JP2000089029A - Hologram reflection plate and its production and reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make reflected and diffracted light at a wide wavelength width approximate to white color possible to be generated by specifying the intervals of the wavelengths before and after the diffraction efficiency is halved with respect to the wavelength, at which the diffraction efficiency is maximized, to a specific value or above. SOLUTION: The liquid crystal panel 2 side of the hologram reflection plate 1 is a volume phase reflection type hologram having angle selectivity and emits only a light incident at the same angle as the angle of reference light at the time of hologram photographing as the reflected and diffracted light 4 to the same angle as the angle of the object light at the time of photographing. The incident light which does not match with the angle selectivity of the hologram passes the hologram as it is without receiving the diffraction, is reflected by the reflection layer existing on the rear surface of the halogen, passes the liquid crystal panel again, and arrives as pattern display light at the observer's eyes. The optical characteristics are so set that the central wavelength of the reflected and diffracted light 4 from the hologram exists at a point of 50 nm±30 nm and that the intervals of the wavelengths before and after the diffraction efficiency is halved with respect to the wavelength, at which the diffraction efficiency is maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 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, a hologram reflector suitable therefor, and a method of manufacturing the same. About.

[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.

The reflection plate in the above-mentioned reflection type liquid crystal display device is a reflection plate having a scattering surface 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. Was. 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 surface of the device. 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 chromatic dispersion of the hologram. 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 hologram called a Lippmann hologram, the wavelength width of reflected and diffracted light is narrow and limited (specified color) due to its wavelength selectivity. The effect is realized. 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.

As described above, in the proposals (2), (3) and (4),
Since a volume phase reflection hologram is used, the wavelength width of the reflected and diffracted light is narrow and limited (specified color) due to its wavelength selectivity, and an interesting visual effect with a specific color is realized. It is not visible over a wide range of wavelength components (ie, white) over a range.

In order to view white reflected diffracted light with a volume phase reflection hologram (Lipmann hologram) having wavelength selectivity, a plurality of (for example, three types of red, green, and blue) holograms are superposed, For example, a method of multiplexly capturing and recording a plurality of laser beams (for example, three types of red, green, and blue) on a photosensitive material can be considered.

[0013]

According to the present invention, even a single volume phase reflection type hologram photographed and recorded by a laser beam of one type of wavelength can reflect reflected diffracted light with a wide wavelength width close to white. It is a main object to provide a hologram reflector that can generate the hologram.

[0014]

According to the hologram reflector of the present invention, the center wavelength of the reflected diffracted light is 550 nm ±.
At a position of 30 nm, an interval between wavelengths before and after the diffraction efficiency becomes 1/2 with respect to the wavelength at which the diffraction efficiency becomes the maximum is 100.
It is characterized by being composed of a volume phase reflection hologram having a diffraction characteristic of not less than nm.

According to a second aspect of the present invention, there is provided a method of manufacturing a hologram reflector, wherein a volume phase reflection hologram is photographed and recorded using a laser beam selected from wavelengths of 406 nm, 413 nm and 415 nm, and at least the recorded hologram is recorded. The center wavelength of the diffracted light is lengthened to a range of 550 nm ± 30 nm by performing a process of disturbing and widening the interval between the interference fringes, and before and after the diffraction efficiency becomes 1/2 with respect to the wavelength at which the diffraction efficiency becomes maximum. The method is characterized by including a step of setting a wavelength interval to 100 nm or more.

According to a third aspect of the present invention, there is provided a reflection type liquid crystal display device, wherein the hologram reflection plate according to the first aspect is arranged on a back surface of a liquid crystal panel, and a light reflection layer is arranged on the back surface. .

<Operation> The wavelength interval (hereinafter, referred to as a half-value width) before and after the peak wavelength at which the diffraction efficiency is １ ／ with respect to the wavelength at which the diffraction efficiency is the maximum (hereinafter, referred to as a peak wavelength) is 100 nm. With the above, the reflected diffracted light is not limited to a specific color, but can be made closer to white.

[0018]

FIG. 1 is a schematic view showing a reflection type liquid crystal display device using a hologram reflection plate according to the present invention. The hologram reflector 1 is arranged on the back surface of the liquid crystal panel 2 (on the side opposite to the observer), makes the peripheral illumination light 3 reach the observer 5 as reflected diffracted light 4, and visually displays the image displayed by the liquid crystal panel 2. Let it.

A polarizing film (not shown) is disposed before and after the liquid crystal panel 2, respectively. When the peripheral illumination light 3 enters 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, and is rotated by the liquid crystal panel 2 according to the display pattern. After that, it reaches the second polarizing film.

Light transmitted through the second polarizing film is incident on the hologram reflector 1. A light reflection layer (not shown) is provided on the back surface of the hologram reflection plate 1 (the side opposite to the liquid crystal panel 2).
Are formed. The light reflecting layer may have a mirror surface or a scattering surface, and a material such as resin or metal is appropriately selected.

The liquid crystal panel 2 side of the hologram reflector 1 is
It is a volume phase reflection type hologram having angle selectivity,
Only the light incident at the same (conjugate) angle with the reference light at the time of hologram imaging is emitted as reflected diffracted light 4 at the same angle as the object light at the time of imaging.

Incident light that does not match the angle selectivity and wavelength selectivity of the hologram is transmitted as it is without being diffracted by the hologram. The light transmitted through the hologram is reflected by the reflection layer on the back of the hologram, passes through the hologram, the polarizing film, the liquid crystal panel 2 and the polarizing film again, and reaches the eyes of the observer as pattern display light.

The pattern display light is composed of the diffracted light 4 reflected from the hologram reflector and the light scattered and reflected by the reflection layer.

In photographing the hologram, FIG.
The imaging optical system of the volume phase reflection type hologram (master hologram) shown in FIG.

The object light 31 and the reference light 32 oscillated from the laser light source 30 are made incident from the front and back of the photosensitive material 35 serving as a hologram to make interference with the reference light 32 to record a hologram. In the figure, both the object light 31 and the reference light 32 are parallel light. However, at least one of the object light 31 and the reference light 32 is diffused light or converged light to reflect and diffract light from the hologram reflector (or peripheral light to be reflected and diffracted). ) Can be set to a predetermined value.

As the laser light source 30, 406 nm, 41
One type of laser light selected from wavelengths of 3 nm and 415 nm (existing wavelengths of purple laser) is used.

Since the angle selectivity of the hologram 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. You.

In the present invention, the center wavelength of the diffracted light reflected from the hologram is located at 550 nm ± 30 nm, and the interval between the wavelengths at which the diffraction efficiency becomes 1/2 with respect to the wavelength at which the diffraction efficiency becomes maximum is 100 nm. As described above, it is important to set the optical characteristics of the volume phase reflection hologram.

The above setting is performed as follows. Exposure duplication of master hologram (contact copy)
Although a technique for performing this is well known, a technique for changing the interval of interference fringes of a duplicated hologram and thereby shifting the reproduction wavelength (wavelength of diffracted light) of the hologram is known.

The above method is disclosed in Japanese Patent Application Laid-Open No. 8-297456. The invention according to the above-mentioned publication, the exposure duplicated photopolymerized photopolymer, by heating the film coated with a diffusing agent in close contact, when changing the interval of the interference fringes of the hologram to shift the reproduction wavelength,
Ultraviolet light spread from the inside of the rotating drum to the diffusion film is exposed in a pattern through a mask, and the shift amount of the reproduction wavelength is controlled according to the exposure pattern.

As the photopolymerized photopolymer, JP-A No. 2
Photopolymers described in JP-A-303081 or JP-A-2-3082 are used. As the diffusion film, a film coated with a diffusion agent described in JP-A-3-46687 is used.

The diffusing agent is a substance similar to the monomer used for the photopolymerized photopolymer, and swells the spacing between the interference fringes by heating the photopolymerized photopolymer in which the interference fringes are recorded. The diffusing agent acts so as to cause the reproduction wavelength to shift.

FIG. 3 conceptually shows an apparatus according to Japanese Patent Application Laid-Open No. 8-297456, which involves a shift in the reproduction wavelength of a hologram that has been exposed and copied. In the figure, the photopolymerized photopolymer is represented as HRF, and the diffusion film is represented as CTF.

As the shift amount of the reproduction wavelength is larger, the uniformity of the interval between the interference fringes is lost (that is, the interval between the interference fringes is disturbed), and the wavelength selectivity of the hologram is reduced. Can be reproduced by diffraction.

In order to increase the shift amount of the reproduction wavelength, it is effective that the wavelength of the master hologram recorded first is short (the interval between interference fringes is small). It is preferable to expose and duplicate a master hologram recorded with a laser beam selected from existing 406 nm, 413 nm, and 415 nm violet lasers using a laser in the visible region.

The shift amount of the reproduction wavelength can be increased by increasing the time for heating the diffusion film in close contact with the photopolymerized photopolymer. In the device of FIG.
It is to lengthen the heating time in the oven.

FIG. 4 shows a state in which the diffraction characteristic of the hologram changes due to the shift of the reproduction wavelength. It can be seen that the center wavelength of the reflected and diffracted light of the hologram that has been exposed and duplicated has shifted from around 400 nm to around 550 nm of the master hologram, and the half width has expanded to 100 nm or more.

[0038]

According to the present invention, even a single volume phase reflection hologram photographed and recorded by a laser beam of one kind of wavelength has a half-width of at least 100 nm with respect to the peak wavelength, so that reflected diffracted light can be generated. There is provided a hologram reflector capable of generating reflected diffracted light with a wide wavelength width close to white without being limited to a specific color.

[0039]

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing an imaging optical system of a volume phase reflection hologram (master hologram).

FIG. 3 is an explanatory view schematically showing an apparatus for exposing and duplicating a master hologram accompanied by a reproduction wavelength shift process.

FIG. 4 is an explanatory diagram showing that optical characteristics of a hologram change due to a shift of a reproduction wavelength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Hologram reflector 2 ... Liquid crystal panel 3 ... Peripheral illumination light 4 ... Diffraction reflected light 5 ... Observer 30 ... Laser light source 31 ... Object light 32 ... Reference light 35 ... Photosensitive material

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Claims (3)

[Claims] 1. The center wavelength of reflected diffraction light is 550 nm ± 30.
at a wavelength of 100 nm, and the interval between the wavelengths before and after the diffraction efficiency becomes 1/2 with respect to the wavelength at which the diffraction efficiency becomes maximum is 100 nm.
A hologram reflector comprising a volume phase reflection hologram having the above-mentioned diffraction characteristics. 2. Processing for photographing and recording a volume phase reflection hologram using a laser beam selected from wavelengths of 406 nm, 413 nm, and 415 nm, and then increasing and disturbing at least the interval between interference fringes of the recorded hologram. , The center wavelength of the diffracted light is extended to the range of 550 nm ± 30 nm, and the diffraction efficiency is reduced by 1 / to the wavelength at which the diffraction efficiency is maximized.
2. A method for manufacturing a hologram reflector, comprising the step of setting the interval between wavelengths before and after the step 2 to be 100 nm or more. 3. 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 a light reflection layer is arranged on the back surface.