JPH117006A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure of the reflection type liquid crystal display device which can obtain high visibility while holding lightness and contrast of display without lowering the reflection factor of a reflecting surface and the transmissivity of a liquid crystal layer. SOLUTION: An optical modulating filter 40 in such a structure that an optical modulating layer 42 is sandwiched between transparent sheets 41 and 43 formed of polycarbonate is adhered onto the external surface of a surface- side glass substrate 10. In the optical modulating layer 42 of the optical modulating filter 40, many light shield layers 44 made of black resin which absorbs visible light are sealed with transparent resin almost at right angles to the lamination surface or slantingly to some extent from the orthogonal direction.

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, and more particularly to a structure for improving visibility of a liquid crystal display.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device, a reflection surface is provided inside a liquid crystal display, and light incident from the outside passes through a liquid crystal layer and is reflected by the reflection surface, and then passes through the liquid crystal layer again. There are reflective liquid crystal displays configured to emit light.

In a reflection type liquid crystal display device, various liquid crystal layers are held between a light-transmitting substrate disposed on the light incident side and a substrate disposed on the opposite side thereof. A reflection surface is formed on the opposite side. The reflection surface may be formed on the front surface or the back surface of the opposite substrate, and the pixel electrode formed on the inner surface of the opposite substrate may be formed of a metal electrode such as Cr having a high reflectance. May be formed also as a pixel electrode.

According to the reflection type liquid crystal display device, the display can be visually recognized by reflection of external light.
There is an advantage that a light source is not required and power consumption of the device can be reduced. On the other hand, the above-mentioned reflective liquid crystal display device has a drawback that the display is generally dark because the display can be viewed with light generated by the reflection of external light. To overcome this shortcoming,
Various liquid crystal display devices using a scattering mode capable of displaying without using a polarizing plate have been developed. These liquid crystal display devices generally perform display by switching between a state in which light is scattered by the liquid crystal layer and a state in which the liquid crystal layer is transparent, so that it is not necessary to use a polarizing plate. There is an effect that the display can be brightened.

[0005]

By the way, in a reflection type liquid crystal display device having a dark display, direct light from a light source enters eyes and the reflection of a background becomes remarkable due to reflection of external light. However, there is a problem that the visibility of the display is significantly impaired. On the other hand, in order to reduce the reflection of external light, the reflectance of the reflection surface and the transmittance of the liquid crystal layer must be reduced, and thus there is a problem that the brightness and contrast of the display are reduced.

In particular, as described above, in a liquid crystal display using a scattering mode without using a polarizing plate, the brightness of display can be ensured, but when the liquid crystal layer is in a light transmitting state, external light is reflected as it is. Therefore, there is a problem that the visibility is further reduced, such as being confused by the direct light or making the display difficult to see due to the reflection of the background.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to maintain high brightness and contrast of a display without lowering the reflectance of a reflection surface and the transmittance of a liquid crystal layer. It is an object of the present invention to provide a structure of a reflection type liquid crystal display device which can obtain the property.

[0008]

Means taken by the present invention to solve the above-mentioned problem is a reflection-type liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of opposing substrates. A light modulation filter is formed, and the light modulation filter has a light shielding surface configured to partially block at least visible light, and the light shielding surface is arranged to intersect with the surface of the substrate. It is characterized by becoming.

According to this means, the light incident or emitted in the direction intersecting the light-shielding surface is at least partially blocked by the light-shielding surface of the light modulation filter, but the light incident or emitted in the direction parallel to the light-shielding surface is not affected. Because it is not obstructed, it is possible to reduce the reflection of external light while suppressing the decrease in display brightness, and to prevent direct reflection of lighting and reflection of the background, thereby improving visibility. .

Here, it is preferable that the light modulation filter is formed of a light transmitting body including a light shielding layer forming the light shielding surface.

According to this means, since the light modulation filter is constituted by the light transmitting body including the light shielding layer,
Deterioration and damage of the light shielding layer can be prevented.

Further, the light modulation filter is formed of a light transmitting body having a periodic surface uneven structure, and the light shielding surface is
It is preferable to be provided on a surface part constituting a part of the surface uneven structure.

According to this means, since the light-shielding layer is formed on the surface portion of the surface uneven structure formed on the light transmitting body, the light modulation filter can be easily formed.

In this case, the surface uneven structure of the light transmitting body may be formed on either the incident side surface or the opposite side surface of the light transmitting body.

In each of the above means, it is desirable that the liquid crystal layer is a composite liquid crystal layer of a polymer dispersion type.

According to this means, by forming the polymer dispersed composite liquid crystal layer, the display can be performed without using a polarizing plate, so that the display can be brightened. Since visibility of external light in the light transmitting state of the liquid crystal layer can be prevented, visibility can be greatly improved.

In this case, it is particularly desirable that the light-shielding surface has a black color.

According to this means, since the light-shielding surface is black, the display in the light transmitting state of the liquid crystal layer can be blackened, so that the display contrast can be enhanced.

[0019]

Next, an embodiment according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is an enlarged view showing an internal structure of a liquid crystal display of a reflection type liquid crystal display device according to the present invention, and the illustrated range shows a sectional structure in a single pixel region. .

A transparent electrode 1 made of ITO (indium tin oxide) or the like is provided on the inner surface of the glass substrate 10 on the light incident side.
An alignment film 12 is coated on the surface of the transparent electrode 11 and rubbed in a predetermined direction.

On the other hand, a reflective electrode layer 2 made of a metal film such as aluminum or chromium is formed on the inner surface of the glass substrate 20 facing the glass substrate 10 by sputtering or vapor deposition.
1 is formed. On the surface of the reflective electrode layer 21, an alignment film 22 similar to the above-described alignment film 12 is formed.

The glass substrate 10 and the glass substrate 20 as described above are pressure-bonded via a sealing material (not shown), and a predetermined gap is formed between the substrates using a known spacer or the like. Then, the liquid crystal layer 30 is injected into this gap.
As the liquid crystal layer 30, various known liquid crystals can be injected. In the present embodiment, a polymer dispersed composite liquid crystal layer is used as the liquid crystal layer 30. This composite liquid crystal layer
For example, a solution in which a photocurable polymer monomer and a predetermined liquid crystal are mixed and infused is injected between the substrates, and then irradiated with light through the substrate to photopolymerize the polymer monomer, thereby polymerizing the polymerized polymer. It can be formed by dispersing particles in a liquid crystal. The polymer particles and liquid crystal molecules thus formed are normally aligned together in the rubbing direction of the alignment film when no electric field is applied.

In the polymer-dispersed composite liquid crystal layer, since the liquid crystal molecules have dielectric anisotropy and refractive index anisotropy, the refractive index of the polymer particles and the refractive index of the liquid crystal molecules are different. The display state is changed by making use of the fact that the values become substantially equal or different values depending on whether or not an electric field is applied. For example, when no electric field is applied, the aligned polymer particles and liquid crystal molecules are set to have substantially the same refractive index with respect to light entering and exiting in a direction perpendicular to the substrate surface. When the liquid crystal molecules change their orientation in the direction of the electric field, if the polymer particles and the liquid crystal molecules are set to have different refractive indexes, the liquid crystal layer will be in a light transmitting state when no electric field is applied, and will be in a light transmitting state when an electric field is applied. Is in a light scattering state.

In this embodiment, a light modulation filter 40 having a structure in which a light modulation layer 42 is sandwiched between transparent sheets 41 and 43 made of polycarbonate on the outer surface of a glass substrate 10.
Is attached. In the light modulating layer 42 of the light modulating filter 40, a number of light shielding layers 44 made of black resin that absorb visible light are arranged at equal intervals in a direction substantially perpendicular to the lamination surface or at a certain angle from the perpendicular direction. It is sealed in a transparent resin so as to have a slightly inclined direction.

As the black resin constituting the light shielding layer 44,
Various known black resins can be used. For example, a resin obtained by mixing carbon black with polycarbonate can be used. Various known transparent resins can be used as the transparent resin that seals the light shielding layer 44. For example, polycarbonate can be used.

The light-shielding layer 44 is set substantially parallel to a preset user's line of sight in a display device in which the above-described liquid crystal display is incorporated. In the present embodiment, it is assumed that the light-shielding layer 44 is used for a portable personal computer, a word processor, or the like, and the light-shielding layer 44 is formed to be inclined by about 18 degrees with respect to a direction perpendicular to the surface of the glass substrate. .

FIG. 2 shows the liquid crystal layer 3 in the above embodiment.
0 indicates the light traveling state when the light is in the light transmitting state. When the liquid crystal layer 30 is in a light transmitting state, external light incident from above the glass substrate 10 in the figure is transmitted through the liquid crystal layer 30 and reflected on the surface of the reflective electrode layer 21 and returns to the front surface side as it is. . However, in the present embodiment, the external light X incident from a direction different from the user's line of sight is shielded to some extent by the light shielding layer 44 of the light modulation filter 40, and does not reach the user's eyes.

On the other hand, light Y incident from substantially the same direction as the user's line of sight is not shielded by the light shielding layer 44, but is transmitted through the light modulation filter 40, further transmitted through the glass substrate 10 and the liquid crystal layer 30, and reflected. Although the incident light Y parallel to the light shielding layer 44 is reflected by the electrode layer 21, the incident light Y is inclined with respect to the reflection electrode layer 21. Only light is reflected back into the liquid crystal display.

In this light transmitting state, depending on the inclination angle and the formation interval of the light-shielding layer 44, the user generally recognizes a considerable proportion of the light reflected by the light-shielding layer 44 at the time of incidence or emission. Therefore, the color tone of the display visually recognized by the user substantially matches the color tone of the light shielding layer 44. In particular, when the color tone of the light shielding layer 44 is black as in the present embodiment, the display surface looks entirely black.

FIG. 3 shows a state in which light travels when the liquid crystal layer 30 is in a light scattering state, contrary to the above. In this state, the liquid crystal layer 30 looks cloudy due to the difference in the refractive index between the polymer particles and the liquid crystal molecules. At this time, the user visually recognizes the light scattered by the liquid crystal layer 30 from the incident external light, and the display looks white.

In the present embodiment, in particular, when the liquid crystal layer 30 is in a light transmitting state, the direct reflection of external light and the reflection of the background are prevented, so that the visibility is improved as a whole and the light shielding layer 44 is improved. Is black, the display is entirely blackened, so that the display contrast can be improved.

The angle of inclination of the light-shielding layer 44 is preset according to the relationship between the liquid crystal display and the direction of the user's line of sight, depending on the equipment on which the liquid crystal display is installed, the manner of use, and the like.
That is, the light shielding layer 44 is arranged in parallel with the main line of sight of the user. Therefore, if the main viewing direction of the user is a direction orthogonal to the surface of the glass substrate, the light-shielding layer 44 is also formed in an orthogonal posture without an inclination angle. The light-shielding layer may be configured to be adjustable to an appropriate inclination angle by a connection mechanism similar to a blind.

In the above embodiment, the case where the light-shielding layer 44 is inclined with respect to the direction perpendicular to the glass substrate is described, but the main line of sight of the user is in the direction perpendicular to the surface of the glass substrate. Therefore, when the light-shielding layer 44 is formed in parallel to the direction orthogonal to the glass substrate, the following is obtained. When the liquid crystal layer is in a light transmitting state, light incident from substantially the same direction as the user's line of sight,
Without being blocked by the light-blocking layer 44, it enters the liquid crystal display body as it is, is reflected by the reflective electrode layer 21, and is emitted again without being blocked by the light-blocking layer 44. The deviated light is often blocked by the light shielding layer 44 at the time of incidence or emission, and is hardly incident or emitted. Therefore, also in this case, since the reflection of external light is reduced, the visibility of the display can be improved, and the display when the liquid crystal layer is in the light transmitting state is blackened, and the contrast of the display is reduced. Can be improved.

In the above embodiment, the light-shielding layer 44 is described as completely blocking visible light and reflecting only light of a predetermined color tone.
Almost the same effect can be obtained even with a device mainly configured to transmit only light of a predetermined color tone. In this case, light absorption by the light-shielding layer 44 can be reduced, and a considerably thin sheet-like material can be formed as the light-shielding layer 44, so that the brightness of the display itself can be ensured, and the visibility is improved. Can be further improved.

The light modulation filter 40 includes a light shielding layer 44
Is contained in the inside, so that there is an advantage that the light-shielding layer 44 is hardly deformed or damaged, and has high durability.

FIG. 4 is an enlarged view showing the structure of a light modulation filter according to another embodiment of the present invention. In this embodiment, a light modulation filter 50 made of a transparent material such as an acrylic resin is adhered on the surface of a glass substrate 10 of a liquid crystal display similar to the above embodiment.

The light modulation filter 50 has a periodic surface uneven structure having a mountain-shaped cross section, and the surface uneven structure is substantially parallel to or slightly inclined from the direction orthogonal to the surface of the glass substrate 10. The one surface portion 50a and the second surface portion 50b connected to the first surface portion are alternately arranged in a predetermined direction on the display surface. On the surface of the first surface portion 50a, a thin light shielding layer 51 is formed by coating a black resin or the like. This light shielding layer 51
Is substantially the same as the above-described light-shielding layer 44, does not transmit visible light and emits reflected light of a predetermined color tone, but mainly transmits only light of a predetermined color tone. Is also good. Most preferably, the color is black.

Also in the embodiment having the light modulation filter 50, as shown in FIG. 5, the light shielding layer 51 has exactly the same operation as the light shielding layer 44 described above. Visibility can be improved and display contrast can be increased.

The light modulation filter 50 can easily form a surface uneven structure by resin molding and the like, and the light shielding layer 51 can be easily formed by coating, vapor deposition or other methods, so that it is relatively inexpensive. There is an advantage that it can be manufactured.

[0040]

As described above, according to the present invention, the following effects can be obtained.

That is, by using the means as in the present invention, the light incident or emitted in the direction intersecting with the light-shielding surface is at least partially blocked by the light-shielding surface of the light modulation filter. Light that enters or exits the screen is not blocked, so it is possible to reduce the reflection of external light while preventing the brightness of the display from decreasing, and to prevent direct reflection of lighting and reflection of the background. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a schematic structure of an embodiment of a reflection type liquid crystal display device according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a traveling state of light when the liquid crystal layer is in a light transmitting state in the embodiment.

FIG. 3 is an enlarged cross-sectional view showing a traveling state of light when the liquid crystal layer is in a light scattering state in the same embodiment.

FIG. 4 is an enlarged view showing a structure of a light modulation filter of another embodiment of the reflection type liquid crystal display device according to the present invention.

FIG. 5 is an enlarged cross-sectional view illustrating a traveling state of light in the embodiment shown in FIG.

[Explanation of symbols]

 10, 20 glass substrate 21 reflective electrode layer 40, 50 light modulation filter 41, 42 transparent sheet 44, 51 light shielding layer 50a first surface portion 50b second surface portion

Claims (5)

[Claims] 1. A reflection type liquid crystal display device having a liquid crystal layer sandwiched between a pair of opposing substrates, wherein a light modulation filter is formed on one of the substrates, and the light modulation filter partially filters at least visible light. A reflection type liquid crystal display device, wherein a light shielding surface is configured so as to intercept the light, and the light shielding surface is disposed so as to intersect the surface of the substrate. 2. The reflection type liquid crystal display device according to claim 1, wherein the light modulation filter is formed of a light transmitting body including a light shielding layer forming the light shielding surface. 3. The light modulation filter according to claim 1, wherein the light modulation filter is formed of a light transmitting body having a periodic surface unevenness structure, and the light shielding surface is provided on a surface portion forming a part of the surface unevenness structure. 1. A reflective liquid crystal display device comprising: 4. A reflection type liquid crystal display device according to claim 1, wherein said liquid crystal layer is a polymer dispersion type composite liquid crystal layer. 5. The reflection type liquid crystal display device according to claim 4, wherein the light shielding surface has a black color.