JP3317786B2 - Fresnel lens sheet and transmission screen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Fresnel lens sheet and a transmissive screen used as a screen of a projection television, a microfilm reader or the like. The present invention relates to a Fresnel lens sheet and a transmission screen that can be provided.

[0002]

2. Description of the Related Art A transmissive screen used in a rear projection type projection television or the like diffuses projection light so as to obtain brightness and uniformity of the screen, and a certain level of brightness even when obliquely observed. The image is made available for observation. Such a transmission screen generally has a configuration in which a Fresnel lens is arranged on a light source side and a lenticular lens on which a black stripe processing is performed is arranged on an observation side. The Fresnel lens directs a light beam incident from a light source toward an observer so that four corners of the screen are not darkened. In addition, the lenticular lens is red,
Green and blue (RGB) lights are mixed to provide color uniformity, and light rays are diffused in the horizontal direction to widen the horizontal viewing angle.

A transmissive screen is composed of a single base material having a Fresnel lens formed on a light source side and a lenticular lens formed on an observation side, and a Fresnel lens sheet having a Fresnel lens formed on one side. And a lenticular lens sheet having a lenticular lens formed on one or both sides. As a transmission screen composed of a Fresnel lens sheet and a lenticular lens sheet, there are a screen in which the lens surface of the Fresnel lens sheet is arranged on the light source side, a screen in which the lens surface of the Fresnel lens sheet is arranged on the lenticular lens sheet side, and the like. .

[0004] In each of these transmission screens, the Fresnel lens and the lenticular lens are arranged close to each other, so that a partial light and dark pattern formed by the Fresnel lens and the vertical pattern of the lenticular lens interfere with each other. Moiré tends to occur, and there is a problem that image quality is degraded due to moiré. In particular,
In a transmissive screen in which the lens surface of the Fresnel lens sheet is arranged on the lenticular lens sheet side, the Fresnel lens and the lenticular lens are arranged adjacent to each other, and moire tends to occur.

For the purpose of reducing such moiré, there has been proposed a method of imparting a light diffusing function to a Fresnel lens sheet. In general, as a light diffusion function, a method of diffusing light by using a light diffusing agent is performed. For example, a method of mixing a light diffusing agent into the entire Fresnel lens sheet, a method of mixing a light diffusing agent into the base layer of the Fresnel lens sheet, a method of mixing a light diffusing agent into the lens layer of the Fresnel lens sheet, and the like are exemplified.

[0006]

However, in the method using the light diffusing agent, it is necessary to use a large amount of the light diffusing agent in order to remarkably reduce the moiré. There is a problem that image quality is deteriorated due to blurring or the like. In the method of mixing the light diffusing agent into the entire Fresnel lens sheet or the method of mixing the light diffusing agent into the base material layer, the distance from the time when the incident light incident on the screen is diffused by the light diffusing agent to the time when the light reaches the lenticular lens is reached. , And the image becomes blurred. Further, the method of mixing the light diffusing agent into the lens layer has a problem that the thickness of the light diffusing layer differs between the peripheral portion and the central portion, resulting in a difference in luminance. SUMMARY OF THE INVENTION It is an object of the present invention to provide a Fresnel lens sheet and a transmission screen capable of remarkably reducing moire without deterioration in image quality such as a decrease in luminance and image blur.

[0007]

Means for Solving the Problems In view of the above-mentioned problems of the prior art, the present inventors have made intensive studies on the lens shape of a Fresnel lens, and as a result, have reached the present invention. That is, the Fresnel lens sheet of the present invention is a Fresnel lens sheet that constitutes a transmission screen in combination with a lenticular lens sheet,
It is characterized by having a Fresnel lens comprising a first lens unit having a convex and / or concave shape with an arc-shaped cross section and a second lens unit having a planar lens surface. Things. Further, the transmission type screen of the present invention is a transmission type screen comprising a Fresnel lens and a lenticular lens, wherein the lens surface is formed in a convex and / or concave shape having an arc-shaped cross section.
, And a second lens unit having a planar lens surface.

As shown in FIGS. 1 to 3, the Fresnel lens sheet and the transmission screen of the present invention have a first lens unit in which the lens surface 3 is formed of a curved surface having a convex or concave arc-shaped cross section. 2 and a second lens unit 4 having a planar lens surface 5. As described above, by forming a part of the lens unit of the Fresnel lens 1 such that the lens surface 3 is convex and / or concave having an arc-shaped cross section, the lens unit 3 is shifted from the lens surface 3 of the first lens unit 2. The emitted light is diffused, the light / dark pattern of the light formed by the Fresnel lens 1 is reduced, and the moire can be significantly reduced, and the viewing angle in the vertical direction can be widened.

As shown in FIG. 1, the lens surface 3 of the first lens unit 2 of the Fresnel lens 1 may be formed in a convex or concave shape having a circular cross section as shown in FIG. As shown, it may be formed in two or more arc-shaped convex or concave cross-sections, or may be formed by combining convex and concave cross-section arcs. From the viewpoint of the productivity of the Fresnel lens, the diffusion characteristics of light, and the like, it is preferable that the lens surface 3 is formed in a convex or concave shape having two or more arcs in cross section, and more preferably two to five arcs in cross section. It is formed in a convex or concave shape. In the present invention, the first
The lens unit 2 may have a configuration in which a lens unit having a lens surface formed in an arcuate cross section and a lens unit having a lens surface formed in an arcuate cross section are mixed.

In the present invention, the size of the convex or concave arc-shaped cross section constituting the lens surface 3 of the first lens unit 2 is appropriately selected according to the size of the Fresnel lens 1 and is particularly limited. But not the moire reduction,
From the viewpoint of the vertical viewing angle and the luminance, the ratio (P / r) of the pitch (P) to the radius of curvature (r) is set to 0.05 to
It is preferably in the range of 1.0, and more preferably in the range of 0.1 to 0.9. This is because if the ratio (P / r) between the pitch (P) and the radius of curvature (r) is less than 0.05, the light emitted from the lens surface 3 is not sufficiently diffused,
This is because the effect of reducing moiré becomes insufficient and the viewing angle in the vertical direction tends to be insufficiently widened.
Conversely, if it exceeds 1.0, the brightness tends to decrease and a bright image tends not to be obtained. In particular, when the lens surface 3 of the Fresnel lens sheet 1 is formed in a concave shape having an arcuate cross section, the ratio (P / r) of the pitch (P) to the radius of curvature (r) is 0.05 to 0.1. It is preferably in the range of 5, more preferably in the range of 0.07 to 0.4.

In the present invention, it is preferable that the lens surface 3 of the first lens unit 2 be formed in a concave shape having an arcuate cross section from the viewpoint of reducing moire and suppressing a decrease in luminance. This is because when the lens surface 3 is formed in a convex shape having an arcuate cross section, the radius of curvature is increased to obtain the same light diffusion performance as compared with a case in which the lens surface 3 is formed into a concave shape having an arcuate cross section. This is because the luminance of the transmissive screen tends to decrease and a sufficiently bright image tends not to be obtained. Further, when the lens surface 3 is formed in a convex shape having an arc-shaped cross section, the light passing through the lens surface 3 is once condensed and then diffused. That's why.

In the Fresnel lens 1 of the present invention, it is important that the first lens unit 2 as described above is mixed with the second lens unit 4 having the lens surface 5 formed in a planar shape. This is because when all the lens units of the Fresnel lens sheet 1 are formed of the first lens unit 2, the light is diffused by the convex or concave lens surface 3 having an arc-shaped cross section. This is because the brightness decreases in the peripheral portion where the brightness is low and the image becomes dark, and the image in the central portion becomes whitish or the image is blurred due to diffuse reflection or brightness reduction in the central portion.

First lens unit 2 and second lens unit 4
The ratio of the first lens unit 2 is not particularly limited, and may be a ratio that can balance image deterioration and moiré due to irregular reflection and a decrease in luminance. % Is preferable. this is,
If the ratio of the first lens unit 2 is less than 30%, the effect of reducing moiré tends to decrease, and if it exceeds 70%, image deterioration due to irregular reflection and reduction in luminance tends to occur. It is.

First lens unit 2 and second lens unit 4
It is preferable that the combination is uniformly dispersed so that there is no sudden change in luminance from the center to the periphery. For example, the first lens unit 2 and the second lens unit 4 are alternately arranged at every one pitch or at a constant pitch, or the ratio of the first lens unit 2 is gradually increased from the center toward the periphery. And combinations of increasing the number. In particular, in order to prevent the image at the center of the first lens unit 2 from whitish or to prevent the image from being blurred,
It is preferable that the lens unit located at the center of the Fresnel lens 1, particularly at the center, be the second lens unit 4. In addition, in order to prevent deterioration of the image in the central portion and to further reduce moire in the peripheral portion where moire is likely to occur, the ratio of the second lens unit is large in the central portion and the first lens unit is in the peripheral portion. It is preferable to increase the ratio of lens units.

The Fresnel lens sheet 1 of the present invention is composed of a synthetic resin base material having good light transmittance, such as an acrylic resin, a polycarbonate resin, an olefin resin, a styrene resin, a vinyl chloride resin, or a resin mixture thereof. It is manufactured by a commonly used method such as a casting method, an injection molding method, a hot press molding method or a method using an active energy ray-curable resin. In the present invention, a light diffusing agent such as alumina, silica, calcium carbonate, or polymer beads may be added in a small amount that does not impair the luminance, for the purpose of further increasing the viewing angle in the vertical direction. Good.

The Fresnel lens sheet 6 having the Fresnel lens 1 having the above lens surface shape is, for example, as shown in FIG.
As shown in (1), a transmission screen is formed by combining with the lenticular lens sheet 7. In the transmission type screen shown in FIG. 4, a lenticular lens sheet 7 is arranged on the observation side, and a Frenel lens sheet 6 is arranged on the light source side such that the Fresnel lens surface is located on the lenticular lens sheet 7 side. . The present invention is particularly suitable for a transmissive screen having such a configuration in which moiré is easily generated, but is not limited to this. The transmissive screen in which the Fresnel lens 1 has the lens surface shape as described above is used. In the case of a type screen, for example, a structure in which the Fresnel lens surface of the Fresnel lens sheet 6 is arranged on the light source side may be used, or a Fresnel lens is formed on the light source side surface and a lenticular lens is formed on the observation side surface. May be formed as a single structure.

The lenticular lens sheet 7 of the present invention
Is composed of a synthetic resin having good light transmission properties such as an acrylic resin, a polycarbonate resin, an olefin resin, a styrene resin, a vinyl chloride resin or a mixture thereof, and is formed by an extrusion molding method, a casting molding method, It is manufactured by a commonly used method such as an injection molding method or a hot press molding method.

The lens shape of the lenticular lens formed on the lenticular lens sheet 7 is not particularly limited, and the shape of a commonly used lenticular lens having a semicircular cross-section or a semi-elliptical cross-section may be used. Can be used. The lenticular lens sheet 7 includes a single-sided lenticular lens sheet having a lenticular lens formed on one of an exit surface and an incident surface, and a double-sided lenticular lens sheet having a lenticular lens formed on both an exit surface and an incident surface. Can be used. Furthermore, on the observation side surface of the lenticular lens sheet 7, for the purpose of improving the contrast of the image,
A black stripe 8 is formed in a light opaque part of the lenticular lens.

In the present invention, in order to further reduce the moire caused by the Fresnel lens and the lenticular lens, when the pitch of the Fresnel lens is 1, the pitch of the lenticular lens is N + 0.35 to 0.4.
3, N + 0.55 to 0.73, 1 / (N + 0.35
0.43) or 1 / (N + 0.55 to 0.73). Here, N is a natural number of 1 to 12.

[0020]

The present invention will be specifically described below with reference to examples. Example 1 Pitch 0.06 mm, radius of curvature 0.16 mm on lens surface
A first lens unit in which three convex portions having an arc-shaped cross section are continuously formed, and a second lens unit having a planar lens surface are formed such that the center becomes the second lens unit. A 3 mm thick transparent methacrylic resin plate (Acrylite L # 001 manufactured by Mitsubishi Rayon Co., Ltd.) is heated and pressed using a brass lens mold having a circular Fresnel lens pattern with a pitch of 0.12 mm alternately arranged every pitch. The pitch is 0.06 mm as shown in FIG.
A first lens unit 2 having a lens surface 3 formed by a curved surface with three consecutive concave portions having a radius of curvature of 0.16 mm and having an arc-shaped cross section, and a second lens unit 3 having a planar lens surface 5
Were alternately arranged at every pitch to obtain a Fresnel lens sheet 6.

The obtained Fresnel lens sheet 6 and a lenticular lens sheet 7 having a pitch of 0.41 mm with a black stripe 8 formed on the front face are combined as shown in FIG. 4 and mounted on a projection television as a transmission screen. The image and moire were observed. As a result, almost no moiré was observed, and a bright and high-quality image having a gain (G ₀ ) of 4.7 was obtained. In particular, no image deterioration was observed at the center. Further, the vertical directivity (αV) was 8 degrees, and the viewing angle in the vertical direction was wide.

Example 2 A pitch 0.06 mm and a radius of curvature 0.16 mm are formed on the lens surface.
A circular lens having a pitch of 0.12 mm, in which a first lens unit having three consecutive convex portions having an arc-shaped cross section and a second lens unit having a planar lens surface are arranged as follows. Using a brass lens mold having a Fresnel lens pattern, a transparent methacryl resin plate (Acrylite L # 001 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 3 mm was formed by a hot press method, and the pitch was 0.06 mm and the radius of curvature was 0. .
A first lens unit 2 having a lens surface 3 formed by a curved surface having three consecutive 16 mm arc-shaped concave portions and a second lens unit 3 having a planar lens surface 5 are as follows. The arranged Fresnel lens sheet 6 was obtained.

Area within 10 cm from the center: One pitch of the second lens unit is disposed every two pitches of the first lens unit, and the second lens unit is disposed at the center. Area within 30 cm from the periphery: Second lens One pitch of the first lens unit is arranged for every two pitches of the unit. Areas other than the above: the first lens unit and the second
The lens units are alternately arranged at every pitch. The obtained Fresnel lens sheet 6 and a lenticular lens sheet 7 having a pitch of 0.41 mm with a black stripe 8 on the front face are combined as shown in FIG. It was mounted on a projection television as a transmission screen, and its images and moire were observed. As a result, almost no moiré was observed, and a bright and high-quality image having a gain (G ₀ ) of 4.8 was obtained. In particular, no image deterioration was observed at the center. In addition, vertical directivity (αV)
However, the vertical viewing angle was as wide as 8 degrees.

Comparative Example 1 A pitch of 0.12 in which the lens surface of each lens unit is flat.
A transparent methacrylic resin plate (Acrylite L # 001 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 3 mm is formed by a hot press method using a lens mold made of brass having a circular Fresnel lens pattern of 2 mm to obtain a Fresnel lens sheet 6. Was. The obtained Fresnel lens sheet 6 and a lenticular lens sheet 7 having a pitch of 0.41 mm with a black stripe 8 on the front face were combined as shown in FIG. Moire was observed. as a result,
Although a bright image having a gain (G ₀ ) of 5.0 was obtained, moire was remarkable. In addition, vertical directivity (αV)
Had a slightly narrow vertical viewing angle of 7 degrees.

Comparative Example 2 A Fresnel lens sheet 6 was obtained in the same manner as in Comparative Example 1 except that a methacrylic resin plate containing 0.3% by weight of silica particles having a particle size of 4 μm was used. The obtained Fresnel lens sheet 6 and a lenticular lens sheet 7 having a pitch of 0.41 mm with a black stripe 8 on the front face were combined as shown in FIG. Moire was observed. As a result, a bright image having a gain (G ₀ ) of 4.3 was obtained, and the vertical directivity (αV) was 9 °, which was a wide viewing angle in the vertical direction, but was extremely moire.

COMPARATIVE EXAMPLE 3 Three circular arc-shaped convex portions having a pitch of 0.06 mm and a radius of curvature of 0.16 mm were formed continuously on the lens surface of each lens unit, and a circular Fresnel lens pattern having a pitch of 0.12 mm was formed. A transparent methacrylic resin plate (Acrylite L # 001 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 3 mm was formed by a hot press method using a brass lens mold having
There was obtained a Fresnel lens sheet 6 in which the lens surface of each lens unit was formed with a curved surface in which three concave portions having an arc-shaped cross section with a pitch of 0.06 mm and a radius of curvature of 0.16 mm were continuous.

The obtained Fresnel lens sheet 6 and a lenticular lens sheet 7 having a pitch of 0.41 mm with a black stripe 8 on the front face are combined as shown in FIG. 4 and mounted on a projection television as a transmission screen. The image and moire were observed. As a result, almost no moiré was observed, and the vertical directivity (αV)
Was 9 degrees and the viewing angle in the vertical direction was wide, but the gain (G ₀ ) was slightly low at 4.3, the image was slightly whitish at the center, and the image was slightly blurred.

[0028]

The Fresnel lens sheet and transmissive screen of the present invention can be used to reduce whitening of an image, blurring of an image, reduction in luminance, etc. by forming a lens surface of a part of the Fresnel lens into a specific shape. It is possible to provide an excellent transmissive screen having a wide vertical viewing angle while significantly reducing moire without causing image deterioration.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a structure of a Fresnel lens sheet of the present invention.

FIG. 2 is a partial sectional view showing the structure of the Fresnel lens sheet of the present invention.

FIG. 3 is a partial sectional view showing the structure of the Fresnel lens sheet of the present invention.

FIG. 4 is a cross-sectional view showing the structure of the transmission screen of the present invention. 1: Fresnel lens 2: First lens unit 3: Lens surface of first lens unit 4: Second lens unit 5: Lens surface of second lens unit 6: Fresnel lens sheet 7: Lenticular lens sheet 8: Black stripe

Claims (2)

(57) [Claims] 1. A Fresnel lens sheet comprising a transmission type screen in combination with a lenticular lens sheet, wherein a first lens unit having a lens surface formed in a convex and / or concave shape having an arc-shaped cross section, and a lens surface having a flat surface. A Fresnel lens sheet having a Fresnel lens comprising a second lens unit formed in a shape. 2. A transmission screen comprising a Fresnel lens and a lenticular lens, wherein a first lens unit having a lens surface formed in a convex and / or concave shape having an arc-shaped cross section, and a lens surface formed in a planar shape. Second formed
A transmissive screen comprising a Fresnel lens comprising: