JPH10142424A - Hologram reflecting plate and reflection type liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the hologram reflecting plate which can control light which is reflected and diffracted and has wide wavelength width and high diffraction efficiency so that a light display is made in a predetermined direction by arranging a reflection layer on the back of a volume phase transmission type hologram (hologram lens) having a light converging function. SOLUTION: The reflection type liquid crystal display device has a hologram reflection plate arranged on the back of a liquid crystal panel 2 and consists of the volume phase transmission type hologram which has angle selectivity, a hologram lens 6, and a metal reflecting layer 8. Illumination light 5 after being rotated and polarized by the liquid crystal panel 2 according to a display pattern is made incident on a hologram reflecting plate. The incident light 7 is transmitted through the hologram lens 6 as it is without being diffracted, scattered and reflected by the metal reflecting layer 8, and made incident on the hologram lens 6 again. This incident light 9 matches the angle selectivity that the hologram lens 6 has and is transmitted and diffracted. The transmitted and diffracted light reaches the eye 11 of an observer as pattern display light 10.

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 capable of displaying a brighter image than conventional ones without being restricted by observation conditions, and a hologram reflector used therein.

[0002]

2. Description of the Related Art A structure in which a reflective layer is provided on the back surface of a liquid crystal panel, in which a pattern-like reflected light caused by light from the observer side (indoor light or external light such as sunlight) is viewed without a backlight. 2. Description of the Related Art A reflection type liquid crystal display device is known, and in recent years, it has been attempted to use a reflection type hologram as a reflection layer in the display device instead of an existing metal reflection layer. By using a reflection hologram,
The viewing zone and the reflection direction can be specified, and bright display in a specific direction can be achieved as compared with the metal reflection layer.

However, when the reflection hologram to be used is a surface relief hologram, it is difficult to increase the diffraction efficiency, and furthermore, the color displayed according to the observation direction depends on the color dispersion of the hologram. There is a problem that it is changed and seen. Further, in the case of a volume phase reflection type hologram, since the wavelength width of reflection and diffraction due to its wavelength selectivity is narrow, colored (specific color other than white or silver) reflected light can be seen or visible wavelength region can be observed. However, there is a problem that it is difficult to realize a bright display over a wide range.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a reflection type liquid crystal display device using a hologram as a reflection layer instead of a metal reflection layer. An object of the present invention is to provide a control hologram reflector capable of performing control so as to display a bright image in a different direction, and a reflection type liquid crystal display device using the same.

[0005]

According to the present invention, a volume phase transmission hologram (hereinafter, referred to as a hologram lens) having a condensing function is employed as a hologram, and a reflection layer is disposed on the back surface of the hologram. A hologram reflector is used as a reflection layer.

<Operation> By adopting a configuration in which a reflection layer is disposed on the back surface of a volume phase transmission type hologram, the hologram reflector has a high diffraction efficiency (reflectance of external light) and a wide wavelength range for diffraction. It is possible to perform a bright display within a certain range according to the light collecting function of the hologram lens. (Claim 1) Here, since the hologram is a volume phase transmission hologram having angle selectivity, incident light (or light reflected from the reflection layer) undergoes transmission diffraction by the hologram, and as a result, the incident light becomes positive. Since the reflected light is emitted in a direction different from the reflection direction, it is not necessary to be conscious of the image of the light source of the incident light due to the reflection on the hologram surface, and the viewing zone and the reflection direction can be specified. Angle selectivity is an optical property of a hologram that emits diffracted light at a specific angle (direction) only for incident light from a specific angle (direction),
The specific angle (direction) is determined according to the conditions at the time of recording and recording the hologram.

[0007] A plurality of different types of hologram lenses,
Incident light that contributes to reflection (by being recorded multiple times on the same photosensitive material, integrated by superposition, or divided into the same photosensitive material by pattern division and recorded) Observation conditions under which bright reflected light can be seen increase, such as less restrictions on the direction of external light), or that the observer can sufficiently see the reflected light even if the observer moves the viewpoint. (Claims 2, 3,
4)

In this case, the following two meanings are considered as “a plurality of different types of hologram lenses”. (1) With respect to the same reproduction illumination light, a plurality of types of diffracted lights having different focal positions are emitted. (2) Diffracted light is emitted at the same focal position for different reproduction illumination light.

When the whole is in the form of a film, the work of incorporating the hologram reflector into the liquid crystal display device becomes easy. (Claim 5)

When the reflection layer has a scattering reflection surface,
The range in which the reflected light is condensed can be widened, and a bright display can be achieved within a certain widened range without limiting the viewing area (reflection direction) to a limited narrow range. (Claim 6)

By forming a polarizing layer on the surface of the hologram opposite to the reflecting layer, the polarizing layer functions as a protective layer of the hologram and, when incorporated in a liquid crystal display device, a polarizing layer necessary for a liquid crystal panel. Can also be used.
(Claim 7)

[0012]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is a schematic view showing a reflection type liquid crystal display device using the hologram reflection plate of the present invention. The hologram reflection plate 1 is disposed on the back surface of the liquid crystal panel 2 and, as shown in FIG. 1, includes a hologram lens 6 composed of a volume phase transmission hologram having angle selectivity and a metal reflection layer 8 having a scattering reflection surface. Be composed. In the figure, the hologram lens 6 and the metal reflection layer 8 are shown separated from each other in order to schematically represent optical characteristics (optical paths of incident and reflected light), but they are integrated by lamination or vapor deposition. The same applies to the following description.

Before and after the liquid crystal panel 2, a polarizing film 3,
4 are arranged respectively. When the illuminating 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 reflection plate 1, and the hologram reflection plate 1 has a hologram lens 6 made of a volume phase transmission hologram having angle selectivity on the liquid crystal panel 2 side. The incident light is transmitted through the hologram lens 6 without being diffracted by the hologram lens 6 due to the angle selectivity. The light 7 transmitted through the hologram lens 6 is scattered and reflected by the metal reflection layer 8 on the back surface of the hologram lens 6, and then enters the hologram lens 6 again. The incident light 9 enters the hologram lens 6 at an incident angle opposite to that of the first incident light 7 and is transmitted and diffracted in accordance with the angle selectivity of the hologram lens 6.

The transmitted diffracted light travels so as to be condensed at the focal position F of the hologram lens 6, passes through the polarizing film 4, the liquid crystal panel 2, and the polarizing film 3 again, and becomes the eye 11 of the observer.
Arrives as the pattern display light 10.

Although FIG. 1 shows that the pattern display light 10 is condensed only at the point F, the pattern display light has a spread because the metal reflection layer 8 has a scattering reflection surface. As a result, the range in which the pattern display light can be seen brightly can be expanded. When it is desired to condense light without spreading, it is not necessary to provide the metal reflection layer 8 with a scattering reflection surface, and it may be a mirror surface.

<Embodiment 2> FIG. 2 is a schematic view showing an embodiment of a reflection type liquid crystal display device in which the angle selectivity of the hologram lens 6 is different from that of the above embodiment (FIG. 1). The configuration is the same as in FIG.

In the first embodiment, the incident light is transmitted without being diffracted by the hologram lens 6 due to the angle selectivity of the hologram. In the present embodiment, the incident light is transmitted and diffracted by the hologram lens 6. Thereafter, the light reaches the metal reflection layer 8 having the scattering reflection surface.

As described above, the angle selectivity is desirably variable according to the conditions at the time of recording and recording the hologram. In the case of the present embodiment, the light incident on the hologram lens 6 is diffracted, The hologram is photographed and recorded under such a condition that the light reflected from the hologram lens 6 is not diffracted.

The scattered and reflected light 9 scattered and reflected by the metal reflection layer 8 and incident on the hologram lens 6 again is the first incident light 5
Since the positive and negative are opposite incident angles, the transmitted light reaches the observer's eyes 11 as the pattern display light 10 after being transmitted as it is without being diffracted by the hologram lens 6.

In this embodiment, the scattered reflected light 9 is condensed via the metal reflection layer 8 at a position (mirror virtual image F *) symmetrical to the original focal position F (not shown) of the hologram lens 6. Will be reflected.

Although FIG. 2 shows that the pattern display light is reflected and condensed only at the point F *, the pattern display light spreads because the metal reflection layer 8 has a scattering reflection surface. Therefore, the range in which the pattern display light can be seen brightly can be expanded. As in the first embodiment, when it is desired to condense light without spreading, it is not necessary to provide the metal reflection layer 8 with a scattering reflection surface.
It may be a mirror surface.

Third Embodiment FIG. 3 shows a hologram lens in which two different hologram lenses are multiplex-recorded on the same hologram as a volume phase transmission hologram composed of two different interference fringes 12 and 13. It is explanatory drawing which shows an example of 6 typically.

Each of the hologram lenses 12 and 13 receives object light 14 and 15 (object light such that light from a point light source spreads and irradiates a photosensitive material) at the time of photographing and recording. Recorded by interference with the material.

When the hologram lens 6 is reproduced, a focus position corresponding to the optical path of the object light during photographing and recording (the position of the point light source during photographing and recording) with respect to incident light (external light) conjugate with the reference light during recording. ) Are transmitted and diffracted.
As described above, the reflected light is emitted from the hologram reflector so as to be condensed at the positions of the mirror surface virtual images.

As another example of multiplex recording, a single object beam is made to interfere with reference light from a plurality of directions by a photosensitive material, so that two different types of hologram lenses can be combined with two different types of interference fringes. It is also possible to manufacture the hologram lens 6 recorded as the transmission holograms 12, 13. (Not shown)

When the hologram lens 6 is reproduced, one condensing diffracted light is transmitted and diffracted with respect to incident light (external light) from a plurality of directions conjugate to the reference light at the time of recording. The reflected light is emitted from the hologram reflector so as to be condensed at the position of the mirror surface virtual image.

In any of the multiplex recordings described above, the observation conditions under which the hologram reflector can view bright reflected light increase.

The method of manufacturing a plurality of different types of hologram lenses is not limited to multiplex recording, but the same can be realized by superposition of hologram lenses or multiplex recording in which a region is divided in a pattern.

FIG. 4 is a graph comparing the reflected light amount distribution 17 of the reflection type liquid crystal display device using the existing metal reflective layer with the reflected light amount distribution 17 using the hologram reflector of the present invention. It is. As shown in the figure, in the metal reflective layer (graph 16), the intensity of the reflected light in the specular reflection direction is the strongest, and weakens in a normal distribution manner toward the periphery. On the other hand, in the hologram reflector (graph 17) of the present invention, the viewing area can be controlled so as to be centered on the converging direction of the hologram lens.

FIG. 5 is an explanatory diagram showing a comparison between the spectral diffraction efficiency of the volume phase reflection hologram (graph 18) and the spectral diffraction efficiency of the volume phase transmission hologram (graph 19).
The diffraction efficiency and the diffraction wavelength width of the volume phase hologram are
It mainly depends on the film thickness of the photosensitive material on which the hologram is recorded, the spatial frequency of the interference fringes recorded and the degree of refractive index modulation. When the parameters of the photosensitive material described above are the same, as shown in the figure, the diffraction wavelength width of the transmission hologram 19 is clearly wider than that of the reflection hologram 18, and therefore, the volume phase reflection hologram is used for the volume phase reflection hologram. It becomes a reflector that is several times brighter than the hologram.

In order to obtain a wide diffraction wavelength width similar to that of a volume phase transmission hologram in a volume phase reflection hologram, the refractive index modulation degree must be several times that required in a transmission type hologram. The required performance becomes severe and is not realistic. It is a known matter in the art that the diffraction wavelength width of the volume phase transmission hologram is wider than that of the volume phase reflection hologram, and detailed description is omitted in this specification.
E BELL SYSTEM TECHNICAL JOURNAL, November 1969,
Volume 48, Number 9 ".

The volume phase transmission type hologram employed in the present invention can be recorded by a normal two-beam hologram photographing optical system using a volume phase type hologram photosensitive material.

As the photosensitive material, gelatin dichromate, a silver salt photosensitive material, a photopolymer, or the like can be used. In the present invention, a silver salt photosensitive material for hologram 8E manufactured by AGFA is used.
56 films were used.

As a laser as a light source, an argon ion laser (wavelength: 514.5 nm) was employed. Of the two light beams used for recording and recording the hologram, the divergent light spread from the point light source is used as the object light, and the parallel light is used as the reference light. Was. Aluminum was deposited as a reflective layer on the back surface side of the hologram (a foil-like aluminum having a scattering reflection surface may be laminated) to obtain a hologram reflector of the present invention.

The above description relates to a hologram that is photographed and recorded by two-beam interference. A hologram that is formed by drawing a desired hologram lens with an EB lithography device or the like is used as a master hologram to form a volume phase transmission hologram by a contact copy method or the like. It is also possible.

[0037]

In a reflection type liquid crystal display device using a hologram as a reflection layer instead of a metal reflection layer, by using a hologram lens, it is easy to control a reflection direction and a light condensing range that enable bright display. Become.

[0038]

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a reflection type liquid crystal display device using a hologram reflection plate of the present invention.

FIG. 2 is a schematic view showing another embodiment of the reflection type liquid crystal display device using the hologram reflection plate of the present invention.

FIG. 3 is an explanatory diagram illustrating an example of a hologram lens in which a plurality of different types of hologram lenses are multiplex-recorded.

FIG. 4 is a graph comparing a reflected light amount distribution 17 of a reflective liquid crystal display device using an existing metal reflective layer with a reflected light amount distribution 17 using a hologram reflector of the present invention.

FIG. 5 is an explanatory diagram showing a comparison between the spectral diffraction efficiency of a volume phase reflection hologram (graph 18) and the spectral diffraction efficiency of a volume phase transmission hologram (graph 19).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hologram reflection plate 2 ... Liquid crystal panel 3, 4 ... Polarizing film 5 ... Illumination light 6 ... Hologram lens 7, 9 ... Light incident on a hologram 8 ... Metal reflection layer 10 ... Pattern display light 12, 13 ... Different hologram lenses 14, 15: Object light at the time of recording and recording of the hologram lens 16: Graph showing the reflected light amount distribution of the liquid crystal display device using the metal reflection layer 17 ... Graph showing the reflected light amount distribution of the liquid crystal display device using the hologram reflector 18 … Spectral diffraction efficiency of volume phase reflection hologram 19… Spectral diffraction efficiency of volume phase transmission hologram

Claims (8)

[Claims] 1. A hologram reflector comprising a structure in which a reflection layer is arranged on the back of a volume phase transmission hologram having a condensing function. 2. The hologram reflector according to claim 1, wherein a plurality of different types of said holograms are multiplex-recorded on the same photosensitive material. 3. The hologram reflector according to claim 1, wherein the hologram is of a configuration in which a plurality of different types of holograms are superimposed. 4. The hologram reflection plate according to claim 1, wherein a plurality of different types of said holograms are recorded in the same photosensitive material while being divided into regions in a pattern. 5. The hologram reflector according to claim 1, wherein the hologram and the reflection layer have a film-like structure in which the hologram and the reflection layer are integrated. 6. The hologram reflector according to claim 1, wherein the reflection layer disposed on the back surface of the hologram has a scattering reflection surface. 7. The hologram reflector according to claim 1, wherein a polarizing layer is formed on the surface of the hologram opposite to the reflection layer. 8. A reflection type liquid crystal display device comprising the hologram reflection plate according to claim 1 arranged on the back surface of a liquid crystal panel.