JP2004029502A - Transmission type screen and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission type screen and a method of manufacturing the same for eliminating a gap between at least two lens sheets constituting the transmission type screen to realize an image of high quality free from blur and distortion. <P>SOLUTION: The transmission type screen is provided with: a lenticular lens sheet consisting of cylindrical lens groups arranged in parallel in the horizontal direction; and a Fresnel lens sheet. The lens parts are opposed to each other. In the method of manufacturing the transmission type screen, a bend having curvature of an aspherical surface shape is given to at least a part in the vicinity of the center part of at least one of the lenticular lens sheet and the Fresnel lens sheet so as to project toward the other lens sheet. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission screen used for a projection type projection television or the like.
[0002]
[Prior art]
Conventionally, in a rear projection television, brightness and a wide viewing angle have been mainly required.
[0003]
As a transmissive screen used for a rear projection television, a screen having a wide viewing angle, high contrast, little glare, no moiré, no stray light, no blur, and no distortion is required.
[0004]
A wide viewing angle gives the observer a wider viewable area of the image, a higher contrast results in a higher visibility of the image, a lower glare results in less fatigue of the observer's eyes, and an image shows less moiré, stray light, blur and distortion. This leads to improved quality.
[0005]
As one of means for expanding the viewing angle, there is a method of expanding image light in a horizontal direction or a vertical direction using a lenticular lens sheet in which cylindrical lens groups are arranged in parallel.
[0006]
Further, by providing a light diffusing material or the like in any layer constituting a screen such as a substrate or a lens, a method of isotropically spreading image light is adopted.
[0007]
In order to improve the contrast, for example, a lenticular lens sheet is provided with a light-shielding layer to increase the selectivity of image light, or a layer or a portion that absorbs visible light is provided to suppress external light reflection. Used. At this time, it is important to take a method of minimizing the reduction in light transmittance of the screen.
[0008]
It is known that glare is reduced by the concentration gradient of the light diffusion material in the light diffusion layer, the concentration difference between the light diffusion layers, and the like.
[0009]
Moiré is an interference fringe resulting from each combination of a projection pixel pitch, a Fresnel lens pitch, and a lenticular lens pitch. Therefore, the problem can be eliminated or reduced by setting the respective optimal pitches.
[0010]
The blur and distortion of the image are mainly caused by the shape distortion of the lens sheet itself and the gap between the lens sheets generated when the lenticular lens sheet and the Fresnel lens sheet are mounted on the housing.
[0011]
The shape distortion of the lens sheet is generally considered to be caused by temperature unevenness or stress unevenness when the base material is formed, and is eliminated by using a special forming method or performing a heat treatment (annealing) after the forming. Or can be reduced.
[0012]
As a method of reducing the gap between the lens sheets, a method of giving a warp to one or both of the lenticular lens sheet and the Fresnel lens sheet is known.
As a method for imparting the warp, a method of forming a convex shape on each lens sheet side and contacting them near the center, or a method of making the convex directions the same and appropriately changing the curvatures of each other Various proposals have been made.
[0013]
However, when the size of the lens sheet is increased or the thickness of the base material of the lens sheet is reduced, as in the related art, only a warp is given, or an arc-shaped having a constant radius of curvature. It is difficult to eliminate the gap between the lens sheets to the extent that the shape is given. Further, in a severe temperature and humidity environment, the gap between the lens sheets becomes larger due to thermal expansion and contraction of the lens sheets.
[0014]
Furthermore, in order to cope with the recent high definition television (HDTV), it is essential to reduce the gap between the lens sheets more than ever.
[0015]
[Problems to be solved by the invention]
The present invention has been made in view of the above technical background, and a lenticular lens sheet or a microlens sheet, and a Fresnel lens sheet and a transmission type screen in which the lens surfaces are in close contact with each other so as to face each other. It is an object of the present invention to provide a transmission screen capable of eliminating a gap between two lens sheets and realizing a high-quality image free from blur and distortion.
[0016]
[Means for Solving the Problems]
According to the present invention, in order to achieve the above object, an invention according to claim 1 includes at least a lenticular lens sheet including a group of cylindrical lenses arranged in a horizontal direction and a Fresnel lens sheet, and the lens units of In a transmissive screen having a configuration in which they are arranged facing each other,
At least one of the lenticular lens sheet and the Fresnel lens sheet is provided with a curvature having an aspherical curvature at least in the vicinity of the central portion so as to be convex toward the other lens sheet. It is a transmission screen.
[0017]
According to a second aspect of the invention, there is provided a transmission screen including a microlens sheet in which unit convex lenses are two-dimensionally arranged substantially in a matrix, and a Fresnel lens, wherein the lens units are arranged to face each other.
At least one of the micro lens sheet and the Fresnel lens sheet is provided with a warp having an aspherical curvature at least in the vicinity of the central portion so as to be convex toward the other lens sheet. It is a transmission screen.
[0018]
According to a third aspect of the present invention, in the transmission screen according to the first or second aspect, the aspheric shape is a parabolic shape.
[0019]
According to a fourth aspect of the present invention, in the transmission screen according to any one of the first to third aspects, a peripheral portion of the lens sheet except for a portion near a central portion has no curvature.
[0020]
The invention according to claim 5 is the transmissive screen according to any one of claims 1 to 4, wherein the warpage is at least one of a long side and a short side of a lenticular lens sheet or a Fresnel lens sheet. It is characterized by being formed in.
[0021]
The invention according to claim 6 is that, on a mold having an aspherical concave portion in the vicinity of the central portion,
At least one of a lenticular lens sheet, a Fresnel lens sheet, and a microlens sheet is placed so that its lens surface faces the concave portion, and a molding die having a convex portion having a shape fitted with the concave portion is formed. By hot pressing the lens sheet,
A method of manufacturing a transmissive screen, comprising a step of forming an aspherical warp in which a lens portion side is convex near a central portion of the lens sheet.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional view showing an example of the configuration of the transmission screen of the present invention. The transmissive screen 11 includes a Fresnel lens sheet 13 having a function of emitting the projection light from the projector 12 as substantially parallel light, and a cylindrical lens group which receives the light emitted from the Fresnel lens sheet 13 and is arranged in the vertical direction. A lenticular lens sheet 14 (a lens surface shape is not shown) having a function of spreading the substantially parallel light in the horizontal direction and emitting the light in the horizontal direction, wherein the lenticular lens sheet 14 is disposed on the viewer side. 14 shows an example in which a warp having a parabolic curvature protruding toward the lens is provided on the long side only in the vicinity of the central portion of No. 14.
[0023]
Of course, the transmission type screen of the present invention is not limited to the above-described configuration, and at least a portion near the central portion of at least one of the lenticular lens sheet and the Fresnel lens sheet or both lens sheets has a convex side. A warp having an aspherical curvature can be provided. Further, it can be provided on the short side of the lens sheet. The side to be warped and the amount of warpage vary depending on the size and thickness of the sheet and the use condition.
[0024]
The Fresnel lens sheet 13 used in the present invention is formed by a press method, a casting method, or the like. In the pressing method and the casting method, the lens portion and the base portion are made of the same material, and a thermoplastic resin such as an acrylic resin, a polycarbonate resin, a styrene resin, and an acrylic / styrene copolymer resin can be used. Alternatively, an ionizing radiation resin such as an ultraviolet curable resin (UV resin) or an electron beam curable resin is applied or injected onto the uneven surface of the stamper, and a resin sheet serving as a base material is placed thereon, and after the curing process, the stamper is used. There is a method of releasing the mold. As the ionizing radiation resin, a resin having good mold releasability at the time of photocuring, excellent light resistance when formed into a lens, and having a high lens hardness is selected.
[0025]
The lenticular lens sheet 14 composed of a group of cylindrical lenses used in the present invention can be integrally molded by using a stamper or the like when extruding and molding a resin sheet. In this case, the material is a material of the resin sheet, for example, an acrylic-based material. It is the same material as thermoplastic resin such as resin, polycarbonate resin, styrene resin, acrylic / styrene copolymer resin, etc., and at the time of the extrusion molding, a light diffusing material, for example, an inorganic material such as alumina, silica, etc. It is also possible to knead in advance an acrylic resin, a styrene resin, a polycarbonate resin, and an acrylic / styrene copolymer resin.
[0026]
The cylindrical lens group is formed by applying or injecting an ionizing radiation resin such as an ultraviolet curable resin (UV resin) or an electron beam curable resin onto the uneven surface of a stamper, a casting method, or a stamper, and becomes a base material thereon. It can also be obtained by placing a resin sheet, releasing the resin from the stamper after curing treatment. As the ionizing radiation resin, a resin having good mold releasability at the time of photocuring, excellent light resistance when formed into a lens, and having a high lens hardness is selected.
[0027]
The method of imparting the warp can be achieved by, for example, giving a difference in temperature and a difference in cooling rate between the upper surface and the lower surface of the resin sheet when the resin sheet is extruded. In this case, it is often performed simultaneously with the molding of the cylindrical lens group.
[0028]
FIG. 2 is a schematic explanatory view for explaining a method of imparting a warp to a lenticular lens sheet and a Fresnel lens sheet constituting a transmission screen of the present invention by using a warping mold.
At least one of the lenticular lens sheet and the Fresnel lens sheet is warped to have a convex aspherical curvature on the lens side at least in the vicinity of the central portion of the lens sheet using a warping mold 22. Can be formed by a hot press molding method having
The lenticular lens sheet or the Fresnel lens sheet may be sandwiched between a pair of warping molds under appropriate temperature conditions and time conditions, or may be arranged in one warping mold.
[0029]
The warp shape of the lens sheet largely depends on the shape of the warp mold. Therefore, the shape of the warp type must be designed based on the desired warp shape.
[0030]
The warp mold is preferably as rigid as possible in that it is for imparting a shape, and it is preferable to use a metal mold because it is easy to work into a desired shape. , But is not limited to this.
[0031]
It is preferable that the warping is performed under a constant temperature and humidity condition. It is also possible to warp a plurality of lens sheets at once. If there is a problem such as a flaw or heat fusion of the lens sheet, it is necessary to provide a slip sheet or a cushioning material between the warp mold and the lens sheet or between the lens sheets.
[0032]
Further, a light diffusing material can be used as a member constituting the transmission screen of the present invention. As the light diffusing agent, an inorganic resin such as alumina and silica, and an organic resin such as an acrylic resin, a styrene resin, a polycarbonate resin, and an acrylic / styrene copolymer resin are preferable. Light diffusion taking into account optical properties such as transmittance, diffusion transmittance, refractive index difference from base resin, surface gloss, dispersibility when molded as a light diffusion plate, brittleness when molded, etc. By selecting the agent, a desired resin sheet can be obtained.
[0033]
【Example】
Hereinafter, examples of the present invention will be described more specifically.
A lenticular lens sheet having a length and width of 650 mm × 1150 mm and a thickness of 1 mm, in which an arc-shaped warp having a radius of curvature of 1000 mm is applied to the long side, and a parabolic warp is applied to the long side as a whole. (2) was manufactured using a warp mold designed to have the same amount of warp for each. The amount of warpage referred to here is determined by measuring the distance from a straight line connecting both ends of the warped side to the side where the distance is maximum. The warpage was imparted by holding both in (1) and (2) in a room at 80 ° C. for 12 hours in a state sandwiched by a warp mold. The amount of warpage was about 150 mm.
[0034]
The lenticular lens sheets (1) and (2) produced as described above were combined with a separately prepared circular Fresnel lens sheet (3) having a length and width of 650 mm × 1150 mm and a thickness of 3 mm, respectively, from (1) and (3). And a transmission screen (5) composed of (2) and (3). The transmissive screens (4) and (5) described above were each set in a housing, and the adhesion between the lenticular lens sheet and the Fresnel lens sheet was evaluated based on the adhesion evaluation method described below. In this example, a circular Fresnel lens sheet (3) having a short side with a warpage of 5 mm was used.
[0035]
[Adhesion evaluation method]
The measurement was performed by visually observing the entire difference in reflected light intensity of external light between the lenticular lens sheet and the Fresnel lens sheet.
[0036]
As a result, in the case where the lenticular lens sheet (1) was used, two columnar floats which spread vertically at a position of about 450 mm left and right from the center occurred (see FIG. 3). When the lenticular lens sheet (2) was used, no floating was observed over the entire surface, and good adhesion was obtained.
[0037]
【The invention's effect】
According to the present invention, a lenticular lens sheet or a micro lens sheet, and at least a portion near a central portion of at least one of the Fresnel lens sheets, the curvature of the aspheric shape so as to be convex toward the other lens sheet side. By providing the warpage, the gap between the two lens sheets of the transmission screen in which the lenticular lens sheet or the micro lens sheet and the Fresnel lens sheet are combined in close contact with each other so that the lens surfaces are opposed to each other is provided. Thus, it is possible to provide a transmission screen capable of realizing a high-quality image without blur or distortion.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an example of the configuration of a transmission screen of the present invention.
FIG. 2 is a schematic explanatory view for explaining a method of applying a warp to a lenticular lens sheet and a Fresnel lens sheet constituting a transmission screen of the present invention by using a warping mold.
FIG. 3 is a schematic explanatory diagram for explaining poor adhesion between a lenticular lens sheet and a Fresnel lens sheet that constitute a conventional transmission screen.
[Explanation of symbols]
11 ... Transmissive Screen 12 ... Light Source 13 ... Fresnel Lens Sheet 14 ... Lenticular Lens Sheet 21 ... Pressure Cylinder 22 ... Warp Type 31 ... Transmissive Screen 32 ... Case 33: poor adhesion part

Claims (6)

At least, a lenticular lens sheet composed of a group of cylindrical lenses arranged in parallel in the horizontal direction, and a Fresnel lens sheet, a transmission screen having a configuration in which the lens units are arranged to face each other,
At least one of the lenticular lens sheet and the Fresnel lens sheet is provided with a curvature having an aspherical curvature at least in the vicinity of the central portion so as to be convex toward the other lens sheet. And a transmissive screen. In a transmission screen having a configuration in which a microlens sheet in which unit convex lenses are two-dimensionally arranged substantially in a matrix, and a Fresnel lens, the lens units are arranged to face each other.
At least one of the micro lens sheet and the Fresnel lens sheet is provided with a warp having an aspherical curvature at least in the vicinity of the central portion so as to be convex toward the other lens sheet. And a transmissive screen. 3. The transmission screen according to claim 1, wherein the aspheric shape is a parabolic shape. The transmissive screen according to any one of claims 1 to 3, wherein a peripheral portion of the lens sheet except for a portion near a central portion has no curvature. The transmission screen according to claim 1, wherein the warp is formed on at least one of a long side and a short side of a lenticular lens sheet or a Fresnel lens sheet. On a mold having an aspherical concave portion near the center,
At least one of a lenticular lens sheet, a Fresnel lens sheet, and a microlens sheet is placed so that its lens surface faces the concave portion, and a molding die having a convex portion having a shape fitted with the concave portion is formed. By hot pressing the lens sheet,
A method of manufacturing a transmission screen, comprising a step of forming an aspherical warpage in which a lens portion side is convex near a central portion of the lens sheet.

Images