source electrode 10b, and the drain electrode 11 constitute a TFT, and the TFT has a function of a switching element.

[0009] Liquid crystal is sealed between the active matrix substrate thus prepared and the opposing substrate having the transparent electrode, and bonded to form a reflection type liquid crystal display device.

In this reflection type liquid crystal display device, external light incident from the counter substrate side is reflected by the reflection film 5 of the active matrix substrate, and the reflected light passing through the liquid crystal layer is viewed from the counter substrate side.

If the first film 2 is formed on the substrate 1a on which the TFT is formed as described above, a large number of fine irregularities can be easily formed on the first film 2 by using the etching method. By forming the reflection film 5 with a metal or the like on the substrate 1a having the above, a pixel electrode having irregularities functioning as a reflection plate can be easily obtained.

A process for forming a pixel electrode having irregularities functioning as a reflector as described above will be described in more detail. FIG. 7 is a diagram for explaining the process of the portion A in FIG. First, on the gate insulating film 7 on the substrate 1a,
The film 2 is formed (FIG. 7A). Next, a photoresist 3 is applied thereon and patterned into a predetermined shape (FIG. 7).
(B)), a large number of fine irregularities are formed by etching the first film 2 (FIG. 7 (c)). Then, the photoresist 3 is peeled off, and the reflection film 5 serving as a pixel electrode is formed on the substrate 1a having the unevenness (FIG. 7D).

[0013]

However, when the reflection film 5 is formed by the above-described method, as shown in FIG. 7D, the protrusions 5a and the insulating portions where the photoresist remains at the time of FIG. The concave portion 5b from which the film 2a has been removed is planar, and the reflected light contains a large amount of specular reflection components.
It is almost mirror-like.

Although it is possible to increase or decrease the slope portion by devising the etching, the flat portion remains.
It is also possible to stop the etching of the first film halfway so that the underlying gate insulating film 7 is not shown. However, the etching shape varies depending on the distribution of the inner surface of the substrate, and the reflection characteristics vary in the surface. Problems arise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high contrast reflective liquid crystal display device provided with a reflective plate having a uniform and highly light-reflective reflective characteristic, and a method of manufacturing the same. .

[0016]

According to the present invention, there is provided a reflection type liquid crystal display device comprising a first film having irregularities and a liquid applied to the first film.
A reflector having an electrode made of a reflective film formed on a substrate having a large number of fine irregularities including a curved surface portion made of a second film formed by curing, and between the insulating substrate and the reflector And a sealed liquid crystal layer.

Further, the reflection type liquid crystal display device of the present invention has an insulating substrate on which a transparent electrode is formed, a first film having irregularities, and a first film formed by applying and curing a liquid on the first film. An active matrix substrate in which pixel electrodes made of a reflective film are formed on a substrate having a large number of fine irregularities including a curved surface portion made of two films, and a liquid crystal sealed between the insulating substrate and the active matrix substrate And a layer.

Here, the first film or the second film may be used as a protective film of a switching element on an active matrix substrate.

Further, the first film may be made of a photosensitive resin.

Further, the method of manufacturing a liquid crystal display device according to the present invention is a method of manufacturing a reflection type liquid crystal display device having a reflector in which an electrode made of a reflective film is formed on a substrate having a large number of fine irregularities. Forming a first film on one surface of a substrate constituting the reflection plate and processing it into a predetermined shape to form a large number of fine irregularities; and applying a liquid on the substrate on which the irregularities are formed. Then, the method includes a step of forming a second film by curing, and a step of forming an electrode made of a reflective film on the second film. In addition, the method of manufacturing a reflective liquid crystal display device of the present invention is a method of manufacturing a reflective liquid crystal display device having an active matrix substrate in which pixel electrodes formed of a reflective film are formed on a substrate having a large number of fine irregularities. A step of forming a first film on one surface of a substrate constituting the active matrix substrate and processing it into a predetermined shape to form a large number of fine irregularities, and forming the first film on the active matrix substrate on which the irregularities are formed. A step of forming a second film by applying and curing a liquid on the substrate, and a step of forming a pixel electrode made of a reflective film on the second film.

[0021]

The liquid is applied onto the irregularities formed by using the first film, so that the surface of the substrate is caused to have an upwardly convex arc shape on the convex portion and a downwardly convex circle on the concave portion due to the surface tension of the liquid. After the liquid is hardened, an uneven shape including a curved portion having a small flat portion is obtained. When a reflective film is formed on the unevenness including the curved surface portion, a specular component is reduced, and a reflector having characteristics closer to a scattering state than a mirror state can be obtained.

Further, the reflection film may be a pixel electrode on an active matrix substrate. In this case, the first film or the second film can be used as a protective film of the switching element on the active matrix substrate, and the protective film forming process can be omitted.

Here, if a photosensitive resin is used for the first film, the process of forming unevenness can be simplified.

[0024]

Embodiments of the present invention will be described below.

FIG. 1 is a view for explaining a manufacturing process of a reflection plate used in the reflection type liquid crystal display device.

A first film 2 is formed on a substrate 1 (see FIG. 1).
(A)). Next, a photoresist 3 is applied, patterned into a predetermined shape (FIG. 1B), and a large number of fine irregularities are created by etching the first film 2 (FIG. 1).
(C)). After the photoresist 3 is peeled off, a liquid material such as an acrylic resin is applied to the upper layer of the substrate 1 on which the irregularities are formed, and then cured to form the second film 4 (FIG. 1D).
Further, an electrode made of the reflection film 5 is formed on the second film 4 to form a reflection plate (FIG. 1E).

When the acrylic resin is applied with such a thickness that the substrate 1 does not appear, the flat portion of the unevenness of the first film 2 is eliminated, and a reflector having less regular reflection can be obtained. In addition, it is possible to eliminate surface roughness and unevenness of reflection caused by etching residues generated on the unevenness of the substrate 1 or the first film 2. The material of the second film 4 can be applied by making it liquid, such as an epoxy resin, in addition to the acrylic resin, and may be a material that can be cured after the application. The reflection film 5 is made of aluminum, silver, nickel,
Use chrome or the like.

The reflector thus prepared has a uniform and good light scattering property.

FIG. 2 is a view for explaining a manufacturing process of another reflection plate. First, a photosensitive resin film is formed as the first film 2 on the substrate 1 (FIG. 2A). Next, the first film 2
Is exposed and patterned into a predetermined shape to form a large number of fine irregularities (FIG. 2B). Further, a liquid material such as an acrylic resin is applied to the upper layer of the substrate 1 having the irregularities, and then cured to form the second film 4. Then, an electrode made of the reflection film 5 is formed on the second film 4 to form a reflection plate (FIG. 2C).

In this reflector, by using a photosensitive resin for the first film 2, the process can be omitted and the cost can be reduced.

Next, a reflection type liquid crystal display device of an active matrix type provided with these reflector structures is shown in FIG.
A description will be given based on FIG. FIG. 3 is a sectional view of this reflection type liquid crystal display device having a TFT as a switching element, and FIG. 4 is a plan view of the substrate 1a shown in FIG. A plurality of gate wirings 6a made of chromium, tantalum or the like are provided on a substrate 1a made of glass or the like, and a gate electrode 6b is provided branching from the gate wiring 6a. The gate wiring 6a functions as a scanning line.
A gate insulating film 7 made of silicon nitride (SiNx), silicon oxide (SiOx), or the like is formed on the entire surface of the substrate 1a so as to cover the gate electrode 6b. On the gate insulating film 7 above the gate electrode 6b, a semiconductor layer 8 made of a-Si, p-Si or the like is formed. Contact layers 9 made of a-Si (n +), p-Si (n +), etc. are formed at both ends of the semiconductor layer. On one end of the contact layer 9, a source electrode 10b made of titanium, molybdenum, aluminum, or the like is formed so as to overlap. As shown in FIG. 4, the source electrode 10b is branched from the source wiring 10a. The source wiring 10a functions as a signal line. At the other end of the contact layer 9, a drain electrode 11 made of titanium, molybdenum, aluminum or the like is formed similarly to the source electrode 10b.
The gate electrode 6b, the gate insulating film 7, the semiconductor layer 8, the source electrode 10b and the drain electrode 11 constitute a TFT,
It has the function of a switching element.

As described above, the first film 2, the second film 4, and the reflection film 5 having irregularities are formed on the substrate 1a on which the TFT is formed, in the same manner as in the above-described manufacturing process of the reflection plate. This reflection film 5 becomes a pixel electrode. Here, the first film or the second film
If the film 4 is made insulating, these films are formed so as to cover the TFT portion as shown in FIG.
And the process can be simplified. However, in this case, after forming the second film 4, the second
Reflective film 5 formed on film 4 and drain electrode 11 of TFT
Must be formed with a contact hole 12 for electrical connection between

A color filter 13 is formed on the insulating substrate 1b facing the substrate 1a. Color filter 1
A transparent electrode 14 made of ITO or the like is formed on the entire surface of the substrate 3. Both substrates are further provided with an alignment film 15 and bonded to face each other. A liquid crystal for a phase change type guest-host system in which a black dye is mixed is sealed as a liquid crystal layer, so that a reflection plate which does not require a polarizing plate is provided. Type liquid crystal display device is completed.

In this reflective liquid crystal display device, external light incident from the opposing insulating substrate 1b is reflected by the reflective film 5 on the substrate 1a, and reflected light passing through the liquid crystal 16 is viewed from the insulating substrate 1b side. Will be.

The pixel electrode of this reflection type liquid crystal display device has a uniform reflection characteristic with good light scattering properties, whereby a good contrast can be realized.

In this embodiment, T is used as the switching element.
Although the case where the FT is used has been described, a diode, a varistor, an MIM element, or the like may be a switching element. Further, a simple matrix system without using a switching element may be used.

In this embodiment, a reflective plate structure is provided as a pixel electrode on the substrate 1a side. However, a transparent electrode may be used for the pixel electrode, and a reflective plate structure may be used for the opposing electrode on the insulating substrate 1b side. However, the color filter 13 is not
On the side.

In this case, external light incident from the substrate 1a is reflected by the reflection film on the insulating substrate 1b facing the substrate, and reflected light passing through the liquid crystal layer 16 is viewed from the substrate 1a side.

The display mode is the same as that of the phase change type guest used in this embodiment. In addition to the host mode, a two-tier guest. Display modes such as a light absorption mode such as a host mode and a light scattering type display mode such as a polymer dispersion type LCD can also be adopted.

[0040]

According to the present invention, it is possible to obtain a reflector having uniform reflection characteristics with good light-scattering properties, so that the contrast of the liquid crystal display device can be improved.

The process can be simplified by using a photosensitive resin for the first film, or in the case of an active matrix reflective liquid crystal display device, by using the first film or the second film as a protective film. In addition, the cost can be reduced and the yield can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a manufacturing process of a reflection plate in a reflection type liquid crystal display device according to one embodiment of the present invention.

FIG. 2 is a diagram for explaining a manufacturing process of another reflector.

FIG. 3 is a sectional view of an active matrix type reflection type liquid crystal display device showing one embodiment of the present invention.

FIG. 4 is a plan view of the active matrix substrate shown in FIG.

FIG. 5 is a plan view of an active matrix substrate used in a conventional reflective liquid crystal display device.

FIG. 6 is a sectional view taken along line Y-Y 'of FIG.

FIG. 7 is a view for explaining a manufacturing process of a conventional reflector.

[Explanation of symbols]

 1, 1a Substrate 1b Insulating substrate 2 First film 4 Second film 5 Reflective film 14 Transparent electrode 16 Liquid crystal layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hisaka Nakamura 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Seiichi Mitsui 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka No. Within Sharp Corporation (72) Inventor Naofumi Kimura 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Within Sharp Corporation (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/1335 520 G02B 5 / 08 G02F 1/1333 500

Claims (7)

(57) [Claims] 1. A reflection type liquid crystal display device which performs display by reflecting incident light, comprising: an insulating substrate on which a transparent electrode is formed; a first film having irregularities; and applying and curing a liquid on the first film. A reflector having an electrode made of a reflective film formed on a substrate having a large number of fine irregularities including a curved surface portion made of a second film formed by the above process, and sealing between the insulating substrate and the reflector A reflective liquid crystal display device, comprising: a liquid crystal layer formed by: 2. A reflection type liquid crystal display device which performs display by reflecting incident light, comprising: an insulating substrate on which a transparent electrode is formed; a first film having irregularities; and applying and curing a liquid on the first film. An active matrix substrate in which pixel electrodes made of a reflective film are formed on a substrate having a large number of fine irregularities including a curved surface portion made of a second film formed by performing And a liquid crystal layer sealed between the reflective liquid crystal display devices. 3. The reflection type liquid crystal display device according to claim 1, wherein said first film is made of a photosensitive resin. 4. The reflection type liquid crystal display device according to claim 2, wherein said first film is a protection film for a switching element on an active matrix substrate. 5. The reflection type liquid crystal display device according to claim 2, wherein said second film is a protection film for a switching element on an active matrix substrate. 6. A method for manufacturing a reflection type liquid crystal display device having a reflection plate on which an electrode made of a reflection film is formed on a substrate on which a large number of fine irregularities are formed, wherein one of the substrates constituting the reflection plate is provided. Forming a first film on the surface and processing it into a predetermined shape to form a large number of fine irregularities; applying a liquid on the substrate on which the irregularities are formed, and curing to form a second film And a step of forming an electrode formed of a reflective film on the second film. 7. A method of manufacturing a reflection type liquid crystal display device having an active matrix substrate in which pixel electrodes made of a reflection film are formed on a substrate on which a large number of fine irregularities are formed, wherein the active matrix substrate is formed. Forming a first film on one surface of the substrate, processing it into a predetermined shape to form a large number of fine irregularities, applying a liquid on the active matrix substrate having the irregularities formed thereon, and curing the liquid; A method of manufacturing a reflective liquid crystal display device, comprising: forming a second film; and forming a pixel electrode made of a reflective film on the second film.