Reflective screens, video display devices

Abstract

To provide a reflection type screen having a good viewing angle in right and left directions of the screen and a video display device.SOLUTION: A screen 10 is a reflection type screen, and includes: a light diffusion layer 11 for diffusing light; a reflection layer 13 positioned on a back surface side of the light diffusion layer 11 in a thickness direction of the screen 10; and a light control layer 12 located between the light diffusion layer 11 and the reflection layer 13. The light control layer 12 is formed by integrally laminating a first layer 121 positioned on an observer side and a second layer 122 positioned on the back surface side in a thickness direction of the screen 10. The first layer 121 and the second layer 122 have refractive index difference. In an interface of the first layer 121 and the second layer 122, a plurality of unit optical shapes 123 are formed and arranged whose arrangement direction is horizontal directions of the screen and a longitudinal direction is a vertical direction of the screen.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a reflective screen and a video display device.

Background Art

[0002] Conventionally, a reflective screen that reflects video light projected from a video source such as a projector and displays a video on a screen (display surface), and a video display device including the same are known (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] Generally, in various video display devices, it is preferable that the viewing angle in the horizontal direction of the screen is wider than the viewing angle in the vertical direction of the screen. In the screen shown in Patent Document 1, the video light is diffused by providing a translucent diffusing base material. Since the diffusing action of this translucent diffusing base material is non-directional and the video light diffuses in the vertical direction of the screen as well as in the horizontal direction, the utilization efficiency of the video light decreases and the brightness of the video also decreases. In a reflective screen, it has always been required to display a bright video with high front luminance.

[0005] An object of the present invention is to provide a reflective screen and a video display device having a good viewing angle in the horizontal direction of the screen.

Means for Solving the Problems

[0006] The present invention solves the above-mentioned problems by the following means. For the sake of ease of understanding, the embodiments of the present invention will be described using reference numerals corresponding to those numerals, but the invention is not limited thereto. The first invention is a reflective screen (10) that displays an image by reflecting image light projected from an image source, comprising: a light diffusion layer (11) that diffuses light; a reflective layer (13) located on the back side of the light diffusion layer in the thickness direction of the reflective screen; and a light control layer (12) located between the light diffusion layer and the reflective layer, wherein the light control layer is formed by integrally laminating a first layer (121) located on the observer side and a second layer (122) located on the back side in the thickness direction of the reflective screen, the first layer and the second layer have a refractive index difference, and a plurality of unit optical shapes (123) are arranged at the interface between the first layer and the second layer, with the left-right direction of the screen as the arrangement direction and the up-down direction of the screen as the longitudinal direction. The second invention is a reflective screen (10) of the first invention, characterized in that the refractive index (n1) of the first layer (121) is greater than the refractive index (n2) of the second layer (122). The third invention is a reflective screen (10) of the first invention, characterized in that the light diffusion layer (11) is a layer in which the light-transmitting base resin contains a diffusing material having a refractive index difference from the base resin. The fourth invention is a reflective screen (10) of the first invention, characterized in that the cross-sectional shape of the unit optical shape (123) in a cross section parallel to the arrangement direction of the unit optical shape (123) and the thickness direction of the reflective screen is a curved shape that is convex towards the back side. The fifth invention is an image display device (1) comprising a reflective screen (10) from any of the first to fourth inventions, and an image source (LS) that projects image light onto the reflective screen. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a reflective screen and an image display device having a suitable viewing angle in the left-right direction of the screen. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating the video display device 1 of an embodiment. [Figure 2] This is a diagram illustrating the layer configuration of the screen 10 in the embodiment. [Figure 3] This figure illustrates other shapes of the unit optical shape 123 in the embodiment. [Figure 4] This figure shows the state of the image light on the screen 10 of the embodiment. [Figure 5] This figure shows the layer configuration of the screens in the reference example, embodiment, and comparative example in the simulation. [Figure 6] This figure shows the shape when the cross-sectional shape of unit optical shape 123 is a curved shape that is convex on the back side (-Z side). [Figure 7] This figure shows the shape when the cross-sectional shape of the unit optical shape 123 is triangular. [Figure 8] This figure shows the shape when the cross-sectional shape of unit optical shape 123 is a curved shape with a concave shape on the back side (-Z side). [Figure 9] This graph shows the simulation results (luminance distribution) on the screen for measurement example 61, which is a reference example. [Figure 10] This graph shows the simulation results (luminance distribution) on the screens for measurement examples 1 to 5, which are examples of the implemented data. [Figure 11] This graph shows the simulation results (luminance distribution) on the screen for measurement examples 6-10, which are examples of the implemented data. [Figure 12] This graph shows the simulation results (luminance distribution) on the screen for measurement examples 11-15, which are examples of the implemented data. [Figure 13] This graph shows the simulation results (luminance distribution) on the screen for measurement examples 16-20, which are examples of the implemented data. [Figure 14]It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 21 to 25 which are examples. [Figure 15] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 26 to 30 which are examples. [Figure 16] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 31 to 35 which are comparative examples. [Figure 17] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 36 to 40 which are comparative examples. [Figure 18] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 41 to 45 which are comparative examples. [Figure 19] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 46 to 50 which are comparative examples. [Figure 20] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 51 to 55 which are comparative examples. [Figure 21] It is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 55 to 60 which are comparative examples. [Figure 22] It is a diagram showing the relationship between the front luminance and the angle θ for each shape of the unit optical shape 123, and the angle θ and αH which is the half angle in the left - right direction of the screen, on the screens of Measurement Examples 1 to 15 which are examples. [Figure 23] It is a diagram showing the relationship between the front luminance and the angle θ for each shape of the unit optical shape 123, and the angle θ and αH which is the half angle in the left - right direction of the screen, on the screens of Measurement Examples 16 to 30 which are examples. [Figure 24] It is a diagram showing the relationship between the front luminance and the angle θ for each shape of the unit optical shape 123, and the angle θ and αH which is the half angle in the left - right direction of the screen, on the screens of Measurement Examples 31 to 45 which are comparative examples. [Figure 25] It is a diagram showing the relationship between the front luminance and the angle θ for each shape of the unit optical shape 123, and the angle θ and αH which is the half angle in the left - right direction of the screen, on the screens of Measurement Examples 46 to 60 which are comparative examples. [Figure 26] This table summarizes the simulation results for the screens in measurement examples 1 to 10. [Figure 27] This table summarizes the simulation results for the screens used in measurement examples 11-20. [Figure 28] This table summarizes the simulation results for the screens used in measurement examples 21-30. [Figure 29] This table summarizes the simulation results for the screens used in measurement examples 31-40. [Figure 30] This table summarizes the simulation results for the screens used in measurement examples 41-50. [Figure 31] This table summarizes the simulation results for the screens used in measurement examples 51-60. [Figure 32] This figure shows the layer configuration of the screen used to measure the speckle value. [Figure 33] This table shows the measurement results of speckle values ​​on screens 1-4 and the results of the visual evaluation of image glare. [Figure 34] This diagram illustrates the layer structure of the deformed screen 20. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings and other figures. Note that the following figures, including Figure 1, are schematic representations, and the size and shape of each part have been exaggerated as appropriate for ease of understanding. In this specification, terms used to specify shapes and geometric conditions, such as parallel and orthogonal, are used not only in their strict sense but also to include states that exhibit similar optical functions and have an error that can be considered parallel or orthogonal. The dimensions and other numerical values, as well as material names, for each component described herein are merely examples of embodiments and are not limited thereto; they may be selected and used as appropriate.

[0010] Furthermore, while this specification uses terms such as "board" and "sheet," these terms are generally used in the order of increasing thickness: board, sheet, and film, and this specification follows that convention. However, there is no technical significance to this distinction, and these terms can be substituted as appropriate.

[0011] (Embodiment) Figure 1 is a diagram illustrating the video display device 1 of this embodiment. Figure 1(a) is a perspective view of the video display device 1, and Figure 1(b) is a side view of the video display device 1 (a side view seen from the +X side, which will be described later). The video display device 1 includes a screen 10, a video source LS, etc. The screen 10 in this embodiment is a reflective screen that reflects projected video light and displays an image on its screen (display surface). The video display device 1 projects video light from the video source LS onto the screen 10, and the screen 10 reflects the video light L to display an image on its screen (display surface), thereby displaying an image to the observer O.

[0012] For ease of understanding, the following figures, including Figure 1, use an XYZ Cartesian coordinate system as appropriate. In this coordinate system, the left-right direction 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 (display surface) of the screen 10 is parallel to the XY plane, and the thickness direction (Z direction) of the screen 10 is perpendicular to the screen surface of the screen 10. From the perspective of an observer O positioned in front of screen 10, the direction to the right in the left-right direction is the +X direction, the direction upward in the up-down direction is the +Y direction, and the direction from the back side (rear side) towards the observer side (image source side) in the thickness direction is the +Z direction.

[0013] In this embodiment, the screen 10 is positioned such that, in its usage state, the vertical direction (Y direction) of the screen is vertical and the horizontal direction (X direction) of the screen is horizontal. In the following description, unless otherwise specified, the vertical direction, horizontal direction, and thickness direction of the screen refer to the vertical direction, horizontal direction, and depth direction of the screen 10 in its usage state, and are assumed to be parallel to the Y direction, X direction, and Z direction, respectively. Furthermore, in this embodiment, the screen surface refers to the plane of the screen 10 when viewed as a whole, and in the usage state of the screen 10, the screen surface is a plane parallel to the XY plane.

[0014] The image source LS is an image light projection device that projects image light L onto the screen 10. In this embodiment, the image source LS is a general-purpose projector. The video source LS, in its operational state, is positioned at a predetermined distance from the observer, passing through point A, which is the geometric center (center of the screen) of the screen (display area) of the screen 10, and along the direction of the normal to the screen surface of the screen 10.

[0015] Screen 10 is a screen that reflects the image light L projected by the image source LS toward the observer O and displays an image on the screen. The screen (display area) of screen 10, when viewed from the observer O side (image source side) in its usage state, is approximately rectangular in shape, with the longer side being the left-right direction of the screen (X direction) and the shorter side being the up-down direction of the screen (Y direction). Screen 10 has a large screen with a diagonal size of approximately 40 to 100 inches and an aspect ratio of 16:9. However, the screen size of Screen 10 is not limited to this; for example, it may be less than 40 inches or greater than 100 inches, and its size and shape can be appropriately selected according to the purpose of use and the environment in which it is used.

[0016] The screen 10 may be configured to maintain its flatness by having a support plate (not shown) on its rear side. Suitable support plates include plate-shaped members made of resin, metal, wood, glass, etc. The screen 10 may also be configured to maintain its flatness by having at least two opposing sides supported by a support member (not shown). Furthermore, the screen 10 is not limited to the above configuration, and may be configured to be retractable and flexible, so that when not in use it can be rolled up and stored in a designated box or the like (not shown), and when in use it can be rolled up and suspended along a wall surface by a support member or the like (not shown).

[0017] Figure 2 illustrates the layer configuration of the screen 10 in this embodiment. Figure 2(a) is an enlarged view of a portion of the cross-section (YZ cross-section) that passes through point A (see Figures 1(a) and (b)), which is the geometric center (center of the screen) of the screen (display area) of the screen 10, and is parallel to the vertical direction of the screen (Y direction) and the direction perpendicular to the screen surface (thickness direction, Z direction). Figure 2(b) is an enlarged view of a portion of the cross-section (XZ cross-section) that passes through point A (see Figures 1(a) and (b)), which is the geometric center (center of the screen) of the screen (display area) of the screen 10, and is parallel to the horizontal direction of the screen (X direction) and the direction perpendicular to the screen surface (Z direction).

[0018] As shown in Figure 2, the screen 10 comprises, in its thickness direction, a light diffusion layer 11, a light control layer 12, and a reflective layer 13, in that order from the observer side (+Z side). The light diffusion layer 11 is a layer that has an omnidirectional diffusion effect. This light diffusion layer 11 uses a light-transmitting resin as the base resin and contains particulate diffusing material having a refractive index difference from the base resin. Examples of suitable base resins include PET (polyethylene terephthalate) resin, PC (polycarbonate) resin, MS (methyl methacrylate-styrene) resin, MBS (methyl methacrylate-butadiene-styrene) resin, TAC (triacetylcellulose) resin, PEN (polyethylene naphthalate) resin, and acrylic resins.

[0019] Suitable diffusers for the light-diffusing layer 11 include resin particles such as acrylic resins, styrene resins, epoxy resins, and silicone resins, as well as inorganic particles such as glass beads. In addition, a combination of inorganic and organic diffusers may be used. The diffuser is preferably spherical or nearly spherical, with an average particle size of approximately 1 to 50 μm, and more preferably 2 to 10 μm. Furthermore, the refractive indices of both the base resin and the diffuser of the light diffusion layer 11 are preferably around 1.48 to 1.65. The difference in refractive index between the base resin and the diffuser is preferably 0.01 to 0.10, and more preferably 0.01 to 0.03. The base resin and the diffuser may be configured so that one has a higher refractive index than the other. The thickness of the light diffusion layer 11 is preferably about 10 to 2000 μm, although this depends on the screen size of the screen 10. Furthermore, it is desirable that the haze value of the light diffusion layer 11 be in the range of 70 to 95%.

[0020] The optical control layer 12 is a layer that primarily functions to spread the image light in the left-right direction of the screen. This optical control layer 12 is located on the back side (-Z side) of the optical diffusion layer 11. The light control layer 12 is formed by integrally laminating a first layer 121 and a second layer 122. In the thickness direction of the screen 10, the first layer 121 is located on the observer side (+Z side), and the second layer 122 is located on the back side (-Z side).

[0021] The first layer 121 is a layer formed of a light-transmitting resin, and multiple unit optical shapes 123 are arranged on its back surface (the interface with the second layer 122). The unit optical shapes 123 are arranged in multiples in the left-right direction (X direction) of the screen, with the vertical direction (Y direction) of the screen being the longitudinal direction (extension direction). In this embodiment, in the cross-section shown in Figure 2(b), the cross-sectional shape of the unit optical shape 123 is a curved shape that is convex towards the back side. Furthermore, it is preferable that the cross-sectional shape of this unit optical shape 123 shown in Figure 2(b) is symmetrical in the left-right direction (X direction) of the screen.

[0022] In the cross-section of the optical control layer 12 shown in Figure 2(b), the angle θ that the straight line passing through point t1, which is on the back side (-Z side) of the unit optical shape 123, and point t2, which is on the observer side (+Z side), makes with the plane parallel to the screen surface (XY plane) may be set appropriately according to the desired optical performance of the screen 10. For example, if you want a screen 10 that has a wide viewing angle in the left-right direction while also having high front brightness, then a smaller angle θ is preferable. Conversely, if you want a screen 10 that has a wider viewing angle in the left-right direction than its front brightness, then a larger angle θ is preferable.

[0023] The second layer 122 is made of a light-transmitting resin and is located on the back side (-Z side) of the first layer 121. On the observer-side (+Z side) surface of the second layer 122, multiple second unit optical shapes 124, which are the inverse of the unit optical shape 123, are arranged and formed. As described above, since the first layer 121 and the second layer 122 are laminated together, multiple unit optical shapes 123 and second unit optical shapes 124 are arranged and formed at the interface between the first layer 121 and the second layer 122. The second layer 122 makes the back surface of the light control layer 12 planar.

[0024] Figure 3 illustrates another shape of the unit optical shape 123 in this embodiment. In Figure 3, a magnified view of a portion of the cross-section of the optical control layer 12 parallel to the arrangement direction of the unit optical shapes 123 (i.e., the left-right direction of the screen, the X direction) and the thickness direction of the screen 10 (the Z direction) is shown. As shown in Figure 3(a), the unit optical shape 123 may have a triangular cross-sectional shape. In this case, it is preferable that the cross-sectional shape of the unit optical shape 123 is an isosceles triangle. Furthermore, as shown in Figure 3(b), the unit optical shape 123 may have a curved cross-sectional shape that is concave with respect to the back side. In this case, the second unit optical shape 124 has a curved cross-sectional shape that is convex towards the observer side (+Z side). In any of the unit optical shapes 123 shown in Figures 3(a) and 3(b), it is preferable that the cross-sectional shape is symmetrical in the left-right direction of the screen (X direction). Also, as shown in Figures 3(a) and 3(b), in any of the unit optical shapes 123, the angle that the line passing through point t1, which is on the far back side (-Z side), and point t2, which is on the observer side (+Z side), makes with the plane parallel to the screen surface (XY plane) is angle θ.

[0025] Returning to Figure 2, the first layer 121 and the second layer 122 have a refractive index difference. In this embodiment, we will explain using an example where the refractive index n1 of the first layer 121 is greater than the refractive index n2 of the second layer 122, but the embodiment is not limited to this, and the refractive index n2 of the second layer 122 may be greater than the refractive index n1 of the first layer 121.

[0026] The reflective layer 13 is a layer that reflects light. In this embodiment, an example in which the reflective layer 13 is planar will be given for explanation. The reflective layer 13 can be formed, for example, by vapor deposition, sputtering, or transfer of highly light-reflective metals such as aluminum, silver, or nickel. Alternatively, the reflective layer 13 can also be formed by applying and curing a paint containing particles or fine flakes of the aforementioned highly light-reflective vapor-deposited metal or metal foil using various coating methods such as spray coating, die coating, screen printing, or groove filling by wiping. Furthermore, the reflective layer 13 can also be formed by applying and curing a white paint or a resin containing white pigments or beads using various coating methods. The reflective layer 13 only needs to have a thickness sufficient to reflect light adequately, and its thickness can be appropriately selected depending on the materials used.

[0027] Figure 4 shows the state of the image light in the screen 10 of this embodiment. Figure 4 schematically shows a portion of the cross-section of the screen 10 parallel to the left-right direction (X direction) and the thickness direction (Z direction). The image source LS in this embodiment is a general-purpose projector as described above, and the incident angles in the vertical and horizontal directions of the screen are smaller compared to short-throw projectors and the like. The image light projected from the image source LS enters the screen 10 at an incident angle of approximately 0° to 45° relative to the screen surface in the vertical direction (Y direction). After being diffused in the light diffusion layer 11, it passes through the light control layer 12, is reflected by the reflection layer 13, passes through the light control layer 12 again, is diffused in the light diffusion layer 11, and is emitted towards the observer.

[0028] Furthermore, in the left-right direction (X direction) of the screen, as shown in Figure 4, the image light incident on the screen 10, for example, image light L1, L3, L5, is incident on the unit optical shape 123, and either does not refract at the interface between the first layer 121 and the second layer 122, or is refracted and passes through the second layer 122, and is reflected by the reflection layer 13. Subsequently, as with image light L2, L4, L6, again does not refract at the interface between the first layer 121 and the second layer 122, or is refracted and passes through the first layer 121, is incident on the light diffusion layer 11, undergoes an omnidirectional diffusion effect, and is emitted towards the observer. In other words, the image light incident on the screen 10 is diffused appropriately in the left-right direction of the screen, mainly due to the diffusion effect of the light diffusion layer 11, as well as the refractive index difference at the interface between the first layer 121 and the second layer 122 of the light control layer 12 and the shape of the unit optical shape 123. Therefore, according to this embodiment, the light control layer 12 can diffuse the image light in the left-right direction of the screen, thereby ensuring a sufficient viewing angle in the left-right direction of the screen.

[0029] Furthermore, since the light diffusion layer 11 has an omnidirectional light diffusion effect, the image light is also diffused in the vertical direction (Y direction) of the screen. As a result, the screen 10 of this embodiment can ensure a sufficient viewing angle in the vertical direction of the screen. Furthermore, the image light incident on the screen 10 is diffused twice by the light diffusion layer 11, before and after reflection by the reflective layer 13. In the screen 10, a light control layer 12 is located between the light diffusion layer 11 and the reflective layer 13, which allows for a longer optical path length between diffusion in the light diffusion layer 11 and subsequent diffusion. As a result, the screen 10 of this embodiment can reduce image glare (also called speckle or scintillation).

[0030] Furthermore, if the screen 10 does not have a light control layer 12, for example, in order to ensure a sufficient viewing angle in the left-right direction (X direction) of the screen using only the light diffusion layer 11, it is necessary to increase the content of the diffusing material in the light diffusion layer 11 or increase the refractive index difference between the base resin and the diffusing material. However, screens of this type have problems such as increased black brightness in the image, making the image appear whitish, or the image becoming darker, or the image resolution decreasing, resulting in a decrease in image quality. However, since the screen 10 of this embodiment is equipped with a light control layer 12, it is possible to display bright, high-resolution, and good images while ensuring a sufficient viewing angle in the left-right direction (X direction) of the screen.

[0031] Furthermore, in this embodiment, the screen 10 has the light diffusion layer 11 positioned closer to the observer (+Z side) than the light control layer 12. This allows at least a portion of the image light to be diffused before it enters the light control layer 12. Therefore, when the screen 10 has a configuration in which the first layer 121 has a higher refractive index than the second layer 122, the amount of light totally reflected at the interface between the first layer 121 and the second layer 122 can be reduced, and unwanted brightness peaks (so-called side peaks) that occur outside the viewing angle range can be reduced.

[0032] (Evaluation of viewing angle in the left-right direction and front brightness of the screen) Here, using optical simulation, the luminance distribution and other parameters were measured for the screens of Measurement Examples 1 to 60, which correspond to the examples and comparative examples of the screen 10 of this embodiment, and for the screen of Measurement Example 61, which serves as a reference example, and the 1 / 2 angle of peak luminance and front luminance were evaluated. FIG. 5 is a diagram showing the layer configuration of the screens of the examples, comparative examples, and reference examples in the simulation. In FIG. 5, a part of the cross section of the screens of the examples, comparative examples, and reference examples is shown, and for the sake of easy understanding, the shape of the unit optical shape 123 of the light control layer 12 is shown in an omitted manner. As shown in FIG. 5(a), the screens of measurement examples 1 to 30, which are examples of the screen 10 of the present embodiment, include a surface layer 14, a light diffusion layer 11, a light control layer 12, and a reflection layer 13 in order from the observer side along the thickness direction of the screen 10. As shown in FIG. 5(b), the screens of measurement examples 31 to 60, which correspond to the screen 10B of the comparative example, include a surface layer 14, a light control layer 12, a light diffusion layer 11, and a reflection layer 13 in order from the observer side along the thickness direction of the screen.

[0033] As shown in FIG. 5(c), the screen of measurement example 61, which corresponds to the screen 10C of the reference example, does not include the light control layer 12, and includes a surface layer 14, a light diffusion layer 11, and a reflection layer 13 in order from the observer side along the thickness direction of the screen. In this simulation, the screens of all measurement examples are in a form having the surface layer 14 on the most observer side (+Z side). This is for making the refractive indexes of the layers on the most observer side of the screen the same. The surface layer 14 is a layer having light transmissivity and the surface on the observer side is a smooth planar shape and does not have the effect of diffusing light.

[0034] In the simulation, for the refractive index n1 of the first layer 121 and the refractive index n2 of the second layer 122 of the light control layer 12, two cases of n1>n2 and n1<n2 are set. The magnitude relationship between the refractive indexes of the two layers in each measurement example is as follows. In the screens of measurement examples 1 to 15 (examples) and measurement examples 31 to 45 (comparative examples), the refractive index n1 of the first layer 121 is greater than the refractive index n2 of the second layer 122, and n1 = 1.65 and n2 = 1.48. In the screens of measurement examples 16 to 30 (examples) and measurement examples 46 to 60 (comparative examples), the refractive index n1 of the first layer 121 is smaller than the refractive index n2 of the second layer 122, and n1 = 1.48 and n2 = 1.65.

[0035] Furthermore, in the simulation, three different cross-sectional shapes were set for the unit optical shape 123 of the optical control layer 12. In the screens of measurement examples 1-5, 16-20 (examples) and measurement examples 31-35, 46-50 (comparative examples), the cross-sectional shape of unit optical shape 123 is a curved shape that is convex towards the back side (see Figure 2(b)). In the screens of measurement examples 6-10, 21-25 (Examples) and measurement examples 36-40, 51-55 (Comparative Examples), the cross-sectional shape of the unit optical shape 123 is triangular (see Figure 3(a)). In the screens of measurement examples 11-15, 26-30 (Examples) and comparative examples 41-45, 55-60 (Comparative Examples), the cross-sectional shape of the unit optical shape 123 is a curved shape that is concave on the back side (see Figure 3(b)).

[0036] Furthermore, for the three cross-sectional shapes of the above-mentioned unit optical shape 123, five examples were set for the angle θ that the line connecting point t1, which is on the back side of the unit optical shape 123, and point t2, which is on the observer side, makes with a plane parallel to the screen surface: 15°, 30°, 45°, 60°, and 75°. In the screens used in measurement examples 1, 6, 11, 16, 21, and 26 (Examples) and measurement examples 31, 36, 41, 46, 51, and 56 (Comparative Examples), the angle θ = 15°. In the screens used in measurement examples 2, 7, 12, 17, 22, and 27 (Examples) and measurement examples 32, 37, 42, 47, 52, and 57 (Comparative Examples), the angle θ = 30°. In the screens used in measurement examples 3, 8, 13, 18, 23, and 28 (Examples) and measurement examples 33, 38, 43, 48, 53, and 58 (Comparative Examples), the angle θ = 45°. In the screens of measurement examples 4, 9, 14, 19, 24, and 29 (Examples) and measurement examples 34, 39, 44, 49, 54, and 59 (Comparative Examples), the angle θ = 60°. In the screens of measurement examples 5, 10, 15, 20, 25, and 30 (Examples) and measurement examples 35, 40, 45, 50, 55, and 60 (Comparative Examples), the angle θ = 75°.

[0037] Figure 6 shows the shape of the unit optical shape 123 when its cross-sectional shape is curved and convex on the back side (-Z side). Figure 6(a) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 15° (screens for measurement examples 1, 16, 31, and 46), and Figure 6(b) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 30° (screens for measurement examples 2, 17, 32, and 47). Figure 6(c) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 45° (screens for measurement examples 3, 18, 33, and 48), and Figure 6(d) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 60° (screens for measurement examples 4, 19, 34, and 49). Figure 6(e) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 75° (screens for measurement examples 5, 20, 35, and 50).

[0038] Figure 7 shows the shape of the unit optical shape 123 when its cross-sectional shape is triangular. Figure 7(a) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 15° (screens for measurement examples 6, 21, 36, and 51), and Figure 7(b) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 30° (screens for measurement examples 7, 22, 37, and 52). Figure 7(c) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 45° (screens for measurement examples 8, 23, 38, and 53), and Figure 7(d) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 60° (screens for measurement examples 9, 24, 39, and 54). Figure 7(e) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 75° (screens for measurement examples 10, 25, 40, and 55).

[0039] Figure 8 shows the shape of the unit optical shape 123 when its cross-sectional shape is curved with a concave shape on the back side (-Z side). Figure 8(a) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 15° (screens for measurement examples 11, 26, 41, and 56), and Figure 8(b) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 30° (screens for measurement examples 12, 27, 42, and 57). Figure 8(c) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 45° (screens for measurement examples 13, 28, 43, and 58), and Figure 8(d) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 60° (screens for measurement examples 14, 29, 44, and 59). Figure 8(e) shows the cross-sectional shape of the unit optical shape 123 when the angle θ = 75° (screens for measurement examples 15, 30, 45, and 60).

[0040] For unit optical shapes 123, regardless of their shape, the array pitch in the left-right direction (X direction) of the screen is the same and is 0.03 mm. Furthermore, for the unit optical shapes 123 whose cross-sectional shape is convex and concave relative to the back side (-Z side), the cross-sectional shape was approximated by setting seven points on the XZ plane and connecting these points with straight lines, as shown in Figures 6 and 8. These seven points are the point t1 on the back side of the cross-sectional shape of the unit optical shape 123 (see Figure 2(b), etc.), the two points at both ends in the arrangement direction of the unit optical shape 123, the two points between point t1 and one end, and the two points between point t1 and the other end. Furthermore, for the unit optical shape 123 with a triangular cross-sectional shape, as shown in Figure 7, three points were set on the XZ plane, and the points were connected by straight lines. These three points are the point t1 on the furthest back side of the unit optical shape 123, and the two points at both ends in the direction of arrangement of the unit optical shape 123.

[0041] Furthermore, the surface layer 14, light diffusion layer 11, and reflective layer 13, which are common to all measurement examples, were set as follows. The refractive index of the surface layer 14 is 1.55. The refractive index of the base resin of the light diffusion layer 11 is 1.595. Furthermore, when light is incident on the light diffusion layer 11 at an incident angle of 0°, the emission angle at which the light passes through the light diffusion layer 11 and exits is 0°, and the angle at which the brightness is half of the peak brightness (half angle) in the vertical and horizontal directions of the screen is ±20°. In the simulation, the light diffusion layer 11 was set as a diffusing surface, without considering its thickness. The reflective layer 13 has a total ray reflectance of 70% for light incident at an incident angle of 0°. Optical simulations were performed on all the screens in the measurement examples described above using LightTools (Synopsys), and the angular distribution of brightness in the vertical direction (Y direction) and horizontal direction (X direction) of the screen was measured.

[0042] Figure 9 is a graph showing the simulation results (luminance distribution) on the screen of measurement example 61, which is a reference example. In Figure 9, the vertical axis represents normalized luminance, and the horizontal axis represents the emission angle (°) from the screen in the left-right and up-down directions, passing through point A, which is the center of the screen. In the graph shown in Figure 9 and in the graphs shown in Figures 10 to 21 described later, the normalized luminance on the vertical axis is normalized with the peak luminance of the screen in the reference example, Measurement Example 61, set to 100. The peak luminance of the screen in Measurement Example 61 is the average value of the luminance at polar angles from 0 to 1° and azimuth angles from 0 to 360°, when the polar angle direction is divided into 90° segments at 1° intervals and the azimuth angle direction into 36 segments at 10° intervals, with the polar angle and azimuth angle set to the central axis with the direction perpendicular to the screen surface (normal direction of the screen surface) passing through point A, which is the center of the screen in Measurement Example 61.

[0043] Figure 10 is a graph showing the simulation results (luminance distribution) on the screens for measurement examples 1 to 5, which are examples of the actual implementation. Figure 11 is a graph showing the simulation results (luminance distribution) on the screen for measurement examples 6 to 10, which are examples of the actual implementation. Figure 12 is a graph showing the simulation results (luminance distribution) on the screen for measurement examples 11 to 15, which are examples of the actual implementation. Figure 13 is a graph showing the simulation results (luminance distribution) on the screen for measurement examples 16-20, which are examples of the actual implementation. Figure 14 is a graph showing the simulation results (luminance distribution) on the screen for measurement examples 21-25, which are examples of the actual implementation. Figure 15 is a graph showing the simulation results (luminance distribution) on the screen for measurement examples 26-30, which are examples of the actual implementation. In the graphs of luminance distribution for each measurement example shown in Figures 10 to 15, the vertical axis represents the normalized luminance, with the peak luminance of the screen in measurement example 61 (a reference example) set to 100, as described above, and the horizontal axis represents the emission angle (°).

[0044] Figure 16 is a graph showing the simulation results (luminance distribution) on the screen for comparative examples 31-35. FIG. 17 is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 36 to 40 which are comparative examples. FIG. 18 is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 41 to 45 which are comparative examples. FIG. 19 is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 46 to 50 which are comparative examples. FIG. 20 is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 51 to 55 which are comparative examples. FIG. 21 is a graph showing the simulation results (luminance distribution) on the screens of Measurement Examples 55 to 60 which are comparative examples. In the graphs of the luminance distributions of each measurement example shown in FIGS. 16 to 21, the vertical axis is the normalized luminance with the peak luminance of the screen of Measurement Example 61 which is a reference example being 100 as described above, and the horizontal axis is the emission angle (°).

[0045] FIG. 22 is a diagram showing the relationship between the front luminance for each shape of the unit optical shape 123 and the angle θ, and the angle θ and αH which is the half angle in the left - right direction of the screen, on the screens of Measurement Examples 1 to 15 which are examples. On the screens of Measurement Examples 1 to 15, the refractive index of the first layer 121 is larger than the refractive index of the second layer 122 (n1>n2), and the light control layer 12 is located on the back side (-Z side) of the light diffusion layer 11. FIG. 23 is a diagram showing the relationship between the front luminance for each shape of the unit optical shape 123 and the angle θ, and the angle θ and αH which is the half angle in the left - right direction of the screen, on the screens of Measurement Examples 16 to 30 which are examples. On the screens of Measurement Examples 16 to 30, the refractive index of the first layer 121 is smaller than the refractive index of the second layer 122 (n1<n2), and the light control layer 12 is located on the back side (-Z side) of the light diffusion layer 11.

[0046] FIG. 24 is a diagram showing the relationship between the front luminance and the angle θ for each shape of the unit optical shape 123 in the screens of Measurement Examples 31 to 45 which are comparative examples, and the angle θ and αH which is the half angle in the left - right direction of the screen. In the screens of Measurement Examples 31 to 45, the refractive index of the first layer 121 is larger than the refractive index of the second layer 122 (n1>n2), and the light control layer 12 is located on the observer side (+Z side) of the light diffusion layer 11. FIG. 25 is a diagram showing the relationship between the front luminance and the angle θ for each shape of the unit optical shape 123 in the screens of Measurement Examples 46 to 60 which are comparative examples, and the angle θ and αH which is the half angle in the left - right direction of the screen. In the screens of Measurement Examples 46 to 60, the refractive index of the first layer 121 is smaller than the refractive index of the second layer 122 (n1<n2), and the light control layer 12 is located on the observer side (+Z side) of the light diffusion layer 11.

[0047] FIGS. 22(a), 23(a), 24(a), and 25(a) are graphs showing the relationship between the front luminance and the angle θ. The vertical axis represents the front luminance obtained from the above - mentioned simulation results, and the horizontal axis represents the angle θ (°). The front luminance on the vertical axis is the average value of the luminance at an emission angle of 0° in the left - right direction and the up - down direction of the screen, and is shown as a value normalized with the peak luminance of the screen of Measurement Example 1 which is a reference example set to 100. FIGS. 22(b), 23(b), 24(b), and 25(b) are graphs showing the relationship between αH which is the half angle in the left - right direction of the screen and the angle θ. The vertical axis represents αH (°), and the horizontal axis represents the angle θ (°). The half angle αH in the left - right direction (X direction) of the screen is the average value of the absolute values of the half angles on the +X side and the -X side in the X direction. In the graphs shown in FIGS. 22 to 25, the angle θ on the horizontal axis is the angle θ formed by the straight line passing through the point t1 which is the most back side (-Z side) and the point t2 which is the most observer side (+Z side) of the unit optical shape 123 in the cross - section of the light control layer 12 shown in FIG. 2(b), FIGS. 3(a), and (b) above, and the plane (XY plane) parallel to the screen surface.

[0048] FIG. 26 is a table summarizing the simulation results in the screens of Measurement Examples 1 to 10. Figure 27 is a table summarizing the simulation results for the screens in measurement examples 11 to 20. Figure 28 is a table summarizing the simulation results for the screens in measurement examples 21 to 30. Figure 29 is a table summarizing the simulation results for the screens in measurement examples 31 to 40. Figure 30 is a table summarizing the simulation results for the screens in measurement examples 41 to 50. Figure 31 is a table summarizing the simulation results for the screens in measurement examples 51-60.

[0049] The tables in Figures 26 to 31 show the shape of the unit optical shape 123 in the screen for each measurement example, as well as the relationship between the refractive indices of the first layer 121 and the second layer 122, the angle θ, etc. In Figures 26 to 31, αH, which is the half angle in the left-right direction of the screen (X direction), is the average of the absolute values ​​of the half angle on the +X side and the half angle on the -X side, and αV, which is the half angle in the up-down direction of the screen (Y direction), is the average of the absolute values ​​of the half angle on the +Y side and the half angle on the -Y side. Although not shown in Figures 26 to 31, in the screen of measurement example 61, which is a reference example, both the half angle αH in the left-right direction of the screen and the half angle αV in the up-down direction of the screen are 20°.

[0050] As shown in Figures 9 to 31, in the screens of measurement examples 1 to 60 (examples and comparative examples), regardless of the cross-sectional shape of the unit optical shape 123, as the angle θ increases, the frontal brightness (brightness in the 0° direction) decreases and the 1 / 2 angle αH in the left-right direction of the screen increases. However, in the comparative example, the screens of measurement examples 31 to 60, where the light control layer 12 is located closer to the observer (+Z side) than the light diffusion layer 11, when the angle θ increases, brightness peaks, so-called side peaks, appear in diagonal directions symmetrical with respect to the front direction (emission angle 0° direction) in the left-right direction of the screen. These side peaks appear when the angle θ increases, regardless of the relative refractive indices of the first layer 121 and the second layer 122, or the shape of the unit optical shape 123.

[0051] Such side peaks, especially in the case of a large-screen display, are factors that cause bright and dark regions in the screen to be observed as thick vertical stripes (band-like) when the screen is viewed obliquely. Such bright and dark stripes lead to a deterioration in the quality of the screen, which is not preferable. Also, side peaks may occur in an unnecessary direction outside the assumed viewing angle range of the screen, which is not preferable from the perspective of light utilization efficiency.

[0052] On the other hand, in the screens of Measurement Examples 1 to 30, which are examples and in which the light control layer 12 is located on the back side of the light diffusion layer 11, as the angle θ increases, the front luminance (luminance in the 0° direction) decreases and the luminance distribution becomes smoother, and the viewing angle becomes wider. However, regardless of the shape of the unit optical shape 123, no side peaks occur. Also, as shown in FIGS. 10 to 15, in the screen of the example, when emphasizing the height of the front luminance rather than the width of the viewing angle in the horizontal direction of the screen, a screen with a small angle θ can be selected, and when emphasizing the width of the viewing angle in the horizontal direction of the screen rather than the height of the front luminance, a screen with a large angle θ can be selected. Also, as shown in FIGS. 22 and 23, in the screen of the example, the viewing angle and the front luminance can also be controlled by the magnitude relationship between the refractive index n1 of the first layer 121 and the refractive index n2 of the second layer 122. For example, when n1 > n2, the width of the viewing angle in the horizontal direction of the screen can be increased, and when n1 < n2, the front luminance can be increased.

[0053] Therefore, according to the present embodiment, without considering the occurrence of side peaks, etc., from the screens of Measurement Examples 1 to 30, which are examples, according to the desired optical performance, the shape of the unit optical shape 123, the angle θ, the magnitude relationship between the refractive indices of the first layer 121 and the second layer 122, etc. can be selected, and the degree of freedom in the design of the screen 10 can be increased.

[0054] (Evaluation regarding video flicker) Furthermore, screens corresponding to the example's screen (Sample 1 and Sample 2) and the comparative example's screen (Sample 3 and Sample 4) were prepared, and their speckle values ​​were measured using a measuring instrument. Figure 32 shows the layer structure of the screen of a sample for measuring speckle value. In Figure 32, a cross-section parallel to the vertical direction of the screen and parallel to the thickness direction of the screen is shown. Figure 32(a) shows the layer structure of the screen of samples 1 and 2, which correspond to the example, and Figure 32(b) shows the layer structure of the screen of samples 3 and 4, which correspond to the comparative example.

[0055] The screens of Samples 1 and 2, which correspond to the examples, consist of a surface layer 14, a light diffusion layer 11, a light control layer 12, a lens layer 16, and a reflective layer 13, in that order from the observer side, with the light diffusion layer 11 located on the observer side (+Z side) of the light control layer 12. The screens of samples 3 and 4, which correspond to the comparative examples, consist of a surface layer 14, a light control layer 12, a light diffusion layer 11, a lens layer 16, and a reflective layer 13, in that order from the observer side, with the light diffusion layer 11 located on the back side (-Z side) of the light control layer 12.

[0056] In the screens of Samples 1 to 4, the cross-sectional shape of the unit optical shape 123 in the optical control layer 12 is triangular, and the angle θ is 45°. In the screens of samples 1 and 3, the refractive index of the first layer 121 is greater than that of the second layer 122, while in the screens of samples 2 and 3, the refractive index of the first layer 121 is smaller than that of the second layer 122.

[0057] In other words, the screen of Sample 1 corresponds to the screen of Measurement Example 8, the screen of Sample 2 corresponds to the screen of Measurement Example 23, the screen of Sample 3 corresponds to the screen of Measurement Example 38, and the screen of Sample 4 corresponds to the screen of Measurement Example 53. The screen of Measurement Example 8 and the screen of Measurement Example 38 are similar in terms of peak brightness and brightness distribution in the left-right direction of the screen, as shown in Figures 11(c) and 17(c) above. Also, the screen of Measurement Example 23 and the screen of Measurement Example 53 are similar in terms of peak brightness and brightness distribution in the left-right direction of the screen, as shown in Figures 14(c) and 20(c) above.

[0058] In measuring speckle values, if the direction of light projected from the image source LS and incident on each sample screen is coaxial with the direction of light incident on the measuring instrument (reflected light from each sample screen), measurement cannot be performed with the measuring instrument. Therefore, in the screens of samples 1 to 4, the reflective layer 13 is formed on the back side of the lens layer 16. This lens layer 16 has multiple unit lenses 161 arranged vertically on the screen, with the screen's left-right direction as its longitudinal direction, on the back side (-Z side). Multiple unit lenses 161 of the same shape are arranged in the direction of their arrangement. Furthermore, as shown in Figure 32, the unit lenses 161 have a triangular cross-sectional shape and have a first slope 162 and a second slope 163.

[0059] Furthermore, in the unit lens 161, the first inclined plane 162 is located above the second inclined plane 163 in the vertical direction of the screen. The angle θa that the first inclined plane 162 makes with a plane parallel to the screen surface is smaller than the angle θb that the second inclined plane 163 makes with a plane parallel to the screen surface. Also, angle θa is 20°, angle θb is 90°, and the vertex angle θc of the unit lens 161 is 70°. As a result, the light projected from the image source LS (the light used for speckle measurement), located below the screen of each sample, is incident on the first slope 162, reflected, and directed towards the front of the screen of each sample.

[0060] The other layer configurations common to screens 1-4 are as follows: The light diffusion layer 11 is a layer (sheet-like member) that has diffusion characteristics such that when light is incident on the light diffusion layer 11 at an incident angle of 0° and passes through the light diffusion layer 11 and is emitted, the emission angle (half angle) at which the brightness is half of the maximum brightness (in the direction of emission angle 0°) is ±7°. The lens layer 16 is formed of urethane acrylate resin and has a refractive index of 1.55. The reflective layer 13 is formed by spraying a paint containing flake-shaped aluminum metal thin films using a spray gun, and has a total light reflectance of 50% at an incident angle of 0°. The screen size is 100mm x 100mm.

[0061] The speckle value S is a value that serves as an indicator for evaluating the glare of an image, and is calculated using the following formula (1). Equation (1)... S[%]=100×σ[cd / m 2 ] / M[cd / m 2 ] In equation (1), σ represents the standard deviation of the luminance at each measurement point when a predetermined color image (white, red, green, or blue) is displayed on the screen of each sample. The measurement area is defined as a range of 30 mm vertically and 30 mm horizontally around the center of the screen of each sample. Line segments with a pitch of 133 μm are drawn in the vertical and horizontal directions of the screen within this measurement area, and the intersections of these line segments are used as measurement points. In equation (1), M represents the average value of the luminance at the aforementioned measurement points when a predetermined color image (white, red, green, or blue) is displayed.

[0062] From the perspective of suppressing image glare while maintaining sufficient frontal brightness, it is desirable that the speckle value S be 7.0% or less for all white, red, green, and blue images. If the speckle value S is greater than 7.0%, image glare will be visible, which is undesirable.

[0063] This speckle value S was obtained in a darkroom environment by placing the measuring instrument (Dr.SPECKLE / SM01VS09 manufactured by Oxide Co., Ltd.) at a position 1000 mm away from the center of the screen (geometric center of the screen) of each sample, on the observer side (+Z side) in the direction normal to the screen surface. Furthermore, the image source LS (Hisense 75L9S) was positioned 800 mm below the center of each sample's screen (-Y side) and 500 mm towards the observer (+Z side) along the normal direction of the sheet surface, projecting white, red, green, and blue light. As a result, white, red, green, and blue images were displayed on each sample's screen.

[0064] Furthermore, in a darkroom environment, the observer visually evaluated the glare of the image from a position 1000 mm away from the center of each sample's screen, in the direction of the normal to the screen surface, towards the observer (+Z side). During the visual evaluation, the image light projected onto each sample's screen from the image source LS consisted of white light, red light, green light, and blue light. White, red, green, and blue images were displayed, and the observer evaluated the glare of each color image. The position of the image source LS was the same as when the speckle value was measured.

[0065] Figure 33 is a table showing the measurement results of the speckle value S for screens 1-4 and the results of the visual evaluation of image glare. The speckle value S tends to be highest for red images compared to white, green, and blue images. Therefore, the table in Figure 33 shows the speckle value S when displaying red images. Figure 33 also shows the results of the visual evaluation of image glare using red images. The measurement results of the speckle value S when the screens of Samples 1 to 4 displayed red images, and the evaluation results of the glare of the images as visually assessed by observers viewing each color image, are as follows.

[0066] On the screen of Sample 1, the speckle value S was less than 7.0% when displaying white, blue, and green images, and 7.0% when displaying a red image. Furthermore, in the visual evaluation of image glare, the screen of Sample 1 exhibited weak glare, regardless of the color of the displayed image, and was almost imperceptible. In Sample 2, the speckle value S was less than 7.0% when displaying white, blue, and green images, while the speckle value S was 7.0% when displaying a red image. Furthermore, in the visual evaluation of image glare, the screen in Sample 2 exhibited weak glare, regardless of the color of the displayed image, and was almost imperceptible.

[0067] In Sample 3, the speckle value S was 7.0% or less when displaying white, blue, and green images, but it was 7.9% when displaying a red image. Furthermore, in a visual evaluation of image glare, the Sample 3 screen was usable with white, blue, and green images, although the glare was weakly visible, but the glare was strongly visible with the red image. In the Sample 4 screen, the speckle value S was 7.0% or less when displaying white, blue, and green images, but the speckle value S was 7.6% when displaying a red image. Furthermore, in the visual evaluation of image glare, the Sample 4 screen was usable with white, blue, and green images, although the glare was weakly visible, but the glare was strongly visible with red images.

[0068] As described above, in the example screens Sample 1 and 2, the speckle value S was 7.0% or less, and image glare was reduced. On the other hand, in the comparative example screens Sample 3 and 4, the speckle value S exceeded 7.0%, and image glare was visible. Therefore, according to this embodiment, by positioning the light diffusion layer 11 closer to the observer than the light control layer 12, image glare can be reduced.

[0069] Based on the above, this embodiment provides a reflective screen 10 and an image display device 1 with a good viewing angle in the left-right direction (X direction) of the screen. Furthermore, according to this embodiment, the shape and angle θ of the unit optical shape 123 of the light diffusion layer 11, and the relationship between the refractive indices of the first layer 121 and the second layer 122 can be appropriately selected according to the desired optical performance, allowing for free screen design without worrying about the occurrence of side peaks. Furthermore, according to this embodiment, the distance between the light diffusion layer 11 and the reflective layer 13 in the thickness direction (Z direction) of the screen can be increased, thereby reducing glare in the image. Furthermore, according to this embodiment, the viewing angle in the left-right direction of the screen can be widened without increasing the amount of diffusing material contained in the light diffusion layer 11, the black brightness of the image can be sufficiently reduced, and the resolution of the image can be maintained.

[0070] (Transformed form) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the scope of the present invention.

[0071] (1) In one embodiment, the screen may be a screen 20 that includes a lens layer 24 having a Fresnel lens shape with a plurality of unit lenses 241 arranged on the back side between the light control layer 12 and the reflective layer 13. Figure 34 illustrates the layer structure of the deformed screen 20. Figure 34 shows a cross-section of the screen 20 that passes through the center of the screen and is parallel to the arrangement direction of the unit lenses 241 and the thickness direction (Z direction) of the screen 20. This lens layer 24 has a circular Fresnel lens shape on its back surface, and has a circular Fresnel lens shape in which multiple unit lenses 241 are arranged concentrically around a point located outside the display area of ​​the screen 10. If the lens layer 24 is viewed from the direction normal to the screen surface on the back side (-Z side), the unit lenses 241 appear to be a partial shape of a perfect circle (arc-shaped), and multiple such arrangements are observed.

[0072] The reflective layer 23 is preferably formed on at least a portion of the lens surface 241a of the unit lens 241. Figure 34 shows a configuration in which the reflective layer 23 is formed on both the lens surface 241a and the non-lens surface 241b. The reflective layer 23 can be formed using the same materials and manufacturing methods as those used to form the reflective layer 13 in the above embodiments. Alternatively, a reflective layer may be formed only on the lens surface 241a, and a light-absorbing layer or the like may be provided on the back side of the reflective layer 23, thereby forming a light-absorbing layer on the non-lens surface 241b. This configuration allows for the absorption of unwanted stray light and ambient light, resulting in a better image.

[0073] A screen 20 equipped with such a lens layer 24 and reflective layer 23 is suitable for image sources LS such as a short-throw projector that is located below the observer side of the screen 20 and projects image light at an angle, or an ultra-short-throw projector that projects image light from a position closer in the depth direction than a short-throw projector. Furthermore, in the lens layer 24, when the image source LS is positioned below and outside the display area of ​​the screen 20, it is preferable that the center point of the circular Fresnel lens shape is located outside the screen (outside the display area) of the screen 20, in the center of the screen 20 in the left-right direction, and below the screen 10.

[0074] Such an image source LS can project image light from a significantly closer position in the depth direction (Z direction) compared to conventional general-purpose projectors. Furthermore, with an ultra-short-throw projector, this distance can be reduced even further (for example, the depth distance from the image source LS to the screen 10 can be about 300 mm). When using conventional general-purpose projectors or general-purpose short-throw projectors as the image source, a distance of 1m to several meters or more was required between the image source and the reflective screen. This meant that people walking between the screen and the image source could obstruct the display of the image. Furthermore, a sufficiently large space was required to install the image source and screen at such a spacing. In contrast, if an ultra-short-throw projector is used as the image source LS, the distance between the image source LS and the screen 10 can be significantly reduced, thus resolving the above-mentioned problem.

[0075] (2) In one embodiment, the screen 10 may be provided with a layer on the observer side (+Z side) of the light diffusion layer 11 that has one or more functions as appropriate, such as an anti-reflective function, an anti-glare function, a hard coat function, an ultraviolet absorption function, an anti-fouling function, or an anti-static function. Furthermore, the screen 10 may be provided with a protective layer or the like on the back side (-Z side) of the reflective layer 13 to protect the reflective layer 13. Furthermore, the screen 10 may have a light-absorbing layer (not shown) on the back side of the reflective layer 13. By providing a light-absorbing layer, for example, ambient light incident from the back side can be absorbed, or image light and ambient light that have passed through the reflective layer 13 can be absorbed.

[0076] (3) In the embodiment, the unit optical shape 123 may have a flat portion between adjacent unit optical shapes. Alternatively, the unit optical shape 123 may have a planar top surface portion that is on the back side. Alternatively, the unit optical shape 123 may have both the flat portion and the top surface portion as described above. When the unit optical shape 123 has the top surface portion and the flat portion as described above, it is preferable to set the angle θ with point t1 being the center of the top surface portion and point t2 being the center of the flat portion. Furthermore, if the unit optical shape 123 has a triangular cross-sectional shape in a section parallel to its arrangement direction and the thickness direction of the screen 10, it may have a form in which both the apex that is convex towards the back side and the valley that is convex towards the observer side are curved. Furthermore, if the unit optical shape 123 has a cross-sectional shape that is convex towards the back side and a curved shape that is concave towards the back side in a cross-section parallel to its arrangement direction and the thickness direction of the screen 10, these shapes may be composed of multiple curves.

[0077] The embodiments and variations of this invention can be used in combination as appropriate, but a detailed explanation is omitted. Furthermore, the present invention is not limited to the embodiments described above. [Explanation of symbols]

[0078] 1. Video display device 10 screens 11 Light Diffusion Layer 12. Light control layer 121 The first layer 122 Second Layer 123 Unit Optical Shapes 124 Second Unit Optical Shape 13 Reflective layer

Claims

1. A reflective screen that displays an image by reflecting image light projected from an image source, A light-diffusing layer that diffuses light, A reflective layer located on the back side of the light diffusion layer in the thickness direction of the reflective screen, A light control layer located between the light diffusion layer and the reflection layer, Equipped with, The aforementioned light control layer is formed by integrally laminating a first layer located on the observer side and a second layer located on the back side in the thickness direction of the reflective screen. The refractive index of the first layer and the refractive index of the second layer have a refractive index difference. At the interface between the first layer and the second layer, a plurality of unit optical shapes are arranged and formed with the left-right direction of the screen as the arrangement direction and the up-down direction of the screen as the longitudinal direction. The aforementioned unit optical shape has a triangular cross-sectional shape in a cross-section parallel to its arrangement direction and the thickness direction of the reflective screen. In the cross-sectional shape of the unit optical shape, the angle θ formed by the straight line connecting the point on the back side of the unit optical shape and the point on the observer side with a plane parallel to the screen surface is 15° or more and 45° or less. A reflective screen characterized by the following features.

2. In the reflective screen described in claim 1, The refractive index of the first layer is higher than the refractive index of the second layer. A reflective screen characterized by the following features.

3. In the reflective screen described in claim 1, The light-diffusing layer is a layer in which a light-transmitting base resin contains a diffusing material having a refractive index difference from that of the base resin. A reflective screen characterized by the following features.

4. In the reflective screen described in Claim 1, The reflective layer has a flat surface on the observer's side. A reflective screen characterized by the following features.

5. A reflective screen according to any one of claims 1 to 4, A video source that projects video light onto the aforementioned reflective screen, A video display device equipped with the following features.

Images