JPH0658495B2 - Lens sheet for reflective screen - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lens sheet suitable for use in a reflective screen for projecting and observing an image from an observer side.

[Conventional technology]

As a reflective screen for slides, movies, and video projectors, a flat white plate or a substrate having minute irregularities, which is laminated with an aluminum foil or the like, has a diffuse reflective surface.

Such a conventional reflective screen, except the projection light,
For example, when outside light such as indoor illumination light strikes, the contrast of the projection light is lowered, and the image quality is deteriorated.

Also, the distribution of reflected light is the same in the vertical and horizontal directions,
Considering the general relationship between the observation position and the screen, the horizontal spread is insufficient, but the vertical spread is excessive, which causes a problem in effective use of reflected light.

[Problems to be solved and used by the invention]

In the present invention, eliminating the drawbacks of the prior art,
Provide a lens sheet for use in manufacturing a reflection type screen in which the contrast of projection light is not deteriorated by external light and the image quality is not deteriorated, the horizontal spread of reflected light is wide, and the vertical spread is suppressed. The purpose is to do.

[Means for solving problems]

According to the present invention, a plurality of lenticular lenses are provided in a vertical direction on a surface opposite to an incident surface of projection light, and a convex portion of the lenticular lens has a lenticular lens surface on which light rays incident in a direction perpendicular to the screen are provided. A lens sheet for a reflection type screen, characterized in that a strip-shaped light reflection layer for reflecting incident light is provided in a range that is equal to or less than an angle sin ⁻¹ (1 / n) formed by a light ray when hitting It is a summary.

FIG. 1 is a lens sheet 1 for a reflective screen of the present invention.
Is shown in its used state, and the lens sheet 1 and the back sheet 6 are drawn separately for easy understanding.

The lens sheet 1 is made up of a surface on which projection light is incident, that is, an incident surface 2 and a lens surface 3 which is the opposite surface.
On the lens surface 3, a plurality of lenticular lenses 4 are provided side by side in a vertical direction when viewed in a normal observer's posture, and the convex portion of each lenticular lens also has a strip-shaped light beam in a vertical direction. A reflective layer is provided. In FIG. 1, 6 is a back sheet, 7 is a base material thereof, and 9 is a light absorbing layer, which absorbs light leaked from the lens sheet 1 and is in a direction opposite to an incident surface of projection light. A reflection type screen is formed by using the lens sheet 1 in combination with the lens sheet 1 in order to block external light entering from the screen.

The lens sheet 1 is made of a material having a high transparency and a high refractive index, and is made of a transparent synthetic resin such as acrylic or methacrylic resin such as polymethylmethacrylate, polyvinyl chloride resin, or polycarbonate resin, or glass.
Considering the ease of molding, mass productivity, and light weight, it is preferable to use transparent synthetic resin.

FIG. 2 is a horizontal sectional view of FIG. 1 cut in the horizontal direction.

As the horizontal sectional shape of the lenticular lens 4, a part of various curves, for example, a part of a circle, an ellipse, a parabola, a hyperbola, or a sine (sine) curve is used.
By selecting such a horizontal cross-sectional shape and the refractive index of the lens sheet, the spread of reflected light can be made as desired.

As an example, when making a lens sheet with polymethylmethacrylate having a refractive index of 1.49, a lenticular lens sheet with a horizontal cross-section part of an ellipse with a major axis (lens sheet thickness direction) of 0.7 and a minor axis of 0.5. The horizontal divergence angle when parallel light is incident on is ± 50 °. If the major axis is 0.8 and the minor axis is 0.5, it is ± 40 °. If the major axis is 0.9 and the minor axis is 0.5, it is ± 30 °. Is. Here, the divergence angle is 1 / the maximum value of the reflection intensity (usually the maximum on the optical axis of the lens)
2 is an angle measured from the optical axis direction of the lens in the observation position direction where the reflection intensity of 2 is secured.

The light reflection layer 5 is provided on the convex portion of the lenticular lens 4, and reflects the incident light from the incident surface 2 side. Light rays entering the total reflection surface of the lenticular lens as shown by 9 in FIG. 2 are reflected by the lens surface and emitted to the observer side, while light rays as shown by 10 in FIG. Without layer 5, it does not reflect on the lens surface, but passes through the lens surface. Therefore, the light-reflecting layer 5 may be provided only in an area where the light rays incident on the lens sheet are not totally reflected by the lens surface, and if provided on the front surface of the lens surface, the reflectance of external light is increased, which is not preferable.

FIG. 3 is a diagram for explaining an area of total internal reflection of incident light. Reference numerals 11 to 15 are light rays incident on the lens sheet and parallel to the optical axis of the lens. It has an angle of A _{11 to} A ₁₅ with respect to the normal. A ₁₁ ~ A ₁₅
Let θ be the angle of θ and n be the refractive index of the lens sheet, then when n × sin θ> 1, total reflection occurs and n × sin θ
When ≦ 1, a light ray is emitted downward in FIG. 3 and is not reflected back to the incident side. If n = 1.49, θ = 4
At 2.2 °, n × sin θ = 1, and at an angle θ smaller than this, the incident light is transmitted as it is. The normals 14 and 15 in FIG. 3 show a state of transmission because θ is small.

Therefore, it is preferable that the light reflection layer is provided in a range of angles smaller than θ with θ satisfying n × sin θ> 1, that is, θ = sin ⁻¹ (1 / 1.49) as a boundary. Although only the right half is shown in FIG. 3, the same applies to the left half.

FIG. 4 illustrates the absorption and blocking of external light. Like the projection light 16, a light ray incident from a direction close to the optical axis direction of the lens of the lens sheet 1 is incident and then repeatedly reflected, Although reflected on the incident side, a light ray such as a light ray 17 which is incident at a considerable angle with respect to the optical axis direction of the lens does not undergo total reflection and is transmitted through the lens in the portion where the light reflection layer 5 is not provided, and thus is reflected. do not do. On the contrary, it is better not to have a light reflection layer in this portion.

As shown in FIG. 4, in the usage example of the lens sheet of the present invention, a back sheet in which a light absorbing layer 8 of black or the like is provided on another base material 7 is prepared, and the light absorbing layer 8 side is the lens sheet. Since the lens surface is touched, the transmitted light 17 ′ is absorbed by the light absorbing layer 8 and is not reflected and returned after being transmitted, and the external light 18 from the base material 7 side is not reflected by the base material 7. It is reflected or absorbed by the light absorption layer 8 even if the substrate is transparent, and does not affect the observer side. For the same purpose, the light absorbing layer may be directly provided on the lens surface, particularly on the portion where the light reflecting layer is not present.

The light reflection layer 5 provided in the range described above can be provided by, for example, the thermal transfer method shown in FIGS. 9 to 12.

FIG. 9 exemplifies the structure of a transfer film A used in the thermal transfer method, in which a release layer 22, a light reflection layer 23, and a thermal adhesive layer 24 are provided in this order on a base film 21. The base film 21 is preferably a polyethylene terephthalate film having a thickness of 70 to 100 μm.

FIG. 10 is a simplified representation of the thermal transfer method. First
As shown in FIG. 0, the lens sheet 1 is placed with the lens surface facing upward, and the transfer film is brought into close contact with it. From above, 70-1
When pressure is applied with a rubber roll heated to 00 ° C., the pressure is applied only to the convex portion of the lens, and the light reflection layer 5 is transferred only to that portion.

As shown in FIG. 11, the width of the light reflection layer 5 transferred to the lens sheet 1 depends on the area through which the pressure of the rubber roll is transmitted. Therefore, by changing the hardness and pressure of the rubber, a certain degree of freedom can be obtained. It is possible to have By the method as described above, the light reflection layer 5 having a required width can be provided on the lens sheet 1 as shown in FIG.

Next, the spread of reflected light in the vertical direction of the lens sheet will be described.

The spread of the reflected light in the horizontal direction should be fairly wide so that it can be understood if multiple observers see it side by side, but the spread of the vertical direction is better if the observer stands. It suffices to cover the range of whether you are sitting or lying on the floor. Normally, when you sit down and look at it, it is within the range of ± 5 ° to ± 10 ° and the maximum intensity of reflected light is 1
It is sufficient if / 2 is secured.

The spread of the reflected light in the vertical direction can be realized by making the incident surface of the lens sheet surface a diffusion surface. Figure 5 is the 1
One example is shown, and the lens surface 3 of this lens sheet 1
Is made of the same lenticular lens as that of FIG. 1, but the incident surface on the opposite side is a fine uneven surface. FIG. 6 shows another example, which is a lenticular lens 20 having a plurality of incident surfaces arranged in the horizontal direction.

In the case of FIG. 5, the incident surface can be formed as a predetermined concavo-convex shape by a method such as embossing, sandblasting, applying a matte paint, or attaching a light diffusing sheet during or after the production of the lens sheet. In this method, not only the spread of light in the vertical direction can be controlled, but also the incident light can be prevented from being reflected as it is and appearing to be partially bright.

In the case of FIG. 5, both incident light and reflected light are transmitted through the diffusion surface. Therefore, as shown in FIGS. 7 and 8, a large diffusion effect can be obtained even with a weak diffusion surface. FIG. 7 shows the state of diffusion in the horizontal direction, and FIG. 8 shows the state of diffusion in the vertical direction.

The structure shown in FIG. 6 can be manufactured by molding a predetermined shape on the front surface and the back surface when manufacturing the lens sheet. Sixth
Compared to the one shown in FIG. 5, the one shown in the figure can have a relatively large horizontal expansion. Also, it is relatively easy to determine the spreading characteristics as desired. If a lenticular lens is simply provided, the incident surface tends to reflect the incident light as it is, and a bright portion is likely to occur. Therefore, the lenticular lens surface on the incident surface should be a diffusing surface having a weak diffusion effect.

[Operation and effect of invention]

In the present invention, the spread of the reflected light in the horizontal direction is controlled by a plurality of lenticular lenses in the vertical direction and the light reflecting layer of the convex portion of the lens, so that the spread of the reflected light is based on the optical characteristics of the lens. It is determined.

Further, since the external light from the observer side is transmitted from the portion where the light reflection layer is not provided, the reflection of the external light can be suppressed.

Further, the spread of the reflected light in the vertical direction can be controlled by designing the diffusing surface of the incident surface separately from the horizontal direction, and the spread can be suppressed to a small value, so that the utilization rate of the reflected light is improved.

Therefore, when the lens sheet for a reflection type screen of the present invention is applied to a reflection type screen, there is no problem in observing a projected image even in a bright room in the daytime or under illumination. The spread of the reflected light in the direction can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a usage example of the lens sheet of the present invention, and FIG.
The figures are sectional views showing the use state of the lens sheet of the present invention, and FIGS. 3, 4, 7 and 8 are views for explaining the situation after incidence of incident light, FIG. 5 and FIG. Is a perspective view showing the state of the diffusing surface, and FIGS. 9 to 12 are views showing a method of providing a light reflecting layer. 1 ... Lenticular lens 2 ... Incident surface (diffusing surface) 3 ... Lens surface 4 ... Lenticular lens 5 ... Light reflection layer 6 ... Back sheet 7 ... Base material 8 ... Light absorption layer 19 ... Diffusion Surface 20 ... Lenticular lens

Claims (5)

[Claims] 1. A plurality of lenticular lenses are provided in a vertical direction on a surface opposite to a surface on which projection light is incident, and a convex portion of the lenticular lens is provided with a strip-shaped light reflection layer for reflecting incident light. For a reflective screen, characterized in that the angle between the ray incident on the lenticular lens surface perpendicular to the screen and the normal line is less than sin ^-1 (1 / n) Lens sheet. 2. The lens sheet for a reflective screen according to claim 1, wherein the incident surface is a diffusion surface. 3. The lens sheet for a reflection type screen according to claim 2, wherein the incident surface is a minute uneven surface. 4. The lens sheet for a reflective screen according to claim 2, wherein the incident surface is composed of a plurality of lenticular lenses provided in the horizontal direction. 5. The lens sheet for a reflective screen according to claim 2, wherein a light diffusing sheet is attached to the incident surface to form a diffusing surface.