JPH0895042A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a thin type liquid crystal display device having a wide angle of visibility of a scattering type liquid crystal. CONSTITUTION: Parallel rays 14 are incident on a liquid crystal panel 200 from a hologram lens 300 serving as a parallel ray generating panel arranged beneath the scattering type liquid crystal panel 200. The light rays from a light source 7 are converged by means of the hologram lens 300, and the converged parallel light rays are directly incident on a pattern layer 11 (layer having a hologram pattern) on the side face of the hologram lens 300, so that the light rays cause diffraction on the pattern layer 11 and reflected parallel light rays 14 are formed. When light rays are scattered on the liquid crystal panel 200, the light rays to be scattered are scattered and directed in almost all directions from the liquid crystal panel 200 surface, and when voltage is impressed to a picture element electrode 2 the light rays transmit to advance straight and maintain the incident direction. Therefore, a picture element electrode area to which voltage is impressed becomes invisible and dark excepting the direction in which the light rays advance, and as a result, a contrast is formed.

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 thin, direct-viewing type liquid crystal display device using a scattering type liquid crystal panel.

[0002]

2. Description of the Related Art In a liquid crystal display device capable of displaying an image, a liquid crystal panel which has conventionally used a twisted nematic (TN) liquid crystal has a narrow viewing angle. However, the display quality is not good. Although it has been improved a lot recently, its scope of application is still narrow and limited. Therefore, as disclosed in Japanese Patent Laid-Open No. 5-165019, it has been attempted to obtain a display device having high brightness and a wide viewing angle by using a scattering type liquid crystal (polymer dispersion type liquid crystal, PDLC). This is to obtain a wide field of view by directly looking at the scattered light of the scattering type liquid crystal.

Scattering type liquid crystal (polymer dispersed type liquid crystal, PDLC)
As its name suggests, a low molecular weight liquid crystal is included in a polymer network structure and dispersed, and it is sandwiched between two transparent electrodes, and the light scattering state occurs as voltage is applied to the electrodes. To a light transmission state. When utilizing this property, there are two methods of visually observing scattered light: light transmitted through the liquid crystal panel and light reflected by placing a reflector under the liquid crystal panel. In either case, the problem is how to remove the light component (direct light) that directly arrives without being scattered. A commonly used method is to make parallel light incident from an oblique direction so that an observer does not directly see the parallel light.

[0004]

However, in such a configuration, it is necessary to irradiate the light source away from the liquid crystal panel, the optical system becomes large, and the characteristic of the liquid crystal panel aiming at thinness is lost. There is a problem.

Therefore, an object of the present invention is to provide a thin liquid crystal display device using a scattering type liquid crystal having a very wide viewing angle in order to solve the above problems.

[0006]

In order to solve the above problems, the structure of the present invention is a liquid crystal display device using a transmissive liquid crystal panel, in which light from a light source optical system is refracted on the back side of the liquid crystal panel. Parallel light generating panel for generating parallel light, and the parallel light generating panel causes the parallel light to enter the liquid crystal panel.

The structure of the present invention is also that the parallel light generating panel is a hologram lens. In addition to this, the characteristic configuration is that the light source optical system further introduces parallel light focused by an optical lens from the side surface of the hologram lens. In addition, the light source optical system,
The optical prism installed on the lower surface of the end of the hologram lens introduces parallel light substantially parallel to the layer having the hologram pattern of the hologram lens. Alternatively, the layer having the hologram pattern has a thick and thin structure having a thick portion and a thin portion in the thickness direction of the layer, and the hologram pattern is formed in large numbers with increasing distance from the optical system. . As yet another configuration,
The hologram pattern is a hologram pattern that is multiple-exposure at any wavelength, as a whole, between the liquid crystal panel and the parallel light generation panel,
It has a characteristic structure that it has a structure in which a cooling medium flows.

[0008]

According to the first aspect of the present invention, the parallel light is incident on the liquid crystal panel from the parallel light generating panel provided below the scattering type liquid crystal panel. When the light is scattered by the liquid crystal panel, the scattered light is scattered and advances in almost all directions from the liquid crystal panel surface, and when a voltage is applied to the pixel electrode, the light is transmitted and goes straight, and the incident direction is maintained. To do. Therefore, the pixel electrode region to which the voltage is applied is invisible except in the direction in which light travels, and becomes dark, and contrast is formed.

When the parallel light generating panel is a hologram lens, the light source optical system collects the light from the light source with the lens, and with respect to the pattern layer (layer having the hologram pattern) on the side surface of the hologram lens, Since collimated parallel light is made incident, the light is diffracted in the pattern layer.
When an optical prism is used in the light source optical system as in claim 4, the incident light from obliquely below is refracted substantially parallel to the pattern layer of the hologram lens because of the refractive index, and also the light is effectively emitted to the pattern layer. spread. According to the fifth aspect, since the hologram pattern increases as the distance from the optical system increases, the amount of light receiving interference increases corresponding to the amount of light as the distance from the optical system increases. In the sixth aspect, the same wavelength interferes with the pattern recorded by the exposed wavelength. Therefore, for example, white light comes out in a pattern exposed with RGB wavelengths. In the structure of claim 7, the hologram lens itself and the liquid crystal panel are cooled by the cooling medium flowing between them. When the refractive index of this cooling medium is almost the same as the refractive index of the interface (glass substrate or the like) in contact with each other, reflection on that surface is suppressed.

[0010]

According to the structure of the first aspect, it is easy to allow parallel light to enter the liquid crystal panel by the flat parallel light generating panel, and a thin liquid crystal display device having a wide viewing angle is formed by the scattering type liquid crystal panel. To be done. Further, according to the structure of claim 2, the optical system can be made simple and the entire apparatus can be made compact. In the structures of claims 3 and 4, since it is sufficient to allow parallel light having a width to be incident on the side surface of the hologram lens having no thickness, it is possible to reduce manufacturing restrictions. According to the structure of claim 5, there is an effect of suppressing unevenness in the parallel light emerging from the hologram pattern. According to the sixth aspect, a well-balanced white color can be obtained, which is suitable for full-color display. In the structure of claim 7, heat generation due to light irradiation is suppressed to improve the reliability of the device, and unnecessary reflection is suppressed to improve display quality.

[0011]

EXAMPLES The present invention will be described below based on specific examples using the hologram lens 300. (First Embodiment) FIG. 1 is a schematic structural sketch showing a main part of a liquid crystal display device 100 of the present invention. The hologram lens 300 is arranged below the liquid crystal panel 200,
An optical system for irradiating the end lens side surface of the hologram lens is configured so that the light from the light source 7 having the reflector 6 is incident on the side surface of the hologram lens in parallel by the condenser lenses 8 and 9. ing. A slight gap is provided between the liquid crystal panel 200 and the hologram lens 300, and a mechanism (not shown) through which a cooling medium (cooling air or a cooling liquid having a refractive index similar to that of the substrate) can pass is provided. This is a means for preventing the hologram lens 300 and the liquid crystal panel 200 from generating heat due to the light from the light source 7 and preventing the interference conditions from shifting.

In the liquid crystal panel 200, a pixel electrode 2 made of a transparent ITO electrode is formed between transparent glass substrates 3 and 5, and is filled with a scattering type liquid crystal (PDLC) 4. The scattering type liquid crystal has a function of transmitting light when a voltage is applied to the pixel electrode 2, and the light cannot be seen only in the portion of the pixel electrode 2 to which the voltage is applied.

The hologram lens 300 is a photosensitive dry plate 1 made of gelatin or the like between transparent substrates 10 and 12.
1 is sandwiched and a predetermined hologram pattern (not shown) is printed. This hologram pattern is an interference fringe that diffracts incoming light and refracts or reflects it. Therefore, the dry plate 11 plays the role of the hologram lens itself. The hologram pattern is formed by exposing a dry plate to an interference pattern based on coherent light having a predetermined wavelength. Therefore, any wavelength interference pattern may be used. Since the visibility is good in black and white contrast, it is preferable to use parallel light of white light.

Since a structure intended to display an image on the front surface of the liquid crystal panel 200 is assumed here, the incident light is inclined by 4 ° or more with respect to the vertical direction of the hologram lens, It is configured so that it is diffracted and emerges so as to be reflected (reflected parallel light 14). Note that reflection is because the direction in which light is emitted after being diffracted is opposite to the incident direction of light from the light source, and the direction of diffraction is 9
It means a case of 0 ° or more, and does not mean to reflect like a mirror.

Here, as the hologram pattern, RG is used.
Interference fringes are printed so as to diffract the three primary colors of B.
That is, the hologram lens independently diffracts wavelengths of red, green, and blue, and the other wavelengths pass through the inside of the dry plate 11 without diffracting.
It has a characteristic that it passes through like No. 15 of. Therefore, the reflected parallel light 14 is white light and has a full-color component,
When the pixel electrode has a structure with a color filter, a full-color liquid crystal display device is obtained. In a normal pixel electrode,
It is a liquid crystal panel displaying white.

The light emitted from the light source 7 enters the condenser lens 8 either directly or after being reflected by the reflector 7.
The light is condensed by the condenser lens 8 and the condenser lens 9,
The arrangement is such that parallel light is incident on the side surface of the hologram lens 300. Light incident on the hologram lens 300 in parallel from the side is diffracted by the interference of the hologram lens, and becomes reflected parallel light 14 that travels in parallel in an oblique direction toward the liquid crystal panel 200, as shown in FIG. At this time, diffraction occurs at a specific wavelength corresponding to the hologram pattern.

The reflected parallel light 14 incident on the liquid crystal panel 200 in an oblique direction should be displayed in the front direction of the liquid crystal panel 200 (viewing direction 1 of the observer) for the purpose of using the liquid crystal panel 200. Therefore, parallel light cannot enter in the front direction of the liquid crystal panel 200, that is, in the vertical direction of the liquid crystal panel 200. Therefore, it cannot be displayed in the direction in which the parallel light is transmitted. However, depending on the purpose, it may be desired to display in an oblique direction, and in that case, the configuration may be such that the reflected parallel light 14 is diffracted perpendicularly to the liquid crystal panel 200.

In the structure shown in FIG. 1, the angle of incidence on the liquid crystal panel 200 was determined by the inventors to be 4
It became clear that this parallel light could not be recognized if it was tilted more than ° from the vertical direction. That is, the hologram pattern may be formed so that the reflected parallel light 14 from the hologram lens is diffracted at an angle of 4 ° or more with respect to the surface of the liquid crystal panel 200. Naturally, the larger this angle is, the more the recognition from the front is not performed, and the visual recognition angle of the display becomes wider. However, of course, it is at most 90 ° or less (in the case of 90 °, it does not enter the liquid crystal panel), and in the vicinity of 90 °, it is difficult to radiate from the hologram lens 300, and the liquid crystal panel 20
When entering 0, the reflection component on the surface of the glass substrate 5 increases, so that it is at least 45 ° or less from the vertical direction.

Although this incident angle is shown as being diffracted on a vertical plane including the incoming optical path in FIG. 1, the diffracted direction is not necessarily related to the incoming direction, and the hologram is not shown. It suffices that the angle from the direction perpendicular to the lens surface is the above value, and it is not necessary to diffract on the vertical plane including the optical path from the light source 7.

The reflected collimated light 14 obliquely incident on the liquid crystal panel 200 is as follows when no voltage is applied to the pixel electrode 2.
The light is scattered by the scattering type liquid crystal 4 in the area of the pixel electrode 2 and is scattered in a uniform direction with respect to the front surface of the liquid crystal panel 200 to become scattered light 13 (in the figure, for simplicity, the pixel electrode 2 It is drawn so that it may be scattered right above or on the panel surface). Then, when a voltage is applied to the pixel electrode 2, the orientation of the scattering type liquid crystal 4 in that region is changed and light is transmitted. Therefore, of the reflected collimated light 14 coming from the hologram lens, the light passing through the pixel electrode 2 to which the voltage is applied becomes the transmitted light and is not recognized by the observer (observer direction 1) of the liquid crystal panel 200. become. Therefore, contrast with other scattered electrode regions where no potential is applied is generated, and the image is recognized by an observer as an image.

As described above, since the hologram lens 300 can easily make parallel light incident on the liquid crystal panel 200 from an oblique direction, a liquid crystal display device having a simple optical system can be provided only by the flat hologram lens 300. Composed.

(Second Embodiment) Since the amount of light entering the hologram pattern from the optical system is reduced by the amount reflected and emitted by interference, it naturally decreases as the distance increases, and the optical system is installed. The light amount will be the least at the edge opposite to the side. Therefore, the emitted parallel light may also have a brightness distribution. This is a hologram pattern formed on the hologram lens and can be corrected to some extent, but if it is still inadequate, the layer having the hologram pattern (pattern layer) is formed into a thick and thin structure, and the structure as shown in FIG. Then, the liquid crystal panel 200
It is possible to provide parallel parallel light to.

The hologram lens 400 shown in FIG. 2 is shown here.
Shows that the dry plate for exposing the hologram pattern between the substrates 10 and 12 has a thin and thick structure including a thin layer portion 11a, an intermediate portion 11b, and the thickest portion 11c, and the side away from the optical system, that is, the thick portion 11c. Many hologram patterns are constructed. Therefore, the thin portion 11a forms a hologram pattern in the lower layer region of the hologram lens in a range of about 1/3 from the lower layer side, the intermediate portion 11b has a thickness range of from the lower layer to about 2/3, and the thick portion 11c is all formed. The hologram pattern is formed in the thickness of. Further, the width in the lateral direction is set to be approximately 1/3. If necessary, a finer thickness structure may be used, and the lateral distribution may be an appropriate non-uniform distribution.

With such a configuration, the parallel light incident from the side surface passes through the thin portion 11a with little interference at the beginning, and is mostly transmitted in the area away from the light source side. Collimated and reflected on the liquid crystal panel side
Give out. That is, in the thin portion 11a, about 1 / l of the incident amount
Some of the light quantity of 3 causes interference and is reflected, some of the light quantity of about 2/3 of the parallel light causes interference in the area 11b in the middle portion, and the parallel light over the entire hologram pattern layer in the thickest portion 11c. Some of them cause interference. In this way, the distribution of the reflected parallel light 14 can be made uniform.

(Third Embodiment) FIG. 3 is a schematic structural sectional view showing another means for making parallel light incident on the hologram lens 300. The optical prism 17 is provided below the end of the hologram lens 300. Is installed, and collimated light is made incident from one surface thereof. Although the optical system of FIG. 3 does not use a lens,
A light source optical system may be provided as necessary so that the light emitted from the light source 7 can be collimated.

The light emitted from the light source 7 is converted into almost parallel light by the reflector 6 and is incident on one surface 17a of the optical prism 17. The optical prism 17 is the substrate 10 of the hologram lens.
The parallel light incident from the surface 17a is incident on the substrate 10. Since the optical prism 17 and the glass substrate 10 are made of the same glass material and have substantially the same refractive index, refraction hardly occurs, and the optical prism 17 and the glass substrate 10 proceed as they are, and when they enter the dry plate 11 having the hologram pattern from the glass substrate 10,
Due to the difference in refractive index, the light is largely refracted and enters the dry plate 11 so as to be substantially parallel to the dry plate 11, as shown in FIG. However, it is not completely parallel to the dry plate 11, so that the substrate 10,
The reflection is repeated with an angle in a range between 12. Since this angle is within a substantially constant range if the optical prism 17 is determined, the hologram pattern also becomes parallel light in the same direction in each region of the hologram lens 300 corresponding to this incident angle. The pattern may be formed so as to be diffracted by the light. Such pattern formation is realized by using the same optical prism 17 as the pattern exposure optical system.

Since the incident parallel light has an angle within a certain range, the parallel light is also obliquely incident on the liquid crystal panel 200 at an angle having a certain spread. However, since the directions scattered by the pixel electrode 2 are almost uniform in all directions, they are sufficiently distinguished from the transmitted light transmitted in a certain angle range, and the recognition of the contrast on the front side of the liquid crystal panel 200 is affected. Absent.

The above two embodiments have been shown as means for making light incident on the hologram lens 300.
The method is not limited to the above-mentioned method, and may be a configuration in which light emitted from a light source is converted into parallel light and introduced into a parallel light generation panel such as a hologram lens. In addition, as the parallel light generating panel described in claim 1, there is a grating interference lens utilizing grating interference.

[Brief description of drawings]

FIG. 1 is a schematic configuration sketch of a liquid crystal display device using a hologram lens.

FIG. 2 is a schematic configuration sectional view of a hologram lens portion of a second embodiment.

FIG. 3 is a schematic configuration sectional view of a hologram lens portion of a third embodiment.

[Explanation of symbols]

 100 Liquid crystal display device 200 Liquid crystal panel 300 Hologram lens 400 Thick hologram lens 1 Viewing direction of observer 2 Pixel electrode 3 Substrate 4 Scattering liquid crystal (polymer dispersed liquid crystal, PDLC) 5 Substrate 6 Reflector 7 Light source 8, 9 Focusing Lens 10 Substrate 11 Dry Plate (Hologram Pattern) 12 Substrate 13 Scattered Light 14 Transmitted Light 15 Passed Light 17 Optical Prism

Claims (7)

[Claims] 1. A liquid crystal display device using a transmissive liquid crystal panel, comprising a parallel light generation panel on the back side of the liquid crystal panel for refracting light from a light source optical system to generate parallel light. A liquid crystal display device, wherein a generation panel makes the parallel light incident on the liquid crystal panel. 2. The liquid crystal display device according to claim 1, wherein the parallel light generating panel is a hologram lens. 3. The method according to claim 2, wherein the light source optical system is configured to introduce parallel light focused by an optical lens from a side surface of the hologram lens. 4. A structure in which the light source optical system introduces parallel light substantially parallel to a layer having a hologram pattern of the hologram lens by an optical prism provided on a lower surface of an end portion of the hologram lens. The method according to claim 2, wherein 5. The layer having the hologram pattern has a thick and thin structure having a thick portion and a thin portion in the thickness direction of the layer, and the hologram pattern is formed in a large number with increasing distance from the optical system. The liquid crystal display device according to any one of claims 2 to 4. 6. The liquid crystal display device according to claim 2, wherein the hologram pattern is a hologram pattern subjected to multiple exposure at an arbitrary wavelength. 7. The liquid crystal display device according to claim 1, having a structure in which a cooling medium is flown between the liquid crystal panel and the parallel light generating panel.