Reflective screen, video display device

Abstract

To provide a reflection type screen and a video display device with which it is possible to display a good video having high transparency and high contrast.SOLUTION: A screen 10 is a reflection type screen comprising: diffusion parts 15 that are arranged along the screen surface; a first light permeable part 12 and a second light permeable part 14 that are provided between the adjacent diffusion parts 15; and a low refractive index layer 13 that is provided between the first light permeable part 12 and the second light permeable part 14 so as to be inclined at a prescribed angle θ2 with respect to the thickness direction of the screen 10, and that has a lower refractive index than the first light permeable part 12. The diffusion part 15 has a fourth plane 15d that is a rear-side plane and contains a light diffusion material 152 that diffuses light. When, in a cross section parallel to the arrangement direction of the diffusion part 15 and the thickness direction of the screen 10, the dimension of the fourth plane 15d in the arrangement direction of the diffusion part 15 is defined as W2 and the dimension of the diffusion part 15 in the thickness direction of the screen 10 is defined as h1, then the relationship h1>W2 holds true.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a reflective screen that reflects and displays video light, and a video display device.

Background Art

[0002] Conventionally, various reflective screens that reflect and display video light projected from a video source have been developed. Among them, a reflective screen that can be used as a reflective screen for projecting video light and allowing the video to be clearly visible, and that has transparency such that the scenery on the other side of the screen can be seen through when not in use, i.e., when no video light is projected (a semi-transmissive reflective screen), is in increasing demand due to its high design quality (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a semi-transmissive reflective screen, part of the video light passes through the reflective screen. However, if the amount of the transmitted video light is large, there is a problem that the light utilization efficiency is poor and the video becomes dark. In addition, there is a problem that the projected image is projected onto people and objects located on the ceiling or the back side due to such transmitted video light. Therefore, for example, in a screen such as that of Patent Document 1, in order to reduce the amount of the transmitted video light, improvements such as reducing the arrangement pitch of the light scattering portions are assumed. However, reducing the array pitch of the light scattering portions causes problems such as increased haze and decreased contrast of the video displayed on the screen. Further, reducing the array pitch of the light scattering portions also causes a problem that the diffraction phenomenon occurs due to external light such as sunlight transmitted through the screen, resulting in a decrease in transparency.

[0005] An object of the present invention is to provide a reflective screen and a video display device that have high transparency, high contrast, and can display a good video.

Means for Solving the Problems

[0006] The present invention solves the above problems by the following means. For ease of understanding, reference numerals corresponding to the embodiments of the present invention are attached for explanation, but the present invention is not limited thereto. A first invention is a reflective screen that visually displays video light projected from a video source to an observer, having a function of diffusing at least a part of incident light, and diffusion portions (15) arranged along the screen surface, a first light transmission portion (12) provided between adjacent diffusion portions, a second light transmission portion (14) provided between adjacent diffusion portions and on the back side of the first light transmission portion, and a low refractive index layer (13) provided between the first light transmission portion and the second light transmission portion and inclined at a predetermined angle with respect to the thickness direction of the reflective screen and having a lower refractive index than the first light transmission portion. The diffusion portion contains a light diffusing material that diffuses light. The diffusion portion has a fourth surface (15d) that is the back side surface. In a cross section parallel to the arrangement direction of the diffusion portion and the thickness direction of the reflective screen, when the dimension of the fourth surface in the arrangement direction of the diffusion portion is W2 and the dimension of the diffusion portion in the thickness direction of the reflective screen is h1, h1 > W2. The reflective screen (10) is characterized by this. A second invention is the reflective screen according to the first invention, wherein the angle formed by the low refractive index layer (13) with the thickness direction of the reflective screen is larger than the angle formed by the video light (Lt) incident on the first light transmission portion with the thickness direction of the reflective screen. The reflective screen (10) is characterized by this. The third invention is a reflective screen according to the first invention or the second invention, wherein the diffusion part (15) has a first surface (15a) which is the surface on the video source side, and in a cross-section parallel to the arrangement direction of the diffusion part and the thickness direction of the reflective screen, the cross-sectional shape of the diffusion part is a trapezoidal shape, and the dimension of the first surface in the arrangement direction of the diffusion part is smaller than the dimension of the fourth surface (15d) in the arrangement direction of the diffusion part, and is a reflective screen (10) characterized by this. The fourth invention is a reflective screen according to any one of the first invention to the third invention, wherein the diffusion part (15) has a second surface (15b) and a third surface (15c) facing each other in the arrangement direction of the diffusion part, and when the angles formed by the second surface and the third surface with the thickness direction of the reflective screen are angle θ3 and angle θ1 respectively, it satisfies θ3 = θ1, and is a reflective screen (10) characterized by this. The fifth invention is a reflective screen according to any one of the first invention to the fourth invention, wherein the arrangement pitch of the diffusion part (15) is 100 to 1000 μm, and is a reflective screen (10) characterized by this. The sixth invention is a reflective screen according to any one of the first invention to the fifth invention, wherein the average particle diameter of the light diffusing material is 1 μm or more, and is a reflective screen (10) characterized by this. The seventh invention is a reflective screen according to any one of the first invention to the sixth invention, wherein the diffusion part (15) has a first surface (15a) which is the surface on the video source side, and the average particle diameter of the light diffusing material is equal to or less than the dimension of the first surface in the arrangement direction of the diffusion part, and is a reflective screen (10) characterized by this. The eighth invention is a reflective screen according to any one of the first invention to the seventh invention, wherein the video light is incident on the diffusion part and diffused, and a part of it is emitted to the video source side and a part of it is emitted to the back side, and is a reflective screen (10) characterized by this. The ninth invention is a reflective screen according to any one of the first to eighth inventions, characterized in that the refractive indices of the first light transmission part (12) and the second light transmission part (14) are equal. The tenth invention is a reflective screen according to any one of the first to ninth inventions, characterized in that the diffusion part (15) is formed in a strip shape so as to extend in a first direction along the screen surface of the reflective screen, is arranged in a second direction intersecting the first direction, and the cross-sectional shape in a cross-section parallel to the second direction and the thickness direction of the reflective screen is a wedge shape. The eleventh invention is a reflective screen according to any one of the first to tenth inventions, characterized in that, in addition to the diffusion part (15), it does not have a part containing a light diffusing material for diffusing light. The twelfth invention is a reflective screen according to any one of the first to eleventh inventions, characterized in that the angle formed by the low refractive index layer (13) with respect to the thickness direction of the reflective screen changes continuously or stepwise in the arrangement direction of the low refractive index layer. The thirteenth invention is a reflective screen according to any one of the first to twelfth inventions, characterized in that the arrangement pitch of the diffusion part changes continuously or stepwise in the arrangement direction of the diffusion part (15). The fourteenth invention is a video display device (1) comprising a reflective screen (10) according to any one of the first to thirteenth inventions and a video source (LS) for projecting video light onto the reflective screen.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a reflective screen and a video display device with high transparency, high contrast, and capable of displaying good images.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. Note that each of the drawings shown below, including FIG. 1, is a schematically shown diagram, and the size and shape of each part are appropriately exaggerated for easy understanding. In this specification, for terms specifying shapes and geometric conditions, such as terms like parallel and orthogonal, in addition to their strict meanings, states having errors to the extent that they exhibit similar optical functions and can be regarded as parallel or orthogonal are also included.

[0010] Also, in this specification, words such as plate and sheet are used, but in general usage, in order of increasing thickness, they are used in the order of plate, sheet, and film, and this specification also follows this usage. However, since there is no technical meaning in such a distinction, these expressions can be replaced as appropriate. Also, in this specification and the claims, the screen surface refers to the surface that is the planar direction of the screen when viewed as a whole, and is assumed to be parallel to the screen of the screen (display surface).

[0011] (Embodiment) FIG. 1 is a diagram showing the video display device 1 of the present embodiment. In FIG. 1(a), it is a perspective view of the video display device 1, and FIG. 1(b) is a view of the video 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 the present embodiment is a reflective screen that reflects the image light L projected from the image source LS and displays an image on its screen. Details of this screen 10 will be described later. In the present embodiment, as an example, the image display device 1 is applied to a store window, and it is assumed that the screen 10 is fixed to the glass of a window (not shown).

[0012] Here, for ease of understanding, in each of the figures shown below including FIG. 1, an XYZ orthogonal coordinate system is appropriately provided and shown. In this coordinate system, the left - right direction of the screen of the screen 10 is the X - direction, the up - down direction of the screen is the Y - direction, and the thickness direction of the screen 10 is the Z - direction. The screen of the screen 10 is parallel to the XY plane, and the thickness direction (Z - direction) of the screen 10 is orthogonal to the screen of the screen 10. The screen 10 of the present embodiment is arranged such that the screen is parallel to the vertical direction and the horizontal direction in the use state.

[0013] Also, when viewed from an observer O located in the front direction of the screen 10, the direction toward the right side in the left - right direction 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) to 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 of the screen, the left - right direction of the screen, and the thickness direction refer to the up - down direction of the screen (vertical direction), the left - right direction of the screen (horizontal direction), and the thickness direction (depth direction) in the use state of this screen 10, and are parallel to the Y - direction, X - direction, and Z - direction respectively.

[0014] The image source LS is an image projection device that projects the image light L onto the screen 10, and is, for example, a short - focus projector. In the use state of the image display device 1, when the screen (display area) of the screen 10 is viewed from the front direction (the normal direction of the screen surface), the image source LS is located at the center in the left - right direction of the screen of the screen 10 and is located below the screen of the screen 10 in the vertical direction. The image source LS can project the image light L obliquely from a position where the distance from the surface of the screen 10 in the depth direction (Z direction) of the image display device 1 is significantly closer than that of a conventional general-purpose projector. Therefore, compared with a conventional general-purpose projector, the image source LS has a shorter projection distance to the screen 10 and a larger incident angle at which the projected image light L enters the screen 10.

[0015] The screen 10 is a reflective screen that reflects the image light L projected by the image source LS toward the observer O side to display an image, and is a semi-transmissive reflective screen having transparency that allows the observer O to observe the scenery (-Z side) on the other side of the screen 10 through the screen 10. The screen (display area) of the screen 10 has a rectangular shape in which the long side direction is the left-right direction (X direction) of the screen when viewed from the observer O side in the use state. The screen 10 has a large screen with a screen size of about 80 to 100 inches diagonal, and the aspect ratio of the screen is 16:9. Note that this is not limiting, and for example, it may be sized about 40 inches or less, and the size and shape can be appropriately selected according to the purpose of use, the use environment, etc.

[0016] Generally, the screen 10 is a laminate of thin resin layers or the like, and often does not have sufficient rigidity to maintain flatness by itself. Therefore, the screen 10 is integrally joined (or partially fixed) to an unillustrated support plate via an unillustrated bonding layer having light transmissivity on the back side (-Z side) to maintain the flatness of the screen. This unillustrated support plate is a flat plate member having light transmissivity and high rigidity, and a plate-like member made of resin such as acrylic resin or PC resin, or glass can be used. In this embodiment, the image display device 1 is applied to a show window such as a store, and the support plate is a window glass. Note that the screen 10 is not limited to the above example, and the four sides and the like of the screen 10 may be supported by an unillustrated frame member or the like to maintain its flatness.

[0017] FIG. 2 is a diagram showing the layer structure of the screen 10 of the present embodiment. In FIG. 2, a part of a cross-section parallel to the vertical direction (Y direction) of the screen and orthogonal to the screen surface (parallel to the Z direction) passing through point A (see FIGS. 1(a) and 1(b)) which is the center of the screen (geometric center of the screen) of the screen 10 is enlarged and shown. FIG. 3 is a diagram showing an enlarged view of the first light transmission part 12 and the like of the present embodiment. FIG. 3 shows an enlarged view of the first light transmission part 12, the low refractive index layer 13, the second light transmission part 14, and the diffusion part 15 in the cross-section of the screen 10 shown in FIG. 2 for easy understanding. As shown in FIG. 2, the screen 10 includes, in order from the image source side (+Z side), a first base material layer 11, a first light transmission part 12, a low refractive index layer 13, a second light transmission part 14, a diffusion part 15, and a second base material layer 16.

[0018] The screen 10 of the present embodiment selectively diffuses more of the image light L projected from the image source LS located below (-Y side) the image source side (+Z side) by the diffusion part 15 described later than the light incident from other directions, and emits a part thereof toward the image source side, thereby displaying an image visible to the observer O. Further, this screen 10 transmits most of the light other than the image light L without diffusion, realizing transparency that allows the scenery on the other side to be confirmed through the screen 10.

[0019] The first base material layer 11 is a sheet-like member having light transmissibility, and the first light transmission part 12 is integrally formed on the surface on the back side (-Z side). The first base material layer 11 is a layer serving as a base material for forming the first light transmission part 12. The first base material layer 11 is formed of, for example, a polyester resin such as PET (polyethylene terephthalate) having high light transmissibility, an acrylic resin, a styrene resin, an acrylic styrene resin, a PC (polycarbonate) resin, an alicyclic polyolefin resin, a TAC (triacetyl cellulose) resin, or the like.

[0020] The first light transmission part 12 is a light-transmissive part formed on the surface of the back side (-Z side) of the first base material layer 11. The first light transmission part 12 has a convex shape on its back side surface and is arranged along the screen surface. In the present embodiment, the cross-sectional shape of the first light transmission part 12 shown in FIG. 2 is a triangular shape that protrudes toward the back side (-Z side), and it is formed in a strip shape so that its cross-sectional shape extends in a direction intersecting the arrangement direction of the first light transmission part 12. In the present embodiment, the extending direction of the first light transmission part 12 is the horizontal direction (X direction) of the screen, and the arrangement direction of the first light transmission part 12 is the vertical direction (Y direction) of the screen. Moreover, the first light transmission part 12 of the present embodiment has a continuous part that is continuous along the screen surface (XY plane) between adjacent first light transmission parts 12 at the end on the image source side (+Z side). Note that the first light transmission part 12 may be configured not to have this continuous part.

[0021] In the cross-section of the screen 10 shown in FIG. 2, the first light transmission part 12 has a first surface 12a and a second surface 12b that are located on the upper side (+Y side) with the vertex t1 in between. In the cross-section of the screen 10 shown in FIG. 2, the first surface 12a forms an angle θ1 [°] with respect to the thickness direction (Z direction) of the screen 10, and the second surface 12b forms an angle θ2 [°] with respect to the thickness direction (Z direction) of the screen 10. This angle θ2 is larger than the angle θ1 and satisfies the relationship θ2 > θ1.

[0022] The first light transmission part 12 is formed of an ultraviolet curable resin such as a urethane acrylate-based, polyester acrylate-based, epoxy acrylate-based, polyether acrylate-based, polythiol-based, butadiene acrylate-based resin with high light transmittance. Note that the resin constituting the first light transmission part 12 is not limited to the above-mentioned ultraviolet curable resin, and for example, other ionizing radiation curable resins such as electron beam curable resins or thermoplastic resins may also be used. Also, it is preferable that the refractive index of the first light transmission part 12 is 1.54 or more from the viewpoint of efficiently total-reflecting image light at the interface with the low refractive index layer 13 described later. The first light transmission part 12 of this embodiment is formed of an ultraviolet-curable urethane acrylate resin (refractive index n1 = 1.55).

[0023] The low refractive index layer 13 is provided between the first light transmission part 12 and the second light transmission part 14 in the thickness direction (Z direction) of the screen 10, and between adjacent diffusion parts 15 in the arrangement direction (Y direction) of the diffusion parts 15. This low refractive index layer 13 is a layer having a lower refractive index than the first light transmission part 12 and the second light transmission part 14 and having light transmissivity. The low refractive index layer 13 is provided at a position in contact with the second surface 12b of the first light transmission part 12.

[0024] As shown in FIG. 2, the low refractive index layer 13 is provided to be inclined at an angle with respect to the thickness direction (Z direction) of the screen 10. In the low refractive index layer 13 of this embodiment, the upper (+Y side) end portion is located on the back side (-Z side), and the lower (-Y side) end portion is inclined so as to be located on the video source side (+Z side), and forms an angle θ2 [°] with respect to the thickness direction of the screen 10. Further, in the low refractive index layer 13 of this embodiment, the upper (+Y side) end portion is in contact with the back side (-Z side) end portion of the diffusion part 15 adjacent to the upper side, and the lower (-Y side) end portion is in contact with the video source side (+Z side) end portion of the diffusion part 15 adjacent to the lower side.

[0025] This angle θ2 is provided such that the video light Lt projected from below the video source side and incident on the screen 10 and transmitted through the first light transmission part 12 is incident on the interface (second surface 12b) between the first light transmission part 12 and the low refractive index layer 13 at an angle equal to or greater than the critical angle and undergoes total reflection. Therefore, the angle θ2 is larger than the angle formed by the video light (for example, the video light Lt shown in FIG. 3) in the first light transmission part 12 with respect to the thickness direction of the screen 10. It is preferable from the viewpoint of efficiently making the video light incident on the diffusion part 15 that this angle θ2 is in the range of 30° or more and 80° or less, and more preferably in the range of 40° or more and 60° or less. If the angle θ2 is larger than this range, the image light incident on the screen 10 will pass through the screen 10 without total reflection at the interface (the second surface 12b) between the first light transmission portion 12 and the low refractive index layer 13, resulting in a dark image being displayed or the projection image being reflected onto the ceiling or the like on the back side, which is not preferable.

[0026] If the angle θ2 is smaller than this range, external light or the like that is desired to pass through the screen 10 (for example, external light G1, G2, etc. shown in FIG. 4 described later) will be totally reflected at the interface between the first light transmission portion 12 and the low refractive index layer 13 and at the interface between the low refractive index layer 13 and the second light transmission portion 14, and the transparency of the screen may decrease. Also, if the angle θ2 is smaller than this range, the arrangement pitch P1 of the diffusion portion 15 becomes smaller. As a result, the ratio of the area occupied by the diffusion portion 15 on the surface formed by the back surface (the third surface 14c) of the second light transmission portion 14 and the back surface (the fourth surface 15d) of the diffusion portion 15 may increase, and the transparency of the screen 10 may decrease. Further, if the angle θ2 is smaller than this range, the arrangement pitch P1 of the diffusion portion 15 becomes smaller, and a diffraction phenomenon due to transmitted light is likely to occur. From the above, the angle θ2 preferably satisfies the above range. In the present embodiment and FIG. 2, for ease of understanding, an example is shown in which the angle θ2 satisfies the above range and is constant in the arrangement direction (the vertical direction of the screen, the Y direction) of the low refractive index layer 13.

[0027] The low refractive index layer 13 is formed by depositing silicon dioxide (SiO2). When silicon dioxide is used, the refractive index of the low refractive index layer 13 is, for example, 1.44 or more and 1.46 or less. Note that the present invention is not limited to this. For example, it may be formed of a resin that satisfies the conditions of high light transmittance and a refractive index lower than those of the first light transmission portion 12 and the second light transmission portion 14, or a fluorine compound such as magnesium fluoride. Also, the formation method of the low refractive index layer 13 may be appropriately selected according to the material used. For example, in addition to the deposition method, it may be formed by a dip coating method, a spray method, CVD (Chemical Vapor Deposition), or the like.

[0028] As shown in FIG. 2, the second light transmission part 14 is provided at a position facing the second surface 12b of the first light transmission part 12 through the low refractive index layer 13, and is arranged along the screen surface. As shown in FIG. 3 and the like, the low refractive index layer 13 is positioned between the second light transmission part 14 and the first light transmission part 12. As shown in the cross-sectional shape in FIG. 4, the second light transmission part 14 has a triangular shape that is convex on the video source side (+Z side). The second light transmission part 14 of the present embodiment is formed in a strip shape so that its cross-sectional shape extends in the horizontal direction (X direction) of the screen, and is arranged in the vertical direction (Y direction) of the screen that intersects the extending direction.

[0029] The second light transmission part 14 has a first surface 14a located on the lower side (-Y side) across the vertex t2, a second surface 14b located on the upper side (+Y side), and a third surface 14c located on the back side (-Z side). The second surface 14b faces the second surface 12b of the first light transmission part 12 through the low refractive index layer 13, and the third surface 14c is parallel to the screen surface. Note that the second light transmission part 14 may be configured to have a continuous part continuous with the screen surface (XY plane) at the back side end between the convex shapes of adjacent second light transmission parts 14.

[0030] The second light transmission part 14 can be formed using an ultraviolet curable resin similar to the resin forming the aforementioned first light transmission part 12, an ionizing radiation curable resin, or a thermoplastic resin. Also, it is preferable that the second light transmission part 14 has the same refractive index as the first light transmission part 12 or the refractive index difference from the first light transmission part 12 is as small as possible from the viewpoint of suppressing the deviation of the video (transmitted video) observed through the screen 10. Therefore, similar to the first light transmission part 12, it is preferable that the refractive index of the second light transmission part 14 is 1.54 or more. The second light transmission part 14 of the present embodiment is formed of an ultraviolet curable urethane acrylate resin (refractive index n1 = 1.55) similar to the first light transmission part 12.

[0031] The diffusion part 15 is a part that diffuses at least a part of the incident light. The diffusion parts 15 are alternately arranged in the vertical direction (Y direction) of the screen at the convex part on the back side formed by the first light transmission part 12, the low refractive index layer 13, and the second light transmission part 14. The cross-sectional shape of the diffusion part 15 shown in FIG. 2 is continuous in the left-right direction (X direction) of the screen and extends in a strip shape in the left-right direction of the screen.

[0032] The cross-sectional shape of the diffusion part 15 shown in FIG. 2 is a wedge shape. The wedge shape here refers to a shape in which the width of one end is wide and gradually becomes narrower toward the other end, and includes a triangular shape, a trapezoidal shape, etc. The cross-sectional shape of the diffusion part 15 shown in FIG. 2 is a trapezoidal shape in which the width (dimension in the Y direction) on the video source side (+Z side) is smaller than the width (dimension in the Y direction) on the back side (-Z side), but it is not limited to this, and it may be a triangular shape with the video source side as the apex. In FIG. 2, the surface on the video source side of the diffusion part 15 is defined as the first surface 15a, the upper surface is defined as the second surface 15b, the lower surface is defined as the third surface 15c, and the surface on the back side is defined as the fourth surface 15d.

[0033] In this embodiment, the first surface 15a and the fourth surface 15d are parallel to the screen surface (XY plane). Also, the second surface 15b and the third surface 15c form angles θ3 and θ1 respectively with respect to the thickness direction (Z direction) of the screen 10. In this embodiment, the angle θ1 is equal to the angle θ3, satisfying θ1 = θ3. Therefore, the cross-sectional shape of the diffusion part 15 in this embodiment is an isosceles trapezoidal shape as shown in FIG. 2. From the viewpoint of easily and accurately manufacturing the diffusion part 15, both of these angles θ1 and θ3 are preferably 0° or more and 5° or less. The smaller the value of the angles θ3 and θ1, that is, the closer the second surface 15b and the third surface 15c are to being parallel to the thickness direction (Z direction) of the screen 10, the more the amount of light such as external light (G1, G2 shown in FIG. 4 described later) transmitted through the screen 10 increases, and the transparency of the screen 10 is improved, which is preferable.

[0034] The array pitch of the diffusion portions 15 (the array pitch of the first light transmission portion 12 and the second light transmission portion 14) is P1. Also, in the cross section shown in FIG. 2, in the vertical direction (Y direction) of the screen, the dimension of the first surface 15a of the diffusion portion 15 is W1, and the dimension of the fourth surface 15d is W2. Further, among the dimensions between adjacent diffusion portions 15 (the dimensions of the light transmission portions), the dimension between the ends on the video source side (+Z side) is W3, and the dimension between the ends on the back side (-Z side) is W4. Also, the height of the diffusion portion 15 (the dimension in the thickness direction of the screen 10) is h1. In the present embodiment, h1 > W2.

[0035] The array pitch P1 of the diffusion portions 15 is preferably 100 to 1000 μm, and more preferably 200 to 500 μm. By setting the array pitch P1 within the above range, while sufficiently ensuring the amount of transmitted light of the screen 10, the video light transmitted through the screen 10 can be totally reflected at the interface between the low refractive index layer 13 and the first light transmission portion 12 and made incident on the diffusion portions 15, and can be effectively diffused. Also, by setting the array pitch P1 within the above range, the diffraction phenomenon due to the arrangement of the diffusion portions 15 can be suppressed, and the diffusion portions 15 can be made difficult to be visually recognized by the observer O.

[0036] The diffusion portion 15 has a binder material 151 and a plurality of light diffusion materials 152 contained therein. In the screen 10 of the present embodiment, the diffusion portions 15 contain the light diffusion materials 152, but other portions (for example, the first base material layer 11, the second base material layer 16, the first light transmission portion 12, the second light transmission portion 14, etc.) do not contain such light diffusion materials. That is, only the diffusion portions 15 contain the light diffusion materials.

[0037] The binder material 151 is preferably a resin material having light transmissivity. For example, a transparent resin mainly composed of one or more of acrylic, styrene, polycarbonate, polyethylene terephthalate, acrylonitrile, etc., or an ionizing radiation curable resin such as an ultraviolet curable resin such as epoxy acrylate or urethane acrylate can be used.

[0038] The light diffusing material 152 has the function of diffusing light. In this embodiment, for example, a white pigment is used. Examples of the white pigment include metal oxides such as titanium oxide, titanium dioxide, magnesium oxide, and zinc oxide. As the white pigment, one of these metal oxides may be used, or it may be formed from a plurality of metal oxides.

[0039] In addition, the light diffusing material 152 is not limited to the above example, and the following materials may be used. For example, a silver pigment may be used as the light diffusing material 152. As the silver material, metal materials such as aluminum and chromium can be used. Also, for example, as the light diffusing material 152, a particulate member formed of a curable resin mixed with the above-mentioned white pigment or silver pigment may be used. At this time, the curable resin may be the same as the material forming the first light transmission portion 12 and the second light transmission portion 14. Further, as the light diffusing material 152, cross-linked particles obtained by polymerizing monomers centered on (meth)acrylic esters and styrene containing the above-mentioned white pigment or silver pigment, or particles such as urethane cross-linked particles may be used.

[0040] When particles formed of a curable resin containing a white pigment or a silver pigment are used as the light diffusing material 152, the shape is preferably spherical, but other shapes such as an ellipsoidal shape or a polyhedral shape may also be used. When such a light diffusing material 152 is used, the average particle diameter r of the light diffusing material 152 is preferably 1 μm or more and not more than the width W1 of the first surface 15a that becomes the image source side end of the diffusion portion 15, from the viewpoint of preferably diffusing the light incident on the diffusion portion 15 and sufficiently filling the diffusion portion 15.

[0041] Also, at this time, the ratio W1 / r of the average particle diameter r of the light diffusing material 152 to the width W1 of the first surface 15a of the diffusion portion 15 is preferably 1 or more and 5 or less from the viewpoint of sufficiently filling the diffusion portion 15 with the light diffusing material 152. Also, at this time, the width W1 of the first surface 15a of the diffusion part 15 is preferably larger than the average particle diameter r of such particulate light diffusing material 152 and is 3 μm or more and 20 μm or less.

[0042] The second base material layer 16 is a layer located on the back side of the second light transmission part 14 and the diffusion part 15, has light transmissivity, and has a function of protecting the diffusion part 15 and the second light transmission part 14. As the second base material layer 16, a sheet-like member or the like similar to the aforementioned first base material layer 11 can be used.

[0043] Since the screen 10 has the configuration as described above, by diffusing the video image at the diffusion part 15 and directing a part of it toward the video source side (+Z side), the video image can be displayed to the observer O. Further, when the screen 10 does not have the low refractive index layer 13, the video light that would otherwise pass through the screen 10 can also be made to enter the diffusion part 15, improving the utilization efficiency of the video light, and a bright and high-contrast good video image can be displayed. Also, since the screen 10 has the configuration as described above, when the screen 10 does not have the low refractive index layer 13, the video light that passes through the screen 10 is made to enter the diffusion part 15, diffused, and emitted to the back side. Therefore, the projection image onto the ceiling, objects located on the back side of the screen 10, etc. caused by the video light passing through the screen 10 can be reduced.

[0044] FIG. 4 is a diagram for explaining the traveling direction of the light incident on the screen 10 of the present embodiment. The cross-section of the screen 10 shown in FIG. 4 is the same as the cross-section of the screen 10 shown in FIG. 2 described above. The video lights L1 and L2 projected from the video source LS located below the video source side (+Z side) of the screen 10 enter the screen 10 and enter through the first base material layer 11 and the first light transmission part 12. The image light L1 passes through the first light transmission part 12 and is incident on the second surface 12b of the first light transmission part 12. The second surface 12b is the interface between the first light transmission part 12 and the low refractive index layer 13. The image light L1 is incident on the second surface 12b at an angle equal to or greater than the critical angle and undergoes total internal reflection. Then, the image light L1 is incident on the diffusion part 15 and is diffused. Also, the image light L2 passes through the first light transmission part 12 and is incident directly on the diffusion part 15 from the third surface 15c of the diffusion part 15 without undergoing total internal reflection at the interface with the low refractive index layer 13, and is diffused. Also, although not shown in the figure, there is also image light that is incident directly on the diffusion part 15 from the first surface 15a of the diffusion part 15 and is diffused.

[0045] These image lights L1 and L2 are diffusely scattered omnidirectionally by the light diffusing material 152 of the diffusion part 15, and a part is emitted to the back side (-Z side), and a part is emitted to the image source side (+Z side). In this way, an image visible to the observer O located on the image source side is displayed on the screen 10 by the image light diffused by the diffusion part 15 and emitted to the image source side. Also, although a part of the image light (not shown) is emitted to the back side, it is diffused, and the reflection of the projection image on the objects and people O2 on the back side and the ceiling is significantly suppressed.

[0046] Next, the light from the outside world such as sunlight other than the image light incident on the screen 10 from the back side (-Z side) or the image source side (+Z side) (hereinafter referred to as external light) will be described. The external light G2 incident on the screen 10 from the image source side (+Z side) at a small incident angle mostly enters the interface (the second surface 12b) between the first light transmission part 12 and the low refractive index layer 13 at an angle smaller than the critical angle, passes through the low refractive index layer 13, the second light transmission part 14, and the second base material layer 16, and is emitted to the back side of the screen 10.

[0047] Similarly, the external light G1 that enters the screen 10 at a small incident angle from the back side (-Z side) passes through the second base material layer 16 and the second light transmission part 14, and enters the interface (the second surface 14b) between the second light transmission part 14 and the low refractive index layer 13 at an angle smaller than the critical angle. And most of the external light G2 passes through the low refractive index layer 13, passes through the first light transmission part 12 and the first base material layer 11, and is emitted to the video source side of the screen 10. As described above, since most of the external lights G1 and G2 do not enter the diffusion part 15, they pass through the screen 10 without being diffused. Also, a part (not shown) of the external light that enters the screen at a small incident angle like the external lights G1 and G2 enters the diffusion part 15, is diffused, passes through the screen 10, or returns to the back side or the video source side, but the amount of this light is small.

[0048] Therefore, the screen 10 of the present embodiment has transparency such that the observer O on the video source side of the screen 10 and the observer O2 on the back side can favorably visually recognize the scenery (transmitted image) on the other side through the screen 10. In addition, the screen 10 of the present embodiment can suppress the transmitted image (transmitted image) on the other side observed through the screen 10 from appearing blurred or whitened, and can also suppress a decrease in the contrast of the image due to external light or the like.

[0049] Next, the external light G3 that enters the screen 10 from above on the video source side will be described. Among the external lights that enter from above the screen 10 on the video source side, a part of the external light G3 enters the interface between the first light transmission part 12 and the low refractive index layer 13 at an angle smaller than the critical angle as shown in FIG. 4, passes through the low refractive index layer 13, the second light transmission part 14, and the second base material layer 16, and is emitted to the lower part on the back side of the screen 10.

[0050] Among the external light incident from above the screen 10 on the video source side, a part of the external light (not shown) passes through the low refractive index layer 13 and then enters the first surface 14a of the second light transmission part 14 (the second surface 15b of the diffusion part 15), and is diffused by the diffusion part 15. However, most of it exits to the back side of the screen 10, and the amount of light traveling toward the video source side is small. Therefore, a decrease in the contrast of the video due to external light incident from above the video source side is suppressed.

[0051] Regarding the external light incident from above on the back side, when it enters the diffusion part 15 and is diffused, it becomes a factor in reducing the contrast of the video and the transparency of the screen 10. Therefore, it is preferable to place the screen 10 in a location where such external light from above the back side does not enter, or to provide a shade or the like for the purpose of blocking the external light incident from above the back side to the screen 10.

[0052] As described above, according to the present embodiment, a low refractive index layer 13 having a lower refractive index than the first light transmission part 12 and the second light transmission part 14 is formed between adjacent diffusion parts 15, and the interface (the second surface 12b) between the first light transmission part 12 and the low refractive index layer 13 forms an angle θ2 with respect to the thickness direction of the screen 10, and serves as a total reflection surface where the video light is incident at an angle equal to or greater than the critical angle and undergoes total reflection. As a result, the video light that would exit to the back side of the screen 10 and cause the projected image to be reflected on the ceiling or the like in the case where the low refractive index layer 13 is not provided can be more effectively incident on the diffusion part 15 and diffused, and the effect of suppressing the projected image from being reflected on the ceiling or the object or person located on the back side on the back side can be significantly enhanced.

[0053] Further, according to the present embodiment, by providing the low refractive index layer 13 between adjacent diffusion parts 15, the arrangement pitch P1 of the diffusion parts 15 can be increased as compared with the case where the low refractive index layer 13 is not provided. Thereby, the diffraction phenomenon that easily occurs when the arrangement pitch P1 is small can be suppressed, and the blurring of the transmitted video when looking through the screen 10 can be suppressed. Further, thereby, while maintaining the optical performance of the screen 10, the thickness can be reduced, and the transparency can also be improved. In addition, according to the present embodiment, since most of the external light (external light G1, G2 shown in FIG. 4) with a small incident angle on the screen 10 passes through the screen 10 without being diffused, the transparency of the screen 10 can be maintained at a high level.

[0054] As described above, according to the present embodiment, the screen 10 has transparency and can display a good image that is bright and has high contrast. Further, according to the present embodiment, it is possible to significantly suppress the projection image from being reflected on the ceiling on the back side, objects or people located on the back side, etc., and improve the design and comfort of the space where the video display device 1 is arranged.

[0055] (Modification) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the scope of the present invention. (1) In the embodiment, an example is shown in which the diffusion part 15 has an isosceles trapezoidal cross-sectional shape in a cross-section parallel to the arrangement direction (Y direction) of the first light transmission part 12 and the thickness direction (Z direction) of the screen 10. However, the present invention is not limited to this, and a trapezoidal shape that is asymmetric in the arrangement direction may be used. For example, in the arrangement direction (Y direction) of the diffusion part 15, one of the upper (+Y side) surface or the lower (-Y side) surface of the diffusion part 15 may have a trapezoidal shape parallel to the thickness direction (Z direction) of the screen 10. Further, in the embodiment, the diffusion part 15 may have a polygonal shape other than a trapezoidal shape, and may have a polygonal shape such as a rectangular shape or a pentagonal shape. Further, in the embodiment, the cross-sectional shape of the diffusion part 15 may be such that the first surface 15a on the video source side is inclined with respect to the arrangement direction (Y direction). Further, in the embodiment, a part of the diffusion part 15 may be formed by a curved surface, or a part of it may have a folded surface shape. In addition, the angles θ3 and θ1 formed by the second surface 15b and the third surface 15c of the diffusion part 15 with the thickness direction (Z direction) of the screen 10 may be continuously or stepwise changed at least one of them in the arrangement direction (Y direction) of the diffusion part 15.

[0056] (2) In the embodiment, the diffusion part 15 is shown with an example of a trapezoidal shape in which the width in the video source side (+Z side) (dimension in the Y direction) is smaller than the width in the back side (-Z side) (dimension in the Y direction) in the cross-sectional shape shown in FIG. 2. However, it is not limited to this. For example, the cross-sectional shape shown in FIG. 2 may be a trapezoidal shape in which the width in the video source side (+Z side) (dimension in the Y direction) is larger than the width in the back side (-Z side) (dimension in the Y direction), or may be a triangular shape with the back side as the apex. Even in such a form, the same effects as the screen 10 of the embodiment can be achieved.

[0057] (3) In the embodiment, an example in which the arrangement pitch P1 of the diffusion part 15 is constant is shown. However, it is not limited to this. For example, in the arrangement direction (Y direction), as it moves away from the video source LS, the arrangement pitch P1 may be continuously or stepwise increased. By adopting such a form, the video light can be made to enter the diffusion part 15 more efficiently.

[0058] (4) In the embodiment, the low refractive index layer 13 may be an air layer.

[0059] (5) In the embodiment, the angle θ2 formed by the low refractive index layer 13 with the thickness direction (Z direction) of the screen 10 may be continuously or stepwise increased as it moves away from the video source LS in the arrangement direction (vertical direction of the screen, Y direction) of the low refractive index layer 13. The incident angle of the video light on the screen increases as it goes upward in the vertical direction of the screen. Therefore, by adopting such a form, the video light incident on the screen 10 can be made to enter the diffusion part 15 more efficiently.

[0060] (6) In an embodiment, a hard coat layer for the purpose of preventing damage may be provided on the surface of the screen 10 on the video source side (+Z side). The hard coat layer is formed, for example, by applying an ultraviolet curable resin (such as urethane acrylate, etc.) having a hard coat function on the surface of the screen 10 on the video source side (the surface of the first base material layer 11 on the video source side). Note that the method of forming the hard coat layer is not limited to this. Also, the first base material layer 11 may have a hard coat function. Moreover, not limited to the hard coat layer, depending on the usage environment and purpose of the screen 10, etc., for example, one or more layers having necessary functions such as an antireflection function, an ultraviolet absorption function, an antifouling function, an antistatic function, etc. may be appropriately selected and provided. Further, a touch panel layer or the like may be provided on the video source side (observer side) of the first base material layer 11. Note that the layer having the above functions is not limited to the surface of the screen 10 on the video source side (the surface of the first base material layer 11 on the video source side), and may also be laminated and provided on the back surface side (the back surface side of the second base material layer 16). Also, a coloring layer for setting a predetermined amount of transmitted light or improving the contrast of the video may be provided in the screen 10. Such a coloring layer is, for example, dark transparent such as black, and has a function of transmitting a part of the incident light and absorbing a part of it.

[0061] (7) In an embodiment, the screen 10 may be in a form that does not include at least one of the first base material layer 11 and the second base material layer 16. Also, in an embodiment, the screen 10 may have at least one of the first base material layer 11 and the second base material layer 16 as a plate-like member made of a resin such as acrylic or a plate-like member having light transmissivity such as a glass plate. At this time, other layers may be joined to the glass plate or the like through an adhesive layer or the like. Also, for example, the screen 10 may be in a form that uses a transparent substrate instead of the first base material layer 11 and the second base material layer 16 and is joined thereto. Examples of such a transparent substrate include a plate-like member made of a highly transparent resin and a glass plate.

[0062] (8) In the embodiment, the video display device 1 has been shown as an example to be arranged in a store window such as a store, but it is not limited thereto. For example, it can also be applied to indoor partitions, video displays at exhibitions, etc. Further, the video display device 1 may be applied to vehicles such as cars and ships, and the screen 10 may be used by being attached to a window glass, an internal partition, etc.

[0063] (9) In the embodiment, the diffusion part 15 may be in a form that further contains a dark coloring material such as black or gray in addition to the light diffusing material 152. By adopting such a form, a part of the transmitted video light can be absorbed to reduce the projection image reflection on the people or objects located on the back side of the screen 10, or the external light from the back side can be absorbed to improve the contrast of the video displayed on the screen 10.

[0064] (10) In the embodiment, an example in which the diffusion part 15 is formed by the binder material 151 containing the light diffusing material 152 has been shown, but it is not limited thereto. The diffusion part 15 may be formed by filling only the light diffusing material 152.

[0065] (11) In the embodiment, an example in which the video source LS is arranged below (-Y side) the screen 10 in the vertical direction (Y direction) has been shown, but it is not limited thereto. For example, the video source LS may be in a form located above (+Y side) the screen 10 in the vertical direction. In this case, the position of the video source LS in the vertical direction is made to correspond to the point C that is the Fresnel center, and the screen 10 is used with its vertical direction reversed. Further, the video source LS may be in a form located on the right side or the left side of the screen 10 in the horizontal direction (X direction). Also in this case, the position of the video source LS in the horizontal direction is made to correspond to the point C that is the Fresnel center, and the screen 10 is used by rotating its vertical direction 90° to the left or right.

[0066] Note that although the present embodiment and the modified forms can be used in appropriate combination, detailed description thereof will be omitted. Also, the present invention is not limited to the embodiments described above and the like.

Explanation of Reference Numerals

[0067] 1 Video display device 10 Screen 11 First base material layer 12 First light transmission part 13 Low refractive index layer 14 Second light transmission part 15 Diffusion part 151 Binder material 152 Light diffusing material LS Video source

Claims

1. A reflective screen that visibly displays image light projected from an image source to an observer, having a function of diffusing at least a part of incident light, a diffusion part arranged along the screen surface, a first light transmission part provided between adjacent said diffusion parts, a second light transmission part provided between adjacent said diffusion parts and on the back side of said first light transmission part, a low refractive index layer provided between said first light transmission part and said second light transmission part, inclined at a predetermined angle with respect to the thickness direction of the reflective screen and having a refractive index lower than that of said first light transmission part, comprising, said diffusion part contains a light diffusing material for diffusing light, said diffusion part, has a fourth surface that is the back side surface, in a cross section parallel to the arrangement direction of said diffusion parts and the thickness direction of the reflective screen, when the dimension of said fourth surface in the arrangement direction of said diffusion parts is W2 and the dimension of said diffusion part in the thickness direction of the reflective screen is h1, h1 > W2, the angle formed by said low refractive index layer with the thickness direction of the reflective screen is larger than the angle formed by the image light incident on said first light transmission part with the thickness direction of the reflective screen, characterized by a reflective screen.

2. A reflective screen that visibly displays image light projected from an image source to an observer, having a function of diffusing at least a part of incident light, a diffusion part arranged along the screen surface, a first light transmission part provided between adjacent said diffusion parts, a second light transmission part provided between adjacent said diffusion parts and on the back side of said first light transmission part, a low refractive index layer provided between said first light transmission part and said second light transmission part, inclined at a predetermined angle with respect to the thickness direction of the reflective screen and having a refractive index lower than that of said first light transmission part, comprising, said diffusion part contains a light diffusing material for diffusing light, said diffusion part, has a first surface that is the image source side surface and a fourth surface that is the back side surface, in a cross section parallel to the arrangement direction of said diffusion parts and the thickness direction of the reflective screen, when the dimension of said fourth surface in the arrangement direction of said diffusion parts is W2 and the dimension of said diffusion part in the thickness direction of the reflective screen is h1, h1 > W2, when the dimension of said first surface in the arrangement direction of said diffusion parts is W1 and the average particle diameter of said light diffusing material is r, the ratio W1 / r is 1 or more and 5 or less, characterized by a reflective screen.

3. In the reflective screen according to claim 2, the angle formed by the low refractive index layer with the thickness direction of the reflective screen is greater than the angle formed by the video light incident on the first light transmission portion with the thickness direction of the reflective screen, characterized in that it is a reflective screen.

4. In the reflective screen according to claim 1 or claim 2, the diffusion portion has a first surface that is the surface on the video source side, in a cross-section parallel to the arrangement direction of the diffusion portion and the thickness direction of the reflective screen, the cross-sectional shape of the diffusion portion is a trapezoidal shape, the dimension of the first surface in the arrangement direction of the diffusion portion is smaller than the dimension of the fourth surface in the arrangement direction of the diffusion portion, characterized in that it is a reflective screen.

5. In the reflective screen according to claim 1 or claim 2, the diffusion portion has a second surface and a third surface that face each other in the arrangement direction of the diffusion portion, when the angles formed by the second surface and the third surface with the thickness direction of the reflective screen are angle θ3 and angle θ1 respectively, θ3 = θ1 is satisfied, characterized in that it is a reflective screen.

6. In the reflective screen according to claim 1 or claim 2, the arrangement pitch of the diffusion portion is 100 to 1000 μm, characterized in that it is a reflective screen.

7. In the reflective screen according to claim 1 or claim 2, the average particle diameter of the light diffusing material is 1 μm or more, characterized in that it is a reflective screen.

8. In the reflective screen according to claim 1, the diffusion portion has a first surface that is the surface on the video source side, the average particle diameter of the light diffusing material is equal to or less than the dimension of the first surface in the arrangement direction of the diffusion portion, characterized in that it is a reflective screen.

9. In the reflective screen according to claim 1 or claim 2, the video light is incident on the diffusion portion and diffused, and a part of it is emitted to the video source side and a part of it is emitted to the back side, characterized in that it is a reflective screen.

10. In the reflective screen according to claim 1 or claim 2, the first light transmission portion and the second light transmission portion have the same refractive index, characterized in that it is a reflective screen.

11. In the reflective screen according to claim 1 or claim 2, the diffusion portion is formed in a strip shape so as to extend in a first direction along the screen surface of the reflective screen, and is arranged in a second direction intersecting the first direction. The cross-sectional shape in a cross-section parallel to the second direction and the thickness direction of the reflective screen is a wedge shape. A reflective screen characterized by the above. **Claim 12** In the reflective screen according to Claim 1 or Claim 2, In addition to the diffusion part, there is no part containing a light diffusing material that diffuses light. A reflective screen characterized by the above. **Claim 13** In the reflective screen according to Claim 1 or Claim 2, The angle formed by the low refractive index layer with respect to the thickness direction of the reflective screen continuously or stepwise changes in the arrangement direction of the low refractive index layer. A reflective screen characterized by the above. **Claim 14** In the reflective screen according to Claim 1 or Claim 2, In the arrangement direction of the diffusion part, the arrangement pitch of the diffusion part continuously or stepwise changes. A reflective screen characterized by the above. **Claim 15** A video display device comprising: The reflective screen according to Claim 1 or Claim 2; and A video source that projects video light onto the reflective screen.

Images