JP2000284267A - Liquid crystal display - Google Patents

Abstract

(57) [Problem] To provide a scattering type liquid crystal display device capable of brightening a bright display due to scattering of incident light and obtaining a sufficient contrast. A transparent film having a glossy surface is arranged on the back side of a scattering / transmission type liquid crystal cell, and a light absorbing layer is arranged on the back side of the transparent film to reduce incident light. The bright display due to scattering is obtained by irradiating light from the front of the scattered light incident from the front and scattered by the liquid crystal layer 15 of the liquid crystal cell 10 and the transparent film of the scattered light emitted to the back side of the liquid crystal cell 10. The light is reflected by the liquid crystal layer 20, is scattered again by the liquid crystal layer 15, and is emitted forward.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a scattering type liquid crystal display device for controlling and displaying light scattering.

[0002]

2. Description of the Related Art As a liquid crystal display device, there is a scattering type device which controls display of light by scattering.

FIG. 8 is a sectional view of a conventional scattering type liquid crystal display device.
And a light absorbing layer 9 disposed on the back side of the liquid crystal cell 1.

The scattering / transmission type liquid crystal cell 1 scatters and transmits incident light, and a pair of transparent substrates 2 and 3 on the front side and the back side joined via a frame-shaped sealing material (not shown). And transparent electrodes 4 and 5 provided on the inner surfaces of these substrates 2 and 3, respectively,
3 and a liquid crystal layer 6 that scatters and transmits incident light according to a change in the alignment state of liquid crystal molecules due to an electric field applied between the electrodes 4 and 5.

The scattering / transmission type liquid crystal cell 1 shown in FIG.
Is a polymer dispersed type, and the liquid crystal layer 6 is a liquid crystal / polymer composite layer. This liquid crystal / polymer composite layer is obtained by dispersing a nematic liquid crystal 8 having a positive dielectric anisotropy in a transparent polymer layer 7, and polymerized to have a sponge-like cross section. The liquid crystal 8 is confined in each of the gaps 7.

The liquid crystal cell 1 is of the active matrix type, and the electrodes 5 provided on the inner surface of the rear substrate 3 are a plurality of pixel electrodes arranged in a matrix. Each of the pixel electrodes 5 is provided with a plurality of TFTs (not shown) provided on the inner surface of the rear substrate 3 so as to correspond to the respective pixel electrodes 5.
The plurality of TFTs are connected to a gate line and a data line (not shown) wired on the inner surface of the rear substrate 3.

On the other hand, the electrode 4 provided on the inner surface of the front-side substrate 2 is a single-film-shaped counter electrode facing all of the plurality of pixel electrodes 5. Regions 5 and 5 are pixel regions.

The light absorbing layer 9 is of a black type that absorbs most of the incident light.
The liquid crystal cell 1 is disposed on the back side so as to face almost the entire surface of the liquid crystal cell 1. In the figure, the light absorbing layer 9
Is shown separated from the rear surface of the liquid crystal cell 1, but the light absorbing layer 9 is provided close to or in close contact with the outer surface of the rear substrate 3 of the liquid crystal cell 1.

This scattering type liquid crystal display device utilizes external light (natural light, room illumination light, etc.) which is light of the environment in which the liquid crystal of the scattering / transmission type liquid crystal cell (polymer dispersion type liquid crystal cell) 1 is used. The display is performed by controlling the scattering of light by the layer 6. The liquid crystal layer 6 scatters incident light to obtain a bright display, and transmits the incident light through the liquid crystal layer 6 to display a light absorbing layer on the back side. A dark display is obtained by absorption at 9.

That is, the molecules 8a of the liquid crystal 8 of the liquid crystal / polymer composite layer which is the liquid crystal layer 6 of the liquid crystal cell 1
In the no-electric-field state in which no voltage is applied between the five points, they are oriented in random directions as shown in FIG.

In this state of no electric field, light incident on the liquid crystal cell 1 from the front thereof is scattered by the scattering action of the liquid crystal layer 6 as shown by a solid arrow in the figure, and of the scattered light, The light directed toward the front is emitted forward, and the display in that area becomes bright. Note that, of the light scattered by the liquid crystal layer 6, the light going to the back side is the liquid crystal cell 1.
And is absorbed by the light absorbing layer 9.

Further, between the electrodes 4 and 5 of the liquid crystal cell 1,
When a voltage having a predetermined value is applied, the electric field causes the liquid crystal molecules 8a of the liquid crystal layer 6 to be uniformly arranged so as to be substantially perpendicular to the surfaces of the substrates 2 and 3.

At this time, the light incident on the liquid crystal cell 1 from the front thereof passes through the liquid crystal cell 1 almost without being scattered by the liquid crystal layer 6, as indicated by the dashed arrow in FIG. Is absorbed by the light absorbing layer 9, and the display in that region becomes a dark display.

Thus, the above-mentioned scattering type liquid crystal display device has
The scattering type liquid crystal display device does not require a polarizing plate for controlling light transmission unlike a TN (twisted nematic) type liquid crystal display device because it controls display of light scattering. A bright display can be obtained by using external light.

The scattering / transmission type liquid crystal cell 1 shown in FIG.
Is a polymer-dispersed type, but the scattering / transmission type liquid crystal cell has a liquid crystal layer composed of a cholesteric liquid crystal having a positive dielectric anisotropy or a mixed liquid crystal of a cholesteric liquid crystal and a nematic liquid crystal between a pair of transparent substrates. There is also a phase transition type (also called a phase transition type) provided.

This phase transition type liquid crystal cell scatters and transmits light by utilizing the phase transition of liquid crystal, and is a non-electric field state in which no voltage is applied between electrodes provided on inner surfaces of a pair of substrates. In the above, the liquid crystal exhibits a cholesteric liquid crystal phase and scatters incident light. In addition, when a predetermined voltage is applied between the electrodes, the liquid crystal transitions to a nematic liquid crystal phase in a homeotropic arrangement, and transmits incident light with almost no scattering.

A scattering type liquid crystal display device using the above-mentioned phase change type liquid crystal cell also has a structure in which a light absorbing layer is arranged on the back side of the above liquid crystal cell. The light is scattered to obtain a bright display, and the incident light is transmitted through the liquid crystal cell and absorbed by the light absorbing layer to obtain a dark display.

[0018]

However, in the conventional scattering type liquid crystal display device, the light is incident on the scattering / transmission type liquid crystal cell (polymer dispersion type or phase transition type liquid crystal cell) from the front surface thereof and is scattered by the liquid crystal layer. Of the scattered light, only light directed toward the front of the liquid crystal cell is emitted forward, and scattered light directed toward the back of the liquid crystal layer is emitted to the back of the liquid crystal cell and absorbed by the light absorbing layer. Brightness is not enough.

An object of the present invention is to provide a scattering type liquid crystal display device capable of brightening a bright display due to scattering of incident light and obtaining a sufficient contrast.

[0020]

According to a liquid crystal display device of the present invention, electrodes are provided on inner surfaces of a pair of substrates facing each other, and liquid crystal molecules are generated between the pair of substrates by an electric field applied between the electrodes. A scattering / transmission type liquid crystal cell provided with a liquid crystal layer that scatters and transmits incident light in accordance with a change in the alignment state of the liquid crystal cell; a transparent film having a glossy surface disposed on the back side of the liquid crystal cell; And a light absorbing layer disposed on the back side of the transparent film.

This liquid crystal display device uses external light, which is light of its use environment, to control the scattering of light by the liquid crystal layer of the scattering / transmission type liquid crystal cell, and displays the liquid crystal cell. When the liquid crystal molecules in the liquid crystal layer are in an alignment state that scatters incident light, external light incident on the liquid crystal cell from the front is scattered by the liquid crystal layer.

At this time, of the scattered light scattered by the liquid crystal layer, light heading toward the front of the liquid crystal cell is emitted forward, and a certain amount of scattered light emitted to the back of the liquid crystal cell is emitted. Light is reflected on the surface (glossy surface) of the transparent film, and the reflected light is incident on the liquid crystal cell from the back and is scattered again by the liquid crystal layer. Is emitted forward, and the display of the area becomes bright.

Note that, of the light emitted to the back of the liquid crystal cell, the light incident on the transparent film without being reflected on the surface of the transparent film passes through the transparent film and is absorbed by the light absorbing layer. .

That is, in the liquid crystal display device, a bright display due to the scattering of the incident light is transmitted from the front of the light scattered by the liquid crystal layer of the liquid crystal cell, which is incident from the front, and the light of the liquid crystal cell. The display is performed by the light that is reflected by the transparent film out of the scattered light emitted to the back side, is scattered again by the liquid crystal layer, and is emitted forward, and thus the brightness of the bright display is sufficient.

When the liquid crystal molecules of the liquid crystal layer of the liquid crystal cell are oriented so as to transmit the incident light, the light incident on the liquid crystal cell from the front is transmitted through the liquid crystal layer with almost no scattering, and the liquid crystal cell is not scattered. And the display in that area is dark.

However, even in the case of this dark display, of the light emitted to the back side of the liquid crystal cell, the light transmitted through the transparent film is absorbed by the light absorbing layer. Some of the emitted light is reflected by the transparent film, and the reflected light is transmitted through the liquid crystal cell and emitted forward, so that the dark display does not include the transparent film and the back of the liquid crystal cell It becomes brighter than when almost all the light emitted to the light absorbing layer is absorbed by the light absorbing layer.

However, the display of the liquid crystal display device is usually observed from the front direction (direction near the normal to the front surface of the liquid crystal cell), and external light is transmitted in the front direction, which is the display observation direction. The light is mainly incident from a direction inclined obliquely to it.

The surface of the transparent film is a glossy surface, and the light reflected on the surface of the transparent film is specularly reflected at the same reflection angle as the angle of incidence on the transparent film. The emission direction of the light reflected by the transparent film is obliquely forward with respect to the front direction,
That is, the direction is almost invisible to the display observer, so that the dark display observed from the front direction is sufficiently dark.

Therefore, according to the liquid crystal display device of the present invention, a bright display due to scattering of incident light can be made bright and a sufficient contrast can be obtained.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the liquid crystal display device of the present invention has a transparent film having a glossy surface on the back side of a scattering / transmission type liquid crystal cell, By arranging the light absorbing layer, the bright display due to the scattering of incident light is made bright, and a sufficient contrast can be obtained.

In the liquid crystal display device according to the present invention, when light is incident from a direction inclined by 5 ° with respect to a normal to the surface of the transparent film, 80 to 90 of the incident light is used.
Preferably, it has a property of transmitting 98% of light and regularly reflecting 2 to 20% of light. By using a transparent film having such properties, the bright display can be made sufficiently bright and sufficient contrast can be obtained. Can be obtained.

Further, in the liquid crystal display device of the present invention,
A plurality of the transparent films may be stacked and arranged. By arranging a plurality of the transparent films in this manner, the brightness of the bright display can be further improved.

Further, in the liquid crystal display device according to the present invention, between the transparent film and the light absorbing layer, incident light in a specific incident angle range which is incident from the front is transmitted.
An anisotropic reflection plate that reflects incident light from an oblique direction having a larger incident angle than that may be disposed. With such a configuration, the brightness of the bright display can be further improved. Further, the brightness of the bright display can be further improved by arranging a plurality of the transparent films as described above and arranging the directional reflector on the back side thereof.

In this case, a plurality of the anisotropic reflection plates may be stacked and arranged. In this way, by arranging the plurality of anisotropic reflection plates in a stacked manner, a brighter display can be further brightened. And the contrast can be further increased.

[0035]

FIG. 1 is a sectional view of a part of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device of this embodiment includes a scattering / transmission type liquid crystal cell 10 and a liquid crystal cell 1 of the present invention.
And a light absorbing layer 21 disposed on the back side of the transparent film 20.

The scattering / transmission type liquid crystal cell 10 scatters and transmits incident light, and a pair of front and back transparent substrates 11 and 12 joined via a frame-shaped sealing material (not shown). Transparent electrodes 1 on the inner surface of
3 and 14 are provided, and between the pair of substrates 11 and 12,
A liquid crystal layer 15 that scatters and transmits incident light according to a change in the alignment state of liquid crystal molecules due to an electric field applied between the electrodes 13 and 14 is provided.

The scattering / transmission type liquid crystal cell 10 used in this embodiment is of a polymer dispersion type, and its liquid crystal layer 1
5 is a liquid crystal / polymer composite layer. This liquid crystal / polymer composite layer is obtained by dispersing a nematic liquid crystal 17 having a positive dielectric anisotropy in a transparent polymer layer 16 and polymerized to have a sponge-like cross section. The liquid crystal 17 is confined in each of the gaps 16.

The liquid crystal cell 10 is of the active matrix type, and the electrodes 14 provided on the inner surface of the rear substrate 12 are a plurality of pixel electrodes arranged in a matrix. These pixel electrodes 14 are respectively
The TFTs are connected to a plurality of TFTs (thin film transistors) (not shown) provided on the inner surface of the rear substrate 12 so as to correspond to the respective pixel electrodes 14.
It is connected to a gate line and a data line (not shown) wired on the inner surface of the rear substrate 12.

On the other hand, the electrode 13 provided on the inner surface of the front-side substrate 11 is a single-film counter electrode facing all of the plurality of pixel electrodes 14. The areas facing each other are pixel areas.

Next, a description will be given of the transparent film 20 disposed on the back side of the scattering / transmission type liquid crystal cell 10. The transparent film 20 is a colorless transparent resin film having both glossy surfaces. is there.

FIG. 2 shows the optical characteristics of the transparent film 20. This transparent film 20 reflects a certain amount of incident light on a glossy surface as indicated by arrows in the figure. And has the property of transmitting other light.

Although FIG. 2 shows an example in which light is incident on the transparent film 20 from one surface thereof, the transparent film 20 has the same characteristics with respect to incident light from the other surface. Show.

The transparent film 20 used in this example is
When light is incident from a direction inclined by 5 ° with respect to the normal H of the surface, 80-98% of the incident light is transmitted and 2-20% of the light is specularly reflected. For example, as a transparent resin film having such optical characteristics, there is a PET (polyethylene terephthalate) film.

Although FIG. 1 shows the liquid crystal cell 10 and the transparent film 20 separated from each other, the transparent film 20 is provided on the rear substrate 1 of the liquid crystal cell 10.
2 is provided close to or in close contact with the outer surface.

The light absorbing layer 21 is of a black type that absorbs most of the incident light.
Is provided close to or in close contact with the back surface of the transparent film 20.

This liquid crystal display device uses external light, which is light in its use environment, and scatters light by the liquid crystal layer 15 of the scattering / transmission type liquid crystal cell (the polymer dispersion type liquid crystal cell in this embodiment) 10. The liquid crystal 1 of the liquid crystal / polymer composite layer, which is the liquid crystal layer 15 of the liquid crystal cell 10, is displayed.
In a no-electric-field state where no voltage is applied between the electrodes 13 and 14, the molecules 17 a of 7 are in an alignment state oriented in a random direction, that is, an alignment state in which incident light is scattered, as shown in FIG. .

As described above, when the liquid crystal molecules 17a of the liquid crystal layer 15 of the liquid crystal cell 10 are in an alignment state that scatters incident light, light incident on the liquid crystal cell 10 from the front is indicated by a solid line arrow in FIG. Is scattered by the scattering action of the liquid crystal layer 15.

At this time, of the scattered light scattered by the liquid crystal layer 15, light directed toward the front surface of the liquid crystal cell 10 is emitted forward, and of the scattered light emitted to the back surface of the liquid crystal cell 10. Is reflected on the surface (glossy surface) of the transparent film 20, the reflected light is incident on the liquid crystal cell 10 from the back side, is again scattered by the liquid crystal layer 15, and the liquid crystal of the scattered light is Light heading toward the front of the cell 10 is emitted forward, and the display in that area becomes bright.

Of the light emitted to the back of the liquid crystal cell 10, the light incident on the transparent film 20 without being reflected on the surface of the transparent film 20 passes through the transparent film 20 and passes through the light absorbing layer. 21 to be absorbed.

That is, in this liquid crystal display device, a bright display due to scattering of incident light is incident from the front and the liquid crystal cell 10 is illuminated.
Of the scattered light scattered by the liquid crystal layer 15 and the scattered light emitted to the back side of the liquid crystal cell 10 are reflected by the transparent film 20 and scattered again by the liquid crystal layer 15. The display is performed by the light that is emitted forward and thus, the brightness of the bright display is sufficient.

The electrodes 13 and 14 of the liquid crystal cell 10
When a voltage of a predetermined value is applied during this time, the electric field causes the liquid crystal molecules 17a of the liquid crystal layer 15 to be uniformly arranged so as to be substantially perpendicular to the surfaces of the substrates 11 and 12, and the alignment for transmitting the incident light. State.

As described above, when the liquid crystal molecules 17a of the liquid crystal layer 15 of the liquid crystal cell 10 are oriented so as to transmit the incident light, light incident on the liquid crystal cell 10 from the front is indicated by a broken arrow in FIG. Then, the light passes through the liquid crystal layer 15 with almost no scattering and exits to the back side of the liquid crystal cell, and the display in that region becomes a dark display.

However, even during the dark display, the liquid crystal cell 1
0 of the light emitted to the rear side of the transparent film 20
Is transmitted through the light absorbing layer 21, but some of the light emitted to the back side of the liquid crystal cell 10 is reflected by the transparent film 20, and the reflected light passes through the liquid crystal cell 10. Since the light is transmitted and emitted forward, the dark display becomes brighter than when the light absorbing layer 21 absorbs most of the light emitted to the back of the liquid crystal cell without the transparent film 20.

However, the display of the liquid crystal display device is usually observed from the front direction (the direction near the normal to the front surface of the liquid crystal cell 20), and the external light is reflected in the front direction, which is the display observation direction. Mainly from a direction obliquely inclined with respect to.

The surface of the transparent film 20 is a glossy surface, and the light reflected on the surface of the transparent film 20 is specularly reflected at the same reflection angle as the incident angle on the transparent film 20. When the transparent film 2
The emission direction of the light reflected by 0 is obliquely forward with respect to the front direction, that is, a direction that is hardly seen by a display observation observer, and therefore, a dark display observed from the front direction is sufficiently dark. is there.

Therefore, according to this liquid crystal display device,
It is possible to brighten a bright display due to scattering of incident light and to obtain a sufficient contrast.

In this liquid crystal display device, as described above, when light is incident from a direction inclined by 5 ° with respect to the normal H of the surface, the transparent film 20 has 80% of the incident light. It is preferable that the film has a property of transmitting up to 98% of light and regularly reflecting 2 to 20% of light. By using the transparent film 20 having such a property, the bright display can be made sufficiently bright, and A sufficient contrast can be obtained.

The transparent film 20 has a transmittance of 80% and a reflectance of 2% when light is incident from a direction inclined at 5 ° to the normal H of the surface. Comparing the display characteristics of the liquid crystal display device of the above embodiment with the conventional scattering type liquid crystal display device in which a light absorbing layer is arranged on the back side of the scattering / transmission type liquid crystal cell, both liquid crystal display devices have the same scattering / transmission characteristics. When a polymer-dispersed liquid crystal cell having transmission characteristics is used, the light reflectance (ratio of outgoing light to incident light) and contrast in bright display and dark display of a liquid crystal display device are as follows, respectively.

The display characteristics are such that light is incident on the liquid crystal display device at an incident angle of 30 ° with respect to the normal from the entire circumferential direction centered on the normal of the front surface of the liquid crystal display. Is a characteristic when measured from the front direction. The reflectance is based on the reflectance of a single white reflector made of Al ₂ O ₃ (alumina), and the reflectance of the white reflector is 100%. Value.

[Conventional Liquid Crystal Display Device] Bright display: reflectance = 10.9% Dark display: reflectance = 2.7% Contrast = 4.0 [Liquid crystal display device of the embodiment] Bright display: reflectance = 16 0.4% Dark display: reflectance = 4.1% Contrast = 4.0 Thus, the liquid crystal display device of the above embodiment is a conventional liquid crystal in which the light absorption layer is arranged on the back side of the scattering / transmission type liquid crystal cell. A bright display about 1.5 times brighter than the display device can be obtained.

In the liquid crystal display device of the above embodiment, the dark display is brighter than that of the conventional liquid crystal display device, but the ratio is about 1.5 times. High contrast is obtained.

In the first embodiment, one transparent film 20 is disposed between the scattering / transmission type liquid crystal cell 10 and the light absorbing layer 21, but the transparent film 20 having a glossy surface is used. A plurality of films 20 may be stacked and arranged. By arranging a plurality of transparent films 20 in such a manner, the brightness and contrast of the bright display can be further improved.

The display characteristics of a liquid crystal display device in which two transparent films 20 are stacked and a liquid crystal display device in which three transparent films 20 are stacked are as follows. In addition, this characteristic also has a transmittance of 8 when light enters the transparent film 20 from a direction inclined by 5 ° with respect to the normal H of the surface.
A liquid crystal display device having a characteristic of 0% and a reflectance of 2% is used. The liquid crystal display device emits light at an incident angle of 30 ° with respect to the normal from the entire circumferential direction around the normal on the front surface of the liquid crystal display. Is the characteristic when the emitted light is measured from the front direction,
The reflectance is based on the reflectance of a single white reflector made of Al ₂ O ₃ , and the reflectance of this white reflector is 1
The value is set to 00%.

[Two transparent films] Bright display: reflectance = 20.7% Dark display: reflectance = 5.3% Contrast = 3.9 [three transparent films] Bright display: reflectance = 25.0% Dark display: reflectivity = 6.8% Contrast = 3.7 As described above, the liquid crystal display device in which a plurality of the transparent films 20 are stacked and arranged has a single transparent film 20 (bright display reflection). Ratio = 16.4%, reflectance of dark display =
4.1%, contrast = 4.0), the brightness of the bright display is about 1.26 times when the number of the transparent films 20 is two, and when the number of the transparent films 20 is three. The contrast is about 1.52 times, and the contrast is a sufficient value, which is only slightly inferior to that of a single transparent film 20.

FIG. 3 is a sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention. In the liquid crystal display device of this embodiment, one sheet is provided on the back side of the scattering / transmission type liquid crystal cell 10. Along with disposing the transparent film 20, between the transparent film 20 and the light absorbing layer 21 disposed on the back side thereof,
One directional reflection plate 22 is arranged.

The scattering / transmission type liquid crystal cell 10 is of a polymer dispersion type, and the liquid crystal cell 10, the transparent film 20 and the light absorbing layer 21 are the same as those in the first embodiment. Therefore, the overlapping description is given the same reference numeral in the figure and omitted.

For example, as shown in the drawing, the directional reflection plate 22 has a plurality of minute prism portions 22a having a substantially triangular or similar cross-sectional shape on the front surface opposite to the back surface of the transparent film 20. The liquid crystal cell 10 is formed by closely arranging a plurality of pixel regions (regions in which the plurality of pixel electrodes 14 and the opposing electrodes 13 are opposed to each other) at a pitch sufficiently smaller than the pitch of the plurality of pixel regions. Are formed in a straight line or concentric shape parallel to each other, or in a pyramid shape or a conical shape and arranged in a matrix.

FIG. 4 shows the optical characteristics of the directional reflector 22. The directional reflector 22 has a front surface (a surface on which the prism portion 22a is formed) as indicated by an arrow in the drawing. Of the light incident from the front, a specific incident angle range incident from near the front direction, that is, the direction perpendicular to the back surface (flat surface) of the directional reflection plate 22 (the direction indicated by the dashed line in the figure). It has a characteristic of transmitting incident light of θ and reflecting incident light from an oblique direction having a larger incident angle.

The incident angle range θ of the incident light from the front direction passing through the directional reflector 22 and the reflection direction of the light incident from an oblique direction at a larger incident angle are determined by the material of the directional reflector 22. In this embodiment, the plurality of prism portions 22a are formed in a straight line along the horizontal axis of the screen, and the material of the directional reflector 22 and the prism portions are different. 2
The light incident on the cross-sectional shape of 2a at an incident angle of θ = about 30 ° (a range inclined about 15 ° in the vertical direction of the screen with respect to the vertical direction) is transmitted, and the incident light larger than that Light incident at an angle is selected to be reflected in a direction of a reflection angle substantially equal to the angle of incidence.

Although FIG. 3 shows the liquid crystal cell 10 and the transparent film 20 and the directional reflector 22 and the light absorbing layer 21 apart from each other, they are provided close to or in close contact with each other. I have.

The liquid crystal display of this embodiment has a transparent film 20 disposed on the back side of the scattering / transmission type liquid crystal cell 10.
And the light absorbing layer 21 disposed on the back side thereof, the incident light of a specific incident angle range θ incident from the front direction is transmitted, and the incident light from an oblique direction having a larger incident angle is transmitted. Since the reflective anisotropic reflection plate 22 is disposed, the brightness of the bright display is further improved as compared with the liquid crystal display device of the first embodiment (having one transparent film 20). And the contrast can be improved.

That is, in the liquid crystal display device of this embodiment, the light enters the liquid crystal cell 10 from the front during bright display, and is scattered by the scattering action of the liquid crystal layer 15 as shown by the solid line arrow in FIG. Among the scattered light, light directed toward the front surface of the liquid crystal cell 10 is emitted forward, and
0 of the scattered light emitted to the back surface of the transparent film 2
The light reflected on the surface (glossy surface) of the liquid crystal cell 10 is again scattered by the liquid crystal layer 15, and of the scattered light, light directed toward the front surface of the liquid crystal cell 10 is emitted forward, and further, the back surface of the liquid crystal cell 10. Out of the scattered light transmitted through the transparent film 20 and entering the anisotropic reflection plate 22 obliquely at an incident angle larger than the specific incident angle range θ. The light reflected by the reflection plate 22 and transmitted through the transparent film 20 and incident on the liquid crystal cell 10 from the back surface of the reflected light is again scattered by the liquid crystal layer 15, and Light heading toward the front of 10 exits forward.

Of the scattered light transmitted through the transparent film 20, light incident on the anisotropic reflection plate 22 from the front at an incident angle in the specific incident angle range θ is the anisotropic reflection plate 22. The light passes through the reflection plate 22 and is absorbed by the light absorption layer 21.

That is, the liquid crystal display device of this embodiment is
The bright display due to the scattering of the incident light is divided into the light that is incident from the front and is emitted out of the scattered light scattered by the liquid crystal layer 15 of the liquid crystal cell 10 and the scattered light that is emitted to the back side of the liquid crystal cell 10 The light reflected by the transparent film 20 and scattered again by the liquid crystal layer 15 and emitted forward, and the light reflected by the anisotropic reflector 22 and scattered again by the liquid crystal layer 15 and emitted forward. The display is performed by light, and thus the brightness of the bright display is much brighter than that of the liquid crystal display device of the first embodiment having one transparent film 20.

In the liquid crystal display device of this embodiment, even during dark display, of the light emitted to the back side of the liquid crystal cell 10, the light is transmitted through the transparent film 20 and further transmitted through the directional reflector 22. The absorbed light is absorbed by the light absorbing layer 21, but as shown by the dashed arrow in FIG.
0 is reflected by the transparent film 20 and is incident on the liquid crystal cell 10 from the rear side, and the directional reflection of the light transmitted through the transparent film 20 is reflected by the transparent film 20. Light incident obliquely to the plate 22 is reflected by the directional reflection plate 22, and of the reflected light, the light transmitted through the transparent film 20 is incident on the liquid crystal cell 10 from the back thereof, and The dark display becomes brighter than the liquid crystal display device of the first embodiment having one transparent film 20.

However, as described above, external light mainly enters from a direction obliquely inclined with respect to the front direction, which is the viewing direction of the display, and the light incident on the liquid crystal cell 10 during dark display. Since the light is transmitted through the liquid crystal layer 15 with almost no scattering, the direction of the light reflected by the transparent film 20 and emitted forward in the dark display is obliquely forward with respect to the front direction. Reflective plate 22
In order to reflect the light incident from the oblique direction toward the reflection angle direction substantially the same as the incident angle, the emission direction of the light reflected by the transparent film 20 and emitted forward in the dark display is also in the front direction. On the other hand, it is diagonally forward. Therefore, the dark display observed from the front direction is sufficiently dark.

The display characteristics of the liquid crystal display of this embodiment are as follows. Note that this characteristic is the same as that of the transparent film 2 described above.
In addition to the directional reflection plate, a light-emitting element having a characteristic of having a transmittance of 80% and a reflectance of 2% when light is incident from a direction inclined by 5 ° with respect to the normal H of the surface is used. 22
In this case, light incident at an incident angle in the angle range of θ = about 30 ° from the front direction is transmitted, and light incident at an incident angle larger than that is reflected toward the same reflection angle direction as the incident angle. Using a liquid crystal display device, light is incident on the liquid crystal display device at an incident angle of 30 ° with respect to the normal from the entire circumferential direction around the normal of the front surface of the liquid crystal display device. It is a characteristic when measured, and the reflectance is Al ₂
The value is based on the reflectance of a single white reflector made of O ₃ as a reference, and the reflectance of this white reflector is 100%.

Bright display: reflectance = 28.2% Dark display: reflectance = 5.6% Contrast = 5.0 As described above, the liquid crystal display device of this embodiment has one transparent film 20. Liquid crystal display device of the first embodiment (reflectance of bright display = 16.4%, reflectance of dark display = 4.1)
%, Contrast = 4.0), the brightness of the bright display is about 1.7 times, and the contrast is higher than that of the first display.
Is higher than that of the embodiment.

The liquid crystal display of the second embodiment has one transparent film 20, and one directional reflector 22 is disposed between the transparent film 20 and the light absorbing layer 21. However, if a plurality of the transparent films 20 are stacked and arranged, the brightness of the bright display can be further improved.

FIG. 5 is a sectional view of a part of a liquid crystal display device according to a third embodiment of the present invention. In the liquid crystal display device of this embodiment, two sheets are provided on the back side of the scattering / transmission type liquid crystal cell 10. The transparent film 20 is laminated and arranged, and one directional reflector 22 is arranged between the transparent film 20 and the light absorbing layer 21 on the back side.

The display characteristics of the liquid crystal display device of this embodiment are as follows. Note that this characteristic is such that when light is incident on the two transparent films 20 from a direction inclined by 5 ° with respect to the normal H of the surfaces, the transmittance is 80% and the reflectance is 2%.
%, The light incident on the directional reflector 22 at an incident angle in the angle range of θ = about 30 ° from the front direction, and the light incident at an incident angle larger than that. Is reflected in the direction of the reflection angle which is substantially the same as the incident angle, and the liquid crystal display device is provided with an angle of 30 ° with respect to the normal from all directions around the circumference centered on the normal to the front surface. This is a characteristic when light is incident at an incident angle of ° and the emitted light is measured from the front direction.
The value is based on the reflectance of a single white reflector made of l ₂ O ₃ as a reference, and the reflectance of this white reflector is 100%.

Bright display: reflectivity = 33.2% Dark display: reflectivity = 7.3% Contrast = 4.6 Thus, the liquid crystal display device of this embodiment has one transparent film 20 and one transparent film. The liquid crystal display device of the second embodiment (reflectance for bright display = 28.2)
%, Reflectivity of dark display = 5.6%, contrast = 5.
0), the brightness of the bright display is about 1.18 times,
Also, the contrast is sufficient, at 4.6.

The liquid crystal display device of the third embodiment has two transparent films 20 and one directional reflector 22.
However, if three or more transparent films 20 are stacked and arranged, the bright display can be further brightened.

FIG. 6 is a sectional view of a part of a liquid crystal display device according to a fourth embodiment of the present invention. The liquid crystal display device of this embodiment has two sheets on the back side of a scattering / transmission type liquid crystal cell 10. The transparent film 20 is laminated and arranged, and two directional reflectors 22 are laminated and arranged between the transparent film 20 and the light absorbing layer 21 on the back side.

According to the liquid crystal display device of this embodiment, since the transparent film 20 and the directional reflector 22 are each laminated and disposed two by two, the two transparent films 2
The bright display can be made brighter and the contrast can be made higher than that of the liquid crystal display device of the third embodiment having zero and one directional reflection plate 22.

The liquid crystal display device of this embodiment has two transparent films 20 and two directional reflectors 22, and three or more directional reflectors 22 are laminated. By arranging them, it is possible to further increase the brightness of the bright display and to increase the contrast, and when three or more transparent films 20 are laminated and arranged, the bright display can be further brightened.

FIG. 7 is a sectional view of a part of a liquid crystal display device according to a fifth embodiment of the present invention. In the liquid crystal display device of this embodiment, an anti-glare film 23 is provided on the front surface of a scattering / transmission type liquid crystal cell 10. It is provided.

In this embodiment, two transparent films 20 are laminated on the back side of the liquid crystal cell 10, and the transparent film 20 and the light absorbing layer 21 on the back side are arranged.
The configuration is the same as that of the third embodiment shown in FIG. 5 except that an anti-glare film 23 is provided on the front surface of the liquid crystal cell 10. Is the same.

The anti-glare film 23 is, for example, a light-diffusing transparent resin film whose surface is very slightly roughened.
It has a diffusion characteristic that the diffusion effect on light reflected by the zero and the directional reflection plate 22 and emitted forward is small.

The display characteristics of the liquid crystal display device of this embodiment are as follows. Note that this characteristic is such that when light is incident on the two transparent films 20 from a direction inclined by 5 ° with respect to the normal H of the surfaces, the transmittance is 80% and the reflectance is 2%.
%, The light incident on the directional reflector 22 at an incident angle in the angle range of θ = about 30 ° from the front direction, and the light incident at an incident angle larger than that. Is reflected in the direction of the reflection angle which is substantially the same as the incident angle, and the liquid crystal display device is provided with 30 This is a characteristic when light is incident at an incident angle of ° and the emitted light is measured from the front direction.
The value is based on the reflectance of a single white reflector made of l ₂ O ₃ as a reference, and the reflectance of this white reflector is 100%.

Bright display: reflectivity = 34.6% Dark display: reflectivity = 7.5% Contrast = 4.6 Thus, the liquid crystal display device of this embodiment is a liquid crystal cell 1
The liquid crystal display device of the third embodiment shown in FIG. 5 in which the anti-glare film 23 is not provided
3.6%, reflectivity of dark display = 7.3%, contrast =
Compared with 4.6), the brightness of the bright display is further increased, and a sufficient contrast equivalent to that of the liquid crystal display device of the third embodiment can be obtained.

Further, in this embodiment, since the anti-glare film 23 is provided on the front surface of the liquid crystal cell 10, glare on the screen due to surface reflection of external light on the front surface of the liquid crystal cell 10 is eliminated, and the transparent film It is possible to suppress glare in dark display due to the glossy surface of the surface 20.

The liquid crystal display device of this embodiment is similar to that of FIG.
The anti-glare film 23 is added to the liquid crystal display device of the third embodiment shown in FIG.
May be provided in any of the liquid crystal display devices of the above-described first to fourth embodiments.

The liquid crystal display of each of the embodiments described above displays a black-and-white image.
0, a plurality of color filters corresponding to each pixel region, for example, red, green,
By providing three color filters of blue, a multicolor image such as a full-color image can be displayed.

However, if the liquid crystal cell 10 is provided with a color filter, the transmitted light absorbs light in the absorption wavelength band by the color filter and becomes colored light.
The light emission rate is lower than that without the color filter.

Therefore, when the liquid crystal cell 10 is provided with a color filter, it is preferable to provide the color filter on the inner surface of the rear substrate 12. Of the scattered light scattered by the liquid crystal layer 15 of the liquid crystal cell 10, the uncolored light emitted forward and the color of the color filter are colored and emitted to the back side of the liquid crystal cell 10, and the transparent film 20 or The display is performed by both the scattered light reflected by the transparent film 20 and the directional reflection plate 22 and scattered again by the liquid crystal layer 15 and emitted forward, and a bright full-color image can be displayed.

In addition, the scattering / transmission type liquid crystal cell 10 comprises:
The liquid crystal layer is not limited to the polymer dispersion type, and may be a phase transition type in which a liquid crystal layer made of a cholesteric liquid crystal having a positive dielectric anisotropy or a mixed liquid crystal of a cholesteric liquid crystal and a nematic liquid crystal is provided between a pair of transparent substrates.

Further, the scattering / transmission type liquid crystal cell 10
Is not limited to the active matrix type, but may be a simple matrix type, and in the case of a black and white display liquid crystal display device, a segment type may be used.

[0099]

According to the liquid crystal display device of the present invention, a transparent film having a glossy surface is arranged on the back side of a scattering / transmission type liquid crystal cell, and a light absorbing layer is arranged on the back side of the transparent film. Therefore, bright display due to scattering of incident light can be made bright, and a sufficient contrast can be obtained.

In the liquid crystal display device of the present invention, when light is incident from a direction inclined by 5 ° with respect to the normal to the surface of the transparent film, 80 to 90 of the incident light is used.
Preferably, it has a property of transmitting 98% of light and regularly reflecting 2 to 20% of light. By using a transparent film having such properties, the bright display can be made sufficiently bright and sufficient contrast can be obtained. Can be obtained.

In the liquid crystal display of the present invention,
A plurality of the transparent films may be stacked and arranged. By arranging a plurality of the transparent films in this manner, the brightness of the bright display can be further improved.

Further, in the liquid crystal display device according to the present invention, between the transparent film and the light absorbing layer, incident light of a specific incident angle range which is incident from the front is transmitted.
An anisotropic reflection plate that reflects incident light from an oblique direction having a larger incident angle than that may be disposed. With such a configuration, the brightness of the bright display can be further improved. Further, the brightness of the bright display can be further improved by arranging a plurality of the transparent films as described above and arranging the directional reflector on the back side thereof.

In this case, a plurality of the anisotropic reflection plates may be stacked and arranged. In this way, by arranging the plurality of anisotropic reflection plates in a stacked manner, a bright display can be further brightened. And the contrast can be further increased.

Having a reflection axis and a transmission axis orthogonal to each other,
A p-s-wave separating reflector that reflects s-wave light of a polarization component along the reflection axis and transmits p-wave light of a polarization component along the transmission axis is disposed. Since the light absorbing member is provided on the side, bright display due to scattering of incident light can be made sufficiently bright, and a display with good contrast can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a part of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a view showing optical characteristics of a transparent film.

FIG. 3 is a sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating optical characteristics of a directional reflector.

FIG. 5 is a cross-sectional view of a part of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a part of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a part of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 8 is a cross-sectional view of a part of a conventional scattering type liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Scattering / transmission type liquid crystal cell (polymer dispersion type liquid crystal cell) 11, 12 ... Substrate 13, 14 ... Electrode 15 ... Liquid crystal layer (liquid crystal / polymer composite layer) 20 ... Transparent film 21 ... Light absorption layer 22 ... Direction Reflective plate 22 ... Anti-glare film

Claims (5)

[Claims] An electrode is provided on an inner surface of a pair of substrates opposed to each other, and incident light is scattered between the pair of substrates in accordance with a change in an alignment state of liquid crystal molecules due to an electric field applied between the electrodes. And a scattering / transmission type liquid crystal cell provided with a liquid crystal layer to be transmitted, a transparent film having a glossy surface disposed on the back side of the liquid crystal cell, and a light absorbing layer disposed on the back side of the transparent film. A liquid crystal display device comprising: 2. The transparent film transmits 80% to 98% of the incident light when light is incident from a direction inclined at 5 ° to the normal to the surface of the transparent film. 20%
The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a characteristic of regularly reflecting light. 3. The liquid crystal display device according to claim 1, wherein a plurality of the transparent films are arranged in a stacked manner. 4. An incident light of a specific incident angle range incident from the front direction is transmitted between the transparent film and the light absorbing layer, and the incident light from an oblique direction having a larger incident angle is reflected. The liquid crystal display device according to claim 1, wherein an anisotropic reflection plate is disposed. 5. The liquid crystal display device according to claim 4, wherein a plurality of anisotropic reflection plates are stacked.