JPH11258427A - Hologram reflector and reflection type liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflector using a volume phase reflection type hologram obtained by photographing and recording a hologram without using the diffused light by using the volume phase reflection type hologram having the angle selectivity for outgoing the parallel reflective diffraction light only to the parallel incident light at a specific angle. SOLUTION: The light transmitted through a polarization film 4 is entered into a hologram reflector 1. A liquid crystal panel 2 side of the hologram reflector 1 is a volume phase reflection type hologram 11 having the angle selectivity, and only the light entered with an angle same as that of the parallel light as a reference light in the photographing of the hologram, is emitted as the reflective diffraction light 6 as the parallel light at an angle same as that of the object light in the photographing. The most of incident light not agreed with the angle selectivity and wavelength selectivity of the hologram is transmitted as it is without diffracted. The light 7 transmitted through the hologram 11 is scattered and reflected by a metallic reflection layer 12 at the back of the hologram 11 to reach the observer's eyes as the pattern display light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device, and more particularly to a reflection type liquid crystal display device which does not require a special light source such as a backlight or an edge light, and a hologram reflector suitable for the same.

[0002]

2. Description of the Related Art A backlight is not required, and ambient light (illumination light or sunlight, which is light from an observer side) is reflected by a reflection layer (mainly a metal reflection layer) through a liquid crystal panel. 2. Description of the Related Art A reflective liquid crystal display device of a type in which display light according to a pattern displayed on a panel is made visible to an observer is known. A clock, a calculator, and the like are typical examples of the device. (See Fig. 1)

The reflection plate in the above-mentioned reflection type liquid crystal display device is a scattering reflection plate made of metal or resin, and it is difficult to see a bright image because the reflected light is diffusely reflected at a wide angle. Further, in the above-mentioned reflector, the intensity of reflected light is highest in the direction of regular reflection of incident light, so that the reflected light from the display device and the direction in which the reflection of the light source to be illuminated can be seen due to the cover glass on the device surface. There is a problem that the brightest directions overlap.

Attempts have been made to use a hologram so that the reflection angle and the like can be controlled in place of the existing scattering reflector. The following are known as proposals relating to a reflection type liquid crystal display device using a hologram as a reflection plate. (1) JP-A-56-51772 (2) U.S. Pat. No. 5,663,816 (Japanese Translation of PCT Application No. Hei 8-505)
716) (3) JP-A-9-138396 (4) JP-A-9-152586

There are various types of holograms, and the characteristics of the hologram reflector change accordingly.

(1) JP-A-56-51772 In the case of a surface relief hologram, it is difficult to increase the diffraction efficiency, so that it is difficult to see a bright display pattern and the hologram has a low chromatic dispersion. For this reason, the visual color changes according to the viewing direction. This corresponds to (1) above.

In the case of a volume phase reflection type hologram, the wavelength width reflected and diffracted by the wavelength selectivity is narrow and limited (a specific color is obtained), but an interesting visual effect in a specific color is realized. You. This corresponds to the above (2) (3) (4).

(2) US Pat. No. 5,663,816 (Japanese Unexamined Patent Publication No. Hei 8-505716) The above-mentioned (2) effectively diffuses ambient light having components in various directions to the reflection from the device. The hologram is photographed using diffused light that has passed through a diffuser such as frosted glass. In reproducing a hologram (observing a liquid crystal display device), a reflection diffraction pattern is reproduced with respect to diffused peripheral light corresponding to the diffused light. The above-mentioned (2) also discloses the idea of disposing a diffuse reflector on the back surface of the hologram so that diffuse peripheral light having a wavelength that is not reflected and diffracted by the wavelength selectivity of the hologram effectively contributes to reflection.

(3) JP-A-9-138396 discloses a volume phase reflection type in which incident light (peripheral light) incident on a display device is reflected and diffracted in a direction deviated from a regular reflection direction. It is described that a hologram is used.

(4) JP-A-9-152586 In the above (4), a diffuse reflection hologram that diffuses and reflects incident light (peripheral light) to a display device only in a direction predetermined as an observation area is used. Is described.

In any of the proposals (2), (3), and (4), when photographing a hologram, the angle selectivity of the hologram (light from a specific direction, which is determined according to the photographing conditions, is transmitted in a specific direction). Diffuse light is used in order to utilize the property of diffracting light out. That is, in (2), diffused light is used as reference light in order to design a hologram that reflects and diffracts incident light from multiple directions. (3)
In (4), diffused light (scattered light) is used as object light in order to define the direction and range in which light emitted from the display device (display light) is viewed bright.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hologram reflector using a volume phase reflection type hologram obtained by photographing and recording a hologram without using diffused light (scattered light). I do.

[0013]

According to a first aspect of the present invention, there is provided a hologram reflector having a volume having an angle selectivity such that parallel reflected diffraction light is emitted only for parallel incident light at a specific angle. It is characterized by using a phase reflection type hologram.

The hologram reflector according to the second aspect of the present invention is provided on one entire surface of a volume phase reflection type hologram having an angle selectivity such that parallel reflected and diffracted light is emitted only for parallel incident light at a specific angle. And a light reflection layer having a scattering reflection surface is formed.

According to a third aspect of the present invention, there is provided a hologram reflector having a volume phase reflection type having an angle selectivity such that only a specific area emits parallel reflected and diffracted light only for parallel incident light at a specific angle. A hologram is used.

The hologram reflector according to claim 4 is provided on one surface of a volume phase reflection type hologram having an angle selectivity such that parallel reflected and diffracted light is emitted only for parallel incident light at a specific angle. A light reflection layer having a scattering reflection surface is formed except for a specific region.

Further, the hologram reflector according to any one of claims 1 to 4 is arranged on a back surface of a liquid crystal panel,
A reflection type liquid crystal display device is obtained.

<Operation> A volume phase reflection type hologram having an angle selectivity such that parallel reflected and diffracted light is emitted only for parallel incident light at a specific angle is employed as a reflection plate in a reflection type liquid crystal display device. By doing so, it is possible to obtain a reflective liquid crystal display device that emits parallel reflected and diffracted light only for parallel incident light at a specific angle and allows a viewer to visually recognize a display pattern. (Claim 1,
5)

By forming a light reflecting layer having a scattering reflecting surface, light in a direction or a wavelength component that is not reflected and diffracted can be formed based on the angle selectivity and wavelength selectivity of the hologram.
The light can be scattered and reflected by the reflection layer, and by employing such a hologram reflection plate in a reflection type liquid crystal display device, incident light can be effectively contributed to reflection. (Claims 2 and 6)

The hologram reflector can be used in a liquid crystal display device by emitting parallel reflected and diffracted light only in a specific region of the hologram reflector only for parallel incident light at a specific angle. If applied, only a part of the display screen corresponding to the area will be restricted in the conditions under which the display light can be viewed, for example, only the person at a specific position can view the display information of the specific area. In addition, it is possible to make the display information of the specific area difficult for a surrounding person to see. (Claims 3, 4, 6)

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Embodiment 1> FIG. 2 is a schematic view showing a reflection type liquid crystal display device using a hologram reflection plate according to the present invention. The hologram reflection plate 1 is arranged on the back surface of the liquid crystal panel 2, and as shown in FIG. 1, a volume phase reflection hologram 11 having angle selectivity and a metal having a scattering reflection surface formed on one entire surface thereof. And a reflective layer 12.

In the figure, optical characteristics (optical paths of incident and reflected light)
Although the hologram 11 and the metal reflection layer 12 are shown separated from each other in order to schematically represent them, they may be integrated by lamination or vapor deposition. The case where the hologram 11 and the metal reflection layer 12 are integrated is related to the hologram reflection plate of claim 2, and when both are separate bodies, the hologram reflection plate of claim 1 is applied to a display device. Will be described.

Before and after the liquid crystal panel 2, a polarizing film 3,
4 are arranged respectively. When the ambient light 5 is incident on the liquid crystal display device from the outside, first, only the light of the polarization component in one direction reaches the liquid crystal panel 2 by the first polarizing film 3 and is rotated by the liquid crystal panel 2 according to the display pattern. Thereafter, the light reaches the second polarizing film 4.

The light transmitted through the second polarizing film 4 is incident on the hologram reflector 1, and the liquid crystal panel 2 side of the hologram reflector 1 is a volume phase reflection hologram 11 having angle selectivity. Only light incident at the same (conjugate) angle as the parallel light, which is the reference light at the time of shooting, is emitted as reflected diffracted light 6, which is parallel at the same angle as the object light at the time of shooting.

Most incident light that does not match the angle selectivity and wavelength selectivity of the hologram is transmitted through the hologram 11 without being diffracted. The light 7 transmitted through the hologram 11 is scattered and reflected by the metal reflection layer 12 on the back of the hologram 11, and transmitted again through the hologram 11, the polarizing film 4, the liquid crystal panel 2, and the polarizing film 3 to display a pattern on the observer's eyes. Light 20
To reach as.

The pattern display light 20 is composed of the diffraction light 6 reflected from the hologram reflection plate and the light scattered and reflected by the metal reflection layer 12.

When the hologram 11 is photographed, an optical system shown in FIG. 3 similar to the master photographing of the volume phase reflection type hologram (Lipman hologram) is used. After being oscillated from the laser light source 30 and branched into two, the object light 31 and the reference light 32, both of which are collimated, are made incident from the front and back of the photosensitive material 35 to be a hologram to cause interference and record a hologram. .

Since the angle selectivity of the hologram 11 is determined according to the conditions at the time of photographing, the intersection angle between the object light 31 and the reference light 32 is appropriately set in consideration of the use state of the liquid crystal display device. Is done.

<Second Embodiment> In the first embodiment, the same characteristics are described over the entire surface of the hologram reflector (the entire surface of the display screen when applied to a liquid crystal display device). In the embodiment, only a specific area of the hologram reflector has a large restriction on the condition under which the reflected diffracted light can be viewed, and other than the above-described area, it is completely the same as the first embodiment.

FIG. 4 is a schematic diagram showing an example of the liquid crystal display device from the front. Only a specific area 41 (the lower right hatched portion) in the display screen 40 can see the reflected diffracted light. This is an area where conditions are large.

Such an area can be set as follows. (A) At the time of photographing a hologram, only a portion of the photosensitive material that hits the region is recorded with holograms using parallel light from the front and back. A mask is applied only to that part, and hologram recording using diffused light is made to other parts. (B) A metal reflection layer having a scattering reflective surface only on one surface of the hologram 11 of the first embodiment and a portion corresponding to that region
12 is not provided. (Or, part is removed from the metal reflection layer 12 on the whole surface.)

When such a hologram reflector is applied to a liquid crystal display device, it is conceivable that information displayed only in a specific area of the screen has concealment. That is, when parallel light from a specific angle enters the display device,
Only the person at the specific position can visually recognize the display information of the specific area, and it is possible to make the display information of the specific area hard to be seen by surrounding people.

[0033]

When applied to a reflection type liquid crystal display device,
In a hologram reflector that realizes an interesting visual effect in a specific color, a novel configuration is provided by hologram imaging without using diffused light, and a hologram reflector with the following more interesting visual effects is provided. . (1) When parallel light from a specific angle is incident using external illumination light such as a searchlight, since diffracted light having a high intensity, which is parallel light in a specific direction, is emitted, a specific position (direction) is used. A bright display is possible only for the observer. (2) When a bright display is not required only at a specific position (direction), even if external illumination light such as a searchlight is not used, among ambient light, rays that do not match parallel light from a specific angle can be used. However, normal display by generating scattered reflected light is possible. (3) The restriction on the condition under which the reflected diffracted light can be viewed only in a specific region of the hologram reflector is increased (the reflected diffracted light is reflected in a specific direction only for incident parallel light at a specific angle). By causing the parallel light to be emitted), it is possible to make the display information of the region visible only to the observer at a specific position (direction), and to make it difficult for other observers to see.

[0034]

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a conventional reflection type liquid crystal display device using a diffuse reflection layer.

FIG. 2 is an explanatory view showing an example of a reflection type liquid crystal display device according to the present invention.

FIG. 3 is an explanatory view showing a hologram imaging optical system.

FIG. 4 is an explanatory view showing an example of a reflection type liquid crystal display device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hologram reflection plate 2 ... Liquid crystal panel 3, 4 ... Polarizing film 5 ... Ambient light 11 ... Volume phase reflection type hologram 12 ... Light reflection layer which has a scattering reflective surface

Claims (6)

[Claims] 1. Only for parallel incident light at a specific angle,
A hologram reflection plate using a volume phase reflection hologram having angle selectivity so as to emit parallel reflected diffraction light. 2. Only for parallel incident light at a specific angle,
A hologram reflector, wherein a light reflection layer having a scattering reflection surface is formed on one entire surface of a volume phase reflection hologram having an angle selectivity such that parallel reflected diffraction light is emitted. 3. A volume phase reflection hologram having an angle selectivity such that only a specific region emits parallel reflected and diffracted light only for parallel incident light at a specific angle. Hologram reflector. 4. Only for parallel incident light at a specific angle,
A light reflection layer having a scattering reflection surface is formed on one surface of a volume phase reflection hologram having an angle selectivity such that parallel reflection diffraction light is emitted, except for a specific region. Hologram reflector. 5. A reflection type liquid crystal display device, wherein the hologram reflection plate according to claim 1 is arranged on a back surface of a liquid crystal panel, and further, a light reflection layer having a scattering reflection surface is arranged on the back surface. 6. A reflection type liquid crystal display device, wherein the hologram reflection plate according to claim 2 is arranged on a back surface of a liquid crystal panel.