JPH05232465A - Reflection type liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To improve the contrast of the reflection type liquid crystal display device by obtaining reflection plates having uniform light scatterability and good reflection characteristics. CONSTITUTION:This liquid crystal display device is constituted by having an insulating substrate 1b on which transparent electrodes 14 are formed, an active matrix substrate 1a which is constituted by forming pixel electrodes consisting of reflection films 5 on a substrate having many pieces of fine ruggedness including curved surface parts consisting of first films 2 having ruggedness and second films 4 formed by applying liquid on the first films 2 and curing the liquid and a liquid crystal layer 16 which is encapsulated between the insulating substrate 1b and the active matrix substrate 1a. The liquid for forming the second films 4 is applied on the first films 2 having many pieces of the fine ruggedness and curing the coating, by which the above-mentioned ruggedness having the plane parts are made into the ruggedness having the curved surface parts. The light scattering characteristic of the reflection films 5 formed thereon is thereby improved.

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 for displaying by reflecting incident light and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, the application of liquid crystal display devices to word processors, laptop personal computers, pocket televisions, etc. has been rapidly developing. Among the liquid crystal display devices, the reflection type liquid crystal display device that reflects light incident from the outside for display has low power consumption because it does not require a backlight, and is noted for its thinness and lightness. There is.

Conventionally, a TN has been used for a reflective liquid crystal display device.
The (twisted nematic) method and the STN (super twisted nematic) method are used. However, in these methods, 1/2 of the light intensity of natural light is not necessarily used for display by the polarizing plate, and the display is There is a problem that it gets dark.

To solve this problem, a display mode has been proposed in which natural light is effectively used without using a polarizing plate. An example of such a mode is a phase transition type guest-host system. (DL White and and
G. N. Taylor: J. Appl. Phys. Four
5 4718 1974). In this mode, the cholesteric-nematic phase transition phenomenon by the electric field is utilized. A reflective multi-color display in which a micro color filter is further combined with this system has been proposed (Proceedings of the).
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 optimum reflection characteristics. In the above-mentioned document, the surface of a substrate made of glass or the like is roughened with an abrasive, and the unevenness of the surface is controlled by changing the etching time with hydrofluoric acid, and a silver reflection film is formed on the unevenness. The formed reflector is described.

However, since the concave and convex portions are formed on the reflecting plate described in the above-mentioned document by scratching the glass substrate with the abrasive, it is impossible to form the concave and convex portions 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 reflective 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 large number of fine irregularities having a predetermined shape are formed on the surface of the substrate by using an etching method, and a reflective film of silver or the like is further formed thereon. Then, the method of making it into a reflector is proposed. 5 and 6 show the structure of an active matrix type reflective 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 plan view of FIG. 6, and FIG. 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 branched 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. Amorphous silicon (hereinafter a-) is formed on the gate insulating film 7 above the gate electrode 6b.
A semiconductor layer 8 made of polycrystalline silicon (abbreviated as Si) (hereinafter abbreviated as p-Si), CdSe, or the like is formed. A source electrode 10b made of titanium, molybdenum, aluminum, or the like is superposed on one end of the semiconductor layer 8. As shown in FIG. 5, the source electrode 10b is branched from the source wiring 10a. A drain electrode 11 made of titanium, molybdenum, aluminum, or the like is formed on the other end of the semiconductor layer 8 similarly to the source electrode 10b. A first film 2 is formed on the upper layer of the portion other than the drain electrode 11 and is processed into a large number of fine irregularities by an etching method. A reflective film 5 made of a metal such as aluminum or silver is superposed on the end of the drain electrode 11 opposite to the semiconductor layer 8. This reflective 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 form a TFT, and the TFT has a function of a switching element.

A liquid crystal is sealed and bonded between the active matrix substrate thus prepared and the counter substrate having the transparent electrode to form a reflective liquid crystal display device.

In this reflection type liquid crystal display device, the 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.

When 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 an etching method. By forming the reflective film 5 of a metal or the like on the substrate 1a having a groove, it is possible to easily obtain a pixel electrode having unevenness that functions as a reflector.

The process of forming the pixel electrode having the unevenness functioning as the reflection plate as described above will be described in more detail. FIG. 7 is a diagram for explaining the process of part A in FIG. First, a first film is formed 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 (see FIG. 7).
(B)) A large number of fine irregularities are formed by etching the first film 2 (FIG. 7C). Then, the photoresist 3 is peeled off, and the reflection film 5 to be the pixel electrode is formed on the substrate 1a having the unevenness (FIG. 7D), and the process is completed.

[0013]

However, when the reflection film 5 is formed by the above method, as shown in FIG. 7 (d), the protrusions 5a and the insulation remaining on the photoresist at the time of FIG. 7 (c) are removed. The recess 5b from which the film 2a has been removed is planar, and the reflected light thereof contains a large amount of specular reflection components.
It is close to a mirror surface.

It is possible to increase or decrease the slope portion by devising the etching, but 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 exposed. However, the etching shape differs depending on the distribution of the inner surface of the substrate during etching, and the reflection characteristics may vary within the surface. The problem occurs.

In view of the above problems, an object of the present invention is to provide a reflection type liquid crystal display device having a high contrast and a reflection plate having a reflection characteristic that is uniform and has a good light scattering property, and a manufacturing method thereof. ..

[0016]

A reflection type liquid crystal display device of the present invention comprises a first film having irregularities and a liquid applied to the first film.
Between the insulating plate and the reflective plate, the reflective plate having the electrode formed of the reflective film on the substrate having a large number of fine irregularities including the curved surface part formed of the second film formed by curing. And a liquid crystal layer encapsulated therein.

Further, the reflective liquid crystal display device of the present invention comprises an insulating substrate having a transparent electrode formed thereon, 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 a pixel electrode made of a reflective film is formed on a substrate having a large number of minute 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 a protective film for the switching element on the active matrix substrate.

The first film may be made of a photosensitive resin.

Further, the method of manufacturing a liquid crystal display device of the present invention is a method of manufacturing a reflection type liquid crystal display device having a reflector having electrodes made of a reflective film formed on a substrate on which a large number of fine irregularities are formed. Then, a step of forming a first film on one surface of the substrate that constitutes 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 step of forming a second film by curing and the step of forming an electrode made of a reflective film on the second film are included. Further, the method for manufacturing a reflective liquid crystal display device of the present invention is a method for manufacturing a reflective plate liquid crystal display device having 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. There is a step of forming a first film on one surface of a substrate forming the active matrix substrate and processing it into a predetermined shape to form a number of fine irregularities, and an active matrix substrate on which the irregularities are formed. It includes a step of forming a second film by applying a liquid to and hardening the liquid, and a step of forming a pixel electrode made of a reflective film on the second film.

[0021]

By applying the liquid on the unevenness formed by using the first film, the surface tension of the liquid causes the surface of the substrate to have an upwardly convex arc shape for the convex portion and a downwardly convex circle for the concave portion. After the liquid is hardened, it is formed into an arc shape, and thus unevenness including a curved surface portion having a small number of flat portions is obtained. When a reflection film is formed on the unevenness including the curved surface portion, the specular reflection component is reduced, and a reflection plate having a characteristic closer to a scattering state than a specular state can be obtained.

The reflective film may be a pixel electrode on the active matrix substrate. In this case, the first film or the second film can be a protective film for the switching element on the active matrix substrate, and the protective film forming process can be omitted.

If a photosensitive resin is used for the first film, the process of forming the concavities and convexities can be simplified.

[0024]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a diagram for explaining a manufacturing process of a reflector used in this reflection type liquid crystal display device.

The first film 2 is formed on the substrate 1 (see FIG. 1).
(A)). Next, a photoresist 3 is applied, patterned into a predetermined shape (FIG. 1B), and the first film 2 is etched to form a large number of fine irregularities (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 unevenness is formed and then cured to form the second film 4 (FIG. 1D).
Further, an electrode composed of the reflection film 5 is formed on the upper layer of the second film 4 to form a reflection plate (FIG. 1 (e)).

When the acrylic resin is applied with a thickness such that the substrate 1 does not appear, the flat portion of the unevenness of the first film 2 is eliminated, and a reflection plate with less specular reflection can be obtained. Further, it is possible to eliminate the surface roughness generated on the unevenness of the substrate 1 or the first film 2 and the uneven reflection caused by the etching residue. The material of the second film 4 can be applied by making it liquid such as epoxy resin in addition to the acrylic resin, and any material that can be cured after application may be used. The reflection film 5 is made of aluminum, silver, nickel, which has high reflection efficiency.
Use chrome, etc.

The reflector thus prepared has uniform and good light-scattering reflection characteristics.

FIG. 2 is a view for explaining another manufacturing process of the reflector. 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 irregularities and then cured to form the second film 4. Then, an electrode made of the reflection film 5 is formed on the upper layer of the second film 4 to form a reflection plate (FIG. 2C).

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

Next, an active-matrix reflective liquid crystal display device having these reflector structures will be described with reference to FIG.
And FIG. 4 will be described. FIG. 3 is a sectional view of this reflective 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 branched 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. A semiconductor layer 8 made of a-Si, p-Si, or the like is formed on the gate insulating film 7 above the gate electrode 6b. Contact layers 9 made of a-Si (n +), p-Si (n +), etc. are formed on both ends of the semiconductor layer. A source electrode 10b made of titanium, molybdenum, aluminum, or the like is superposed on one end of the contact layer 9. 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. A drain electrode 11 made of titanium, molybdenum, aluminum, or the like is formed on the other end of the contact layer 9 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 form a TFT,
It has the function of a switching element.

As described above, the first film 2, the second film 4, and the reflective film 5 having the unevenness are formed on the substrate 1a on which the TFT is formed in the same manner as in the manufacturing process of the reflective plate described above. This reflective film 5 becomes a pixel electrode. Here, the first film or the second film
If the film 4 is made insulative, by forming these films so as to cover the TFT portion as shown in FIG.
Can be used as a protective film, and the process can be simplified. However, in this case, after forming the second film 4, the second film 4 is formed.
The reflective film 5 formed on the film 4 and the drain electrode 11 of the TFT
A contact hole 12 for electrically connecting with must be formed.

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 3. An alignment film 15 is further formed on both the substrates, and the substrates are laminated so as to face each other. Type liquid crystal display device is completed.

In this reflective liquid crystal display device, external light incident from the opposing insulating substrate 1b side 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. It will be.

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

In this embodiment, T is used as a switching element.
Although the case where the FT is used has been described, the diode, the varistor, the MIM element and the like may be switching elements. Alternatively, a simple matrix method that does not use a switching element may be used.

Further, in this embodiment, the reflector structure is provided as the pixel electrode on the substrate 1a side, but the pixel electrode may be a transparent electrode and the opposing electrode on the insulating substrate 1b side may be the reflector structure. However, the color filter 13 is the substrate 1a
Provide on the side.

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

The display mode is the phase transition type guest used in this embodiment. In addition to host mode, two-tier guest. A display mode such as a light absorption mode such as a host mode and a light scattering display mode such as a polymer dispersed LCD can also be adopted.

[0040]

According to the present invention, since a reflector having uniform and good light-scattering reflection characteristics can be obtained, the contrast of a liquid crystal display device can be improved.

Further, a photosensitive resin is used for the first film, and in the case of an active matrix type reflection type liquid crystal display device, the process is simplified by using the first film or the second film as a protective film. Therefore, it is possible to reduce the cost and improve the yield.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a reflector in a reflective liquid crystal display device according to an embodiment of the present invention.

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

FIG. 3 is a cross-sectional view of an active matrix reflective liquid crystal display device showing an 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 the line Y-Y ′ of FIG.

FIG. 7 is a diagram for explaining a conventional manufacturing process of a 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hisawa Nakamura 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Co., Ltd. (72) Seiichi Mitsui 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka No. 22 Inside Sharp Corporation (72) Inventor Naofumi Kimura 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside Sharp Corporation

Claims (7)

[Claims] 1. A reflective liquid crystal display device for displaying by reflecting incident light, an insulating substrate on which a transparent electrode is formed, a first film having irregularities, and a liquid applied and cured on the first film. A reflective plate in which 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, and enclosed between the insulating substrate and the reflective plate. A reflective liquid crystal display device, comprising: 2. A reflective liquid crystal display device for displaying by reflecting incident light, an insulating substrate on which a transparent electrode is formed, a first film having irregularities, and a liquid applied and cured on the first film. An active matrix substrate in which a pixel electrode made of a reflective film is formed on a substrate having a large number of fine irregularities including a curved surface portion made of the second film, and the insulating substrate and the active matrix substrate. And a liquid crystal layer enclosed between the reflective liquid crystal display device and the liquid crystal layer. 3. The reflective liquid crystal display device according to claim 1, wherein the first film is made of a photosensitive resin. 4. The reflective liquid crystal display device according to claim 2, wherein the first film is a protective film for a switching element on an active matrix substrate. 5. The reflective liquid crystal display device according to claim 2, wherein the second film is a protective film for a switching element on an active matrix substrate. 6. A method of manufacturing a reflection type liquid crystal display device, comprising: a reflective plate having an electrode made of a reflective film formed on a substrate having a large number of fine irregularities formed thereon; A step of forming a first film on one side and processing it into a predetermined shape to form a large number of fine irregularities; and forming a second film by applying a liquid on the substrate on which the irregularities are formed and curing it. And a step of forming an electrode made of a reflective film on the second film, the manufacturing method of the reflective liquid crystal display device. 7. A method of manufacturing a reflective liquid crystal display device, comprising: an active matrix substrate in which pixel electrodes made of a reflective film are formed on a substrate on which a large number of fine irregularities are formed; A step of forming a first film on one surface of the substrate and processing it into a predetermined shape to form a large number of fine irregularities; and applying and curing a liquid on the active matrix substrate on which the irregularities are formed. A method of manufacturing a reflective liquid crystal display device, comprising: a step of forming a second film; and a step of forming a pixel electrode made of a reflective film on the second film.