JP2000098104A - Planar lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a satisfactorily visible image whose luminance and contrast are improved by constituting a planar lens so that one surface may be provided with a lens layer which is constituted by fixing many spherical lenses arranged in a single layer state by an optical absorption layer which is thinner than the lens thickness of the spherical lens and the other surface may be provided with an optical diffusing layer having anisotropic light diffusing characteristics. SOLUTION: The lens layer is formed by arranging many spherical lenses 11 in a single layer state. And the lens layer is formed by fixing many spherical lenses 11 in a single layer arrangement by the optical absorption layer 12 whose thickness is smaller than the thickness of the spherical lens 11. Thus, each spherical lens 11 is positioned, and a part of each spherical lens 11 projects from the optical absorption layer 12, then, the lens layer is constituted so as to efficiently receive light such as projection image light, etc., by the spherical lens 11. Besides, as for the light diffusing layer 13 which is installed on one side and whose light diffusing characteristics are anisotropic, characteristics of diffusing transmitted light by a large angle in a horizontal direction and hardly diffusing the light in the vertical direction are imparted to the layer 13, then, such a loss that the image light is diffused in a direction where a viewer does not view the image light is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat lens suitable for use as a magnifying screen, a viewing angle magnifying plate or a light diffusing plate of various display devices.

[0002]

2. Description of the Related Art Heretofore, as a lens member that can be used as a transmission-type magnifying screen of a rear projection display device, a lens member in which a large number of spherical lenses are arranged and fixed on a transparent substrate via a resin or the like has been known. JP-A-2-77736).
This is because, with the conventional lenticular lens, interference fringes due to moiré are generated in the image and the display quality is greatly reduced, and it is difficult to manufacture a large-sized plate, and even if it is slightly scratched, it becomes unusable and difficult to handle. It is an improvement in points.

However, when such a lens member is used as the screen or the like, there is a problem that an image in the front direction is dark, and disturbance light enters from the viewing side of the screen and becomes stray light inside the apparatus to lower the contrast of the image. there were.

[0004]

SUMMARY OF THE INVENTION According to the present invention, moiré hardly occurs,
It is an object of the present invention to develop a lens member capable of forming an enlarged screen which is easy to handle and manufacture a large plate, has a wide viewing angle, and is excellent in image brightness and contrast.

[0005]

The present invention has a lens layer in which a large number of spherical lenses in a single layer arrangement are fixed with a light absorbing layer thinner than the lens thickness on one side, and the other side has a light diffusion characteristic. An object of the present invention is to provide a planar lens having an anisotropic light diffusion layer.

[0006]

According to the flat type lens of the present invention, it is easy to handle and a large plate can be easily and efficiently manufactured. Even when used for a transmission type magnifying screen, moire is hardly generated in an image, and the image light is visually recognized. Enlarged projection can be performed with a high degree of control in a viewing angle range that is advantageous to the user, and an image with excellent brightness and contrast and good visibility can be formed. When the surface of the lens is coated with a low-refractive-index material, reflection at the lens layer can be suppressed to form an enlarged image with superior brightness.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flat lens according to the present invention has a lens layer in which a number of spherical lenses arranged in a single layer are fixed with a light absorbing layer thinner than the lens thickness on one side, and on the other side. The light-diffusing characteristic comprises an anisotropic light-diffusing layer.
Examples thereof are shown in FIGS. 1, 2 and 3. 1 is a flat lens, 11 is a spherical lens, 12 is a light absorption layer, 13 and 16 are light diffusion layers, 15 is a light transmissive substrate, 14 is a light diffusion surface, 17 is a transparent adhesive layer, and 18 is a transparent adhesive layer. Overcoat.

Examples of the spherical lens include inorganic particles which may be conductive, such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, antimony oxide, and polymethyl methacrylate and polyurethane. Appropriate materials such as crosslinked or uncrosslinked organic particles composed of various polymers can be used.
Spherical lenses that can be preferably used have excellent transparency and scratch resistance.

The size of the spherical lens can be appropriately determined according to the size of the flat lens to be formed, the assumed visual distance, and the like. ３3 mm, especially 20 μm〜1 mm. Although a spherical lens is generally used as the spherical lens, a hemisphere or the like may be used.

The lens layer is formed in a state where a large number of spherical lenses 11 are arranged in a single layer as shown in the figure. Thereby, it is possible to improve the resolution and the like. From the viewpoint of improving the display quality and the like, it is preferable that the spherical lenses in the single-layer arrangement have uniform diameters as small as possible and are distributed as uniformly as possible.

The lens layer is formed by fixing a large number of the single-layered spherical lenses 11 with a light absorbing layer 12 having a thickness smaller than the lens thickness, as shown in the figure. Thereby, while positioning each spherical lens, a part of each spherical lens protrudes from the light absorption layer, and it is possible to form a lens layer in which light such as projected image light can be efficiently received by the spherical lens.

From the viewpoint of the light receiving efficiency and the like, the preferable ratio of the spherical lens protruding from the light absorbing layer is 2% of the spherical lens diameter.
0% or more, especially 30% or more, especially 50% or more,
The present invention is not limited to this, and can be appropriately determined according to the thickness of the light absorbing layer and the like necessary for fixing the spherical lens.

The lens layer is formed by forming a light-absorbing layer or the like into a light-diffusing layer by an appropriate method such as a knife coater, a roll coater, a gravure coater, a kiss coater, a spray coater, a blade coater, or a rod coater. And spread it on a support base made of a light-transmissive substrate, etc., scatter the spherical lenses on the spread layer, arrange them in a single layer, and press the single-layer spherical lenses by pressing or the like as necessary. A method of embedding and fixing in the developing layer, or mixing and forming a spherical lens with the forming material of the light absorbing layer, coating and developing on a support,
The spreading layer can be formed by an appropriate method such as a method of solidifying the layer by an ultraviolet curing method or a drying method, if necessary.

In the above description, the light absorbing layer fixes the spherical lens, and based on the light absorbing property, as shown in FIG. 4, the light 31 such as the projected image light transmitted from the lens layer side through the portion other than the spherical lens, Absorbs disturbance light 32 and the like incident from the light diffusion layer 16 side on the viewing side or the like to prevent stray light from being generated,
The purpose is to prevent a decrease in image contrast.

Therefore, the light absorbing layer can be formed of an appropriate film forming component such as an adhesive in terms of fixing the spherical lens. By the way, examples include acrylics and carbonates, olefins and styrenes, polyesters and urethanes, celluloses and vinyl chlorides, vinyl acetates and vinyl chloride / vinyl acetate copolymers, amides and imides, Polymers such as sulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, vinyl alcohol, vinylidene chloride, vinyl butyral, arylate, polyoxymethylene, epoxy, and blends thereof can give. Further, for example, various curable resins such as an ultraviolet curable resin and a thermosetting resin such as a polyester resin, an acrylic resin, a urethane resin, an amide resin, a silicone resin, and an epoxy resin can be used.

The provision of the light-absorbing property to the light-absorbing layer composed of the film-forming component can be performed by an appropriate method such as a method in which a suitable coloring agent such as a pigment or a dye is mixed with the film-forming component. it can. In the case of the colorant compounding method, coloring to black or gray by carbon or the like is preferable from the viewpoint of light impermeability due to light absorption, but is not limited thereto.For example, red or green, blue or a mixed color thereof may be appropriately used. It can also be colored in various colors.

In the above, a transparent adhesive layer 17 can be used in addition to the light absorbing layer 12 as shown in FIG. 3 for the purpose of fixing the spherical lens and improving the fixing force. In the illustrated example, the spherical lens 11 is fixed via an overlapping layer of the light absorbing layer 12 and the transparent adhesive layer 17. The transparent adhesive layer can be formed from the above-described film-forming components and the like, and the overlapping layer can be formed by a method in which the transparent adhesive layer and the light absorbing layer are overcoated according to the above. Arrangement positions of the transparent adhesive layer and the light absorbing layer in the superposed layer are arbitrary.

The light diffusion layer provided on one side of the flat lens is
For the purpose of widening the viewing angle, in the present invention, the light diffusion characteristics are formed so as to have anisotropic characteristics, in particular, to exhibit different light diffusion characteristics between one direction and a direction orthogonal thereto. Thereby, as shown in FIG. 5, for example, the transmitted light is diffused at a large angle in the horizontal (left / right) direction and hardly diffused in the vertical (up / down) direction through the light diffusion layer, thereby giving a characteristic that the transmitted light is not visible. It is possible to control and project the image light in the direction visible to the viewer in the front and left and right directions by suppressing the loss of diffusion of the image light in the direction not visible to the viewer, and to increase the brightness in the front and left and right directions. Excellent display can be achieved.

The light diffusion layer having anisotropic light diffusion characteristics is, for example, a surface hologram in which the diffusion directivity of transmitted light is controlled via fine irregularities formed on the surface, or a light diffusion layer which changes the refractive index throughout the bulk to transmit light. Holograms exhibiting anisotropy of light diffusion characteristics, such as volume holograms with controlled diffusion directivity of light, or a large number of fine linear projections or grooves formed on one or both of the surface and inside, and the projections and grooves However, the present invention can be obtained as a device having anisotropic diffusion of transmitted light through the substrate (JP-A-8-297202), but is not limited thereto.

Therefore, the light diffusion layer has an anisotropic light diffusion characteristic based on the diffusion structure imparted to the surface 14 as illustrated in FIG. 1, or has an internal structure or a structure based on both the surface and the internal structure. An appropriate material such as one exhibiting anisotropic light diffusion characteristics may be used. The thickness of the light diffusion layer can be appropriately determined according to its diffusion characteristics and the like. Some of the above-mentioned surface holograms can be formed as a thin surface layer in close contact with a predetermined surface, but are generally 5 mm or less, preferably 1 μm to 3 mm, particularly 5 μm.
The thickness is from μm to 1 mm.

The above-mentioned hologram can be formed by, for example, a photoresist, and there are commercially available holograms such as an elliptical light diffusion sheet (manufactured by Physical Optics). Further, the light diffusion layer having a large number of fine linear projections can be formed of the polymers or resins exemplified in the light absorption layer.

The flat type lens according to the present invention may have any form as long as it has a lens layer on one side and a light diffusion layer on the other side. Therefore, the lens layer and the light diffusion layer are in close contact with each other as in the case where the lens layer is formed by bonding and fixing the spherical lens 11 to one side of the light diffusion plate 13 via the adhesive light absorption layer 12 or the like illustrated in FIG. 2 or 3, between the lens layer and the light diffusing layer, such as a light transmitting substrate 15 having a lens layer on one side and a light diffusing layer on the other side. A configuration in which an intermediate layer is interposed may be used.

As the light-transmitting substrate, an appropriate one made of the polymers, resins, glass, or the like exemplified in the light-absorbing layer can be used. In particular, a material having excellent transmittance of image light and the like can be preferably used, but a translucent material or the like may be used as long as it has a light transmittance. The thickness of the light-transmitting substrate can be appropriately determined, but is generally 5 mm or less, particularly 10 μm to 3 mm, particularly 50 μm to 1 mm from the viewpoint of strength and the like.

When an intermediate layer such as a light-transmitting substrate is used for forming a planar lens, the lens layer and the light diffusing layer can be directly attached to the intermediate layer, or can be bonded via an adhesive layer. You can also. The adhesive layer can be formed of an appropriate adhesive such as an acrylic or rubber-based adhesive or a hot-melt adhesive such as a hot-melt adhesive, particularly, one having excellent transparency and weather resistance. However, a pressure-sensitive adhesive layer is preferable from the viewpoint of easy adhesion.

In the above description, the spherical lens, especially the exposed portion of the light absorbing layer, has a lower refractive index than the spherical lens as illustrated in FIG. 3 for the purpose of improving the image brightness by suppressing the reflection of the projected image light. The overcoat 18 can be made of a transparent material having a low refractive index, especially 0.05 to 0.7. As the transparent material, an appropriate material such as polymers or resins exemplified in the above light absorbing layer can be used,
The overcoat can be formed by an appropriate coating method such as a gravure method.

The flat lens according to the present invention can be used, for example, as a magnifying screen of a projection display device, a viewing angle widening plate of various display devices such as a liquid crystal system, a plasma system, and an electroluminescence system, and a light source such as a backlight for a liquid crystal or an illumination light source. Can be used for various purposes according to the related art, such as a diffusion plate.

FIG. 6 shows an example in which the rear projection display device is used as a transmission type enlarged screen. Reference numeral 3 denotes a screen, which comprises a flat lens 1 and a Fresnel lens 2 arranged on the lens layer side as shown in FIG. Reference numeral 6 denotes a housing.

According to the above, the image light L projected from the projection optical system 4 is reflected via the mirror 5 and enters the screen 3. The incident image light L is first collimated by the Fresnel lens 2 as illustrated in FIG. 4, is incident on the lens layer, is refracted through each spherical lens 11, and becomes an enlarged light beam. The image light incident on the portion is absorbed and removed by the light absorbing layer 12.

The image light, which has been enlarged by the spherical lens, passes through a light-transmitting base material 15 as required, reaches a light diffusion layer 16, and has a large angle in the vertical direction in FIG. In the direction perpendicular to the surface of the paper, and is transmitted without being substantially diffused.

As a result, an anisotropic diffusion that is wide in the horizontal direction and narrow in the vertical direction is achieved when viewed vertically with the vertical direction as the horizontal direction and the vertical direction as the front and back sides of the paper surface, Loss light that can be visually recognized at a large viewing angle and is not visually recognized in the vertical direction is reduced, and good visibility with excellent brightness and contrast is achieved.

[0031]

EXAMPLES Example 1 Polyester (Toyobo Co., Byron 200) 100
Part (parts by weight, hereinafter the same) and a mixed solution of 6 parts of black carbon are coated on one side of a PET substrate having a thickness of 250 μm with a knife coater and dried to form a light absorbing layer having a thickness of 10 μm. Glass beads having an average particle size of 50 μm and a refractive index of 1.70 are arranged in a single layer with almost no gap, and are placed at 120 ° C. and 3 kgf.
After embedding glass beads by hot pressing under the condition of / cm ² for 10 minutes, cooling the glass beads to room temperature, and then forming an elliptical light diffusion sheet (manufactured by Physical Optics) having a surface hologram formed on the other surface of the PET substrate. A light diffusing layer having anisotropic light diffusing characteristics was pressure-bonded with the surface hologram surface outside through an acrylic pressure-sensitive adhesive layer to obtain a flat lens.

Example 2 A 200 μm-thick poly (methyl methacrylate) sheet was applied to a light-diffusing layer at 150 ° C. and 20 kgf / cm ² through a mold.
Example 1 was formed by pressing a sheet in which isosceles prisms having a base (width) of 70 μm and an apex angle of 90 ° were arranged in a stripe shape by hot pressing for 0 second, with the prism surface facing outward. A flat lens was obtained in accordance with the following.

Example 3 Polyester (manufactured by Toyobo Co., Ltd., Vylonal MD1200) was coated on one surface of a polycarbonate substrate having a thickness of 150 μm.
Is coated with a gravure coater and dried to form a transparent adhesive layer having a thickness of 4 μm.
00) A mixture of 100 parts and 10 parts of black carbon was applied by a gravure coater and dried to form a 6 μm-thick light absorbing layer, on which an average particle diameter of 50 μm and a refractive index of 1.5 were formed.
A flat lens was obtained in the same manner as in Example 2 except that the glass beads of No. 2 were disposed in a single layer with almost no gap and embedded.

Example 4 Polyester (Byron 20) was applied to the exposed portions of the glass beads.
0) is coated with a gravure coater and dried to a thickness of 6 μm.
A flat lens was obtained in the same manner as in Example 1 except that the overcoat was formed.

Comparative Example 1 A flat lens was obtained in the same manner as in Example 1 except that no light diffusion layer was provided.

Comparative Example 2 A commercially available lenticular lens was used.

Evaluation Test A flat projection lens or a lenticular lens obtained in each of Examples and Comparative Examples was used to form a screen in combination with a Fresnel lens, and this was used as a transmissive magnifying screen and a rear projection display device according to FIG. Was formed, and the obtained image was evaluated. The results are shown in the following table.

The evaluation was based on the case where the lenticular lens of Comparative Example 2 was used. In the table, ○ means performance exceeding the reference (Comparative Example 2), and △ means performance equivalent to the reference.

From the table, Examples 1 to 4 and Comparative Example 1 are superior to Comparative Example 2 in overall performance.
It can be seen that is superior to Comparative Example 1 in the front luminance and the viewing angle in the horizontal direction. The front luminance was the best in Example 4.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of an embodiment.

FIG. 2 is an explanatory sectional view of another embodiment.

FIG. 3 is an explanatory sectional view of still another embodiment.

FIG. 4 is an explanatory view of a screen example.

FIG. 5 is a graph showing diffusion characteristics of a light diffusion layer.

FIG. 6 is an explanatory diagram of an example of a rear projection display device.

[Explanation of symbols]

 1: Planar lens 11: Spherical lens 12: Light transmitting substrate 13, 16: Light absorbing layer 15: Light transmitting substrate 17: Transparent adhesive layer 18: Overcoat

Claims (6)

[Claims] 1. A lens layer having a single layer arrangement of a number of spherical lenses fixed by a light absorbing layer thinner than the lens thickness on one side, and a light layer having anisotropic light diffusion characteristics on the other side. A planar lens having a diffusion layer. 2. The device according to claim 1, wherein the lens layer and the light diffusion layer are supported via a light-transmitting substrate, and the light diffusion layer exhibits different light diffusion characteristics in one direction and a direction orthogonal thereto. Is a planar lens. 3. The method according to claim 1, wherein the light-diffusing layer has a hologram exhibiting anisotropy of light-diffusion characteristics, or has a plurality of fine linear projections or grooves on one or both of the surface and the inside. A flat lens. 4. The flat lens according to claim 1, wherein the light diffusion layer is subjected to close contact treatment via an adhesive layer. 5. The flat lens according to claim 1, wherein the light absorbing layer is formed of a colored layer superimposed on the transparent adhesive layer. 6. A flat lens according to claim 1, wherein the exposed portion of the spherical lens from the light absorbing layer is overcoated with a transparent material having a lower refractive index than the lens.