JP2007225800A - Transmission type screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission type screen capable of preventing contact wear between a fresnel lens sheet and a lenticular lens sheet and preventing various failures caused by the contact wear. <P>SOLUTION: The transmission type screen includes the lenticular lens sheet 30 including a lens, a prism and an optical diffusion element such as a diffusing material, and the fresnel lens sheet 20 not including the optical diffusion element. A gap (d) between the fresnel lens sheet 20 and the lenticular lens sheet 30 is held by a spacer 40 to be ≥10mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmissive screen used for a rear projection display such as a liquid crystal projection television and a display.

The transmissive screen is molded from a light diffusing plate (hereinafter referred to as a lenticular lens sheet for the sake of convenience), which has a lenticular lens or prism sheet as a basic structure, and an optical diffusing material, and a base material containing the optical diffusing material. The formed Fresnel lens sheet (hereinafter referred to as “Fresnel lens sheet”) is configured such that its end is integrally held by a tape or a holding mechanism (see, for example, Patent Documents 1 and 2).
Since this holding method can handle the transmission screen in an integrated manner, the advantage is that the handling is good.

The lenticular lens sheet and the Fresnel lens sheet constituting the transmission screen are installed so that the lens layer side of the lenticular lens sheet and the lens layer side of the Fresnel lens face each other.
The lenticular sheet of the lenticular lens sheet has a structure in which a lenticular layer, a photosensitive resin layer, a light shielding layer, an adhesive layer and a plate-like diffusion layer are laminated, and the lenticular layer is on the Fresnel lens side of the Fresnel lens sheet. The diffusion layer is arranged on the viewer side. Further, a hard coat layer is provided on the viewer-side surface of the diffusion layer as necessary for protecting the surface.

The lenticular layer of the lenticular lens sheet is composed of a plate-like diffusion layer (hereinafter referred to as a diffusion plate) and a lens layer provided on one side thereof. The lens layer is configured by, for example, arranging a large number of semi-cylindrical cylindrical lenses so that their length directions are parallel to each other and perpendicular to the length direction. A lenticular lens sheet can be obtained by laminating a film-like pressure-sensitive adhesive layer on this lens layer, further laminating a plate-like diffusion layer, and firmly integrating them.
In addition, the diffusion layer of the lenticular lens sheet is formed by mixing a diffusion material made of a plurality of glass beads in a matrix made of, for example, an acrylic plastic. A hard code layer is laminated and integrated on the surface of the diffusion layer as needed.

The Fresnel lens sheet is configured by laminating a Fresnel lens layer and a plate-like diffusion layer.
In general, the Fresnel lens layer has a cone-like prism array shape arranged concentrically. In addition, a plate-like diffusion layer (hereinafter referred to as a diffusion plate) is often used for the diffusion layer as in the case of the lenticular lens sheet. However, the optical diffusion characteristics of the diffusion plate are generally different from those of the lenticular lens sheet.

When the transmissive screen configured as described above is attached to a liquid crystal projector equipped with a projector and light is emitted from the projector, the light becomes a substantially parallel light through a Fresnel lens sheet. The light beam passes through the lenticular layer to give a predetermined light distribution angle, which is appropriately spread in the horizontal direction (horizontal direction) of the screen, and the viewing angle in this direction is controlled.
The light beam that has passed through the lenticular layer becomes a striped beam parallel to the length direction of the cylindrical lens, passes through the light-shielding layer, and then moderately acts in the vertical direction (vertical direction) of the screen due to the action of the diffusion layer. Diffuses and the viewing angle in this direction is controlled. In addition, the light shielding layer can improve the S / N ratio and provide an image with good contrast.
JP-A-5-273658 JP-A-6-317849

In the conventional transmission type screen as described above, since the Fresnel lens sheet and the lenticular lens sheet are held in contact with each other, “rubbing” occurs between them. For this reason, the constituent material of the lens sheet is scraped due to transportation and aging, resulting in “white powder” in which the scraped resin becomes powdery, or the prism function of the Fresnel lens is crushed and the lens function is partially impaired. There is a problem that a phenomenon such as “stain” or a scratch mark that the lens itself is scraped off occurs.
These phenomena are not only manifested in the form of degradation of the observed image, but are not manifested at the time of manufacture, but occur when the product is transported or used, so there is a limit to the prevention of expression within the production process. As a result, there is a problem that the product life of a projection television or the like is shortened, and that once it occurs, maintenance costs for recovery and repair are increased.
In addition, since a plurality of plates with slightly different thermal expansion coefficients are used in an integrated manner, there is a problem that warpage and distortion of the entire screen occur in a temperature change within a practical range (for example, about 0 ° C. to 60 ° C.).

  The present invention has been made to solve the above problems, and provides a transmission screen that can prevent various problems caused by contact wear by preventing the Fresnel lens sheet and the lenticular lens from being contact-weared. With the goal.

  In order to achieve the above object, a transmission screen according to the present invention includes a diffusion plate including an optical diffusion element such as a lens, a prism, and a diffusion material, and a Fresnel lens sheet including no optical diffusion element, and the diffusion plate And the Fresnel lens sheet are arranged to face each other with a predetermined gap.

According to the transmissive screen of the present invention, the diffuser plate and the Fresnel lens sheet are arranged to face each other with a predetermined gap in a non-contact manner, so that the diffuser plate and the Fresnel lens sheet may contact or rub against each other. This prevents the generation of white powder and compression deformation of the Fresnel lens sheet due to contact pressure, and also prevents the screen from warping due to thermal expansion and contraction by holding the diffusion plate and the Fresnel lens sheet alone. Can do.
In addition, according to the present invention, since the Fresnel lens sheet does not include an optical diffusion element, the diffusion plate and the Fresnel lens sheet including the optical diffusion element are generated without causing defocusing of a projected image due to light diffusion by the Fresnel lens. Can be installed in a non-contact manner.

The Fresnel lens sheet constituting the transmissive screen of the present invention does not include an optical diffusion layer in the base material layer, and is particularly clear.
Here, the state where the optical diffusion layer of the Fresnel lens sheet is not present means that an object or structure for causing an increase in the viewing angle is not included as an effect on the projection light from the projector, and more specifically, It shows that it does not contain fillers for the purpose of light dispersion / scattering / diffusion.

In addition, the material of the base layer can be used as long as it has practically satisfactory transmittance for transmitted light and mechanical strength. As the main plastic material, acrylic resin such as methacryl styrene resin can be used. Polycarbonate and the like can be widely used.
In addition to plastic, glass-based materials such as float glass, blue plate glass, BK7, etc. can be used.

  The gap between the two lens sheets constituting the transmissive screen, that is, the lenticular lens sheet corresponding to the diffusing plate and the Fresnel lens sheet is appropriately held by using a spacer holder or the like. This separation holding tool has the simplest configuration in which a simple plate-like member is sandwiched, but a method of holding the above-mentioned gap by clamping the separation plate material or a plurality of attachments on the housing side holding the transmission screen A method of providing a portion, for example, a groove is conceivable. However, the present invention is not limited to this, and it is only necessary to have a function capable of appropriately holding a gap between two lens sheets.

The material of the lens array layer such as a Fresnel lens sheet or a lenticular lens sheet is a material transparent to the image light wavelength such as glass or plastic, and can be used without any particular limitation on the material used for the optical member. In view of production efficiency, it is most preferable to use plastic.
Examples of the plastic include acrylic resins such as polymethyl methacrylate, polycarbonate, acrylic-styrene copolymers, styrene resins, and polyvinyl chloride. It is preferable to use a radiation curable resin such as an ultraviolet curable resin or an electron beam curable resin as a material for the lens layer that requires particularly fine processing.
As the radiation curable resin, for example, a composition in which a reaction diluent, a photopolymerization initiator, a photosensitizer, or the like is added to urethane (meth) acrylate and / or epoxy (meth) acrylate oligomer can be used.

The urethane (meth) acrylate oligomer is not particularly limited, and examples thereof include polyols such as ethylene glycol, 1,4 butanediol, neopentyl glycol, polycaprolactone polyol, polyester polyol, polycarbonate diol, and polytetramethylene glycol. , Hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylene isocyanate, and other polyisocyanates.
The epoxy (meth) acrylate oligomer is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, terminal glycidyl ether of bisphenol A type propylene oxide adduct, fluorene epoxy It can be obtained by reacting an epoxy resin such as a resin with (meth) acrylic acid.

  Further, in the present invention, by using a diffusion plate including an optical diffusion element such as a diffusion material as a lenticular lens sheet, existing production processes and materials can be used as they are, and production advantages are great, and The performance index as a screen, such as the resolution, can be easily set to the same level as that of the conventional product, and the disadvantage associated with the change of the method is hardly generated.

In the present invention, the gap between the diffusion plate and the Fresnel lens sheet is 10 mm or more. As a result of experimentally verifying the durability against deformation of the lens sheet such as temperature change, vibration, and touch by holding such a gap, the size of the lens sheet required for the TV set at present is from 40 inches. If the material is MS resin or PET resin under the condition of about 70 inches and the thickness of each lens sheet is 1 to 3 mm, a relatively rough and inexpensive installation method, for example, when separated by a spacer, etc. However, it was confirmed that the two lens sheets were not in contact with each other.
In addition, a sufficient effect was confirmed in an experiment in which the gap between the two lens sheets was 25 mm, and the light diffusivity of the Fresnel lens sheet was close to 0. It was also confirmed by experiments that the effect of distance on the image was minor. At the same time, it was confirmed by experiments that the effect of the separation distance due to these measures on the image was minor.

Further, in the present invention, by applying an antireflection coating on one side or both sides of the Fresnel lens sheet that does not include a diffusing element, a double image due to stray light in the Fresnel lens sheet that has not become apparent in a conventional transmission type screen. Thus, problems caused by reflection can be effectively prevented.
Further, in the conventional transmission type screen, stray light in the Fresnel lens sheet becomes a double image and may appear as noise in the projection image. One of the causes is the repeated reflection in the Fresnel lens, but in order to eliminate this, conventionally, there is a method of reducing the light intensity by repeatedly diffusing stray light by including a diffusing element in the Fresnel lens sheet. It is done.
In the present invention, if the Fresnel lens sheet contains a diffusing component, it causes blurring of the projected image. Therefore, an antireflection coating that realizes repeated reflection itself by reducing the reflectance is effective.
In addition to AR treatment with a dielectric multilayer film structure, anti-reflection coating can be applied to LR treatment of dielectric single layer film structure, AG treatment to roughen the interface, etc., coating, vapor deposition, or laminating processed sheets Such processing methods can be used, and can be combined as appropriate according to the needs of the product.

Further, in the present invention, the lenticular lens sheet and the Fresnel lens sheet constituting the transmission screen can be bonded with a spacer interposed therebetween, so that the spacer for holding the gap between both lens sheets may be one sheet, and the separation holding mechanism. For this reason, it is not necessary to secure a separate space, so that the separation holding mechanism can be easily and easily changed without adding another component.
In general, as a method for holding the diffusion plate and the Fresnel lens sheet apart, there are many methods using a mechanical holding mechanism on the housing side, but if a mechanism for holding the separation distance is incorporated in the housing, the thickness of the holding mechanism portion, Increases in cost and man-hours due to the addition of mechanisms are likely to be a problem.
In addition, in the configuration of the present invention, the flexure deformation of the Fresnel lens sheet, which has been a cause of defocusing in the past, has almost no effect on image quality because there is almost no light diffusivity of the Fresnel lens sheet. No need to consider. Along with this, in this method, a liquid crystal projection television set or the like can be configured by an extremely rough installation method.

Embodiments of the transmission screen according to the present invention will be described below with reference to FIGS.
FIG. 1 is a schematic cross-sectional view showing an example of a transmissive screen according to the present invention, and FIG. 2 is an explanatory diagram when an image is projected on the transmissive screen in the first embodiment.

1 and 2, the transmissive screen 10 has a Fresnel lens sheet 20 and a lenticular lens sheet 30, and the Fresnel lens sheet 20 and the lenticular lens sheet 30 facing each other with a predetermined gap d (for example, 10 mm or more). And a spacer 40 that is held in a separated state.
The Fresnel lens sheet 20 includes a Fresnel base layer 201 that does not include an optical diffuser and has a light diffusivity close to 0, and a concentric circle on the light emission side of the Fresnel base layer 201 (the side facing the lenticular lens sheet 30). And a Fresnel lens layer 202 having a cone-like prism array shape. In addition, the Fresnel lens in the Fresnel lens sheet 20 is designed as a transmission screen having a projection distance of about 700 mm and a size of 50 inches (aspect ratio 16: 9).

The lenticular lens sheet 30 includes a lenticular sheet layer 301 containing an optical diffusion material, and a semicircle formed on the light incident side of the lenticular substrate layer 301 (the side facing the Fresnel lens layer 202 of the Fresnel lens sheet 20). A lenticular lens layer 302 is formed by arranging a large number of columnar cylindrical lenses.
The lenticular lens sheet 30 is set to design parameters as described below.
That is, in the lenticular base material layer 301, the material was polyethylene terephthalate, and the thickness was 75 μm. In addition, the material of the lenticular lens layer 302 is UV photosensitive resin, and the lens has an aspherical shape with a pitch of 98 μm, an elliptical surface as a reference surface, and correction by higher order terms. Further, a chromalin film (trade name: manufactured by DuPont) having a thickness of 20 μm was used for the photosensitive resin layer.
Similarly to a conventional lenticular sheet, a horizontal viewing angle is given by a lenticular lens, and a vertical viewing angle is given by a diffusing material.
The spacer 40 serving as the gap holding means is made of a lightweight material such as foamed polystyrene, and the gap d between the Fresnel lens sheet 20 and the lenticular lens sheet 30 is set to 10 mm or more by adjusting the thickness thereof. Enabled to set.

  In the transmissive screen 10 thus configured, as shown in FIG. 2, when the light beam 501 is irradiated from the projector 50 onto the transmissive screen 10, the light beam 501 becomes a substantially parallel light beam by the Fresnel lens sheet 20. The light is emitted to the lens sheet 30 side. The light beam 502 is given a predetermined light distribution angle by passing through the lenticular lens sheet 30 and appropriately spreads in the left-right direction (horizontal direction) of the screen, and the viewing angle in this direction is controlled. The light beam that has passed through the lenticular lens sheet 30 becomes a striped light beam that is parallel to the length direction of the cylindrical lens, passes through the light shielding layer, and then is moderately applied in the vertical direction (vertical direction) of the screen by the action of the diffusion layer. The light beam diffuses into the light source, and the viewing angle in this direction is controlled.

In the transmissive screen 10 according to the first embodiment, when a method of displaying a point image or hatching from the projector 50 and confirming the image is taken, no blurring of the image is observed up to a gap of about 30 mm. Imaging was confirmed.
In addition, since the distortion of the image increases when the thickness of the spacer 40 exceeds 30 mm, it is difficult to use the existing projector as it is, but this phenomenon can be avoided by preparing a projector in which the distortion is corrected in advance. Is possible.

According to the transmission screen in the first embodiment, the spacer 40 forms the gap d of 10 mm or more between the Fresnel lens sheet 20 and the lenticular lens sheet 30, so that the screen can be pushed from one side. The Fresnel lens sheet 20 and the lenticular lens sheet 30 do not come into contact with each other even when deflected by gravity, and as a result, generation of stains and white powder can be prevented and thermal expansion and contraction are accompanied. Screen warpage can be prevented.
Further, according to the first embodiment, since the Fresnel lens sheet does not include an optical diffusing element, it is possible to eliminate the blur of the projected image accompanying the light diffusion of the Fresnel lens.

  In the first embodiment, when a thin spacer 40 is used, the separation distance between the lenticular lens sheet 30 and the Fresnel lens sheet 20 is insufficient, and there is a possibility that contact may occur due to vibration due to their elasticity. There is. In such a case, if the material of the base material constituting the lenticular lens sheet 30 and the Fresnel lens sheet 20 is made of a hard material such as glass, or the rigidity is increased by increasing the thickness, the above-described phenomenon is caused. Although it can be prevented, it is desirable that the distance is 10 mm or more when extending the conventional configuration (about 1 to 3 mm with a plastic sheet).

It is a schematic cross section which shows an example of the transmission type screen concerning this invention. It is explanatory drawing at the time of projecting an image | video on the transmission type screen in the present Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Transmission type screen, 20 ... Fresnel lens sheet, 30 ... Lenticular lens sheet, 40 ... Spacer, 50 ... Projector.

Claims (7)

  A diffusing plate including an optical diffusing element such as a lens, a prism, and a diffusing material; and a Fresnel lens sheet not including the optical diffusing element, wherein the diffusing plate and the Fresnel lens sheet are arranged to face each other with a predetermined gap. A transmissive screen characterized by that.   The transmission screen according to claim 1, wherein the diffusion plate is a lenticular lens sheet.   The transmission screen according to claim 1, wherein a gap between the diffusion plate and the Fresnel lens sheet is 10 mm or more.   The transmission screen according to claim 1 or 3, wherein an antireflection coating is applied to a surface of the Fresnel lens sheet.   4. The transmission screen according to claim 1, wherein a gap between the diffusion plate and the Fresnel lens sheet is held by a separation holding means.   The Fresnel lens sheet includes a Fresnel base material layer that does not include an optical diffusing material, and a Fresnel lens that forms a conical prism array formed concentrically on the side of the Fresnel base material layer that faces the lenticular lens sheet. The transmissive screen according to claim 1, comprising a layer. The lenticular lens sheet includes a lenticular lens layer including an optical diffusing material, and a plurality of semi-cylindrical cylindrical lenses formed on a side of the lenticular base layer facing the Fresnel lens sheet. The transmissive screen according to claim 2, comprising:

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