JPH07104254A - Polymer dispersion type liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide a polymer dispersion type liquid crystal display element in which reflection of light on the surface of the substrate can be suppressed so that picture images can visually and clearly be recognized. CONSTITUTION:A back side substrate 1 on which plural transparent picture element electrodes 3 and plural thin film transistors 4 corresponding to these picture element electrodes 3 respectively are formed and a top side substrate 2 having a transparent counter electrode 12 facing to the picture element electrodes 3 are disposed with the electrode forming surfaces faced with each other. A liquid crystal/polymer composite film 13 formed by dispersion of a liquid crystal in a polymer layer is interposed between these substrates 1, 2. Further, the surfaces of the top side substrate 2 is covered with a resin film 16 as a reflection restraining member to suppress reflection of light on this surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer dispersion type liquid crystal display device which displays an image by using a liquid crystal / polymer composite film in which liquid crystal is dispersed in a polymer layer.

[0002]

2. Description of the Related Art In a polymer dispersion type liquid crystal display device, liquid crystal is dispersed in a polymer layer in a cell in which a pair of transparent substrates having transparent electrodes are bonded to each other via a frame-shaped sealing material. A liquid crystal / polymer composite film is provided, and as the liquid crystal, for example, nematic liquid crystal having positive dielectric anisotropy is used.

This polymer-dispersed liquid crystal display device is driven by applying a voltage between the electrodes of both substrates, and the molecules of the liquid crystal dispersed in the polymer are not applied with a voltage. In the state, it faces various directions, and under this state,
Light passing through the liquid crystal / polymer composite film is scattered by the light scattering action of the liquid crystal. Then, when a voltage is applied between the electrodes, the molecules of the liquid crystal are uniformly arranged so as to stand substantially perpendicular to the substrate surface, and based on this arrangement, light passing through the liquid crystal / polymer composite film is hardly scattered. See through. Then, an image of a predetermined pattern is displayed by transmitting and scattering this light.

Such a polymer-dispersed liquid crystal display device does not require a polarizing plate provided on the surface of the substrate, and has a merit that the screen is brighter than that of a commonly used TN type liquid crystal display device. Therefore, it is particularly advantageous in the case of a reflection type liquid crystal display element in which a reflection plate is provided on the back surface of the element and natural light or indoor illumination light incident from the front surface side of the element is reflected by the reflection plate and emitted to the front surface side. .

[0005]

As described above, in the polymer-dispersed liquid crystal display device, there is no polarizing plate on the surface of the substrate, and therefore the displayed image is visually recognized by directly looking at the surface of the substrate. However, on the surface of the substrate, since the polarizing plate is not arranged, light is strongly reflected, so that the surface of the substrate flickers and the image becomes difficult to see depending on the angle at which the image is viewed.

The present invention has been made by paying attention to such a point, and an object thereof is a polymer dispersion capable of suppressing reflection of light on a surface of a substrate and visually recognizing an image clearly. Type liquid crystal display device.

[0007]

In order to achieve such an object, the present invention provides a backside substrate on which a plurality of transparent pixel electrodes and a plurality of active elements respectively corresponding to these pixel electrodes are formed, A liquid crystal / polymer in which a substrate on the front side on which a transparent counter electrode facing the pixel electrode is formed is disposed with their electrode forming surfaces facing each other, and a liquid crystal is dispersed in a polymer layer between the two substrates. A composite film is provided, and a reflection suppressing portion that suppresses reflection of light on the surface is provided on the surface of the substrate on the front surface side.

[0008]

In the polymer-dispersed liquid crystal display device having such a structure, the reflection suppressing portion is provided on the surface of the substrate on the front side. Therefore, the reflection of light on the surface of the substrate causes the reflection suppressing portion. The surface of the substrate is not fluctuated when viewed from any angle direction,
The image can be clearly viewed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a partial cross section of an active matrix polymer dispersion type liquid crystal display device according to a first embodiment of the present invention, in which the lower side substrate 1 is on the lower side and the upper side is the front side. Substrate 2 is arranged. These substrates 1 and 2 are made of a transparent material such as glass,
A plurality of transparent pixel electrodes 3 arranged in the row direction and the column direction and a plurality of active elements 4 respectively corresponding to the pixel electrodes 3 are arranged on the substrate 1 on the back surface side. A reflection plate 5 is provided on the outer surface (lower surface) of the substrate 1 on the back surface side.

The active element 4 is, for example, a thin film transistor, and the thin film transistor 4 includes a gate electrode 6 formed on the substrate 1, a gate insulating film 7 covering the gate electrode 6, and the gate insulating film 7. A semiconductor film 8 formed of a-Si (amorphous silicon) or the like facing the gate electrode 6, and a source electrode 9 and a drain electrode 10 formed on both sides of the semiconductor film 8.
It consists of and.

Although not shown, a gate line (address line) for supplying a gate signal to the thin film transistor 4 and a data signal corresponding to image data are supplied to the thin film transistor 4 on the back surface of the substrate 1. The thin film transistor 4 has a gate electrode 6 formed integrally with the gate line, and a source electrode 9 connected to the data line.

The gate insulating film 7 is a transparent film made of SiN (silicon nitride) or the like, and the pixel electrode 3 is formed on the gate insulating film 7, and one end of the pixel electrode 3 has a drain electrode of the corresponding thin film transistor 4. Connected to 10.

On the other hand, on the inner surface of the substrate 2 on the front surface side, almost all the pixel electrodes 3 of the substrate 1 on the rear surface side are covered over almost the entire surface.
A transparent counter electrode 12 is formed to face the. The substrate 1 on the back surface side and the substrate 2 on the front surface side are bonded to each other via a frame-shaped sealing material (not shown) in the peripheral portion, and a liquid crystal / polymer composite film 13 is provided between the substrates 1 and 2. There is.

The liquid crystal / polymer composite film 13 is obtained by dispersing liquid crystal in a polymer layer, and the liquid crystal is confined in each void of the polymer layer 14 polymerized to have a sponge-like cross section. The liquid crystal portion 15 has the above structure and is shown in FIG.

Such a liquid crystal / polymer composite film 13 can be formed by a photopolymerization phase separation method. That is,
After the pair of substrates 1 and 2 are bonded to each other via a sealing material, a polymer material that undergoes a polymerization reaction by light is passed between the two substrates 1 and 2 through an injection port formed by removing a part of the sealing material. Fill the liquid mixture with liquid crystal by vacuum injection method,
This mixture is irradiated with ultraviolet rays from the front side substrate 2 side to photopolymerize the polymer material. The injection port is sealed after injection of the mixed solution or after photopolymerization of the polymer material.

As described above, when the mixed solution filled between the substrates 1 and 2 is irradiated with ultraviolet rays, the polymer material in the state of a monomer or an oligomer is radicalized by thawing its double bond, so that the adjacent molecules The radical polymerization reaction in which the radicals bond to each other creates a polymer, and the liquid crystal is phase-separated by polymerizing the polymer material.

For this reason, the polymerized polymer layer 14 has a sponge-shaped cross section, and liquid crystal is confined in each void of the polymer layer 14 to form the liquid crystal / polymer composite film 13 having the above-described structure. Become.

This polymer-dispersed liquid crystal display device comprises a liquid crystal /
An image is displayed by utilizing the scattering and transmission of light in the polymer composite film 13, and the molecules of the liquid crystal of the liquid crystal part 15 dispersed in the polymer layer 14 of the composite film 13 generate an electric field. When not applied, the light is oriented in various directions, and when light incident from the front surface side of the substrate 2 on the front surface side passes through the composite film 13, the interface between the liquid crystal portion 15 and the polymer layer 14 and The light is scattered by the light scattering action of the liquid crystal of the liquid crystal unit 15.

When an electric field is applied between the pixel electrode 3 and the counter electrode 12 of both substrates 1 and 2, the liquid crystal molecules of the liquid crystal portion 15 of the composite film 13 stand substantially perpendicular to the surfaces of the substrates 1 and 2. Thus, the light that is uniformly oriented and enters from the surface of the substrate 2 on the front surface side passes through the composite film 13 with almost no light scattering effect of the composite film 13. Then, this light is reflected by the reflection plate 5, passes through the composite film 13 again, and is emitted to the surface of the substrate 2 on the front surface side.

As described above, in this polymer dispersion type liquid crystal display element, an image is displayed by utilizing the scattering and transmission of light in the liquid crystal / polymer composite film 13, and therefore the TN type liquid crystal. A polarizing plate, which is indispensable for a display element, is unnecessary, and there is no loss of light amount due to light absorption in the polarizing plate, and bright display can be achieved.

However, since no polarizing plate is arranged on the surface of the substrate 2 on the front side, light is strongly reflected on the surface of the substrate 2 on the front side. Therefore, when the surface of the substrate 2 is viewed from an angle. In addition, the surface is flicker and the image becomes difficult to see.

Therefore, in this embodiment, the resin film 16 is attached to the front surface of the substrate 2 as a reflection suppressing portion. As the resin film 16, a so-called non-reflective film or low-reflective film which is generally commercially available is used.

In such a structure, the resin film 16 suppresses the reflection of light on the surface of the substrate 2 on the front surface side, and therefore the surface of the substrate 2 is uneven when viewed from any angle direction. The image can be clearly viewed without being touched.

By the way, the outer surface of the substrate 1 on which the pixel electrodes 3 and the active elements 4 are formed is used as a display portion of a liquid crystal display element, and the resin film 1 as a reflection suppressing portion is formed on this surface.
It is conceivable to paste 6. However, in this case, since the reflection of light on the surface of the substrate 1 is suppressed by the resin film 16, the contours of the pixel electrodes 3 and the active elements 4 formed on the inner surface of the substrate 1 can be clearly seen. Therefore, the display quality is rather degraded.

In the present embodiment, in order to avoid such inconvenience, the surface side of the substrate 2 on which the counter electrode 12 is formed is used as a display portion, and the resin film 16 as a reflection suppressing portion is formed on the surface of the substrate 2. Is attached. The counter electrode 12 formed on the inner surface of the substrate 2 is formed uniformly over almost the entire inner surface thereof. Therefore, when the resin film 16 is attached to the surface of the substrate 2, the substrate 2 Even if the reflection of light on the surface is suppressed, the contour of the counter electrode 12 is not visible, and good display quality can be maintained.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. In the second embodiment, the surface of the substrate 2 on which the counter electrode 12 is formed is subjected to a non-reflective or low-reflection surface treatment 17 as a reflection suppressing portion to reflect light on the surface of the substrate 2. I try to suppress it.

As the method of the surface treatment 17, for example, the surface of the substrate 2 made of glass is soft-etched with a fluorine compound or the like to roughen the surface, or the surface of the substrate 2 is subjected to a non-reflective film by vapor deposition or the like. And a method of coating a low reflection film, and a method of coating the surface of the substrate 2 with a resin such as a fluororesin having a small refractive index.

In the second embodiment as described above, similarly to the first embodiment, the reflection suppressing portion on the surface of the substrate 2 suppresses the reflection of light on the surface of the substrate 2, and thus the substrate 2 The image can be clearly seen regardless of the angle of the surface. Although the liquid crystal display element is constructed as a reflection type in any of the above-mentioned embodiments, it does not matter even if it is constructed as a transmission type.

[0029]

As described above, according to the present invention, since the surface of the substrate on which the counter electrode is formed is used as the display portion and the reflection suppressing portion is provided on this surface, the reflection of light on the surface is prevented. The image can be clearly viewed by suppressing the above, and the counter electrode on the inner surface of the substrate is inconspicuous, so that good display quality can be maintained.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a polymer-dispersed liquid crystal display device showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate on the front side 2 ... Substrate on the back surface 3 ... Pixel electrode 4 ... Thin film transistor (active element) 12 ... Counter electrode 13 ... Liquid crystal / polymer composite film 16 ... Resin film (reflection suppressing part) 17 ... Surface treatment (reflection) Suppressor)

Claims (3)

[Claims] 1. A backside substrate on which a plurality of transparent pixel electrodes and a plurality of active elements corresponding to the pixel electrodes are formed, and a frontside substrate on which a transparent counter electrode facing the pixel electrodes is formed. And the electrode forming surfaces thereof are opposed to each other, a liquid crystal / polymer composite film in which a liquid crystal is dispersed in a polymer layer is provided between the both substrates, and the surface of the substrate on the surface side has this surface. A polymer-dispersed liquid crystal display device, which is provided with a reflection suppressing portion that suppresses the reflection of light on the screen. 2. The polymer dispersed liquid crystal display according to claim 1, wherein the reflection suppressing portion is formed by attaching a non-reflective or low-reflective resin film to the surface of the substrate on the front side. element. 3. The polymer dispersion type liquid crystal display element according to claim 1, wherein the reflection suppressing portion is formed by subjecting the surface of the front surface side substrate to a surface treatment.