JPH1020404A - Transmission type projection screen and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection screen which facilitates manufacture, is capable of dealing with a fine pitch, is controllable in light diffusion capability and is capable of making bright and high contrast display by exposing a photosensitive material from its screen printed with a black matrix, thereby developing a lens of a distributed index type. SOLUTION: The front surface of a photopolymer 1 which is the photosensitive material of a type which is provided with PET films 2 as protective layers on both surfaces and is changed in the internal refractive index by exposure is printed with the black matrix(BM) 3 opened with fine openings of circular, elliptic, stripe or other shapes. This photopolymer 1 is sensitized by exposing the material from the printed BM 3 side with the printing patterns of the BM 3 as a mask and, thereafter, the photopolymer is thermally fixed. The refractive index distribution in which the refractive index in the central part of the openings of the BM is high and is successively lower toward the periphery is generated in the photopolymer 1. The projection light 4 entering the screen from its rear surface is condensed by the distributed refractive index type lens effect developed in the photopolymer 1 and is diffused and emitted from the openings of the BM.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type projection screen which can be used for a rear projection television, a liquid crystal display and the like.

[0002]

2. Description of the Related Art Conventionally, rear projection televisions have been
Since the screen is darker than the RT direct-view television, a screen as bright as possible has been demanded. For this reason, a lenticular lens surface shape that reduces the loss of incident light and allows a large amount of light to be emitted only to a specific area on the front and right and left sides has been desired. As such a transmissive projection screen, for example, a Fresnel lens sheet is arranged on the incident light side to make the light parallel, and a lenticular lens is arranged on the outgoing light side, and furthermore, the diffusion of light in the vertical direction is increased. In order to reduce the visibility of a ghost image, a fine horizontal lenticular lens extending horizontally in the incident surface of a Fresnel lens sheet has been proposed.

[0003]

A conventional transmission type projection screen using a lenticular lens is an acrylic resin represented by polymethyl methacrylate, a polystyrene resin, a polycarbonate resin, a polyester resin, or a polyvinyl chloride resin. However, there is a problem that processing is difficult because the resin is manufactured by extrusion molding of a transparent resin such as. Further, the pitch of the unit lenses constituting the lenticular lens is as small as about 0.5 mm even if it is small, and cannot be adapted to a display requiring a fine pitch. Considering the use of a hologram color filter for a liquid crystal display device already proposed by the present applicant in Japanese Patent Application No. 5-12170, the pitch must be 40 μm or less in order to prevent moire. However, this cannot be dealt with.

[0004] In a conventional transmission projection screen,
Although the light diffusion in the horizontal direction is controlled by the lens shape, the light diffusion in the vertical direction cannot be controlled. A method has been proposed in which beads having a different refractive index from a member are put in a screen and light is diffused in the vertical direction, but at the same time, there is a problem that control of light diffusion in the horizontal direction is affected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a transmission type projection which is easy to manufacture, can cope with a fine pitch, can control the light diffusing ability, and can provide a brighter and higher-contrast display. It is an object to provide a screen and a method for manufacturing the screen.

[0006]

The transmission type projection screen of the present invention has fine stripes, circles, ellipses, and other openings on the surface of a photosensitive material in which the refractive index changes internally upon exposure. By printing the black matrix, exposing from the black matrix printing surface side and expressing the refractive index distribution type lens inside, the projection light coming from the back side to the screen is collected by the refractive index distribution type lens, The light is emitted from the opening of the black matrix.

[0007]

Embodiments of the present invention will be described below. FIG. 1 is a view for explaining a method of manufacturing a transmission type projection screen of the present invention. The photosensitive material constituting the screen has a PET film 2 provided on both sides of a photopolymer 1 as a protective layer (FIG. 1A). The photopolymer 1 is a type of photosensitive material whose internal refractive index changes with exposure, such as a photosensitive material for a volume phase hologram.

A black matrix (BM) 3 having fine openings such as a circle, an ellipse, and a stripe is printed on the surface of the photosensitive material (FIG. 1B). The size, shape, and the like of the opening of the BM can be arbitrarily selected depending on the printing technique, and printing can be easily performed. The BM 3 has a function of increasing display contrast when used as a screen while being used as a mask during exposure.

Next, the photopolymer 1 is exposed from the printed BM3 side using the BM3 print pattern as a mask.
Is exposed (FIG. 1 (c)), and then heat-fixed (FIG. 1).
(D)).

When mask exposure is performed in this manner, FIG.
As shown in FIG. 2A, the light that has passed through the BM aperture causes diffraction, so that the amount of light on the photopolymer 1 has a Gaussian distribution as shown in FIG. 2B. Therefore, the photopolymer is exposed with such a distribution that the light amount is large at the center of exposure (the center of the BM opening) and decreases toward the periphery. As a result, the photopolymer 1 has a refractive index distribution having a high refractive index at the center of the BM opening and a lower refractive index toward the periphery as shown in FIG. Therefore, as shown in FIG. 4, the projection light 4 entering the screen from the rear surface is collected by the refractive index distribution type lens effect developed in the photopolymer 1, and is diffused and emitted from the BM opening. .

The light diffusion ability at this time can be determined by selecting the size of the BM opening, the ability of the photosensitive material (the degree of change in the refractive index with respect to the exposure amount), the film thickness, the exposure amount, the heating temperature and time, and the like. You can control.

When the screen of the present invention is compared with a screen using a conventional lenticular lens,
In a conventional screen, as shown in FIG. 5A, external light is reflected on the surface (observer side), and light transmitted from the surface to the inside is scattered inside, and the returned light is emitted from the surface. And was observed together with the display light, leading to a decrease in contrast. On the other hand, in the screen of the present invention, the external light is absorbed by the BM, and at the same time, the return light transmitted through from the surface and scattered inside is also absorbed by the BM.
High-contrast display becomes possible.

In the screen of the present invention, as shown in FIG. 6, since the BM 3 also functions as an exposure mask, it is not necessary to separately prepare a mask for exposure for generating a refractive index distribution.

Further, the screen of the present invention functions as a gradient index lens, and as shown in FIG.
Since the light is condensed and emitted at the center of the M opening, the light is diffused. Therefore, as shown in FIG. 8, if the shape of the BM opening is a stripe shape (FIG. 8A), light is diffused only in a direction orthogonal to the direction in which the stripe extends. B
If the shape of the M opening is circular (FIG. 8B), light is diffused in the same manner in both the vertical and horizontal directions. When the shape of the BM opening is elliptical (FIG. 8C), the diffusion of the ellipse in the minor axis direction is large, and the diffusion in the major axis direction is small, and the diffusion can be varied depending on the direction. In addition, BM
The shape of the opening can be any shape such as a triangle or a square as required. Also, the diffusion of light may be controlled by changing the opening shape depending on the location, such as a circle at the center of the screen and an ellipse or stripe at the periphery.

[0015]

As described above, according to the present invention, a light-sensitive material whose refractive index is changed by exposure is used for a transmission type projection screen, and a fine black matrix is printed on the screen surface to be exposed to light. In addition, a black matrix suppresses surface reflection of external light and scattering from the inside, enabling a high-contrast display, and the black matrix also acts as a mask during exposure. In addition, a fine-pitch screen can be easily manufactured. In addition, since the projection light is condensed by the refractive index distribution type lens effect and exits from the opening of the black matrix, the light diffusion ability can be easily controlled by selecting the size, thickness, exposure amount, and the like of the opening. be able to. In addition, by controlling the shape of the opening of the black matrix to a stripe, a circle, an ellipse, or the like, light diffusion can be controlled only in the vertical or horizontal direction.
It is possible to make the same in the vertical and horizontal directions, and to make it different in the vertical and horizontal directions, and it is also possible to make the light diffusion capability and the light diffusion direction different between the central part and the peripheral part of the screen.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of manufacturing a transmission type projection screen of the present invention.

FIG. 2 is a diagram illustrating light diffraction and light amount distribution due to mask exposure.

FIG. 3 is a diagram illustrating a refractive index distribution.

FIG. 4 is a diagram for explaining condensing of projection light and diffusion of emission light by a gradient index lens effect.

FIG. 5 is a diagram illustrating the enhancement of the contrast of the screen of the present invention in comparison with a conventional screen.

FIG. 6 is a diagram illustrating mask exposure.

FIG. 7 is a diagram illustrating a light collecting function.

FIG. 8 is a diagram illustrating the shape of a BM opening.

[Explanation of symbols]

1 photopolymer, 2 PET film, 3 BM,
4: Projection light.

Claims (4)

[Claims] 1. A screen used in a transmission type projection apparatus for observing projected light through a screen,
While a black matrix is formed on the surface, the refractive index is high at the center of the opening of the black matrix,
A transmissive projection screen, wherein a refractive index distribution having a lower refractive index is formed toward the periphery. 2. A transmission type projection screen according to claim 1, wherein said screen is made of a refractive index modulation type photosensitive material. 3. The transmission type projection screen according to claim 1, wherein the shape of the opening of the black matrix is a stripe, a circle, an ellipse, or a combination thereof. 4. A method of manufacturing a screen used in a transmission type projection apparatus for observing projected light through a screen, wherein a step of printing a fine black matrix on a surface of a photosensitive material whose refractive index changes by exposure, comprises: A method for producing a transmission type projection screen, comprising a step of exposing from a matrix printing surface side and a step of fixing by heating.