JP2001074918A - Light diffusing body and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screen capable of realizing high contrast by preventing peripheral light from being reflected. SOLUTION: Microlenses 10 of 1 to 100 μm are arrayed at random or cyclically on a supporting body 12. The black mask of the microlens array is produced by forming film-state photosensitive material on a surface on the opposite side to a surface where the microlenses 10 are arrayed, and exposing it from a lens surface and developing so that an unexposed part may have a light shielding area (light shielding property) and an exposed part may have a light transmissive area 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffuser and a method for manufacturing the same, and more particularly to a light diffuser used for a screen of a rear projection type display device, a screen of a front projection type display device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a projection type screen, there are a screen of a rear projection type display device and a screen of a front projection type display device. As these screens, there are known fine irregularities having a curved surface on which extrusion molding or the like can be obtained, for example, a screen made of a transparent body in which a large number of convex lenses having a convex shape are repeatedly formed on one surface, so-called lenticular lenses. The light from the projector is projected on the lenticular lens, and the image is viewed from the other surface.

[0003] In these screens, the projection light is converged by the convex lens to focus on a condensed portion corresponding to the optical axis of the convex lens, and thus has high brightness. However, in such a screen, since there is no element that absorbs light from the surroundings by the screen, almost all of the ambient light radiated on the screen is reflected, so that the contrast ratio of the image is limited. Therefore, in order to improve the contrast ratio of the image, an area (black mask) for absorbing light is provided on a portion of the screen opposite to the surface on which the convex lens is formed, where light is not transmitted (light shielding area). Has been done.

Conventionally, as a method of forming the above-mentioned black mask, a method has been proposed in which a concave portion or a convex portion is provided in a stripe shape in a portion other than the light shielding region, and black ink or the like is applied to the concave portion or the convex portion. .

In recent years, as a screen of a rear projection type display device, a screen of a type in which transparent beads are applied and fixed to a white cloth or a metal foil without any gap has been proposed. This utilizes a phenomenon in which the screen gain is higher than that of an isotropically-reflective reflector due to the action of a micro-raise array. Even in the screen of a rear projection display device coated with transparent beads, almost all of the ambient light that irradiates the screen with the light from the surroundings is reflected, so that the contrast ratio obtained with these screens is limited.

Therefore, in order to improve the contrast ratio even in the case of this type of screen, it is desired to form a black mask. However, in the microlens array, since the condensing portions corresponding to the optical axes of the respective lenses are arranged irregularly and innumerably, a black mask is formed by printing or photolithography using a separately prepared pattern. Forming is difficult to perform in a mass production.

[0007]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a light diffuser having a microlens array capable of improving a contrast ratio without impairing the characteristics of the microlens array. is there. Second embodiment of the present invention
An object of the present invention is to provide a method for manufacturing a light diffuser having a microlens array capable of improving the contrast ratio without impairing the characteristics of the microlens array.

[0008]

A light diffuser according to the present invention is a light diffuser that diffuses light from a specific direction and absorbs light from another direction. 1-100
Micro lenses having different diameters of μm are arranged, and a black mask for forming a light shielding area is provided on the surface on the other direction side. It is desirable that the light-shielding region is formed of a photosensitive material. The light diffuser in which microlenses having different diameters of 1 to 100 μm are arranged (random lens array) is not based on so-called “Mie scattering” in which microparticles scatter light. The body diffuses light according to the principle of refraction. From this principle, the light diffuser can diffuse the incident light only in a necessary direction, and exhibit light brightness. In addition, the transmitted light and the reflectance are high, and projection of a high-definition image is possible.

A method for manufacturing a light diffuser according to the present invention is a method for manufacturing a light diffuser for diffusing light from a specific direction and absorbing light from another direction, wherein the surface on the specific direction side is Having a microlens array, forming a film made of a photosensitive material on the surface in the other direction side, exposing light from the specific direction side, making the unexposed part a light-shielding area, and making the exposed part light-transmissive To form a black mask.
The microlens array preferably has microlenses of different diameters of 1 to 100 μm arranged randomly or periodically, and the photosensitive material is preferably a silver salt photosensitive material or a photopolymer. When a film of a photosensitive material such as a silver halide photosensitive material or a photopolymer is formed on the light diffuser included in the microlens array and exposed through the microlens array, a light beam corresponding to the optical axis of each microraise is formed. The light portions are exposed and the other portions are unexposed or lightly exposed portions. Then, by subsequent development, the exposed portion can be a light-transmitting region and the other portions can be light-shielding regions. Therefore, irrespective of the diameter of each lens of the microlens array, the arrangement of the lenses, and the like, the light shielding region can be faithfully formed in a portion other than the converging portion corresponding to the optical axis of each microlens. A light diffuser having a high contrast ratio can be obtained without impairing the characteristics of the lens array.

[0010]

Next, a preferred embodiment of the present invention will be described. FIG. 1 is an explanatory diagram illustrating a method for manufacturing a screen according to the present invention. In FIG. 1, reference numeral 10 denotes a minute lens array, and reference numeral 12 denotes a base. The microlens array 10 is a plate-like or film-like member having a light diffusing function in which microlenses each having a diameter of about 1 to 100 μm are randomly or periodically arranged. 12 are formed on the surface. A black mask 14 is provided on one side of the base 12 described above.
Is provided.

The microlens array 10 is, for example, 1 to 100 μm, preferably 5 to 50 μm on the base 12.
More preferably, it is obtained by fixing transparent beads such as plastic or glass such as acrylic resin of about 10 to 30 μm via a binder such as acrylic. In this case, it is desirable to select the materials of the binder and the beads so that the refractive index of the binder and the refractive index of the beads are as close as possible. When combining beads of different diameters, 5 to 10 μm and 10 to 30 μm
Is desirable. Also, it is desirable that the binder be transparent after solidification.

The base 12 has a plastic film,
Glass and the like can be cited, but the base 12 is not particularly limited as long as it has transparency, has a refractive index similar to that of Haze, and has sufficient strength to provide a microlens array. The microlens array does not necessarily have to be provided on the base, and may be manufactured by the following method. That is, beads of plastic, glass, etc. of about 1 to 100 μm are fixed on a base via a binder, and then a curable material in a fluidized state is brought into contact with the beads, and then the cured product obtained by curing is cast into a mold. Can be used to manufacture a light diffuser having a microlens array. Here, as the curable material, glass, thermosetting resin, room temperature curable resin, and the like can be given. For example, when a UV curable resin is poured into a mold formed of the curable material and cured by UV light irradiation, an intended light diffuser is obtained. Therefore, this method is particularly suitable for mass-producing the light diffuser.

The microlens array is not based on the so-called "Mie scattering" in which microparticles scatter light, but a microstructure acting as a lens diffuses light based on the principle of refracting light. From this principle, the light diffuser can be designed to diffuse the incident light only in the required direction. Also, the size of each lens is 1 to 1
When the lenses are made to be about 00 μm and their lenses are randomly or periodically arranged on the surface, 1) only image light can be diffusely reflected or diffusely transmitted in the direction of viewing and viewing, 2) transmittance. And reflectivity can be increased,
3) For projecting a high-definition image, there is an advantage that the structure of the reflection surface or the transmission surface is minute.

Further, the micro lens array can be obtained by the following method. A method can be used in which a curable liquid is brought into contact with a mold having a surface shape designed so that an intended light diffusion function is exhibited, and solidified by a method suitable for the material. Therefore, this method
Unlike the method described above, it is possible to produce a material having a surface shape other than a spherical surface. For example, it is also possible to make the surface shape elliptical so that the diffuse arrangement of the reflected and transmitted light is wide left and right so as to meet viewing conditions and narrow vertically.

For example, the following method is suitably applied. The mold resin material is cast on a prototype having irregular irregularities on the surface, and then the mold is released to stretch the mold onto which the minute irregularities have been transferred. After curing, a replica (light diffuser) can be obtained by releasing the mold.

In this method, the means for forming irregular irregularities on the surface include: (1) a method for roughening a smooth surface, for example, a method for polishing a smooth surface of glass, ceramics, plastic, or the like with abrasive grains or sandblasting. Polishing or etching, (2) engraving a smooth surface, for example,
A method of engraving a wax surface with a sharp needle, (3) a method of coagulating a fine solid from a gas or a liquid on a substrate having a smooth surface, for example, a method of vapor deposition on a smooth substrate,
Alternatively, an extremely fine mist of a solid solution or dispersion is sprayed on a substrate, and then a solvent or a dispersion is evaporated to aggregate fine solids on the substrate surface,
(4) A method of spreading fine powder on a substrate having a smooth surface, and (5) Wrinkles (reticulation) generated in a coating layer.
(6) a method using various existing materials,
For example, a method using the surface of each part of an organism other than the surface of paper, leather, cloth, plate glass, wood board, rock, and (7) applying a photopolymer to a substrate having a smooth surface and then exposing to a non-uniform pattern Then, there is a method of utilizing the developed surface.

However, in general, only the microlens array 10 has no element that absorbs ambient light other than the light projected onto the screen, so that ambient light is reflected and the contrast ratio of the image is reduced, and the image is blurred. Therefore, the black mask 14 is so formed as to absorb light in a portion other than the optical path of the image light.
Is formed. Therefore, the ambient light is absorbed by the black mask 14, the reflection of light on the screen surface is suppressed, and the contrast ratio of the image on the screen surface is improved.

Next, a specific method of manufacturing the black mask 14 will be described. In this method, as shown in FIG. 1, a photosensitive material is applied to the smooth surface side of the base 12 or the microlens array as needed, and a portion irradiated with light in an exposure step becomes transparent after being developed. The black mask 14 can be obtained by using a positive photosensitive material.

Examples of the photosensitive material include a silver salt photosensitive material and a photopolymer. When exposure is performed with the photosensitive material film formed on the surface of the base 12, a condensing portion corresponding to the optical axis of each lens of the microlens array 10 is exposed as shown in FIG. 1, and other portions are not exposed. Or a portion where the exposure amount is small. Here, in the case of a silver halide photosensitive material, a treatment is performed so that only the exposed portion is desalted, and again
By a known reversal developing method in which the entire surface is exposed and developed by a conventional method, the exposed portion becomes a light transmissive region 16 and the other portion becomes a light shielding region, and the black mask 14 is formed.
In the case of a photopolymer, the polymer in the exposed portion is polymerized or decomposed, and a change in tackiness, a change in solubility in a developing solution, a change in permeability of a microcapsule wall, and the like can be performed. can do. Specific examples of these are disclosed in, for example,
No. 7827, JP-A-4-21252, JP-A-10-
An image recording method utilizing a phenomenon in which polymerization by light irradiation is started as described in JP-A-226174 or the like is exemplified.

In FIG. 1, the film of the photosensitive material 14 is
However, when the microlens array 10 has a small radius of curvature of about 10 μm, it is difficult for the condensing portion corresponding to the optical axis of the lens to reach the film surface of the photosensitive material. In such a case, it is necessary to form a photosensitive material film between the microlens array 10 and the base 12.
In this case, when developing the photosensitive material, the chemicals may not reach the photosensitive material film. However, if the photosensitive material of the heat development type is used, the light is irradiated from the microlens array side, and then the heat development is performed. A black mask is obtained. Examples of such a heat-developable photosensitive material include:
For example, there is a material system in which microcapsules containing a color former are present in a matrix having photopolymerizability and a color developing function.

The screen shown in FIG. 2A is a rear projection type screen, while FIG. 2B shows an example of a front projection type screen. In FIG. 2B, FIG.
The difference from the screen shown in (A) is that the reflection layer 18 is formed on the black mask surface. FIG.
In the screen shown in FIG. 3B, since the reflection layer 18 is formed, the light of the light-exposed portion (light transmissive area) from the microlens array is projected on the front surface via the reflection layer 18. Here, for the reflection layer 18, for example, a white powder layer of titanium oxide or the like, a metal powder layer, unevenness or a smooth metal surface, or the like can be used.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below.

(Example 1) <Utilization of silver salt photosensitive material> A solution prepared by suspending 2 parts by weight of acrylic beads having a diameter of 30 μm to 50 μm in a methyl ethyl ketone solution of 1 part by weight of an acrylic resin binder was applied to one side of a 30 μm polyester film. After drying, a microlens array was prepared. A black-and-white silver halide photosensitive emulsion layer having a thickness of 5 μm was provided on the surface of the film opposite to the lens array. The film was exposed to substantially parallel white light from the lens array side, and subjected to a reversal development process known as a residual method to obtain a transmission type light diffuser. This light diffuser exhibited a characteristic of transmitting 80% of light from the lens array side and transmitting 30% of light incident from the opposite surface.

(Example 2) <Utilization of heat-developable microcapsule photosensitive material> 100 μm
On one side of a thick polyester film, Japanese Patent Application Laid-Open
A photosensitive layer was provided in the same manner as in Example 1 of No. 6174. 20μ with polyvinyl alcohol as a binder
An acrylic bead suspension having a diameter of m was applied and dried to prepare a microlens array. A black-and-white silver halide photosensitive emulsion layer having a thickness of 5 μm was provided on the surface of the film opposite to the lens array. After drying, substantially parallel white light was exposed from the lens array side at an energy of 10 mJ / cm ² . This film was heated to 120 ° C. for 5 seconds to obtain a transmission type light diffuser. This light diffuser is used to reduce the light from the lens array side to 85
%, And 15% of light incident from the opposite surface.

[0025]

According to the light diffuser of the first aspect, the reflection of ambient light can be suppressed without impairing the characteristics of the microlens array, such as high luminance, so that the contrast ratio of the image can be increased. it can. According to the method for manufacturing the light diffuser according to the third aspect, the light-shielding region can be reliably formed in a portion other than the focal portion of each lens of the microlens array by the optical axis. A high light diffuser can be reliably and easily manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a light diffuser having a black mask according to the present invention.

FIG. 2A shows an embodiment of the light diffuser of the present invention, and is a cross-sectional view of the light diffuser for a rear projection screen.
(B) shows another embodiment of the light diffuser of the present invention, and is a cross-sectional view of the light diffuser for a front projection screen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Micro lens array 12 Base 14 Black mask 16 Light transmissive area 18 Reflective layer

Claims (6)

[Claims] 1. A light diffuser for diffusing light from a specific direction and absorbing light from another direction, wherein micro lenses having different diameters of 1 to 100 μm are arranged on the surface on the specific direction side. And a black mask for forming a light shielding region on the surface on the other direction side. 2. The light diffuser according to claim 1, wherein the light shielding area is formed of a photosensitive material. 3. A method for manufacturing a light diffuser for diffusing light from a specific direction and absorbing light from another direction, wherein the surface on the specific direction side has a microlens array, A film made of a photosensitive material is formed on the surface on the side of the direction, light is exposed from the specific direction side, an unexposed portion is developed into a light-shielding region, and the exposed portion is developed so as to be light transmissive to form a black mask. A method for producing a light diffuser. 4. The microlens array is 1 to 100 μm.
The method for producing a light diffuser according to claim 3, wherein the microlenses having different diameters are randomly or periodically arranged. 5. The method according to claim 3, wherein the photosensitive material is a silver salt photosensitive material. 6. The method for manufacturing a light diffuser according to claim 3, wherein the photosensitive material is a photopolymer.