Unit reflective face arrangement sheet for front-type screen, front-type screen and video display system

Abstract

To provide a unit reflective face arrangement sheet for front-type screens that achieves high productivity and uniform image brightness in an entire screen, and to provide a front-type screen equipped with the sheet and a video display system equipped with the screen.SOLUTION: A unit reflective face arrangement sheet 1 includes: a plurality of unit reflective faces 2 arranged in vertical and horizontal directions with a side length of 250 μm or less; and a focus F located at a focal distance f from a center O in an X direction, perpendicular to both vertical and horizontal directions. When vertical and horizontal lengths from the center O to the unit reflective face 2 are Y and X, respectively, and the vertical and horizontal reflection angles are θ and β, respectively, θ=arctan(Y / 2f) and β=arctan(X / 2f) are satisfied. Starting from the focus F, a principal ray of light reflected by the unit reflective face 2 is parallel to the direction perpendicular to both the vertical and horizontal directions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a unit reflecting surface array sheet for a front-type screen, a front-type screen having this unit reflecting surface array sheet, and a video display system including this screen and a video projection device.

[0002] Generally, screens for video display are roughly classified into a front type (also referred to as a reflection type) and a rear type (also referred to as a transmission type). A front-type screen is a screen that reflects, and preferably also diffuses, the video light from a video projection device on the front side of the screen and emits it to the front side. Among front-type screens with diffusion, there are a type that diffuses and reflects incident video light on the surface of the screen, and a type that diffuses on the surface and reflects it with an internal reflection layer. A display using a front-type screen is called a front-type display. On the other hand, a rear-type screen is a screen that transmits and diffuses the video light from a video projection device on the back side of the screen and emits it to the front side.

Background Art

[0003] Instead of the rear type in which the installation space for the video projection device behind the screen increases as the screen size increases, front-type displays that do not require the installation space behind the screen are becoming mainstream. Various forms of front-type screens used for this front-type display have been developed. For example, a screen of a spatial imaging iris surface method that can reflect and condense video light only at the location where the observer is present to achieve power saving and high brightness is known (see, for example, Patent Document 1). In this screen of the spatial imaging iris surface method, the reflecting surface is in the shape of a circular Fresnel lens in order to reflect and condense the video light from the video projection device.

[0004] Also known is a front-type screen in which the reflecting surface is in the shape of a linear Fresnel lens (see, for example, Patent Document 2).

[0005] The circular Fresnel lens has unit lenses arranged in a row on the circumference of concentric circles. In the front type screen with diffusion using this circular Fresnel lens, a diffusion film cut into leaf shapes in units of one sheet is used, and a circular Fresnel lens must be fabricated on the flat surface side by UV polymerization, which has the problem of low productivity for mass production.

[0006] On the other hand, as shown in FIG. 10, the linear Fresnel lens is fabricated by a specific method with a specific structure. Here, the mold 400 refers to a metal mold when manufacturing the resin linear Fresnel lens 100. In FIG. 10, (a) shows the appearance of the linear Fresnel lens, (b) shows the cross-section of the mold, and (c) shows a schematic diagram of the mold manufacturing method. Note that FIG. 10(a) is a view of the linear Fresnel lens 100 obliquely viewed from the front side, and the boundary of the reflecting surface 102 arranged on the back side and not appearing on the front side is shown by a dotted line.

[0007] As shown in FIG. 10, the vertical (Y-axis) direction, the horizontal (X-axis) direction, and the Z-axis direction orthogonal to both the vertical and horizontal directions are set (the same applies to the figures shown later). The concave-convex shape of the mold 400 (FIG. 10(b)) has a concave-convex inversion relationship with the concave-convex shape of the linear Fresnel lens 100 (FIG. 10(a)). The linear Fresnel lens 100 has a structure in which right-angled triangles △ABC are arranged linearly and parallel in the X-axis direction (FIG. 10(a)). The surface formed by the hypotenuse BC of the right-angled triangle △ABC becomes the reflecting surface 102, and the inclination angle of this reflecting surface 102 from the Y-axis becomes the Y-axis reflecting surface angle θ. The female mold part 102K of the reflecting surface 102 corresponds to the reflecting surface 102 (FIG. 10(a)) (FIG. 10(b)). On the other hand, since the surface formed by the side AC does not function optically, it is called the Y-axis unnecessary surface 103, and the Y-axis unnecessary surface angle (∠BAC) φ Y = 90° is desirable. The female mold part 103K of the Y-axis unnecessary surface 103 corresponds to the Y-axis unnecessary surface 103 (FIG. 10(a)) (FIG. 10(b)). However, in the vicinity of the center of the linear Fresnel lens in the Y-axis direction, the Y-axis unnecessary surface angle φ Y = 90°, but as the distance increases, the Y-axis unnecessary surface angle φ Yis less than 90°. The reason is that as the distance from the center in the Y-axis direction increases, the Y-axis reflection surface angle θ increases (Fig. 10(c)), and accordingly, the cutting surface of the diamond tool 50 (hereinafter also simply referred to as "tool") that serves as the ultra-precision cutting tool of the mold 400 must be tilted. Also, since the reflection surfaces 102 of the linear Fresnel lens 100 only have different Y-axis reflection surface angles θ, when explaining the planes on all the reflection surfaces in common, they will be described as the X-Yn plane. Here, Yn means that the Y-axis is tilted by the Y-axis reflection surface angle θ in the direction of the Z-axis at the nth Y position.

[0008] In Fig. 10(a), the X-Yn plane of the linear Fresnel lens 100 is taken as the reflection surface 102, and it is assumed that the reflection surface 102 is formed by continuously connecting minute reflection surfaces without steps at the boundaries. Using Fig. 11, the arrangement of the minute reflection surfaces 104 in the linear Fresnel lens 100 will be described. The minute reflection surfaces 104 are arranged so as to have the same optical characteristics as those of a general cylindrical mirror (Fig. 11(a)). On the Z-axis that is orthogonal to the Y-axis and passes through the X-axis center O, a focal point F (hereinafter also simply referred to as "focal point F") separated from the X-axis center O by the focal length f and a point 2F (hereinafter also simply referred to as "point 2F") separated from the X-axis center O by a distance 2f (= 2 × f) are set. The light emitted from the focal point F is reflected parallel to the X-Z plane passing through the incident point of the minute reflection surface 104 on the Y-axis, and the light from the point 2F returns to the point 2F. The linear Fresnel lens 100 has a lens function only in the Y-axis direction. On the other hand, since the minute reflection surfaces 104 are parallel in the X-axis direction (Fig. 11(b)) and the light from the focal point F and the point 2F is only reflected by the minute reflection surfaces 104 according to the law of reflection, the linear Fresnel lens 100 does not have a lens function in the X-axis direction. Also, the Y-axis reflection surface angle θ of the minute reflection surfaces 104 of the linear Fresnel lens 100 is θ = arctan(Y / 2f) represented by this (Fig. 11(a)). In Fig. 11(a), the Y-axis center is made to coincide with the X-axis center O.

[0009] The linear Fresnel lens is easy to manufacture by mold and can also convert the sheet manufacturing process into a highly productive casting process (roll-to-roll). Since the linear Fresnel lens 100 has a shape change in the vertical direction and no shape change in the horizontal direction (Fig. 11(b)), parallel light orthogonal to the X-Y plane passes through the focal point F on the Z axis and converges on a line parallel to the X axis (shown in Fig. 12). Therefore, it is used as an optical element for converging parallel light.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, when this linear Fresnel lens is used as the reflecting surface of a front-type screen, the reflected light in the Y-axis direction converges inside the front of the screen, but the reflected light in the X-axis direction spreads outside the front of the screen. As a result, the brightness of the images at both ends of the screen in the X-axis direction becomes extremely dark. In Patent Document 2, a technique is proposed in which the reflecting surface having a linear Fresnel lens shape is a semi-transmissive type, and a prism-shaped reflecting surface is arranged on the back side thereof such that the arrangement directions of the concavities and convexities of the former and the latter are orthogonal to each other to direct the reflected light in the X-axis direction inside the front of the screen. However, this proposed technique has a complicated manufacturing process because one of the two types of reflecting surfaces is formed on the front side and the other is formed on the back side, and there are difficulties in industrial productivity.

[0012] In view of the above problems, an object of the present invention is to provide a unit reflecting surface array sheet for a front-type screen that has high industrial productivity and can obtain uniform image brightness across the entire screen. Another object of the present invention is to provide a front-type screen including the sheet and a video display system including the screen.

Means for Solving the Problem

[0013] The inventor has repeatedly studied to solve the above problems and obtained the knowledge that it is effective to use a newly invented unit reflecting surface array sheet instead of a circular Fresnel lens and a linear Fresnel lens as the reflecting surface of a front-type screen. Based on this knowledge, the present invention having the following gist configuration has been made. 〔1〕A unit reflecting surface array sheet for a front-type screen in which a plurality of unit reflecting surfaces are arranged in the vertical and horizontal directions, having a focal point F at a focal length f from the center O in the horizontal direction in a direction orthogonal to both the vertical and horizontal directions, where the inclination angle θ of the unit reflecting surface from the vertical direction is θ = arctan(Y / 2f) when the length in the vertical direction from the center O to the unit reflecting surface is Y, and the inclination angle β of the unit reflecting surface from the horizontal direction is β = arctan(X / 2f) when the length in the horizontal direction from the center O to the unit reflecting surface is X, A unit reflecting surface array sheet for a front-type screen, characterized in that the principal ray of light starting from the focal point F and reflected by the unit reflecting surface is parallel to the direction orthogonal to both the vertical and horizontal directions. 〔2〕A front-type screen having the unit reflecting surface array sheet described in 〔1〕 above, characterized in that a metal layer is provided on the back surface of the unit reflecting surface array sheet. 〔3〕The front-type screen according to 〔2〕 above, characterized in that a surface shape diffusion film is provided on the front surface of the unit reflecting surface array sheet. 〔4〕The front-type screen according to 〔2〕 or 〔3〕 above, characterized in that image light from the position of the focal point F is reflected by the reflecting surface. 〔5〕Image light from a position approximately at a distance a from the screen surface of the front type screen is reflected by the reflecting surface to create a spatial imaging iris surface at a position approximately at a distance b from the screen surface, satisfying the relationship (1 / a) + (1 / b) = 1 / f. The front type screen according to 〔2〕 or 〔3〕 above is characterized by this. 〔6〕An image display system comprising the front type screen according to 〔4〕 or 〔5〕 above and an image projection device that projects image light onto the reflecting surface.

Advantages of the Invention

[0014] In the present invention, a unit reflecting surface array sheet different from both a circular Fresnel lens and a linear Fresnel lens is used to form the reflecting surface of the front type screen.

[0015] The above-mentioned problems in each of the circular Fresnel lens and the linear Fresnel lens are solved by the present invention.

[0016] According to the unit reflecting surface array sheet for the front type screen of the present invention, excellent effects such as improvement in the industrial productivity of the sheet and achievement of good image display can be achieved. According to the front type screen using the sheet, the reduction in the brightness of the images at both lateral ends of the displayed image is improved, the image quality is enhanced, and a screen excellent in portability and installability can be obtained. The image display system using the screen is useful for increasing the size of the display because the uniformity of the brightness of the displayed image is high and the image quality is excellent.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 3A

Figure 3B

Figure 3C

Figure 4

Figure 5

Figure 6

Figure 6A

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts as those in the above-mentioned figures are denoted by the same reference numerals, and the description thereof will be omitted. In addition, the drawings used below, including the above-mentioned drawings, are schematic drawings, and the sizes and shapes of each part are exaggerated as appropriate for easy understanding, and may not accurately represent the mutual relationship. Further, in this specification, terms for specifying shapes and geometric conditions, such as terms like parallel and orthogonal, include not only the strictly defined meanings but also aspects having errors that allow them to be regarded as parallel and orthogonal and exhibit similar optical functions.

[0019] [Unit Reflecting Surface Array Sheet for Front-Type Screen] [Plurality of Unit Reflecting Surfaces] As shown in FIG. 1, the unit reflecting surface array sheet 1 according to the present invention (hereinafter, also simply referred to as "the sheet of the present invention") exhibits an appearance in which a plurality of unit reflecting surfaces 2 are arranged in the vertical (Y-axis) direction and the horizontal (X-axis) direction. Note that FIG. 1 and FIG. 2(a) described later are views obliquely seen from the front side when the sheet of the present invention 1 is used as a screen, and the boundaries of the unit reflecting surfaces 2 arranged on the back side and not appearing on the front side are shown by dotted lines.

[0020] The unit reflecting surface 2 is preferably rectangular or parallelogram-shaped. Also, the unit reflecting surface 2 may be either a plane or a curved surface. Further, as boundaries of the unit reflecting surface 2, there are provided a step 3Y in the Y-axis direction and a step 3X in the X-axis direction. The steps 3Y and 3X have a peak which is the highest part and a valley which is the lowest part (the valleys are shown connected by a two-dot chain line) (see Fig. 1). The sheet 1 of the present invention is different from a linear Fresnel lens in that it has a step 3X in the X-axis direction that does not exist in the linear Fresnel lens (see Fig. 10(a)). Note that the Z-axis direction is a direction orthogonal to the X-Y plane. Since the sheet 1 of the present invention has steps 3X and 3Y, both the cross-section in the X-axis direction and the cross-section in the Y-axis direction have a sawtooth shape on the back side. Therefore, the sheet 1 of the present invention can be provided with a function of exhibiting lens performance of collecting light in both the Y-axis direction and the X-axis direction. Further, the sheet 1 of the present invention having such a sawtooth cross-sectional shape is preferably molded with a mold 40 for manufacturing the sheet of the present invention described later, and can be manufactured by an industrially simple method.

[0021] The unit reflecting surface 2 is a surface that reflects video light. On the other hand, the steps 3Y and 3X respectively form a Y-axis unnecessary surface and an X-axis unnecessary surface that do not function optically. As shown in Fig. 1, the heights (dimensions in the Z-axis direction) of the steps 3Y and 3X increase in proportion to the distance from the X-axis center O, and the respective heights are represented by the vertical length of the unit reflecting surface 2 × tanθ and the horizontal length × tanβ of the unit reflecting surface 2, where θ is the Y-axis reflecting surface angle and β is the X-axis reflecting surface angle (see Fig. 2 described later).

[0022] Note that if the length of the shortest side (the shortest side) of the unit reflecting surface 2 is less than 50 μm, the ratio of the reflecting surface to the steps 3X and 3Y becomes small, and a sufficient amount of reflection cannot be obtained, resulting in a dark video. On the other hand, if it exceeds 250 μm, the interval between the steps becomes large, and the steps can be discriminated by the human eye, which may cause a deterioration in the image quality of the displayed video. Therefore, the length of the shortest side of the unit reflecting surface 2 is preferably 50 to 250 μm. Further, from the manufacturing accuracy of the mold and the dimensional accuracy of the film used as the material of the sheet 1 of the present invention, the length of the shortest side of the unit reflecting surface 2 is more preferably 90 to 110 μm.

[0023] [Structure of the longitudinal (Y-axis) cross-section and the transverse (X-axis) cross-section of the sheet of the present invention] Figure 2 shows the appearance of the sheet 1 of the present invention (Figure 2(a)), the structure of the longitudinal (Y-axis) cross-section (Figure 2(b)), and the structure of the transverse (X-axis) cross-section (Figure 2(c)).

[0024] The arrangement of the unit reflecting surfaces 2 in the Y-axis direction at the X-axis center O (which may also be denoted as Xo) (Figure 2(b)) is the same as that in the case of a linear Fresnel lens. Also, since each unit reflecting surface 2 in the Y-axis direction only has a different Y-axis reflecting surface angle θ, when explaining the plane on all the unit reflecting surfaces in common, it can be described as the X-Yn plane. Here, Yn means an axis obtained by tilting the Y-axis by the Y-axis reflecting surface angle θn in the direction of the Z-axis at the position of the nth Y. The unit reflecting surfaces 2 in the X-axis direction form a sawtooth-like arrangement of the same shape determined by the X and Z values as shown in Figure 2(c) on the X-Yn plane. The shape of this sawtooth-like arrangement is symmetric with respect to the Y-Z plane passing through the X-axis center O. When manufacturing the sheet 1 of the present invention using the mold 40, as shown in Figure 1, the valley of the step of the sheet 1 of the present invention is used as a reference. Here, the "reference" corresponds to the position of the ridge (the surface to be cut of the mold material before cutting) of the mold 40 as will be described later.

[0025] The step 3X in the X-axis direction forms an X-axis unnecessary surface as the boundary of the unit reflecting surface 2 in the X-axis direction. The X-axis unnecessary surface does not function optically in the same way as the Y-axis unnecessary surface. The unit reflecting surface 2 has an X-axis reflecting surface angle β which is the inclination angle of the unit reflecting surface 2 with respect to the X-axis, and the X-axis unnecessary surface has an X-axis unnecessary surface angle δ X which is the inclination angle of the X-axis unnecessary surface with respect to the X-axis. In Figure 2, the subscripts b, m, and rc represent the lower end, the center in the longitudinal direction, and the center on the right side in the transverse direction in Figure 2, respectively.

[0026] [Optical characteristics of the sheet of the present invention] Next, the optical properties of the sheet 1 of the present invention will be described in detail. As shown in FIG. 2, the unit reflecting surfaces 2 of the sheet 1 of the present invention are arranged with steps 3Y and 3X in the Y-axis direction and the X-axis direction, respectively. Therefore, by controlling the height and inclination of the steps 3Y and 3X by setting the shape of the mold 40 so as to be the same as the optical properties of the spherical mirror, it becomes possible to add a lens function in the Y-axis and X-axis directions.

[0027] In the sheet 1 of the present invention, as shown in FIG. 4(a), a focal point F and a point 2F are set on the Z-axis passing through the X-axis center O. At this time, the light radiated from the focal point F is reflected by the unit reflecting surface 2 on the Y-axis, and the principal ray of the reflected light becomes parallel to the Z-axis. The "principal ray of the reflected light" corresponds to the ray that is the average value of the light flux starting from the focal point F and reflected by the unit reflecting surface 2. The principal ray of the reflected light starting from the point 2F returns in the direction of the point 2F. Similarly, as shown in FIG. 4(b), the light radiated from the focal point F is reflected by the unit reflecting surface 2 on the X-axis, and the principal ray of the reflected light becomes parallel to the Z-axis. On the other hand, the light from the point 2F is reflected and then converges on the point 2F on the Z-axis.

[0028] 〔Relationship between the Y-axis reflecting surface angle θ and the X-axis reflecting surface angle β of the unit reflecting surface and the position in the X-Y plane〕 From the above optical properties, as shown in FIGS. 4(a) and (b), the Y-axis reflecting surface angle θ of the unit reflecting surface 2 of the sheet 1 of the present invention is expressed by the formula θ = arctan(Y / 2f), where Y is the length in the Y-axis direction from the X-axis center O to the unit reflecting surface, and 2f is twice the focal length f. Similarly, the X-axis reflecting surface angle β of the unit reflecting surface 2 is expressed by the formula β = arctan(X / 2f), where X is the length in the X-axis direction from the X-axis center O to the unit reflecting surface 2, and 2f is twice the focal length f.

[0029] In FIG. 4, the subscript b represents the lower end in the vertical direction, m represents the center in the vertical direction, re represents the right end in the horizontal direction, and rc represents the center on the right side in the horizontal direction. In FIG. 4(a), the Y-axis center is made to coincide with the X-axis center O.

[0030] 〔Method for producing the unit reflecting surface〕 Here, a method for manufacturing the unit reflecting surface 2 will be described. The unit reflecting surface 2 is created using a mold 40 (a mold for manufacturing the present invention sheet 1. Refer to FIG. 3). As shown in FIG. 8 described later, after the unit reflecting surface 2 is formed on the back surface of the transmissive material of the present invention sheet 1 and the back surface is coated with a metal layer 7, the video light incident from the front side is reflected by the back surface and emitted to the front side. Therefore, the surface shape of the mold 40 corresponds to the female mold shape of the back surface of the present invention sheet 1.

[0031] [Method of manufacturing the mold] The surface shape of the mold 40 is formed by cutting with a tool bit 50 used as an ultra-precision cutting tool. As shown in FIGS. 3(a) and (b), the mold 40 has a female mold part 2K of the unit reflecting surface 2, a female mold part 3XK of the step 3X, and a female mold part 3YK of the step 3Y. The female mold part 2K of the unit reflecting surface 2 has a Y-axis reflecting surface angle θ equivalent to that of the unit reflecting surface 2 (when θn is not related to the position, it is described as θ). The Y-axis reflecting surface angle θ is 0° at Y = 0 which is the center in the Y-axis direction of the mold 40, and becomes a larger angle as it moves away from the center. Also, in the female mold parts 2K of all the unit reflecting surfaces 2 in the X-axis direction where the value of Y is the same, the Y-axis reflecting surface angle θ has the same value. In the present invention sheet 1, if the Y-axis reflecting surface angle θ of the unit reflecting surface 2 where Y is the minimum value is θb, then as shown in FIG. 3(a), the angle for forming the female mold part 2K of the unit reflecting surface 2 by cutting with the tool bit 50 is also θb. On the other hand, the angle of the tool bit 50 for forming the female mold part 3YK of the step 3Y which becomes a Y-axis unnecessary surface is 90° perpendicular to the Y-axis. When cutting while moving the tool bit 50 in the X-axis direction, since the movement of the tool bit 50 in the Y-axis direction is restricted, the Y-axis reflecting surface angle θb is kept constant. In FIG. 3(a), θb + 1 represents the Y-axis reflecting surface angle of the unit reflecting surface 2 where Y is the next larger value after the minimum value.

[0032] When forming the unit reflecting surface 2 in the X-axis direction within the region enclosed by the dashed circle 80 in Fig. 3(c), while moving the tool bit 50 in the X-axis direction in the order of to in Fig. 3(a), it is also moved in the Z-axis direction. By moving simultaneously in the Z-axis direction, it is possible to form the unit reflecting surface 2 with the X-axis reflecting surface angle βrc while keeping the Y-axis reflecting surface angle θb constant. Here, β in βrc represents the X-axis reflecting surface angle, and the subscript rc represents the center on the right side in the horizontal direction in Fig. 3(c).

[0033] Fig. 3(c) shows the shapes of the cross-sections in the X-axis direction and the Z-axis direction with respect to the Yn-axis in the direction of the Y-axis reflecting surface angle θ. Here, the "ridge (reference)" indicated by the two-dot chain line is the "ridge (reference)" in Fig. 3A to be described later, and it shows the position of the surface to be cut of the mold material before cutting. The "ridge (reference)" of this mold 40 corresponds to the "valley (reference)" (Fig. 1) of the present invention sheet 1 with the mold 40 as the female mold.

[0034] The Y-axis reflecting surface angle θ changes according to the value of Y, but the shapes of the cross-sections in the X-axis direction and the Z-axis direction with respect to the Yn-axis in the direction of the Y-axis reflecting surface angle θ are determined by the value of Z at the value of X regardless of Yn as shown in Fig. 3(c). Therefore, by simply adjusting the angle of the tool bit 50 forming the female mold part 2K of the unit reflecting surface 2 at the X-axis center O to θ, it becomes possible to form the female mold part 2K of the unit reflecting surface 2 in the X-axis direction. On the other hand, as shown in Fig. 3(a), when the Y-axis reflecting surface angle becomes θm, when the cutting surface of the tool bit 50 is adjusted to θm, the Y-axis unnecessary surface angle φ Y becomes 90° or less, and it becomes necessary to consider the adverse effect due to reflection on the Y-axis unnecessary surface. Here, the subscript m in θm represents the center in the vertical direction.

[0035] Also, Fig. 3A shows the array structure of the unit reflecting surface 2 when the positions of the ridges of the steps 3Y and 3X formed on the mold 40 are used as a reference and the X-axis reflecting surface angle β is set to three levels of small, medium, and large. In Fig. 3A, (a) is a schematic perspective view, (b) is a side view, and (c) is a top view. It can be seen that as β increases, the valley of the step 3X becomes deeper.

[0036] Figure 3B shows the cutting method of the mold for manufacturing the unit reflector array sheet with a flat unit reflector. In Figure 3B, Yb is the cutting area at the lower end in the Y-axis direction (the part where the value of Y is the smallest), and Yb+1 is the cutting area one level above Yb. Since the length of the cutting tool for cutting the unit reflector is longer than the length of the side of the unit reflector in the Y-axis direction, the part shown by the triangle in Figure 3B(a) adjacent to the boundary area with Yb+1 is also cut simultaneously when cutting Yb. However, since the part shown by this triangle is cut deeper in the Z-axis direction when cutting Yb+1 and does not remain, there is no problem that the shape after cutting deviates from the target. Since the inclination angle of the unit reflector from the X-axis, that is, the X-axis reflector angle β (Figure 3B(b)), is controlled by the depth in the Z-axis direction, the deeper the depth in the Z-axis direction as the value of X increases, and accordingly, the part of the triangle cut simultaneously adjacent to the boundary area also becomes larger.

[0037] Also, Figure 3C shows the case where, in Figure 3B, the unit reflector is changed from a plane to a curved surface. Also in this case, the part shown by the substantially triangular shape (a triangle with a curved hypotenuse) in Figure 3C(a) adjacent to the boundary area with Yb+1 is also cut simultaneously when cutting Yb. However, since the part of this substantially triangular shape is cut deeper in the Z-axis direction when cutting Yb+1 and does not remain, there is no problem that the shape after cutting deviates from the target.

[0038] As shown in Figure 3(c), the shape of the mold 40 is symmetric with respect to the Y-Z plane passing through the X-axis center O. Therefore, it is also possible to create the right half of the mold from the X-axis center O, and connect the secondary mold made from that mold to the original mold at the X-axis center O to create a mass-production mold. Further, the cutting direction in the X-axis direction may be from the end side to the X-axis center O instead of from the X-axis center O to the end side.

[0039] Also, by using the mold 40, the production of the sheet of the present invention can use not only the UV curing process but also processes such as hot pressing and casting molding (roll to roll) with high industrial productivity.

[0040] 〔Comparison between the sheet of the present invention and the linear Fresnel lens〕 [Comparison of Optical Characteristics] As described above, since the linear Fresnel lens 100 has a shape change in the vertical direction and no shape change in the horizontal direction (Fig. 10(a)), it is used for the purpose of collecting parallel light on a line parallel to the X-axis passing through the focal point F. Therefore, the reflected light of the light rays incident from the focal point F and the point 2F is reflected in front of the linear Fresnel lens 100 according to the law of reflection (Fig. 11(a)) and spreads in a direction away from the X-axis center O (Fig. 11(b)). Therefore, when the linear Fresnel lens 100 is used for the reflecting surface of the front type screen, the reflected light in the horizontal direction goes to the front outside of the reflecting surface 102 (Fig. 11(b)), so that the images on both ends of the front type screen become extremely dark images.

[0041] On the contrary, when the sheet 1 of the present invention is used, the reflected light in the X-axis direction is reflected back in the direction of the X-axis center O or Xo (Fig. 5(b)), so that the images on both ends of the front type screen do not become dark. Here, in Fig. 5, the subscript o of Y represents the center of the Y-axis, and b, m, and t (t is also the subscript of θ) represent the lower end, the center, and the upper end in the vertical direction of the reflecting surface of the front type screen, respectively. Also, the subscript o of X represents the X-axis center, and lc, le, rc, and re represent the left center, the left end, the right center, and the right end in the horizontal direction of the reflecting surface of the front type screen, respectively. Note that the plane mirror in Fig. 5(c) is shown for reference.

[0042] [Comparison of Mold Manufacturing Methods] Furthermore, for the mold manufacturing for the sheet of the present invention, if cutting is performed with a movement in which a linear bite movement in the X-axis direction is added with a bite push-in in the Z-axis direction, the bite does not move in both the Y-axis direction and the X-axis direction as in the mold manufacturing for the circular Fresnel lens. Therefore, in the mold manufacturing for the sheet of the present invention, a large circular cutting device is not required, and a mold can be manufactured with a cutting device having a one-dimensional cutting stage and a three-dimensional bite control function. Furthermore, since the mold can also be made into a roll (cylindrical mold), an increase in the size of the lens sheet, which was difficult with the circular Fresnel lens, and an improvement in the productivity of the manufacturing process can be achieved.

[0043] [Front - type Screen Comprising the Sheet of the Present Invention and Its Manufacturing Process] Next, with reference to FIG. 6 showing an example and FIG. 6A showing another example, the configuration of a front - type screen (hereinafter also referred to as "the screen of the present invention") comprising the sheet 1 of the present invention will be described together with the manufacturing method.

[0044] In the example of FIG. 6, a liquid UV resin material (which will become the uneven portion 1A of the sheet 1 of the present invention) is allowed to overflow in the mold 40 (FIG. 6(a)), and UV polymerization is carried out while being pressed with a flat transparent resin plate having a thickness of 100 - 200 μm (which will become the flat plate portion 1B of the sheet 1 of the present invention) (FIG. 6(b)). After the sheet 1 of the present invention thus obtained is die - cut, a metal layer 7 is disposed on the back side thereof, and a surface - shape diffusion film 9 is disposed on the front side via a substrate 5 (FIG. 6(c)). Note that the surface - shape diffusion film 9 is manufactured by UV polymerization using the substrate 5 as described later.

[0045] Also, in the example of FIG. 6A, a liquid UV resin material (which will become the uneven portion 1A of the sheet 1 of the present invention) is allowed to overflow in the mold 40 (FIG. 6A(a)), and UV polymerization is carried out while being pressed with a substrate 5 with a surface - shape diffusion film 9 (FIG. 6A(b)). In this example, since the uneven portion 1A of the sheet 1 of the present invention is in close contact with the substrate 5 and the distance between the surface - shape diffusion layer and the reflecting surface is shortened, deterioration of the image resolution can be suppressed to a low level. After the sheet 1 of the present invention thus obtained is die - cut, a metal layer 7 is disposed on the back side thereof (FIG. 6A(c)).

[0046] [Metal Layer] In order to make the back surface, which is the side having the step of the sheet 1 of the present invention, the reflecting surface, the screen of the present invention is provided with a metal layer 7 (FIG. 6(c)) on the back surface. The metal layer 7 can be formed by performing metal vapor deposition or aluminum coating with a high reflectivity (reflectivity of 55% or more) using the unit reflecting surface 2 and the X - axis and Y - axis unnecessary surfaces as a base. Note that the thickness (dimension in the Z - axis direction) of the metal layer 7 is 1 μm or less in the case of vapor deposition, but is preferably 20 - 100 μm in the case of aluminum coating. If the thickness of the metal layer 7 in aluminum coating is less than 20 μm, peeling may occur, and if it exceeds 100 μm, the coated surface may become uneven.

[0047] [Surface Shape Diffusion Film] The surface of the screen of the present invention preferably causes diffusion (diffusion of incident light) on the surface in order to eliminate reflection, hot spots, and hot bars. As a method of causing diffusion on the surface, it is preferable to include a processing step of providing a surface shape diffusion film 9 (Fig. 6(c)) on the front surface of the sheet 1 of the present invention. Examples of the surface shape diffusion film 9 include the "anisotropic diffusion layer depending on surface shape" disclosed in Patent Document 1. This is a diffusion layer having the characteristic that the diffusion angle of light is different in two orthogonal directions. The material of this diffusion layer is an ultraviolet curable resin such as urethane acrylate or epoxy acrylate, or other ionizing radiation curable resins such as electron beam curable resins, and has flexibility. On the front side of this diffusion layer, a large number of irregularly long ridges extending substantially in one direction are arranged side by side at irregular intervals in a direction (C direction) orthogonal to the extending direction (L direction). According to such a surface shape, the diffusion angle when diffusing in the C direction is larger than the diffusion angle when diffusing in the L direction. From the viewpoint of the resolution of the image, the layer thickness of this diffusion layer is preferably as thin as possible.

[0048] [More Detailed Manufacturing Process of the Screen of the Present Invention] Next, a more detailed manufacturing process of the screen of the present invention will be described with reference to Fig. 7, which is a cross-sectional view in the horizontal direction. In this more detailed manufacturing process, in addition to the sheet 1 of the present invention, the metal layer 7, the surface shape diffusion film 9, and the substrate 5 (Fig. 7(c)), a protective layer 8 and a magnet sheet 11 (Fig. 7(e)) are used as suitable auxiliary members that contribute to preventing deformation or deterioration of semi-finished products or products, or facilitating installation. These auxiliary members become constituent members of the product.

[0049] First, a surface shape diffusion film 9 is formed on the front surface of the substrate 5 (Fig. 7(a)). As a forming method, for example, an ultraviolet curable resin is charged into a mold (not shown) that is a female mold of the shaped surface of the surface shape diffusion film 9, pressed from above to a predetermined thickness on the front surface of the substrate 5, irradiated with ultraviolet rays to be cured, and then demolded.

[0050] Next, the inventive sheet 1 is formed on the back surface of the substrate 5 (Fig. 7(b)). As a forming method, for example, an ultraviolet-curable resin is allowed to overflow into a mold 40 (Fig. 6A(a)), pressed from above to a predetermined thickness on the back surface of the substrate 5, irradiated with ultraviolet rays to cure, and then demolded.

[0051] Next, a metal layer 7 is formed on the back surface of the inventive sheet 1 (unit reflecting surface 2 and steps 3X, 3Y) (Fig. 7(c), where the step 3Y is not shown). As a forming method, on the back surface of the inventive sheet 1, for example, a metal such as aluminum, silver, nickel, etc. is vapor-deposited, sputtered, or a metal foil is transferred, or a method of coating thin pieces of aluminum so that these surfaces are parallel is exemplified.

[0052] Next, a protective layer 8 is formed on the back surface of the metal layer 7 (Fig. 7(d)). As a forming method, for example, a method of applying and curing a material obtained by mixing resins such as urethane-based resins, epoxy-based resins, and acrylic-based resins as a base material and adding a light absorber and various additives to the back surface of the metal layer is exemplified. Examples of the light absorber include dark-colored paints such as black, dark-colored dyes and pigments such as black, or beads containing these. The various additives are materials that protect the metal layer 7 from deterioration such as oxidation. Note that the protective layer 8 may be formed using a thermosetting resin or an ultraviolet-curable resin containing the light absorber and the various additives, or may be formed with a dark-colored paint or the like.

[0053] In the final step, a magnet sheet 11 (or a holding plate not shown) is bonded to the back surface of the protective layer 8 with an adhesive (Fig. 7(e)).

[0054] By the above manufacturing method, the inventive screen can be finished into a thin sheet shape with a thickness of about 1 mm, and it is also possible to form a magnet sheet on the back surface.

[0055] [First Embodiment of the Inventive Screen] Next, a first embodiment in which the image light from the position of the focal point F is reflected by the reflecting surface in the screen of the present invention will be described. An example of the first embodiment is shown in FIG. 8. The screen 60 of the present invention in FIG. 8 is the same as that in FIG. 7(e) (in FIG. 8, illustration of the substrate 5, the protective layer 8, and the magnet sheet 11 (see FIG. 7(e)) is omitted). In this example, a light projection unit (not shown) of the video projection apparatus 20 is placed at the position of the focal point F of the reflecting surface (the metal layer 7 on the back side) of the sheet 1 of the present invention, and the principal ray of the image light reflected by the reflecting surface is directed in the normal direction of the screen surface. Here, the screen surface refers to the front surface of the sheet 1 of the present invention (the same applies hereinafter).

[0056] In the screen 60 of the present invention, a surface shape diffusion film 9 with a large diffusion angle may be required on the screen surface in order to widen the horizontal viewing area. For example, in the case of a 100-inch 16:9 screen, the diffusion angle must be ±15° or more in the vertical direction and ±35° or more in the horizontal direction. Note that "diffusion of ±15° or more" means that the diffusion half-value width with the normal direction of the screen surface being 0° is ±15° (the same applies when 15° is another angle value). A screen with only diffusion without using a Fresnel lens requires a large diffusion of ±80° or more in order to make the ratio of the brightness between the center part and both end sides in the horizontal direction of the screen within the allowable range of 1 / 10 or more, and as a result, the horizontal viewing area is also widened. However, as the diffusion increases, the brightness of the screen decreases. Therefore, the screen of the present invention has a small variation in screen brightness and is a high-brightness screen, and the demand is considered to increase in the future. Furthermore, as described above, the screen of the present invention is in a thin sheet shape with a thickness of about 1 mm and can be made into a magnet sheet on the back surface, so it can be rolled up and transported, or directly attached and installed on the flat surface of a steel wall or rack. Therefore, it is also excellent in portability and installability.

[0057] [Second Embodiment of the Screen 5 of the Present Invention] Next, a second embodiment in which a spatial imaging iris surface is formed in the screen 60 of the present invention will be described.

[0058] An example of the second embodiment is shown in FIG. 9. In FIG. 9, the illustration of the surface shape diffusion film 9 (see FIG. 8) is omitted. In the second embodiment, the image light from a position approximately at a distance a from the screen surface of the screen 60 of the present invention is reflected by a reflecting surface (the metal layer on the back side of the sheet 1 of the present invention) to form a spatial imaging iris surface 30 at a position approximately at a distance b. Here, a and b satisfy the relational expression of (1 / a) + (1 / b) = 1 / f, where f is the focal length of the reflecting surface, and "approximately a" and "approximately b" mean that a and b satisfying the above relational expression have an allowable range within ±10% respectively. Note that at the position approximately at the distance a, the aperture 24A (FIG. 9(c)) of the projection optical system 24 of the image projection device 20 is placed.

[0059] The optical method such as the second embodiment is called a spatial imaging iris surface method. In the spatial imaging iris surface method, an observer placing their eyes within the spatial imaging iris surface 30 can observe a projected image with uniform brightness on the screen 60 of the present invention.

[0060] [The image display system of the present invention] Finally, the image display system of the present invention will be described. As shown in FIGS. 8 and 9, the image display system of the present invention includes the screen 60 of the present invention and an image projection device 20 that projects image light onto the reflecting surface (the metal layer on the back side of the sheet 1 of the present invention). As shown in FIG. 9(c) as an example, the image projection device 20 sequentially passes the light source light from the three-primary-color light source 21 composed of LED chips through a diffusion film laminate 22 as a homogenizer, relay lenses 20a, 20b, and a digital micromirror device 23. Subsequently, it is configured to be sequentially reflected by a concave mirror 25 and a convex mirror 26 through a projection optical system 24 composed of a plurality of lenses and sent to the screen 60 of the present invention. The light that does not go towards the screen is blocked by a light shield 27.

[0061] [Usefulness of the image display system of the present invention] Here, a supplementary explanation will be given regarding the usefulness of the video display system of the present invention. Generally, in order to apply a video display system using a front type screen to a large display, it is necessary to increase the size of the screen. However, if the size of a conventional front type screen is simply increased, although the horizontal viewing area remains wide, the brightness of the image decreases. Therefore, for example, there is a problem that high-brightness and high-contrast video light cannot be delivered to multiple side-by-side attendees even in a bright room at school. On the other hand, by using the screen of the present invention, the video display system of the present invention can equalize the brightness at the center and both ends in the horizontal direction of the screen as described above. In addition, by using the surface shape diffusion film, a wide horizontal viewing angle can be realized. Regarding portability, as described above, the screen of the present invention can be rolled up for transportation by being thinned and having a magnet sheet on the back surface, and it is easy to improve portability. Although conventional paper or cloth screens can also be rolled up for transportation, compared with these, the screen of the present invention has good contrast and significantly excellent image quality, so it is useful.

Explanation of Signs

[0062] 1 Unit reflecting surface array sheet (sheet of the present invention) 1A Concave and convex portion of the sheet of the present invention 1B Flat plate portion of the sheet of the present invention 2 Unit reflecting surface 2K Female die portion of the mold of unit reflecting surface 2 3X Step in the horizontal (X-axis) direction 3XK Female die portion of the mold of step 3X 3Y Step in the vertical (Y-axis) direction 3YK Female die portion of the mold of step 3Y 5 Substrate 6 Holding plate 7 Metal layer 8 Protective layer 9 Surface shape diffusion film 11 Magnet sheet 20 Video projection device 20a, 20b Relay lens 21 Three-primary color light source 22 Diffusion film laminate 23 Digital mirror device 24 Projection optical system 24A aperture 25 concave mirror 26 convex mirror 27 light shield 30 spatial imaging iris surface 40 mold (for manufacturing the sheet of the present invention) 50 diamond bit (bit) 60 screen of the present invention 100 linear Fresnel lens 102 reflecting surface (reflecting surface of the linear Fresnel lens) 102K female mold part of the mold of the reflecting surface 102 103 Y-axis unnecessary surface (Y-axis unnecessary surface of the linear Fresnel lens) 103K female mold part of the mold of the Y-axis unnecessary surface 103 104 minute reflecting surface 400 mold (for manufacturing the linear Fresnel lens)

Claims

1. A unit reflecting surface array sheet for a front type screen in which a plurality of unit reflecting surfaces are arranged in the vertical and horizontal directions, wherein one side of the unit reflecting surface is 250 μm or less, having a focal point F at a focal distance f from the center O in the horizontal direction in a direction orthogonal to both the vertical and horizontal directions, wherein the inclination angle θ of the unit reflecting surface from the vertical direction, when the length in the vertical direction from the center O to the unit reflecting surface is Y, is θ = arctan(Y / 2f), wherein the inclination angle β of the unit reflecting surface from the horizontal direction, when the length in the horizontal direction from the center O to the unit reflecting surface is X, is β = arctan(X / 2f), A unit reflecting surface array sheet for a front type screen, characterized in that the principal ray of light starting from the focal point F and reflected by the unit reflecting surface is parallel to the direction orthogonal to both the vertical and horizontal directions.

2. A front type screen having the unit reflecting surface array sheet according to Claim 1, characterized in that a metal layer is provided on the back surface of the unit reflecting surface array sheet.

3. The front type screen according to Claim 2, characterized in that a surface shape diffusion film is provided on the front surface of the unit reflecting surface array sheet.

4. The front type screen according to Claim 2 or 3, characterized in that image light from the position of the focal point F is reflected by the reflecting surface.

5. Image light from a position approximately at a distance a from the screen surface of the front type screen is reflected by the reflecting surface to create a spatial imaging iris surface at a position approximately at a distance b from the screen surface, satisfying the relationship (1 / a) + (1 / b) = 1 / f. The front type screen according to Claim 2 or 3.

6. An image display system comprising the front type screen according to Claim 4 and an image projection device for projecting image light onto the reflecting surface.

7. An image display system comprising the front type screen according to Claim 5 and an image projection device for projecting image light onto the reflecting surface.

Images