JPH0736029A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a reflection type LCD with which mis-registration of pixels hardly arises even if the pixels are formed to smaller sizes to attain higher fineness. CONSTITUTION:The liquid crystal display element of the reflection type includes a relatively thick glass substrate 8 for supporting, a reflection layer 9 formed on the front surface of this glass substrate 8 for supporting, a polarizing film 10 adhered to this reflection layer 9, an adhesive layer 11 applied on the front surface of this polarizing film 10, a reflection side glass substrate 1 adhered to the polarizing film 10 by the adhesive layer 11 and transparent electrodes 2 formed on the front surface of the reflection side glass substrate 1 as one of a pair of the substrates 1, 7 holding a liquid crystal layer 12.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a liquid crystal display device (LCD).
In particular, the present invention relates to a reflective liquid crystal display device. LCD is
It is widely used as a display element for OA equipment, especially for portable OA equipment, taking advantage of its advantages of being lightweight, thin, and power saving. With the recent increase in the capacity of processing information, a high-definition and large-screen LCD is required.

[0002]

2. Description of the Related Art A conventional reflective LCD will be described below with reference to FIG. A polarizing film 51 and a reflecting plate 52 are adhered to the back surface of the reflecting side glass substrate 50 in this order. Transparent electrodes 55 are formed in stripes on the surface (liquid crystal surface) of the reflection-side glass substrate 50 that sandwiches the liquid crystal. The liquid crystal surface of the reflection side glass substrate 50 and the transparent electrode 5
5 is covered with a polyimide alignment film 58.

On the liquid crystal surface of the transmission side glass substrate 53, stripe-shaped transparent electrodes 54 are formed in a direction orthogonal to the transparent electrodes 55. The liquid crystal surface of the transmissive glass substrate 53 and the transparent electrode 54 are covered with a polyimide alignment film 57 like the liquid crystal surface of the reflective glass substrate.

The glass substrate 50 on the reflection side and the glass substrate 53 on the transmission side are held and adhered by a spacer (not shown) so that the liquid crystal surfaces thereof face each other at intervals of several μm. A liquid crystal 56 is filled in the space between the liquid crystal surfaces of both glass substrates. A polarizing film 59 is adhered to the surface of the transmission side glass substrate 53 opposite to the liquid crystal surface. The polarizing films 51 and 59 are arranged, for example, with their polarization axes orthogonal to each other.

The transparent electrodes 54 and 55 form a simple matrix, and the intersections thereof form one pixel. When the liquid crystal 56 is a twisted nematic liquid crystal, the liquid crystal layer has a function of rotating the polarization axis of incident light by 90 °.
If the polarization axes of the polarization films 51 and 59 are aligned with the polarization axis directions on both surfaces of the liquid crystal layer, light is transmitted while the electric field is off.

When a voltage is applied to the corresponding transparent electrodes 54 and 55, the liquid crystal molecules are aligned in the direction of the electric field, and the optical rotation characteristic of the pixel is lost. Since the polarizing films 51 and 59 are orthogonal to each other, light is blocked. In this way, only light having a specific polarization direction can pass through the polarizing films 51 and 59, so that the brightness of the pixel can be changed by applying a voltage between the transparent electrodes corresponding to the pixel. .
The arrangement of the polarization axes and the optical rotation characteristics of the liquid crystal layer described above are merely examples.

[0007]

A reflective glass substrate 50.
The thickness is usually 0.7 to 1.1 mm. On the other hand, 1m
When performing high-definition display having a resolution of 4 to 5 lines per m, the pitch of the transparent electrodes 55 and 54 is about 200 μm. When the incident light is perpendicularly incident on the reflection surface of the glass substrate, the incident light and the reflected light pass through the same pixel. However, as shown in FIG. 3, when the light is obliquely incident, the incident light passes through the pixel 61 and the reflected light passes through the pixel 62 different from that.

As described above, when the pixels through which the incident light and the reflected light pass are not the same, the image is doubled and so-called pixel shift occurs. The higher the resolution, the more likely the pixel shift is to occur even at a small incident angle. Further, as the screen becomes larger, the angle of incidence at the peripheral portion of the screen becomes larger with respect to the observer, so that pixel shift easily occurs.

The pixel shift basically occurs because the distance between the liquid crystal layer and the reflective layer is larger than the pixel pitch. Therefore, in order to prevent the pixel shift, the distance between the liquid crystal layer and the reflective layer may be set to be equal to or smaller than the pixel pitch.

FIG. 4 shows an example in which a transparent electrode on the liquid crystal surface on the reflection side is directly formed on the polarizing film instead of the glass substrate 50 on the reflection side in FIG. The reflective film 52 is formed on the supporting glass substrate 60, and the polarizing film 51 is adhered thereon. The transparent electrode 55 is directly formed on the polarizing film 51.

With such a structure, the distance between the liquid crystal layer and the reflective film 52 is only the thickness of the polarizing film 51. If a polarizing film with a thickness of about 30 μm is used, it is sufficiently smaller than the pixel pitch of 200 μm.
Pixel shift can be prevented.

However, the polarizing film is a resin such as polyvinyl alcohol impregnated with iodine and generally has low heat resistance. Therefore, in the method of directly forming the transparent electrode on the polarizing film, the polarizing film cannot withstand the high heat treatment at the time of producing the transparent electrode and the liquid crystal molecular alignment film, and the polarizing function is lost. Therefore, it is not realistic to manufacture the LCD having the structure shown in FIG.

It is also conceivable to reduce the thickness of the reflection side glass substrate 50 of FIG. 3 to about 100 μm. But,
If the thickness is about 100 μm, handling in the manufacturing process becomes extremely difficult, and the yield is extremely reduced.

An object of the present invention is to provide a reflective LCD,
An object of the present invention is to provide an LCD in which pixel shift is unlikely to occur even when the pixel size is reduced and the resolution is high.

[0015]

The liquid crystal display element of the present invention is a reflection type liquid crystal display element, wherein a relatively thick supporting glass substrate, a reflecting layer formed on the surface of the supporting glass substrate, and A polarizing film adhered to the reflective layer,
An adhesive layer applied to the surface of the polarizing film, a reflective side glass substrate adhered to the polarizing film by the adhesive layer, and a transparent electrode on one side formed on the surface of the reflective side glass substrate are liquid crystal. It is included as one of a pair of substrates sandwiching a layer.

[0016]

By narrowing the distance between the transparent electrode and the reflective layer, the distance between the passing point of incident light and the passing point of reflected light in the liquid crystal layer can be shortened. Therefore, even if the pixel pitch is made fine, the occurrence of pixel shift can be suppressed.

Further, the liquid crystal layer portion including the transparent electrode and the liquid crystal layer and the reflective layer portion including the reflective layer and the polarizing film are separately produced and then attached to each other, which causes difficulty in handling in the manufacturing process. Therefore, a decrease in yield can be avoided.

[0018]

EXAMPLES Examples of the present invention will be described below by taking a Super Twisted Nematic (STN) type LCD showing an optical rotation performance of 180 to 270 ° as an example. The STN LCD has a sharp change in light transmittance with respect to a change in applied voltage (effective value), and is widely used especially for a large-screen LCD.

FIG. 1 shows an STN type L according to an embodiment of the present invention.
Indicates a CD. The LCD according to the present embodiment includes a liquid crystal layer portion 13 including a transmissive side glass substrate 7, a relatively thin reflective side glass substrate 1 and a liquid crystal layer 12 sandwiched therebetween, a supporting glass substrate 8, a reflective layer 9 and a polarizing film. The reflective layer portion 14 is composed of 10 and the adhesive layer 11 for bonding the both.

Transparent electrodes 2 are formed in stripes on the liquid crystal surface of the reflection side glass substrate 1. The liquid crystal surface of the reflection-side glass substrate 1 and the transparent electrode 2 are covered with a polyimide alignment film 4.

On the liquid crystal surface of the transmission side glass substrate 7, the transparent electrodes 3 are formed in stripes in the direction orthogonal to the transparent electrodes 2.
Are formed. The liquid crystal surface of the transmissive side glass substrate 7 and the transparent electrode 3 are covered with a polyimide alignment film 5 like the liquid crystal surface of the reflective side glass substrate.

Reflecting side glass substrate 1 and transmitting side glass substrate 7
Are held and adhered by spacers (not shown) so that their liquid crystal surfaces face each other at intervals of several μm. In the space between the liquid crystal surfaces of both glass substrates, the liquid crystal 6
Is filled.

The liquid crystal layer portion 13 having the above-described structure is manufactured in the same process as that of the conventional STN type LCD. In another step, chromium and aluminum are vacuum-deposited on the surface of the supporting glass substrate 8 in this order to form the reflective layer 9. After that, the polarizing film 10 is attached to produce the reflective layer portion 14.

Acrylic UV-curable resin is applied to the adhesive surfaces of the liquid crystal layer 13 and the reflective layer 14, which are manufactured in separate steps, and they are adhered to each other. In this configuration, the reflection-side glass substrate 1 has a thickness of, for example, 100 to 200 μm, and the total thickness of the adhesive layer 11 and the polarizing film 10 is 250 to 350 at the maximum.
.mu.m, high-quality display without pixel shift is possible even when performing high-definition display.

The results of experiments comparing the LCD according to this embodiment with the LCD according to the conventional example will be described below. The LCD used in this experiment has an effective display area of 188 x 78 m.
An indium-tin oxide (ITO) substrate with m ² and a pixel count of 846 × 351 was used. That is, the pixel pitch is 2
It is 00 μm. The thickness of the transparent glass substrate 7 is 700μ
m, and the thickness of the reflection side glass substrate 1 is 100 μm. The manufacturing method used was the same as that of the conventional STN LCD.

In a separate step, the supporting glass substrate 8 having a thickness of 700 μm was washed, and chromium was vacuum-deposited at 1000Å and aluminum was continuously vacuum-deposited at 1500Å. Next, thickness 30
A polarizing layer 10 having a thickness of μm was attached to produce a reflective layer portion 14.

Liquid crystal layer portion 13 and reflection layer portion 1 which are separately manufactured
Acrylic resin-based UV curable resin was applied to the bonding surface of No. 4 by about 10 μm and cured by irradiating UV rays from a high pressure mercury lamp.

The LCD manufactured in this manner is used as an ordinary STN.
As a result of driving at 1/180 duty using the driving circuit, the viewing angle range in which no pixel shift occurs is ± 20 °,
The contrast ratio was 18: 1. In the LCD according to the conventional example in which the reflective glass substrate 50 shown in FIG. 3 having a thickness of 0.7 mm is used, the viewing angle range in which no pixel shift occurs is ± 7 °, and the contrast ratio is 10: 1. .

As described above, the LCD according to the embodiment manufactured in the present experiment has a viewing angle range in which no pixel shift occurs about 3 times and the contrast ratio is improved to nearly 2 times as compared with the LCD according to the conventional example. Was done.

If the refraction at the interface is ignored, the viewing angle is 7 °.
At this time, the point where the incident light and the reflected light cross the liquid crystal surface of the reflection side glass substrate is shifted by about 180 μm. This is a value close to the pixel pitch of 200 μm. Therefore, if the distance between the passing point of the incident light and the passing point of the reflected light in the liquid crystal layer is smaller than the pixel pitch, it can be estimated that no pixel shift will occur.

If the pixel shift depends only on the distance between the passing point of the incident light and the passing point of the reflected light in the liquid crystal layer, as in the LCD manufactured in this experiment, the liquid crystal surface of the reflecting side glass substrate and the reflecting layer are separated. When the distance is about 140 μm, it is estimated that a viewing angle of about 30 ° is secured, and the result of this experiment can almost explain that the viewing angle at which no pixel shift occurs is about 20 °. Let's do it.

The black-and-white reflective LCD has been described above, but the present invention is also applicable to a color reflective LCD. An example of applying the present invention to a color LCD will be described below.

FIG. 2 shows a color LCD according to another embodiment of the present invention. This example is different from the above example in that a color filter is included in the adhesive layer that adheres the liquid crystal layer portion and the reflective layer portion.
That is, the polarizing film 10 is once adhered between another reflection side glass substrate 15 and the reflection film 9, and the reflection side glass substrate 1
And another reflection side glass substrate 15 are adhered to each other by an adhesive layer 11a. At this time, the adhesive layers 11a are adhered so as to include the color filters 16a, 16b, 16c.

The color filters include a red filter 16a and a green filter 16 at positions corresponding to respective pixels of the transparent electrode.
b, the blue filters 16c are periodically arranged. With such a structure, the distance between the liquid crystal surface of the reflection-side glass substrate 1 and the reflection layer 9 can be shortened as in the above embodiment. For this reason, it becomes possible to prevent the pixel shift from occurring even in the high-definition display.

Although the process of forming the liquid crystal layer portion using a thin glass substrate in the same manner as the conventional method and joining the liquid crystal layer portion to the reflective layer portion has been described, other manufacturing processes may be adopted. For example, a liquid crystal cell may be formed by forming a transparent electrode pattern on a thin substrate, joining the reflective layer portion, and then combining the transparent electrode pattern with the transmissive side substrate. The bonding is not limited to the ultraviolet curable resin as long as it can be performed at a low temperature. For example, it is possible to use an epoxy resin or the like.

Although the STN liquid crystal has been described in the above embodiment, the present invention is not limited to the STN liquid crystal. For example, TN liquid crystal, ferroelectric liquid crystal, or the like may be used. Further, in the above embodiment,
Although the simple matrix type LCD has been described, the present invention is also applicable to an active matrix type LCD using a thin film transistor for driving each liquid crystal cell.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0038]

As described above, according to the present invention,
In the reflective LCD, even when the pixel pitch is made fine to provide a high-definition display, pixel deviation is unlikely to occur and a wide viewing angle can be secured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a reflective LCD according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of a reflective LCD according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional reflective LCD.

FIG. 4 is a cross-sectional view of a reflective LCD in which a transparent electrode is directly formed on a polarizing film to solve the conventional problem.

[Explanation of symbols]

 1, 15 reflection side glass substrate 2, 3, 54, 55 transparent electrode 4, 5, 57, 58 alignment film 6, 56 liquid crystal 7, 53 transmission side glass substrate 8, 60 supporting glass substrate 9, 52 reflection layer 10, 51, 59 Polarizing film 11, 11a Adhesive layer 12 Liquid crystal layer 13 Liquid crystal layer part 14 Reflective layer part 16a, 16b, 16c Color filter 50 Reflective glass substrate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tetsuya Makino 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Masashi Watanabe, 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited

Claims (3)

[Claims] 1. In a reflective liquid crystal display device, a relatively thick supporting glass substrate (8), a reflecting layer (9) formed on the surface of the supporting glass substrate (8), and the reflecting layer (8). Polarizing film (10) adhered to 9)
An adhesive layer (11) applied to the surface of the polarizing film (10); and the polarizing film (10) by the adhesive layer (11).
A liquid crystal display device comprising a reflective side glass substrate (1) adhered to a substrate and a transparent electrode (2) formed on the surface of the reflective side glass substrate (1) as one of a pair of substrates sandwiching a liquid crystal layer. 2. The liquid crystal display element according to claim 1, wherein the adhesive layer (11) is a photocurable resin. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal layer contains a twisted nematic liquid crystal, a super twisted nematic liquid crystal, or a ferroelectric liquid crystal.