JP2000066026A - Holographic diffusing sheet and reflection type liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably arrange a holographic diffusing sheet on the front surface of the liquid crystal panel of a display device which does not require a special light source by forming an angle at which the optical axes of object light and reference light are nearly aligned and performing photographing-recording with the object light being diffused light. SOLUTION: A laser beam emitted from one laser beam source is divided into two by a beam splitter, and either laser beam is made the object light being the diffused light illuminating a diffusing plate consisting of ground glass and the other is made the reference light being spherical wave or plane wave, and master hologram is formed by recording the interference fringe of two light waves on photosensitive material for hologram first and performing developing bleaching processing thereto. Next, the master hologram 22 is reproduced and the image of the diffusing plate is formed on the photosensitive material for hologram 25. Then, the photosensitive material 25 is irradiated with the reference light 24 transmitted through the master hologram 22 so that the optical axis of the reproducing light 23 may be aligned with that of the reference light 24, and holographic photographing-recording is performed again. The on-line holographic diffusing sheet formed by performing developing bleaching processing is arranged on the front surface of the liquid crystal display panel and is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be used for an image display device using a reflection type liquid crystal panel, such as a reflection type liquid crystal television, a reflection type liquid crystal monitor, etc., without increasing the power consumption of the main body of the device. The present invention relates to a diffusion sheet suitable for realizing a stable image display and a reflective liquid crystal display device using the same.

[0002]

2. Description of the Related Art In a reflection type liquid crystal display device, a reflector such as a reflection plate or a reflection film having a light diffusing property is arranged on the back side of a liquid crystal panel (the side opposite to an observer) to diffuse ambient light entering the device. The light is reflected so that a display image formed on the liquid crystal panel is visually recognized by an observer. The device comprises:
Since the display light does not require a special light source such as a backlight or an edge light and uses ambient light (sunlight or illumination light), it is effective in terms of power consumption.

In order to display a bright and high-contrast image, it is preferable that the reflector has a high reflectance and a certain degree of directivity. Therefore, the conventional reflector has been formed from a material having a metal surface processed into a mat shape.

In a conventional reflector having a metal surface processed into a mat shape, a mat surface is formed by sandblasting the metal surface or dissolving using a solution (acidic or alkaline). Therefore, it is difficult to control the light diffusivity (the state of the rough surface), and when used in a reflective liquid crystal display device, unnecessary diffused light that does not contribute to observation is generated, resulting in a decrease in brightness and contrast. is there.

In recent years, a reflection type liquid crystal display device in which an electrode for driving a liquid crystal also serves as a reflector has been developed. In order to provide display light with diffusivity, a liquid crystal panel is provided on the front side (viewer side) of the liquid crystal panel. A method of arranging a light diffusion film is also employed.

When a normal light diffusing film is used, light is diffused both at the time of light incidence and at the time of light reflection, so that a double image is generated due to a pixel shift, and a high-definition display cannot be sufficiently performed. is there. In addition, a method of processing an electrode (reflector) into a mat shape is also adopted, but there is a problem that unnecessary diffused light is generated as in the above-described conventional metal reflector.

[0007] As an alternative to the above diffusion film,
The use of a hologram (referred to as a holographic diffusion sheet or a hologram scattering plate) that diffracts diffused light is being studied, and the off-axis (Off-ax) is used as the hologram.
is) The use of holograms has been proposed, but the diffracted light of holograms recorded off-axis undergoes chromatic dispersion, so that the diffused light changes to a rainbow color depending on the position where the display screen is viewed, and the observer sees the displayed image. There is a problem that hinders visual recognition.

The off-axis hologram is a hologram in which the optical axes of the object light and the reference light are recorded at an angle in a two-beam optical system for photographing and recording a hologram.

Japanese Patent Application Laid-Open No. 9-152602 is known as a proposal for controlling the viewing area (widening) by disposing a hologram scattering plate on the front surface of a liquid crystal panel. It controls the emission range of the display light due to the above, and does not provide the display light in the reflection type liquid crystal display device with diffusivity.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a holographic diffusion sheet suitable for being arranged on the front surface of a liquid crystal panel of a reflection type liquid crystal display device which does not require a special light source, and a reflection type liquid crystal display device using the same. The purpose is to provide.

That is, by making the diffusion sheet have a function (light diffusion having anisotropy) in which light is diffused when light is incident on the device and is not reflected when reflected, it is directly transmitted. In this case, a double image due to pixel shift is prevented. It is another object of the present invention to provide a reflection type liquid crystal display device which realizes bright, high-contrast, high-definition display by realizing white diffracted light without color change of display light depending on an observation position.

[0012]

According to the present invention, a diffusion sheet made of an online hologram is employed as a holographic diffusion sheet. The online hologram is for an off-axis hologram, and is a hologram photographed and recorded at an angle at which the optical axes of the object light and the reference light substantially coincide with each other.

The holographic diffusion sheet according to claim 1 forms an angle at which the optical axes of the object light and the reference light substantially coincide with each other,
It is characterized by being photographed and recorded by object light that is diffused light.

A holographic diffusion sheet according to a second aspect is a volume phase transmission hologram.

[0015] The holographic diffusion sheet according to claim 3 is a surface relief hologram having angle selectivity.

In the reflection type liquid crystal display device of the present invention, a reflector is disposed on the back surface of the liquid crystal panel, and ambient light incident from the front surface of the liquid crystal panel is reflected by the reflector toward the liquid crystal panel side, and modulated by the liquid crystal panel. 2. A reflection type liquid crystal display device which allows an observer to view the displayed light, wherein a front surface of the liquid crystal panel is provided.
3. The holographic diffusion sheet according to any one of 1 to 3, wherein the holographic diffusion sheet is arranged.

[0017] The reflector may be a specular reflector that specularly reflects incident light.

The reflector may be a diffusive reflector for diffusing and reflecting incident light.

[0019] The reflector may also serve as an electrode for driving the liquid crystal.

<Operation> The online holographic diffusion sheet can be provided with a light diffusion function having anisotropy according to the photographing conditions. It is also possible to arbitrarily control each of the horizontal directions. (Claim 1)

When the online holographic diffusion sheet is a volume phase transmission type hologram, the incident light to the reflection type liquid crystal display device is diffracted and diffused by the hologram and the emitted display light is transmitted directly. In addition to providing anisotropy, it is also possible to diffract only incident light at a specific incident angle due to the angle selectivity of the hologram. (Claim 2)

When the online holographic diffusion sheet is a surface relief hologram having an angle selectivity, the diffusion sheet can be mass-produced at low cost by emboss duplication to a thermoplastic resin by a stamper generated from a master hologram. . (Claim 3)

In the reflection type liquid crystal display device according to the present invention, by arranging the above-described online holographic diffusion sheet on the front surface of the liquid crystal panel, the light transmitted through the online hologram from the front surface of the liquid crystal panel is incident on the liquid crystal panel. The light diffuses as if it were transmitted through a diffuser sheet, reaches the reflector as diffused light, and the diffused light reflected by the reflector passes through the online hologram and is emitted from the front of the liquid crystal panel. The light is emitted without being diffused as when transmitted through a transparent sheet. Therefore, the display becomes bright because there is no unnecessary display light diffusion, and light diffusion occurs only at the time of light incidence. High-definition display can be performed without a phenomenon such as pixel bleeding. (Claim 4)

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the reflection type liquid crystal display device according to the present invention will be described in detail with reference to the drawings. FIG.
As shown in FIG. 1, a reflective liquid crystal display device 1 according to the present invention comprises a liquid crystal panel 2, a specular or diffusive reflector 3 disposed on the back surface thereof, and an online holographic device disposed on the front surface of the liquid crystal panel 2. And a diffusion sheet 4.

In the figure, the optical characteristics (optical paths of incoming and outgoing light) are shown.
Is schematically shown as being spaced apart from the online holographic diffusion sheet 4, the liquid crystal panel 2, and the reflector 3, but they are actually adhered and laminated by an adhesive layer (not shown). ing. In addition, incident light, reflected light, display light, and the like are all shown as light rays so that all claims can be conceptually described.

In the reflection type liquid crystal display device 1, the reflector 3 may not be separate from the liquid crystal panel 2, but may be provided inside the liquid crystal panel 2 as an electrode for driving liquid crystal.

The liquid crystal panel 2 has a general structure, and modulates incident light in accordance with the presence or absence of an applied voltage, and switches between white and black.

As shown, when the incident light 5 enters the online holographic diffusion sheet 4 from the front side of the liquid crystal panel 2, light diffusion occurs, and the diffused light is
The light is reflected by the reflector 3 on the back side, passes through the online holographic diffusion sheet 4 and exits to the front, and the display light reaches the observer 7. At this time, the online holographic diffusion sheet 4 transmits the emitted diffused light 6 as it is without secondary light diffusion.

FIGS. 2 and 3 are structural views showing an example of an optical system for producing the online holographic diffusion sheet 4 shown in FIG.

As shown in FIG. 2, one laser light source 10
The laser beam emitted from the beam splitter 11
And one of them is a diffusion plate 12 made of ground glass or the like.
Is used as object light which is the diffused light 13 illuminated, and the other is used as the reference light 14 which is a spherical wave or a plane wave, and interference fringes of the two light waves are first recorded on the hologram photosensitive material 15, subjected to development bleaching processing, and subjected to master bleaching. Create a hologram.

Next, as shown in FIG. 3, the master hologram 22 is reproduced and the image of the diffusion plate is converted to the hologram photosensitive material 2.
5, the hologram photosensitive material 25 is illuminated with the reference light 23 transmitted through the master hologram 22 so that the optical axis of the reproduction light 23 and the optical axis of the reference light 23 coincide with each other.
Perform holographic shooting and recording again.

According to the above-described two-step hologram recording method using the optical system shown in FIGS. 2 and 3, the diffused light from the diffusion plate 12 is first recorded on the hologram photosensitive material 15 as a hologram to produce a master hologram. Then, the reproduction light 23 from the master hologram 22 is irradiated and recorded on the hologram photosensitive material 25 as object light and light having the same optical axis as the object light is used as reference light 24, which is developed and bleached. Thus, the online holographic diffusion sheet 4 can be prepared, and is used by being arranged on the front surface of the liquid crystal display panel 2.

When the online holographic diffusion sheet 4 in FIG. 2 is manufactured, the distance between the diffusion plate 12 and the hologram photosensitive material 15 and the size of the diffusion plate 12 depend on the light diffusion of the online holographic diffusion sheet 4. Reflection type liquid crystal display device 1 of the present invention
Is appropriately selected in the range of about 0 to 1 m in consideration of the visual field which can be observed best. Further, in FIG. 3, the exposure light is obliquely incident on the photosensitive material. However, since this incident angle affects the selectivity of the angle which causes the function of light diffusion / direct transmission, it is 0 to 80 degrees. The degree is appropriately selected depending on the use of the reflective liquid crystal display device 1 of the present invention.

Since the size and diffusivity of the diffusion plate 21 affect the light diffusivity of the online holographic diffusion sheet 4, the size is in the range of 1 to 500 mm on one side and the diffusivity is the same as that of ground glass. Number 10 to 1000 in number
An appropriate number between 0 is appropriately selected.

As the liquid crystal display panel 2 of the reflection type liquid crystal display device of the present invention, either a color display panel equipped with color filters corresponding to R, G, B pixels or a monochrome display panel is used. Is also good. In addition, TN method, ST
It is not particularly limited to a liquid crystal driving method such as an N method, a guest host method, and a polymer dispersion type.

As the reflector 3 disposed on the back of the liquid crystal display panel 2, either a regular reflection reflector or a light diffusion reflector may be used. Or liquid crystal panel 2
The electrode for driving the liquid crystal contained therein may function as a reflector as it is.

The argon ion laser used for manufacturing the light diffusing sheet 4 is a laser beam having a wavelength of 514.5 nm (green), a laser beam of 488 nm (blue-green) or a laser beam having a wavelength of 457.9 nm (blue). ) Can be used. In addition, other than an argon ion laser, a laser light source having good coherence can be produced. For example, a helium neon laser or a krypton ion laser can be used.

As the diffusion plate 12 of the subject, for example, frosted glass is used, and the hologram photosensitive materials 15 and 2 are used.
For example, silver halide photosensitive materials for holograms for green and blue manufactured by Agfagewald can be used as 5.

In one embodiment of the present invention, No. 1000 ground glass was recorded on a silver halide photosensitive material for an 8E56 hologram manufactured by Agfagewald using an argon laser of 514.5 nm by a two-step hologram recording method. Later, CWC2 developer is used for development, and PWC is used for bleaching.
Developing, bleaching, washing with water and drying using the BQ2 bleaching solution were performed on a reflection type liquid crystal display device using TN type liquid crystal with the configuration as shown in FIG.

In the optical system shown in FIG. 3, even if hologram recording is performed with the angle between the object beam and the reference beam off-axis within the range of 0 to 5 degrees, the chromatic dispersion of the diffracted beam from the holographic diffusion sheet is small. The holographic diffusion sheet was mounted on a reflection type liquid crystal display device using a TN type liquid crystal in the configuration as shown in FIG. 1, and the display image was observed. It was confirmed that an off-axis in the range of 0 to 5 degrees could be regarded as an online hologram if it hindered the visual recognition of the image.

Further, in the case of the volume phase type hologram according to the second aspect, it is produced by using the above-mentioned silver salt photosensitive material, gelatin dichromate, photopolymer and the like. Claim 3
In the case of the surface relief hologram described in (1), an embossed hologram produced by using a photoresist as the hologram photosensitive material 25 in FIG. 3 or copied as an original plate (stamper) by a method such as embossing on a thermoplastic resin sheet is used. Can be used.

[0042]

As described above, by arranging an online holographic diffusion sheet having anisotropic light diffusing property as a light diffusing plate of a reflection type liquid crystal display device on the front surface of a liquid crystal display panel, illumination can be achieved. It is possible to have anisotropy that diffuses light only when ambient light, which is light, enters the liquid crystal display device, and transmits light without being diffused when it is emitted from the liquid crystal display device. There is no unnecessary diffusion of display light, and the display becomes bright, and a high-definition display can be performed without generating a double image due to pixel shift. In particular, in the diffusion sheet according to the present invention, the color of display light that is visually recognized does not change according to the observation position.

[Brief description of the drawings]

FIG. 1 is an explanatory view conceptually showing a reflection type liquid crystal display device of the present invention.

FIG. 2 is an explanatory view showing an example of an optical system (first step) for producing an online holographic diffusion sheet.

FIG. 3 is an explanatory view showing an example of an optical system (second step) for producing an online holographic diffusion sheet.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reflection type liquid crystal display device 2 ... Liquid crystal display panel 3 ... Reflector 4 ... Online holographic diffusion sheet 5 ... Incident light 6 ... Outgoing light 7 ... Observer 10 ... Laser light source 11 ... Beam splitter 12 ... Diffusion plate 13 ... Diffusion Light 14 Reference light 15 Holographic photosensitive material 16a, 16b, 16c, 26a, 26b, 26c Reflector 17a, 17b, 27a, 27b Spatial filter 18a, 18b, 28a, 28b Lens 20 Laser light source 21 Beam splitter 22 Master hologram 23 Diffracted light 24 Reference light 25 Photosensitive material for hologram

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 CA01 CA05 CA16 CA22 CA28 2H091 FA14Y FA14Z FA19X FA31X FA31Y FA31Z FB02 FB06 GA02 LA16 LA17 2K008 AA10 BB04 DD13 DD15 DD22 EE01 FF11 FF17 HH01 HH19 HH23

Claims (7)

[Claims] 1. A holographic diffusion sheet characterized in that the optical axis of the object light and the reference light form an angle that substantially coincides with each other, and the holographic diffusion sheet is photographed and recorded by the object light that is the diffused light. 2. The holographic diffusion sheet according to claim 1, wherein the holographic diffusion sheet is a volume phase transmission hologram. 3. The holographic diffusion sheet according to claim 1, wherein the holographic diffusion sheet is a surface relief hologram having an angle selectivity. 4. A reflector is disposed on the rear surface of the liquid crystal panel, and ambient light incident from the front surface of the liquid crystal panel is reflected by the reflector toward the liquid crystal panel, and display light modulated by the liquid crystal panel is visually recognized by an observer. A reflective liquid crystal display device, comprising: a holographic diffusion sheet according to claim 1 disposed in front of a liquid crystal panel. 5. The reflection type liquid crystal display device according to claim 4, wherein said reflector is a regular reflection reflector for regularly reflecting incident light. 6. The reflection type liquid crystal display device according to claim 4, wherein said reflector is a diffusive reflector for diffusing and reflecting incident light. 7. The reflection type liquid crystal display device according to claim 4, wherein said reflector also serves as an electrode for driving liquid crystal.