JP7521364B2 - Video display device - Google Patents

Description

The present invention relates to a reflective screen and an image display device equipped with the same.

Conventionally, in image display devices equipped with a reflective screen and an image projection device, the use of short-focus projectors (image projection devices) that project image light onto the reflective screen from a close distance at a relatively large projection angle to achieve a large-screen display has become widespread, and various corresponding reflective screens have been developed.
A short-focus projector projects image light onto a reflective screen at a larger angle of incidence than conventional image sources, thereby making it possible to shorten the distance in the depth direction between the projector and the reflective screen, thereby contributing to space-saving image display devices that use reflective screens.

In order to display the image light projected by such a short focal projector well, various reflective screens have been developed in which a reflective layer is formed on the surface of a lens layer having a Fresnel lens shape (see, for example, Patent Documents 1 and 2).

Patent No. 3655972 JP 2008-76522 A

2. Description of the Related Art Among conventional reflective screens, there is known one that is provided with a diffusion layer that contains a diffusion material dispersed therein in order to ensure a viewing angle.
However, such reflective screens have a diffusion layer that increases the thickness of the screen itself, or the thickness of the diffusion layer must be increased in order to obtain sufficient diffusion performance, which may result in insufficient flexibility for the screen to be rolled up and stored when not in use.

Reflective screens are also known which diffuse the image light and ensure a wide viewing angle by providing a layer coated with particles (filler) on the surface closest to the image source (viewer side) or by providing a finely uneven shape on the surface closest to the image source.
However, in such a reflective screen, if the roughness (mattness) of the surface closest to the image source is increased in order to increase the viewing angle of the image, the front luminance of the image decreases, and if the roughness is reduced in order to improve the front luminance, a sufficient viewing angle cannot be obtained. Therefore, for example, in the reflective screen shown in Patent Document 1, a lenticular lens shape is provided on the surface closest to the image source, and a matt shape is given to the surface, thereby controlling the viewing angle and gain.

In recent years, projectors using a laser light source as the light source are becoming more common among the single focus projectors described above. Projectors using a laser light source have high luminance and can display bright and clear images. On the other hand, when using a projector using a laser light source, for example, a problem occurs in that bright lines are observed and the quality of the image is reduced on a screen having a lenticular lens shape with a matte shape given to the surface on the image source side as in Patent Document 1.
The above-mentioned Patent Documents 1 and 2 do not disclose any measures for obtaining a good viewing angle and front luminance, and suppressing bright lines and the like in response to an image source using a laser light source.

The objective of the present invention is to provide a reflective screen that provides a good viewing angle and front brightness, and that suppresses bright lines and other defects caused by image light from an image source that uses a laser light source, and an image display device that includes the same.

The present invention solves the above problems by the following solving means. Note that, for ease of understanding, the following description will be given with reference numerals corresponding to the embodiments of the present invention, but the present invention is not limited thereto.
The first invention is a reflective screen which reflects image light (L) projected from an image source (LS) to display it in an observable manner, the reflective screen (10) comprising: a lens layer (13) having a Fresnel lens shape on the rear side thereof, the lens layer (13) having a lens surface (132) and a non-lens surface (133) and having unit lenses (131) which are convex on the rear side, an optical shape on the rear side of the reflective screen, the optical shape on the rear side of the reflective screen being an array of unit optical shapes (111), a surface layer (11) which is provided closest to the image source, has an optical shape on the surface on the image source side of the reflective screen, the surface on the image source side being a rough surface, and the transmission haze value of the surface layer is 91% or more and 94% or less.
The second invention is a reflective screen (10) characterized in that, in the reflective screen of the first invention, the unit optical shapes (111) are convex toward the image source side, are formed in a strip shape extending in the vertical direction of the screen of the reflective screen, and are arranged in the horizontal direction of the screen.
The third invention is a reflective screen (10) characterized in that, in the reflective screen of the second invention, the surface layer (11) has an optical shape formed on the surface facing the image source in the form of a lenticular lens shape in which unit surface lenses (111), which are unit optical shapes, are arranged, and the unit surface lenses are arranged in the left-right direction of the screen with the top-to-bottom direction of the screen as the ridge direction when the reflective screen is in use.
A fourth invention is a reflective screen (10) characterized in that, in the reflective screen of the first invention, the Fresnel lens shape is a circular Fresnel lens shape, and its optical center (C) is located outside the display area of the reflective screen.
The fifth invention is a reflective screen (10) characterized in that, in the reflective screen of the first invention, a colored layer (17) colored to a predetermined concentration is provided between the surface layer (11) and the lens layer (13).
The sixth invention is a reflective screen (10) characterized in that, in the reflective screen of the fifth invention, a transparent resin layer (12) having optical transparency is provided on the back side of the surface layer (11), and the colored layer (17) is provided between the transparent resin layer and the lens layer.
The seventh invention is a reflective screen (10) characterized in that, in the reflective screen of the fifth invention, a transparent resin layer (12) having optical transparency is provided on the image source side of the lens layer (13), and the colored layer (17) is provided between the surface layer and the transparent resin layer.
The eighth invention is a reflective screen (10) characterized in that, in the reflective screen of the fifth invention, a first transparent resin layer (12) having optical transparency is provided on the back side of the surface layer (11), a second transparent resin layer (18) having optical transparency is provided on the image source side of the lens layer, and the colored layer (17) is provided between the first transparent resin layer and the second transparent resin layer.
A ninth aspect of the present invention is an image display device (1) comprising the reflective screen (10) of the first aspect of the present invention, and an image source (LS) that projects image light onto the reflective screen.
A tenth aspect of the present invention is an image display device (1) according to the ninth aspect of the present invention, characterized in that the image source (LS) uses a laser light source.

The present invention provides a reflective screen that provides a good viewing angle and front brightness, and suppresses bright lines and other defects caused by image light from an image source using a laser light source, and an image display device equipped with the same.

1 is a diagram showing an image display device 1 according to an embodiment. 1 is a diagram showing a layer structure of a screen 10 according to an embodiment. FIG. 2 is a diagram illustrating a surface layer 11 according to the embodiment. 11A to 11C are diagrams illustrating other embodiments of the surface layer 11. 3A and 3B are diagrams illustrating a lens layer 13 according to the embodiment. 2 is a diagram showing how image light and external light incident on a screen 10 according to an embodiment travel. FIG. 10A to 10C are diagrams illustrating a layer structure in another embodiment of the screen 10.

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

In this specification, the terms plate, sheet, etc. are used, and in general usage, they are used in the order of thickness, plate, sheet, and film, and this specification follows that order. However, since such distinction in usage has no technical meaning, these terms can be used interchangeably as appropriate.
In this specification, the screen surface refers to a surface that is in the planar direction of the screen when viewed as a whole, and is parallel to the image plane (display surface) of the screen.

(Embodiment)

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

To facilitate understanding, an XYZ Cartesian coordinate system is set up and shown as appropriate in each of the following figures, including FIG. 1. In this coordinate system, the left-right direction of the screen of the screen 10 is the X direction, the up-down direction of the screen is the Y direction, and the thickness direction of the screen 10 is the Z direction. The screen of the screen 10 is parallel to the XY plane, and the thickness direction of the screen 10 (Z direction) is perpendicular to the screen of the screen 10.

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

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

The screen 10 is a reflective screen that reflects image light L projected by an image source LS toward an observer O to display an image.
The screen 10 has a display area (image area) that is generally rectangular in shape when viewed from the observer O side and whose longer side extends in the left-right direction (X direction) of the screen.
The screen 10 has a large screen size of about 60 to 100 inches diagonally, and the aspect ratio of the screen is 16:9. However, the screen size is not limited to this, and may be, for example, about 40 inches or less, and the size and shape can be appropriately selected depending on the purpose of use, the environment in which it is used, etc.

The screen 10 has flexibility that allows it to be rolled up, and when not in use, it can be rolled up and stored in a predetermined box (not shown) or the like. When in use, the screen 10 may be in a form in which at least two opposing sides are supported by a support member (not shown) or the like, thereby maintaining its flatness.
The total thickness of the screen 10 is preferably 70 μm or more and 700 μm or less, and more preferably 100 μm or more and 700 μm or less. If the total thickness of the screen 10 is smaller than this range, it may not be possible to obtain the desired optical performance. If the total thickness of the screen 10 is larger than this range, the flexibility may decrease, making it difficult to wind up the screen 10, or the screen 10 may be damaged or the like when wound up.

Fig. 2 is a diagram showing the layer structure of the screen 10 of this embodiment. Fig. 2 shows an enlarged portion of a cross section that passes through point A (see Figs. 1(a) and (b)) which is the screen center (geometric center of the screen) of the screen 10, is parallel to the up-down direction of the screen (Y direction), and is perpendicular to the screen surface (parallel to the Z direction).
As shown in FIG. 2, the screen 10 includes, in order from the image source side (+Z side), a surface layer 11, a transparent resin layer 12, a lens layer 13, a reflective layer 14, and a rear surface protective layer 15, which are laminated together.

Fig. 3 is a diagram illustrating the surface layer 11 of this embodiment. Fig. 3 shows an enlarged view of a portion of a cross section of the surface layer 11 in a cross section parallel to the left-right direction (X direction) and thickness direction (Z direction) of the screen 10.
The surface layer 11 is a layer provided closest to the image source (+Z side) in the thickness direction of the screen 10, and has optical transparency. The surface layer 11 of this embodiment has unit surface lenses 111 arranged on its image source side surface, which are convex toward the image source side, and has a lenticular lens shape as an optical shape.

The unit surface lenses 111 are each a part of a cylinder, with the ridgeline direction (longitudinal direction) being the vertical direction of the screen (Y direction), and are arranged in the horizontal direction of the screen (X direction). The cross-sectional shape of the unit surface lenses 111 shown in Fig. 3 is a part of a circle. The shape of the unit surface lenses 111 is not limited to the above, and may be, for example, a part of an elliptical cylinder, or a cylindrical lens shape made up of multiple curved surfaces.
By providing a surface layer 11 on which such unit surface lenses 111 are formed, the image light L is diffused in the left-right direction of the screen by the unit surface lenses 111, and the screen 10 can ensure a sufficient viewing angle in the left-right direction of the screen (X direction).

It is preferable that the arrangement pitch P1 of the unit surface lenses 111 is within the range of 30 to 120 μm, and that the height h1 of the unit surface lenses 111 (the dimension from the apex of the unit surface lenses 111 in the thickness direction of the screen to the point which is the bottom between the unit surface lenses 111) is within the range of 10 to 25 μm, from the viewpoint of diffusing the image light in the left-right direction of the screen and ensuring a sufficient viewing angle in the left-right direction of the screen.
Since the surface layer 11 includes the unit surface lenses 111 as described above, the thickness of the surface layer 11 is formed to be 15 to 35 μm.

In addition, the unit surface lens 111 of this embodiment has a rough surface (matte surface) with fine irregularities on its image source side (+Z side). By roughening the image source side surface of the surface layer 11, it is possible to obtain effects such as suppressing reflections of external light such as illumination light and sunlight and the resulting decrease in image contrast, and expanding the viewing angle in the vertical direction of the screen (Y direction). Note that the diffusion effect of the rough surface is smaller than the diffusion effect of the lens shape of the unit surface lens 111, but even if the viewing angle is smaller in the vertical direction of the screen compared to the horizontal direction of the screen, it is not a problem and a sufficient viewing angle can be secured. In addition, the diffusion effect of the rough surface does not diffuse the image light too much, so it is possible to suppress a decrease in the front luminance of the image.

Furthermore, by roughening the image source side surface of the surface layer 11, it is possible to obtain the effect of eliminating bright lines due to a portion of the image light. If the surface of the unit surface lens 111 were a smooth surface without fine unevenness as described above, a portion of the image light projected from the image source LS would be condensed by the lens shape of the unit surface lens 111, and a bright line would be generated along the longitudinal direction (Y direction) at a position corresponding to the apex of the unit surface lens 111 and would be visually recognized by the observer O, resulting in a deterioration in image quality.
However, by roughening the image source side surface of surface layer 11 (the surface of unit surface lens 111) as described above, the image light that causes the above-mentioned bright lines is diffused, thereby suppressing the bright lines.

From the viewpoint of suppressing the above-mentioned bright lines, the surface layer 11 preferably has a transmission haze value (proportion of diffuse transmittance in total light transmittance) of 91% or more and 94% or less for the surface layer 11 alone. This transmission haze value is the transmission haze value for the surface layer 11 alone, and can be measured by a haze meter (NDH7000SP manufactured by Nippon Denshoku Industries Co., Ltd.).
If the transmission haze value of the surface layer 11 is less than 91%, the effect of suppressing the bright lines as described above cannot be sufficiently obtained. On the other hand, if the transmission haze value of the surface layer 11 is greater than 94%, the effect of suppressing the bright lines can be obtained, but the image light for displaying the image may be diffused too much, resulting in a decrease in the front brightness. Therefore, the transmission haze value of the surface layer 11 is preferably within the above range.

The surface layer 11 of this embodiment is formed using an ultraviolet curing resin such as urethane acrylate, epoxy acrylate, etc. Note that the material for forming the surface layer 11 is not limited to this, and an ionizing radiation curing resin such as an electron beam curing resin or a thermoplastic resin may be used.
In addition, the surface layer 11 of this embodiment may be formed by molding a lenticular lens shape on one surface (the surface on the +Z side) of the transparent resin layer 12 by an ultraviolet molding method or the like, and then blasting the surface of the lenticular lens shape. Alternatively, without being limited to this, the surface layer 11 may be formed on one surface (the surface on the +Z side) of the transparent resin layer 12 by an ultraviolet molding method or the like using a molding die that has been subjected to blasting to impart the lenticular lens shape.
The method for forming the surface layer 11 may be appropriately selected depending on the resin material to be used, etc.

The surface layer 11 is not limited to the above example, and may have other lens shapes.
Fig. 4 is a diagram for explaining another embodiment of the surface layer 11. Fig. 4 shows an enlarged view of a part of a cross section parallel to the XZ plane of the surface layer 11, similar to Fig. 3 .
4, the surface layer 11 may have an optical shape in which unit prisms 112 that are convex toward the image source side are arranged on the image source side. The unit prisms 112 are arranged in the left-right direction of the screen (X direction) with their ridge lines oriented in the vertical direction of the screen (Y direction).

In this case, it is preferable that the arrangement pitch P3 of the unit prisms 112 is 30 μm or more and 120 μm or less, and the apex angle γ is 120° or more and 160° or less. The apex of the unit prism 112 may be curved so as to be convex toward the image source side.
Moreover, in the surface layer 11 having such unit prisms 112, from the viewpoint of suppressing the above-mentioned bright lines, the transmission haze value of the surface layer 11 is preferably 91% or more and 94% or less.
Even if the optical shape of the surface layer 11 on the image source side has a prism shape in which unit prisms 112 are arranged as described above, a sufficient viewing angle in the left-right direction of the screen can be secured, a preferable front brightness can be obtained, and bright lines caused by an image source using a laser light source can be suppressed.

2, the transparent resin layer 12 is located on the back side (−Z side) of the surface layer 11. The transparent resin layer 12 in this embodiment is a layer that serves as a substrate (base) for forming the surface layer 11.
The transparent resin layer 12 is formed, for example, from a polyester resin such as PET (polyethylene terephthalate) having high light transmittance, an acrylic resin, a styrene resin, an acrylic-styrene resin, a PC (polycarbonate) resin, an alicyclic polyolefin resin, a TAC (triacetyl cellulose) resin, or the like.

The transparent resin layer 12 has a thickness of 50 to 250 μm, which provides sufficient flexibility to allow the screen 10 to be rolled up, and is suitable as a base material for the surface layer 11 .
In this embodiment, the transparent resin layer 12 is made of polyethylene terephthalate and has a thickness of 188 μm.

Fig. 5 is a diagram for explaining the lens layer 13 of the embodiment. Fig. 5(a) shows the lens layer 13 alone as observed from the front direction on the rear side (-Z side). Fig. 5(b) shows a further enlarged view of a portion of the cross section of the screen 10 shown in Fig. 2, and for ease of understanding, only the lens layer 13, the reflective layer 14, and the rear surface protective layer 15 are shown.
The lens layer 13 is a light-transmitting layer provided on the rear side (-Z side) of the transparent resin layer 12, and as shown in FIG. 5( a), the rear side surface has a circular Fresnel lens shape in which unit lenses 131 are arranged on concentric circles.

This circular Fresnel lens shape has a so-called offset structure in which point C, which is its optical center (Fresnel center), is outside the screen (display area) of the screen 10 when the screen 10 is in use and is located below (on the -Y side) of the screen 10. Therefore, as shown in FIG. 5(a), when the lens layer 13 is viewed from the front direction of the back side (-Z side), it is observed that unit lenses 131 each having a partial shape of a perfect circle (arc-shaped) are arranged.

As shown in Figures 2 and 5 (b), the unit lenses 131 are parallel to the direction perpendicular to the screen surface (Z direction), and the cross-sectional shape in a cross section parallel to the arrangement direction of the unit lenses 131 is a triangular shape that is convex toward the back side (-Z side).
5B, each unit lens 131 has a lens surface 132 and a non-lens surface 133 that faces the lens surface 132 with a vertex t3 in between. When the screen 10 is in use, the lens surface 132 of each unit lens 131 is located vertically above (on the +Y side of) the non-lens surface 133 with the vertex t3 in between.

5B, in unit lens 131, the angle that lens surface 132 makes with a plane parallel to the screen surface is α, and the angle that non-lens surface 133 makes with a plane parallel to the screen surface is β. This angle β is larger than angle α (β>α).
The arrangement pitch of the unit lenses 131 is P2, and the lens height of the unit lenses 131 (the dimension from the vertex t3 in the thickness direction of the screen to the point t4 which is the bottom between adjacent unit lenses 131) is h2.

2 and other figures show the arrangement pitch P2 and angles α and β of the unit lenses 131 as being constant in the arrangement direction of the unit lenses 131. However, in reality, the arrangement pitch P2 of the unit lenses 131 of this embodiment is constant, but the angle α gradually increases as the unit lenses 131 move away from point C, which is the Fresnel center, in the arrangement direction of the unit lenses 131.
In this embodiment, the unit lenses 131 have an arrangement pitch P2 = 100 μm, an angle α of approximately 4° at the bottom center of the screen 10 in the left-right direction, an angle α of approximately 20° at the top center of the screen in the left-right direction, and an angle β of 90°.

However, the screen 10 is not limited to this, and may have a configuration in which the arrangement pitch P2 gradually changes along the arrangement direction of the unit lenses 131.
In addition, the arrangement pitch P2 and angles α, β, etc. can be changed appropriately depending on the size of the pixels of the image source LS that projects the image light L, the projection angle of the image source LS (the angle of incidence of the image light L on the screen surface of the screen 10), the screen size of the screen 10, the refractive index of each layer, etc.

The lens layer 13 is formed of an ultraviolet-curable resin such as urethane acrylate, epoxy acrylate, etc. The lens layer 13 may be formed of other ionizing radiation-curable resins such as an electron beam-curable resin.
The lens layer 13 can be formed, for example, by ultraviolet ray molding on one surface (the surface on the −Z side) of the transparent resin layer 12. The method for forming the lens layer 13 may be appropriately selected depending on the resin or the like that is the material of the lens layer 13, and is not limited thereto.

The reflective layer 14 is a layer that has the function of reflecting incident light. The reflective layer 14 is formed on at least a part of the lens surface 132. As shown in Fig. 2 and Fig. 5(b), the reflective layer 14 of this embodiment is formed on the lens surface 132 but is not formed on the non-lens surface 133.
The reflective layer 14 is made of a metal having high light reflectivity, such as aluminum, silver, or nickel, and has a thickness of about 800 Å.
The reflective layer 14 in this embodiment is formed by vapor deposition of aluminum.

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

The rear surface protective layer 15 is provided on the rear surface side (−Z side) of the lens layer 13 and the reflective layer 14 to protect the reflective layer 14 and also protect the rear surface side (rear surface side) of the screen 10 .
2 and 5(b), the rear surface protective layer 15 of the present embodiment fills in the irregularities caused by the unit lenses 131 to flatten the rear surface side of the screen 10. The rear surface protective layer 15 covers the reflective layer 14 and the non-lens surface 133, and the non-lens surface 133 is in contact with the rear surface protective layer 15.
In addition, it is preferable that the back surface protective layer 15 has a light absorbing effect, from the viewpoint of absorbing unnecessary external light such as sunlight and illumination light that enters the screen 10 from the back side (-Z side) and improving the contrast of the image.

The back surface protective layer 15 of this embodiment has a light absorbing effect, and is formed by applying and curing a resin containing a dark-colored paint such as black, a dark-colored pigment or dye such as black, and a light absorbing material such as beads having a light absorbing effect to the back surface side (circular Fresnel lens shape side) of the lens layer 13 having the reflective layer 14 formed on the lens surface 132. As such a resin, a thermosetting resin such as an epoxy resin or a urethane resin, a thermoplastic resin such as an acrylic resin, an ultraviolet-curable resin such as a urethane acrylate or an epoxy acrylate, or the like is preferable.
The refractive index of this back surface protective layer 15, that is, the refractive index of the resin containing the above-mentioned light absorbing material, is preferably equal to or higher than the refractive index of the lens layer 13, from the viewpoint of efficiently absorbing unnecessary external light such as sunlight.
From the viewpoint of protecting the reflective layer 14 and the lens layer 13, the rear surface protective layer 15 may have an ultraviolet absorbing function, a hard coat function, or the like.

Fig. 6 is a diagram showing how image light and external light enter the screen 10 of the embodiment and travel. The cross section of the screen 10 shown in Fig. 6 is similar to the cross section of the screen 10 shown in Fig. 2 described above. In Fig. 6, for ease of understanding, the refractive indices of the surface layer 11, the transparent resin layer 12, the lens layer 13, and the rear surface protective layer 15 are shown as being equal to each other.
As shown in FIG. 6, image light L 1 projected from an image source LS enters the screen 10 from below, enters the surface layer 11 , passes through the screen 10 , and enters the unit lenses 131 of the lens layer 13 .
Next, the image light L1 is incident on the lens surface 132 and reflected by the reflective layer 14 , travels toward the image source side (+Z side), and is incident on the unit surface lens 111 of the surface layer 11 .

The image light L1 is diffused in the left-right direction (X direction) of the screen by the lens shape of the unit surface lens 111 before being emitted, so that a sufficient viewing angle in the left-right direction of the screen can be ensured. Furthermore, the image light L1 is diffused by the fine uneven shape of the surface of the unit surface lens 111, so that a viewing angle in the up-down direction (Y direction) of the screen can also be ensured, and bright lines caused by the laser light source of the image source LS can be suppressed. The diffusing effect of the fine uneven shape of the surface of the unit surface lens 111 is smaller than the diffusing effect of the lens shape of the unit surface lens 111, so that the viewing angle in the up-down direction of the screen is not unnecessarily widened, and the front luminance of the image is not reduced.
As described above, the image light L1 is efficiently reflected and diffused before reaching the observer O, so that the screen 10 has a sufficient viewing angle and front brightness and can display good images. Furthermore, even if the image source LS uses a laser light source, good images with suppressed bright lines can be displayed.

In addition, since the image light L1 is projected from below the screen 10 and the angle β (see FIG. 5(b)) is greater than the angle of incidence of the image light L1 at each point in the vertical direction (Y direction) of the screen 10, the image light L1 does not directly enter the non-lens surface 133 and the non-lens surface 133 does not affect the reflection of the image light L1.

On the other hand, unnecessary external light G1, G2 such as sunlight and illumination light that enters the screen 10 from the image source side (+Z side) mainly enters from above the screen 10, passes through the surface layer 11, etc., and enters the unit lenses 131 of the lens layer 13, as shown in Figure 6.
The external light G1 is reflected by the lens surface 132 and travels mainly downward (-Y side) within the screen 10, exiting from the surface of the screen 10 on the image source side toward the lower side of the screen 10, or attenuating within the screen 10. Therefore, the external light G1 does not reach the observer O directly, and even if it does reach the observer O, the amount of light is significantly less than that of the image light L1.

External light G2 is incident on the non-lens surface 133 and is absorbed by the rear surface protection layer 15 .
Although not shown, external light incident on the screen 10 from the rear side (−Z side) is absorbed by the rear surface protective layer 15 .
Therefore, the screen 10 can suppress a decrease in image contrast caused by external light, and can display good images even in a bright room environment.

Here, samples 1 to 7 having surface layers 11 with different transmission haze values were prepared, screens 10 including these samples were manufactured, and the peak gain, viewing angle, whether or not bright lines were visible, and so on were compared.
In all of the samples 1 to 7 of the surface layer 11, the arrangement pitch P1 of the unit surface lenses 111 is P1=100 μm, and the lens height h1 is h1=15 μm.
In addition, in samples 1 to 6, fine irregularities are formed on the surface of the unit surface lens 111 by blasting, whereas in sample 7, the surface of the unit surface lens 111 is not blasted, and the surface of the unit surface lens 111 is a smooth surface.
The fine uneven shape on the surface of the unit surface lenses 111 of Samples 1 to 6 is formed by blasting the lenticular lens shape of the surface layer 11 .

The blasting material used in the blasting of samples 1 to 6 was glass beads with an average particle size of 45 μm. The distance from the outlet through which the blasting material was projected to the apex t1 of the unit surface lens 111 was 40 mm. The number of passes of the blasting material on each sample, the blasting pressure, which is the pressure when the blasting material was projected, and the obtained transmission haze value of each sample are as follows:
For Sample 1, the number of projections (passes) of the blast material in the blast processing was 8, and the blast pressure (pressure for projecting the blast material) was 0.5 MPa. The transmission haze value of Sample 1 was 93.88%.
For sample 2, the number of times the blast material was projected in the blast processing was 8, and the blast pressure was 0.3 MPa. The transmission haze value of sample 2 was 92.50%.

For sample 3, the number of times the blast material was projected in the blast processing was 8, and the blast pressure was 0.15 MPa. The transmission haze value of sample 3 was 89.59%.
For sample 4, the blasting process was performed with the blast material projected four times at a blast pressure of 0.3 MPa. The transmission haze value of sample 4 was 92.00%.
For sample 5, the number of times the blast material was projected in the blast processing was 12, and the blast pressure was 0.3 MPa. The transmission haze value of sample 5 was 92.48%.
For sample 6, the number of times the blast material was projected in the blast processing was 8, and the blast pressure was 0.23 MPa. The transmission haze value of sample 6 was 91.22%.
As described above, no blasting process was performed on Sample 7. The transmission haze value of Sample 7 was 86.18%.

The transmission haze value of each sample is the ratio of diffuse transmittance to total light transmittance, and is obtained by measurement using a haze meter, etc. Here, the transmission haze values of Samples 1 to 7 were measured using a haze meter (NDH7000SP, manufactured by Nippon Denshoku Industries Co., Ltd.) as described above.
As described above, the transmission haze value of the surface layer 11 is preferably 91% or more and 94% or less. Therefore, Samples 1, 2, 4, 5, and 6 are surface layers 11 of the examples, and Samples 3 and 7 are surface layers 11 of the comparative examples.

Screens 10 of measurement examples 1 to 14 were fabricated having the surface layer 11 of each of these samples 1 to 7, and image light was actually projected from an image source LS to measure the peak gain, the 1/2 angle αH [°] in the horizontal direction of the screen, and the black luminance [cd/ ^m2 ] at point A, which is the geometric center of the screen.
The screens of Measurement Examples 1 to 7 and the screens of Measurement Examples 8 to 14 have different materials for the reflective layer 14 other than the surface layer 11, but otherwise have the same configuration.
The reflective layer 14 of the screens in the measurement examples 1 to 7 was formed from an aluminum flake mixed paint, had a thickness of about 10 μm, and had a reflectance of about 59%.
The reflective layer 14 of the screens of Measurement Examples 8 to 14 was formed from an aluminum flake mixed paint, had a thickness of about 10 μm, and had a reflectance of about 69%.
The screen in each measurement example has a screen size of 75 inches, a vertical dimension of 948 mm, and a horizontal dimension of 1675 mm.

The screens in measurement examples 1 and 8 have the surface layer 11 of sample 1 and correspond to the screens in the examples. The screens in measurement examples 2 and 9 have the surface layer 11 of sample 2 and correspond to the screens in the examples. The screens in measurement examples 3 and 10 have the surface layer 11 of sample 3 and correspond to the screens in the comparative examples. The screens in measurement examples 4 and 11 have the surface layer 11 of sample 4 and correspond to the screens in the examples. The screens in measurement examples 5 and 12 have the surface layer 11 of sample 5 and correspond to the screens in the examples. The screens in measurement examples 6 and 13 have the surface layer 11 of sample 6 and correspond to the screens in the examples. The screens in measurement examples 7 and 14 have the surface layer 11 of sample 7 and correspond to the screens in the comparative examples.

The peak gain PG indicates the maximum value of the gain ((brightness/illuminance) x π) calculated from the illuminance at the incident surface where light (white light) is projected from the image source LS onto the screen and the brightness of the light reflected by the reflective layer and emitted from the screen. Here, the illuminance was measured by placing an illuminance meter (T-10A manufactured by Konica Minolta) on point A, which is the geometric center of the screen screen of each measurement example, and the brightness was measured by placing a luminance meter (LS-110 manufactured by Konica Minolta) at a position 3 m away from point A, which is the geometric center of the screen of each measurement example, on the observer side in the normal direction of the screen surface. In addition, the angle of incidence of light at point A is 59 degrees, and the image source LS is located 686.5 mm downward from the geometric center A on the observer side of the screen of each measurement example and 415 mm toward the image source side (+Z side) in the normal direction (Z direction) of the screen surface.

The half angle αH in the left-right direction of the screen is used to evaluate the viewing angle. When the angles K at which the light incident on the screen, reflected by the reflective layer 14, and emitted from the screen has a peak luminance are K1 and K2, respectively, and the angle changes from the angle K of the peak luminance to the angles K1 and K2 at which the luminance is half the peak luminance are ΔK1 (where K+ΔK1=K1) and ΔK2 (where K+ΔK2=K2), respectively, the half angle αH in the left-right direction of the screen corresponds to the average of the absolute values of these angle changes, i.e., (|ΔK1|+|ΔK2|)/2.
A spectrophotometer (UV-Vis-NIR spectrophotometer V-670 manufactured by JASCO Corporation) was used to measure the 1/2 angle αH in the left-right direction of the screen. In addition, in measuring the 1/2 angle αH, the position of the image source LS that projects light onto the screen in each measurement example is the same as that in measuring the peak gain.

Black luminance refers to the luminance of the screen surface when no image is displayed on the screen in a bright room environment. This black luminance is the average value of the results of measuring point A, which is the geometric center of the screen image, three times in a bright room environment with a luminance meter (LS-110 manufactured by Konica Minolta) placed 3 m away from point A, which is the geometric center of the screen surface of each measurement example, toward the image source side (+Z side) in the normal direction of the screen surface. In addition, a bright room environment is defined as a state in which a light source (fluorescent lamp) is located 45° above point A, which is the geometric center of the screen surface, and the illuminance at point A is 100 lx.

The visibility of bright lines was evaluated by projecting white light from the image source LS onto the screen of each measurement example, and having an observer observe the screen from a point 3 m away from point A, which is the geometric center of the screen's image, toward the image source (+Z side), to see if bright lines were visible on the screen.

Table 1 below shows the transmission haze values of surface layer 11 samples 1 to 7, as well as the measurement results of the peak gain, half angle αH in the horizontal direction of the screen, and black luminance of the screen in measurement examples 1 to 14.

As shown in Table 1, in the screens of Measurement Examples 3, 7, 10, and 14 in which the transmission haze value of the surface layer 11 was less than 91%, the peak gain and the 1/2 angle αH were sufficient, and the black luminance was also sufficiently low, but bright lines were observed and the image quality was reduced.
On the other hand, in the screens of Measurement Examples 1, 2, 4, 5, 6, 8, 9, 11, 12, and 13 in which the transmission haze value of the surface layer 11 was 91% or more, the peak gain and the 1/2 angle αH were sufficient, the black luminance was sufficiently low, no bright lines were observed, and good images were displayed. In other words, if the transmission haze value of the surface layer 11 is 91% or more, the effect of suppressing bright lines can be obtained regardless of the material of the reflective layer 14.
In addition, if the transmission haze value of the surface layer 11 is greater than 94%, the effect of suppressing bright lines can be obtained, but this is not preferable because the image light displaying the image is diffused too much, resulting in a decrease in peak gain and an increase in black luminance.

The screen 10 of this embodiment has a surface layer 11 in which unit surface lenses 111 are arranged, and the transmission haze value of the surface layer 11 is 91% or more and 94% or less, so that it is excellent in terms of front luminance and viewing angle in the left-right direction of the screen, and can display good images by suppressing bright lines caused by the laser light source of the image source LS.

(Other embodiments of the screen 10)
7 is a diagram for explaining a layer structure in another embodiment of the screen 10. Fig. 7 shows a cross section of the screen 10 corresponding to the screen 10 shown in Fig. 2.
A screen 10A of another embodiment shown in Figure 7 (a) has, in the thickness direction, a surface layer 11, a transparent resin layer 12, a bonding layer 16, a colored layer 17, a lens layer 13, a reflective layer 14, and a rear surface protective layer 15, in that order from the image source side (+Z side).
The colored layer 17 is a layer that is colored with a dye or pigment of a dark color such as gray or black to achieve a predetermined transmittance. The colored layer 17 is located on the back surface side (-Z side) of the bonding layer 16, and is bonded to the transparent resin layer 12 via the bonding layer 16. The colored layer 17 is a layer that serves as a base material for forming the lens layer 13, and is laminated on the back surface side of the lens layer 13.
The colored layer 17 has a function of absorbing a part of unnecessary external light such as illumination light and stray light that enters the screen 10, thereby improving the contrast of the image.

The colored layer 17 is formed of, for example, PET resin containing a coloring material such as a dark color dye or pigment such as black, PC resin, acrylic resin, acrylic-styrene resin, TAC resin, PEN (polyethylene terenaphthalate) resin, or the like.
From the viewpoint of displaying a good image, the colored layer 17 preferably has a light transmittance (total light transmittance) of 50 to 80%, more preferably 60 to 70%. If the transmittance of the colored layer 17 is smaller than this range, too much image light is absorbed, lowering the contrast of the image, which is not preferred. Also, if the transmittance of the colored layer 17 is larger than this range, it is not preferred because a sufficient absorption effect of external light and stray light cannot be obtained.

The colored layer 17 preferably has a thickness of 25 to 50 μm. If the colored layer 17 is thinner than this range, it may not be possible to obtain a sufficient absorption effect of external light and stray light. If the colored layer 17 is thicker than this range, it may not be possible to obtain the flexibility that allows the screen 10 to be rolled up.
The colored layer 17 of the screen 10A in another embodiment is, for example, a sheet-like member made of polyethylene terephthalate resin having a thickness of approximately 38 μm and colored black and transparent with a coloring agent or the like, and its light transmittance is 70%.

The bonding layer 16 is a layer formed from an adhesive or pressure-sensitive adhesive having optical transparency, and has the function of bonding two adjacent layers (the transparent resin layer 12 and the colored layer 17 in the screen 10A of FIG. 6(a)) together via this layer.
The bonding layer 16 is formed using an acrylic, epoxy, urethane resin, or the like.
The thickness of the bonding layer 16 is preferably 5 to 30 μm. If the thickness of the bonding layer 16 is smaller than this range, sufficient bonding properties may not be obtained. If the thickness of the bonding layer 16 is larger than this range, handling properties may be reduced, or bonding may take a long time, resulting in reduced productivity.
The bonding layer 16 of the screen 10A is formed using an adhesive made of acrylic resin, and has a thickness of 25 μm.

Even with such a screen 10A, a good viewing angle and front brightness can be obtained, and good images can be displayed with reduced visibility of bright lines. Furthermore, by using such a screen 10A, the colored layer 17 absorbs stray light and external light, allowing images with higher contrast to be displayed.

Moreover, the screen 10B of another embodiment shown in FIG. 7(b) has, in the thickness direction, a surface layer 11, a colored layer 17, a bonding layer 16, a transparent resin layer 12, a lens layer 13, a reflective layer 14, and a rear surface protective layer 15, in that order from the image source side (+Z side).
In the screen 10B, the colored layer 17 is laminated on the surface layer 11 on the image source side, and serves as a base material for the surface layer 11.
The bonding layer 16 bonds the colored layer 17 and the transparent resin layer 12 together.
Even in the case of using such a screen 10B, a good viewing angle and front luminance can be obtained, and a good image in which the visibility of bright lines is suppressed can be displayed. Moreover, by using such a screen 10B, the colored layer 17 absorbs stray light and external light, and an image with higher contrast can be displayed.

Moreover, a screen 10C of another embodiment shown in FIG. 7( c) includes, in the thickness direction, a surface layer 11, a transparent resin layer 12 (first transparent resin layer), a bonding layer 16, a colored layer 17, a second bonding layer 19, a second transparent resin layer 18, a lens layer 13, a reflective layer 14, and a back surface protective layer 15, in that order from the image source side (+Z side).
The second transparent resin layer 18 is a layer having optical transparency, is a layer located on the back surface side (−Z side) of the second bonding layer 19 , and is a layer that serves as a substrate (base) of the lens layer 13 .
The second transparent resin layer 18 can be formed using the same material as the transparent resin layer 12, and may be formed using the same components as the transparent resin layer 12. Like the aforementioned transparent resin layer 12, the second transparent resin layer 18 is formed from polyethylene terephthalate, and its thickness, etc. are also the same as those of the transparent resin layer 12.
The second bonding layer 19 is made of the same material as the bonding layer 16 described above, and in the screen 10C, bonds the colored layer 17 and the second transparent resin layer 18 together.

Even with this type of screen 10C, a good viewing angle and front brightness can be obtained, and good images can be displayed with reduced visibility of bright lines. Furthermore, with this type of screen 10C, the colored layer 17 absorbs stray light and external light, allowing images with higher contrast to be displayed.

(Modifications)
The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the scope of the present invention.
(1) In the embodiment, the surface layer 11 may be a layer having one or more appropriate functions such as a hard coat function, an antiglare function, an antireflection function, an ultraviolet absorbing function, an antifouling function, an antistatic function, etc., or may be formed by laminating a plurality of layers having desired functions. In addition, a touch panel layer or the like may be provided as the surface layer 11.

(2) In the embodiment, an example is shown in which the lens layer 13 has a circular Fresnel lens shape, but this is not limited thereto, and the lens layer 13 may have a linear Fresnel lens shape.

(3) In the embodiment, an example in which the reflective layer 14 is formed on the lens surface 132 has been shown, but this is not limiting. For example, the reflective layer 14 may be formed only on a portion of the lens surface 132 (the area where the image light is incident), or may be formed on the lens surface 132 and the non-lens surface 133.

(4) In the embodiment, the back surface protective layer 15 has light absorbing properties, but the present invention is not limited thereto, and the back surface protective layer 15 may not have light absorbing properties, and the back surface side of the back surface protective layer 15 may be covered with a flexible light-resistant cloth or resin light-shielding screen, a layer for improving scratch resistance, or the like. In addition, when a decrease in contrast due to external light from the back surface side is unlikely to occur in the usage environment of the screen, the back surface protective layer 15 may not have light absorbing properties, and the screen 10 may not have the light-shielding screen or the like.
In addition, the back surface protective layer 15 may be made of flexible paper, nonwoven fabric, resin sheet, etc., and may be laminated on the back surface side of the lens layer 13 and the reflective layer 14 via a layer of adhesive or bonding agent (not shown).

(5) In the embodiment, an example is shown in which lens surface 132 and non-lens surface 133 are flat surfaces. However, this is not limited to the above. Lens surface 132 and non-lens surface 133 may have a curved surface in part, or may be a combination of a curved surface and a flat surface.
Furthermore, at least one of the lens surface 132 and the non-lens surface 133 may be configured to be composed of a plurality of flat surfaces (so-called folded surface).

(6) In an embodiment, the unit lens 131 may have a polygonal shape formed by three or more surfaces.

(7) In the embodiment, the image source LS is disposed below the screen 10 in the vertical direction (on the -Y side), but this is not limiting. For example, the image source LS may be disposed above the screen 10 in the vertical direction (on the +Y side). In this case, the position of the image source LS in the vertical direction corresponds to the position of point C, which is the Fresnel center, and the screen 10 is used with its up-down direction inverted.

(8) In the embodiment, the screen 10 is shown to have a flexible shape that can be rolled up and stored when not in use, but the present invention is not limited to this. For example, a highly rigid support plate (not shown) may be laminated integrally with the rear side, so that the screen 10 has a substantially flat shape when in use and when not in use. By adopting such a shape, the flatness of the screen 10 can be improved.

The present embodiment and its variations can be used in appropriate combinations, but detailed explanations will be omitted. Furthermore, the present invention is not limited to the embodiments described above.

REFERENCE SIGNS LIST 1 Image display device 10 Screen 10A, 10B, 10C Screen 11 Surface layer 111 Unit surface lens 12 Transparent resin layer 13 Lens layer 14 Reflective layer 15 Rear surface protective layer LS Image source

Claims (8)

a reflective screen that reflects the image light projected from the image source and displays it so that it can be viewed ;
an image source that projects image light onto the reflective screen;
An image display device comprising:
In the thickness direction of the reflective screen, a surface side onto which the image light is projected is defined as an image source side, and the opposite side is defined as a back side,
The reflective screen is
a lens layer having a Fresnel lens shape on a rear surface side in which unit lenses having a lens surface and a non-lens surface and convex on a rear surface side are arranged;
a reflective layer formed on at least a part of the lens surface and reflecting light;
a surface layer that is disposed closest to the image source, has an optical shape in which unit optical shapes are arranged on a surface on the image source side, and has a rough surface on the image source side;
Equipped with
The transmission haze value of the surface layer is 91% or more and 94% or less,
The image source is a laser light source;
An image display device comprising: 2. The image display device according to claim 1,
the unit optical shapes are convex toward the image source side, are formed to extend in a strip shape in the vertical direction of the screen of the reflective screen, and are arranged in the horizontal direction of the screen;
An image display device comprising: 3. The image display device according to claim 2,
The surface layer has an optical shape formed on a surface facing an image source, the optical shape being a lenticular lens shape in which unit surface lenses, which are unit optical shapes, are arranged;
the unit surface lenses are arranged in the left-right direction of the screen with the top-bottom direction of the screen being the ridgeline direction when the reflective screen is in use;
An image display device comprising: 2. The image display device according to claim 1,
the Fresnel lens shape is a circular Fresnel lens shape, and the optical center thereof is located outside the display area of the reflective screen;
An image display device comprising: 2. The image display device according to claim 1,
the reflection-type screen is provided with a colored layer between the surface layer and the lens layer, the colored layer being colored to a predetermined density;
An image display device comprising: 6. The image display device according to claim 5,
the reflective screen includes a transparent resin layer having optical transparency on a rear side of the surface layer,
the colored layer is provided between the transparent resin layer and the lens layer;
An image display device comprising: 6. The image display device according to claim 5,
the reflective screen includes a transparent resin layer having optical transparency on the image source side of the lens layer,
the colored layer is provided between the surface layer and the transparent resin layer;
An image display device comprising: 6. The image display device according to claim 5,
The reflective screen is
a first transparent resin layer having optical transparency on a rear surface side of the surface layer;
a second transparent resin layer having optical transparency on the image source side of the lens layer;
the colored layer is provided between the first transparent resin layer and the second transparent resin layer;
An image display device comprising:

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