Reflection type screen and video display device

Abstract

To provide a reflection type screen which is easy for winding, can keep high flatness during usage, and hardly causes damage such as a folded mark and abrasion, and a video display device which includes the same, especially, a windable reflection type screen which is applicable to a video projection system called an ultrashort focus type having a short fucus distance, and a video display device having the same.SOLUTION: A reflection type screen includes: a lens layer in which a plurality of unit lenses having lens surfaces and non-lens surfaces crossing the lens surfaces are arrayed; a reflection layer which is formed in at least a part of the lens surface and reflects light; and a base material layer which is formed of a resin having light transmittance, is arranged on an observer side of the lens layer, and serves as a base material of the lens layer, has such flexibility as to be windable, and has tensile strength of 31 MPa or more and 43 MPa or less and bending strength of 45 MPa or more and 79 MPa or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a reflective screen and an image display device. [Background technology]

[0002] Conventionally, the use of short-focus projectors (image projection devices) that project image light onto a reflective screen from a close distance at a relatively large projection angle to achieve a large-screen display has become widespread, and various reflective screens compatible with these have been developed. In order to display the image light projected by such a short focal projector in a good condition, various reflective screens have been developed in which a reflective layer is formed on the surface of a lens layer having a Fresnel lens shape. In addition, conventionally, reflective screens have been known that are flexible and can be rolled up for storage when not in use, and reflective screens compatible with the above-mentioned short focus projectors have also been developed that are flexible enough to be rolled up for storage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-76523 A Summary of the Invention [Problem to be solved by the invention]

[0004] For a flexible reflective screen that can be rolled up, there is always a demand for ease of roll-up, i.e., the ability to roll up quickly with little force, and improved flatness of the screen when unrolled for use. In addition, for a flexible reflective screen that can be rolled up, there is also a demand for suppressing damage such as creases and scratches that occur in parts of the reflective screen due to repeated rolling and unrolling.

[0005] Furthermore, in image display devices using the ultra-short focus type image projection method that has become widespread in recent years, the image source and the screen are located close to each other, which tends to significantly increase image distortion, and high precision is required for the flatness of the screen. Also, screens used in the ultra-short focus type image projection method are widely known to have a Fresnel lens layer in which unit lenses are arranged and a reflective layer formed on the surface of the unit lenses in order to direct the image light in the front direction of the screen. However, when such a lens layer is provided, the thickness distribution of the lens layer becomes large within the screen surface, which causes bias in the stress when rolling up, making it difficult to realize an ultra-short focus type rollable screen.

[0006] The object of the present invention is to provide a reflective screen that is easy to roll up, can maintain a high degree of flatness during use, and is less susceptible to damage such as creases and scratches, and an image display device equipped with the same, in particular to provide a rollable reflective screen that is applicable to an image projection method known as an ultra-short focal length type, which has a short focal length, and an image display device equipped with the same. [Means for solving the problem]

[0007] The present invention solves the above problems by the following solving means. Note that, for ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present invention, but the present invention is not limited thereto. The first invention is a reflective screen (10) that displays an image by reflecting light projected from an image source, comprising: a lens layer (13) in which a plurality of unit lenses (131) are arranged, each unit lens (131) having a lens surface (132) and a non-lens surface (133) intersecting the lens surface; a reflective layer (14) that is formed on at least a part of the lens surface and reflects light; and a base layer (12) that is made of a light-transmitting resin, is placed on the viewer side of the lens layer, and serves as a base material for the lens layer; the reflective screen (10) has flexibility that allows it to be rolled up, and has a tensile strength of 31 MPa or more and 43 MPa or less, and a bending strength of 45 MPa or more and 79 MPa or less. A second invention is a reflective screen (10) characterized in that in the reflective screen of the first invention, the ratio Et / Eb of the tensile elastic modulus Et to the flexural elastic modulus Eb is 1.02 or more and 1.04 or less, and the Poisson's ratio is 0.37 or more and 0.39 or less. The third invention is a reflection-type screen according to the first or second invention, wherein the Charpy impact strength is 1.8 Kj / m 2 More than 3.5Kj / m 2 The present invention relates to a reflective screen (10) characterized in that: A fourth invention is a reflective screen (10) characterized in that in any one of the reflective screens of the first to third inventions, the base layer (12) has a light diffusion portion (121) containing a diffusion material that diffuses light in at least a part of its thickness direction. The fifth invention is a reflective screen (10) characterized in that in any one of the reflective screens from the first to fourth inventions, the base layer (12) is formed from styrene-butadiene copolymer resin (SBC resin). The sixth invention is a reflective screen (10) characterized in that in any one of the reflective screens from the first to fifth inventions, the base layer (12) has a colored portion (122) in at least a part of its thickness direction, the colored portion containing a coloring material having a light absorbing effect of absorbing a part of the incident light. A seventh invention is an image display device (1) comprising a reflective screen (10) according to any one of the first to sixth inventions, and an image source (LS) that projects image light onto the reflective screen. Effect of the Invention

[0008] According to the present invention, it is possible to provide a reflective screen that is easy to roll up, can maintain a high degree of flatness during use, and is less susceptible to damage such as creases and scratches, and an image display device equipped with the same. Also, according to the present invention, it is possible to provide a rollable reflective screen that is particularly applicable to an image projection method called an ultra-short focal length type, which has a short focal length, and an image display device equipped with the same. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an image display device 1 according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a layer structure of the screen 10 according to the embodiment. [Diagram 3] FIG. 2 is a diagram illustrating a lens layer 13 according to the embodiment. [Figure 4] 2 is a diagram showing how image light and external light incident on a screen 10 in an embodiment travel. [Diagram 5] FIG. 2 is a diagram illustrating a test piece 30A used for measuring tensile strength. [Figure 6] FIG. 1 is a table summarizing the numerical values ​​regarding the tensile strength, etc., and the evaluation of the ease of winding, etc., of the screens of Samples 1 to 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, etc. Note that each of the drawings shown below, including Fig. 1, is a schematic diagram, and the size and shape of each part are appropriately exaggerated to facilitate understanding. In this specification, terms specifying shapes or geometric conditions, such as parallel and orthogonal, are intended to include not only their strict meanings but also states that have a similar optical function and have an error that can be regarded as parallel or orthogonal. The numerical values ​​such as dimensions of each component and the names of materials described in this specification are merely examples of an embodiment, and are not limiting, and may be appropriately selected and used.

[0011] In addition, the terms plate, sheet, and the like are used in this specification, and in general, they are used in the order of thickness, plate, sheet, and film, and this specification follows suit. However, since there is no technical meaning behind such distinction, these terms can be used interchangeably as appropriate. In this specification, the screen surface refers to the planar direction of the screen when in use.

[0012] (Embodiment) Fig. 1 is a diagram showing an image display device 1 according to the present embodiment. Fig. 1(a) is a perspective view of the image display device 1, and Fig. 1(b) is a view of the image display device 1 as seen from the side (the +X side described later). The image display device 1 includes a screen 10, an image source LS, etc. The screen 10 of this embodiment is a reflective screen that reflects image light La projected from the image source LS and displays an image on its screen. The details of this screen 10 will be described later.

[0013] For ease of understanding, an XYZ Cartesian coordinate system is provided as appropriate in each of the following figures, including Fig. 1. In this coordinate system, the left-right direction of the screen of screen 10 is the X direction, the up-down direction of the screen is the Y direction, and the thickness direction of screen 10 is the Z direction. The screen of screen 10 is parallel to the XY plane, and the thickness direction of screen 10 (Z direction) is perpendicular to the screen of screen 10.

[0014] In the screen 10 of this embodiment, when in use, the screen (display area) is parallel to the XY plane, the up-down direction (Y direction) of the screen is vertical, and the left-right direction (X direction) of the screen is horizontal. The direction toward the right in the left-right direction as seen by an observer O positioned in front of the screen 10 is the +X direction, the direction toward the upper side in the up-down direction is the +Y direction, and the direction from the back side (rear side) toward the image source side (observer side) in the thickness direction is the +Z direction. Furthermore, in the following description, unless otherwise specified, the up-down direction, left-right direction, and thickness direction of the screen refer to the up-down direction (vertical direction), left-right direction (horizontal direction), and thickness direction (depth direction) of the screen 10 when it is in use, and are parallel to the Y direction, X direction, and Z direction, respectively.

[0015] The image source LS is an image projection device that projects the image light La onto the screen 10, and is, for example, an ultra-short focus projector. In the present embodiment, as an example, the image source LS uses a laser light source. When the image display device 1 is in use, and the screen (display area) of the screen 10 is viewed from the front (the normal direction of the screen surface), this image source LS is located in the center of the screen in the left-right direction (X direction) of the screen 10 and vertically below the screen of the screen 10 (the -Y side). The image source LS can project the image light La obliquely from a position that is much closer to the surface of the screen 10 in the depth direction (Z direction) of the image display device 1 than a conventional general-purpose projector. Therefore, compared to a conventional general-purpose projector, the image source LS has a shorter projection distance of the image light La to the screen 10 and a larger incidence angle at which the projected image light La is incident on the screen 10.

[0016] The screen 10 is a reflective screen that reflects the image light La projected by the image source LS toward the observer O to display the image. The image plane (display area) of the screen 10 is substantially rectangular when viewed from the observer O side in use, with the longer side extending in the left-right direction (X direction) of the screen. This screen 10 has flexibility that allows it to be rolled up, and when not in use it can be rolled up and stored in a predetermined box (not shown) or the like, and when in use it is unrolled and hung by a support member (not shown) or the like. Note that when in use, the screen 10 may be in a form in which, for example, at least two opposing sides are supported by a support member (not shown) or the like, and the flatness of the screen 10 is maintained.

[0017] The screen 10 has a large screen with a diagonal screen size of about 60 to 100 inches, and the aspect ratio of the screen is 16:9. However, the screen size is not limited to this, and may be, for example, about 40 inches or less, and the size and shape can be appropriately selected depending on the purpose of use, the environment of use, etc. In this embodiment, an example will be described in which the screen size of the screen 10 is 80 inches. The total thickness of the screen 10 is preferably 100 μm or more and 1400 μm or less, and more preferably 400 μm or more and 700 μm or less. If the total thickness of the screen 10 is smaller than this range, the desired optical performance may not be obtained. If the total thickness of the screen 10 is larger than this range, the flexibility may decrease, making it difficult to wind up the screen 10, or the screen 10 may be damaged when wound up.

[0018] Fig. 2 is a diagram showing the layer structure of the screen 10 of this embodiment. Fig. 2 shows an enlarged portion of a cross section that passes through point A (see Figs. 1(a) and (b)) which is the center of the screen (the geometric center of the screen) of the screen 10, is parallel to the vertical direction of the screen (Y direction), and is perpendicular to the screen surface (parallel to the Z direction). As shown in FIG. 2, the screen 10 comprises, in order from the image source side (+Z side), a surface layer 11, a base layer 12 (light diffusion layer 121, colored layer 122), a lens layer 13, and a reflective layer 14, which are laminated together.

[0019] The surface layer 11 is a layer provided on the viewer side (+Z side) of the base layer 12. The surface layer 11 of this embodiment forms the outermost surface of the screen 10 on the viewer side. The surface layer 11 of this embodiment has a hard coat function and an anti-glare function. This surface layer 11 is formed by applying an ionizing radiation curable resin such as an ultraviolet curable resin (e.g., urethane acrylate) having a hard coat function to the viewer-side surface of the base layer 12, and then transferring a fine uneven shape (matte shape) to the resin film surface and curing it, thereby forming a fine uneven shape on the surface. Therefore, the viewer-side surface of the surface layer 11 has a rough surface. In addition, the surface layer 11 is formed so that the thickness after forming the fine uneven shape is about 10 to 100 μm.

[0020] The surface layer 11 is not limited to the above examples, and may be provided with one or more appropriate functions such as anti-reflection function, anti-glare function, hard coat function, ultraviolet absorbing function, anti-soiling function, and anti-static function. In addition, the surface layer 11 may be a separate layer from the base material layer 12 and may be bonded to the base material layer 12 with an adhesive material or the like (not shown), or may be formed directly on the observer side (+Z side) of the base material layer 12.

[0021] The base layer 12 is a light-transmitting layer, and is a sheet-like member that serves as a base material for forming the lens layer 13. The surface layer 11 is integrally formed on the observer side (+Z side) of the base layer 12, and the lens layer 13 is integrally formed on the back side (-Z side). The base layer 12 has a light diffusion layer 121 containing a diffusing material that diffuses light, and a coloring layer 122 containing a coloring material such as a pigment or dye. The base layer 12 of this embodiment is formed by laminating the light diffusion layer 121 and the coloring layer 122 together by co-extrusion molding. However, this is not limited to this, and these layers may be formed separately and laminated together via a bonding layer (not shown) made of a light-transmitting adhesive or adhesive. Also, this bonding layer (not shown) may contain the diffusing material and the coloring material. In this embodiment, as shown in FIG. 2, in the base layer 12, the light diffusion layer 121 is located on the viewer side (+Z side), and the colored layer 122 is located on the back side (-Z side).

[0022] The light diffusion layer 121 is a layer that uses a resin having optical transparency as a base material and contains a diffusing material that diffuses light. The light diffusion layer 121 has the functions of widening the viewing angle and improving the in-plane uniformity of brightness. The resin that is the base material of the light diffusion layer 121 will be described in detail later.

[0023] The diffusion material contained in the light diffusion layer 121 is preferably a resin particle such as an acrylic, epoxy, or silicone particle, or an inorganic particle. The diffusion material may be a combination of an inorganic diffusion material and an organic diffusion material. The diffusion material is preferably substantially spherical and has an average particle size of about 1 to 50 μm, and more preferably about 5 to 30 μm. The thickness of the light diffusion layer 121 depends on the screen size of the screen 10, but is preferably about 25 to 400 μm, and more preferably 125 to 250 μm. The light diffusion layer 121 desirably has a haze value in the range of 1 to 50%.

[0024] The colored layer 122 is a layer that is colored with a dark colored material such as black so as to have a predetermined light transmittance. The colored layer 122 has the function of improving the contrast of an image by absorbing unnecessary external light such as illumination light that is incident on the screen 10 and reducing the black luminance of the displayed image. As the coloring material for the colored layer 122, dyes or pigments of dark colors such as gray or black, or metal salts such as carbon black, graphite, and black iron oxide are preferably used. The resin that is the base material of the colored layer 122 will be described in detail later. Note that the resin that is the base material of the colored layer 122 is preferably the same resin as the resin that is the base material of the light diffusion layer 121 described above. The thickness of the colored layer 122 depends on the screen size of the screen 10, but is preferably about 25 to 400 μm, and more preferably 125 to 250 μm.

[0025] Fig. 3 is a diagram illustrating the lens layer 13 of this embodiment. Fig. 3(a) shows only the lens layer 13 observed from the front direction on the rear side (-Z side). Fig. 3(b) shows a further enlarged view of a portion of the cross section of the screen 10 shown in Fig. 2, and for ease of understanding, only the lens layer 13 and the reflective layer 14 are shown. The lens layer 13 is a light-transmitting layer provided on the back side (-Z side) of the base layer 12, and as shown in FIG. 3(a), the back side surface has a circular Fresnel lens shape in which unit lenses 131 are arranged on concentric circles.

[0026] This circular Fresnel lens shape has a so-called offset structure in which point C, which is its optical center (Fresnel center), is outside the screen (display area) of the screen 10 and is located below (-Y side) of the screen 10 when the screen 10 is in use. Therefore, as shown in Fig. 3(a), when the lens layer 13 is viewed from the front direction of the back side (-Z side), unit lenses 131 each having a partial shape of a perfect circle (arc shape) are observed to be arranged.

[0027] As shown in Figures 2 and 3(b), the unit lenses 131 are parallel to the direction perpendicular to the screen surface (Z direction), and the cross-sectional shape in a cross section parallel to the arrangement direction of the unit lenses 131 is a triangular shape that is convex toward the back side (-Z side). In the cross section shown in Fig. 3(b), unit lens 131 has lens surface 132 and non-lens surface 133 that intersects with lens surface 132 at vertex t2. In the cross section shown in Fig. 3(b), unit lens 131 has lens surface 132 located vertically above (on the +Y side of) non-lens surface 133, with vertex t2 in between.

[0028] 3(b), in unit lens 131, the angle that lens surface 132 makes with a plane parallel to the screen surface is α, and the angle that non-lens surface 133 makes with a plane parallel to the screen surface is β. This angle β is larger than angle α (β>α). The arrangement pitch of the unit lenses 131 is P, and the lens height of the unit lenses 131 (the dimension in the thickness direction of the screen from the vertex t2 to the point t1 that is the bottom between adjacent unit lenses 131) is h.

[0029] 2, 3(b) and the like show the arrangement pitch P, angles α, β, and the like of the unit lenses 131 as being constant in the arrangement direction of the unit lenses 131. However, in reality, the arrangement pitch P of the unit lenses 131 of this embodiment is constant, but the angle α gradually increases with distance from point C, which is the Fresnel center, in the arrangement direction of the unit lenses 131. In this embodiment, the unit lenses 131 have an arrangement pitch P2=100 μm, an angle α of about 4° at the bottom center of the screen 10 in the horizontal direction, an angle α of about 20° at the top center of the screen in the horizontal direction, and an angle β of 90°.

[0030] However, the screen 10 is not limited to this, and may have a configuration in which the arrangement pitch P changes gradually or stepwise along the arrangement direction of the unit lenses 131. In addition, the array pitch P and angles α, β, etc. can be changed appropriately depending on the size of the pixel of the image source LS that projects the image light La, the projection angle of the image source LS (the angle of incidence of the image light La on the screen surface of the screen 10), the screen size of the screen 10, the refractive index of each layer, etc.

[0031] The lens layer 13 of the present embodiment is formed of an ultraviolet curable resin such as urethane acrylate, epoxy acrylate, etc. However, the lens layer 13 may be formed of other ionizing radiation curable resins such as an electron beam curable resin. This lens layer 13 can be formed, for example, by ultraviolet ray molding or the like on the surface that will be the back side (-Z side) of the base layer 12. Note that the method for forming the lens layer 13 may be appropriately selected depending on the resin or the like that is the material of the lens layer 13, and is not limited thereto.

[0032] The reflective layer 14 is a layer that has the function of reflecting incident light. The reflective layer 14 is formed on at least a part of the lens surface 132. As shown in Fig. 2 and Fig. 3(b), the reflective layer 14 of this embodiment is formed on the surface of the unit lens 131, that is, on the lens surface 132 and the non-lens surface 133. However, this is not limiting, and the reflective layer 14 may be formed only on the lens surface 132 and not on the non-lens surface 133. The reflective layer 14 is made of a metal having high light reflectivity, such as aluminum, silver, or nickel, and has a thickness of about 800 Å. The reflective layer 14 of this embodiment is formed by vapor deposition of aluminum.

[0033] Furthermore, the reflective layer 14 is not limited to this, and may be formed, for example, by sputtering a metal having high light reflectivity, transferring a metal foil, applying paint containing a thin metal film, or by vapor deposition of a dielectric multilayer film or a dielectric single layer. In addition, the reflective layer 14 may be formed by applying and curing a white or silver-based paint, an ultraviolet-curable resin or a thermosetting resin containing a white or silver-based pigment or beads, or the like, by various application methods such as spray coating, die coating, screen printing, or groove filling by wiping.

[0034] Fig. 4 is a diagram showing how image light and external light enter the screen 10 of this embodiment and travel. The cross section of the screen 10 shown in Fig. 4 is similar to the cross section of the screen 10 shown in Fig. 2 described above. For ease of understanding, Fig. 4 shows that there is no refractive index difference at the interface between the surface layer 11 and the base material layer 12 (light diffusion layer 121) and at the interface between the base material layer 12 (colored layer 122) and the lens layer 13. As shown in FIG. 4, image light Lb projected from an image source LS enters the surface layer 11 from below the screen 10, passes through the base layer 12, and enters the unit lenses 131 of the lens layer 13. Next, the image light Lb is incident on the lens surface 132, reflected by the reflective layer 14, proceeds toward the image source side (+Z side), and is emitted from the surface layer 11 in the front direction of the screen 10.

[0035] This image light Lb is diffused by the rough surface shape of the surface layer 11 (the fine uneven surface shape of the surface layer 11) and the light diffusion layer 121 of the base material layer 12 before being reflected by the reflective layer 14, and is diffused again by the light diffusion layer 121 and the rough surface shape of the surface layer 11 and is emitted to the viewer side after being reflected by the reflective layer 14. As a result, the image light Lb is diffused appropriately, and a sufficient viewing angle can be ensured. As described above, the image light Lb is efficiently reflected and diffused before reaching the observer O (see FIG. 1), and the screen 10 has a sufficient viewing angle and front luminance, allowing good images to be displayed.

[0036] Furthermore, since the image light Lb is projected from below the screen 10 and the angle β (see Figure 3 (b)) is greater than the angle of incidence of the image light Lb at each point in the vertical direction (Y direction) of the screen 10, the image light Lb does not directly enter the non-lens surface 133.

[0037] On the other hand, unnecessary external light G1, G2 such as sunlight and illumination light that enters the screen 10 from the image source side (+Z side) mainly enters from above the screen 10, passes through the surface layer 11 and the base material layer 12, and enters the unit lenses 131 of the lens layer 13, as shown in Figure 4. The external light G1 is reflected by the lens surface 132 and travels mainly downward (-Y side) within the screen 10, and is attenuated by being emitted downward from the surface of the screen 10 on the image source side or by being absorbed by the colored layer 122 within the screen 10. Therefore, the external light G1 does not reach the viewer O directly, and even if it does reach the viewer O, the amount of light is significantly less than that of the image light Lb.

[0038] External light G2 enters non-lens surface 133, is reflected by reflective layer 14, enters lens surface 132, is reflected by reflective layer 14, and then exits toward the upper side (+Y side) of screen 10 above the viewer side (+Z side). Therefore, the screen 10 can sufficiently suppress the influence of external light entering from above on the viewer side (+Z side).

[0039] Furthermore, when external light enters the screen 10 from the rear side (−Z side), it is reflected by the reflective layer 14 and does not reach the viewer O. From the above, the screen 10 can suppress the reduction in image contrast caused by external light, and by lowering the black luminance of the image, can relatively improve the contrast of the image, thereby enabling good images to be displayed even in a bright room environment.

[0040] (Regarding ease of winding, etc.) The screen 10 of the present embodiment has flexibility that allows it to be rolled up and stored when not in use. Such a rollable screen is required to simultaneously achieve the following main performances: -Easy to wind (can be wound quickly and easily with little force) Flatness (there should be minimal distortion on the display surface of the screen when unrolled and used) - Bending durability (the screen should not suffer damage such as creases or scratches even after repeated winding and unwinding)

[0041] The screen 10 of the present embodiment solves these problems by carefully selecting the resin forming the base layer 12, which has the greatest thickness in the screen (i.e., the resin serving as the base material of the light diffusion layer 121 and the colored layer 122), and by satisfying the following condition A. Furthermore, by satisfying condition A, the screen 10 of the present embodiment can solve these problems even when used as a screen applied to an ultra-short focus image projection method in which the image projection angle is large and the projection distance is short. Moreover, the screen 10 of this embodiment satisfies condition B in addition to condition A, thereby further improving the ease of winding, flatness, bending durability, and the like.

[0042] Furthermore, in recent years, screens that emit sound from the screen have been developed, and high sound reproducibility is also required. The screen 10 of this embodiment can simultaneously satisfy these additional requirements by further satisfying the following condition C.

[0043] Regarding ease of winding, flatness, and bending durability, it is preferable that the screen satisfies the following condition A. (Condition A) The tensile strength is 31 MPa or more and 43 MPa or less, and the flexural strength is 45 MPa or more and 79 MPa or less. In order to further improve the ease of winding, flatness, and bending durability, it is preferable that the screen satisfy, in addition to condition A, condition B shown below. (Condition B) If the tensile modulus of elasticity is Et and the flexural modulus of elasticity is Eb, the ratio Et / Eb is 1.02 or more and 1.04 or less, and the Poisson's ratio is 0.37 or more and 0.39 or less.

[0044] Next, with regard to improving the reproducibility of the acoustic response, it is preferable that the screen satisfies the following condition C. (Condition C) Charpy impact strength is 1.8Kj / m 2 More than 3.5Kj / m 2 It is less than or equal to.

[0045] (Sample evaluation) Here, screen samples 1 to 9 were prepared and evaluated for ease of winding and the like. The screens of Samples 1 to 9 have the same screen size and the same shape and thickness of each layer, but differ in the resin forming the base layer 12 (the resin that is the base material for the light diffusion layer 121 and the colored layer 122).

[0046] The screens for samples 1 to 9 have the following in common: Screen size: 80 inches (approximately 1000 mm vertically and 1800 mm horizontally). Surface layer 11: Made of urethane acrylate resin, approximately 10 μm thick. Base layer 12: A layer in which a light diffusing layer 121 and a colored layer 122 are laminated. The thickness is about 250 μm. Light diffusion layer 121: Approximately 125 μm thick, containing spherical particles made of acrylic resin with an average particle size of 30 μm as a diffusion material. Colored layer 122: Approximately 125 μm thick, containing carbon black as a coloring material. Lens layer 13: Made of acrylic resin, average thickness approximately 30 to 90 μm. Reflective layer 14: Vapor-deposited aluminum film, thickness 800 Å.

[0047] The screens of Samples 1 to 5 all have a base layer 12 whose main material is SBC resin (styrene-butadiene copolymer resin), but each has different physical properties, etc. The SBC resin used for the base layer 12 of the screens of Samples 1 to 5 was made by selecting three SBCs from various grades of Asahi Kasei Corporation's Asaflex and Denka Company's Clearlen based on their optical properties as a screen and their suitability for screen manufacturing, and named them resin materials SBC-1, SBC-2, and SBC-3.

[0048] SBC resin (styrene-butadiene copolymer resin) has high transparency, flexibility, and high hinge properties, and is characterized by being less susceptible to damage such as creases and scratches even when folded in sheet form. By using this SBC resin as the material for forming the base layer 12, which is the thickest layer in the screen 10, it is possible to achieve flexibility that allows winding, as well as improve ease of winding, flatness, and durability.

[0049] The materials forming the base layer 12 of the screens of Samples 1 to 9 are as follows: Sample 1 is SBC-1, Sample 2 is SBC-2, Sample 3 is a mixed resin of SBC-1 and SBC-2 (SBC-1:SBC-2=50:50), Sample 4 is a mixed resin of SBC-1 and PS (polystyrene) (SBC-1:PS=75:25), Sample 5 is a mixed resin of SBC-2 and PS (polystyrene) (SBC-2:PS=75:25), Sample 6 is PS (polystyrene), Sample 7 is SBC-3, Sample 8 is PU (polyurethane), and Sample 9 is PC (polycarbonate). PU generally has low rigidity and is not often used as a material for the base layer in flat screens, etc. PC, on the other hand, has high rigidity and is widely used as a material for the base layer in flat screens.

[0050] For each sample screen, the tensile strength and the like were measured by preparing test pieces as described below. The tensile strength was measured in accordance with JIS K 7161-1 and JIS K 7161-2 using a test piece 30A of a predetermined size cut out from the screen of each sample. Fig. 5 is a diagram illustrating a test piece 30A used for measuring the tensile strength, showing a plan view of the test piece 30A. As shown in Fig. 5, the test piece 30A has a so-called dumbbell shape in which both ends in the longitudinal direction are wider than the center when viewed from above. The test piece 30A is cut out from the vicinity of point A, which is the center of the screen of each sample. At this time, point A may be located within the test piece 30A. The longitudinal direction of the test piece 30A is the vertical direction of the screen. The dimensions of each part of the test piece 30A are as follows: total length L3 is 150 mm, parallel part length L1 is 60 mm, gripping part width B2 is 20 mm, gauge length L0 is 50 mm, parallel part width B1 is 10 mm, and gripping part distance L is 115 mm.

[0051] In addition, not only in the measurement of the tensile strength value, but also in each of the following measurements, if the screen of each sample has a protective layer (backing) or the like provided on the rear side of the reflective layer 14 for protecting the reflective layer 14, the protective layer is peeled off to prepare a test specimen. In addition, not only in the measurement of the tensile strength value, but also in each of the following measurements, the influence of differences in thickness between test pieces of each sample is to be appropriately corrected by measuring the thickness of each test piece and inputting the measured thickness into the test conditions. In addition, the effect of the cut-out position of the test piece was investigated, but no particular bias was found within the plane of the screen. Therefore, the test piece was cut out from the vicinity of point A, which is the center of the screen.

[0052] The bending strength was measured in accordance with JIS K 7171 using a test piece 30B cut out from the vicinity of point A, which was the center of the screen of each sample. Although not shown, the test piece 30B has a rectangular shape in a plan view, and the longitudinal direction of the test piece 30B is the vertical direction of the screen. Point A may be located within the test piece 30B. The test piece 30B has a length of 80 mm and a width of 10 mm in plan view. The thickness of each test piece 30B is actually measured and input into the test conditions, so that the influence of the difference in thickness between the test pieces 30B of each sample is corrected.

[0053] The tensile elastic modulus Et of the screen of each sample was determined as follows. The tensile modulus Et was measured using a test piece 30A cut out from the screen of each sample in accordance with JIS K 7127. This test piece 30A is the same member as the test piece used in the above-mentioned measurement of tensile strength. The flexural modulus Eb was measured using a test piece 30B cut out from the screen of each sample in accordance with JIS K 7171. This test piece 30B is the same member as the test piece used in the measurement of the above-mentioned flexural strength. The Poisson's ratio was calculated by attaching a lattice scale as a strain gauge to the same test piece 30A as the above-mentioned tensile elastic modulus, and measuring the elongation in the tensile load direction and the contraction in the perpendicular direction.

[0054] The Charpy impact strength was measured in accordance with JIS K 7111-1:2012 6.3.2 using a test piece (not shown) cut out from the vicinity of point A, which is the center of the screen of each sample. The test piece used for measuring the Charpy impact strength was prepared in accordance with test piece type 3 described in Table 1 of JIS K7111-1:2012. In a test to measure Charpy impact strength, a test piece is supported horizontally at two points, and the Charpy impact strength is calculated by dividing the energy required to destroy it with a single blow using a hammer (pendulum) by the cross-sectional area.

[0055] The screens of Samples 1 to 9 were evaluated for ease of winding, etc. FIG. 6 is a table showing the evaluation results of the tensile strength and other properties of the screens of Samples 1 to 9, as well as the ease of winding. 6, for the screens of Samples 1 to 9, those that satisfied the conditions A, B, and C are indicated with "◯", and those that did not are indicated with "X". In addition, the testers also evaluated the ease of winding up the screens of Samples 1 to 9, the flatness of the screen during use, the durability against bending, the reproducibility of the acoustic response, etc.

[0056] The ease of winding was evaluated by placing each sample screen (80 inches) on a wall and unwinding and winding the screen as one set, performing a total of five sets. The winding and unwinding of the screen was performed by a drive device (not shown) used in the image display device. The ease of winding up the screen was evaluated based on the number of times that winding up and unwinding could be performed at a speed of 4 m / min or more without causing defects such as curling, wrinkles, or layer misalignment (floating or misalignment of the layers that form the screen) during winding and unwinding of the screen (i.e., the number of times that one set of winding up and unwinding could be performed within one minute if the length of the screen in the winding and unwinding direction is 2 m). A screen that could be wound up and unwinded 5 times at the above speed was rated as good, 3 to 4 times was rated as acceptable, and 0 to 2 times was rated as unacceptable. In the table shown in Figure 6, a screen that was good in terms of ease of winding up was indicated with "◎", a screen that was acceptable was indicated with "◯", and a screen that was unacceptable was indicated with "X".

[0057] Regarding flatness, the screen of each sample was spread out along a vertically standing wall, and image light was projected from the image source LS using an ultra-short focus image projection method, and the degree of distortion of the displayed image was compared and evaluated. The tester views the image from a position 2 m toward the observer (+Z side) from point A, which is the center of the screen, selects the largest distorted area (area where distortion occurs in the image) and measures the maximum length of that distorted area. The shape of the distorted area is indefinite, and the number of distorted areas that occur is also indefinite. Therefore, this maximum length is the maximum length of the shape of the distorted area. A maximum length of less than 1 cm was rated as good, 1 cm to less than 3 cm was rated as acceptable, and 3 cm or more was rated as unacceptable. In the table shown in Figure 6, good flatness is indicated with "◎", acceptable flatness is indicated with "◯", and unacceptable flatness is indicated with "×".

[0058] For bending durability, a rectangular test piece 80 mm long and 10 mm wide was cut out with the center at point A, which was the center of the screen, and this was folded in half widthwise at the center of the length, held in this state for four hours, and the condition immediately after being released was observed. In the table shown in Figure 6, screens without damage such as creases or scratches are indicated as good by "◎", and screens with damage are indicated as unacceptable by "×".

[0059] The acoustic response reproducibility was evaluated as follows. First, the tester sends electric signals of low-pitched sound (250 Hz) and high-pitched sound (2000 Hz) to a general speaker (not shown), and measures the frequency of the generated sound with a standard sound level meter (NL-42A / Rion Co., Ltd.) at a position 3 m in front of the speaker. This is the reference frequency. Next, a voice coil and magnetic circuit were connected to the screen of each sample, and electric signals of a low-pitched sound (250 Hz) and a high-pitched sound (2000 Hz) were sent to generate sounds. The tester measured the frequency of the sounds using an ordinary sound level meter (NL-42A / Rion Co., Ltd.) at a position 3.0 m normal to the screen surface from point A, which was the center of the screen on the observer side (+Z side) of each sample screen.

[0060] The tester evaluated the acoustic response reproducibility by determining whether the average value of the difference in frequency between the low-frequency sound and the high-frequency sound was 30 Hz or less as good, whether it was greater than 30 Hz and less than 60 Hz as acceptable, and whether it was 60 Hz or more as unacceptable. In the table shown in Figure 6, good acoustic response reproducibility is indicated with "◎", acceptable acoustic response reproducibility is indicated with "◯", and unacceptable acoustic response reproducibility is indicated with "X".

[0061] As shown in the table of FIG. 6, the screens of Samples 1 to 5 satisfy condition A, but the screens of Samples 6 to 9 do not satisfy condition A. Furthermore, the screens of Samples 1 to 3 and 6 satisfy condition B, but the screens of Samples 4, 5 and 7 to 9 do not satisfy condition B. Furthermore, the screens of Samples 1 and 3 satisfy condition C, but the screens of Samples 2 and 4 to 9 do not satisfy condition C.

[0062] The screens of Samples 1 to 5 were easy to wind up, could be wound up quickly with little force, and had a small winding diameter. The screens of Samples 1 to 5 also had high flatness during use, and the area where image distortion occurred was small. The screens of Samples 1 to 5 also had sufficient bending durability, and did not suffer from damage such as creases or scratches, and did not warp. Furthermore, as shown in the table of FIG. 6, among the screens of Samples 1 to 5, the screens of Samples 1 to 3 in particular were excellent in terms of ease of winding, flatness of the screen during use, and durability against bending.

[0063] As described above, the screens of Samples 1 to 5 satisfy condition A, and Samples 1 to 3 also satisfy condition B. Therefore, by satisfying condition A, the screen can be easily rolled up, has good flatness, and has good bending durability, and by further satisfying condition B, these performances can be improved.

[0064] In contrast, the screens of samples 6, 8, and 9, which did not satisfy condition A, had a large repulsive force during winding, making it difficult to wind them up, as a large force was required for winding and the winding diameter was large. Also, the screen of sample 7, which did not satisfy condition A and had a tensile strength and bending strength lower than the preferable range of condition A, could be wound up with little force, but there was also the problem of wrinkles occurring in the screen during the winding process. The screens of Samples 7 to 9 had low bending durability, with damage such as creases and scratches occurring in the bending durability test. In particular, the screen of Sample 7 had low bending durability, with warping remaining, rolling wrinkles occurring, and a portion of the lens layer 13 cracking in the bending durability test.

[0065] When a material with a high elastic modulus, i.e., a material with high rigidity, is used as the material forming the base layer 12 of the screen, the restoration when unfolded from a rolled up state is good and the flatness of the screen is improved, but on the other hand, a large force is required for winding and the roll diameter tends to be large. On the other hand, when a material with low rigidity is used as the material forming the base layer 12 of the screen, it becomes possible to wind with a small force and the roll diameter can be made small, but on the other hand, there is a tendency for winding wrinkles and winding marks to occur and flatness to decrease. For these reasons, it is preferable that the screen 10 of this embodiment uses SBC resin as the material for the base material layer 12. SBC resin has high transparency, flexibility, and hingeability, and is less likely to suffer damage such as creases or scratches even when the sheet is folded. In the screens of Samples 1 to 5 described above, SBC resin is used as the material for the base material layer 12.

[0066] Furthermore, as shown in the table of Fig. 6, the screens of Samples 2 and 4 to 9, which did not satisfy condition C, had poor acoustic response reproducibility. In contrast, the screens of Samples 1 and 3, which satisfied condition C, had good acoustic response reproducibility. In view of the above, the screen 10 of this embodiment can be made to be a better screen by selecting one that further satisfies condition C in accordance with the desired performance.

[0067] (Variations) The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present invention.

[0068] (1) The screen 10 of this embodiment may be configured to have a protective layer on the back side (-Z side) of the reflective layer 14, which has the function of protecting the reflective layer 14 and the unit lenses 131 of the lens layer 13, and also protecting the back side of the screen 10. The protective layer is formed, for example, by filling in resin so as to fill in the irregularities of the unit lenses 131 and make the surface on the rear side of the screen 10 flat. From the viewpoint of improving the contrast of an image by absorbing unnecessary external light incident from the rear side, such a protective layer preferably has a light absorbing effect. Furthermore, in cases where a decrease in contrast due to external light from the rear side is unlikely to occur in the usage environment of the screen, the protective layer may have optical transparency.

[0069] When the protective layer has light absorbing properties, it can be formed from a resin containing a light absorbing material. As the light absorbing material, a paint having a light absorbing effect, such as a dark color paint, such as black, a pigment or dye having a dark color such as black, or beads having a light absorbing effect are preferable. As the resin containing a light absorbing material, a thermosetting resin such as an epoxy resin or a urethane resin, a thermoplastic resin such as an acrylic resin, or an ultraviolet-curing resin such as a urethane acrylate or an epoxy acrylate is preferable. When the protective layer has light absorbing properties, a reflective layer may not be formed on non-lens surface 133, and non-lens surface 133 may be covered with the protective layer. With such a configuration, it is possible to absorb unnecessary external light that enters from above the image source side (+Z side) of screen 10 and enters non-lens surface 133. In this case, it is preferable that the refractive index of the protective layer, i.e., the refractive index of the resin containing the above-mentioned light absorbing material, is equal to or higher than the refractive index of lens layer 13, from the viewpoint of efficiently absorbing unnecessary external light such as sunlight.

[0070] In the case where the protective layer is light-transmitting, the back side of the protective layer may be further covered with a flexible light-blocking screen made of cloth or resin that is less likely to transmit light, or a layer that improves scratch resistance. In addition, the protective layer may be made of flexible paper, nonwoven fabric, resin sheet, etc., and may be laminated on the back side of the lens layer 13 and the reflective layer 14 via a layer of adhesive or bonding agent (not shown). Furthermore, from the viewpoint of protecting the reflective layer 14 and the lens layer 13, the protective layer may have an ultraviolet absorbing function, a hard coat function, or the like.

[0071] (2) In the embodiment, the surface layer 11 may be a layer having one or more appropriate functions such as a hard coat function, an antiglare function, an antireflection function, an ultraviolet absorbing function, an antifouling function, an antistatic function, etc., or may be formed by laminating a plurality of layers having desired functions. In addition, a touch panel layer or the like may be provided as the surface layer 11.

[0072] (3) In the embodiment, the lens layer 13 may have a linear Fresnel lens shape.

[0073] (4) In the embodiment, the reflective layer 14 may be formed only on the lens surface 132, or may be formed only on a portion of the lens surface 132 (the area where the image light is incident).

[0074] (5) In the embodiment, lens surface 132 and non-lens surface 133 may be partially curved or may be a combination of a curved surface and a flat surface. In addition, at least one of lens surface 132 and non-lens surface 133 may be in a form composed of a plurality of flat surfaces (so-called folded surface). Furthermore, in the embodiment, the unit lens 131 may have a polygonal shape formed by three or more surfaces.

[0075] (6) In the embodiment, the image source LS may be located vertically above (on the +Y side of) the screen 10. In this case, the position of the image source LS in the vertical direction corresponds to the position of point C, which is the Fresnel center, and the screen 10 is used with its up-down direction inverted.

[0076] The present embodiment and the modified embodiment may be used in appropriate combination, but detailed description thereof will be omitted. The present invention is not limited to the above-described embodiment and the like. [Explanation of symbols]

[0077] 1. Video display device 10 Screens 11 Surface layer 12 Base material layer 121 Light diffusing layer 122 Colored layer 13 Lens layer 131 Unit Lens 132 Lens surface 133 Non-lens surface 14 Reflective layer LS video source

Claims

1. A reflective screen that reflects and displays an image light projected from an image source, a lens layer in which a plurality of unit lenses are arranged, each unit lens having a lens surface and a non-lens surface intersecting the lens surface; a reflective layer formed on at least a part of the lens surface and configured to reflect light; a base layer formed of a resin having optical transparency, disposed on a viewer side of the lens layer, and serving as a base material for the lens layer; It has flexibility that allows it to be rolled up, The tensile strength is 31 MPa or more and 43 MPa or less, and the bending strength is 45 MPa or more and 79 MPa or less. A reflective screen that features:

2. 2. The reflective screen according to claim 1, The ratio Et / Eb of the tensile elastic modulus Et to the flexural elastic modulus Eb is 1.02 or more and 1.04 or less, and the Poisson's ratio is 0.37 or more and 0.39 or less. A reflective screen that features:

3. 2. The reflective screen according to claim 1, Charpy impact strength is 1.8Kj / m ２ More than 3.5Kj / m ２ That is: A reflective screen that features:

4. 2. The reflective screen according to claim 1, the base layer has a light diffusion portion containing a diffusion material that diffuses light in at least a part of the thickness direction of the base layer; A reflective screen that features:

5. 2. The reflective screen according to claim 1, the base layer is formed of a styrene-butadiene copolymer resin (SBC resin); A reflective screen that features:

6. 2. The reflective screen according to claim 1, the base layer has a colored portion in at least a part of its thickness direction, the colored portion containing a coloring material having a light absorbing effect of absorbing a part of incident light; A reflective screen that features:

7. A reflective screen according to any one of claims 1 to 6, an image source that projects image light onto the reflective screen; A video display device comprising:

Images