JPH11248908A - Flat lens - Google Patents

Abstract

(57) [Problem] To provide a flat lens which can be reduced in weight, is bright in any direction, has a wide field of view, and can improve contrast. SOLUTION: A transparent base material 11 and a colored hot melt adhesive layer 13 formed on the image light incident side surface of the transparent base material
And a number of transparent beads 12 formed of a single layer fixed to the colored hot melt adhesive layer, and a transparent resin formed on the transparent beads and having a refractive index smaller than that of the transparent beads. A Fresnel lens is formed directly on the light incident side surface of the transparent resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen for a rear projection type display device, a viewing angle widening plate for a liquid crystal display device, a plasma display device, an electroluminescence display device, etc., a backlight for a liquid crystal display, various illumination light sources and the like. The present invention relates to a flat lens used for a light diffusion plate or the like that diffuses light.

[0002]

2. Description of the Related Art In recent years, a projection type display device using a light bubble such as a liquid crystal panel, which emits a light beam having a polarization characteristic, has been developed. In a projection type display device using liquid crystal, image light spatially modulated by a liquid crystal panel is enlarged and projected on a screen by a projection lens. This projection type display device includes a front projection type or a rear projection type device.

FIG. 5 shows a configuration example of a rear-projection display device among these two display devices. The rear projection type display device shown in FIG. 5 has a projection optical system 28 for emitting image light.
, A transmission screen 31, and a mirror 30 that reflects the image light A emitted from the projection optical system 28 and guides the image light A to the transmission screen 31. As shown in FIG. 6, the transmissive screen 31 generally includes a Fresnel lens 33 and a lenticular lens 34, and transmits the image light A projected from the projection optical system 28 to the Fresnel lens 3.
After making the light nearly parallel by 3, the lenticular lens 3
4 is configured to diffuse right and left.

As described above, in the rear projection type display device, the image light A emitted from the projection optical system 28 is enlarged and projected on the transmission type screen 31. Observation of a projected image can be performed as light transmitted through the transmission screen 31 from the opposite side.

[0005]

Since the lenticular lens diffuses the image light mainly in the left-right (horizontal) direction as described above, the lenticular lens can be used even when the projection screen is viewed obliquely from the right or left. Can be recognized. However, since the image light can hardly be diffused in the vertical (vertical) direction orthogonal to the diffused direction, when the projection screen is viewed obliquely from above or below, the range in which a clear image can be recognized becomes extremely narrow. There is a problem.

In addition, since the lenticular lens has a linear array of lenses arranged regularly, there is a problem that moire interference fringes are generated in an image and image quality is degraded.

Further, in order to cope with higher definition of an image, it is necessary to reduce a lens size or a lens pitch of a screen. However, in a conventional lenticular lens, it is said that the limit is about 0.4 mm due to a limitation in a manufacturing method. And
For example, there is a problem that it cannot be applied to a liquid crystal projection display of a resolution XGA (1024 × 768 pixels) class.

[0008] As one of means for solving the above-mentioned problem,
LCD Intelligence (LCD Intelligence),
[11] (1997) p. 107 has a wide angle screen. This wide angle screen is a single screen in which a circular Fresnel lens is provided on the projector side and a lenticular lens is provided on the viewer side. This wide angle screen has the features that it can be reduced in weight, the lens pitch can be fine, the resolution is high, and the occurrence of moire interference fringes is small, but since there is no flat portion on the light emission side surface,
Light-shielding printing (black stripes) for absorbing ambient light entering from the outside and suppressing contamination with image light cannot be formed. Therefore, it is necessary to color the entirety to improve the contrast, and there is a problem that the light transmittance is reduced.

Further, as a transmission screen used for a rear projection display device or the like, Japanese Patent Application Laid-Open No. 2-77736 discloses a flat lens in which a spherical lens is fixed with resin or the like. According to this technique, a screen having a high resolution and free from moiré interference fringes can be obtained. However, since a wide field of view is to be obtained by the diffusion panel in contact with the spherical lens, the image light is scattered backward when passing through the diffusion panel, and a part of the image light is returned to the direction of the projection optical system. There is. Furthermore, since ambient light around the display device can easily enter from the light exit surface side of the screen, there is a problem that image contrast is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to reduce the weight, to provide a bright, wide field of view, and to improve contrast in any direction. It is intended to provide a lens.

[0011]

The flat lens according to the present invention comprises a transparent substrate, a colored hot-melt adhesive layer formed on the light-incident side of the transparent substrate, and a colored hot-melt adhesive. A large number of transparent beads consisting of a single layer fixed to the layer, formed on the transparent beads, a transparent resin having a refractive index smaller than the refractive index of the transparent beads,
The transparent resin layer has a Fresnel lens shape on the surface.

Next, the operation of the flat lens according to the present invention will be described. The flat lens of the present invention is used in place of the Fresnel lens 33 and the lenticular 34 of the conventional transmission screen shown in FIG. As shown in FIG. 4, according to the flat lens of the present invention, incident on the transparent resin layer 16 via the fresnel lens 16a of the image light A is formed on the surface of the light incident side of the planar lens L _1, Most of the image light A is incident on the transparent beads 12 as substantially parallel light. The refractive index n _B of the transparent beads 12 is the refractive index of the transparent resin layer 16.
is greater than n _P, the image light A incident on the transparent beads 12 is condensed and emitted from the transparent substrate 11 as isotropic diffuse light.

On the other hand, the image light A ′ which is not incident on the transparent beads 12 even though it is incident on the planar lens L ₁ , that is, the image light which is not affected by the lens action of the transparent beads 12 is applied to the colored hot melt adhesive layer 13 Absorbed.

The ambient light B enters the flat lens L ₁ from the transparent substrate 11 side and reaches the colored hot melt adhesive layer 13, but most of the ambient light B is absorbed here, so that it passes through the transparent beads 12. It is unlikely to be stray light.

As described above, by applying the flat lens of the present invention to a transmission screen, a viewer can view a bright, high-contrast image from any angle.

In the flat lens according to the present invention, the refractive index n _B of the transparent beads and the refractive index n _P of the transparent resin layer are:
0.1 ≦ n _B −n _P ≦ 0.9, n _B ≧ 1.4, _P ≧ 1.
It is preferable to satisfy the condition of each formula (3).

When the refractive index n _{B of the} transparent beads and the refractive index n _P of the transparent resin layer are in the ranges satisfying the above expressions, the diffusion angle of the emitted image light increases, and the viewing angle of the image increases. Here, n _B -n value of _P becomes insufficient diffusion of the image light becomes less than 0.1 is not preferable because the viewing angle is narrowed. If the value of the inverse to n _B -n _P exceeds 0.9, increases reflection loss at the interface between the transparent resin layer and the transparent beads is, as it reduces the light transmittance is not preferred. In consideration of such a point, the value of n _B −n _P is 0.2 or more and 0.
More preferably, it is set to 8 or less.

In the flat lens according to the present invention, the colored hot melt adhesive layer may be entirely composed of a colored layer. The colored hot melt adhesive layer is formed on a transparent layer and a light incident side surface of the transparent layer. It can also be constituted by a colored layer. It is preferable that the colored layer constituting the whole or a part of the colored hot melt adhesive layer is made of a resin colored with a black or gray pigment or dye. However, red, green, blue, or a mixture thereof may be used.

Further, in the flat lens according to the present invention,
In order to suppress or control the reflection of light, an anti-reflection treatment or an anti-glare treatment may be performed on the surface of the transparent substrate on the light emission side to form an anti-reflection film or an anti-glare film.

In this specification, the term "transparent" means that the target light, that is, the light to be transmitted through the lens, can be transmitted therethrough, and also includes what is called translucent. .

[0021]

Next, an embodiment of a flat lens according to the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing one embodiment of the flat lens according to the present invention. Planar lens L ₁ shown in FIG. 1 includes a transparent substrate 11, the transparent formed on a surface of the light incident side of the substrate 11 a colored hot-melt adhesive layer 13
And a number of transparent beads 12 consisting of a single layer fixed to the colored hot melt adhesive layer 13;
2 and a transparent resin layer 16 formed on the transparent resin layer 2. The transparent resin layer 16 is made of a transparent resin having a refractive index smaller than the refractive index of the transparent beads 12,
A Fresnel lens is directly formed on the light incident side surface.

Next, a method of manufacturing the flat lens according to the present embodiment will be described. First, a colored hot melt adhesive layer 13 is formed (coated) on the light incident side surface of the transparent base material 11 to be in a solidified or semi-solid state, and a plurality of transparent hot melt adhesive layers 13 are formed on the surface of the colored hot melt adhesive layer 13. One bead 12
The layers are dispersed and arranged while maintaining the arrangement of the layers, that is, the single particle layer. The transparent beads 12 are pressed against the colored hot melt adhesive layer 13 with a predetermined pressure while melting or softening the colored hot melt adhesive layer 13 by heating this using, for example, a hot press device. The transparent bead 12 is embedded in the colored hot melt adhesive layer 13 by a part of its diameter, that is, a predetermined depth. further,
Heating and pressurizing the colored hot melt adhesive layer 13 are eliminated, and the colored hot melt adhesive layer 13 is naturally cooled or forcibly cooled to room temperature to solidify the colored hot melt adhesive layer 13. Next, a transparent resin layer 16 made of a transparent resin having a refractive index smaller than that of the transparent beads 12 is coated on the exposed surface of the transparent beads 12 embedded in the colored hot melt adhesive layer 13. Finally, the surface on the light incident side of the transparent resin layer 16 is formed into a Fresnel lens shape by a casting method, a pressing method, or the like.
Obtaining a planar lens L ₁ and the Fresnel lens 16a faces the light incident side of the.

FIG. 2 is a cross-sectional view schematically showing another embodiment of the flat lens according to the present invention. Construction of the planar lens L ₂ of the present embodiment is planar lens L ₁ shown in FIG. 1
But the colored hot melt adhesive layer 1
3 'is composed of two layers: a transparent layer 13a formed on the light incident side surface of the transparent base material 11 and a colored layer 13b formed on the light incident side surface of the transparent layer 13a. There is a feature in the point.

FIG. 3 is a sectional view schematically showing still another embodiment of the flat lens according to the present invention. Construction of the planar lens L ₃ of the present embodiment is similar to the structure planar lens L _1, L ₂ shown in FIGS. 1 and 2, anti-reflection surface of the light emission side of the transparent substrate 11 A film 17 is formed. This antireflection film 17 is formed by antireflection processing or antiglare processing. This antireflection film 1
7, the transparent substrate 11 of the ambient light B (see FIG. 4)
Specular reflection on the surface can be suppressed, and as a result, a decrease in image contrast can be prevented.

In FIG. 3, the colored hot melt adhesive layer 13 'composed of the transparent layer 13a and the colored layer 13b shown in FIG. 2 is used as the colored hot melt adhesive layer. A single-layer colored hot melt adhesive layer 13 composed of only the colored layer may be used.

In each of the planar lenses shown in FIGS. 1 to 3, the transparent beads 12 and the transparent resin layer 16 have a refractive index n _B of the transparent beads 12 and a refractive index n _p of the transparent resin layer 16 of 0.1. 1 ≦ n _B −n _P ≦ 0.9, n _B ≧ 1.4, n _P
It satisfies the condition of each expression of ≧ 1.3. As a material of the transparent beads 12, for example, glass, acrylic resin, polystyrene resin, or the like is used. In addition, as a material of the transparent resin layer 16, for example, a transparent resin such as an acrylic resin, a polyester resin, a polyurethane resin, a vinyl chloride resin, or a polyolefin resin can be used.

In the flat lens shown in FIGS. 1 to 3, the material of the transparent substrate 11 is, for example, acrylic resin, polycarbonate resin, vinyl chloride resin, polyolefin resin, polyester resin or polystyrene resin. Can be used.

Further, in the planar lens shown in FIG. 3, the method of the anti-reflection treatment or the anti-glare treatment applied to the light emitting side surface of the transparent base material 11 is not particularly limited, but may be any of these methods. As an example, in the anti-reflection treatment, a method of forming a known thickness of a known anti-reflection film such as silica or alumina on the surface of the transparent substrate 11 by coating or vacuum deposition is used.
In the anti-glare treatment, a method of mixing silica or plastic beads into a resin to coat the surface of the transparent substrate 11, or a method of sand blasting or embossing to form irregularities on the surface of the transparent substrate 11. There is a method of forming.

The colored hot-melt adhesive layer 13 composed of only the colored layer shown in FIG. 1 and the colored layer 13b of the colored hot-melt adhesive layer 13 'shown in FIGS.
It has a sufficient adhesive strength to the transparent beads 12 and the transparent substrate 11. Base resin for forming colored hot melt adhesive layer 13 shown in FIG. 1, and FIGS. 2 and 3
Acrylic resin, polycarbonate resin, polyolefin resin, polystyrene resin, polyester resin,
Polyurethane resin, polyvinyl chloride resin, vinyl chloride
A hot melt adhesive made of a vinyl acetate copolymer or a polyamide resin is used. By dispersing a pigment in these base resins or dyeing the base resin with a dye, the colored hot melt adhesive layer 13 shown in FIG. 1 and the colored layer 13b shown in FIGS.
Can be formed.

The coating of the colored hot melt adhesive layer 13 shown in FIGS. 1 to 3 can be performed by, for example, knife coating, roll coating, gravure coating, kiss coating, spray coating, blade coating, rod coating, or the like.

When the colored hot melt adhesive layer 13 'has a two-layer structure of a transparent layer 13a and a colored layer 13b,
A transparent hot-melt adhesive is applied by the above-described coating method to form a transparent layer 13a, and then a colored hot-melt adhesive is applied by a similar method to form a colored layer 13b.

[0033]

Next, specific examples of the flat lens according to the present invention will be described. Example 1 A planar lens having the structure shown in FIG. 1 was manufactured as follows.

First, a polyester-based resin (manufactured by Toyobo Co., Ltd.) was placed on one surface of a flat transparent substrate 11 (thickness: 0.25 mm) made of polyethylene terephthalate resin.
A hot-melt adhesive 13 was formed by applying a colored layer prepared by mixing 3 parts by weight of black carbon with 100 parts by weight of a black carbon to a thickness of 10 μm after drying with a knife coater.

Next, transparent beads 12 (using glass beads) having a refractive index of 2.20 and an average diameter of 50 μm are densely arranged on the surface of the colored hot-melt adhesive layer 13, and heated to a temperature of 120 ° C. After holding at a pressure of 3 kg / cm ² for 10 minutes, the transparent beads 1 were cooled to room temperature.
2 was embedded in the colored hot melt adhesive layer 13. next,
A transparent acrylic resin having a refractive index of 1.49 (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Dianal LR-162) is applied to the exposed surface of the transparent beads 12 by a gravure coater, and after drying, a circular Fresnel lens shape is formed on the surface. By heating and pressing using a mold and transferring the shape, a planar lens of this example was obtained.

Instead of the Fresnel lens 33 and the lenticular lens 34 shown in FIG. 6 constituting the transparent screen 31 used in the rear projection type display device shown in FIG. 5, a flat lens of this embodiment is mounted. Observation of the projected image showed that the viewing angle was 1.3 times in the horizontal direction and 2.4 times in the vertical direction as compared with the conventional transmission screen. In addition, high-quality images with high contrast and good resolution could be observed. Example 2 A planar lens having the structure shown in FIG. 2 was manufactured as follows.

First, a polyester resin (manufactured by Toyobo Co., Ltd.) was placed on one surface of a flat transparent substrate 11 (0.25 mm thick) made of polyethylene terephthalate resin.
(Trade name: Byron 200) was applied by a knife coater to a thickness of 6 μm after drying to form a transparent layer 13a. Furthermore, a coloring layer 13b in which 3 parts by weight of black carbon is blended with 100 parts by weight of a polyester resin (trade name: Byron 630, manufactured by Toyobo Co., Ltd.)
Was dried by a knife coater to a thickness of 5 μm after drying to form a colored hot melt adhesive 13 ′.

Next, transparent beads 12 (using glass beads) having a refractive index of 1.70 and an average diameter of 50 μm are densely arranged on the surface of the colored hot melt adhesive layer 13 ′, and the temperature is adjusted to 120 ° C. by hot pressing. After maintaining at a temperature of 3 ° C. and a pressure of 3 kg / cm ² for 10 minutes, the transparent beads 12 were embedded in the colored hot melt adhesive layer 13 ′ by cooling to room temperature. Next, a transparent acrylic resin having a refractive index of 1.49 (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Dianal LR-162) is applied to the exposed surface of the transparent beads 12 by a gravure coater, and after drying, the surface is covered with circular Fresnel. The flat lens of this example was obtained by heating and pressing using a lens-shaped mold and transferring the shape.

Instead of the Fresnel lens 33 and the lenticular lens 34 shown in FIG. 6 constituting the transparent screen 31 used in the rear projection type display device shown in FIG. 5, a flat lens of this embodiment is mounted. When the projected image was observed, a viewing angle of 1.2 times in the horizontal direction and 2.2 times in the vertical direction were obtained as compared with the conventional transmission screen. In addition, high-quality images with high contrast and good resolution could be observed. Example 3 A planar lens having the structure shown in FIG. 1 was manufactured as follows.

In this embodiment, transparent beads 12 (using styrene beads) having a refractive index of 1.59 and an average diameter of 40 μm are used as the transparent beads 12, and the temperature condition of the hot press is set to 1
A flat lens was manufactured in the same manner as in Example 1 except that the temperature was changed to 00 ° C.

Instead of the Fresnel lens 33 and the lenticular lens 34 shown in FIG. 6 which constitute the transparent screen 31 used in the rear projection type display device shown in FIG. 5, the flat lens of this embodiment is mounted. Observation of the projected image showed that the viewing angle was 1.1 times in the horizontal direction and 2.0 times in the vertical direction as compared with the conventional transmission screen. In addition, high-quality images with high contrast and good resolution could be observed. Example 4 A planar lens having the structure shown in FIG. 3 was manufactured as follows.

First, in the flat lens manufactured in the same manner as in Example 1, the surface of the transparent substrate 11 on the light emission side was
An anti-reflection film 17 made of SiO _{2 was formed} to a thickness of 100 nm using a vacuum evaporation method.

Instead of the Fresnel lens 33 and the lenticular lens 34 shown in FIG. 6 constituting the transparent screen 31 used in the rear projection type display device shown in FIG. 5, a flat lens of this embodiment is mounted. Observation of the projected image showed that the viewing angle was 1.3 times in the horizontal direction and 2.4 times in the vertical direction as compared with the conventional transmission screen. In addition, high-quality images with high contrast and good resolution could be observed.

[0044]

As described above, the flat lens according to the present invention comprises a transparent base material, a colored hot melt adhesive layer formed on the light incident side of the transparent base material, and a colored hot melt adhesive layer. It is composed of a number of transparent beads formed of a single layer fixed to the adhesive layer, and a transparent resin layer formed on the transparent beads and formed of a transparent resin having a refractive index smaller than that of the transparent beads. Since the Fresnel lens is directly formed on the surface of the transparent resin layer on the light incident side, a bright and high-contrast image can be obtained from any angle.

Here, in the flat lens of the present invention,
The refractive index and n _B of the transparent beads, the refractive index n _P of the transparent resin layer _{is, 0.1 ≦ n B -n P ≦} 0.9, n B ≧ 1.
4. If the material of the transparent resin layer is selected so as to satisfy the condition of each formula of n _P ≧ 1.3, it is possible to obtain a display device having a wide viewing angle when viewed from any direction, and the brightness of the image. Can be improved without lowering the contrast.

In the flat lens according to the present invention, when the surface on the light emitting side of the transparent substrate is subjected to an antireflection treatment or an antiglare treatment, specular reflection of environmental light can be suppressed, and the contrast of an image can be reduced. It does not decline.

Therefore, according to the planar lens of the present invention,
Further, a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a flat lens according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the flat lens according to the present invention.

FIG. 3 is a sectional view showing still another embodiment of the flat lens according to the present invention.

FIG. 4 is a diagram illustrating the operation of the flat lens according to the present invention.

FIG. 5 is an explanatory diagram showing an example of a conventional rear projection display device.

FIG. 6 is a sectional view showing an example of a conventional transmission screen.

[Explanation of symbols]

L ₁ , L ₂ , L ₃ planar lens 11 transparent substrate 12 transparent beads 13 colored hot melt adhesive layer 16 transparent resin layer 16a Fresnel lens

Claims (4)

[Claims] 1. A transparent base material, a colored hot melt adhesive layer formed on a light incident side surface of the transparent base material, and a plurality of transparent layers composed of a single layer fixed to the colored hot melt adhesive layer. And a transparent resin layer formed on the transparent beads and made of a transparent resin having a refractive index smaller than the refractive index of the transparent beads. A Fresnel lens is formed on the light incident side of the transparent resin layer. Is a flat lens directly formed. 2. A refractive index and n _B of the transparent beads, the refractive index n _P of the transparent resin layer _{is, 0.1 ≦ n B -n P ≦} 0.9, n B ≧ 1.4, n P 2. The planar lens according to claim 1, wherein the condition of each expression of ≧ 1.3 is satisfied. 3. The flat lens according to claim 1, wherein the colored hot melt adhesive layer comprises a transparent layer and a colored layer formed on the light incident side of the transparent layer. 4. An anti-reflection treatment or an anti-glare treatment is applied to a surface of the transparent substrate on a light emission side.
4. The planar lens according to 2 or 3.