JPH0238936B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a black stripe type lenticular screen. For example, a lenticular lens is used as a transmission screen for a projection television.
There is a band on the back side that does not transmit the image light, which absorbs external light.
Screens with so-called black stripe types are often used. Transparent synthetic resins, particularly polymethyl methacrylate and polystyrene, are preferred as materials for this type of screen because of their ease of molding and light weight. In order to improve the quality of the image seen through the screen, it is preferable to use a lenticular lens with a fine lens pitch, that is, a lenticular lens in which lenses with a small radius of curvature are closely arranged. On the other hand, due to the structure of a black stripe type screen, the smaller the lens pitch, the thinner the screen must be. This not only makes molding difficult, but also reduces the strength of the screen. The purpose of the present invention is to solve these problems and provide a lenticular screen with sufficient thickness at a low cost without changing the diffusion angle of light passing through the screen. . The screen of the present invention is a transmission type screen that uses a lenticular lens, and is a black stripe type lenticular screen in which a band that absorbs external light is provided on the back surface that does not transmit image light. Consisting of two layers, the layer on the lenticular lens surface uses an optical material with a small refractive index, and the base layer on the back side uses an optical material with a high refractive index. thickness and base layer thickness,
The lens pitch is selected depending on the combination of the lens pitch and the refractive index of the optical materials of both layers, so that the focal point of the image light almost coincides with the exit surface. Here, when the refractive index of an optical material is "large" or "small", it means that it is sufficient that it has a relative magnitude rather than an absolute value. The larger the difference in refractive index, the better, but if the refractive index of the one with the smaller absolute value is too low, the function of the lenticular lens itself will deteriorate, so a material with the highest possible refractive index should be used as the material with the larger absolute value. It is preferable to select a combination that provides a large difference. This will be explained below with reference to the drawings. As shown in Fig. 1, a conventional black stripe type lenticular screen 1A has a lenticular lens 2A formed in one piece from a transparent synthetic resin material.
Since black stripes 3 are provided in the above, in order to give the light beam in the direction of the arrow an appropriate diffusion angle and pass between the black stripes,
The thickness is determined by the lens pitch and the refractive index of the material, and Ta is the limit. According to the present invention, as shown in FIG. 2, the lenticular screen 1B includes a base material 4 made of a material with a higher refractive index laminated on the back surface of a lenticular lens 2B, and a base material 4 made of a material having a higher refractive index. A black stripe 3 is provided on the top. When the light enters the base material 4 from the lenticular lens 2B, it is refracted and transmitted through the screen along the path indicated by the arrow. Therefore, the screen thickness can be increased to Tb even though the diffusion angle remains the same. This principle can be easily understood by referring to FIG. In Fig. 3, among the parallel rays incident perpendicularly on the lenticular lens, the one at the position of the arrow travels at an angle of θ ₁ , and if the screen is made of a single material with a refractive index of n ₁ , then There is a relationship n ₁ sin θ ₁ = sin θ ₃ between the diffusion angles θ ₃ and θ ₁ when the light passes through this. If there is a base material with a refractive index n ₂ (n ₂ > n ₁ ), the slope θ ₂ when entering the base material is n ₁ sin θ ₁ = n ₂ sin θ ₂ , and the slope when leaving the base material is Since θ ₄ is n ₂ sin θ ₂ = sin θ ₄ , sin θ ₄ = sin θ ₃ after all. The material of the lenticular screen of the present invention is
A transparent thermoplastic resin is also suitable, and various materials can be used, but typical materials are as shown below, and they may be selected and combined in consideration of the refractive index values listed below.

[Table] Matters related to screen design, especially the thickness of the lenticular lens layer and the thickness of the base material.
It may be determined based on the above relationship. A specific example is as follows. (Conventional product) Lenticular lens layer only...PMMA thickness 1890μ (Invention product) Lenticular lens layer...PMMA thickness 20μ Base material layer...PS thickness 2010μ Total thickness 2030μ Two-layer laminate , heat fusion may be used, or an appropriate adhesive may be used. Techniques for providing black stripes are known. The screen of the present invention, as in the example above, can be increased in thickness by 7.4% or more compared to the conventional screen. As a result, the screen can have sufficient strength. The optical performance is
Even with a two-layer structure, there is virtually no effect. Furthermore, in the above example, the combination is thin PMMA and thick PS, and since the inexpensive PS is the main component, the material cost can be reduced first. In molding, commercially available molds with a thickness of about 20 μm are used.
PMMA film is made into a lenticular lens by roll embossing method, and at the same time, the base material PS
Since it can be integrated with the top by heat fusion, processing costs are also low. In this way, the object of the invention described above can be achieved.

[Brief explanation of drawings]

Figure 1 shows the structure and operation of a conventional black stripe type lenticular screen.
It is an enlarged sectional view. FIG. 2 is a view similar to FIG. 1 showing a lenticular screen according to the invention. FIG. 3 is a diagram illustrating the principle of making the screen thicker without changing the diffusion angle of transmitted light according to the present invention. 1A... Conventional lenticular screen, 1
B... Lenticular screen of the present invention, 2
A, 2B... Lenticular lens, 3... Black stripe, 4... Base material.

Claims (1)

[Scope of Claims] 1. A transmissive screen using a lenticular lens, which is a black stripe type lenticular screen in which a band that absorbs external light is provided on a portion of the back surface that does not transmit image light. consists of at least two layers, an optical material with a small refractive index is used for the layer on the lenticular lens surface, and an optical material with a large refractive index is used for the base layer on the back surface. A screen characterized in that the thickness of the layer and the thickness of the base material layer are selected according to the lens pitch and the combination of the refractive indexes of the optical materials of both layers, so that the focal point of the image light almost coincides with the exit surface. . 2. As optical materials, cellulose triacetate, cellulose tributyrate, cellulose acetate butyrate, polymethyl methacrylate,
The screen according to claim 1, which uses a combination of two types of synthetic resins selected from nitrocellulose, polyvinyl chloride, polycarbonate, polystyrene, and polyethylene terephthalate based on their refractive index.