JPS62121437A - Transmission type screen - Google Patents

Abstract

PURPOSE:To obtain a transmission type screen which has a high blackening rate and excellent visual field characteristics by providing a total reflecting curved surface which is outward convex on both sides of lens units constituting a lenticular lens and also providing two projection curved surfaces between total reflecting curved surfaces. CONSTITUTION:This transmission type screen has the lenticular lens formed on its observation side, outward convex total reflecting curved surfaces 2 and 2 having a radius r1 of curvature are provided on both sides of lens units 1 constituting the lenticular lens, and two projection curved surfaces 3 and 3 with a radius r2 of curvature are formed between total reflecting curved surfaces. When those four curved surfaces are regarded as a minimum lens unit, the ratio P1:r1 of the pitch P1 and radius r1 of curvature is set to 1:1-1:4.6 and the ratio r2:P1 of the pitch P1 and radius r2 of curvature is set to 1:2.4-1:3.0. Consequently, the transmission type screen which has no large depression of the quantity of light when the visual field angle is almost 20 deg. is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmissive screen with a lenticular lens used as a screen for a video globulogram television or the like.

[Conventional technology]

Rear projection screens can be used for video projectors,
It is used as a projection surface for microfilm readers or computer display screens, and various studies have been conducted on its light transmittance, such as increasing its viewing angle. As one means of achieving this objective, it has traditionally been the practice to use a lenticular lens, in which a large number of minute cylindrical lenses are continuously formed, either alone or in combination with other lenses or a diffuser plate. ing.

Further, the present inventors have disclosed a lenticular lens having a shape as shown in FIG. 10 in Japanese Patent Application Laid-open No. 145933/1983 in order to widen the viewing angle of the lenticular lens. In this lenticular lens, the lens unit has total reflection surfaces 101, 101 on both inclined surfaces, and a plurality of curved surface portions 102, 102 are formed between the inclined surfaces on both sides, so that light enters from the projection side Reflective surface 101, 1
It is designed so that the light reflected at 01 passes through part of the curved portions 102 and 102.

FIG. 11 is a diagram showing the traveling direction of transmitted light when light from (person)-(E)-1 is incident on the lenticular lens unit 100 from the projection side X.

In the figure, the light incident between (C) and (D) is emitted from the curved surface 102 as if it were a general circular lenticular lens, and the light enters the range (C') where the viewing angle is small.
-(D'). Further, the light incident between (A) and (B) is totally reflected by the total reflection surface 101, and then exits from the curved surface 102 and reaches the wide area between (person) and (B). Note that the light incident between (B) and (C) and between (C) and (E) similarly spreads from the center line CC'') to the area on the left side, but is omitted from the diagram for the sake of simplicity.

FIG. 12 shows the viewing angle characteristics of the lenticular lens shown in FIG. 11. In the figure, the horizontal axis represents the viewing angle, and the vertical axis represents the brightness ratio.

Furthermore, the viewing angle characteristics of a conventional cylindrical lenticular lens are shown in FIG. As can be seen by comparing FIGS. 12 and 13, the lenticular lens shown in FIG. 12 causes less reduction in brightness than the conventional cylindrical lens even when the viewing angle becomes large.

Furthermore, when an external light absorption layer is formed on the total reflection surface of the lenticular lens shown in FIG.
2, 102) is narrow, the ratio of the external light absorbing layer to the entire surface of the lenticular lens (so-called blackening ratio) is increased, which has the advantage of providing a screen that is easy to see even in bright places.

[Problem that the invention seeks to solve]

However, when using the lenticular lens 100 alone as shown in FIG. 10, there is a drawback that a large gap in the scene appears near the viewing angle 20 as shown in FIG. 12.

This is between (C') and (D') and (A
Angle 10 where light does not reach the valley between ') - (B')
The reason is that 3 is wide. Therefore, there is a problem in that the brightness of the screen decreases at angles around this range, and strong color changes occur.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a transmission type IJ screen that does not have a large gap in the amount of light even at a viewing angle of about 2o0.

The object as described above is a transmission type screen in which a lenticular lens is formed at least on the observation side, and each lens unit constituting the lenticular lens is provided with an outwardly convex total reflection curved surface with a radius of curvature rl on both sides. and between the total reflection curved surfaces are two exit curved surfaces each having a radius of curvature r2), and when these four curved surfaces are considered as the minimum lens unit, the pitch P and the ratio of the radius of curvature r1, Pl:r is within the range of 1:3.4 to 1:4.6, and the ratio of pitch P to radius of curvature r2*r2:P
, is within the range of 1:2.4 to 1:3.0.

〔Example〕

The present invention will be described below with reference to drawings of embodiments.

FIG. 81 is a perspective view showing an embodiment of the transmission type screen of the present invention. FIG. 2 is an enlarged view of the lens unit of the lenticular lens. In FIG. 2, 1 indicates a lens unit, and this lens unit 10 is provided with outwardly convex total reflection curved surfaces 2, 2 with a radius of curvature rl on both sides, and the total reflection curved surfaces 2, 2. In between, two exit curved surfaces 3, 3 each having a radius of curvature r2 are provided.

The light transmission characteristics of the lens unit 1 in the transmission screen of the present invention will be described later, but the example shown in FIG. 1 is a lenticular lens formed of only the viewing side YK and the lens unit 1 shown in FIG. 2. The present invention is a transmission screen in which a lenticinary lens made of the lens unit 1 described above is formed at least on the observation side Y, but it is more effective if an XK souffler lens is formed on the projection side. This embodiment is shown in FIG. 3, which is a sectional view of a transmission screen in which a 7-Renel lens 4 is formed on the projection side X of the transmission screen in FIG. The Fresnel lens 4 in this case is generally a Sarkiehler Fresnel lens, and its focal length depends on the purpose of use of the screen, but for example, in the case of a transmissive screen for a large video projector, it is generally f = 1. .0 to 1.2 is most common.

Further, as one means for improving the contrast of the transmission screen of the present invention, there is a method of forming an external light absorbing layer 5 on the total reflection curved surfaces 2, 2, as shown in FIG. -,
In this case, in order to prevent absorption loss in the external light absorbing layer 5, a reflective layer 6 is formed in advance.

This reflective layer 6 is made of a material with a lower refractive index than the lens unit 1. In this way, the total reflection curved surfaces 2, 2, which do not have the function of emitting light to the observation side Y, can be effectively used as surfaces that absorb external light, and the contrast of the screen can be improved.

Now, as described above, the transmission screen of the present invention has a lens unit 1 having total reflection curved surfaces 2, 2 on both sides and an emission curved surface 3, 3 between the total reflection curved surfaces 2.2. However, the light transmittance of this lens unit 1 will be explained below based on FIGS. 5 and 6.

FIG. 5 shows one lens unit 1, where 2°2 is a total reflection curved surface and 3.3 is an exit curved surface. This lens unit 1
The shape of is determined by the overall pitch P, the horizontal distance tb from the end a of the total reflection curved surface 2 to the apex, and the radius of curvature r of the total reflection curved surface 2.
4. Determine by giving the radius of curvature r2 of the exit curved surface 30, the distance t1 from the end a of the total reflection curved surface 2 to the center of curvature 01 of the total reflection curved surface 2, and the distance t2 from the end a to the center of curvature 02 of the exit curved surface 3. be able to.

Here, it is desirable that the angle θ at which the total reflection curved surface 2 with the radius of curvature r intersects the line segment ms is sufficiently larger than the angle at which parallel light is totally reflected, that is, the critical angle. In other words, θ〉−but n
is the refractive index, for example, when the refractive index is n=1.4 like acrylic resin.
In the case of 9, it is desirable that θ is 65 to 8σ. This is because, in order to make the total reflectance as large as possible, it is preferably 65 or more, and conversely, if it is too close to 90, it will be difficult to manufacture the mold.

Furthermore, the ratio between the total reflection curved surface 2 and the exit curved surface 3 in the lens unit 1 (determined by determining tb in Fig. 5) cannot be set freely, but due to the characteristics of the transmission screen, it is within the range of It is preferable that there be.

Next, FIG. 6 is a diagram showing the traveling direction of transmitted light when the elements (A) to (E) are incident on the lens unit 1 from the projection side X. As shown in the same figure, K (person) - (B
) Since the total reflection curved surface 2 has a curvature r1, the angle 7 at which the light incident between the two ends can be made smaller than the angle 103 in FIG. 11 described in the prior art section. This means that it is possible to prevent the brightness of the screen from decreasing in this angle range.
It is possible to provide a transmissive screen that exhibits better viewing characteristics than the screen disclosed in No. 145933. However, even though it is said that the total reflection curved surface is given a curvature r1, it does not mean that any curvature is acceptable.The present inventors have discovered that there are certain conditions to reduce the angle 7 at which the light does not reach. I found it. The conditions are as follows.
, and (■) must both be satisfied.

■ The ratio of the pitch P of the lens unit and the radius of curvature r of the total reflection curved surface 2, P, :rl is 1: 3.4 to 1: 4.6.
be within the range of

■ Pitch P1 of lens unit and radius of curvature r of exit curved surface 3
The ratio e 72 :Pl of 2 is within the range of 1:2.4 to 1:3.0.

Here, the condition of We conducted an experiment to find out what range the ratio of radius r1 to pitch P should be for a screen that can actually be used.
It has been established.

The experiment was conducted as shown in FIG.
The figure shows the case of 1:2.5. ) P, and the radius of curvature r, P: We created screens with different values of rl, and investigated the viewing angle and brightness distribution of the screens.

As can be seen from FIG. 7, when the value of P is 1, the value of r is 3.4, 3.3, etc. As the value is decreased, a valley appears in the light amount around 20 to 25.

Conversely, the value of r is 4.5, 4.7.・・・・・・・・・・・・
As the value is increased, the amount of light at 25 increases, so the valley near 20' is emphasized. Therefore, Pl:
It was determined that rl was between 1:3.4 and 1:4.6, which did not cause any trouble in observation. In addition, in the same figure, 0° to 1
The reason why the brightness at 5° does not change is because the shape of the exit curved surface 3 is constant in FIG. 6, so the transmitted light CC)-(D) does not change.

Next, the condition (■) is based on an experiment to find out what ratio of the pitch P and the radius of curvature r2 of the exit curved surface should be set to produce a screen with good characteristics when P:,1 is constant. It is determined by the following. FIG. 8 shows an example of the experimental results.
3, the relationship between viewing angle and brightness was investigated by changing the ratio of r2 and Pl.

As can be seen from Figure 8, when the value of r2 is set to 1 and the value of P is decreased, the light intensity decreases significantly at 20 degrees. Although not shown, the amount of light is O. Even at 2.3, there is a large gap in the amount of light, which is not practical. Although there is a valley in the light amount at 2.4, it is at a level that does not pose a problem for observation. Conversely, as the value of P increases, the valley of light intensity near 2♂ becomes smaller, but O
The overall light amount decreases around 20 to 20, and a valley in the light amount appears around 15'. The upper limit is 3.0. Therefore, r2:Pl is 1:2.4 to 1:3. It was determined that there was no problem in observation between 0 and 0.

In addition, in the above description, in the case of FIG. 7, r2:P, = 1
:2.5, in the case of Figure 8, Pl : rl ” 1 :
4.3 was selected for explanation purposes as it best represents its characteristics, and in actual experiments, the conditions described above ■
,■ In determining , it goes without saying that we looked for improvements in other ratios. In this search, several points were found where the characteristics of the screen were improved by the combination of the Pl:rl ratio and the r2:Pl ratio, and these points were also within the range of the above-mentioned conditions (1) and (2).

Acrylic resin is most suitable as the base material for the transmission screen of the present invention, because acrylic resin is particularly excellent in terms of optical properties and moldability. However, instead of this, vinyl chloride resin, eyes? Recarbonate resin, olefin resin, styrene resin, etc. can also be used, and when these synthetic resin materials are used, the transmission screen according to the present invention can be manufactured by extrusion molding, hot pressing, or injection molding.

Further, in order to further improve the light diffusing properties of the transmission screen according to the present invention, it is preferable to provide a light diffusing means. This light diffusing means is made of synthetic resin constituting the medium, such as acrylic resin. CaCO3゜Al205,
TiO2t BaSO4 + ZnO + glass fine powder, or one or more types of diffusive substances that do not undergo melting or chemical change in a liquid synthetic resin medium, such as an organic diffusing agent, are uniformly mixed and dispersed in the medium, or It is preferable to form a layer containing a diffusing substance.

It is also effective to form a fine matte surface on the projection side X plane and/or the observation side Y plane. By taking such means for imparting light diffusivity, the horizontal and vertical diffusivity of the screen can be compensated for and the evenness can be improved.

Specific examples will be described below.

(Example) Acrylic resin with a refractive index of 1.49 was used, and 5LO2 was mixed as a light diffusing agent in the production of the resin plate, and the thickness was 3 mm.
A rill resin board was prepared. This acrylic resin plate was connected to a mold on which a 7-Renel-raised surface with focal length r=i, i was formed, and a third
A transmission type screen as shown in FIG. 5 was produced by heat pressing between a mold such as the lens unit shown in the figure at a temperature of 180° C. and a pressure of 40° C. In addition, in Fig. 5, the angle θ is 76, and Pl is 0.69.
Ryu, rl is 3, Om Atsushi, r2 is 0.28 all,,t
b is 0.13! ! tK and tl are 2. g 1 mgm, t
2 is 0.1351”I's P:rl is 1:4.
3. Designed with r2:Pl ratio of 1:2.5.

When the transmission characteristics of the transmission screen thus obtained were evaluated, the results shown in FIG. 9 were obtained. As is clear from these results, we believe that we have been able to provide a transmissive screen with much better front viewing characteristics than the conventional transmissive screen shown in Figure 12.

〔Effect of the invention〕

As described above, according to the transmission screen of the present invention, it was possible to provide a transmission screen with a high blacking rate and good viewing characteristics.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a transmission screen of the present invention, and FIG. 2 is an enlarged view of a lenticular lens unit of the transmission screen. FIG. 3 is a sectional view showing an embodiment in which a Fresnel lens is formed on the screen of FIG. 1, and FIG. 4 is an enlarged view showing an embodiment in which an external light absorption layer is provided. FIG. 5 is a diagram showing the configuration and main meter for determining the lenticular lens unit, and FIG. 6 is a diagram showing the transmitted light characteristics of the lenticular lens unit of the present transmission screen. FIGS. 7 and 8 are graphs showing the relationship between viewing angle and brightness ratio for each lenticular lens, and FIG. 9 is a graph showing the relationship between viewing angle and brightness ratio of the present transmissive screen in a specific example. . FIG. 10 is an enlarged view showing a conventional lenticular lens unit, and FIG. 11 is a diagram showing its transmitted light characteristics. FIG. 12 is a graph showing the relationship between the viewing angle and brightness ratio of the lenticular lens unit shown in FIG. 10, and FIG. 13 is a graph showing the relationship between the viewing angle and brightness ratio of the conventional cylindrical lenticular lens unit. 1: Shi/Chiquilar lens unit, 2: Total internal reflection curved surface, 3:
Output curved surface, 4: Fresnel lens, 5: External light absorption layer, 6:
Reflective layer, 7: An angle that is unlikely to be reached. Agent Patent Attorney Yamashita 1 Figure 1 Figure 2 Figure 4 tY) (×) Figure 7 R No Kado (dog) Figure 8 Rfff14 (deq) Kazu Shuno (de9) 12th introduction! Nokura (de9)

Claims (5)

[Claims] (1) It is a transmission screen with a lenticular lens formed at least on the observation side, and the radius of curvature is r_1 on both sides of the lens unit that makes up the lenticular lens.
It has an outward convex total reflection curved surface, and between the total reflection curved surfaces there are two exit curved surfaces each having a radius of curvature r_2, and when these four curved surfaces are taken as the minimum lens unit, The ratio of the pitch P_1 and the radius of curvature r_1, P
_1:r_1 is within the range of 1:3.4 to 1:4.6, and the ratio of pitch P_1 to radius of curvature r_2, r_2:P
A transmission screen characterized in that _1 is within the range of 1:2.4 to 1:3.0. (2) The transmission screen according to claim 1, further comprising a light diffusing means. (3) The transmission screen according to claims 1 and 2, wherein an external light absorbing layer is formed on the total reflection curved surface of the lenticular lens. (4) The transmission screen according to claim 3, characterized in that a low refractive material layer is interposed on the total reflection curved surface of the lenticular lens. (5) The transmission screen according to claims 1, 2, 3, and 4, characterized in that a Fresnel lens is formed on the projection side.