JP2000298205A - Optical diffusing plate and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain satisfactory light-diffusing performance and a good contrast ratio by forming a passing region, where incident collimated light mainly passes and a non-passing region having relatively low light-transmission property and applying the both materials for these regions at a time. SOLUTION: An optical diffusion plate 16a is produced by fixing light- transmitting spheres (beads) 20, which constitute a diffusing layer with a light- absorbing binder 22 to a light-transmission supporting sheet 18. The collimated light emitted from a backlight part and passing a liquid crystal panel 12 to carry an image is refracted (diffused) by the spheric beads 20, passes through the contact area between the beads 20 and the supporting sheet 18 and near this area (contact part) which is the passing region for light, and is diffused sufficiently. Since a binder 22 has light-absorbing property, the non-passing region except for the contact part of the beads 20 and the supporting sheet 18 acts as a black mask. Thus, the external light from the observer's side is not reflected or diffused by the optical diffusion plate 16, and there is no decrease in contrast.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of light diffusing plates and display devices, and more particularly, has a wide viewing angle,
Also, the present invention relates to a light diffusion plate capable of realizing a liquid crystal display for displaying a high-contrast image, a liquid crystal display device using the light diffusion plate, and an image display device having a matrix structure.

[0002]

2. Description of the Related Art In recent years, with the spread of word processors and personal computers, various image display devices have been developed and used for displaying images. An image display device generally includes a display device that converts an image information electric signal into image light and displays the image light on a display screen, a drive circuit that drives the display device, and a power supply that supplies power to the drive circuit. You. There are various image display devices depending on the optical system of display and the drive system of the display device, but the CRT (Cathode Rad) has been most widely used in the past.
y Tube) Display. For example, ultrasound diagnosis, C
In medical fields such as T diagnosis and MRI diagnosis, black and white CR
Although a T display is used, this monochrome CRT display can obtain a smooth and natural image because there is no digital matrix structure.

On the other hand, recently, miniaturization is easy,
Liquid crystal displays (Liqu
id Crystal Display (LCD) has been used in various fields. In particular, as a display of a word processor or a computer, L
The frequency of using CDs has increased significantly. Also, LCD
The use of is also being considered as a monitor of a medical diagnostic apparatus, such as an ultrasonic diagnostic apparatus, a CT diagnostic apparatus, and an MRI diagnostic apparatus, in which a CRT has conventionally been the mainstream.

[0004]

As described above, the LCD has many advantages such as easy miniaturization, thinness and light weight, but has poor viewing angle characteristics (narrow viewing angle). ), That is, the contrast ratio of the image sharply decreases depending on the viewing direction and the angle, and the inversion of the gradation occurs, so that the appearance of the image differs. Therefore, there is a problem that the image cannot be properly observed depending on the position of the observer or the like. In particular, in medical applications such as those mentioned above, diagnosis is performed based on the density of the image, so an image with a high contrast ratio is required.In addition, improper recognition of the image is a cause of misdiagnosis and discrepancies in the diagnosis results. Become. Therefore, in particular,
An image with a high contrast ratio is required over a wide viewing angle. Further, in a medical monitor, a display image is usually a monochrome image, and thus the image contrast greatly depends on the viewing angle, which is more problematic.

[0005] In addition, as a wide viewing angle LCD, IPS (I
n-Plane Swiching) mode, MVA (Multi-domain Vert
Although LCDs of the Alignment mode are known, they have not been able to secure a sufficiently wide viewing angle for monochrome images, particularly for medical applications.
On the other hand, as an LCD capable of obtaining an image with a good contrast ratio over a wide viewing angle, collimated light (straight light) is used as a backlight (collimated backlight), and light transmitted through a liquid crystal panel is diffused. A method of diffusing with a plate is known. However, an LCD that uses a diffuser plate to achieve a sufficient viewing angle even in medical applications
Has not yet been realized. In addition, in the method using a diffusion plate, external light incident on the diffusion plate is also reflected and scattered, thereby reducing the contrast of an observed image,
After all, it is often impossible to observe a suitable image.

On the other hand, a high-definition display, such as an LCD, which has a clear digital pixel matrix structure, high sharpness, and is suitable for displaying an artificial image such as CG (Computer Graphics). However, LCD
Has a matrix structure of digital pixels. For example, for a still image having a natural smoothness such as an X-ray image, the clarity of the matrix structure gives a mosaic effect. However, there is a problem that an undesired state called so-called pixelization (or jaggy) in which the image is jagged occurs. This is the case when the pixel size is large (for example, 15 "XGA (Extended Gra
In a phics array, the pixel size is about 300 μm), and the vertical streaks of the matrix structure of the color filter are clearly visible, and are particularly conspicuous. Not only LCDs but also color C
RT and PDP (Plasma Display Panel) which have a matrix structure also have a problem that the above-mentioned pixelization occurs.

A first object of the present invention is to solve the above-mentioned problems of the prior art, to have excellent light diffusion performance, and to suitably reduce a decrease in contrast due to surface reflection, and use the liquid crystal display. Accordingly, it is possible to provide a light diffusing plate having a good contrast ratio over a wide viewing angle and realizing a liquid crystal display suitable for medical use, and a liquid crystal display device using the light diffusing plate. It is in. A second object of the present invention is to solve the above-mentioned problems of the prior art, to eliminate pixelization (jaggies) (that is, to perform pixelization), and to obtain an image display capable of obtaining a smooth and natural display image. It is to provide a device.

[0008]

In order to achieve the first object, a light diffusing plate according to a first aspect of the present invention comprises an invisible structure having an optical refracting power and an invisible structure. A passing area through which parallel light mainly entering from a possible structure side passes, and a non-passing area other than the passing area having a relatively low light transmittance as compared with this passing area; The material of the region and the material of the non-passage region are applied simultaneously. Here, a light-transmissive support,
It is preferable that a light-transmitting sphere constituting the passing area is fixed to a light-absorbing binder constituting the non-passing area, and a diffusion layer formed on the support. Further, it is preferable that the reflectivity to external light be 10% or less due to the function of the non-passing region.

Further, the light diffusion plate of the present invention comprises a light-transmitting support, a diffusion layer having a light-transmitting sphere, and a photosensitive heat developing material layer formed between the support and the diffusion layer. When,
Having a photosensitive heat developing material layer, the exposed portion is made of a non-colored photosensitive heat developing material, and heat-colors the photosensitive heat developing material after substantially parallel light is incident from the diffusion layer side. Is characterized by the following. Further, the light diffusion plate of the present invention has a light-transmitting support, a diffusion layer having a light-transmitting sphere, and a thermal ablation layer formed between the support and the diffusion layer, The thermal ablation layer
It is made of a light-absorbing thermal ablation material, and is obtained by removing the thermal ablation material in a region irradiated with light by entering substantially parallel light from the side of the diffusion layer with heat energy by light. .

Further, the light diffusion plate of the present invention has a light-transmitting support and a diffusion layer composed of a light-transmitting sphere, and the material in contact with the sphere is made of a photosensitive material whose exposed portion is non-colored. The photosensitive material is colored by heating and developing after substantially parallel light is incident from the side of the diffusion layer. Further, the light diffusion plate of the present invention has a light-transmitting support and a diffusion layer made of a light-transmitting sphere, and the material in contact with the sphere includes a light-absorbing material,
A light-exposed portion is provided with a non-colored photosensitive material between the material in contact with the sphere and the support, and after the substantially parallel light is incident from the diffusion layer side, the photosensitive material is colored by heat development. It is characterized by the following.

In each of the light diffusing plates, it is preferable that the diffusion layer is formed by forming a layer of a material that comes into contact with the sphere first, and then embedding the sphere. It is preferable that a surface of the support opposite to the diffusion layer is subjected to a light non-reflection treatment.

A display device according to a second aspect of the present invention comprises:
A liquid crystal display panel, a backlight unit for inputting parallel light to the liquid crystal display panel, and the light diffusion plates disposed on the opposite side of the liquid crystal display panel from the backlight unit. I do.
Here, it is preferable to further provide an external light scattering prevention sheet on the light diffusion plate.

In order to solve the above-mentioned second problem, an image display device according to a third aspect of the present invention provides a visual display device having an optical refractive power on an observation side of a display screen of an image display device having a matrix structure. A light diffusion plate having an impossible structure is provided. Further, it is preferable that the light diffusing plate has a light transmissive support and a diffusion layer formed by fixing a light transmissive sphere to a binder. Further, it is preferable that an external light scattering prevention sheet is further provided on the light diffusion plate provided on the observation side of the display screen.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A light diffusing plate and a display device according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 conceptually shows an embodiment of a display device according to the second embodiment of the present invention, which utilizes the light diffusion plate according to the first embodiment of the present invention. A display device 10 shown in FIG. 1 is a so-called liquid crystal display (hereinafter, referred to as an LCD) that uses a liquid crystal panel 12 as an image display means. The liquid crystal panel 12 and collimated light (straight light) ) And the liquid crystal panel 1
The light diffusion plate 16 according to the first aspect of the present invention, which diffuses the light carrying the image passing through the light diffusion plate 2. In addition, a driver (not shown) for driving the liquid crystal panel 12 is connected to the liquid crystal panel 12, and various members of a known LCD are arranged in the display device 10 as necessary. Display device 1 of the present invention utilizing light diffusion plate 16 of the first embodiment of the present invention
A value of 0 can realize a high contrast ratio over a wide viewing angle, so that it can be suitably used for a monitor or the like of a medical diagnostic apparatus.

The liquid crystal panel 12 used in the display device 10 of the present invention is not particularly limited, and liquid crystal is filled between transparent supports arranged with a predetermined gap, and a transparent electrode is provided. Any known liquid crystal panel used for various LCDs, in which an analysis plate is disposed on one surface of the sheet-like liquid crystal sandwiching support and a polarizing plate is disposed on the other surface, can be used. Accordingly, the liquid crystal panel 12 used in the display device 10 of the present invention
May be color or monochrome, and the operation mode is TN (Twisted Nematic) mode, STN (Super Twisted
sted Nematic) mode, ECB (Electrically Controll)
ed Birefringence) mode, IPS (In Plane Switchi)
ng) mode, MVA (Multidomain Vertical Alignment)
All modes of operation, such as modes, are available. Among them, a TN mode liquid crystal panel is particularly preferable. Although the liquid crystal display of the TN mode has a low viewing angle characteristic, the configuration of the liquid crystal panel itself is simpler than that of the wide viewing angle mode such as the IPS mode and the MVA mode. Therefore, the use efficiency of the backlight at the time of high resolution is high, and high-definition image display can be easily performed. Further, the switching element and the matrix are not particularly limited.

As the backlight unit 14, various light source devices can all be used as long as they can emit collimated light of a light quantity sufficient for image observation. As an example, one using a louver that passes only part of the scattered light, one that uses a lens to collimate the light emitted from a point light source like an overhead projector, and one that uses a microlens effect to reduce the scattered light A device that produces parallel light having directivity is preferably exemplified.

The light diffusing plate 16 of the present invention has an optical refractive power (optical power) and has a fine spherical shape or the like that cannot be visually recognized by an observer of the display device 10. And, compared to a region through which parallel light incident from the structure side mainly passes (passing region), the other region (non-passing region) has a relatively low light transmittance, Preferably, the non-passing area has a light absorbing property (a black mask). Here, it is necessary that the material of the passage area and the material of the non-passage area are applied simultaneously. Further, due to the effect of the non-passing region, it is preferable that the reflectance with respect to external light be 10% or less.

FIG. 2A is a schematic cross-sectional schematic view of one embodiment of the light diffusing plate according to the first aspect of the present invention. The light diffusing plate 16a shown in the figure is one of the embodiments of the light diffusing plate 16 of the present invention, and the light transmissive support sheet 18 is provided with a light transmissive sphere (hereinafter, referred to as a diffusing layer). (Beads) 20
Is fixed by a binder 22 having a light absorbing property. The beads 20 are partially in contact with the support sheet 18.

Therefore, as shown by a dashed line in FIG. 2A, the collimated light carrying the image, which is emitted from the backlight unit 14 and passes through the liquid crystal panel 12, is refracted (diffused) by the spherical beads 20. Then, the light passes through a contact portion between the beads 20 and the support sheet 18 which is a light passage area and the vicinity thereof (hereinafter, simply referred to as a contact portion), and is sufficiently diffused. Moreover, since the binder 22 has a light absorbing property, a non-passing area other than a contact portion between the beads 20 and the support sheet 18 becomes a black mask, and external light from the observer side is reflected and scattered by the light diffusion plate 16. And there is no reduction in contrast. for that reason,
According to the present invention, it is possible to realize a display device (LCD) capable of obtaining a good contrast ratio over a wide viewing angle.

The support sheet 18 is not particularly limited, and various materials can be used as long as they have sufficient light transmittance and sufficient mechanical strength according to the application. Specifically, various types of glass, polyester, polyolefin, polyamide, polyether, polystyrene,
Various resin materials such as polyesteramide, polycarbonate, polyphenylene sulfide, polyetherester, polyvinyl chloride, and polymethacrylic acid ester are preferably exemplified. Since the light diffusing plate 16 of the present invention, including the light diffusing plate 16a in the illustrated example, may have a rigid plate shape or a flexible sheet or film shape, The material and thickness of the support sheet 18 may be selected depending on the required mechanical strength and use.

In order to further improve the observability of the display device 10, the observation surface (the surface opposite to the beads 20) of the support sheet 18 is provided with a known light non-reflection such as an AR (Anti Reflection) coat. By performing the processing, the light non-reflection processing layer 23
Is preferably provided.

The beads 20 are for forming a diffusion layer and are (substantially) spheres having a light transmitting property and a size that cannot be visually recognized by an observer. Is fixed to the support sheet 18. In the light diffusion plate 16a of the present invention, the beads 20 mainly constitute the structure having the above-mentioned optical refractive index. Therefore, the light diffusion plate 16 a and the like using the beads 20 are arranged and held with the beads 20 facing the liquid crystal panel 12.

The material of the beads 20 is not particularly limited, and various materials can be used as long as they are transparent. For example, the above-mentioned materials of the support sheet 18 are variously exemplified, and particularly, the optical characteristics are excellent. In this respect, a (meth) acrylic resin or glass is preferably used. The size of the beads 20 is not particularly limited, and may be any size that cannot be visually recognized by an observer, depending on the use of the display device 10 or the like, and preferably has a weight average particle diameter of 3 μm to 40 μm. It is more preferable that the thickness be 5 μm to 20 μm. When used as a bead of a light diffusing plate of an image display device according to a third embodiment of the present invention described below, a more preferable bead size is preferably 10 μm to 21 μm.

The binder material constituting the binder 22 is not particularly limited, and various adhesives can be used as long as the beads 20 can be fixed to the support sheet 18. For example, a vinyl acetate resin, ethylene- Vinyl acetate copolymer, vinyl chloride resin, vinyl chloride-vinylidene chloride copolymer, (meth) acrylate resin, butyral resin, silicone resin, polyester resin, vinylidene fluoride resin, nitrocellulose resin, polystyrene resin, styrene- Acrylic copolymers, urethane resins, polyethylene resins, polypropylene resins, chlorinated polyethylene resins, rosin derivatives, and mixtures thereof are preferably exemplified.

Binder 22 used in this embodiment
Has a light absorbing property. As the binder 22, a light-absorbing binder material itself may be used, or a light-absorbing agent such as carbon black may be dispersed in the binder material to give the binder 22 a light-absorbing property.

There is no particular limitation on the method of manufacturing such a light diffusion plate 16a.
May be dispersed and a paint may be prepared, and the paint may be applied to the support sheet 18 and dried (cured), or the binder 22 may be applied to the support sheet 18 and the beads 20 may be spread over the entire surface. Then, the binder 22 may be dried. In this embodiment, since the binder 22 has a light absorbing property, the beads 20 can be uniformly fixed to the support sheet 18 over the entire surface, and preferably all the beads 20 are not buried in the binder 22. Bead 2
It is necessary to adjust the amount of the binder 22 so that 0 is exposed from the binder 22 more than half. Further, the binder 22 may be dried after the beads 20 are brought into contact with the support sheet 18 by pressing the beads 20 or settling by gravity as needed.

FIG. 2B is a conceptual cross-sectional schematic view of another embodiment of the light diffusing plate of the present invention. The light diffusing plate 16b shown in the figure uses a non-colored, that is, a positive-type photosensitive material, for example, a positive-type photosensitive heat-developable material. A photosensitive material layer (photosensitive thermal development material layer) 24 is formed, exposed and developed to form a black mask. The light diffusing plate 16b shown in FIG. 2B and the light diffusing plate 16c shown in FIG. 2C described later have many components similar to the light diffusing plate 16a shown in FIG. Since they are the same, the same components are denoted by the same reference numerals, and the following description mainly focuses on different parts.

The light diffusion plate 16b shown in FIG.
A black-colored photosensitive material layer on the support sheet 18;
For example, a photosensitive heat developing material layer (hereinafter, referred to as a coloring material layer) 2
4, the beads 20 are fixed on the coloring material layer 24, and the coloring material layer 24 is not colored in a region where the light refracted by the beads 20 passes (passing region). . Therefore, the collimated light carrying the image passing through the liquid crystal panel 12 is also transmitted to the beads 20 by the light diffusing plate 16b, as in the embodiment shown in FIG.
And is suitably diffused by passing through the non-color-forming portion (light-passing region) of the color-forming material layer 24, and the color-forming material layer 24 becomes a black mask (light non-passing region). A display device 10 (LCD) that can obtain a good contrast ratio over a wide viewing angle without a decrease in contrast due to reflection and scattering of light can be realized.

A photosensitive material which is a positive type color forming material for forming the color forming material layer (photosensitive heat developing material layer which is a photosensitive material layer) 24, for example, a photosensitive heat developing material, is such that an exposed portion is not colored by exposure. Then, by heating, it is developed by heat or a chemical reaction, and the non-exposed part develops a color, becomes a light shielding part (light non-passing area), and the non-colored exposed part becomes a light transmitting part (light passing area). It is a material to become.

Preferable examples include a thermoresponsive microcapsule containing an electron-donating colorless dye, a compound having an electron acceptor and a polymerizable vinyl monomer in the same molecule, and a coloring material containing a photopolymerization initiator. Is exemplified.
Note that, in this coloring material, these compounds and the photopolymerization initiator exist outside the thermoresponsive microcapsules. The coloring material is cured (polymerized) and fixed by heat to a composition (hereinafter referred to as a curable composition) outside the thermoresponsive microcapsules, and has mobility (not fixed) by heating. ), A compound having an electron acceptor and a polymerizable vinyl monomer as described above or an electron acceptor compound moves in the coloring material to form a colorless electron-donating dye in the microcapsule to form a positive image. This is the recording material to be used.

This coloring material is disclosed in JP-A-10-226174.
The details are described in Japanese Patent Publication No. In addition, other than this, if the photosensitive material is a positive photosensitive material, JP-A-3-87827 and JP-A-4-87827 can be used.
The color forming material (photosensitive heat-developable recording material) disclosed in Japanese Patent Application Laid-Open No. 21252 can also be suitably used.

Such a light diffusing plate 16b can be manufactured as follows. First, the support sheet 18
Then, the coloring material layer 24 is applied by dissolving or dispersing it in a solvent as necessary, and dried. Next, the beads 20 are fixed on the coloring material layer 24. For example, a coating material in which beads 20 are dispersed in a binder 25 is applied,
After applying 5, the beads 20 are scattered over the entire surface, the binder 25 is dried, and the beads 20 are fixed. Prior to the fixing of the beads 20, the binder 25 is fixed in the same manner as in the above-described example.
The beads 20 and the coloring material layer 24 may be brought into contact with each other by pressing or settling the upper beads 20.

After the beads 20 are fixed, collimated light, preferably collimated light similar to that emitted by the backlight unit 14, is incident from the beads 20 side. Thereby, the light incident on the beads 20 is refracted, and (in addition,
The light which does not enter the beads 20) also enters the coloring material layer 24,
The area is exposed. That is, only the region of the color forming material layer 24 through which light passes is exposed, and becomes a light passing region that does not develop color even when developed. The light passing (transmitting) region including the contact region between the beads 20 and the coloring material layer 24 and the vicinity thereof is exposed, and the region other than the light transmitting region, which constitutes the light non-passing (shielding) region, is not exposed. However, this is because the light incident on the beads 20 is condensed on the light passing area by the beads 20, so that the coloring material layer 24 in the light passing area can be exposed, but the light incident on the light non-passing area is
This is because the color forming material layer 24 in the light non-passing area cannot be well exposed because the light is not collected by the beads 20. Next, by heating the color forming material layer 24 and developing it by heat or a chemical reaction, only the unexposed portions develop color,
It becomes a light non-passing area, and the exposed part becomes a light passing area.
The color development by this thermal development is, as described above, the bead 20.
This is only the region through which the light refracted by the light, that is, the diffused light does not pass. Therefore, the coloring material layer 24 suitably functions as a black mask that absorbs external light from the observer side.

In the present embodiment (further, an embodiment shown in FIG. 2C described later), when the binder 25 is used for fixing the beads 20, the binder 25 is made of a material having a light transmitting property, particularly, a colorless and transparent material. Preferably, for example,
Various materials exemplified as the binder material of the binder 22 of the light diffusion plate 16a can be used. Further, although not particularly limited, when the binder 25 is used for fixing the beads 20, the beads 20 and the binder 25 are used.
It is preferable that the difference in refractive index is small, and it is particularly preferable that the difference in refractive index is 0.1 or less. Thereby, light reflection at the interface between the two can be prevented, and more suitable image observation becomes possible. Further, in both embodiments, the amount ratio between the binder 25 and the beads 20 is not particularly limited. However, the weight ratio is set to 1 to 5 in terms of the surface state and the brightness of the light diffusion plate surface during image display. Is preferred. In this embodiment, since the binder 25 is light-transmitting, the beads 20 may be buried in the binder 25.

FIG. 2C is a conceptual cross-sectional schematic view of another embodiment of the light diffusing plate of the present invention. The light diffusing material plate 16c shown in the figure uses a light-absorbing, preferably black, heat-sensitive ablation material instead of the coloring material layer 24, and uses the ablation layer 26 formed thereby as a black mask. Other than this, it has basically the same configuration as the diffusion plate 16b of FIG. 2B described above,
Further, it can be similarly manufactured.

That is, after the ablation layer 26 made of a heat-sensitive ablation material is formed on the support sheet 18, the beads 20 are fixed similarly to the light diffusion plate 16b. Thereafter, collimated light is irradiated from the bead 20 side. As a result, the light or the like refracted by the beads heats the thermal ablation material, and the thermal ablation material in that region is removed by ablation, and only in the region through which light does not pass, the ablation material remains, suitably acting as a black mask. An ablation layer 26 is formed.

In the present invention, the heat-sensitive ablation material that can be used is not particularly limited, as long as it can form a light-absorbing layer, preferably a black layer, and can generate ablation satisfactorily by heating with light. Various materials are available. Specifically, a material which contains a dye and a light absorbing substance in a color-forming layer described in British Patent Application No. 2,083,726 and evaporates the dye by heating, US Pat. No. 5,429, No. 909, a material having a color-forming layer containing an image dye, an infrared absorbing substance, and a binder;
Nos. 73 and 9-104174, resin materials such as nitrocellulose, propioncellulose acetate, and cellulose acetate; infrared absorbing substances such as carbon black; or foaming agents (such as azide) and accelerators Materials containing an ablation enhancer such as (4,4′-diazidobenzophenone and 2,6-di (4-azidobenzal) -4-methylcyclohexanone) are exemplified.

As shown in FIGS. 3A and 4A, when the color forming material layer 24 serving as a black mask is formed by a relatively high-sensitivity positive photosensitive material by a self-alignment process, beads are used. Since a portion of the gap between the beads 20 and the beads 20 is exposed, light is transmitted after development. This is because the coloring material layer 24 does not serve as a black mask, and the diffusion plates 16d and 16e shown in FIGS. 3B and 4B impair the function expected as a black screen. It is necessary to take measures to eliminate it.

For this reason, the diffusion plate 16d shown in FIG.
When the diffusion plate 16e shown in FIG. 4A is manufactured, the coloring material layer (photosensitive material layer) 24 itself or an upper layer thereof (a layer close to the exposure light source), for example, the binder 25, is exposed to a medium of exposure light. , That is, a layer having a medium density for exposure light. In order to form the coloring material layer 24 itself or the binder 25 above it as such a layer having a medium concentration, the material itself forming the coloring material layer 24 or the binder 25 itself above it has a medium density. Although a material having a concentration may be used, an absorber which absorbs exposure light to a moderate degree may be added to the color forming material layer 24 or the binder 25 thereon.

As a result, the space between the beads 20 (for example, the coloring material layer 24 shown in FIG.
The binder 25) has a medium density and a large thickness, so that the exposure light is attenuated, and does not sufficiently expose the photosensitive material of the coloring material layer 24, and develops a color after development to block visible light. Become like On the other hand, the light transmitted through the beads 20 is thin because the color-forming material layer 24 shown in FIG. 3A or the binder 25 shown in FIG.
The photosensitive material of No. 4 was exposed and did not develop color after development, and
Since the light-absorbing layer is thin, the desired function of light transmittance is not impaired.

Accordingly, the diffusion plate 1 as shown in FIG.
In the case of manufacturing 6d, as a binder for bonding the beads 20 to the transparent support sheet 18, it has a medium density at the photosensitive wavelength, and after being developed by heat or a chemical reaction, has a high density in the visible light region. A color-forming photosensitive material is used. For example, first, a coloring material layer 24 made of a photosensitive material having such characteristics is applied on a transparent support sheet 18, and the beads 20 are scattered over the coloring material layer 24, and the beads 20 are pressed as necessary. After being brought into contact with the support sheet 18 by settling or settling, the coloring material layer 24 is dried, and the beads 20 are adhered and fixed to the supporting sheet 18 by the coloring material layer 24.

Thereafter, as shown in FIG. 3A, when collimated light is incident as exposure light from the bead 20 side, the light incident on the bead 20 is refracted, and the light between the bottom of the bead 20 and the support sheet 18 is formed. The light enters the region of the thin color-forming material layer 24 between them or near the contact portion between them. The coloring material layer 24 in this region also has a medium density but is thin, so that exposure light is sufficiently irradiated, and that region is sufficiently exposed. At this time,
Exposure light is also incident on the coloring material layer 24 in the gap between the beads 20, but since the coloring material layer 24 in this gap is thick,
It is not sufficiently exposed and remains as an unexposed area.

Thereafter, by heating the color-forming material layer 24 and developing it by heat or a chemical reaction, only the unexposed areas are colored with a high density and become light non-passing areas, and the exposed areas are not colored. It becomes a light passage area. In this way, as shown in FIG. 3B, a diffusion plate 16d in which the coloring material layer 24 that has developed a high density functions as a black mask is manufactured. FIG.
As shown in (C), by using the diffusion plate 16d thus obtained, the light carrying the image transmitted through the liquid crystal panel 12 is refracted by the beads 20 and is sufficiently diffused.
On the other hand, the coloring material layer 24 functioning as a black mask
External light from the support sheet 18 side (observer side) is well absorbed.

The diffusion plate 16 shown in FIG.
e, first, the transparent support sheet 18
After being developed by heat or a chemical reaction, the color-forming material layer 24 is a layer made of a photosensitive material that develops a high-density color in the visible light region.
And a resin 30 having a medium concentration at the photosensitive wavelength as a binder 30 on the beads 2.
0 is adhered and fixed. Thereafter, as shown in FIG. 4A, when collimated light is incident as exposure light from the bead 20 side, the light incident on the bead 20 is refracted, and the light between the bottom of the bead 20 and the coloring material layer 24 is removed. Alternatively, the light enters the region of the thin binder 30 near the contact portion between them. Although the binder 30 in this area has a medium density, the exposure light is transmitted because the binder 30 is thin, and the color forming material layer 24 under the area is sufficiently exposed. At this time, the exposure light also enters the binder 30 in the gap between the beads 20, but since the binder 30 in this gap is thick, the coloring material layer 24 thereunder is not sufficiently exposed, and the unexposed area is not exposed. Remains as.

Thereafter, by heating the color-forming material layer 24 and developing it by heat or a chemical reaction, only the unexposed area is colored with a high density and becomes a light non-passing area, and the exposed area is not colored. It becomes a light passage area. In this way, as shown in FIG. 4B, the diffusion plate 16e in which the coloring material layer 24 that has developed a high density functions as a black mask is manufactured. FIG.
As shown in (C), by using the diffusion plate 16e thus obtained, the light carrying the image transmitted through the liquid crystal panel 12 is refracted by the beads 20, and is sufficiently diffused.
On the other hand, the coloring material layer 24 functioning as a black mask
External light from the support sheet 18 side (observer side) is well absorbed.

By the way, as shown in FIGS. 5A to 5C, prior to fixing the beads 20, the beads 20 are fixed as described above.
The beads 20 on the layer 32 that contacts the support sheet 18 may be pressed or settled to contact the support sheet 18. That is, as shown in FIG. 5A, the contact layer 32 with the beads 20 is formed on the support sheet 18, for example, the binder 22 shown in FIG. 2A or the color forming material layer 24 shown in FIG. After being formed by coating or the like, as shown in FIG. 5B, the beads 20 are scattered over the entire surface of the contact layer 32. Next, the beads 20 on the contact layer 32 are pressed or settled, so that the beads 20 can be brought into contact with the support sheet 18 as shown in FIG. 5C. Although not shown, the beads 20 are fixed to the coloring material layer 24 (see FIG. 2B), the ablation layer 26 (see FIG. 2C), the coloring material layer 24 (see FIG. 4A), and the like. Prior to this, the beads 20 on the binder 25 (see FIGS. 2 (B) and 2 (C)) and the binder 30 (see FIG. 4 (A)) are pressed or settled to form a lower layer. Coloring material layer 2
4 and the ablation layer 26. The light diffusing plate of the first embodiment of the present invention and the display device of the second embodiment of the present invention are basically configured as described above.

Next, an image display device according to a third embodiment of the present invention will be described in detail with reference to FIGS. FIG. 6 conceptually shows an example of an image display device to which the present invention is applied. Since the image display device 40 shown in FIG. 6 has the same components as those of the image display device 10 shown in FIG. 1 except for a part, the same components are denoted by the same reference numerals, and details thereof will be described. Detailed description is omitted, and different portions will be mainly described.

The image display device 40 shown in FIG. 6 is a so-called liquid crystal display (LCD) using the liquid crystal panel 12 as an image display means. Image display device 40
Is a liquid crystal panel 12, a backlight portion 14a for entering light into the liquid crystal panel 12, a light diffusion plate 16f attached to a surface of the liquid crystal panel 12, and diffusing light carrying an image passing through the liquid crystal panel 12, Further, it has an external light scattering prevention sheet 42 stuck thereon. The liquid crystal panel 12 is provided with a color filter (not shown) having a matrix structure, and a driver (not shown) for driving the liquid crystal panel 12 is connected. Various members of the LCD are arranged as needed.

In the present embodiment, the image display device 40
Although a LCD is used as a display device, the display device is not limited to the LCD, and may be a CRT or a PDP as long as it has a matrix structure. As long as the backlight unit 14a can emit a sufficient amount of light for image observation, various light source devices including the above-described backlight unit 14 for emitting collimated light can all be used. The light emitted from the backlight unit 14a does not need to be particularly collimated light. Rather, in order to suppress pixelization (depixelization),
Since it is better to diffuse the light to blur the image, it is preferable not to use collimated light.

The light diffusing plate 16f has an optical refracting power (optical power), and has a fine, spherical or other structure that cannot be visually recognized by an observer of the image display device 40. ing. FIG. 7 shows a conceptual diagram of an example of the light diffusion plate 16f. The light diffusion plate 16f shown in FIG. 7 has a configuration in which a light-transmitting sphere (hereinafter, referred to as beads 20) is fixed to a light-transmitting support sheet 18 with a binder 44. The beads 20 are partially in contact with the support sheet 18.

In the present embodiment, as described above, the backlight light is not particularly collimated.
By using a light transmissive material for the binder 44, as shown by an arrow in FIG. 7, light carrying an image, which has passed through the liquid crystal panel 12, is incident on the spherical beads 20 from various directions, Being refracted by the beads 20,
Fully diffused.

The binder 44 is not particularly limited, and various adhesives can be used as long as the beads 20 can be fixed to the support sheet 18. In the present embodiment, the binder 44
Preferably has a light transmitting property. For example, the binder material used for the binders 22 and 25 described above can be used.

FIG. 8 is an enlarged view of the light diffusion plate 12 and the sheet 42 for preventing external light scattering. The external light scattering prevention sheet 42 absorbs light and reduces light transmittance to prevent scattering of external light, and is not particularly limited.
Is preferably subjected to an AR process. External light scattering prevention sheet 4
For example, VDT (Visual Display Ter) used by being attached to a monitor of a personal computer or the like may be used.
minal) filter (filter for visual display terminal) is preferably exemplified.

For example, assuming that the light transmittance of the external light scattering prevention sheet 42 is 30%, the light once transmitted through the external light scattering prevention sheet 42 as indicated by an arrow A in FIG. Of (100%), only 30% is transmitted. On the other hand, as shown by an arrow B in FIG. 8, light that enters the external light scattering prevention sheet 42 from the outside, is reflected by the beads 20 of the light diffusion plate 16f, and passes through the external light scattering sheet 42 again is external light. Since the light passes through the scattering sheet 42 twice, its transmittance is 3
30% of 0%, 0.3 × 0.3 = 0.09, 9% more
Becomes Therefore, the transmittance of the reflected external light is reduced by the square of the transmittance of the external light scattering sheet 42, and thus becomes extremely small as described above, and scattering of the external light is effectively prevented.

As described above, in the present embodiment, the light diffusing plate 1
6f is adhered to the surface of the LCD 12 to diffuse light passing through the LCD 12 so that the matrix structure of the LCD 12 cannot be seen, so that a smooth and natural image can be obtained. At this time, by attaching the external light scattering prevention sheet 42 on the light diffusing plate 16f, the external light is prevented from being scattered by the beads 20 of the light diffusing plate 16f to lower the contrast. As a result, depixelization can be performed without lowering the contrast. For example, when applied to medical treatment, a smooth and natural image suitable for diagnosis can be displayed on the image display device.

As described above, the external light scattering prevention sheet has the function of a CRT face plate that intentionally lowers the transmittance and reduces the influence of external light to the square of the transmittance. is there. Instead of attaching the external light scattering prevention sheet on the light diffusion plate, the support sheet of the light diffusion plate may have the function of the external light scattering prevention sheet. In this case, the support sheet may have a light transmittance of, for example, about 30%.

The light diffusing plate and the display device according to the present invention have been described in detail with reference to various embodiments.
The present invention is not limited to these embodiments, and various improvements and design changes may be made without departing from the scope of the present invention. For example, the light diffusing plate also uses beads in this embodiment, but is not limited to this. Further, in the display device according to the second aspect of the present invention, the light diffusion plate or the external light scattering sheet according to the third aspect of the present invention may be applied.

[0059]

As described above in detail, the light diffusing plate according to the first aspect of the present invention has excellent light diffusing performance, and has excellent characteristics with little reflection and scattering of external light. It is a light diffusion plate having. Further, the display device according to the second aspect of the present invention using the light diffusing plate according to the first aspect of the present invention has a wide light diffusing performance and a reduction in external light reflection of the light diffusing plate. The liquid crystal display has a good contrast ratio over a viewing angle and can be suitably used for medical applications.

Further, as described above, according to the third aspect of the present invention, the jaggedness of the displayed image can be eliminated without deteriorating the contrast (depixelization), and a smooth and natural image can be obtained. It can be displayed on an image display device. Therefore, particularly when the present invention is applied to medical treatment, a smooth and natural image suitable for diagnosis can be obtained, and the effect can be particularly exhibited.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view conceptually showing one embodiment of a display device of the present invention.

FIGS. 2A, 2B and 2C are schematic cross-sectional views conceptually showing one embodiment of the light diffusing plate of the present invention.

FIG. 3A is a schematic cross-sectional view conceptually showing an example of a manufacturing process of an embodiment of the light diffusing plate of the present invention, and FIG.
Is a schematic cross-sectional view of the light diffusion plate manufactured in (A),
(C) is a schematic cross-sectional view conceptually showing an example of the usage form.

FIG. 4A is a schematic cross-sectional view conceptually showing an example of a manufacturing process of another embodiment of the light diffusion plate of the present invention;
(B) is a schematic cross-sectional view of the light diffusing plate manufactured in (A), and (C) is a schematic cross-sectional view conceptually showing an example of its usage.

FIGS. 5A, 5B, and 5C are schematic cross-sectional views conceptually showing steps of manufacturing another embodiment of the light diffusing plate of the present invention.

FIG. 6 is a conceptual diagram showing an embodiment of the image display device of the present invention.

7 is a schematic diagram showing a liquid crystal panel and a light diffusion plate of the image display device shown in FIG.

8 is a schematic view showing a light diffusion plate and an external light scattering prevention sheet of the image display device shown in FIG.

[Explanation of symbols]

10, 40 (image) display device 12 liquid crystal panel 14, 14a backlight unit 16, 16a 16b, 16c, 16d, 16e, 16f
Light diffusion plate 18 Support sheet 20 Beads 22, 25, 30, 44 Binder 23 Light non-reflection treatment layer 24 Coloring material layer 26 Ablation layer 32 Contact layer 42 External light scattering prevention sheet

Claims (12)

[Claims] An invisible structure having an optical refracting power, a passing area through which parallel light mainly entering from the invisible structure side passes, and a relatively large area compared to the passing area. A light diffusion plate having a low light transmittance and a non-passing area other than the passing area, wherein the material of the passing area and the material of the non-passing area are simultaneously applied. 2. A light-transmitting support, and a light-transmitting sphere forming the passing area are fixed to a light-absorbing binder forming the non-passing area. The light diffusion plate according to claim 1, further comprising a diffusion layer formed. 3. A light-transmitting support, a diffusion layer having a light-transmitting sphere, and a photosensitive heat-developable material layer formed between the support and the diffusion layer. The heat-developable material layer is characterized in that the exposed portion is made of a non-color-developed photosensitive heat-developable material, and the photosensitive heat-developable material is heated and colored after substantially parallel light is incident from the diffusion layer side. Light diffusion plate. 4. A light-absorbing layer comprising: a light-transmitting support; a diffusion layer having light-transmitting spheres; and a thermal ablation layer formed between the support and the diffusion layer. A light comprising an absorptive thermal ablation material, wherein the thermal ablation material in a region irradiated with light by entering substantially parallel light from the diffusion layer side is removed by thermal energy of light. Diffuser. 5. A light-transmitting support, and a diffusion layer comprising a light-transmitting sphere, wherein the material in contact with the sphere comprises a light-sensitive material and a light-absorbing material whose exposed portion is non-colored. A light diffusing plate, wherein the photosensitive material is colored by heating and developing after substantially parallel light is incident from the diffusion layer side. 6. A light-transmitting support and a diffusion layer comprising a light-transmitting sphere, wherein the material in contact with the sphere includes a light-absorbing material, and the material in contact with the sphere and the support A light diffusion plate, wherein a non-colored photosensitive material is disposed between the body and an exposed portion, and the photosensitive material is colored by heat development after substantially parallel light is incident from the diffusion layer side. 7. The light diffusion according to claim 2, wherein the diffusion layer is formed by first forming a layer of a material in contact with the sphere, and then embedding the sphere. Board. 8. The light diffusing plate according to claim 2, wherein a surface of the support opposite to the diffusion layer is subjected to a light non-reflection treatment. 9. A liquid crystal display panel, and a backlight unit for entering parallel light into the liquid crystal display panel;
A display device, comprising: the light diffusion plate according to claim 1, which is disposed on a side opposite to the backlight unit with respect to the liquid crystal display panel. 10. An image display apparatus comprising: a light diffusing plate having an optically refracting power and having an invisible structure, which is disposed on an observation side of a display screen of an image display device having a matrix structure. 11. The light diffusing plate comprises: a light-transmitting support;
The image display device according to claim 10, further comprising: a diffusion layer formed by fixing a light transmitting sphere to a binder. 12. The image display device according to claim 10, wherein an external light scattering prevention sheet is further provided on the light diffusion plate provided on the observation side of the display screen.