JP4232918B2 - Diffuse reflection type holographic optical member - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diffuse reflection holographic optical member, and in particular, is a bright diffuse reflection holographic optical member that effectively uses ambient external light and can be used as a diffuse reflection plate for a reflective liquid crystal display device or the like. About things.
[0002]
[Prior art]
The present applicant has proposed a liquid crystal display device using a diffuse reflection hologram in Japanese Patent Application No. 7-312362. The diffuse reflection hologram is a hologram that diffuses and reflects light incident from a specific direction only in a direction defined as an observation area, and is obtained by the one-step photographing method shown in FIG. 5 or the two-step photographing method shown in FIG. Produced.
[0003]
In the one-step imaging method of FIG. 5, a reflection hologram dry plate (Lippmann hologram dry plate) 11 such as a photopolymer is disposed at a position previously determined as a diffuse reflection region with respect to the scattering plate 10 such as ground glass, and the scattering plate. The scattered light 14 illuminated with the coherent light 12 having a predetermined wavelength divided from the same light source from the back surface of the light 10 and emitted from the front surface of the scattering plate 10 is incident on the reflection hologram dry plate 11 as object light, and simultaneously from the same light source. By making another coherent light 13 having a predetermined wavelength divided into two into a reference light, a reference light 13 traveling in a direction opposite to the incident light assumed in the diffuse reflection hologram is made incident from the opposite side to the scattered light 14, thereby reflecting the reflection type. A diffuse reflection hologram is recorded on the hologram dry plate 11.
[0004]
Further, in the two-step imaging method of FIG. 6, as shown in FIG. 6A, a transmissive hologram dry plate 15 is disposed at a position previously determined as a diffuse reflection region with respect to the scattering plate 10 such as ground glass, and scattering is performed. The scattered light 14 illuminated from the back surface of the plate 10 with the coherent light 12 having a predetermined wavelength divided into two from the same light source and emitted from the front surface of the scattering plate 10 is incident on the transmission hologram dry plate 15 as object light, and at the same time The transmission hologram which is the first hologram on the transmission hologram dry plate 15 by making another coherent light 16 having a predetermined wavelength divided by 2 from the same surface side as the scattered light 14 at an arbitrary angle as a reference light Record.
[0005]
Next, the first hologram is set to 17, and as shown in FIG. 6 (b), it is arranged at the position of the original transmission hologram dry plate 15, and this time the reflection type hologram dry plate 20 is placed at the position of the scattering plate 10. The hologram 17 is placed on the opposite side of the reference beam 16 at the time of recording so that the real image of the hologram 17 is formed on the position of the reflection hologram dry plate 20 (the position of the scattering plate 10 in FIG. 1A). The reproduction illumination light 18 having the same wavelength is irradiated so that the diffracted light 19 from the hologram 17 enters the reflection hologram dry plate 20 as object light and proceeds in the opposite direction to the incident light assumed for the diffuse reflection hologram. By making the light 21 enter from the opposite side of the reflection hologram dry plate 20, the diffuse reflection hologram as the second hologram is recorded on the reflection hologram dry plate 20. By this method, a diffuse reflection hologram that limits the observation area to the range of the first hologram 17 can be produced. Further, a hologram that is closely replicated using this hologram as an original plate also becomes a diffuse reflection type hologram in which the diffraction direction (scattering direction) of the original plate is maintained.
[0006]
The diffuse reflection type hologram 31 obtained as described above is incident on the display side of the liquid crystal display element 40 by disposing it on the side opposite to the viewing side of the liquid crystal display element 40 as shown in FIG. A liquid crystal display device capable of diffusing and reflecting illumination light 32 as diffused light 33 only in an angle range θ that matches the observation area of the liquid crystal display device and capable of bright display without using a self-luminous backlight in a bright place. Can be configured. Here, the liquid crystal display element 40 includes, for example, a twisted nematic liquid crystal layer 45 sandwiched between two glass substrates 41 and 42, and a uniform transparent counter electrode is formed on the inner surface of one glass substrate 42. 44, and a transparent display electrode 43 and a black matrix (not shown) are provided on the inner surface of the other glass substrate 41 independently for each pixel. In the case of a color display device, a transparent display electrode 43, a color filter, and a black matrix are provided on the inner surface of the other glass substrate 41 independently for each of the liquid crystal cells R, G, and B. Further, an alignment layer (not shown) is provided on the liquid crystal layer 45 side of the electrodes 43 and 44, and further, a polarizing plate 46 is provided on the outer surface of the observation side glass substrate 41, and the glass substrate 42 on the opposite side to the observation side. Polarizing plates 47 are respectively attached to the outer surfaces, and for example, their transmission axes are arranged so as to be orthogonal to each other. Display is possible by controlling the voltage applied between the transparent display electrodes for each pixel of the liquid crystal display element 40 and changing the transmission state thereof. In the arrangement of FIG. 7, the luminance can be further improved by providing a diffuse reflector or reflector on the back side of the diffuse reflection hologram 31.
[0007]
Further, taking advantage of the characteristic of diffracting only a specific wavelength of the reflection hologram and transmitting light in other wavelength regions, a self-luminous backlight 34 is used on the back side of the diffuse reflection hologram 31 as shown in FIG. Thus, in the dark place, the light is emitted by the light 35 from the self-luminous backlight 34, and in the bright place, the luminance of the self-luminous backlight 31 is reduced or turned off, and the diffuse reflected light 33 of the external light 32 is illuminated. By doing so, the battery drive time of a device using a liquid crystal display device such as a portable computer can be greatly extended.
[0008]
[Problems to be solved by the invention]
As shown in FIG. 3A, the diffuse reflection hologram 31 photographed as described above generally has an external illumination light 32 incident from a predetermined angle range α on one side with respect to the normal n. It has the characteristic of diffracting as scattered light 33 in the front direction. This angle range α is determined by the directions of the reference beams 13 and 21 at the time of shooting, the scattering characteristics of the scattering plate 10, and the like.
[0009]
In any case, the external illumination light 32 can be diffracted when it is incident from one side with respect to the normal line n of the surface of the diffuse reflection hologram 31. As shown in FIG. When the external light illumination light 32 ′ is incident from the opposite side to the normal n of the surface of the reflection hologram 31, the external light illumination light 32 ′ passes through the diffuse reflection hologram 31 as transmitted light 36. Since it does not diffract to the reflection side, it hardly reaches the observer's eyes. This is because the diffuse reflection hologram 31 is called a Lippmann hologram or a volume hologram, and the angle selectivity of the diffracted light is high.
[0010]
Therefore, the conventional diffuse reflection hologram efficiently diffracts and scatters external light incident from a predetermined angle range, but hardly diffracts and scatters external light incident outside the angular range. In a reflection type liquid crystal display device using a type hologram as a diffuse reflection plate, the angle and direction of the display panel must be adjusted in accordance with the direction of available external light. Moreover, the utilization efficiency of ambient external light was not necessarily high.
[0011]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a bright diffuse reflection type holographic optical member that can effectively use illumination light incident from a direction other than a predetermined direction. is there.
[0012]
[Means for Solving the Problems]
The diffuse reflection type holographic optical member of the present invention that achieves the above-mentioned object is integrated with a volume type diffuse reflection hologram that diffusely reflects light incident from a predetermined direction on the front side within a specific angle range on the front side, and integrated on the back side thereof. Or specular reflection mirrors arranged in parallel and spaced apart from each other.
[0013]
In this case, the predetermined direction is a predetermined angle range on one side with respect to the normal line of the diffuse reflection hologram surface, and the center of the specific angle range is the direction of the normal line of the diffuse reflection hologram surface. Can be configured.
[0014]
The diffuse reflection hologram is made of, for example, a photopolymer, and the regular reflection mirror is made of, for example, an aluminum layer.
[0015]
The diffuse reflection type holographic optical member of the present invention is used, for example, as a diffuse reflection plate of a reflective liquid crystal display device.
[0016]
In the present invention, it is composed of a diffuse reflection hologram and a specular reflection mirror disposed on the back side thereof, so that the incident angle range of external light that can be diffusely reflected is doubled and a brighter diffusion than in the case of a diffuse reflection hologram alone. A reflector can be configured. This diffuse reflection type holographic optical member is suitable for a diffuse reflection plate such as a reflection type liquid crystal display device.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the diffuse reflection type holographic optical member of the present invention will be described in detail with reference to the drawings.
The basic configuration of the diffuse reflection type holographic optical member 26 of the present invention is, as shown in a schematic cross-sectional view of FIG. 1, a diffuse reflection type hologram 31 obtained by photographing in the arrangement as shown in FIG. 5 or FIG. Is used. In addition, a metal reflection mirror 25 is arranged behind or in parallel with the metal reflection mirror 25 so as to be substantially parallel to each other. As the metal reflecting mirror 25, for example, a mirror-finished aluminum film or an aluminum vapor-deposited layer that reflects specularly is used.
[0018]
FIG. 2 is a view for explaining the operation of the diffuse reflection type holographic optical member 26 having such a configuration. As described with reference to FIG. 3, the diffuse reflection type hologram 31 itself has a normal line n. On the other hand, external light illumination light 32 (FIG. 3A) incident from a predetermined angle range α on one side (right side in FIG. 2) is diffracted as scattered light substantially in the front direction, but opposite to the normal line n. The external illumination light 32 ′ incident from the side (left side in FIG. 2) hardly diffracts, and has a characteristic of being transmitted through the diffuse reflection hologram 31 as transmitted light 36.
[0019]
In the diffuse reflection type holographic optical member 26 of the present invention, the metal reflection mirror 25 is disposed behind or in the space of the diffuse reflection type hologram 31, so that the transmitted light 36 is reflected by the metal reflection mirror 25. The light 37 is regularly reflected, and the reflected light 37 enters from the back of the diffuse reflection hologram 31 at the same angle as the incident angle of the external illumination light 32 ′ to the diffuse reflection hologram 31. When the reflected light 37 travels in the opposite direction to the external light illumination light 32 (FIG. 3A) incident within the predetermined angle range α, that is, the external light illumination light 32 ′ has an angle range −α opposite to the angle range α. When incident, the reflected light 37 is diffracted as scattered light in the back surface direction by the diffuse reflection hologram 31, and the scattered light is reflected in the front direction by the metal reflection mirror 25 to become scattered light 38. This scattered light 38 is then incident substantially perpendicularly from behind the diffuse reflection hologram 31. A part of the scattered light 38 is diffracted by the diffuse reflection hologram 31 in the transmission direction of the external light illumination light 32 (FIG. 3A), but the rest is transmitted through the diffuse reflection hologram 31 and is the same as the scattered light 33. For example, it can be used for display when used as a diffuse reflection plate of a reflective liquid crystal display device.
[0020]
Here, when the diffraction efficiency of the diffuse reflection hologram 31 of the external illumination light 32 incident from the predetermined angle range α is, for example, 50%, the scattered light 38 has substantially half the intensity of the external illumination light 32 ′ and is diffusely reflected. Although the light 39 has an intensity of about one quarter, the ambient light 32 ′ within the angle range −α that originally did not contribute to the display can be contributed to the display. In combination with 32, brighter display becomes possible. Moreover, even when the external light is only within the angle range α or −α, it is not necessary to adjust the angle and direction so that the direction of the display panel matches the direction of the external light.
[0021]
FIG. 4 is a cross-sectional view of a configuration in which the diffuse reflection holographic optical member 26 according to the present invention is disposed on the backlight side of the liquid crystal display element 40 as shown in FIG. 7 as an example. As described above, the external illumination light 32 incident within the angle range α from the display side of the liquid crystal display element 40 is only within the predetermined front angle range θ (FIG. 7) that matches the observation area of the liquid crystal display device. Diffused light 33 is diffusely reflected. On the other hand, the external light illumination light 32 ′ incident within the angle range −α from the display side of the liquid crystal display element 40 also diffuses only within a predetermined front angle range θ (FIG. 7) that matches the observation area of the liquid crystal display device. The light 39 is diffusely reflected. Therefore, a liquid crystal display device capable of bright display without using a self-luminous backlight in a bright place is configured. Here, when the external light exists in the angle ranges α and −α, that is, on both sides with respect to the normal line n, the conventional example of FIG. Since there is also diffused light 39 in addition to 33, a brighter display is possible. In the conventional example, when the external light exists only within the angle range −α, the display cannot be seen, and the angle and direction are adjusted such that the display panel is rotated by 180 ° around the normal line n. Although necessary, in the present invention, since the diffused light 39 is obtained, it is not necessary to make such adjustment.
[0022]
The diffuse reflection type holographic optical member of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made.
[0023]
【The invention's effect】
As is clear from the above description, according to the diffuse reflection type holographic optical member of the present invention, the diffuse reflection type hologram and the specular reflection mirror disposed on the back side thereof are included, so that the diffusion reflection type hologram alone is more diffused. The incident angle range of external light that can be reflected is doubled, and a brighter diffuse reflector can be configured. This diffuse reflection type holographic optical member is suitable for a diffuse reflection plate such as a reflection type liquid crystal display device.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining a basic configuration of a diffuse reflection type holographic optical member of the present invention.
FIG. 2 is a diagram for explaining the operation of the diffuse reflection type holographic optical member of the present invention.
FIG. 3 is a schematic cross-sectional view for explaining the characteristics of a diffuse reflection hologram.
FIG. 4 is a cross-sectional view of a configuration example in which a diffuse reflection type holographic optical member according to the present invention is disposed on the backlight side of a liquid crystal display element.
FIG. 5 is a diagram for explaining a method of producing a diffuse reflection hologram by a one-step imaging method.
FIG. 6 is a diagram for explaining a method of producing a diffuse reflection hologram by a two-step imaging method.
FIG. 7 is a cross-sectional view of a liquid crystal display device provided with a conventional diffuse reflection hologram.
FIG. 8 is a cross-sectional view of another liquid crystal display device having a conventional diffuse reflection hologram.
[Explanation of symbols]
n ... Normal 26 ... Diffuse reflection type holographic optical member 31 ... Diffuse reflection type hologram 25 ... Metal reflection mirrors 32, 32 '... External light illumination light 33 ... Diffuse light 36 ... Transmitted light 37 ... Reflected light 38 ... Scattered light 39 ... Diffuse reflected light 40 ... Liquid crystal display elements 41, 42 ... Glass substrate 43 ... Transparent display electrode 44 ... Transparent counter electrode 45 ... Liquid crystal layers 46, 47 ... Polarizing plate

Claims (3)

A volume type diffuse reflection hologram that diffuses and reflects light incident from a predetermined direction on the front side within a specific angle range on the front side and transmits light incident from a direction other than the predetermined direction, and is integrated or separated on the back side And the predetermined direction is a predetermined angle range on one side with respect to the normal line of the diffuse reflection type hologram surface, and the center of the specific angle range. there up direction der normal of the diffusion reflection hologram surface, center the light incident from a predetermined direction of the front side of the said diffuse reflection hologram of the in the direction of the normal of the diffusion reflection hologram surface Light diffusely reflected within a specific angle range and incident from the side opposite to the predetermined direction on the front side with respect to the normal line of the diffuse reflection hologram surface is transmitted through the diffuse reflection hologram and reflected regularly. And the reflected light is incident on the diffuse reflection hologram from the back surface side and the center is in the direction of the normal line of the diffuse reflection hologram surface. The diffuse reflection type hologram is characterized in that the diffuse reflection light is incident on the specular reflection mirror and specularly reflected, and the reflected light is incident on and transmitted through the diffuse reflection hologram from the back side. Graphic optical member.   The diffuse reflection type holographic optical member according to claim 1, wherein the diffuse reflection type hologram is made of a photopolymer, and the specular reflection mirror is made of an aluminum layer.   3. The diffuse reflection type holographic optical member according to claim 1, wherein the diffuse reflection type holographic optical member is used as a diffuse reflection plate of a reflection type liquid crystal display device.

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