JPH1054911A - Hologram reflection plate and reflection type liquid crystal display device using the plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embody a bright display by using a hologram reflection plate constituted by adopting a volume phase transmission type hologram having angle selectivity as a hologram and arranging a reflection layer on the rear surface of a hologram as a reflection layer. SOLUTION: The light transmitted through a polarizing film 4 of a second sheet is made incident on the hologram reflection plate 1 but the liquid crystal panel 2 side of the hologram reflection plate 1 is the volume phase transmission type hologram 6 having the angle selectivity and the incident light is transmitted through the hologram 6 as it is by the angle selectivity without being diffracted. The light 7 transmitted through the hologram 6 is specularly reflected by the metallic reflection layer 8 on the rear surface of the hologram 6 and is again made incident on the hologram 6. The incident light 9 is made incident on the hologram 6 at the incident angle reverse in positive and negative from the incident light 7 at the first time and is alighted to the angle selectivity possessed by the hologram 6, by which the light is transmitted and diffracted at the specific angle. This diffracted light 10 transmits again the polarizing film 4, the liquid crystal panel 2 and the polarizing film 3 and arrives at the observer's eyes 11.

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 performing brighter display than before and suitable for color display, and a hologram reflector used therein.

[0002]

2. Description of the Related Art A reflection type liquid crystal display device having a reflection layer on the back surface of a liquid crystal panel is known. In recent years, in such a display device, a reflection type hologram is used instead of an existing metal reflection layer. It has been attempted to be used as By using the reflection hologram, the viewing area and the reflection direction can be specified, and a brighter 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. When the hologram is a volume phase reflection hologram, the wavelength to be reflected and diffracted due to its wavelength selectivity. Since the width is narrow, there are problems that the reflective layer is colored and it is difficult to realize a bright display over a visible wavelength range. Furthermore, there is also a problem that, due to the chromatic dispersion, the displayed color changes depending on the viewing direction and is visually recognized due to the characteristics of the hologram itself.

When a color display is performed on a liquid crystal display device, a color filter such as a pigment dispersion type, which is well known in the art, is used in combination with a liquid crystal panel. In the display device, the brightness of the display is reduced due to absorption by the color filter or the like, and the problem of cost increase due to the use of the color filter also occurs.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a reflection type liquid crystal display device which uses a hologram as a reflection layer instead of a metal reflection layer, and which can realize a bright display (particularly a bright color display). It is an object to provide a reflection plate and a reflection type liquid crystal display device using the same.

[0006]

According to the present invention, a volume phase transmission hologram having an angle selectivity is employed as a hologram, and a hologram reflector having a structure in which a reflection layer is arranged on the back surface of the hologram is used as the reflection layer. I do.

[0007]

With the configuration in which the reflection layer is disposed on the back surface of the volume phase transmission type hologram, the hologram reflection plate as a whole has a high diffraction efficiency and a wide wavelength range for diffraction. In particular, since the hologram is a volume phase transmission hologram having angle selectivity, incident light (or reflected light from the reflective layer) undergoes transmission diffraction by the hologram, and as a result, the incident light has a regular reflection direction. Since the reflected light is emitted in different directions, 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. (Claim 1)

Here, the angle selectivity is an optical characteristic 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.

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 2) Further, 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 is necessary for a liquid crystal panel when a liquid crystal display device is incorporated. It can also serve as a polarizing layer. (Claim 8)

The hologram composed of a plurality of types of interference fringes having different spatial frequencies is integrated by multiplex recording or superimposition, so that the influence of hologram chromatic dispersion is reduced and observation from different directions is possible. In contrast, there is little change in the color diffracted and reproduced from the hologram. (Claims 3 and 4)

[0011] With the configuration in which the holograms composed of a plurality of types of interference fringes having different spatial frequencies are arranged in a specific pattern, light of different wavelengths (colors) is diffracted according to the pattern (hologram). The hologram reflector also functions as a color filter. (Claim 5)

The hologram reflecting plate in which the hologram forms a lens array is arranged on the back surface of the liquid crystal panel such that the focal position of each hologram lens array is at the position of the liquid crystal panel. Light loss due to the light shielding pattern (black matrix) can be suppressed. (Claims 6 and 10)

[0013]

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 is composed of a volume phase transmission hologram 6 having angle selectivity and a metal reflection layer 8, as shown in FIG. In the figure, the hologram 6 and the reflection layer 8 are shown separated from each other in order to schematically represent optical characteristics (optical paths of incident and reflected light). However, even if both are integrated by lamination or vapor deposition. It does not matter, and 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. The liquid crystal panel 2 side of the hologram reflection plate 1 is a volume phase transmission hologram 6 having angle selectivity. Due to the angle selectivity of 6, the incident light passes through the hologram 6 without being diffracted.
The light 7 transmitted through the hologram 6 is specularly reflected by the metal reflection layer 8 on the back surface of the hologram 6, and is incident on the hologram 6 again. The incident light 9 is incident on the hologram 6 at an incident angle opposite to that of the first incident light 7, matches the angle selectivity of the hologram 6, and is transmitted and diffracted as a diffracted light 10 at a specific angle. The diffracted light 10 passes through the polarizing film 4, the liquid crystal panel 2, and the polarizing film 3 again, and reaches the eyes 11 of the observer as pattern display light.

<Embodiment 2> FIG. 2 shows a reflection type hologram 6 in which the angle selectivity of the volume phase transmission type hologram 6 is different from that of the above-mentioned embodiment (FIG. 1) and the metal reflection layer 8 has a scattering reflection surface. FIG. 2 is a schematic diagram illustrating an embodiment of a liquid crystal display device, and other configurations are the same as those in FIG. 1.

In the first embodiment, the incident light is transmitted without being diffracted by the hologram 6 due to the angle selectivity. In this embodiment, the incident light is transmitted and diffracted by the hologram 6 and then reflected by the metal. The layer 8 is reached. As mentioned above,
The angle selectivity is desirably variable depending on the conditions at the time of recording and recording of the hologram.
The hologram is photographed and recorded under such a condition that light in the direction of incidence on the hologram is diffracted and light in the direction reflected from the hologram 6 is not diffracted.

The incident light 9 scattered and reflected by the metal reflection layer 8 and incident on the hologram 6 again has the opposite sign to the first incident light 5 and has a different incident angle. After that, the light reaches the observer's eyes 11 as transmitted light 10 as pattern display light. By making the angle selectivity of the hologram 6 as described above and providing the metal reflection layer 8 with a scattering reflection surface, the pattern display light reaches the observer in a range wider than in the first embodiment.

<Embodiment 3> FIG. 3 shows a volume phase transmission type hologram 1 composed of three types of interference fringes having different spatial frequencies.
FIG. 2 is a schematic diagram showing an embodiment of a reflective liquid crystal display device in a case where 2, 13, and 14 are configured to be superimposed. Each volume phase transmission hologram is designed to transmit and diffract red, green and blue light, and the angle selectivity is such that incident light is transmitted and diffracted by the hologram as in the second embodiment. The metal reflection layer 8 has a scattering reflection surface.

According to the chromatic dispersion characteristics of the hologram,
By combining three types of holograms so that the diffraction angles of the three color lights match so that the diffraction angle does not change according to the color, when the display device is observed, it is displayed depending on the viewing angle. The color does not change. Note that the present embodiment is not limited to the above, and the same operation and effect can be obtained even when a volume phase transmission hologram composed of a plurality of types of interference fringes is multiplex-recorded on one photosensitive material. You.

<Embodiment 4> FIG. 4 is a front view showing a hologram reflector according to claim 4 (a configuration in which the hologram composed of a plurality of types of interference fringes having different spatial frequencies is arranged in a specific pattern). FIG. As shown in the figure, volume phase transmission holograms with different spatial frequencies
22, 23, and 24 are arranged in an array in a specific pattern (in the figure, a stripe pattern), and three adjacent hologram cells 22, 23, and 24 transmit and diffract red, green, and blue, respectively. ing. The figure is an example of a specific pattern, and the hologram reflector of the present invention is not limited to the illustrated pattern. Alternatively, other patterns can be used.
Alternatively, as shown in FIG. 5, three types of holograms 25, 26, and 27 may be arranged as a specific pattern so as to correspond to a circle, a square, and a triangle, respectively, so that each figure is observed in a different color. good. In this way, it is also possible to display a specific character or figure colored in a specific color.

<Embodiment 5> FIG. 6 is a schematic view showing a reflection type liquid crystal display device using a hologram reflector (the hologram forms a lens array) according to the fifth aspect.
As shown in the figure, the volume phase transmission type hologram 15 is a hologram lens array, and the size of one hologram lens is equivalent to three liquid crystal pixel cells of the liquid crystal panel 16.

The incident light 17 is first transmitted through the hologram 15 without being diffracted by the hologram 15 due to the angle selectivity of the volume phase transmission type hologram lens array 15, and is specularly reflected by the reflection layer 18. The light is diffracted and condensed by the array 15. However, since this diffraction position differs in diffraction angle depending on the wavelength, chromatic dispersion occurs, and as shown in the figure, the liquid crystal panel
Disperse on 16 Therefore, the three adjacent liquid crystal panels 16
Light of three different colors, such as red, green, and blue, enters one liquid crystal pixel cell 19, 20, and 21, and each of the liquid crystal pixel cells rotates the polarization direction corresponding to the color to produce a color. Display is enabled. The figure shows one of the hologram lens arrays.
By way of example, the hologram reflector of the present invention is not limited to the illustrated patterns and the number of colors.

<Embodiment 6> FIG. 7 shows a reflection type liquid crystal display device in which the angle selectivity of the volume phase transmission type hologram 15 is different from that of Embodiment 5, and the metal reflection layer 18 has a scattering reflection surface. FIG. 7 is a schematic diagram illustrating the embodiment, and other configurations are the same as those in FIG. 6. Volume phase transmission hologram 15
Is a hologram lens array, and the size of one hologram lens is equivalent to three liquid crystal pixel cells of the liquid crystal panel 16.

The incident light 17 is first diffracted and transmitted by the angle selectivity of the volume phase transmission type hologram lens array 15 and scattered and reflected by the reflection layer 18, and then the volume phase transmission type hologram lens array 15 is directly reflected as light. To Penetrate. At this time, the diffracted light is condensed and diffracted to the focal position f due to the condensing property of the hologram lens array 15. Therefore, when the light is reflected by the reflective layer 18, the light is emitted so as to be condensed at a virtual image focal position f ′, which is a mirror virtual image of the focal position f.
Has a scattered reflection surface, so that scattered reflected light is emitted in the vicinity of the virtual image focus position f 'as a center, and the visual range can be expanded.

FIG. 8 is a graph 32 showing a reflection light amount distribution of a reflection type liquid crystal display device using an existing metal reflection layer, and a graph 33 showing a comparison of the reflection light amount distribution when using the hologram reflection plate of the present invention. It is. As shown in the figure, in the metal reflection layer (graph 32), the intensity of the reflected light in the specular reflection direction is the strongest, and weakens in a normal distribution toward the periphery. On the other hand, in the hologram reflector of the present invention (graph 33), since the viewing area can be controlled by the manufacturing method, the light amount distribution becomes as shown in the drawing, and uniform brightness can be maintained within a predetermined viewing area range. In addition, since the image can be observed at a position deviated from the specular reflection direction, a bright display can be easily viewed without being conscious of the specular reflected light from the light source.

FIG. 9 is an explanatory diagram showing a comparison between the spectral diffraction efficiency of the volume phase reflection hologram (graph 34) and the spectral diffraction efficiency of the volume phase transmission hologram (graph 35).
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 drawing, the diffraction wavelength width of the transmission hologram 35 is clearly wider than that of the reflection hologram 34. 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 with a volume phase reflection hologram, the refractive index modulation degree must be several times that required for 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 hologram employed in the present invention can be recorded by a usual two-beam hologram photographing optical system using a photosensitive material for a volume phase hologram.

As the photosensitive material, gelatin dichromate, a silver salt photosensitive material, a photopolymer and 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.

The photographing and recording of the hologram is performed by a known two-step photographing process. As a laser as a light source, an argon ion laser (wavelength: 514.5 nm) was employed. First,
As a first step, a Fresnel hologram with a diffusion plate (ground glass) as a subject was photographed, and in a second step, a real image of the diffusion plate reproduced from the Fresnel hologram was photographed again as an image type hologram. After hologram shooting in the second step, develop with CWC2 developer, PBQ
2 Bleaching was performed with a bleaching solution, washed with water and dried to obtain a volume phase transmission hologram. 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.

In the above description, a desired mask pattern is arranged in front of the photosensitive material at the time of photographing in the second step, and the mask pattern is step-moved every time the photographing wavelength is changed, and photographing is repeated. 4 is a color hologram reflector. Alternatively, the same effect can be obtained by changing the reference light angle instead of the wavelength.

In the above description, the hologram obtained by photographing the diffusion plate (as a subject) is used. However, when the hologram lens array according to the fifth aspect is used, the refraction lens array is photographed in the same manner as described above. I do. Alternatively, a hologram lens array drawn by an EB drawing device or the like can be used as a master hologram to form a volume phase transmission hologram by a contact copy method or the like.

[0034]

According to the present invention, there is provided a reflection type liquid crystal display device using a hologram as a reflection layer instead of a metal reflection layer, and provides a hologram reflection plate capable of realizing a bright display (particularly, a bright color display). Is done. In the reflection type liquid crystal display device having the metal reflection layer, the background of the liquid crystal display pattern was grayish, whereas according to the reflection type liquid crystal display device using the hologram reflection plate of the present invention, the white or full color background was used. Can be color. Also,
In a conventional display device using a hologram reflector in place of a metal reflection layer, there was a problem that the luminance was low even though the background color could be white or full color. , A bright color display can be realized.

[0035]

[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 a schematic diagram showing an embodiment of a reflection type liquid crystal display device using a hologram reflection plate having a configuration in which volume phase transmission holograms composed of a plurality of types of interference fringes having different spatial frequencies are superimposed.

FIG. 4 is a schematic front view showing an example of a hologram reflector having a configuration in which a plurality of types of holograms having different spatial frequencies are arranged in a specific pattern.

FIG. 5 is a schematic front view showing another example of a hologram reflector having a configuration in which a plurality of types of holograms having different spatial frequencies are arranged in a specific pattern.

FIG. 6 is a schematic diagram showing a reflection type liquid crystal display device using a hologram reflection plate in which a hologram forms a lens array.

FIG. 7 is a schematic view showing another example of a reflection type liquid crystal display device using a hologram reflection plate in which a hologram forms a lens array.

FIG. 8 shows a comparison between a reflection light amount distribution of a reflection type liquid crystal display device using an existing metal reflection layer (graph 32) and a reflection light amount distribution using a hologram reflector of the present invention (graph 33). Graph.

FIG. 9 is an explanatory diagram showing a comparison between the spectral diffraction efficiency of a volume phase reflection hologram (graph 34) and the spectral diffraction efficiency of a volume phase transmission hologram (graph 35).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hologram reflection plate 2 ... Liquid crystal panel 3, 4 ... Polarizing film 5 ... Illumination light 6 ... Volume phase transmission hologram having angle selectivity 7, 9, 17 ... Light incident on hologram 8 ... Metal reflection layer 10 ... Diffraction Light 12, 13, 14… Volume phase transmission holograms with different spatial frequencies 15… Volume phase transmission holograms forming a hologram lens array 16… Liquid crystal panel 18… Reflection layers 19, 20, 21… Liquid crystal pixel cells 22, 23, 24: Volume phase transmission hologram cell with different spatial frequency 25, 26, 27 ... Volume phase transmission hologram cell with different spatial frequency 32 ... Graph showing reflected light amount distribution of liquid crystal display device using metal reflection layer 33 ... Hologram reflection A graph showing the distribution of the amount of reflected light of a liquid crystal display device using a plate 34 ... Spectral diffraction efficiency of volume phase reflection hologram 35 ... Spectral diffraction efficiency of volume phase transmission hologram

Claims (10)

[Claims] 1. A hologram reflector, wherein a reflection layer is arranged on the back of a volume phase transmission hologram having angle selectivity. 2. The hologram reflector according to claim 1, wherein said hologram and said reflection layer are formed in a film-like structure. 3. The hologram reflector according to claim 1, wherein a hologram comprising a plurality of types of interference fringes having different spatial frequencies is multiplex-recorded. 4. The hologram reflection plate according to claim 1, wherein a hologram composed of a plurality of types of interference fringes having different spatial frequencies is superposed. 5. The hologram reflector according to claim 1, wherein holograms composed of a plurality of types of interference fringes having different spatial frequencies are arranged in a specific pattern. 6. The hologram reflector according to claim 5, wherein the hologram has a configuration in which unit holograms having a condensing property for diffracted light are arranged in an array. 7. The hologram reflector according to claim 1, wherein the reflection layer disposed on the back surface of the hologram has a scattering reflection surface. 8. The hologram reflector according to claim 1, wherein a polarizing layer is formed on the surface of the hologram opposite to the reflection layer. 9. A reflection type liquid crystal display device comprising the hologram reflection plate according to claim 1 arranged on a back surface of a liquid crystal panel. 10. The hologram reflector according to claim 6,
A reflection type liquid crystal display device having a configuration in which the focal position of each hologram lens array is located on the back surface of a liquid crystal panel so as to be at the position of the liquid crystal panel.