JPH09138396A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an observer to observe a display image at the lightest position by providing a reflecting plate which includes a diffracting and reflecting layer formed of a volume phase reflection type hologram and diffracts and reflects incident light to a direction deviating from a regularly reflecting direction. SOLUTION: The reflection type liquid crystal display device 1 consists of a liquid crystal panel 2 and the reflecting plate composed of the volume phase reflection type hologram 3 arranged behind the liquid crystal panel. The liquid crystal panel 2 modulates the incident light according to whether or not a voltage is applied to display switching between black and white. The volume phase reflection type hologram 3, on the other hand, is so constituted as to reflect monochromatic light of a specific wavelength range of the incident light 4 as reflected and diffracted light 6 to the direction different from the regularly reflecting direction 5 according to the pitch of interference fringes. The reflected and diffracted light 6 travels almost to an observation position 7 which is at a distance (a) from the surface of the liquid crystal panel 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be applied to an image display device using a reflection type liquid crystal panel such as a reflection type liquid crystal television, a reflection type liquid crystal monitor and the like, and particularly to a liquid crystal such as a calculator, a mobile phone, a pager and a device indicator. The present invention relates to a reflective liquid crystal display device capable of improving the visibility, brightness and contrast of a displayed image without increasing the power consumption of the device body in the display device.

[0002]

2. Description of the Related Art A reflection type liquid crystal display device has a reflector such as a light-scattering reflection plate or a reflection film on the back surface of a liquid crystal panel, and scatters and reflects incident light to observe a display image on the liquid crystal panel. It is configured to be visually recognized. Since this reflector displays a bright and high-contrast image, it is preferable that it has a high reflectance and a certain degree of directivity. Therefore, the conventional reflector is formed of a metal surface processed into a mat.

[0003]

However, in the case of the conventional reflector having a metal surface, the strongest reflected light is generated in the specular reflection direction of the incident light. Therefore, in the regular reflection direction, the reflected image of the illumination light source overlaps with the display image of the liquid crystal panel, and there is a problem that the visibility of the image is deteriorated. Therefore, conventionally, the image has to be observed in a direction slightly deviated from the regular reflection direction. Therefore, the conventional technique has a problem that a bright image cannot be observed. Further, the reflection type liquid crystal display device is often used for a meter display or an indicator of a device, and thus there is a problem that a color image display using a color filter cannot be adopted in terms of function and cost.

The present invention solves the above-mentioned problems, and separates the reflected image of the illumination light source and the display image from the viewpoint,
Another object of the present invention is to provide a reflective liquid crystal display device that allows an observer to observe a display image at the brightest position.

[0005]

In order to achieve the above object, the present invention provides a liquid crystal panel that modulates incident light according to an applied voltage and a modulated incident light that is arranged on the back surface of the liquid crystal panel. A reflection type liquid crystal display device comprising a reflection plate that emits light to the liquid crystal panel side, wherein the reflection plate includes a diffractive reflection layer composed of a volume phase reflection type hologram, and is arranged in a direction deviated from a regular reflection direction. The present invention constitutes a reflective liquid crystal display device that diffracts and reflects incident light. The diffractive reflective layer,
It is characterized by having a composite structure in which a plurality of volume phase reflection holograms having different spatial frequencies are multiplexed or multilayered and diffracting and reflecting white incident light. Further, the diffractive reflection layer is characterized in that a plurality of volume phase reflection holograms having different spatial frequencies are arranged in an area division manner, and incident light of different colors is diffracted and reflected at a partial portion to enable color display. To do. The reflection plate has a black layer on the back of the diffractive reflection layer, and absorbs an unnecessary portion of incident light that has not been diffracted and reflected. The volume phase reflection hologram has a function of limiting the diffraction reflection direction of incident light to a desired viewing area.

By providing a volume phase reflection hologram on the back surface of the liquid crystal panel, incident light is diffracted and reflected in a direction deviated from the specular reflection direction, and the reflected image of the illumination light source and the display image are visually separated. Therefore, the observer can observe the display image at the brightest position offset from the regular reflection direction without overlapping with the reflection image of the illumination light source. Further, by multiplexing or multi-layering volume phase reflection holograms having different spatial frequencies, a plurality of wavelength components are reflected and diffracted in a direction deviated from the regular reflection direction, so that an image of each color is bright and easy to see. To be observed. Further, by arranging the volume phase reflection type hologram in an area-divided manner corresponding to the pixels, for example, a color image as one pixel of the display image can be observed in the RCB3 region in a bright and easy-to-see state. Further, by forming a black layer on the back surface of the volume phase reflection type hologram, it is possible to absorb or attenuate unnecessary light such as transmitted light components that are not reflected and diffracted and reflected light on the back surface of the hologram to improve the contrast of image display. You can Further, by substantially matching the diffraction azimuth of the volume phase reflection hologram with the viewing range of the observer of the final product, the liquid crystal display device, the condensing power is substantially given to increase the brightness of the display image. You can

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a reflective liquid crystal display device according to the present invention will be described below in detail with reference to the drawings. FIG.
As shown in FIG. 3, the reflection type liquid crystal display device 1 of the present invention is composed of a liquid crystal panel 2 and a reflection plate composed of a volume phase reflection type hologram 3 arranged on the back surface thereof.

The liquid crystal panel 2 has a general structure and modulates the incident light according to the presence / absence of an applied voltage to perform switching display between white and black. On the other hand, as shown in the figure, the volume phase reflection hologram 3 reflects monochromatic light in a specific wavelength region of the incident light 4 in a direction different from the specular reflection light 5 in the specular reflection direction according to the pitch of the interference fringes recorded in advance. It is configured to reflect the diffracted light 6. The reflected diffracted light 6
Is an observation position 7 which is a distance a from the surface of the liquid crystal panel 2.
Is formed so as to almost face. Observation position 7
By observing with, it is possible to visually recognize a clear and bright image that does not overlap the light source image included in the specular reflection light 5.

FIG. 2 is a block diagram showing an optical system for producing the volume phase reflection hologram shown in FIG. The laser beam 9 from the argon laser 8 is split from the reflecting mirrors 10 and 11 by a beam splitter (BS) such as a half mirror 12. One of the split laser beams 9a is reflected by the reflecting mirror 13, the spatial filter (SF) 14 and the concave mirror 15 to form the reference beam 1
It becomes 6. On the other hand, the other split laser beam 9b passes through the reflection mirrors 17 and 18 and the spatial filter 19 and the reference beam 16
The illumination light 20 intersects with. The illumination light 20 illuminates a subject's diffuser plate 21 arranged correspondingly. A photosensitive material 22 is disposed in contact with the surface of the diffuser plate 21 on the reference light 16 side. With the above optical system, the volume phase reflection hologram 3 similar to the Lippmann hologram is formed on the photosensitive material 22. Interference fringes having a pitch depending on the irradiation angle of the reference beam 16 and the wavelengths of the laser beams 9a and 9b are formed on the volume phase reflection hologram 3. When the volume phase reflection hologram 3 is irradiated with reproduction light (incident light) which is conjugate with the reference light 16, reflected diffraction light deviated from the regular reflection angle in the direction based on the diffraction angle of the formed interference fringes is emitted. It

FIG. 3 shows a volume phase reflection hologram 3 for reflecting and diffracting red (R), green (G), and blue (B) light, respectively.
1 shows a reflection type liquid crystal display device 1a in which a volume phase reflection type hologram 3A having a composite structure having a, 3b and 3c is provided on a back surface of a liquid crystal panel 2. The volume phase reflection type hologram 3A is composed of three R, respectively produced according to the production method shown in FIG.
The G and B volume phase reflection type holograms 3a, 3b and 3c are adhered to each other to form a multilayer structure. As described above, the RGB components included in the white light are reflected and diffracted in a predetermined direction deviated from the regular reflection direction, so that a clear display image can be observed.

FIG. 4 shows volume phase reflection holograms having different spatial frequencies in the form of an array or a stripe (not shown).
3 shows a volume phase reflection type hologram 3B formed by arranging the holograms. Note that FIG. 4 is a plan view, in which volume phase reflection holograms 3a, 3b, and 3c of the three primary colors of red (R), green (G), and blue (B) are formed as one area, and the area is formed by one pixel. And a color image is formed corresponding to. That is, only the red color light is reflected and diffracted from the volume phase reflection hologram 3a in the red (R) area shown in the figure, and similarly the green color light from the green (G) area is converted into the blue (B) area. Only the light of blue color is reflected and diffracted from the area of, and the liquid crystal panel is turned on and off according to the RGB arrangement of the reflected light.
Full color image display is possible by making one pixel of the color display image in the R, G and B regions. That is, in this example, the volume phase reflection hologram also serves as a color filter.

FIG. 5 shows a reflection type liquid crystal display device 1b in which a black film 23 (or a black sheet) is attached to the back surface of the volume phase reflection type hologram 3 and integrated with the liquid crystal panel 2. Instead of the volume phase reflection hologram 3, the volume phase reflection holograms 3A and 3B described above may be used. By providing the black film 23, it is possible to improve the contrast of image display by absorbing or attenuating unnecessary light such as transmitted light components that are not reflected and diffracted and reflected light on the back surface of the volume phase reflection hologram 3 or the like. That is, in this example, the reflector has a structure in which the diffractive reflection layer formed of the reflection hologram 3 and the black layer formed of the black film 23 are stacked.

As described above, by using the volume phase reflection type holograms 3, 3A, 3B of the present invention, most of the incident light 4 is made the reflected diffracted light 6 in a predetermined direction deviated from the regular reflection direction. Although it is possible to obtain a bright and high-contrast display image, it is preferable that there is no reflected diffracted light 6 that is out of the viewing zone of the observation position 7. That is, the reflected diffracted light 6
It is desirable to condense the light in a certain range corresponding to the observer's visual range to increase the brightness of the display image. For this reason, the volume phase reflection holograms 3, 3A, 3B, etc. need to have a form in which the diffraction reflection direction of incident light is limited to a desired viewing area. 6 and 7 show an optical system for producing a volume phase reflection type hologram having such a limiting function. In this optical system, a Fresnel hologram using a diffusion plate as an object is produced in the first step, and then a Lippmann hologram is produced in the second step using this Fresnel hologram as a master hologram. Hereinafter, the optical system of FIGS. 6 and 7 will be described in detail.

As shown in FIG. 6, the diffuser plate 24 of the subject and the photosensitive material 25 are arranged facing each other with a distance a shown in FIG. Laser light 27 from the argon laser 26
Is divided by a half mirror 28. One of the split laser beams 27b becomes illumination light 33 through the reflecting mirrors 29, 30, 31 and the spatial filter 32, illuminates the diffuser plate 24, and the diffused object light 33a illuminates the photosensitive material 25. On the other hand, the other laser beam 27a split by the half mirror 28 is reflected by the reflecting mirror 34, the spatial filter 35, and the concave mirror 36.
The light becomes the reference light 37 and illuminates the photosensitive material 25. The reference light 37 intersects with the object light 33a. The Fresnel hologram 38 is formed on the photosensitive material 25 due to the interference between the object light 33 a and the reference light 37.

As shown in FIG. 7, the Fresnel hologram 38 is used as a master hologram 38a, and a photosensitive material 39 is arranged at a position separated from the master hologram 38a by a distance a. In addition,
The relationship between the master hologram 38a and the photosensitive material 39 is the diffusion plate 24 and the Fresnel hologram 38 shown in FIG.
Is the same as the relational position of, and is arranged facing each other and separated by a distance a. A mask plate 40 is arranged in contact with the surface of the master hologram 38a on the side of the photosensitive material 39.
Further, a color filter 41 is arranged on the surface of the photosensitive material 39 on the master hologram 38a side, if necessary.
The color filter 41 is necessary when the R, G, B volume phase reflection hologram shown in FIG. 4 and 3B are manufactured.

The laser light 43 from the argon laser 42 is split by the half mirror 44. One of the split laser beams 43a is reflected by the reflecting mirror 45, the spatial filter 46, and the concave mirror 4.
The illumination light 48 is transmitted through the master hologram 38a.
Is irradiated. On the other hand, the other split laser beam 43b passes through the reflection mirrors 49, 50 and the spatial filter 51, and the reference beam 52.
Then, the photosensitive material 39 is irradiated. The reproduction light 53 in a range corresponding to the opening area (not shown) of the mask plate 40 is emitted from the master hologram 38a irradiated with the irradiation light 48. Due to the interference between the reproduction light 53 and the reference light 52, a volume phase reflection hologram having a desired interference fringe is formed on the photosensitive material 39. The position where the volume phase reflection hologram is formed corresponds to the actual image position of the diffusion plate 24 in FIG. Further, when the position of the mask plate 40 in FIG. 7 is set as the observation position, it is possible to set the viewing zone in a range corresponding to the opening area limited by the mask plate 40. Further, the color filter 41 is the volume phase reflection hologram 3B shown in FIG.
It is used when manufacturing. Further, in the above description, the mask plate 40 is arranged immediately after the master hologram 38a, but it may be arranged immediately before.

Next, a concrete embodiment of the volume phase reflection hologram 3B shown in FIG. 4 and having a power for condensing light in a constant viewing area will be described. Using the optical system shown in FIG. 6, three Fresnel holograms 38 are prepared, one for each of red (R), green (G), and blue (B).
In this case, a laser light 27 of a helium neon laser having a wavelength of 632.8 [nm] is used for the red light source, and an argon ion laser of 514.5 [nm] is used for the green light.
Laser light 27 having a wavelength of 47.9 [nm] is used for blue light.
Was used. Opal glass was used as the diffuser plate 24 of the subject, and silver halide photosensitive materials for holograms for red, green, and blue manufactured by Agfa-Gewald were used as photosensitive materials.
Each time the wavelength of each laser light 27 is changed, another photosensitive material 2
5 is placed at a predetermined position, and three R, G, B master holograms 38a are recorded in the same procedure for the three wavelengths. In this case, since the distance a between the diffuser plate 24 and the photosensitive material 25 is directly related to the viewing area when the reflective liquid crystal display device 1 is finally observed, the most common observation when observing the liquid crystal display device is performed. The distance of 400 [mm] was set.
The size of the photosensitive material 25 was 8 inches × 10 inches, and the size of the diffusion plate 24 was 4 inches × 5 inches. After the exposure of the master hologram 38a, a CWC developing solution was used for development, and a PBQ2 bleaching solution was used for bleaching to perform development, bleaching, washing with water, and drying to produce respective master holograms 38a for R, G, and B. .

Next, the master hologram 38a is conjugated and reproduced by the optical system of FIG. 7 to form a real image of the diffusion plate 24, the photosensitive material 39 is placed at this real image position, and the reference light 52 from the back surface of the photosensitive material 52 is placed. And the real image reproduction light 53 of the diffusion plate 24 are caused to interfere with each other, and the volume phase reflection hologram 3 is photographed. As in the first step, the wavelengths of the laser light 43 are changed to R, G, B.
The exposure is performed three times by changing the three types, but in the case of the volume phase reflection hologram 3B shown in FIG. 4, one photosensitive material 39 is used.
Three types of holograms of R, G, and B are divided into areas in a pattern and exposed. Therefore, the color filter 41 for the liquid crystal television is arranged immediately before the photosensitive material 39. By the color filter 41, the light of each wavelength of R, G, B is transmitted through only the area of the color filter cell corresponding to that color, so that the photosensitive material 39 is arrayed in a pattern different for each of R, G, B. Exposure is performed. Photosensitive material 39
A full-color silver salt light-sensitive material was used as. Also, the size of the opening of the master plate 40 is 65 [m when the distance between both eyes of a human is
m], and 130 [mm], which is twice that, is taken in the horizontal direction and 100 [mm] which is slightly smaller in the vertical direction. The mask plate 40 having an opening of this size is used as the master hologram 38.
It was placed immediately after a. As described above, the volume phase reflection hologram 3B patterned into an array could be manufactured.

The present invention is not limited to the combination of wavelengths of laser light or the kind of photosensitive material described in the above embodiments, and the dimensions of each part are not limited to the above contents. Although the embodiment has described the method of manufacturing the volume phase reflection hologram 3B of FIG. 4, it is shown in FIG. 1 and FIG. 3 etc. by omitting operations such as array patterning and changing the wavelength of laser light. The thing can be similarly produced.

[0020]

According to the present invention, the following remarkable effects are obtained. 1) Since the light incident on the hologram is reflected and diffracted in a direction deviated from the direction of specular reflection, the reflected image of the illumination light source deviates from the display image, and the observer can observe the display image at the brightest position. 2) By multiplexing or layering volume phase reflection holograms having different spatial frequencies, white incident light can be diffracted and reflected in a specific direction deviated from the regular reflection direction,
A bright and easy-to-see display is possible. 3) The volume phase reflection holograms having different spatial frequencies are divided into areas according to the pixels and are arranged in an array or a stripe so that they can also serve as a color filter and a full color image can be displayed. 4) By attaching a black filter or sheet to the back surface of the hologram, the contrast of image display can be improved. 5) It is possible to increase the brightness of the display image by providing the reflection hologram with a power for condensing the light in a certain range corresponding to the visual field of the observer.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a reflective liquid crystal display device of the present invention.

FIG. 2 is a configuration diagram of an optical system for producing a volume phase reflection hologram of the reflection type liquid crystal display device shown in FIG.

FIG. 3 is a schematic diagram of a reflection type liquid crystal display device of the present invention in which a plurality of volume phase reflection type holograms are multilayered.

FIG. 4 is a plan view of a volume phase reflection hologram in which volume phase reflection holograms having different spatial frequencies are arranged in an array.

FIG. 5 is a schematic view of a reflective liquid crystal display device of the present invention in which a black film or a sheet is attached to the back surface of a volume phase reflection hologram.

6 is a configuration diagram showing an optical system in a first step for producing the volume phase reflection hologram shown in FIG.

FIG. 7 is a configuration diagram showing a second step optical system for producing the volume phase reflection hologram shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 reflective liquid crystal display device 1a reflective liquid crystal display device 1b reflective liquid crystal display device 2 liquid crystal panel 3 volume phase reflective hologram 3A volume phase reflective hologram 3B volume phase reflective hologram 3a volume phase reflective hologram 3b volume phase reflective type Hologram 3c Volume phase reflection hologram 4 Incident light 5 Regular reflection light 6 Reflection diffraction light 7 Observation position 8 Argon laser 9 Laser light 9a Laser light 9b Laser light 10 Reflecting mirror 11 Reflecting mirror 12 Half mirror 13 Reflecting mirror 14 Spatial filter 15 Concave mirror 16 Reference Light 17 Reflecting Mirror 18 Reflecting Mirror 19 Spatial Filter 20 Illuminating Light 21 Diffusing Plate 22 Photosensitive Material 23 Black Film 24 Diffusing Plate 25 Photosensitive Material 26 Argon Laser 27 Laser Light 27a Laser Light 27b Laser Light 28 Half Mirror 29 Reflecting Mirror 30 Reflection 31 Reflection mirror 32 Spatial filter 33 Illumination light 33a Object light 34 Reflection mirror 35 Spatial filter 36 Concave mirror 37 Reference light 38 Fresnel hologram 38a Master hologram 39 Photosensitive material 40 Mask plate 41 Color filter 42 Argon laser 43 Laser light 43a Laser light 43b Laser Light 44 Half mirror 45 Reflecting mirror 46 Spatial filter 47 Concave mirror 48 Illuminating light 49 Reflecting mirror 50 Reflecting mirror 51 Spatial filter 52 Reference light 53 Reproducing light

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tokuhiro Yasushi 1-5-1 Taito, Taito-ku, Tokyo Within Toppan Printing Co., Ltd. (72) Inventor Takashi Mizobuchi 1-5-1 Taito, Taito-ku, Tokyo Toppan Imprint Co., Ltd.

Claims (5)

[Claims] 1. A reflective liquid crystal display comprising a liquid crystal panel that modulates incident light in accordance with an applied voltage, and a reflection plate that is disposed on the back surface of the liquid crystal panel and reflects the modulated incident light to emit to the liquid crystal panel side. The device is a reflection type liquid crystal display device, wherein the reflection plate includes a diffractive reflection layer made of a volume phase reflection type hologram, and diffracts and reflects incident light in a direction deviated from a regular reflection direction. 2. The diffractive reflection layer has a composite structure in which a plurality of volume phase reflection holograms having different spatial frequencies are multiplexed or multilayered, and diffracts and reflects white incident light. The reflective liquid crystal display device described. 3. The diffractive reflection layer has a plurality of volume phase reflection holograms having different spatial frequencies arranged in an area-division manner, and diffracts and reflects incident light of different colors in partial portions to enable color display. The reflection type liquid crystal display device according to claim 1. 4. The reflection type liquid crystal display according to claim 1, wherein the reflection plate has a black layer on the back of the diffractive reflection layer and absorbs an unnecessary portion of incident light that has not been diffracted and reflected. apparatus. 5. The reflection type liquid crystal display device according to claim 1, wherein the volume phase reflection type hologram has a function of limiting a diffraction reflection direction of incident light to a desired viewing area.