JPH1152411A - Reflection type liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display element capable of making bright white display and well expressing the brightness and darkness of the colors exclusive of white even with the display light exclusive of the white. SOLUTION: A dichroic mirror 4 which reflects the light of a specific wavelength and allows the transmission of the light exclusive of a specific wavelength is arranged between a transparent substrate 2 and a reflection plate 3. A first phase transition type guest-host liquid crystal layer 6 contg. dichromatic dyestuffs 5 is disposed between this transparent substrate 2 and the dichroic mirror 4. A second phase transition type guest-host liquid crystal layer 8 contg. the dichromatic dyestuffs 7 is disposed between a reflection plate 3 and the dichroic mirror 4. The first phase transition type guest-host liquid crystal layer 6 and the second phase transition type guest-host liquid crystal layer 8 are so constituted that the transmission and scattering of the light in these liquid crystal layers are respectively independently controlled by individual impression of voltages thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device which enables a particularly bright white display.

[0002]

2. Description of the Related Art A liquid crystal display device such as a liquid crystal color display has excellent features such as light weight and thinness.
Currently, it is widely used as a display for AV equipment such as small cameras, video cameras, and digital cameras, and OA equipment such as word processors and personal computers. However, in the conventional liquid crystal display device, there is a problem to be improved such that a backlight is required because light use efficiency is as low as several percent and power consumption is increased. In response to such a problem, a reflective liquid crystal display device using natural light has been proposed and put to practical use. Among such reflection type liquid crystal display devices, in particular, a type using a color filter (CF) and a type using an ECB (electric field control birefringence) type are known as those for color display.

[0003]

By the way, the above-mentioned color filter system expresses a color to be displayed by absorbing light of a color other than the color to be displayed. According to the color filter system, for example, when an additive color mixture system of R (red), G (green), and B (blue) is used, color reproduction is performed with three pixels, so that it is in principle equivalent to printed matter. I can't get the brightness.

In the case of the ECB (Electric Field Controlled Birefringence) system, by controlling the voltage applied to the liquid crystal layer,
The color displayed by each pixel can be changed to white, orange, blue, green, and red. So, with this method,
Even in the case of white display, since light passes through the polarizing plate, about 1/2 of the incident light is lost, and there is a complaint that a sufficiently bright white display cannot be performed. further,
In the ECB (Electric Field Controlled Birefringence) method, the transmittance (reflectance) is low because the light passes through the polarizing plate, and the display becomes dark, and the brightness of each color cannot be sufficiently expressed. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable bright white display and to express the brightness of a color of display light other than white well. An object of the present invention is to provide a reflection type liquid crystal display device.

[0006]

In a reflection type liquid crystal display device according to the present invention, a dichroic mirror between a transparent substrate and a reflection plate reflects light in a specific wavelength range and transmits light outside the specific wavelength range. Is disposed between the transparent substrate and the dichroic mirror, and a first phase change type guest-host liquid crystal layer containing a dichroic dye is provided. A second phase-transition guest-host liquid crystal layer containing a reactive dye, and the first phase-transition guest-host liquid crystal layer and the second phase-transition guest-host liquid crystal layer are individually provided with a voltage. Is applied to control the transmission and scattering of light in these liquid crystal layers independently of each other.

According to this reflection type liquid crystal display device, the first phase change type guest-host liquid crystal layer is provided between the transparent substrate and the dichroic mirror, and the second phase change type is provided between the reflection plate and the dichroic mirror. Type guest-host liquid crystal layer, and the first phase-change type guest-host liquid crystal layer and the second
Of the phase-transition type guest-host liquid crystal layer
Since the scattering is controlled independently of each other, the brightness of light reflected by the dichroic mirror by the first phase change type guest-host liquid crystal layer can be continuously expressed. By changing the degree of absorption of light transmitted through the dichroic mirror by the phase-change guest-host liquid crystal layer of No. 2, it is possible to continuously express, for example, the brightness of Red (red) in one pixel, White display is also possible.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a reflection type liquid crystal display device of the present invention will be described in detail. FIG. 1 is a view showing one embodiment of a reflection type liquid crystal display device of the present invention. In FIG. 1, reference numeral 1 denotes a reflection type liquid crystal display device. This reflective liquid crystal display element 1
A dichroic mirror 4 is provided between the transparent substrate 2 and a reflecting plate 3 provided on a counter substrate (not shown), and a first dichroic dye 5 containing a dichroic dye 5 is provided between the transparent substrate 2 and the dichroic mirror 4. Transition type guest-host liquid crystal layer 6
Is provided between the reflection plate 3 and the dichroic mirror 4.
This is provided with a second phase change type guest-host liquid crystal layer 8 containing a dichroic dye 7.

The transparent substrate 2 is made of a transparent base material such as glass and is arranged on the light incident side, and its inner surface (the surface on the dichroic mirror 4 side) is made of a transparent conductive film such as ITO. A transparent electrode 9 and an alignment film (not shown) made of polyimide or the like and subjected to an alignment process such as rubbing are formed and arranged in this order. In this example, the reflection plate 3 is formed by forming a conductive material such as aluminum (Al) or silver (Ag) on the counter substrate, and the reflection plate 3 itself is the second phase change type guest-type. It functions as an electrode for controlling the behavior of the host liquid crystal layer 8. An alignment film (not shown) made of polyimide or the like and having been subjected to an alignment process such as rubbing is also formed on the inner surface (the surface on the dichroic mirror 4 side) of the reflection plate 3.

The dichroic mirror 4 has a structure in which a film that reflects light in a specific wavelength range and transmits light other than the specific wavelength range is formed on a transparent plate.
The color reproduction is performed by an additive mixture of R (red), G (green), and B (blue). That is, in this example, a red reflection dichroic film (not shown) that reflects light in the red light wavelength region and transmits light in other wavelength regions (that is, the green light wavelength region and the blue light wavelength region). A green reflective dichroic film (not shown) that reflects light in the green light wavelength range and transmits light in other wavelength ranges (that is, red light wavelength range and blue light wavelength range); And a blue reflecting dichroic film (not shown) that reflects light in the wavelength region of the above and transmits light in the other wavelength regions (that is, the wavelength region of the red light and the wavelength region of the green light). It is formed by forming a film and patterning it regularly for each pixel. Further, the dichroic mirror 4 has transparent electrodes 10 and 11 formed on both surfaces thereof, respectively, and further covers these to form an alignment film made of polyimide or the like and subjected to an alignment treatment such as rubbing (not shown). ) Is formed and arranged.

A first phase transition type guest-host liquid crystal layer 6,
The second phase-transition type guest-host liquid crystal layer 8 is mainly composed of a P-type liquid crystal that is twisted between the upper and lower substrates during the initial alignment in this example, and a dichroic dye is formed in the P-type liquid crystal so as to be almost black. 5 (7) is mixed and dispersed. With such a configuration, the first and second phase transition type guest-host liquid crystal layers 6 (8) are formed between the electrodes sandwiching them, that is, the transparent electrode 9 of the transparent substrate 2 and the transparent electrode 10 of the dichroic mirror 4. , Or between the transparent electrode 11 of the dichroic mirror 4 and the reflector 3 serving as an electrode, a voltage is individually applied, whereby light is transmitted through these phase-transition type guest-host liquid crystal layers 6, 8.・
The scattering is controlled independently of each other.

The first and second phase-transition type guest-host liquid crystal layers 6 (8) are provided with a dichroic dye molecule 5 (7) and a dichroic dye molecule 5 (7) simultaneously with a liquid crystal by applying a voltage. By arranging the mirror 4 and the reflecting plate 3) so as to be gradually vertical, light is easily transmitted, and the absorbance thereof gradually decreases.

Next, the operation of the reflection type liquid crystal display element 1 having such a configuration will be described. In this example, the dichroic film of the dichroic mirror 4 is a green reflective dichroic film, and the P-type liquid crystal of the first and second phase-transition type guest-host liquid crystal layers 6 (8) changes the initial alignment to the homogeneous alignment. We use what we did.

The reflection type liquid crystal display element 1 uses states 1 to 3 shown in FIG. 2, that is, dark green display (state 1), bright green display (state 2), and white display (state 3).
Each case will be described. First, state 1
With regard to the above, the voltage application to the second phase transition type guest-host liquid crystal layer 8 is turned off, and the second phase transition type guest-host liquid crystal layer 8 is set to a scattering mode, that is, a mode in which light is maximally absorbed. This suppresses the red light and the blue light transmitted through the dichroic mirror 4 from being reflected by the reflection plate 3 and transmitted through the dichroic mirror 4 again and leaking to the transparent substrate 2 side. Then, the voltage application to the first phase transition type guest-host liquid crystal layer 6 is turned off or suppressed to a low voltage, whereby the first phase transition type guest-host liquid crystal layer 6 is turned off.
Is also set to the scattering mode, whereby the absorption of green light that enters the dichroic mirror 4 and is reflected there and emitted to the transparent substrate 2 side is increased, whereby dark green display is performed.

In the state 2, as in the case of the state 1, the voltage application to the second phase-change type guest-host liquid crystal layer 8 is turned off and the second phase-change type guest-host liquid crystal layer 8 is turned off.
Is set to the scattering mode, so that the dichroic mirror 4
The red light and the blue light transmitted through are reflected by the reflection plate 3 and transmitted through the dichroic mirror 4 again to suppress leakage to the transparent substrate 2 side. Then, the first phase transition type guest-host liquid crystal layer 6 is turned on by applying a voltage to the first phase transition type guest-host liquid crystal layer 6, thereby entering the dichroic mirror 4. Further, the absorption of the green light reflected here and emitted to the transparent substrate 2 side is reduced, whereby a bright green display is performed.

In the state 3, the voltage application to the second phase change type guest-host liquid crystal layer 8 is turned on so that the red light and the blue light transmitted through the dichroic mirror 4 are reflected by the reflector 3 to the maximum. I do. Then, the first phase transition type guest-host liquid crystal layer 6 is turned on by applying a voltage to the first phase transition type guest-host liquid crystal layer 6, thereby entering the dichroic mirror 4. Furthermore, the absorption of green light reflected here and emitted to the transparent substrate 2 side is reduced, and the absorption of red light and blue light reflected by the reflection plate 3 and transmitted through the dichroic mirror 4 is also reduced. Display it.

As described above, in the reflection type liquid crystal display element 1 of this embodiment, the first phase change type guest-host liquid crystal layer 6 is used without passing through the polarizing plate and thus without loss of light. The brightness of the light reflected by the dichroic mirror 4 can be continuously expressed, and the degree of absorption of the light transmitted through the dichroic mirror 4 by the second phase transition type guest-host liquid crystal layer 8 is changed. , One pixel can continuously represent light and dark such as Green (green). Therefore, unlike the conventional color filter system, it is possible to satisfactorily display a desired color at a brightness similar to that of a printed matter. Further, since light does not pass through the polarizing plate, there is almost no loss of light, and therefore, very bright white display can be realized.

In the above embodiment, the reflecting plate 3 is used as an electrode as it is. However, when the reflecting plate 3 is made uneven to obtain a scattering effect, the transparent electrode is separated from the reflecting plate 3. Thus, it may be provided on the inner surface side of the reflection plate 3.

[0019]

As described above, in the reflection type liquid crystal display device of the present invention, the first phase change type guest-host liquid crystal layer is provided between the transparent substrate and the dichroic mirror, and the reflection plate and the dichroic mirror are connected to each other. In between the second phase transition type guest
A host liquid crystal layer is provided, and the first phase transition type guest-host liquid crystal layer and the second phase transition type guest-host liquid crystal layer are configured such that transmission and scattering of light thereof are independently controlled. Therefore, the brightness of the light reflected by the dichroic mirror can be continuously expressed by the first phase transition type guest-host liquid crystal layer.
By changing the degree of absorption of light transmitted through the dichroic mirror by the phase-transition type guest-host liquid crystal layer, light and dark such as Red (red) can be continuously expressed by one pixel. Therefore, unlike the conventional color filter system, it is possible to satisfactorily display a desired color at a brightness similar to that of a printed matter. Further, since light does not pass through a polarizing plate as in the conventional ECB system, there is almost no loss of light, and therefore, very bright white display can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a diagram showing an operation state of the liquid crystal display element shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reflection type liquid crystal display element, 2 ... Transparent substrate, 3 ... Reflector,
4 ... dichroic mirror, 5, 7 ... dichroic dye, 6 ...
First phase change type guest-host liquid crystal layer, 8... Second phase change type guest-host liquid crystal layer

Claims (1)

[Claims] 1. A dichroic mirror that reflects light in a specific wavelength range and transmits light in a wavelength other than the specific wavelength range is disposed between a transparent substrate and a reflecting plate, and between the transparent substrate and the dichroic mirror. A first phase change type guest-host liquid crystal layer containing a dichroic dye is provided, and a second phase change type guest-host containing a dichroic dye is provided between the reflector and the dichroic mirror. A liquid crystal layer is provided. The first phase-change type guest-host liquid crystal layer and the second phase-change type guest-host liquid crystal layer are individually applied with a voltage to transmit light through these liquid crystal layers. -A reflective liquid crystal display device characterized in that scattering is independently controlled.