Reflective transparent member and image display system

Abstract

Provided are a reflective transparent member and an image display system with which it is possible to prevent a decrease in reflected light utilization efficiency while increasing a region of high brightness.　The reflective transparent member comprises a first transparent layer having an uneven surface, a reflective layer formed on the uneven surface, and a second transparent layer formed on the uneven surface on which the reflective layer is formed so as to fill in the unevenness. The full width at half maximum of the brightness distribution in a first direction due to reflected light is at least 20% more than the full width at half maximum of the brightness distribution in a second direction orthogonal to the first direction, and at least the brightness distribution in the first direction exhibits a top hat shape.

Description

[Technical Field]

[0001] The present invention relates to a reflective transparent member and an image display system. [Background technology]

[0002] 2. Description of the Related Art A reflective transparent screen described in Patent Document 1, for example, is a reflective screen that displays an image projected from a projector in a visible manner and also allows an image on the back of the screen to be observed.

[0003] The reflective transparent screen described in Patent Document 1 exhibits relatively high brightness over a wide area of ​​the screen. As shown in FIG. 14, the reflected light intensity distribution of the reflective transparent screen is Gaussian. In FIG. 14, the horizontal axis x indicates a certain direction parallel to the plane of the screen. Hereinafter, relatively high brightness will be referred to as "medium brightness." Furthermore, relatively high reflected light intensity will be referred to as "medium reflected light intensity." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 110961 Summary of the Invention [Problem to be solved by the invention]

[0005] Referring to FIG. 14, when the reflective transparent screen described in Patent Document 1 is used, it can be seen that the range of high reflected light intensity, i.e., the region near the peak value, is narrow. That is, since the range of high brightness (see region P in FIG. 14) is narrow, the brightness corresponding to the desired light-focusing range (e.g., the region where the observer is present) is high. However, even in regions outside the desired light-focusing range (e.g., the region where the observer is not present), the reflected light intensity is moderate (see region Q in FIG. 14). Note that in FIG. 14, B indicates the peak value, and B / 2 indicates half the peak value. Furthermore, while FIG. 14 shows the reflected light intensity distribution in the x direction, when the reflective transparent screen described in Patent Document 1 is used, a similar reflected light intensity distribution is exhibited in the y direction, which is perpendicular to the x direction, on the same plane.

[0006] When the reflective transparent screen described in Patent Document 1 is used, a medium level of brightness is exhibited over a wide area of ​​the screen, but the area near the peak value of the reflected light intensity is narrow. Furthermore, since the reflected light intensity is relatively high even in areas where no observer is present, it can be said that the utilization efficiency of the reflected light is reduced.

[0007] An object of the present invention is to provide a reflective transparent member and an image display system that can prevent a decrease in the utilization efficiency of reflected light while widening the high brightness area. [Means for solving the problem]

[0008] In the present invention, the reflective transparent member includes a reflective transparent screen, a reflective diffraction grating, a radio wave reflective transparent element, a HUD (head-up display), and the like. The reflective transparent component according to the present invention comprises a first transparent layer having an uneven surface, a reflective layer on the uneven surface, and a second transparent layer formed on the uneven surface of the reflective layer so as to fill the unevenness, and is characterized in that the full width at half maximum of the luminance distribution in a first direction due to reflected light is 20% or more greater than the full width at half maximum of the luminance distribution in a second direction perpendicular to the first direction, and the luminance distribution in at least the first direction exhibits a top hat shape. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain a reflective transparent member and an image display system that can prevent a decrease in the utilization efficiency of reflected light while widening the high brightness region. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram conceptually showing the function of a reflective transparent member according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a cross section of a main part of a reflective transparent member. [Figure 3] FIG. 2 is a perspective view showing a unit lens that constitutes a part of the reflective transparent member of the first embodiment. [Figure 4] 10A and 10B are three-view diagrams for explaining an example of a first reference direction and a second reference direction. [Figure 5] FIG. 4 is an explanatory diagram for explaining an example of a first reference direction and a second reference direction. [Figure 6] FIG. 2 is an explanatory diagram for explaining an example of the structure of a reflective transparent member according to the first embodiment. [Figure 7] FIG. 1 is a cross-sectional view showing an example of the structure of an image projection structure. [Figure 8] FIG. 2 is a cross-sectional view showing an example of the structure of a reflective transparent member. [Figure 9] FIG. 10 is an explanatory diagram for explaining an example of the structure of a reflective transparent member according to the second embodiment. [Figure 10] FIG. 2 is an explanatory diagram showing the reflected light intensity distribution when light is incident on a screen. [Figure 11] FIG. 10 is an explanatory diagram for explaining a preferable distribution of reflected light intensity. [Figure 12] 10 is an explanatory diagram showing an example of distribution of the shapes of unit lenses 110. FIG. [Figure 13] FIG. 10 is an explanatory diagram showing parameter values ​​and the like in Examples and Comparative Examples. [Figure 14] 1 is an explanatory diagram showing the reflected light intensity distribution when the reflective transparent member described in Patent Document 1 is used. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification, the viewer side relative to a reflective transparent member (hereinafter referred to as a transparent screen) is referred to as the front, and the side opposite the viewer relative to the transparent screen is referred to as the rear.

[0012] FIG. 1 is an explanatory diagram conceptually illustrating the function of a reflective transparent member according to the present invention. As shown in FIG. 1, a projector 200, which is an example of a movie projector, is installed at a predetermined position in front of a transparent screen 100. A general projector can be used as the projector 200. The transparent screen 100 reflects light (incident light) of an image from the projector 200. Light (reflected light) from most of the area (e.g., the entire area) of the transparent screen 100 is reflected toward an observer 300. Note that while FIG. 1 shows the projector 200 and the observer 300 as being at the same height, in reality the projector 200 is installed above, below, to the left, or to the right of the observer 300.

[0013] FIG. 2 illustrates a cross section (longitudinal cross section) of a main part of a transparent screen 100 of this embodiment. As shown in FIG. 2, the transparent screen 100 includes a first transparent layer 32 having an uneven surface, a reflective layer 40 formed on the uneven surface of the first transparent layer 32, and a second transparent layer 52 formed on the reflective layer 40. The second transparent layer 52 is formed on the reflective layer 40 so as to fill the unevenness. A surface 51 of the second transparent layer 52 opposite the reflective layer 40 may be a flat plane or a curved surface. Furthermore, a back surface (reference surface) 31 of the first transparent layer 32 may be a flat plane or a curved surface.

[0014] When the manufactured transparent screen 100 is put to practical use, the second transparent layer 52 is located in the front, i.e., on the viewer side. A system including the transparent screen 100 and the projector 200 is an image display system.

[0015] First embodiment. 3 is a perspective view showing a unit lens 110 constituting a part of the transparent screen 100 of the first embodiment. The surface shape of the first transparent layer 32 of the transparent screen 100 (corresponding to the shape of the reflective layer 40) is a shape in which the unit lenses 110 are arranged. Specifically, the surface shapes of the plurality of unit lenses 110 realize the unevenness of the first transparent layer 32. In other words, the surface shape of the reflective layer 40 is realized by the surface shapes of the plurality of unit lenses 110.

[0016] Hereinafter, the lenses that make up the unit lens 110 are also referred to as small lenses 1101 to 1109.

[0017] Fig. 3 illustrates a unit lens 110 including 3 × 3 (= 9) small lenses 1101 to 1109. Fig. 3 also illustrates small lenses 1101 to 1109 that have a rectangular shape when viewed from the front (shape in plan view), but the shape of the small lenses is not limited to a rectangle and may be a polygon with three or more sides or a circle. In FIG. 3, the x direction represents a first reference direction shown in FIG. 4, which will be described later, and the y direction represents a second reference direction shown in FIG.

[0018] Fig. 4 is a three-view diagram for explaining the "first reference direction" and "second reference direction" for the small lenses 1101 to 1109 used in this embodiment and embodiments described later. Fig. 4(A) is a front view, Fig. 4(B) is a side view, and Fig. 4(C) is a plan view. Note that Fig. 4 illustrates three small lenses 1101 to 1103.

[0019] The "first reference direction" is, for example, one direction that forms the largest angle (inclination angle θ1) in a cross-sectional view with respect to the reference plane 41 (see FIG. 4A). As an example, the reference plane 41 is a plane that is perpendicular to the normal to the transparent screen 100. The "second reference direction" is, when the "first reference direction" is selected, a direction that forms the largest angle (inclination angle θ2) in a cross-sectional view in a direction perpendicular to the line obtained by projecting the line indicating the "first reference direction" onto the reference plane (see FIG. 4C).

[0020] The curvature in the first reference direction and the curvature in the second reference direction of each of the small lenses 1101 to 1109 may be the same or different. Here, the curvature in the first reference direction or the second reference direction may be 0, i.e., the surface may be flat.

[0021] 5, the height direction of the transparent screen 100 may be defined as the second reference direction, and the longitudinal direction of the transparent screen 100 (the direction perpendicular to the second reference direction) may be defined as the first reference direction. Even when the transparent screen 100 has a curved shape that is concave toward the back side (rear side) when viewed from the front, the height direction of the transparent screen 100 is the second reference direction. The first reference direction is, for example, parallel to a plane perpendicular to the normal line at the center of the transparent screen 100 and perpendicular to the second reference direction.

[0022] As shown in FIG. 6 , in this embodiment, the surface shape of the first transparent layer 32 of the transparent screen 100 is realized by arranging a large number of unit lenses 110 over the entire surface. The angle (tilt angle θ1) of each unit lens 110 in the first reference direction and the angle (tilt angle θ2) in the second reference direction are set so that incident light is reflected toward a viewer 300 present in a specific area across the entire area of ​​the transparent screen 100. That is, the surface shape of the first transparent layer 32 (corresponding to the shape of the reflective layer 40) is realized by the shape of the unit lenses 110 whose angles in the first reference direction and the second reference direction are set as described above. The tilt angle θ1 is defined as a positive value when the angle formed by the unit lenses 110 is counterclockwise when viewed from the second reference direction side with respect to the reference plane of the first reference direction, and as a negative value when it is clockwise. When viewed from the first reference direction side relative to the reference plane of the second reference direction, the tilt angle θ2 is defined as a positive value when the angle formed by the unit lenses 110 is counterclockwise and as a negative value when it is clockwise.

[0023] In reality, the uneven surface of the reflective layer 40 (corresponding to the uneven surface of the first transparent layer 32) is formed over the entire area of ​​the transparent screen 100 in one step.

[0024] Furthermore, assuming that the transparent screen 100 is incorporated into a windshield of a vehicle, the specific area is typically the driver's seat and passenger seat. The specific area may also be the rear seat. Furthermore, assuming that there are multiple observers 300, unit lenses of different shapes are used, and each unit lens is configured to reflect light to each observer. Note that, as an example of a case in which there are multiple observers 300, there may be an observer 300 in the driver's seat and passenger seat inside the vehicle. There may also be an example in which there are multiple observers 300 in the rear seat inside the vehicle. Furthermore, even if there is actually only one observer 300, if the observer 300 moves around inside the vehicle, it can be considered that there are essentially multiple observers 300.

[0025] 6 is composed of a surface having an inclination angle that reflects light incident on the projection area toward the viewer. In the first embodiment, the surface shape of the first transparent layer 32 of the transparent screen 100 is such that the unit lenses 110, the shapes of which are determined as described above, are arranged across the entire area of ​​the transparent screen 100. In other words, the transparent screen 100 has unit lenses 110 that focus reflected light to a focusing point, and has a structure in which the unit lenses 110, each having the same shape, are arranged two-dimensionally when viewed from above (when observed from the surface side of the transparent screen 100).

[0026] The tilt angle of each unit lens 110 is set by randomly selecting a focusing point of reflected light set at an arbitrary position. That is, the tilt angle of each unit lens 110 is set so that incident light is reflected toward the randomly selected focusing point. In addition, the random ratio of focusing points selected for each unit lens 110 (the probability that each focusing point is selected) is set to an arbitrary ratio.

[0027] Furthermore, the surface of the unit lens may be provided with minute irregularities, the details of which will be described later.

[0028] 7 is a cross-sectional view showing an example of the structure of an image projection structure 120 that is the base material of a transparent screen 100 according to the present invention. In the structure shown in FIG. 7, the image projection structure 120 is formed on a transparent base material 60.

[0029] The transparent substrate 60 is, for example, glass or transparent resin. When glass is used as the transparent substrate 60, soda lime glass or alkali-free glass is preferably used. The glass may be chemically strengthened, hard coated, or the like to improve durability. When a transparent resin is used as the transparent substrate 60, polycarbonate, PET, PEN, cycloolefin polymer, or the like is preferably used. The transparent substrate 60 is preferably one that does not have birefringence. Furthermore, it is preferable to select a transparent substrate 60 with a thickness that maintains its durability as a substrate.

[0030] The first transparent layer 32 is preferably a transparent resin layer. Examples of transparent resins constituting the transparent resin layer include acrylic resin, epoxy resin, polycarbonate resin, silicone resin, unsaturated polyester resin, and mixed resins thereof. The resin is preferably a photocurable resin, a thermosetting resin, or a thermoplastic resin. The transmittance of the first transparent layer 32 is preferably 50% or more, more preferably 75% or more, and even more preferably 90% or more.

[0031] In addition, it is preferable that the first transparent layer 32 be formed from a resin with a refractive index of 1.4 or more, since this reduces the angle of inclination at which the image light is refracted when it enters the first transparent layer 32 and reflected toward the viewer.

[0032] The first transparent layer 32 may be composed of multiple layers and may contain a filler. When composed of multiple layers, the difference in refractive index between the layers or between the filler and the resin layer serving as a binder is preferably 0.05 or less to prevent cloudiness, more preferably 0.02 or less to improve transparency, and even more preferably 0.01 or less to prevent deterioration of rear visibility similar to halo-like blurring. An example of the filler is silica filler.

[0033] The second transparent layer 52 is preferably a transparent resin layer. The difference between the refractive index of the first transparent layer 32 and the refractive index of the second transparent layer 52 is preferably small, more preferably 0.05 or less, for example. The second transparent layer 52 and the first transparent layer 32 may be formed of the same material or different materials, but are preferably formed of the same material. When the second transparent layer 52 and the first transparent layer 32 are formed of the same transparent resin, the refractive indices of both can be easily matched. Furthermore, as with the first transparent layer 32, the transmittance of the second transparent layer 52 is preferably 50% or more, more preferably 75% or more, and even more preferably 90% or more.

[0034] The second transparent layer 52 may be composed of multiple layers and may contain a filler. When composed of multiple layers, the difference in refractive index between the layers or between the filler and the resin layer serving as a binder is preferably 0.05 or less to prevent cloudiness, more preferably 0.02 or less to improve transparency, and even more preferably 0.01 or less to prevent deterioration of rear visibility similar to halo-like blurring.

[0035] The reflective layer 40 may be a single-layer or multi-layer metal or dielectric film, or a combination thereof. Examples of the reflective layer 40 include a film formed of a metal selected from Au, Ag, Pt, Cu, Ru, Ir, Rh, Os, Bi, Nd, Al, Ni, Ti, Pd, Co, Si, Ta, W, Mo, and Ge, an alloy containing two or more of these metals, or a material primarily composed of an oxide such as NbO or SiO2. A portion of the light incident on the reflective layer 40 is transmitted, while the other portion is reflected. A film formed of Ag or Al, or an alloy of Ag and at least one metal selected from the group consisting of Pd, Au, Pt, Cu, Ru, Ir, Rh, Os, Bi, Nd, and Ge, is preferred because it easily achieves both brightness of the projected image and transmittance of the image projection structure 120.

[0036] A manufacturing example of the image projection structure 120 in the first embodiment will be described below with reference to Fig. 7. However, the manufacturing examples shown below are merely illustrative of the present invention, and the present invention is not limited to these.

[0037] A PET film (thickness: 0.075 mm) was prepared as a support member (transparent substrate 60). A mold having a desired shape (such as the shapes shown in FIGS. 3 and 4) on its surface was prepared as a molding tool. The mold had a shape corresponding to the shape of a unit lens (hereinafter also referred to as a unit shape) described below.

[0038] The mold used can be processed not only by cutting with a tool, but also by laser processing or photolithography. When processed by laser processing or photolithography, the peaks and valleys of the processed shape are rounded, which reduces the haze value. In addition, since the reproducibility of the peaks and valleys of the processed shape is lower than with cutting with a tool, the periodicity of the shape is eliminated, making it possible to suppress diffraction.

[0039] Next, a first resin was applied onto the PET film by a die coating method to form a first transparent layer 32. As the first resin, a bifunctional UV-curable acrylic resin (acrylic equivalent: 152) was used.

[0040] Next, a molding die was placed on the first resin so that the side with the concave and convex portions was in contact with the first resin. In this state, 1000 mJ of UV light was irradiated from the opposite side of the molding die to cure the first resin, thereby forming a first transparent layer 32.

[0041] Thereafter, the molding die was removed, and a first transparent layer 32 (thickness: about 35 μm) having an uneven surface was formed on the PET film. The unevenness of the lens, which will be described later, had been transferred to this uneven surface.

[0042] Next, an Ag—Au alloy layer was formed by sputtering on the irregular surface of the first transparent layer 32 to form the reflective layer 40. The thickness of the reflective layer 40 was 15 nm.

[0043] Next, a resin for an adhesive layer (not shown in FIG. 7) was applied by a die coating method on the reflective layer 40. The resin for the adhesive layer was a linear polymer resin with a Tg of 47° C., mainly composed of a polyester resin made of dicarboxylic acid and diol, and was diluted with toluene as a dilution solvent.

[0044] The adhesive layer was then heated at 110°C for 5 minutes to remove the dilution solvent by drying, forming an adhesive layer. The adhesive layer had a molding shrinkage rate of less than 3% and a thickness of 1.5µm.

[0045] Next, a second resin, an acrylic resin similar to the first resin, was applied onto the adhesive layer by die coating.

[0046] In this state, 1000 mJ of UV light was irradiated from the second resin side to harden the second resin, thereby forming a second transparent layer 52 (thickness: approximately 35 μm). The shrinkage rate of the second transparent layer 52 was approximately 10%.

[0047] The above method produces the image projection structure 120. The adhesive layer is an optional layer, and the second transparent layer may be formed directly on the reflective layer 40.

[0048] Next, a manufacturing example of the transparent screen 100 according to the first embodiment will be described with reference to Fig. 8. However, the manufacturing examples shown below are merely illustrative of the present invention, and the present invention is not limited to these.

[0049] First, soda lime glass with a thickness of 2 mm was prepared as the first transparent substrate 10 and the second transparent substrate 11. Also, PVB films with a thickness of 0.38 mm were prepared as the first adhesive layer and the second adhesive layer (not shown in FIG. 8).

[0050] Next, a laminate was formed by laminating in order the first transparent substrate 10, the first adhesive layer, the image projection structure 120, the second adhesive layer, and the second transparent substrate 11. The laminate was then vacuum-packed and heated at 120°C for 1 hour to obtain the transparent screen 100.

[0051] 8, the transparent substrate 60 and the first transparent substrate 10 are shown as separate entities for convenience, but the transparent substrate 60 can be regarded as one embodiment of the first transparent substrate 10. Therefore, the transparent substrate 60 can be made of the same material as that described for the first transparent substrate 10. Furthermore, the transparent substrate 60 and the first transparent substrate 10 may be integrated into one transparent layer.

[0052] Second embodiment. In the first embodiment, the transparent screen 100 has a structure in which unit lenses 110 of the same shape (note: the inclination angle is not the same) are arranged over the entire surface (see FIG. 6). However, if unit lenses 110 of the same shape (flat shape) are arranged periodically, diffraction may occur, resulting in uneven brightness.

[0053] On the other hand, in the second embodiment, in order to prevent diffraction from occurring, the transparent screen 100 has a structure in which unit lenses 110 of a variety of shapes are arranged.

[0054] Fig. 9 is an explanatory diagram illustrating an example of the structure of a reflective transparent member according to the second embodiment. In the second embodiment, the shape of the first transparent layer 32 in the transparent screen 100 may be a shape in which unit lenses 110 of a plurality of different shapes are two-dimensionally arranged, or may be a shape in which unit lenses 110 of a plurality of different shapes are randomly arranged, as shown in Fig. 9. In Fig. 9, each rectangle corresponds to a unit lens 110.

[0055] The example shown in FIG. 9 is an example of a random arrangement, and in the example shown in FIG. 9, first, the center points are arranged randomly with respect to each of the first reference direction and the second reference direction.

[0056] The shape of each unit lens 110 is determined so that each of the arranged center points becomes the center point of the unit lens 110. The tilt angle of the first reference direction and the tilt angle of the second reference direction for each unit lens 110 on the transparent screen 100 are determined in the same way as those in the first embodiment.

[0057] At this time, the shape of the unit lenses 110 is determined by simulation so that light is reflected toward the location of the observer 300. Specifically, assuming that there are multiple observers 300, unit lenses 110 of multiple shapes are used, and each unit lens 110 is configured to reflect light toward a randomly selected observer.

[0058] In the second embodiment, the unit lenses 110 are arranged without periodicity, thereby preventing diffraction from occurring.

[0059] Furthermore, minute irregularities may be imparted to the surface of the unit lenses. By imparting minute irregularities, it becomes possible to scatter light within a predetermined angle. Methods for imparting minute irregularities include physical cutting of the surface of the material forming the mold (e.g., dry etching, wet etching, sandblasting, laser ablation), surface molding by extrusion molding, use of the surface structure that occurs when molding a mixed material such as fine particles, or application of a self-organizing material.

[0060] When a minute unevenness is imparted to the surface of the unit lenses, the reflective layer 40 is formed to follow the minute unevenness. In this case, since the reflective layer 40 is thinner than the minute unevenness, the surface of the reflective layer 40 has a shape that reflects the minute unevenness. Here, from the viewpoint of scattering light within a predetermined angle, it is preferable that the surface roughness of the reflective layer 40 (i.e., the surface roughness of the unit lenses 110) be in the range of 0.005 μm to 5 μm in terms of arithmetic average surface roughness Ra (JIS B0601-2001). The surface roughness Ra of the reflective surface of the reflective layer 40 can be appropriately selected depending on the desired optical performance, etc.

[0061] FIG. 10 is an explanatory diagram showing the reflected light intensity distribution when light is incident on a screen. The scattering angle will be explained with reference to FIG. 10. FIG. 10(A) shows how light from a projector 200 is incident on a transparent screen 100. FIG. 10(B) shows the reflected light intensity distribution in the direction of the largest FWHM of the transparent screen 100 according to the present invention. Assuming a situation in which an observer 300 is present inside a vehicle, as shown in FIG. 10(D), the direction of the largest FWHM (defined as the x direction) is preferably the direction connecting the driver's seat 410 and the passenger seat 420. The direction perpendicular to the x direction is defined as the y direction. The y direction is the height direction. The z direction is the traveling direction of the vehicle.

[0062] FIG. 10C shows the reflected light intensity distribution in the y direction of the transparent screen 100 according to the present invention, which is similar to the reflected light intensity distribution shown in FIG. In (B) of Figure 10, FWHM1 indicates the full width at half maximum (hereinafter also referred to as FWHM) of the reflected light intensity distribution in the x direction in front of the transparent screen 100, and in (C) of Figure 10, FWHM2 indicates the full width at half maximum of the reflected light intensity distribution in the y direction in front of the transparent screen 100.

[0063] As will be described in the following examples, in the present invention, the FWHM1 of the reflected light intensity distribution in the x direction is 20% or more larger than the FWHM2 of the reflected light intensity distribution in the y direction. That is, the present invention satisfies the following formula (1). FWHM1 ≥ FWHM2 × 120% (1) In the following examples, it is assumed that anisotropy exists when formula (1) is satisfied.

[0064] In the above embodiment and the following examples, the transparent screen 100 is fabricated to maximize the FWHM in the x direction. In other words, the x direction corresponds to the first direction in which the FWHM is maximized. The y direction corresponds to the second direction perpendicular to the first direction.

[0065] Fig. 11 is an explanatory diagram for explaining a preferable reflected light intensity distribution. The reflected light intensity distribution shown in Fig. 11 shows a top-hat type. Since brightness can be defined by the light intensity (luminous intensity) per unit area, hereinafter the expression brightness will be used instead of reflected light intensity.

[0066] As an example, as shown in Fig. 11, the peak is defined as a range where the drop in brightness is equal to or greater than a first predetermined value relative to the maximum brightness (maximum brightness) of the flat portion where brightness is at its maximum. That is, in the reflected light intensity distribution shown in Fig. 11, the lower limit of the peak is expressed by the following formula (2). Top limit = maximum brightness × (100 - first predetermined value)% (2)

[0067] 11, the range where the brightness relative to the maximum brightness is equal to or less than a second predetermined value is defined as the floor portion. In the reflected light intensity distribution, the range from the lower limit of the peak to the upper limit of the floor portion is defined as the transition portion.

[0068] As will be described in the examples below, it is preferable that the first predetermined value is 30% and the second predetermined value is 20%, and it is also preferable that the width C of the apex (see FIG. 11) is 10° or more and the width (distance) D of the transition portion (see FIG. 11) is 20° or less. That is, it is preferable that the brightness distribution in the first direction includes a peak having a width of 10° or more where the brightness is reduced by 30% or less from the maximum brightness, and the width of the transition between the lower limit of the peak and the upper limit of the floor where the brightness is 20% or less from the maximum brightness is 20° or less. In this embodiment, it is assumed that a top hat shape appears in the reflected light intensity distribution when the width C of the apex is 10° or more and the width D of the transition portion is 20° or less.

[0069] FIG. 12 is an explanatory diagram showing an example of the distribution of the shapes of the unit lenses 110 (specifically, small lenses 1101 to 1109, see FIG. 3) used in the above embodiment. As shown in FIG. 12(A), the angles of the unit lenses 110 within a predetermined area on the transparent screen 100 are measured. As an example, the predetermined area is a square measuring 2 mm in length and 2 mm in width. The lens angles are measured using a laser microscope, and the angle in the direction with the largest FWHM is taken as the tilt angle of the small lenses. In the above embodiment, it is assumed that the distance (average distance) between a small lens and its adjacent small lens is 20 μm to 150 μm. Hereinafter, the distance between the small lenses will be referred to as the distance between the concave and convex portions.

[0070] Fig. 12(B) shows an example of the distribution of the tilt angles of the lenslets when the interval between the concave and convex portions is 150 μm. In the example shown in Fig. 12(B), the tilt angles are organized into a histogram with 10 classes. The vertical axis shows the number of tilt angles (degrees) included in the range of tilt angles in each class.

[0071] Fig. 12(C) shows an example of the distribution of the tilt angles of the lenslets when the interval between the concave and convex portions is 20 μm. In the example shown in Fig. 12(C), the tilt angles are organized into a histogram with 10 classes. The vertical axis shows the number of tilt angles (degrees) included in the range of tilt angles in each class.

[0072] As shown in Figures 12(B) and 12(C), it is preferable that the minimum frequency is 50% or less of the maximum frequency, that is, it is preferable that the following formula (3) is satisfied. Minimum frequency ≦ Maximum frequency × 50% (3)

[0073] Examples and comparative examples will be described below with reference to FIG. 13. First, the parameters shown in FIG. 13 will be described. "Anisotropy" means that the reflected light intensity distribution (brightness distribution) in the x direction is different from the reflected light intensity distribution in the y direction. In the examples and comparative examples, the differences are compared in terms of FWHM. The parameters related to top hat are as described above. "Transmittance" is a value (%) measured using a method conforming to ISO 9050. Transmission haze (cloudiness) is a value measured using a method conforming to ISO 14782.

[0074] The "screen gain" is a value as follows: Light is irradiated from a light source (e.g., projector 200) perpendicularly onto the transparent screen 100, and the luminance value is measured with a luminance meter while changing the angle with respect to the transparent screen 100 within the same plane (e.g., between -80° and +80° in 5° increments). The highest value among the ratios of the measured luminance values ​​to the luminance value when the light is irradiated onto a perfect diffuser plate is taken as the screen gain.

[0075] "Image luminance" is expressed, for example, as follows: Image brightness (cd / m 2 ) = Brightness (lm) of the light source (e.g., projector 200) × Screen gain / (Projection area (m 2 ) × pi)

[0076] In the following examples (Examples 1 to 6), a transparent screen 100 was fabricated in which anisotropy was exhibited such that the FWHM of the luminance distribution in the x direction was 20% or more larger than the FWHM of the luminance distribution in the y direction, and the luminance distribution in the x direction was a top-hat type. In this case, the average tilt angle of the small lenses constituting the transparent screen 100 was set to 6°, and the ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was set to less than 50%.

[0077] [Example 1] A transparent screen 100 was produced with an x-direction FWHM (see FIG. 10B) of 80°, a y-direction FWHM (see FIG. 10C) of 30°, a peak width C (see FIG. 11) of 70°, and a transition width D (see FIG. 11) of 10°. In Example 1, the average spacing between the concave and convex portions was 50 μm, and the average tilt angle of the concave and convex portions was 6°. The ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was 30%.

[0078] In Example 1, the surface of the small lenses was subjected to a micro-irregularity treatment. A transparent screen 100 was used, with a transmittance of 75%, a transmission haze of 1.9%, and a screen gain of 0.3. The image brightness was 520 cd / m 2 is.

[0079] [Example 2] A transparent screen 100 was produced with an x-direction FWHM of 80°, a y-direction FWHM of 7°, a peak width C of 70°, and a transition width D of 10°. In Example 2, the average spacing between the concave and convex portions was 50 μm, and the average tilt angle of the concave and convex portions was 6°. The ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was 30%.

[0080] In Example 2, the surface of the small lenses was subjected to a micro-irregularity treatment. A transparent screen 100 was used, with a transmittance of 75%, a transmission haze of 1.9%, and a screen gain of 0.8. The image brightness was 1400 cd / m 2 is.

[0081] [Example 3] A transparent screen 100 was produced with an x-direction FWHM of 23°, a y-direction FWHM of 7°, a peak width C of 20°, and a transition width D of 5°. In Example 3, the average spacing between the concave and convex portions was 50 μm, and the average tilt angle of the concave and convex portions was 6°. The ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was 30%.

[0082] In Example 3, the surface of the small lenses was subjected to a micro-irregularity treatment. A transparent screen 100 was used, with a transmittance of 75%, a transmission haze of 1.9%, and a screen gain of 2.7. The image brightness was 4700 cd / m 2 is.

[0083] [Example 4] A transparent screen 100 was produced with an x-direction FWHM of 20°, a y-direction FWHM of 10°, a peak width C of 20°, and a transition width D of 2°. In Example 4, the average spacing between the concave and convex portions was 50 μm, and the average tilt angle of the concave and convex portions was 6°. The ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was 30%.

[0084] In Example 4, the surface of the small lenses was not subjected to micro-irregularity treatment. The screen used was a transparent screen 100 with a transmittance of 75%, a transmission haze of 1.9%, and a screen gain of 9. The image brightness was 15,000 cd / m 2 is.

[0085] [Example 5] A transparent screen 100 was produced with an x-direction FWHM of 20°, a y-direction FWHM of 4°, a peak width C of 20°, and a transition width D of 2°. In Example 5, the average spacing between the concave and convex portions was 50 μm, and the average tilt angle of the concave and convex portions was 6°. The ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was 30%.

[0086] In Example 5, the surface of the small lenses was not subjected to micro-irregularity treatment. A transparent screen 100 with a transmittance of 75%, a transmission haze of 1.9%, and a screen gain of 18 was used. The image brightness was 32000 cd / m 2 is.

[0087] [Example 6] A transparent screen 100 was produced with an x-direction FWHM of 20°, a y-direction FWHM of 10°, a peak width C of 20°, and a transition width D of 10°. In Example 6, the average spacing between the concave and convex portions was 100 μm, and the average tilt angle of the concave and convex portions was 6°. The ratio (minimum frequency / maximum frequency) in the frequency distribution of the tilt angle was 30%.

[0088] In Example 6, the surface of the small lenses was not subjected to micro-irregularity treatment. The screen used was a transparent screen 100 with a transmittance of 75%, a transmission haze of 1.9%, and a screen gain of 9. The image brightness was 15,000 cd / m 2 is.

[0089] When the transparent screen 100 of any of the above examples (Examples 1 to 6) is used, the region where the intensity of the collected light is high becomes wider in the x direction, so the range in which a bright image can be viewed can be made wider compared to, for example, the transparent screen described in Patent Document 1. In addition, by narrowing the width D (see FIG. 11) of the transition portion in the luminance distribution, it is possible to prevent a decrease in the utilization efficiency of reflected light.

[0090] Therefore, for example, when the transparent screen 100 is installed inside a vehicle, for example, on the front window (windshield) of the vehicle, both the observer 300 in the driver's seat and the observer 300 in the passenger seat can view a bright image. Also, when the observer 300 in the front seat of the vehicle moves in the x direction, or when the observer 300 in the rear seat moves in the x direction, the observer 300 can view a bright image before, during, or after the movement. Note that in the y direction, assuming that the range in which the bright image can be viewed does not need to be wide, the luminance distribution may be the same as the luminance distribution of the transparent screen described in Patent Document 1, for example.

[0091] Comparative Examples will be described below. In the following comparative examples (Examples 7 to 11), transparent screens in which no anisotropy or no top-hat luminance distribution occurs, or transparent screens in which no anisotropy or no top-hat luminance distribution occurs, were fabricated.

[0092] [Example 7] In Example 7, the brightness distribution in the x direction is top-hat shaped. That is, the width C of the top is 10° or more, and the width D of the transition is 20° or less. However, since the FWHM in the x direction is 28° and the FWHM in the y direction is 28°, there is no anisotropy. That is, the above formula (1) is not satisfied.

[0093] [Example 8] In Example 8, the FWHM in the x direction is 14° and the FWHM in the y direction is 12°, so there is no anisotropy. Also, in the brightness distribution in the x direction, the width C of the apex is 8.5°, which is less than 10°, so no top hat shape appears.

[0094] [Example 9] In Example 9, the FWHM in the x direction is 6° and the FWHM in the y direction is 5°, so there is no anisotropy. Also, in the brightness distribution in the x direction, the width C of the apex is 3°, which is less than 10°, so no top hat shape appears.

[0095] [Example 10] In Example 10, the FWHM in the x direction is 30° and the FWHM in the y direction is 10°, so there is anisotropy. However, the top width C is 20°, but the transition width D is 35°, which exceeds 20°, so the top hat shape does not appear.

[0096] [Example 11] In Example 11, the brightness distribution in the x direction is top-hat shaped. That is, the width C of the top portion is 10° or more, and the width D of the transition portion is 20° or less. However, since the FWHM in the x direction is 30° and the FWHM in the y direction is 30°, there is no anisotropy. That is, the above formula (1) is not satisfied.

[0097] The screens of Examples (Examples 1 to 6) are anisotropic and have a top-hat luminance distribution, so when these screens are installed on a vehicle windshield, multiple viewers can view a bright image. On the other hand, the screens of Comparative Examples (Examples 7 to 11) are not anisotropic or do not have a top-hat luminance distribution, so when the screens of the Comparative Examples are installed on a windshield, it is difficult for multiple viewers to view a bright image. [Explanation of symbols]

[0098] 10 First transparent substrate 11 Second transparent substrate 32 First transparent layer 40 reflective layer 52 Second Transparent Layer 60 Transparent base material 100 Transparent Screens 110 unit lens 1101~1109 Small Lenses 120 Image Projection Structure 200 projectors 300 Observer

[0099] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2021-156598, filed on September 27, 2021, are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims

1. a first transparent layer having an uneven surface; a reflective layer on the uneven surface; a second transparent layer formed on the uneven surface of the reflective layer so as to fill the unevenness, the full width at half maximum of the luminance distribution in a first direction due to the reflected light is 20% or more larger than the full width at half maximum of the luminance distribution in a second direction perpendicular to the first direction; The luminance distribution in at least the first direction exhibits a top-hat shape. Reflective transparent material.

2. The full width at half maximum of the luminance distribution in the first direction is maximum. The reflective transparent member according to claim 1 .

3. The top-hat luminance distribution includes a peak with a width of 10° or more, where the drop in luminance is 30% or less compared to the maximum luminance, and the width of the transition between the lower limit of the peak and the upper limit of the floor, where the drop in luminance is 20% or less compared to the maximum luminance, is 20° or less. The reflective transparent member according to claim 1 or 2.

4. In the frequency distribution of the inclination angles of the plurality of concave and convex portions included in the predetermined region, there is included a portion where the minimum frequency is 50% or less of the maximum frequency. The reflective transparent member according to claim 1 or 2.

5. the concave-convex surface is formed by a two-dimensional array of a plurality of unit lenses, The unit lens has small lenses arranged at an average interval of 20 μm to 150 μm. The reflective transparent member according to claim 1 or 2.

6. The reflective transparent member according to claim 1 , wherein the first transparent layer and the second transparent layer are transparent resin layers.

7. 7. The reflective transparent member according to claim 6, wherein the transparent resin constituting the transparent resin layer is a photocurable resin, a thermosetting resin, or a thermoplastic resin.

8. 8. The reflective transparent member according to claim 6, wherein the transparent resin constituting the transparent resin layer is an acrylic resin, an epoxy resin, a polycarbonate resin, a silicone resin, an unsaturated polyester resin, or a mixed resin thereof.

9. 3. The reflective transparent member according to claim 1, wherein the reflective layer is a single-layer film or a multi-layer film of a metal film or a dielectric film.

10. 10. The reflective transparent member according to claim 9, wherein the reflective layer is a film formed of Ag or Al alone, or an alloy of Ag and at least one metal selected from the group consisting of Pd, Au, Pt, Cu, Ru, Ir, Rh, Os, Bi, Nd, and Ge.

11. 3. The reflective transparent member according to claim 1, which is a reflective transparent screen.

12. 3. A projector comprising the reflective transparent member according to claim 1 or 2 and a projector that projects an image onto the reflective transparent member. Video display system.

Images