JPH04143743A - Transmission type screen - Google Patents

Abstract

PURPOSE:To control the distribution of a scattered light beam by composing part of a lenticular lens unit of a plane and using a light diffusing resin plate as a substrate. CONSTITUTION:An example of the lenticular lens unit is shown by total reflecting surfaces 1 of both flank parts, a center curved surface part 2, and plane parts 3 connecting the center curved surface and total reflecting surfaces. The substrate of the screen which form the lenticular lens is the light diffusing resin plate which has diffusing performance so that a light beam which is made incident directly on the plane part 3 is diffused properly; and the necessary light diffusing performance varies with the rate of the plane parts 3 to the whole lenticular lens unit and is selected properly according to the characteristics of the optical system of a projection television in use and the combination. Namely, when a substrate with a 8 deg. half-value angle is used, the substrate becomes a transmission type screen with uniform diffusing performance even unless the intermediate parts 3 are not convex, but plane. Consequently, the distribution of the scattered light beam is controllable and the manufacture is facilitated; and high resolution and a large field angle are obtained and an irregularity in brightness is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmissive screen used in projection televisions and video projectors.

[Conventional technology]

Transmissive screens using lenticular lenses are widely used for projection televisions and the like. One of the important performance requirements for this projection television screen is a large viewing angle.
Various techniques are known, such as:

On the other hand, recently, new types of projection televisions are being developed, and the performance required of transmissive screens is not only to have a large viewing angle, but also to increase resolution by reducing the pitch of the lenticular lenses.

For example, in the case of 40 WL, 0.5 +
There is a need for a lenticular lens with a pitch of less than am. In addition, in projection type LCD televisions, as disclosed in Japanese Patent Application Laid-open No. 62-236282, in order to prevent moiré patterns caused by interference of vertical lines of the lenticular lens of a transmissive screen, the pitch must be made as small as possible. It is desired to do.

On the other hand, with conventional lenticular lenses for transmissive screens designed to increase the viewing angle, it has been difficult to reduce the pitch of the lenticular lenses, mainly due to manufacturing issues.

For example, in the case of the aforementioned Japanese Patent Publication No. 61-28980,
Since the surface from which at least a portion of the light rays totally reflected by the total reflection surfaces at both ends exits is a convex surface, as the pitch is made smaller, it becomes difficult to create the surface shape of this small convex portion as designed. Become. Also, JP-A-58-13462
In the case of Publication No. 7, the structure uses a lenticular lens on the light source side to focus the light on the observation side surface, so if the pitch is made smaller, the plate thickness must also be made smaller, so there are manufacturing limitations and the rigidity is insufficient. There was a problem that it was difficult to handle because there was no such thing.

Therefore, the present inventors created a lenticular lens in a specific shape consisting of a total reflection surface consisting of a convex surface and a flat surface at the center, and a flat section connecting the convex surface and the total reflection surface, and the substrate at a specific half-value angle. We discovered that by using a light-diffusing resin plate with a light-diffusing resin plate, it is possible to manufacture a transmission-type screen with high resolution and a large viewing angle, even if the pitch width of the lens unit is narrow, and we proposed a high-resolution transparent A-type screen ( Patent application Hei 1-336
No. 32), this invention provides a transmission type screen in which lenticular lenses extending vertically to the observation side and having a pitch of 0.5o+m or less are formed, in which the lenticular lens units include at least flat parts at both ends, a curved part in the center, and a central curved part. It consists of an intermediate plane part between the flat parts at both ends and the curved part at the center, and most of the light rays incident on the flat parts at both ends are totally reflected and emitted from the intermediate flat part. Most of the light rays directly incident on the curved surface are designed to be directly emitted, and the substrate has a half-value angle of 6
The present invention relates to a transmission type screen characterized by being a light-diffusing resin plate with a hardness of at least 100°C.

[Problem to be solved by the invention]

The invention described above makes it possible to manufacture a transmission screen with a narrow pitch width and a large viewing angle, but since both the total reflection surface and the surface through which reflected light rays are transmitted are flat, the distribution of scattered light rays can be controlled. There were some difficulties in doing so.

[Means to solve the problem]

The present invention has been made in view of this situation.

That is, the present invention provides a transmission screen in which a large number of vertically extending lenticular lenses are formed on the viewing side, in which each lenticular lens unit has at least a convex surface in the center, a total reflection surface on both sides consisting of a curved surface, and the convex surface. The light rays totally reflected by the total reflection surface are condensed on the flat surface and transmitted through the flat surface, and the light rays directly incident on the flat surface are connected to the flat surface. The present invention provides a transmission type screen which is designed to transmit light, and is characterized in that the substrate of the screen forming the lenticular lens is a light-diffusing resin plate.

The present invention will be explained below with reference to the drawings.

An example of the lenticular lens unit of the transmission screen of the present invention is shown in FIG. 1, which is one embodiment of the present invention and is not intended to limit the present invention.

In FIG. 1, 1 is a total reflection surface on both side surfaces, 2 is a central curved surface, and 3 is a flat surface connecting the central curved surface and the total reflection surface.

In this lenticular lens unit, the incident light rays travel with a certain distribution due to the diffusion effect of the substrate, but for convenience here, it is assumed that parallel rays are incident. The paths of light rays can be broadly classified into ■~■ listed below.

■ Light rays incident on the total reflection surfaces 1 on both sides (Figure 2 (a)
)) is reflected on the total reflection surface l and then focused on the flat part 3,
Most of the light rays are emitted from the flat section 3. In other words, the diffusion of the substrate having a specific half-value angle of the present invention between the incident light beam from the incident surface to the total reflection surfaces 1 at both ends, and between the total reflection surfaces 1 and the flat surface 3 at both side surfaces. The light is diffused by the effect, and is further diffused widely by the synergistic effect of the diffusion by the curved surface forming the total reflection surface 1, and is emitted to the outside from the flat part 3.

■ Light rays incident on the central curved surface 2 ((b) in Figure 2)
is widely diffused due to the synergistic effect of the shape of the curved surface and the diffusion effect of the substrate itself, and is emitted directly to the outside.

■ Light rays directly incident on the flat part 3 ((C) in Figure 2)
) is directly emitted to the outside with appropriate diffusivity due to the diffusion effect of the substrate.

The diffusion of the light rays mentioned in (2) above can be controlled over a wide range by the shape of the curved surface of the total reflection surface 1. Furthermore, since the total reflection surface 1 is a curved surface that condenses light rays onto the flat portion 3, the flat portion 3 can be made smaller than when the total reflection surface 1 is a flat surface. Of course, the flat portion 3 may be made larger. In other words, the ratio of the flat portion 3 to the lens unit can be set within a wide range, so the ratio of the rays in 1. can. In this way, it becomes easier to control the distribution of scattered light rays.

The curved surface of the total reflection surface 1 may be any curved surface as long as it focuses the reflected light in the direction of the flat part 3, but it is preferably a curved surface that concentrates the reflected light at one point. An example of such a curved surface is a parabola represented by y=-ax2 (a is a positive real number). In the case of the above parabola, the focus of the reflected light is (0, -1/4a). This focus does not necessarily have to be on the plane part 3, and as shown in (a) in FIG. It can be on the outside or sometimes on the inside.

Figure 4 shows the brightness distribution diagram when a lens unit with a parabolic total reflection surface is used (Example 1), and Figure 6 shows the brightness distribution diagram when a lens unit with a flat total reflection surface is used (Comparative Example 2). If the total reflection surface is a curved surface, in order to obtain a wide viewing angle, the total reflection surface 1 should be made relatively large so that more light rays (a in Figure 2) that have been totally reflected can be reflected. FIG. 4 is a brightness distribution diagram when the lens unit thus designed is used. - If the total reflection surface is a flat surface, the total reflection surface and the flat portion 3 must be made large at the same time in order to obtain a wide viewing angle. However, if the flat portion 3 is too large for the lenticular lens unit, , a ray of light that directly enters the plane part 3 (C in Fig. 2)
increases, resulting in uneven brightness as shown in FIG.

Japanese Patent Publication No. 61-28980 uses the same technology as the present invention, but the major difference from the present invention is the surface through which the totally reflected light rays pass (corresponding to the flat part 3 in the present invention).
is a point that is a curved surface.

As the pitch of the lens unit becomes smaller, the curvature of the above-mentioned curved surface increases, making it extremely difficult to create.In the present invention, since this is a flat surface, it is easy to create.

The total reflection surface 3 is a curved surface, but the curvature is small compared to the curved surface disclosed in Japanese Patent Publication No. 61-28980 from which at least a part of the totally reflected light rays exit, so it can be manufactured even when the pitch of the lens unit is small. is easy.

In the present invention, the external light absorbing layer 4 may be provided on at least a part of the total reflection surface 1 on both side surfaces, as the case may be, so that the external light can be mainly absorbed and the contrast of the image can be improved. .

In the present invention, since a part of the lens unit constituting the lenticular lens is a flat part, it can be easily designed and manufactured even if the pitch width is narrowed, and the substrate can have light diffusivity at a specific half-value angle. Combined with the selection of resin plates, an excellent transmission screen can be manufactured.

In the present invention, as shown in FIG.
As shown in the figure, a smaller flat portion 5 may be provided between the total reflection surface 1 and the flat portion 3 on both side surfaces.

Further, in the present invention, the flat portion 3 or the minute flat portion 5 may be subjected to surface roughening treatment to prevent reflection of external light.

In the present invention, the substrate of the screen that forms the lenticular lens must be a light-diffusing resin plate that has a diffusion performance that appropriately diffuses the light rays directly incident on the flat surface part 3. If the light is not diffused sufficiently, it will be concentrated at a certain angle, resulting in uneven brightness depending on the angle.The required light diffusion performance is
It changes depending on the proportion of the flat part 3 in the entire lenticular lens unit, and is appropriately selected in combination with the characteristics of the optical system of the projection television used.

Figure 4 shows a case where a substrate with a half-value angle of 8° is used (Example 1)
and Fig. 5 show the luminance distribution when using a substrate with a half-value angle of 4゛ (Comparative Example 1). This half-value angle is the angle at which the brightness is half of the maximum brightness. in the case of(
In Example 1), even if the intermediate part 3 is a flat plate rather than a convex surface as in the conventional example, the substrate becomes a transmission screen with almost uniform diffusivity, but in the case of Fig. 5 (Comparative Example 1) Although the viewing angle is large, a drop in brightness (brightness unevenness) occurs near the viewing angle of 30', making it unsuitable for use as a transmissive screen.

In the present invention, there are no particular restrictions on the transparent resin used as the substrate component of the transmission screen, and examples thereof include acrylic resin, styrene resin, polycarbonate, vinyl chloride resin, etc., and transparent or translucent thermoplastic resins are used. can.

Among these, acrylic resins are preferred in terms of surface scratch resistance, weather resistance, transparency, and the like.

There is no particular limit to the thickness of the transmission screen substrate in the present invention, but from the viewpoint of rigidity and ease of handling, 1
．． 5 to 4 mm is desirable.

In the present invention, there are no particular restrictions on the type and amount of light diffusing agent to be blended into the transparent resin. For example, examples of inorganic light diffusing agents include calcium carbonate, barium sulfate, titanium oxide, silicon dioxide, and Calcium chloride,
Examples of organic light diffusing agents include styrene resin, methyl methacrylate/acrylic ester/aromatics, and crosslinked copolymer particles containing aromatic and nil monomers as main components. Can be used in combination. Among these, preferred are crosslinked copolymer particles containing methyl methacrylate/acrylic acid ester/aromatic vinyl monomer as main components, calcium carbonate, quartz powder, barium sulfate, glass beads, etc. with an average particle size of 20 to 100 microns.

In the present invention, there are no particular restrictions on the manufacturing method of the lenticular plate for a transmission screen, and ordinary injection molding,
Compression molding method, extrusion molding method, casting method, continuous casting method, etc. can all be used.

There are no particular limitations on the material and formation method of the external light absorption layer in the present invention as long as it has the ability to absorb external light.
As a way to increase the total reflectance, for example, Japanese Patent Application No. 63-2
No. 23464, a method of creating an air layer between the base material using a paint containing a black dye/pigment and specific spherical particles, and a method of creating a black color using a transparent material whose refractive index is smaller than that of the base material as the main component. There are methods that use a mixture of dyes and black pigments, and methods that form a layer between the external light absorbing layer and the base material, the main component of which is a transparent substance with a refractive index lower than that of the base material, and any of these methods can be used.

When the transmission screen of the present invention is combined with a Fresnel lens, a transmission screen with even higher performance can be obtained. In this case, a Fresnel lens may be provided on the side surface of the light source of the transmission plate screen of the present invention, or a Fresnel lens may be provided on another plate-shaped body and combined with the transmission type screen of the present invention.

〔Example〕

The present invention will be explained below using Example 1, but this does not limit the present invention.

(1) Production of light diffusing agent (organic crosslinked polymer particles): The following components were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen gas inlet, etc.

■Methyl methacrylate 55 parts by weight ■Butyl acrylate 20 parts by weight ■Styrene
25 parts by weight ■ Allyl methacrylate 1.5 parts by weight ■ t-dodecyl mercaptan 063 parts by weight ■ Asiazoisobutylnitrile o
, smt part ■ Polyvinyl alcohol 3.0ff
iffi part ■ Water 200 parts by weight After the inside of the container was sufficiently replaced with nitrogen gas, the mixture of the above components was heated to 70° C. with sufficient stirring to proceed with polymerization in nitrogen gas. After 4 hours, the temperature was raised to 90℃, and
After the polymerization was completed by holding at 0° C. for 1 hour, the beads were dehydrated, washed with water, and dried to obtain granular beads. The obtained beads were sieved to obtain organic crosslinked polymer particles with an average particle size of about 25 μm.

(2) Manufacturing of substrate: 3% by weight of the light diffusing agent obtained in (1) above was added to Delpet 70H (methacrylic resin manufactured by Asahi Kasei Industries, Ltd.), and after heating and kneading with an extruder (resin temperature 250°C) , the molten resin coming out of the die is passed between rolls and cooled to form a 610x46
A substrate for an example of 0X3i+m was obtained.

In addition, a substrate for a comparative example in which the proportion of the light diffusing agent was 1.5% by weight was obtained in the same manner.

(3) Measurement of the half-value angle of the substrate: Parallel light was incident on the substrate obtained in (2) above using a collimator, and the brightness distribution was measured using a brightness meter (Minoshita type nu-1/3°P). .

From the measurement results, the angle at which the brightness at the center is halved (half-value angle) was determined. The half-value angle of the substrates for Example 1 and Comparative Example 2 was 8°, and the half-value angle of the substrate for Comparative Example 1 was 4°.

(4) Molding of lenticular lens and Fresnel lens: Examples and Comparative Examples 1 and 2 manufactured in (2) above, respectively.
Place the substrate between the lenticular lens mold and Fresnel lens mold shown below, and press using a hot press at a molding temperature of 160°, a molding time of 10 minutes, and a molding pressure of 30 kg.
/ cm 2 and then cooled with water for 10 minutes to obtain a molded product.

[亙j] Substrate half-value angle: 8° Lenticular lens unit: Fig. 7 Pitch 0.4 mm Fresnel lens: Pitch 0.18 mm Focal length glloomm (In Fig. 7, the central curved part is aspherical (x, y) are coordinates indicating the shape of the lens unit.) Comparative Example 1 Substrate half-value angle = 4° Lenticular lens unit: Fig. 7 Pitch 0.4 rnra Fresnel lens: Pitch 0.25 ram
Focal length: 1000 mm Ratio: Substrate half-power angle = 8° Lenticular lens unit: Figure 8 Pitch: 0.4 mm Fresnel lens: Pitch: 0.25 mm Focal length: 11 fltl (looa + m (In Figure 8, center The curved surface part has an aspherical shape, and (X, y) are coordinates that indicate the shape of each lens.) (5) Evaluation and results A parallel beam of light was applied, and the brightness distribution was measured using a brightness meter (Minoshita type nt-1/3°P).

The results are shown in Figure 4 (Example 1) and Figure 5 (Comparative Example 1).
and FIG. 6 (Comparative Example 2).

In addition, the projector is TWIN CABIN 5UPER (manufactured by Cabin Industries, lamp: 300W; lens F3.
Images of the slides were projected onto the transmission screens of Example 1 and Comparative Example using a 50ma+), and the images formed on the screens were visually observed from various angles.

As a result, the transmission screen of Example 1 had no unevenness in brightness, and the details of the image were clearly visible.

However, although the transmission screen of Comparative Example 1 could clearly see the details of the image, it was unsuitable because it had uneven brightness. Comparative Example 2 was designed using the technology disclosed in Japanese Patent Application No. 1-33632 to have a viewing angle comparable to that of Example 1, but it was difficult to control the distribution of scattered light rays. Therefore, uneven brightness remained, which was still unsuitable.

〔Effect of the invention〕

As described above, in the present invention, a part of the lenticular lens unit is made of a flat surface, and a light-diffusing resin plate is used as the substrate, so that it is easy to design and manufacture the lenticular lens unit with a narrow pitch. At the same time, a transmissive screen with high resolution, a wide viewing angle, and no uneven brightness can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of a lenticular lens unit of a transmission screen of the present invention. Figure 2 is a schematic diagram showing the diffusion effect of parallel light rays incident on the lenticular lens unit of Figure 1, of which Figure 2(a) shows the case where the light rays are incident on the total reflection surfaces on both sides. ; Figure 2(b) shows the case where the light ray is incident on the central curved surface; Figure 2(C) shows the case where the light ray is incident on the flat part connecting the total reflection surface and the central curved surface. It shows. FIG. 3 is a schematic diagram showing another embodiment of the transmission screen of the present invention, in which a minute plane part is provided between the total reflection surface part and the plane part at both ends of the lenticular lens unit. 4 to 6 are graphs showing the luminance distribution of the transmissive screen of Example 1 and Comparative Example 1.2, respectively. FIG. 7 is an actual measurement of the unit dimensions of the lenticular lens of the present invention molded according to Example 1. It is a schematic diagram showing a value. FIG. 8 is a schematic diagram showing actual measured values of unit dimensions of a lenticular lens of the present invention molded according to Comparative Example 2. 9 and 10 are schematic diagrams showing a lenticular lens unit of a conventional projection screen. Total reflection surface area on both sides: Curved surface area in the center: Flat area connecting the total reflection surface and the central curved area: External light absorption layer: Minute flat area

Claims (1)

[Claims] In a transmission screen in which a large number of vertically extending lenticular lenses are formed on the observation side, each lenticular lens unit has at least a convex surface in the center, a total reflection surface on both sides consisting of a curved surface, and a combination of the convex surface and the total reflection surface. , so that the light rays totally reflected by the total reflection surface are focused on the plane part and transmitted through the plane part, and the light rays directly incident on the plane part are transmitted through the plane part. 1. A transmission type screen which is designed in such a way that the substrate of the screen forming a lenticular lens is a light-diffusing resin plate.