JPH0713139A - High polymer dispersed liquid crystal display element - Google Patents

Abstract

PURPOSE:To make it possible to obtain the bright display which lessen the decrease in light quantity by light absorption at substrates while the display is consisted of a reflection type by providing the display element with a liquid crystal/high polymer composite film between a pair of substrates, forming a transparent electrode on the front side substrate, formed as a transparent substrate, and forming electrodes and a light reflection film on the inside surface of the rear surface side substrate. CONSTITUTION:The region enclosed with a sealing agent 15 between a pair of the front and rear substrates 11 and 12 is provided with the liquid crystal/high polymer composite film 16. The electrode 13 for impressing voltages to this composite film 16 are formed on the inside surface of the front surface side substrate 11. The electrodes 14 for impressing the voltages to the composite film 16 and the reflection film 17 for reflecting light are formed on the rear surface side substrate 12. The light entering from the front surface side and past the composite film 16 does not pass the rear surface side substrate 12 and is reflected by the reflection film 17 on the inside surface of the rear surface side substrate 12. As a result, the decrease in the light quantity by the light absorption at the substrate is only the decrease-component by the front surface side substrate 11 and, therefore, the decrease in the light quantity is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective polymer dispersed liquid crystal display device.

[0002]

2. Description of the Related Art A polymer dispersed liquid crystal display device has a liquid crystal / polymer composite film provided between a pair of transparent substrates and has the following structure. FIG. 4 is a sectional view of a conventional polymer dispersed liquid crystal display device. In this polymer-dispersed liquid crystal display element, a pair of transparent substrates 1 and 2 made of glass or the like are joined via a frame-shaped sealing material 5 and surrounded by the sealing material 5 between the substrates 1 and 2. A liquid crystal / polymer composite film 6 is provided in the region, and transparent electrodes 3 and 4 are formed on the inner surfaces of the substrates 1 and 2 (the surfaces facing the composite film 6), respectively.

The liquid crystal / polymer composite film 6 is one in which liquid crystal is dispersed in a polymer, and the composite film 6 is formed by polymer-like gaps having a cross section like a sponge. Each has a structure in which liquid crystal is confined. As the liquid crystal, a nematic liquid crystal having a positive dielectric anisotropy is generally used.

This polymer-dispersed liquid crystal display device is driven for display by applying a voltage between electrodes 3 and 4 formed on both substrates 1 and 2, and each liquid crystal dispersed in the polymer. The liquid crystal molecules in the part (the part in which the liquid crystal is confined) face in various directions when no voltage is applied, and in this state, the light passing through the composite film 6 causes the liquid crystal part and the polymer to move. Scattered by the light scattering effect of the interface and the liquid crystal part. When a voltage higher than the threshold voltage of the liquid crystal is applied between the electrodes 3 and 4, the liquid crystal molecules in the liquid crystal parts are uniformly arranged so as to be substantially perpendicular to the substrate surface, and the composite film 6 is formed. Light passing through is transmitted with almost no light scattering effect.

That is, the polymer-dispersed liquid crystal display element displays by utilizing the transmission and scattering of light.
It has the advantage that the screen is brighter than the commonly used TN type liquid crystal display device.

Therefore, the above-mentioned polymer dispersed liquid crystal display element is generally used as a reflection type element by disposing the reflection plate 7 on the back surface thereof. In this reflection type polymer dispersed liquid crystal display device, the light incident from the surface side passes through the liquid crystal / polymer composite film 6 and is reflected by the reflection plate 7, and again passes through the composite film 6 and is emitted to the surface side. Therefore, the light passing through the voltage non-applied portion is doubly scattered, and the contrast with the transmitted light passing through the voltage applied portion is increased.

[0007]

However, in the above-mentioned conventional polymer dispersed liquid crystal display device, the incident light is emitted through the transparent substrate 1 on the front surface side and the transparent substrate 2 on the rear surface side twice, respectively. There has been a problem that the light quantity of the substrates 1 and 2 is greatly reduced due to the light absorption, which causes the display brightness to be dark.

An object of the present invention is to provide a polymer-dispersed liquid crystal display device which is a reflection type and which can obtain a bright display by reducing the decrease in the amount of light due to the absorption of light by the substrate. is there.

[0009]

The polymer-dispersed liquid crystal display device of the present invention is provided with a liquid crystal / polymer composite film in which a liquid crystal is dispersed in a polymer between a pair of front and back substrates, and the front side substrate is As a transparent substrate, a transparent electrode is formed on the inner surface thereof, and an electrode and a reflection film for reflecting light are formed on the inner surface of the rear substrate.

As an embodiment of the present invention, it is conceivable that the reflection film is a color reflection film made of a resin film mixed with a fluorescent pigment. The reflective film may be formed on the electrode or below the electrode. When the reflective film is formed under the electrode, the electrode may be a transparent electrode.

[0011]

That is, in the polymer dispersed liquid crystal display device of the present invention, the light incident from the front surface side and passing through the liquid crystal / polymer composite film is reflected by the reflective film on the inner surface of the back side substrate. According to this polymer-dispersed liquid crystal display element, the light amount reduction due to the light absorption in the substrate is only the reduction amount due to the front side substrate, so that the light amount reduction can be reduced and a bright display can be obtained.

Further, as in the above-mentioned one embodiment, when the reflection film is a color reflection film made of a resin film mixed with a fluorescent pigment, the light reflected by the reflection film becomes colored fluorescence, so that a bright color is obtained. Can be displayed.

[0013]

EXAMPLE An example of the polymer dispersed liquid crystal display device of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view of a polymer dispersed liquid crystal display device, and FIG. 2 is an enlarged sectional view of a part of a liquid crystal / polymer composite film.

In this polymer-dispersed liquid crystal display element, a pair of front and back substrates 11 and 12 are bonded together via a frame-shaped sealing material 15, and a region surrounded by the sealing material 15 between the two substrates 11 and 12 is joined. A liquid crystal / polymer composite film 16 is provided, and the composite film 16 is provided on the inner surface (the surface facing the composite film 16) of the front surface side substrate (the upper substrate in the figure) 11 of the both substrates 11, 12. An electrode 13 for applying a voltage is formed on the inner surface of the back-side substrate (lower substrate in the drawing) 12
An electrode 14 for applying a voltage to the composite film 16 and a reflective film 17 for reflecting light are formed.

The liquid crystal display device of this embodiment is of a simple matrix type, the electrodes 13 formed on the front substrate 11 are scanning electrodes, and the electrodes 1 formed on the rear substrate 12 are.
4 is a signal electrode.

The front side substrate 11 of the liquid crystal display device
Is a transparent substrate made of glass or the like, and the electrode 13 of the front side substrate 11 is a transparent electrode made of a transparent conductive film such as ITO.

The backside substrate 12 is, for example, a glass substrate, and the electrodes 14 of the backside substrate 12 are Al.
The reflective film 17 is formed of a low resistance metal film such as (aluminum), and is formed on the electrode 14 over substantially the entire surface of the substrate 12. The reflection film 17 is made of an insulating film, and in this embodiment, the reflection film 17 is a color reflection film made of a resin film mixed with a fluorescent pigment.

On the other hand, the liquid crystal / polymer composite film 16 is one in which liquid crystal is dispersed in a polymer.
2 has a structure in which the liquid crystal 16b is confined in each gap of the polymer layer 16a polymerized so as to have a cross section like a sponge, as shown in FIG.

The polymer-dispersed liquid crystal display device includes a front-side substrate (transparent substrate) 11 having a transparent electrode 13 formed thereon and a back-side substrate 12 having a metal electrode 14 formed thereon and a reflective film 17 formed thereon. After joining through a sheet-shaped sealing material 15, a mixed solution of a liquid crystal and a polymer material which undergoes a polymerization reaction by light is sealed in a region surrounded by the sealing material 15 between the substrates 11 and 12, It is manufactured by a method in which light (ultraviolet rays) is uniformly irradiated from the outer surface side of the transparent front surface side substrate 11 to the entire encapsulation region of the mixed solution to photopolymerize the polymer material.

As described above, when the mixed solution sealed between the substrates 11 and 12 is irradiated with light, the double bond of the polymer material in a monomer or oligomer state is dissolved to form a radical, and a radical of an adjacent molecule is generated. Are polymerized by a radical polymerization reaction in which they are bonded to each other, and the liquid crystal is phase-separated by polymerizing the polymer material.

Therefore, the polymer material has a cross section like a sponge, and the liquid crystal is confined in the gaps of the polymer layer to form the composite film 16. In addition,
The method of forming this composite film is called a photopolymerization phase separation method.

In the polymer dispersed liquid crystal display element, since the reflection film 17 for reflecting light is formed on the inner surface of the back side substrate 12, the liquid crystal / polymer composite film 16 is incident from the front side. The light that has passed through does not pass through the back-side substrate 12 and does not pass through the reflection film 1 on the inner surface of the back-side substrate 12.
Reflected by 7.

Therefore, according to the polymer-dispersed liquid crystal display element, the light amount reduction due to the light absorption in the substrate is only the reduction amount due to the front side substrate 11, and therefore the light amount reduction is reduced to obtain a bright display. be able to.

Further, in the above embodiment, since the reflection film 17 is the color reflection film made of the resin film mixed with the fluorescent pigment, the light reflected by the reflection film 17 becomes the colored fluorescence, so that the bright color display is obtained. Is obtained.

That is, the polymer-dispersed liquid crystal display device is driven for display by applying a voltage between the electrodes 13 and 14 formed on both substrates 11 and 12, but each is dispersed in the polymer. The liquid crystal molecules of the liquid crystal part (the part in which the liquid crystal 16b is confined) face in various directions when no voltage is applied, and in this state, the light passing through the composite film 16 and the liquid crystal part are high. Since the light is scattered by the interface with molecules and the light-scattering action of the liquid crystal part, the display of the non-voltage applied part becomes a white turbid display.

When a voltage equal to or higher than the threshold voltage of the liquid crystal 16b is applied between the electrodes 3 and 4, the liquid crystal molecules in each liquid crystal portion are uniformly arranged so as to be substantially perpendicular to the surfaces of the substrates 11 and 12. Since the light which is arranged and passes through the composite film 16 is transmitted with almost no light scattering effect, the display of the voltage applying portion is shown by the reflection plate 1.
The light reflected by 7 is displayed, but if the reflection film 17 is a color reflection film made of a resin film mixed with a fluorescent pigment, the light reflected by the reflection film 17 becomes colored fluorescence. The display of the voltage application section becomes a bright color display.

Moreover, in the polymer dispersed liquid crystal display device, the light incident from the surface side thereof passes through the liquid crystal / polymer composite film 16 and is reflected by the reflection film 17, and again passes through the composite film 16 to the surface. Since the light is emitted to the side, the light passing through the voltage applying section is doubly scattered, and the degree of white turbidity of the above-described white turbid color increases, and the display of the voltage applying section is a bright fluorescent color display. It is possible to obtain a better contrast than the conventional reflective element display.

In the above embodiment, the reflective film 17 provided on the inner surface of the rear substrate 12 is formed on the electrode 14, but the reflective film 17 may be formed under the electrode 14,
In that case, the electrode 14 may be a transparent electrode.

FIG. 3 is a sectional view of a polymer dispersed liquid crystal display device showing another embodiment of the present invention. In this embodiment, a reflective film 17 provided on the inner surface of the backside substrate 12 is formed under the electrode 14. And an electrode 14 made of a transparent conductive film such as ITO
Is formed. The liquid crystal display element of the embodiment shown in FIG. 3 is the same as the liquid crystal display element shown in FIG. 1 except that the electrode 14 of the rear substrate 12 is used as a transparent electrode and a reflective film 17 is formed thereunder. Since they are the same, duplicate explanations are given the same reference numerals in the drawings and omitted.

In the above embodiment, the backside substrate 12 is a glass substrate, but the backside substrate 12 can be made of any material, transparent or opaque, and the reflection film 17 can be used. However, as long as it has a high light reflectance, it is not limited to the color reflection film mixed with the fluorescent pigment.

[0031]

The polymer-dispersed liquid crystal display device of the present invention is provided with a liquid crystal / polymer composite film in which a liquid crystal is dispersed in a polymer between a pair of front and back substrates, and the front side substrate is a transparent substrate. A transparent electrode is formed on the inner surface, and an electrode and a reflective film that reflects light are formed on the inner surface of the backside substrate, so even though it is a reflective type, the amount of light is reduced by light absorption by the substrate. Can be reduced to obtain a bright display.

Further, in the polymer dispersed liquid crystal display device of the present invention, if the reflection film is a color reflection film made of a resin film mixed with a fluorescent pigment, the light reflected by the reflection film becomes colored fluorescence. , Bright color display is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a polymer dispersed liquid crystal display device showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a part of the liquid crystal / polymer composite film.

FIG. 3 is a sectional view of a polymer-dispersed liquid crystal display device showing another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional polymer dispersed liquid crystal display device.

[Explanation of symbols]

 11 ... Front side substrate (transparent substrate) 12 ... Back side substrate 13 ... Transparent electrode 14 ... Electrode 16 ... Liquid crystal / polymer composite film 16a ... Polymer layer 16b ... Liquid crystal

Claims (4)

[Claims] 1. A liquid crystal / polymer composite film in which a liquid crystal is dispersed in a polymer is provided between a pair of front and back substrates, and the front substrate is a transparent substrate having a transparent electrode formed on its inner surface and a back surface. A polymer dispersed liquid crystal display device characterized in that an electrode and a reflection film for reflecting light are formed on the inner surface of the side substrate. 2. The polymer dispersed liquid crystal display device according to claim 1, wherein the reflection film is a color reflection film made of a resin film mixed with a fluorescent pigment. 3. The polymer dispersed liquid crystal display device according to claim 1, wherein the reflective film is formed on the electrode. 4. The reflective film is formed under an electrode, and the electrode is a transparent electrode.
Alternatively, the polymer dispersed liquid crystal display device according to claim 2.