JPH05113606A - Reflection type screen - Google Patents

Abstract

PURPOSE:To provide the screen which is small in light scattering in a perpendicular direction and is bright by constituting the screen of an anisotropic light scattering material formed by dispersing materials varying in refractive index into a transparent matrix. CONSTITUTION:This screen is constituted of the anisotropic light scattering material formed by homogeneously dispersing the materials having anisotropic shapes and having the refractive index different from the transparent matrix into the transparent matrix in the positional relation of the materials moving in parallel with each other in good order. The transparent matrix may be any transparent blank materials. The transparent matrix and the materials having the anisotropic shapes vary in the refractive index from each other and are not compatible with each other. The difference in the refractive indices is at least 0.001. The anisotropic shapes have preferably an ellipsoidal body of revolution or rectangular parallelepiped or the shape of intermediate of both. The anisotropy of the scattering of the transparent light is higher as the anisotropy of the shape is larger, i.e., as the ratio between the major axis and the minor axis thereof is larger in the case of the ellipsoidal body of revolution. The particle size of the materials having the anisotropic shapes is 0.1 to 100mum and the ratio value between the max. diameter and the min. diameter is larger than 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective screen for a projector.

[0002]

2. Description of the Related Art Recently, a magnified projection has been used as a display device for projecting a cathode ray tube image or an image formed by liquid crystal on a screen. The reflection type screen used at this time is composed of a diffusion film and a reflection film,
It has the role of scattering the light emitted from the projector to the observation side.

[0003]

The conventional reflection type screen has a problem that the screen becomes dark because it is widely scattered in the horizontal and vertical directions. This is because the diffusion film has an inorganic filler added for diffusion,
Therefore, it spreads widely in the horizontal and vertical directions.

[0004]

In view of the above circumstances, the inventors of the present invention have diligently studied a reflection type screen having a bright screen by reducing vertical scattering, and as a result, have a required performance and stably. Moreover, the inventors have found a material that can be easily manufactured, and have further completed various studies to complete the present invention.

That is, according to the present invention, a substance having an anisotropic shape and a refractive index different from that of the transparent matrix is homogeneously dispersed in an orderly parallel positional relationship with each other. Provided is a reflective screen composed of a directional light scattering material.

The present invention will be described in detail below. The transparent matrix used in the present invention is not necessarily limited as long as it is a transparent material, and can be selected from a wide range of materials.

For example, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and partially or fully saponified product thereof, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acetic acid. Vinyl-methyl methacrylate copolymer, polypropylene, olefin resin such as propylene-α-olefin copolymer, vinyl chloride resin such as polyvinyl chloride resin, acrylonitrile resin such as acrylonitrile-styrene copolymer, polystyrene, Styrene-based resins such as styrene-methyl methacrylate copolymers, acrylic ester polymers such as polyethyl acrylate, methacrylic acid ester polymers such as polymethyl methacrylate, those copolymers and other copolymerization components Added (meth) acrylate resin Polyester resins such as polyethylene terephthalate, polyamide resins such as nylon, polycarbonate resin, ethyl cellulose, cellulose resins such as acetyl cellulose, polyurethane resins, and silicone resins.

Next, a substance having an anisotropic shape used in the present invention and a method of dispersing the substance in a transparent matrix will be described.

The transparent matrix and the substance having an anisotropic shape have different refractive indexes and are incompatible with each other. The difference in refractive index between the transparent matrix and the material having an anisotropic shape is at least 0.001.
And preferably 0.01 or more.

Examples of the anisotropic shape include a spheroid, a rectangular parallelepiped, an intermediate shape between them, and a cylindrical shape.
Preferred are those having a spheroid, a rectangular parallelepiped, or an intermediate shape between them.

The condition required in terms of shape must not be an isotropic shape, but a completely amorphous shape is not effective. The greater the shape anisotropy, that is, the greater the ratio of the major axis to the minor axis of a spheroid, and the greater the ratio of the long side to the short side of a rectangular parallelepiped, the greater the scattering of transmitted light. The orientation will also be more advanced.

The particle size of a substance having an anisotropic shape is 0.
It is 1 to 100 μm, preferably about 0.5 to 70 μm, and the ratio of the maximum diameter to the minimum diameter is larger than 1.

The substance having an anisotropic shape may be the same material as the above-mentioned matrix, and need not be transparent.

It is essential that these substances having anisotropic shapes are dispersed in the transparent matrix in a positional relationship in which they are regularly parallel to each other. That is,
For example, in the case of a spheroid, the directions of its major axes are made uniform, and in the case of a rectangular parallelepiped, the directions of the corresponding sides of the rectangular parallelepiped are made to coincide.

The method of arranging the anisotropically shaped substances in an orderly manner as described above includes, for example, compounding a transparent polymer compound with an anisotropically shaped substance and molding it into a film or sheet. However, a method of stretching in a uniaxial direction or the like can be considered. However, this method is inferior in production stability and is not necessarily preferable from the industrial viewpoint.

In the present invention, industrially useful methods were examined and the following novel production methods were found. That is, in the method for producing an anisotropic light-scattering material that constitutes the present invention, at least one of two or more phase-separated resins that have different refractive indexes and form a matrix and an anisotropic shape is transparent. A resin is a method in which a composition obtained by kneading these resins is extrusion-molded and then stretched in a uniaxial direction. According to this method, in the kneading stage, the dispersed particles that are the islands have an isotropic shape (spherical shape), but when the stretching process is performed, the dispersed particles that are the islands have a long axis in the stretching direction. It is transformed into a spheroidal anisotropic shape, and is homogeneously dispersed in the matrix in a positional relationship in which they are orderly translated.

The anisotropy of the anisotropically shaped material depends on the discharge amount during stretching,
The shape anisotropy can be changed arbitrarily by depending on the take-up speed, in other words, by appropriately setting these processing conditions.

Examples of such stretching processing include inflation processing and T-die processing. T-die processing is preferable from the viewpoint of setting processing conditions.

The resin composition used in the method for producing the anisotropic light-scattering material constituting the reflective screen of the present invention includes, for example, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and Partially or wholly saponified product, ethylene-ethyl acrylate copolymer,
For olefin resins such as ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate-methyl methacrylate copolymer, polypropylene and propylene-α-olefin copolymer, vinyl chloride resin such as vinyl chloride resin, Acrylonitrile-based resin such as acrylonitrile-styrene copolymer, polystyrene, styrene-based resin such as styrene-methyl methacrylate copolymer, acrylic ester polymer such as polyethyl acrylate, and methacrylate ester such as polymethyl methacrylate. Coalescence, (meth) acrylic acid ester-based resins containing these copolymers or other copolymerization components, polyester resins such as polyethylene terephthalate, polyamide resins such as nylon, polycarbonate resins, cellulose resins such as ethyl cellulose and acetyl cellulose. It is preferred to knead a polyurethane resin, a silicone resin or the like.

The olefin resin is, for example, low density polyethylene, more preferably ultra low density polyethylene.

As the resin to be kneaded with the olefin resin, for example, a styrene resin is preferable. Examples of the styrene resin include polystyrene,
More preferred is polystyrene having a molecular weight of 140,000 or less.

The resin is blended in a weight ratio of 95 /
It is 5 to 5/95, preferably 70/30 to 30/70.

The anisotropic shape of the anisotropic light-scattering material obtained by the above manufacturing method is set so that the major axis direction is the vertical direction (vertical direction) of the projector screen.

The reflective screen of the present invention comprises, for example, an anisotropic light-scattering material and a reflective film that reflects the light incident on the anisotropic light-scattering material.

Further, according to the present invention, a reflective screen having an improved contrast can be obtained by combining the polarizing film and the anisotropic light scattering material. Since the light emitted from the projector of the liquid crystal light source is polarized, the brightness of the image on the screen hardly decreases, and the polarizing film reduces the contrast by cutting about 50% of the unpolarized external light. Contribute to improvement.

The polarizing film used in the reflection type screen of the present invention is not particularly limited, but the higher the polarizing property is, the higher contrast can be obtained, which is preferable. The polarizing film has a natural light transmittance of about 50% and a polarized light transmittance of about 9%.
It is preferably 0% or more.

[0027]

Since the reflective screen of the present invention is made of an anisotropic light-scattering material, it exhibits anisotropic scattering and the vertical scattering is small, so that the brightness of the screen can be improved.

[0028]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Preparation of anisotropic light-scattering material Ultra-low density polyethylene with a refractive index of 1.54 (density 0.9
0) 60 parts by weight and 40 parts by weight of polystyrene having a refractive index of 1.59 (molecular weight 95,000) are kneaded, and polyethylene is used as a matrix, and polystyrene is a spherical dispersion (island portion of the sea-island structure). Was prepared. This phase-separated resin composition was supplied to a T-die type extruder having a discharge opening clearance of 0.7 mm and extruded at a melting temperature of 240 ° C. The extruded sheet-shaped molten resin is strongly drawn in the extrusion direction at 15 m / min and cooled while being stretched to obtain a film (thickness 50 μm) of the anisotropic light-scattering material used for the reflection type screen of the present invention. It was

At that time, the spherical dispersion of polystyrene, which is the island portion of the sea-island structure, is transformed into a spheroidal anisotropic shape having a long axis in the stretching direction and is uniformly dispersed in a positional relationship in which they are parallel to each other in an orderly manner. It had been. The anisotropic shape had a major axis of about 20 μm and a minor axis of about 1 μm.

(2) Preparation of reflective screen A reflective screen was prepared by bonding the above anisotropic light-scattering material and an aluminum film (100 μm thick) reflective film with an adhesive. (3) Evaluation of reflective screen The brightness and contrast of the reflective screen were visually evaluated in a dark room and a bright room by projecting from a liquid crystal projector. The results are shown in Table 1. It should be noted that the dark room was completely shielded from outside light, and the bright room was set to a brightness of 1000 lux.

Example 2 A polarizing film (registered trademark Sumikaran SG1852A, manufactured by Sumitomo Chemical Co., Ltd.) was added to the reflection type screen produced in Example 1.
A reflective screen was prepared by bonding P) with an adhesive. The polarizing film used had optical characteristics of 50% natural light transmittance and 90% polarized light transmittance. Table 1 shows the results of evaluation performed in the same manner as in Example 1.

Comparative Example 1 Diffusion film with uneven surface (polycarbonate film,
Film thickness 50μm) and aluminum film (film thickness 100μ
Table 1 shows the results of evaluation performed in the same manner as in Example 1 using the conventional reflective screen composed of m).

[0034]

[Table 1]

Claims (3)

[Claims] 1. An anisotropic anisotropic material in which substances having an anisotropic shape and a refractive index different from that of the transparent matrix are homogeneously dispersed in a positional relationship in which they are parallel to each other in an orderly manner. A reflective screen made of a light-scattering material. 2. A composition in which at least one of two or more phase-separated resins having different refractive indexes and forming a matrix and an anisotropically dispersed substance is a transparent resin is stretched. The reflective screen according to claim 1, which is composed of an anisotropic light-scattering material. 3. The reflection type screen according to claim 1, wherein the anisotropic light scattering material according to claim 1 is combined with a polarizing film.