JPH0829811A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which is excellently formed to have a smaller thickness and weight, high in utilization efficiency of light, consumes less electric power and enables enhancement of luminance and contrast by laminating a polymer dispersion type liquid crystal layer and a guest-host type liquid crystal layer. CONSTITUTION:A first substrate 3 and a second substrate 5 are arranged to face each other in such a manner that their respective GH-PDLC layer 4 and PDLC layer 11 face each other. Liquid crystal layers of a two-layered structure composed of the GH-PDLC layer 4 and the PDLC layer 11 are formed. The GH-PDLC layer 4 is formed by dispersing liquid crystal phases added with a dark color dye into TN liquid crystal having positive dielectric constant anisotropy into a polymer phase. The PDLC layer 11 is formed by dispersing the TN liquid crystals as PDLC in the state of the liquid crystal phases into the high polymer phase as it is without adding the dyes thereto. Driving voltages are impressed to such PDLC layer 11 and the GH-PDLC layer 4 to drive these two layers at one time. Then, the structure of the liquid crystal display panel and the structure of the driving respective are simplified and the driving electric power is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device that realizes good viewing angle characteristics, high contrast characteristics, and low power consumption.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used in word processors, personal computers, projection TVs, direct-view TVs.
It is often used for etc. Among them, a liquid crystal display device is generally used in which a polarizer is used in combination with a liquid crystal display cell to display an image by utilizing the polarization effect of a liquid crystal layer. Liquid crystal display devices using such nematic liquid crystals include TN (twisted nematic) liquid crystal display devices having a molecular arrangement twisted by 90 ° between cell gaps and STN (super twisted nematic) devices having a larger twist angle. Type liquid crystal display element.

A liquid crystal display device utilizing the polarization effect due to the twist of these liquid crystal molecules has a thin liquid crystal layer, exhibits a high response speed and high contrast characteristics, and can be driven at a low voltage. Or a numeric display board such as a calculator, or a display panel that forms an image on a plane such as an active matrix type having a simple matrix or a switching element for each pixel, and a color image is displayed by combining them with a color filter. It is used for LCD TVs.

However, in such a liquid crystal display device which uses a polarization effect due to the twisted molecular alignment of liquid crystals and a polarizer, a polarizing plate is generally used as the polarizer in view of its operation principle. Since at least 50% of the light from the light source is cut off by this polarizing plate, there is a large loss of light when passing through the polarizing plate. Therefore, since the light transmittance of the liquid crystal display panel is extremely low, there is a problem that an image observed on the screen is dark.

In order to obtain a bright display image in a liquid crystal display device utilizing the polarization effect due to the twist of the liquid crystal molecules, it is necessary to illuminate with a large-capacity bright light source (backlight). However, such a bright backlight has a problem of high power consumption. There is also a problem that the backlight body and the light guide plate become thick and large. Therefore, there is a problem that the inherent advantages of the liquid crystal display element, such as low power consumption and thin and lightweight characteristics, cannot be utilized.

Therefore, in recent years, attention has been paid to a reflective liquid crystal display device which does not require a backlight, and research and development thereof have been actively conducted. This is because the reflective liquid crystal display element does not require a backlight, and thus can have low power consumption and can be thin and compact.

However, such a conventional reflective liquid crystal display element has a lower light utilization efficiency than the transmissive liquid crystal display element due to a large light loss at the reflector. Further, since the reflective liquid crystal display element uses external light as a light source instead of the backlight, the brightness of the display image is determined by the external light. Therefore, when the liquid crystal display element is used or in a dark place, the display image at that time is extremely dark and difficult to see.

In particular, in the case of a reflective liquid crystal display device capable of displaying a color image, displaying a color image is, in other words, light is dispersed. -Approximately 1/3 when using G / B color filters, and approximately 2/3 when using Y / M / C color filters. The brightness per pixel is even lower than in black and white display. Become. Therefore, conventionally, it has been extremely difficult to put a reflective color liquid crystal display device into practical use.

On the other hand, as a technique for displaying a color image without using a combination of a nematic type liquid crystal display device having a polarizing plate and a color filter, a coloring effect of transmitted light due to birefringence of an STN type liquid crystal is utilized. A liquid crystal display device of the type that performs color display has been proposed. However, such a liquid crystal display device theoretically has a problem that the color reproducibility of a display image is poor.

As a proposal for the practical application of a reflection type color liquid crystal display device, in SID'92 (p437-), PCGH (Phase Change Guest Host Mod) proposed by Mitsui et al.
e; hereinafter, abbreviated as PCGH) type liquid crystal display device is known.

FIG. 6 shows an example of the structure of a reflection type color liquid crystal display element using a PCGH type liquid crystal. Glass substrate 601
A TFT substrate 605, on which a TFT 602, an interlayer insulating film 603, and a pixel electrode 604 formed of a transparent conductive film such as ITO are laminated in this order, and a color filter 607 and a transparent film such as ITO on a glass substrate 606. A counter substrate 609 in which a counter electrode 608 formed of a conductive film is laminated in this order, and a PCGH-type liquid crystal layer 610 sandwiched between the TFT substrate 605 and the counter substrate 609 so as to seal the periphery thereof Parts are formed.

The reflective color liquid crystal display device using the PCGH type liquid crystal layer 610 is a guest-host type liquid crystal (Guest-host liquid crystal) formed by mixing a nematic liquid crystal with a dye.
PCGH such as Host type liquid crystal; hereinafter abbreviated as GH type liquid crystal)
Type liquid crystal is used. The operating principle is PCGH
When the liquid crystal molecules of the type liquid crystal layer 610 lie horizontally, the dye molecules also lie along the posture (state) of the liquid crystal molecules, light is reflected by the dye molecules, and the color of the dye is observed. .
Then, when the liquid crystal molecules are vertically erected, light is transmitted and observed as a bright spot.

The PCGH type liquid crystal display device utilizing such a change in the orientation of the liquid crystal molecules does not need a polarizing plate, so that there is no loss of transmitted light in the polarizing plate and the light transmittance is high. Therefore, it should be possible to obtain a bright display image.

However, actually, in a reflection type liquid crystal display element which displays a color image by using the PCGH type liquid crystal layer 610 and the color filter 607, the incident light and the emitted light pass through the color filter 607 twice in total. It will be. At this time, light is absorbed at the square of the light absorptance of the transparent substrate in the transmissive liquid crystal display device. As a result, there is a problem in that the image of the liquid crystal display element viewed from the front side has low brightness and low contrast characteristics.

JAPAN DISPLA is a technique intended to solve the problems of the PCGH type liquid crystal display device.
In Y'92 (page 707), Ikeno et al. Proposed a reflective color liquid crystal display device using two liquid crystal display panels, a polymer dispersion (hereinafter abbreviated as PDLC) type liquid crystal display element and a PCGH type liquid crystal display element. ing. FIG. 7 shows an outline of the structure of a reflective color liquid crystal display device using the PDLC type liquid crystal display element and the PCGH type liquid crystal display element.

A PDLC type liquid crystal display element 702 is arranged on a PCGH type liquid crystal display element 701 using a black dye. The PCGH type liquid crystal display element 701 is composed of two glass substrates 703 and 704 which are opposed to each other with a gap.
A PCGH-type liquid crystal layer 705 is sandwiched and sandwiched in the gap of. A reflection plate 706 is arranged on the lower glass substrate 703 in the figure.

The PDLC type liquid crystal display element 702 is composed of two glass substrates 707 and 708 which face each other with a gap.
A PD type liquid crystal layer 709 is sandwiched and sandwiched in the gap of. In this case, the screen is PDLC type liquid crystal display element 7.
Observed from the 02 side.

External light enters the PDLC type liquid crystal display element 702 from above in the figure.

At this time, the PDLC type liquid crystal display element 702
In the transmissive mode, the incident light passes through the PDLC type liquid crystal display element 702 and further enters the PCGH type liquid crystal display element 701.

When the PCGH type liquid crystal display element 701 is in the transmissive mode, the incident light that has passed through the liquid crystal display element 702 passes through the PCGH type liquid crystal display element 701 and the reflection plate 7.
It is reflected at 06. At this time, in the case of the structure in which the color filter is mounted on the reflection plate 706, the reflected light is light colored by the color filter. The reflected light travels in the opposite direction to the PCGH type liquid crystal display element 701, PD.
The light is transmitted through the LC type liquid crystal display element 702 in this order, is emitted to the upper observation side in the figure, and is observed as a coloring point colored by the color of the color filter.

When the PCGH type liquid crystal display element 701 is in the non-transmissive mode, the incident light transmitted through the liquid crystal display element 702 is reflected by the dark color dye in the PCGH type liquid crystal layer 705 to cause the PDLC type liquid crystal display element 702 to pass through. It passes through and is emitted upward in the figure, and is colored in a dark color with a dye and observed as a dark spot.

When the PDLC type liquid crystal display element 702 is in the diffusion mode, the incident light is diffused by the PDLC type liquid crystal display element 702. At this time, since the scattered light is emitted as scattered light having various directional components in the upper part of the figure, as an image, the white turbidity having an appropriate widening of the viewing angle is similar to the light reflected by the diffuse reflector. Are observed as bright spots.

A liquid crystal display device in which two liquid crystal display panels as described above are stacked and each liquid crystal display panel is driven is
The contrast ratio is higher than that of the above-mentioned PCGH type liquid crystal display device, and there is an advantage that a bright image display can be obtained.

However, in actuality, when light passes through the glass substrates adjacent to each other of the two liquid crystal display panels, parallax occurs due to the refraction of the light by the thickness of the glass substrates. This parallax significantly deteriorates the display image quality as the pixel size of one pixel with respect to the thickness of the glass substrate becomes finer. In recent years, in general, in liquid crystal display devices in which higher definition and larger screens are progressing, the ratio of pixel size to the thickness of the glass substrate is becoming finer, so this parallax is more remarkable in image quality. It causes a decrease. As described above, the above technique has a problem that the quality of the display image is deteriorated due to the parallax.

Moreover, compared with the conventional liquid crystal display device using one liquid crystal display panel, the structure of the liquid crystal display element becomes twice as complicated because two liquid crystal display panels are used together. As a result, the manufacturing cost is increased.
In addition, the drive circuit system for separately driving the two liquid crystal display panels is more complicated than before, and the power consumption for driving the drive circuit and the liquid crystal and the power loss of the drive circuit system are increased. There is a problem of bringing.

[0026]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and its purpose is to make the device thin and lightweight, to have high light utilization efficiency and low consumption. It is an object of the present invention to provide a reflective liquid crystal display element that can display an image with high power and high brightness and high contrast.

[0027]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention has a first electrode substrate having a first electrode provided on a substrate and a second electrode substrate provided on the substrate. A second electrode substrate, in which an electrode is disposed and opposed to the first electrode with a gap, and a gap between the first electrode substrate and the second electrode substrate are surrounded by a circumference. A polymer-dispersed liquid crystal layer, in which a nematic liquid crystal phase is dispersed in a capsule state in a polymer phase, and a guest-host liquid crystal layer in which a dye is added to a nematic liquid crystal composition are laminated. And a liquid crystal drive circuit for driving the liquid crystal layer by applying a liquid crystal drive voltage to the first electrode and the second electrode.

Further, a first electrode substrate having a first electrode provided on the substrate and a second electrode provided on the substrate and having a gap with respect to the first electrode. A nematic liquid crystal phase is encapsulated in a polymer phase, which is sandwiched by a second electrode substrate arranged to face each other and a gap between the first electrode substrate and the second electrode substrate with the periphery sealed. A polymer-dispersed liquid crystal layer having a dispersed configuration and a polymer-dispersed liquid crystal layer having a guest-host liquid crystal phase in which a dye is added to a nematic liquid crystal composition dispersed in a capsule state in a polymer phase are laminated. And a liquid crystal layer which is formed.

In the above liquid crystal display device, of the first electrode substrate and the second electrode substrate, on the main surface of the substrate on the rear surface side facing the liquid crystal layer when viewed from the screen observation direction. It is characterized in that it is provided with a color filter arranged at.

In any one of the above liquid crystal display devices, the guest-host type liquid crystal layer or the guest-host type liquid crystal phase among the liquid crystal layers laminated in two layers is dispersed in a polymer phase in a capsule form. The polymer-dispersed liquid crystal layer is formed on the front side of the polymer-dispersed liquid crystal layer when viewed from the screen observation direction. In any one of the above liquid crystal display devices, the diffuse reflection of a surface material that diffuses and reflects light, which is disposed on the main surface of the back side substrate facing the liquid crystal layer when viewed from the screen observation direction. It is characterized by having layers.

The first electrode and the second electrode are, for example, signal electrodes arranged so as to face each other so that one electrode is a scanning electrode and the other electrode intersects the scanning electrode with a gap. The present invention can be applied to a structure of a so-called simple matrix type liquid crystal display device.
Alternatively, each of the first electrode and the second electrode is a pixel electrode in which one electrode is provided for each pixel, and the other electrode is a counter electrode that faces the pixel electrode with a gap in common. The present invention can be applied to the structure of a so-called active matrix type liquid crystal display device as described above.

As the color filter, for example, a color filter of RGR 3 colors formed by, for example, a dyeing method, a pigment dispersion method, a printing method, an electrodeposition method, or the interference of light is used to decompose transmitted light. A dichroic filter or the like that colors by applying can be preferably used. Alternatively,
It goes without saying that the present invention can be applied to a liquid crystal display device that performs monochrome display without using a color filter. Even in the case of this black-and-white display, it is possible to realize image display with excellent brightness and contrast characteristics.

[0033]

According to the present invention, the PDLC layer and the GH-PDLC are
A driving voltage (applied voltage) is applied to the layer or the PCGH layer to drive those two layers at once. At this time, the state of each layer is changed according to the value of the drive voltage by controlling the value of the drive voltage. GH liquid crystal layer and PD
Since both the LC liquid crystal layer and the LC liquid crystal layer are sandwiched between a pair of electrodes that are arranged to face each other, the electrodes are, for example, a pair of electrodes such as a scanning electrode and a signal electrode, or a pixel electrode and a counter electrode, as in the conventional liquid crystal display panel. A pair of electrodes may be used. Therefore, the structure of the liquid crystal display panel and the structure of the drive circuit can be simplified as compared with the conventional liquid crystal display element in which two liquid crystal display panels are stacked. Further, the driving power can be reduced.

By adopting the structure including the liquid crystal layer formed by laminating the PDLC layer and the PCGH layer in this way, the liquid crystal display device of the present invention does not require a polarizing plate and By eliminating the problem of parallax caused by the glass substrate located between liquid crystal display panels in a conventional liquid crystal display device using two liquid crystal display panels, there is no deviation or bleeding of display for each pixel, and high resolution is achieved. It is possible to display an image with good quality and good contrast and brightness characteristics.

Further, a PCGH layer or a liquid crystal layer using a GH (guest host) liquid crystal composition is arranged on the front side as viewed from the observation side, and a color filter is arranged on the main surface of the rear side substrate which is in contact with the liquid crystal layer. By forming the substrate surface on the back side as the reflection main surface, it is possible to realize a reflection type liquid crystal display device capable of displaying an image with higher brightness and a higher contrast ratio. That is, at this time, by arranging a PCGH layer or a PDLC layer using a GH (guest host) liquid crystal composition on the front surface side, it functions as a shutter for incident light as light source light to the reflective liquid crystal display device, And, the PDLC layer on the back side of the PCGH layer or the light transmitted through the PDLC layer using the GH liquid crystal composition is observing the light emitted to the front side by emission of light (bright display) or in the liquid crystal layer. By controlling the absorption (intermediate gradation display) due to the diffusion of the light, it is possible to effectively and brightly display an image with high display quality by using the light from the light source with high efficiency.

[0036]

Embodiments of the liquid crystal display device of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view showing the structure of a liquid crystal display device according to a first embodiment of the present invention. A GH-PDLC layer 4 formed by dispersing a PCGH liquid crystal phase in a polymer phase is formed on the main surface of the transparent electrode 2 of the first substrate 3 having the transparent electrode 2 formed on the transparent substrate 1 on the front side. ing.

On the other hand, T is formed on the transparent substrate 6 of the second substrate 5.
A structural layer such as FT7 is formed, an uneven layer 8 having an uneven surface is formed so as to cover the structural layer, and a reflective electrode 9 having an uneven cross section is formed on the uneven layer 8 along the unevenness.
Further, a color filter (hereinafter abbreviated as CF) 10 is formed on the reflective electrode 9, and a PDLC layer 11 in which a nematic liquid crystal phase is dispersed in a polymer phase is further formed thereon.

Then, the first substrate 3 and the second substrate 5 are arranged so as to face each other so that the GH-PDLC layer 4 and the PDLC layer 11 face each other, and the GH-PDL is formed.
A liquid crystal layer 12 having a two-layer structure including a C layer 4 and a PDLC layer 11.
The liquid crystal display device according to the present invention in which is formed is formed. In this example, the liquid crystal composition used for the liquid crystal layer 12 includes the GH-PDLC layer 4 and the PDLC layer 1.
1 and both have positive dielectric anisotropy (dielectric anisotropy Δε> 0
) TN liquid crystal is used. The GH-PDLC layer 4 is a TN liquid crystal having a positive dielectric anisotropy in which a liquid crystal phase in which a dark dye is added is dispersed in a polymer phase.
The DLC layer 11 is a PDLC in which a TN liquid crystal is dispersed in the polymer phase in its liquid crystal phase without adding a dye.

The liquid crystal display device of the present invention is GH-PDLC.
Since the layer 4 and the PDLC layer 11 are laminated as a liquid crystal layer 12 in a pair of substrates with electrodes, they are simultaneously formed.
It is possible to drive two layers as one liquid crystal layer 12 with one applied voltage by one driving circuit. Further, since the reflection electrode 9 as a reflection plate is arranged inside the liquid crystal cell,
Since incident light related to display can be prevented from being lost by being reflected before passing through the transparent substrate 6 on the back side, the incident light can be effectively used as light source light with high utilization efficiency, and bright multicolor It is possible to display.

FIG. 2 shows the electro-optical characteristics of the PDLC layer 11 and the GH-PDLC layer 4 used in the liquid crystal display device of this embodiment. In addition, FIG. 3 is a diagram showing the optical path of the light relating to the display for each magnitude of the liquid crystal applied voltage in each case.

The liquid crystal display device of this embodiment is controlled in three states by three kinds of applied voltages of V1, V2 and V3 as shown in FIG. It is set to change the light intensity.

When the applied voltage is V1, the PDL
The C layer 11 is in a scattering state, while the GH-PDLC layer 4 is in a state of absorbing light by the dye.

When the applied voltage is V2, the PDLC layer 11 is in the scattering state and the GH-PDLC layer 4 is in the transmitting state.

When the applied voltage is V3, the PDLC layer 1
Both 1 and the GH-PDLC layer 4 are in a transmissive state.

Here, it is possible to realize multicolor display (multicolor display) by using CF. In this embodiment, the case of using CF of three colors of R, G and B will be described. For the sake of brevity, the following description will focus on the R pixel as a representative of the three colors R, G, and B described above.

When the applied voltage is V2, PDLC
Both the layers 11H are in the transmissive state. At this time, the incident light passes through the PDLC layer and the guest host layer, further passes through the CF, is reflected by the reflective electrode 9, and is emitted by tracing the same optical path as this in the opposite direction. Therefore, at V2, a red display is obtained.

When the applied voltage is V1, PD is applied as described above.
While the LC layer 11 is in a scattering state, the GH-PDLC layer 4
Absorbs light with dyes. Incident light is thus GH
-The PDLC layer 4 functions like a shutter and this GH-
Most of the light is absorbed by the PDLC layer 4, resulting in black display (FIG. 3A).

When the applied voltage is V2, the PDLC layer 11
Becomes a scattering state, and the GH-PDLC layer 4 becomes a transparent state. The incident light passes through the GH-PDLC layer 4 and the PDLC
Scattered by the layer 11, the scattered light is divided into forward scattered light and back scattered light, the back scattered light is emitted to the display surface, and the light is recognized as a clouded color. On the other hand, as for the forward scattered light, only the light of R wavelength is transmitted by the CF 10. The light that has passed through the CF 10 is reflected by the reflective electrode 9 and is again CF 10
The light that has passed through and is scattered by the PDLC layer 11 and is scattered is emitted to the display surface through the GH-PDLC phase 4 (FIG. 3B). Therefore, when the applied voltage is V2, the display color is the total display color of the backscattered light and the light reflected by the reflection electrode 9, that is, a mixed color of red and white (for example, pink or crimson is observed). Can be obtained.

When the applied voltage is V3, the PDLC
Both the layer 11 and the GH-PDLC layer 4 are in the transmissive state. At this time, incident light is emitted from the PDLC layer 11 and the GH-PDLC layer 4
Through the CF 10, is reflected by the reflective electrode 9, and is emitted by tracing the same optical path in reverse.
(C)). Therefore, at V3, a red display colored by CF10 is obtained.

Similar to the case of R described above, the same coloring effect of such a display occurs in each pixel of G and B colors. That is, when the applied voltage is V3, it is possible to obtain a high brightness display in which the G pixel is green and the B pixel is blue.
When the applied voltage is V2, a color of green and white is mixed in the G pixel (that is, lettuce color), and a color of blue and white is mixed in the B pixel (that is, light blue such as pastel blue). When the applied voltage is V1, black display in which the brightness is well suppressed is obtained for both G and B pixels. Also R, G, B
When the applied voltage is V3 for all pixels, a white display screen with high brightness can be obtained by combining the colored lights. The liquid crystal display device of the present invention is capable of multicolor display by combining various kinds of such color displays.

Further, by driving with any voltage in the middle between V1 and V2, halftone display or halftone display can be obtained. Alternatively, halftone display or the like can be realized by driving with a driving circuit (not shown) in combination with a frame thinning method or the like.

Although the reflective electrode 9 is used as the pixel electrode in the first embodiment, it goes without saying that the pixel electrode in the structure of the liquid crystal display device according to the present invention is not limited to this. Besides this, for example, CF
It goes without saying that the same effect as described above can be obtained by forming a transparent electrode on 10 and using it as a pixel electrode. It is also possible to use a conductive CF as the CF 10 and also use this conductive CF as a pixel electrode. Therefore, in this case, the pixel electrode is not necessary in addition to the conductive CF.

If the brightness (brightness) is more important than the tint of the display, a brighter display can be obtained by using CFs of three colors of Y (yellow), M (magenta) and C (cyan). can get. Alternatively, a brighter display can be obtained by using two colors of CF (for example, M and G), although the display colors are reduced.

The electro-optical characteristic described in this operation is P
The DLC layer has a higher threshold voltage, but GH-PDLC
Even if the electro-optical characteristics of the layer 4 and the PDLC layer 11 are opposite,
The same effect can be obtained.

It is needless to say that the same effect as that of the above-mentioned embodiment can be obtained even when the liquid crystal having the dielectric anisotropy Δε <0 is used.

Next, a method of manufacturing the liquid crystal display device of the first embodiment having the above structure will be described.

First, a method of forming the GH-PDLC layer 4 will be described. G with black dye added to TN liquid crystal and electro-optical properties of n _e = 1.5678, n _o = 1.4804, Δε = + 4.0
H-type liquid crystal material ZLI-4876 (manufactured by Merck Japan Co., Ltd.) is used as a PCGH liquid crystal phase. Meanwhile, the degree of polymerization is 500
An aqueous solution of PVA with a concentration of 25 wt% is prepared, and PN393 (manufactured by Merck Japan Ltd.) is used as a UV curable resin.
Mix at a ratio of 1: 1 and use this as the polymer phase.

The above PCGH liquid crystal phase and polymer phase are
Mix at a ratio of 0:32. At this time, the PCGH liquid crystal phase is insoluble in the polymer phase PVA. Therefore, an emulsion is formed by performing sufficient stirring. Ultrasonic agitation is performed for 10 minutes for more uniform agitation. 5 μ of the emulsion thus obtained on the first substrate 3 having the transparent electrode 2 made of ITO and having a thickness of 200 nm formed on the transparent substrate 1 made of alkali-free glass having a thickness of 0.7 mmt.
The GH-PDLC layer 4 having a layer thickness of 5 μm is obtained by applying it to a thickness of m by a printing method and drying it at 40 ° C. for 30 minutes. Since the GH-PDLC layer 4 is formed by the emulsion method, the liquid crystal is not dissolved and mixed in the polymer phase, and the ratio of PVA is as low as about 4 wt% of the whole, so the resistance of the polymer is low. It is possible to drive at a low voltage as compared with a polymer phase having a high ratio and a high PVA ratio. This GH-PD
The LC layer 4 is formed as a solid-like layer when viewed from the outside. Therefore, even if a liquid layer is adjacent to the GH-PDLC layer 4, it does not mix with the liquid layer.

On the other hand, the substrate 5 arranged to face the substrate 3
A PDLC layer 11 is formed on top. First, the TFT 7 is formed on a transparent substrate 6 such as a quartz substrate, an acrylic resin is formed on the transparent substrate 6 to a thickness of 2 μm, and the surface thereof is etched by plasma CVD of CF ₄ gas to roughen the surface. The unevenness is formed, and the acrylic resin layer is used as the unevenness layer 8. An Al thin film having a thickness of 200 nm is vapor-deposited on the concavo-convex layer 8 made of acrylic resin to form a reflective electrode 9 as a pixel electrode. The reflective electrode 9 was formed in a pixel size of 100 μm × 100 μm. On the reflective electrode 9 serving as the pixel electrode, a CF 10 in which M and G color cells are arranged is formed.

Then, the PDLC layer 11 is formed so as to cover the substrate 5 including the CF 10. Dielectric anisotropy is positive nematic liquid crystal _{TL- 205 (n e = 1.7445,} n o = 1.
5270, Δε = + 5.0; manufactured by BDH) is used as a liquid crystal phase, and PN 393 (n _p = 1.473) is used as a polymer phase.
This is mixed using a ratio of 80:20. At this time,
The liquid crystal phase is completely soluble in the polymer phase. Therefore, the mixture becomes a liquid. The liquid material of the PDLC layer 11 in a liquid state may be injected into the substrate gap from the injection port after the substrate 5 is disposed so as to face the substrate 3 with a substrate gap and the periphery is sealed. As a sealing material for sealing the periphery of the substrate, for example, UV-1000
Both substrates are superposed on each other by using (Sony Chemical), and the thickness of the sealing material is used as a substrate gap to bond the substrates with a gap. At this time, spacers having a particle size of 5.0 μm are dispersed to maintain the substrate gap. Then, the sealing material is irradiated with ultraviolet rays to be cured, and the liquid is injected into the PDL.
The C layer 11 is cured to obtain a liquid crystal display panel. A drive circuit (not shown) is connected to the liquid crystal display panel to complete the reflective liquid crystal display device according to the present invention.

By driving the liquid crystal display device of the first embodiment as described above, a total of four types of electro-optical characteristics (TV characteristics) of R, G, B single colors and white by combining all RGB are obtained. The display performance was confirmed by measuring the reflectance observed from the front.

First, when only R (red) pixels were driven and the liquid crystal applied voltage was gradually raised from 0 V, observation was carried out. At 0 V, the molecular arrangement of the liquid crystal phase of the GH-PDLC layer 4 was disordered. , The dyes are also randomly arranged. Therefore, most of the incident light is absorbed. The reflectance at this time is 5.0
% Was low.

At a liquid crystal applied voltage of 4 V, only the GH-PDLC layer 4 has a molecular alignment of liquid crystal phase in vertical alignment. The dye is also vertically aligned. The refractive index of the polymer of the GH-PDLC layer 4 is set to be substantially equal to n ₀ of the liquid crystal phase.
Therefore, in this state, the effective refractive indices of the liquid crystal phase and the polymer phase (polymer) are equal (that is, since the liquid crystal molecules in the liquid crystal phase are vertically aligned, the effective refractive index is n ₀ ), The GH-PDLC layer 4 completely transmits incident light.
Further, in the PDLC layer 11, the molecular alignment of the liquid crystal phase remains disordered at 4V as at 0V. Therefore, the incident light is scattered here. About 1/6 of the light scattered here is scattered backward. In other words, about 1/6 of the light is reflected. The light reflected here is white (since it does not pass through CF). The remaining about 5/6 of light passes through the R (red) color filter and is diffusely reflected by the reflective electrode 9 made of Al. These lights are colored and reflected by R and are displayed on the display surface side (observation side).
Will be emitted to. Since the R color filter absorbs the G and B wavelength components, the reflectance is reduced by that amount (that is, 2/3 of the incident light amount). Therefore, in total, 1/6
White light of about 5/6 and red light of about 5/6 x 1/3 were reflected, resulting in a slightly whitish red (pink) display.

Next, at a liquid crystal applied voltage of 4 V, although the color purity is slightly low, 1/6 of the whole light is reflected before passing through the color filter, so that an extremely high reflectance is obtained. This cannot be applied to color display with high color purity, but is extremely effective for milk-color display such as pink.

Further, in the case of white display (when all the R, G, and B pixels are set to 4V), 1/6 of the whole light is reflected before passing through the color filter, which is similar to the conventional technique. Inevitably, it becomes extremely bright compared to the method of transmitting the color filter. The reflectance at 4V (R only at 4V) was 16%.

When the voltage is further increased, the PDLC layers 11 gradually become vertically arranged at 4.5 V or more, and become completely vertically arranged at 8 V. Here, the GH-PDLC layer 4
Both the PDLC layer 11 and the PDLC layer 11 are in a state of directly transmitting the incident light. Therefore, there is no reflection in front of the color filter as in the case of 4 V, and most of the incident light passes through the color filter and is diffusely reflected by the reflecting electrode 9 made of Al. Therefore,
The reflectance is as low as 1/3 of the total, but since it passes through all color filters, color display with extremely high color purity can be obtained. The reflectance here was 10.5%.

Subsequently, when the applied voltage was gradually decreased from 8 V, the response operation of the display state to the applied voltage was the same as the above, although the order was reversed.

Further, when the applied voltage was suddenly changed from 0V → 8V → 0V, the same operation (response of the display state to the applied voltage) was obtained. It was found that gradation display is possible without hysteresis of electro-optical characteristics.

Next, all the R, G and B pixels are driven,
The display performance in white display was evaluated. Liquid crystal applied voltage 0
At V, the reflectance was 5% as in the case of a single color. 4V ~ 4.5
At V, in all pixels, the reflection at the PDLC layer 11 and the reflection at the reflection electrode 9 after passing through the color filter are obtained, and the reflectances of R, G, and B become equal as a whole, and white display is performed. It was Since 1/6 of the light is reflected in front of the color filter, there was no light loss due to passing through the color filter, resulting in a bright display. At this time, the reflectance was 31%. It has been found that there is no hysteresis in electro-optical characteristics and gradation display is possible. The driving voltage was as low as 8V.

Subsequently, the contrast ratio and the viewing angle characteristic of the contrast were measured at a liquid crystal applied voltage of 0V-4.0V. This is shown in FIG. The contrast ratio was as high as about 6: 1. In addition, the viewing angle with a contrast ratio of 2: 1 or more was as wide as ± 50 ° in all directions. This is achieved by using a disordered molecular arrangement of dyes in order to obtain a black display in the liquid crystal display device of the present invention. At this time, the screen brightness itself was high. This can increase the pixel aperture ratio to 80% by adopting a three-dimensional structure in which the structure of the scanning wiring, the signal wiring, the TFT 7 and the like is arranged under the reflective electrode 9 which is the pixel electrode in the structure of the TFT substrate. I was able to do it. In addition, since it is not necessary to use a light-shielding film that shields the semiconductor layer of the TFT 5, it is possible to eliminate the decrease in the opening area of the pixel portion due to the coating of the pixel portion with the light-shielding film.

Then, the response speed of the liquid crystal layer 12 was measured, and it was confirmed that the total of rising and falling was 100 ms, and that high-speed response performance was realized.

(Embodiment 2) In the liquid crystal display device of the second embodiment, the refractive index of the polymer phase of the GH-PDLC layer 4 shown in the liquid crystal display device of the first embodiment is 1
Different from the example, the liquid crystal phase was set to be equal to n _e .
Other than that, the liquid crystal display device of the second embodiment having the same dielectric constant anisotropy and the same structure as the first embodiment was manufactured. In this case, as the polymer phase, SAM 114 is used instead of the UV curable resin PN 393 in the liquid crystal display device of the first embodiment.
Was used to set the refractive index to n _p = 1.56. The other structure is the same as that of the first embodiment.

The liquid crystal display device of the second embodiment is different from the liquid crystal display device of the first embodiment in that the GH-PDLC layer 4 is an extraordinary light refraction type.
The behavior of the H-PDLC layer 4 is different.

That is, in the liquid crystal display device of the second embodiment, the effective refractive index of the liquid crystal phase (including the dye) of the GH-PDLC layer 4 when the liquid crystal applied voltage is 4 V is the same as that of the above liquid crystal composition. n ₀ = 1.48. On the other hand, since the refractive index of the polymer phase is n _p = 1.56 as described above, incident light is scattered at a high rate. That is, most of the incident light is backscattered and reflected. Accordingly, the display becomes brighter than that in the case of the liquid crystal display device of the first embodiment. At this time, GH-P
Needless to say, the DLC layer 4 and the PDLC layer 11 both provide reflection due to backscattering. The reflectance was about 41%. Thus, it was confirmed that the incident light can be used with extremely high efficiency.

However, here, the GH-PDLC layer 4 in the liquid crystal display device of the present embodiment changes the incident light to the liquid crystal applied voltage 0
Only one of the states of absorption at V or backscattering at a liquid crystal applied voltage of 4 V or more can be taken. In other words, since light cannot be simply transmitted, the liquid crystal display device of the first embodiment is better than the liquid crystal display device of the second embodiment in terms of displaying with high color purity of the display color. It has various characteristics.

In all other respects, like the liquid crystal display device of the first embodiment, an image of high display quality with good contrast characteristics and applied voltage-luminance characteristics (TV characteristics) is displayed. be able to. The TV characteristic is shown in FIG.

In each of the above embodiments, one of the two-layer structure forming the liquid crystal layer 12 is GH-
Although the PDLC layer and the other are PDLC layers, it goes without saying that the present invention is not limited to this. The GH-PDLC layer used in the above embodiments is not limited to the polymer dispersion liquid crystal as described above as long as it is a GH liquid crystal suitable for achieving a function like an optical shutter as in the above embodiments. Not limited. That is, the GH- used in the above embodiment
It goes without saying that a simple GH liquid crystal (PCGH liquid crystal) that does not use a polymer phase can be used instead of the PDLC layer. However, in that case, there is no light diffusion effect in the GH-PDLC layer in the above embodiment, and either the light absorption / transmission action in the GH liquid crystal is selectively used.

Further, in each of the above-mentioned embodiments, the reflection electrode made of Al having a function as a diffusion reflection plate having a high light reflectance on the surface is used as the pixel electrode. It is needless to say that the pixel electrodes made of a transparent conductive film may be stacked and provided as separate layers on the above.

[0080]

As described above in detail, according to the present invention, the device is thin and lightweight, the light utilization efficiency is high, the power consumption is low, and the brightness and contrast are high. A reflective liquid crystal display device capable of displaying an image can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display device according to a first embodiment.

FIG. 2 is a PDLC used in the liquid crystal display device of the first embodiment.
It is a figure which shows the electro-optical characteristic of the layer 11 and GH-PDLC layer 4.

FIG. 3 is a diagram showing an optical path of light relating to a display for each magnitude of a liquid crystal applied voltage of the liquid crystal display device of the liquid crystal display device of the first embodiment in each case.

FIG. 4 is a diagram illustrating a liquid crystal applied voltage 0 of the liquid crystal display device according to the first embodiment.
It is a figure which shows the viewing-angle characteristic of a contrast ratio and a contrast in V-4.0V.

FIG. 5 is a diagram showing a TV characteristic of the liquid crystal display device of the second embodiment.

FIG. 6 is a diagram showing an example of a structure of a reflective color liquid crystal display element using a conventional PCGH type liquid crystal.

FIG. 7 is a diagram showing an outline of a structure of a reflective color liquid crystal display device using a conventional PDLC type liquid crystal display element and a PCGH type liquid crystal display element.

[Explanation of symbols]

 1 ... Transparent substrate 2 ... Transparent electrode 3 ... First substrate 4 ... GH-PDLC layer 5 ... Second substrate 6 ... Transparent substrate 7 ... TFT 8 ... Uneven layer 9 ... Reflecting electrode 10 ... Color filter 11 ... PDLC layer 12 ... Liquid crystal layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Hato 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock company Toshiba Yokohama office

Claims (5)

[Claims] 1. A first electrode substrate having a first electrode provided on a substrate, and a second electrode provided on the substrate with a gap from the first electrode. A nematic liquid crystal phase is encapsulated in a polymer phase, which is sandwiched by a second electrode substrate arranged to face each other and a gap between the first electrode substrate and the second electrode substrate with the periphery sealed. A liquid crystal layer in which a polymer-dispersed liquid crystal layer that is dispersedly arranged and a guest-host liquid crystal layer in which a dye is added to a nematic liquid crystal composition are stacked, and liquid crystal driving is performed on the first electrode and the second electrode. A liquid crystal display device comprising: a liquid crystal drive circuit that drives a liquid crystal layer by applying a voltage. 2. A first electrode substrate having a first electrode provided on a substrate, and a second electrode provided on the substrate and having a gap with respect to the first electrode. A nematic liquid crystal phase is encapsulated in a polymer phase, which is sandwiched by a second electrode substrate arranged to face each other and a gap between the first electrode substrate and the second electrode substrate with the periphery sealed. A polymer-dispersed liquid crystal layer having a dispersed configuration and a polymer-dispersed liquid crystal layer having a guest-host liquid crystal phase in which a dye is added to a nematic liquid crystal composition dispersed in a capsule state in a polymer phase are laminated. Liquid crystal display device comprising: 3. The liquid crystal display device according to claim 1, wherein, of the first electrode substrate and the second electrode substrate,
A liquid crystal display device comprising a color filter arranged on a main surface of a substrate on the back surface side facing the liquid crystal layer when viewed from the screen observation direction. 4. Claims 1 and 2 and 3
In the liquid crystal display device according to any one of the above items, the guest-host type liquid crystal layer or the guest-host type liquid crystal phase among the liquid crystal layers laminated in the two layers is dispersed in a polymer phase in a capsule form. The polymer dispersed liquid crystal layer
A liquid crystal display device, wherein the liquid crystal display device is arranged on the front side of the polymer-dispersed liquid crystal layer when viewed from the screen observation direction. 5. Claims 1, 2 and 3
5. The liquid crystal display device according to claim 4, wherein a surface material that diffuses and reflects light is disposed on a main surface of the substrate on the back surface side facing the liquid crystal layer when viewed from the screen observation direction. A liquid crystal display device comprising a diffuse reflection layer.