JPH0517625U - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] To make white turbidity at the edge of the displayed image inconspicuous when viewed from an oblique direction, and to widen the appropriate viewing angle for observing the displayed image as a sharp image. [Structure] A pair of transparent substrates 1 having transparent electrodes 14 and 15
Liquid crystal cell 1 in which a polymer dispersed liquid crystal layer 16 is provided between 2 and 13.
In the liquid crystal display device in which the reflection plate 17 is arranged on the back surface side of No. 1, the thickness of at least the back surface side substrate 13 of the liquid crystal cell 11 is set to 0.3 mm or less.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a liquid crystal display device using a polymer dispersed liquid crystal.

[0002]

[Prior Art]

 Liquid crystal display devices using polymer-dispersed liquid crystals are mainly used as display devices for small electronic devices such as electronic wrist watches and calculators. As shown in FIG. 2, this liquid crystal display device comprises a liquid crystal cell 1 and a reflection plate 7 arranged on the back surface side of the liquid crystal cell 1.

In the above liquid crystal cell 1, a pair of transparent substrates 2 and 3 on which transparent electrodes 4 and 5 are formed are arranged with their electrode forming surfaces facing each other, and a polymer dispersed liquid crystal is placed between these substrates 2 and 3. A layer 6 is provided, and the substrates 2 and 3 are bonded to each other at their outer peripheral portions via a frame-shaped sealing material (not shown), and the polymer dispersed liquid crystal layer 6 is provided in an area surrounded by the sealing material. It is provided over the entire area. The polymer-dispersed liquid crystal layer 6 is a mixture of a transparent polymer 6a and a nematic liquid crystal 6b, as shown in a partially enlarged view in FIG.

The polymer-dispersed liquid crystal layer 6 is formed by injecting a solution obtained by mixing a photocurable polymer monomer and liquid crystal between both substrates 2 and 3 by a vacuum injection method, and thereafter, the outer surface of one substrate. It is formed by irradiating light (ultraviolet ray) from the side to polymerize the above-mentioned polymer monomer to polymerize it, and the liquid crystal 6b is enclosed between the polymerized polymer 6a in a mesh form. ing.

This liquid crystal display device is driven by applying an electric field between the electrodes 4 and 5 of both substrates 2 and 3 of the liquid crystal cell 1, and is driven by display. Are oriented in various directions when no electric field is applied. In this state, the light transmitted through the polymer-dispersed liquid crystal layer 6 has a light scattering action by the liquid crystal 6b and the liquid crystal 6b and the polymer layer 6a. It is scattered by the action of light scattering at the interface. When an electric field above the threshold voltage of the liquid crystal is applied between the electrodes 4 and 5, the molecules of the liquid crystal 6b are uniformly arranged so as to be perpendicular to the surfaces of the substrates 2 and 3, and the transmitted light scatters. The light is transmitted through the high molecular dispersion liquid crystal layer 6 with almost no effect. The light transmitted through the polymer dispersed liquid crystal layer 6 is reflected by the reflection plate 7 arranged on the back surface of the liquid crystal cell 1.

Therefore, when this liquid crystal display device is observed from the surface side of the liquid crystal cell 1, the electric field-free region in the polymer-dispersed liquid crystal layer 6 where light is scattered appears to be cloudy because the light transmittance is poor. Since the light is transmitted through the polymer-dispersed liquid crystal layer 6 with a high transmittance, the electric field applying section looks bright.

That is, in this liquid crystal display device, the transmission state of light that enters the liquid crystal cell 1 from its front surface side, is reflected by the reflection plate 7 on the back surface of the liquid crystal cell 1, and is emitted to the front surface side of the liquid crystal cell 1 is shown. Controlled by the polymer-dispersed liquid crystal layer 6 of the liquid crystal cell 1, the region corresponding to the non-voltage-applied portion of the polymer-dispersed liquid crystal layer 6 becomes a clouded region A, which corresponds to the voltage-applied portion of the polymer-dispersed liquid crystal layer 6. Since the region to be turned is the bright transparent region B, an optical image corresponding to the shape of the voltage application electrode is displayed in the white turbid background. Note that, in FIG. 2, the part without the electrodes 4 and 5 is a cloudy region A, but when no voltage is applied between the electrodes 4 and 5, this part is also a cloudy region.

In some of the liquid crystal display devices, as the reflection plate 7, one whose reflection surface is colored in a single color or a plurality of colors is used. The optical image displayed on the screen appears to be colored in the color of the reflection plate 7.

[0009]

[Problems to be solved by the device]

 However, in the conventional liquid crystal display device, it is good to view the display from the front side (direction substantially perpendicular to the front substrate 1 surface), but when viewed from an oblique direction, the edge portion of the display image becomes cloudy. Since it is visible, there was a problem that the suitable viewing angle for observing the displayed image as a sharp outline image is narrow.

This is because the reflection surface of the reflection plate 7 is separated from the polymer dispersed liquid crystal layer 6 of the liquid crystal cell 1 by the thickness of the rear substrate 2 of the liquid crystal cell 1. When the boundary portion between the transparent region B and the cloudy region A of the high molecular dispersion liquid crystal layer 6 is viewed obliquely as shown by the arrow a in FIG. 2, a portion corresponding to the cloudy region A on the surface of the reflection plate 7 can be seen. Then, since a cloudy color is reflected in the part corresponding to the cloudy area A on the surface of the reflector 7, the edge of the display image displayed in the transparent area B appears clouded and the outline of the display image is displayed. It will be blurred.

An object of the present invention is to provide a liquid crystal display device in which a reflecting plate is arranged on the back side of a liquid crystal cell using polymer dispersed liquid crystal, and almost all the white turbidity at the edge portion of the display image when viewed from an oblique direction. An object of the present invention is to provide a device that can be made inconspicuous and can have a wide suitable viewing angle for observing a displayed image as an image with a clear outline.

[0012]

[Means for Solving the Problems]

 The present invention relates to a liquid crystal display device in which a reflector is arranged on the back side of a liquid crystal cell in which a polymer dispersed liquid crystal layer is provided between a pair of transparent substrates having transparent electrodes. It is characterized in that the thickness is 0.3 mm or less.

[0013]

[Action]

 As described above, when the thickness of at least the back side substrate of the liquid crystal cell is set to 0.3 mm or less, the portion corresponding to the white turbid area on the reflector surface is hardly seen even when viewed from an oblique direction, so that the display image White turbidity at the edges is almost inconspicuous.

[0014]

【Example】

 An embodiment of the present invention will be described below with reference to FIG. The liquid crystal display device of this embodiment comprises a liquid crystal cell 11 and a reflection plate 17 arranged on the back surface side of the liquid crystal cell 11.

In the liquid crystal cell 11, a pair of transparent substrates (for example, glass plates) 12 and 13 on which transparent electrodes 14 and 15 are formed are arranged with their electrode formation surfaces facing each other, and between the substrates 12 and 13. A polymer-dispersed liquid crystal layer 16 is provided, and the front-side substrate 12 and the back-side substrate 13 of the liquid crystal cell 11 are ultrathin plates having a thickness of 0.3 mm or less.

The both substrates 12 and 13 are bonded to each other at their outer peripheral portions via a frame-shaped sealing material (not shown), and the polymer dispersed liquid crystal layer 16 is entirely covered in the area surrounded by the sealing material. It is installed over.

The polymer dispersed liquid crystal layer 16 is a mixture of transparent polymer and nematic liquid crystal, and the polymer dispersed liquid crystal layer 16 is provided in a liquid crystal cell of a conventional liquid crystal display device. Similar to the polymer dispersed liquid crystal layer, a solution in which a photocurable polymer monomer and liquid crystal are mixed is injected between both substrates 12 and 13, and light (ultraviolet ray) is irradiated from the outer surface side of one substrate. Thus, it is formed by a method of polymerizing the above-mentioned polymer monomer by photopolymerization.

Similarly to the conventional liquid crystal display device shown in FIG. 2, this liquid crystal display device also enters the liquid crystal cell 11 from its front surface side and is reflected by the reflection plate 17 on the back surface of the liquid crystal cell 11 to cause a liquid crystal cell. The polymer dispersed liquid crystal layer 16 of the liquid crystal cell 11 controls the transmission state of the light emitted to the surface side of the liquid crystal cell 11, and the region corresponding to the non-voltage applied portion of the polymer dispersed liquid crystal layer 16, that is, transmitted light The region scattered by the polymer dispersed liquid crystal layer 16 becomes the cloudy region A, and the region corresponding to the voltage application portion of the polymer dispersed liquid crystal layer 16, that is, the region where the transmitted light is hardly scattered becomes the transparent region B. Therefore, an optical image corresponding to the shape of the voltage application electrode is displayed in the cloudy white background.

In FIG. 1, the part without the electrodes 14 and 15 is a cloudy region A, but when no voltage is applied between the electrodes 14 and 15, this part is also a cloudy region. Further, the reflector 17 may be a non-colored reflector or a colored reflector whose reflective surface is colored in a single color or a plurality of colors. When the colored reflector is used, it is displayed in a cloudy background. The reflected light image appears colored in the color of the reflection plate 17.

In the liquid crystal display device of this embodiment, as described above, since the back side substrate 13 of the liquid crystal cell 11 is an ultrathin plate having a thickness of 0.3 mm or less, the display of the liquid crystal display device is performed. Even when viewed from an oblique direction, the portion corresponding to the cloudy region A on the surface of the reflection plate 17 is hardly visible.

This is because the thickness of the rear substrate 13 of the liquid crystal cell 11, that is, the distance between the reflective surface of the reflector 17 and the polymer dispersed liquid crystal layer 16 of the liquid crystal cell 11 is 0.3 mm or less. Because it is small.

That is, when the boundary portion between the transparent region B and the cloudy region A of the polymer dispersed liquid crystal layer 16 is viewed in an oblique direction as shown by the arrow a in FIG. 1, the observed point on the surface of the reflector 17 is observed. The point where the tip of the arrow a reaches the reflection plate 17 surface is shifted from the boundary between the transparent region B and the cloudy region A to the cloudy region A side, but the reflection plate 17 surface and the polymer dispersed liquid crystal layer are If the distance to the boundary 16 is as small as 0.3 mm or less, the deviation width d of the observed point with respect to the boundary is extremely smaller than the deviation width D (see FIG. 2) in the conventional liquid crystal display device. .

The shift width d is substantially the same as the distance between the surface of the reflection plate 17 and the polymer dispersed liquid crystal layer 16 when the viewing angle for viewing the display of the liquid crystal display device is about 45 °, for example. The smaller the viewing angle (closer to the vertical), the smaller the viewing angle.

Light incident on the liquid crystal cell 11 from an oblique direction is refracted at the incident surface of the front surface side substrate 12 to increase its angle, and passes through the front surface side substrate 12 at that angle to disperse the polymer dispersed liquid crystal layer. Since the light is emitted to 16, the actual observed point on the surface of the reflection plate 17 is further displaced to the cloudy region A side than in FIG. 1, but the deviation of the observed point due to the refraction of light on the front substrate 12 is caused. Since the amount is determined by the refractive index and the plate thickness of the front surface side substrate 12, if the thickness of the front surface side substrate 12 is set to 0.3 mm or less as in this embodiment, the amount of light on the front surface side substrate 12 is reduced. The amount of displacement of the observed point due to refraction is also extremely small.

Therefore, in the above liquid crystal display device, even when the display is viewed from an oblique direction, the white turbid color reflected in the portion corresponding to the white turbid region A on the reflection plate 7 is hardly visible, and therefore, it is desired. Since the white turbidity at the edge of the displayed image is almost inconspicuous, the displayed image appears as a clear outline image.

The deviation width d is very small, for example, about 0.3 mm or less, even when the viewing angle for viewing the display of the liquid crystal display device is about 45 °, which is very small. It is possible to widen the appropriate viewing angle that can be observed as.

Although the thickness of both substrates 12 and 13 of the liquid crystal cell 11 is set to 0.3 mm or less in the above-mentioned embodiment, the deviation of the observed point on the reflection plate 17 surface is greatly affected. Since the thickness is the thickness of the back side substrate 13 between the surface of the reflection plate 17 and the polymer dispersed liquid crystal layer 16, the thickness of the front side substrate 12 of the liquid crystal cell 11 may be large to some extent.

[0028]

[Effect of the device]

 In the liquid crystal display device of the present invention, at least the back side substrate of the liquid crystal cell has a thickness of 0.3 mm or less. Therefore, it is possible to widen the suitable viewing angle for observing the displayed image as an image with a clear contour.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a conventional liquid crystal display device.

FIG. 3 is an enlarged cross-sectional view of a part of a polymer dispersed liquid crystal layer.

[Explanation of symbols]

11 ... Liquid crystal cell, 12, 13 ... Transparent substrate, 14, 15 ...
Transparent electrode, 16 ... Polymer dispersed liquid crystal layer, 17 ... Reflector.

Claims (1)

[Scope of utility model registration request] 1. A liquid crystal display device comprising a liquid crystal cell having a polymer-dispersed liquid crystal layer between a pair of transparent substrates having transparent electrodes, and a reflective plate disposed on the back surface side of the liquid crystal cell. A liquid crystal display device having a thickness of 0.3 mm or less.