JP2020003812A - Transparent screen - Google Patents

Abstract

To provide a transparent screen having improved visibility of an image at an outer peripheral section thereof.SOLUTION: A transparent screen has a screen body for displaying an image projected from a front side or a rear side to a user in front and allowing the user to view a background behind, and a transparent plate for supporting the screen body. An uneven structure is formed on at least one of an end surface of the screen body and an end surface of the transparent plate. A light absorbing member for absorbing at least part of light propagating inside the transparent screen at the time of projecting the image is provided at an outer peripheral section of the transparent screen.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transparent screen.

  A normal screen displays an image projected from the front or the back to the user in front, but cannot display the back background to the user because it specializes in displaying the image (for example, see Patent Document 1). .

JP 2012-32513 A

  Transparent screens are being developed. The transparent screen has a screen main body and a transparent plate supporting the screen main body.

  The screen main body displays an image projected from the front or the back to the user in front, and allows the user to visually recognize the background in the back.

  During projection of an image, unnecessary light not contributing to image display is generated by light propagating while being repeatedly reflected inside the transparent screen. The contrast of an image may be reduced due to the brightness of unnecessary light.

  The present invention has been made in view of the above problems, and has as its main object to provide a transparent screen with improved visibility of an image on the transparent screen.

In order to solve the above problems, according to one embodiment of the present invention,
A screen body that displays an image projected from the front or the back to the user in front, and allows the user to see the background behind, and a transparent screen having a transparent plate supporting the screen body,
An uneven structure is formed on at least one of an end face of the screen main body and an end face of the transparent plate,
Further, there is provided a transparent screen, wherein a light absorbing member for absorbing at least a part of light propagating inside the transparent screen when projecting an image is provided on an outer peripheral portion of the transparent screen.

  According to one embodiment of the present invention, a transparent screen is provided in which visibility of an image on the transparent screen is improved.

FIG. 2 is a cross-sectional view of a transparent screen according to one embodiment. It is sectional drawing which shows the structure of the outer peripheral part of the transparent screen by one Embodiment. It is sectional drawing which shows the structure of the outer peripheral part of the transparent screen by a modification. FIG. 2 is a cross-sectional view illustrating a structure of a reflection type screen sheet according to one embodiment. 1 is a cross-sectional view illustrating a structure of a transmission type screen sheet according to an embodiment. It is sectional drawing which shows the structure of the transmission type screen sheet by a modification.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.

  FIG. 1 is a cross-sectional view of a transparent screen according to one embodiment. In FIG. 1, the solid line indicates the arrangement of the projector 12 when the transparent screen 20 is of a reflective type, and the broken line indicates the arrangement of the projector 12 when the transparent screen 20 is of a transmissive type. The side of the user 10 (the left side in FIG. 1) with respect to the transparent screen 20 is referred to as the front, and the side opposite to the user 10 with respect to the transparent screen 20 (the right side in FIG. 1) is referred to as the rear. The same applies to FIGS.

  The transparent screen 20 displays an image projected from the front or rear projector 12 to the front user 10 and allows the user 10 to visually recognize the back background. The rear background only needs to be visible when the image is not projected, and may be visible when the image is projected, but may not be visible.

  The transparent screen 20 may be either a flat screen or a curved screen. The curved screen may be either a screen having a convex shape toward the user 10 or a screen having a concave shape toward the user 10.

  The transparent screen 20 has a laminated plate including a plurality of transparent plates 30 and 40 and a screen body 50 provided between the plurality of transparent plates 30 and 40. Further, the transparent screen 20 has a light absorbing member 60 provided in contact with the outer peripheral portion of the laminated plate. The light absorbing member 60 may be provided over the entire outer periphery of the laminated plate, but may be provided on at least a part of the outer periphery of the laminated plate.

  The plurality of transparent plates 30 and 40 protect the screen main body 50 from both front and rear sides by sandwiching the screen main body 50 from both front and rear sides. Each of the plurality of transparent plates 30 and 40 is, for example, a glass plate. In this case, a laminated glass is obtained as a laminated plate. The thickness of the transparent plate 30 and the thickness of the transparent plate 40 can be arbitrarily selected according to the strength and design of the transparent screen 20, respectively.

  The plurality of glass plates sandwiching the screen body 50 may be either untempered glass or tempered glass. The untempered glass is obtained by forming a molten glass into a plate shape and gradually cooling it. Examples of the molding method include a float method and a fusion method. The tempered glass may be either physically tempered glass or chemically tempered glass. Physically strengthened glass is a glass plate that has been strengthened by rapidly cooling a uniformly heated glass plate from a temperature near the softening point and generating a compressive stress on the glass surface due to the temperature difference between the glass surface and the inside of the glass. . Chemically strengthened glass is one in which the glass surface is strengthened by generating a compressive stress on the glass surface by an ion exchange method or the like.

  The transparent plates 30 and 40 of the present embodiment are glass plates, respectively, but may be resin plates. Further, one of the plurality of transparent plates 30 and 40 may be a glass plate, and the other may be a resin plate. The number of transparent plates included in the laminated plate may be three or more.

  FIG. 2 is a cross-sectional view showing the structure of the outer peripheral portion of the transparent screen according to one embodiment. The screen main body 50 has, for example, a plurality of adhesive layers 51 and 52 and a screen sheet 53 sandwiched between the plurality of adhesive layers 51 and 52.

  The plurality of adhesive layers 51 and 52 are provided with the screen sheet 53 interposed therebetween, and adhere the screen sheet 53 to the plurality of transparent plates 30 and 40. The thickness of the adhesive layer 51 and the thickness of the adhesive layer 52 are not particularly limited, but are, for example, 0.01 to 1.5 mm, and preferably 0.05 to 0.5 mm.

  The plurality of adhesive layers 51 and 52 may be formed of different materials, but are preferably formed of the same material. The adhesive layers 51 and 52 are formed of, for example, a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like.

  In the case of a thermoplastic resin or a thermosetting resin, bonding is performed by heat treatment. On the other hand, in the case of an ultraviolet curable resin, bonding is performed by irradiation with ultraviolet light.

  Examples of the thermoplastic resin include ethylene-vinyl acetate copolymer, polyvinyl butyral, plasticized polyvinyl acetal, plasticized polyvinyl chloride, plasticized saturated thermoplastic polyester, thermoplastic polyurethane, and ethylene-ethyl acrylate copolymer.

  Examples of the thermosetting resin include an acrylic thermosetting resin, a thermosetting epoxy resin, a polyurethane curable resin, and the like.

  Examples of the ultraviolet curable resin include an acrylic photocurable resin, a photocurable epoxy resin, and a urethane acrylate photocurable resin.

  The screen sheet 53 displays an image projected from the front or rear projector 12 to the front user 10 and allows the user 10 to visually recognize the back background. The specific structure of the screen sheet 53 will be described later.

  The screen sheet 53 is used between the plurality of transparent plates 30 and 40. The screen sheet 53 need not have flexibility, but preferably has flexibility. It is easy to apply to curved screens. The thickness of the screen sheet 53 can be arbitrarily set according to the manufacturing method of the screen sheet 53, the visibility of the projected image, and the like, and is, for example, 0.02 to 1.5 mm.

  Although the screen sheet 53 of the present embodiment is used sandwiched between the plurality of transparent plates 30 and 40, the screen sheet 53 may be attached to only one of the plurality of transparent plates 30 and 40 and used. The other one of the transparent plates 30 and 40 may not be provided. The screen main body 50 can be supported by one transparent plate.

  The size of the screen sheet 53 in the front-back direction may be the same as the size of the plurality of transparent plates 30 and 40. In this case, as shown in FIG. 2, the end face of the screen sheet 53 and the end faces of the plurality of adhesive layers 51 and 52 form the end face of the screen main body 50.

  The size of the screen sheet 53 may be smaller than the sizes of the plurality of transparent plates 30 and 40 when viewed in the front-back direction. In this case, as shown in FIG. 3, the plurality of adhesive layers 51 and 52 wrap around the end face of the screen sheet 53, and the end face of the screen main body 50 is composed of only the end faces of the plurality of adhesive layers 51 and 52.

  By the way, at the time of projecting an image, the light repeatedly propagates inside the transparent screen 20 while being reflected, thereby generating unnecessary light that does not contribute to the image display.

  Therefore, the light absorbing member 60 is provided on the outer peripheral portion of the transparent screen 20. The light absorbing member 60 absorbs unnecessary light that does not contribute to image display, thereby suppressing a decrease in image contrast due to unnecessary light brightness. Therefore, image visibility of the transparent screen 20 can be improved.

  For example, the light absorbing member 60 may be provided in contact with the end face of the screen main body 50 as shown in FIGS. In this case, the difference between the refractive indices on both sides of the end face is smaller than when the end face of the screen main body 50 is in contact with air. Therefore, the light propagating inside the screen main body 50 at the time of projecting an image is less likely to be reflected inside at the end face of the screen main body 50 and easily emitted to the outside. At least a part of the emitted light propagates inside the light absorbing member 60, is reflected at the interface between the light absorbing member 60 and the air, and is absorbed by the light absorbing member 60 before returning to the screen main body 50. Converted to heat.

  This effect is remarkable when the plurality of transparent plates 30 and 40 sandwich the screen main body 50. In this case, at the time of projecting an image, light propagating inside the screen main body 50 easily propagates far away while repeatedly reflecting at the interface between the screen main body 50 and each of the transparent plates 30 and 40.

  The light absorbing member 60 may be provided in contact with the end surfaces of the transparent plates 30 and 40 as shown in FIGS. In this case, the refractive index difference on both sides of the end face is smaller than when the end faces of the transparent plates 30 and 40 are in contact with air. Therefore, the light propagating inside the transparent plates 30 and 40 at the time of projecting an image is hardly reflected inside at the end faces of the transparent plates 30 and 40 and easily emitted to the outside. At least a part of the emitted light propagates inside the light absorbing member 60, is reflected at the interface between the light absorbing member 60 and the air, and is returned by the light absorbing member 60 before returning to each of the transparent plates 30 and 40. Absorbed and converted to heat.

  2 and 3, the light absorbing member 60 may be provided over the end face of the front transparent plate 30 and the end face of the rear transparent plate 40 to seal the screen main body 50. You may. Deterioration of the screen body 50 due to moisture can be suppressed.

  The light absorbing member 60 of the present embodiment contacts both the end surface of the front transparent plate 30 and the end surface of the rear transparent plate 40, but may contact only one of them.

  As shown in FIGS. 2 and 3, the light absorbing member 60 has an outer peripheral portion of a surface (hereinafter, also referred to as an “outer surface”) of each of the transparent plates 30 and 40 on the side opposite to the screen body 50 side. It may be provided in contact with. In this case, the difference in the refractive index between both sides of the outer peripheral portion is smaller than when the outer peripheral portion of the outer surface of each of the transparent plates 30 and 40 is in contact with air. Therefore, light propagating inside each of the transparent plates 30 and 40 during projection of an image is less likely to be reflected internally at the outer peripheral portion of the outer surface of each of the transparent plates 30 and 40, and is easily emitted to the outside. At least a part of the emitted light propagates inside the light absorbing member 60, is reflected at the interface between the light absorbing member 60 and the air, and is returned by the light absorbing member 60 before returning to each of the transparent plates 30 and 40. Absorbed and converted to heat.

  The light absorbing member 60 of the present embodiment includes an outer peripheral portion of the outer surface (that is, the front surface) of the front transparent plate 30 and an outer peripheral portion of the outer surface (that is, the rear surface) of the rear transparent plate 40. , But may contact only one of them.

  The light absorbing member 60 may be provided on the outer peripheral portion of the front surface of the transparent screen 20, as shown in FIGS. Unnecessary light can be suppressed from being emitted from the outer peripheral portion of the front surface of the transparent screen 20, and the contrast of the image displayed in the remaining central portion can be improved.

  By the way, unnecessary light emitted from the end face of the transparent screen 20 is invisible to the user.

  Therefore, a fine uneven structure is formed on at least one of (A) the end face of the front transparent plate 30, (B) the end face of the rear transparent plate 40, and (C) the end face of the screen main body 50. , A reflection reducing effect may be provided. At these end faces, unnecessary light is hardly reflected inside and easily emitted outside.

  The uneven structure is formed by, for example, a roughening process such as an etching process or a sandblasting process. The uneven structure may be covered with the light absorbing member 60, and unnecessary light emitted from the uneven structure may be absorbed by the light absorbing member 60.

  The concavo-convex structure can also change the direction of light directed toward the inside. Therefore, on the front and rear surfaces of the transparent screen 20, the amount of unnecessary light incident at an incident angle equal to or less than the total reflection angle can be increased, and the amount of unnecessary light reflected back inside can be reduced again.

  The light absorbing member 60 may be formed in a U-shape, and may cover from the outer peripheral portion of the outer surface of the front transparent plate 30 to the outer peripheral portion of the outer surface of the rear transparent plate 40. Good. When the outer peripheral portion of the transparent screen 20 is inserted into the groove of the holding member (not shown) and is held by the holding member, the light absorbing member 60 may serve as a filling member that fills a gap with the wall surface of the groove.

  The light absorbing member 60 includes (1) an end face of the screen main body 50, (2) an end face of at least one transparent plate, (3) an outer peripheral portion of an outer surface of at least one transparent plate, and (4) a transparent screen. It is sufficient if it is provided on one or more of the outer peripheral portions of the front surface of the.

  The light absorbing member 60 may include a material having a larger light absorption coefficient than each material of the screen main body 50 and the material of each of the transparent plates 30 and 40.

  The light absorbing member 60 may include at least one of a pigment and a dye. Pigments and dyes are used in a state of being dispersed or dissolved in a resin. As the pigment, for example, carbon black, graphite, titanium black, ferric oxide, an organic pigment and the like are used. As the dye, for example, an azo dye, an anthraquinone dye, an indigo dye, a phthalocyanine dye and the like are used.

  As a resin for dispersing or dissolving pigments and dyes, urethane resin, acrylic resin, epoxy resin, polyester resin, silicone resin, vinyl chloride resin, butyl rubber resin, polyisobutylene resin, polysulfide resin and the like are used. Further, as the light absorbing member 60, a commercially available one can be used. For example, a trade name Sikaflex 265 (urethane resin, black, manufactured by Sika Japan Co., Ltd.) and the like.

  The color of the light absorbing member may be a dark color such as black.

  As a method of providing the light absorbing member 60 as shown in FIGS. 1 to 3, for example, a method of attaching a light absorbing member formed in a sheet shape, a method of fitting a light absorbing member formed in a U-shaped cross section, a liquid There is a method of applying a light absorbing member.

  FIG. 4 is a cross-sectional view illustrating a structure of a reflective screen sheet according to one embodiment. The reflection type screen sheet 53A shown in FIG. 4 is used in place of the screen sheet 53 shown in FIGS. The reflection type screen sheet 53A displays an image projected from the front projector 12 to the front user 10 and allows the user 10 to visually recognize the back background.

  The screen sheet 53A has, for example, as shown in FIG. 4, from the front side to the rear side, a base material 54A, an uneven layer 55A, a light reflection layer 56A, a coating layer 57A, and a protective layer 58A in this order. In this case, the uneven layer 55A, the light reflecting layer 56A, the covering layer 57A, and the protective layer 58A are formed on the surface of the base 54A in this order.

  The thickness of the base material 54A and the thickness of the protective layer 58A can be arbitrarily selected according to the manufacturing method, and are, for example, 0.01 to 0.5 mm, preferably 0.05 to 0.3 mm. The total of the thickness of the uneven layer 55A, the thickness of the light reflection layer 56A, and the thickness of the coating layer 57A can be arbitrarily selected according to the manufacturing method, and is, for example, 1 to 100 μm.

  Note that the arrangement of the base material 54A and the protective layer 58A may be reversed, and the screen sheet 53A includes a protective layer 58A, a coating layer 57A, a light reflecting layer 56A, a concave-convex layer 55A, and a base material. 54A in this order.

  The substrate 54A may be a glass sheet or a resin sheet, but is preferably a resin sheet from the viewpoint of flexibility. The resin sheet is formed of, for example, polycarbonate, PET, PEN, cycloolefin polymer, or polyester.

  The uneven layer 55A is formed on the surface of the base material 54A, and has unevenness on the surface opposite to the base material 54A. The uneven layer 55A may be formed of a resin. As a method for forming the uneven layer 55A, for example, an imprint method or the like is used. Any of a photocurable resin, a thermoplastic resin, and a thermosetting resin may be used as a resin material for the imprint method.

  The uneven structure of the uneven layer 55A may be a microarray, a hologram, or the like in addition to the structure shown in FIG.

  The light reflection layer 56A is formed in a zigzag shape along the unevenness on the surface of the uneven layer 55A. The light reflection layer 56A reflects a part of light from the front to the front and transmits a part of light from the rear to the front. The light reflection layer 56A may be formed of, for example, a metal such as aluminum or silver, a metal oxide, or a metal nitride. As a method for forming the light reflection layer 56A, for example, a vacuum evaporation method or a sputtering method is used.

  The coating layer 57A fills the unevenness of the light reflection layer 56A. The coating layer 57A may be formed of a resin, and is preferably formed of the same resin as the uneven layer 55A.

  The protective layer 58A is a sheet that protects the covering layer 57A. The protective layer 58A may be either a transparent glass sheet or a transparent resin sheet, but is preferably a transparent resin sheet from the viewpoint of flexibility. The resin sheet is formed of, for example, polycarbonate, PET, PEN, cycloolefin polymer, or polyester.

  The uneven layer 55A of the present embodiment is formed on the surface of the base material 54A, but may be formed on one of the surfaces of the transparent plates 30 and 40 instead. Further, the coating layer 57A of the present embodiment is protected by the protective layer 58A, but may be protected by one of the transparent plates 30 and 40 instead. In these cases, the plurality of adhesive layers 51 and 52, the base material 54A, and the protective layer 58A are unnecessary.

  FIG. 5 is a cross-sectional view illustrating a structure of a transmission type screen sheet according to an embodiment. The transmission type screen sheet 53B shown in FIG. 5 is used in place of the screen sheet 53 shown in FIGS. The transmissive screen sheet 53B displays an image projected from the rear projector 12 to the front user 10 and allows the user 10 to visually recognize the rear background.

  As shown in FIG. 5, for example, the transmission type screen sheet 53B has a light scattering layer 55B and a base material 54B in this order from the front side to the rear side. The thickness of the base material 54B can be arbitrarily selected according to the method of manufacturing the base material 54B, and is, for example, 0.01 to 0.5 mm, and preferably 0.05 to 0.3 mm. The thickness of the light scattering layer 55B can be arbitrarily selected according to the method of manufacturing the light scattering layer 55B, and is, for example, 1 to 200 μm.

  The arrangement of the base material 54B and the light scattering layer 55B may be reversed, and the screen sheet 53B may have the base material 54B and the light scattering layer 55B in this order from the front side to the rear side.

  The substrate 54B may be a glass sheet or a resin sheet, but is preferably a resin sheet from the viewpoint of flexibility. The resin sheet is formed of, for example, polycarbonate, PET, PEN, or a cycloolefin polymer.

  The light scattering layer 55B includes a transparent material and a light scattering material having a different refractive index from the transparent material. As the transparent material, for example, a transparent resin is used. Examples of the transparent resin include a photocurable resin such as an acrylic resin and an epoxy resin, a thermosetting resin, and a thermoplastic resin. On the other hand, as the light scattering material, fine particles of an inorganic material, fine particles of an organic material, voids, and the like are used. Examples of the inorganic material include high refractive index materials such as titanium oxide (refractive index: 2.5 to 2.7), zirconium oxide (refractive index: 2.4), and aluminum oxide (refractive index: 1.76), and porous materials. Low refractive index materials such as silica (refractive index: 1.25 or less) and hollow silica (refractive index: 1.25 or less) are used. The light scattering material may be dispersed in the transparent material. The proportion of the light scattering material in the light scattering layer 55B is, for example, 0.01% by volume or more and 5% by volume or less, preferably 0.05% by volume or more and 1% by volume or less.

  The light scattering layer 55B may further include a light absorbing material. As the light absorbing material, carbon black, titanium black, or the like can be used. The proportion of the light-absorbing material in the light-scattering layer 55B is, for example, 0.01% by volume to 5% by volume, preferably 0.1% by volume to 3% by volume. The light absorbing material suppresses light propagation due to repeated light reflection inside the transparent screen. Thereby, blurring of an image can be suppressed.

  As shown in FIG. 6, the light scattering layer 55B may be a layer in which a plurality of light scattering portions 57B are arranged at intervals in a transparent resin portion 56B. This arrangement is called a louver structure. The light scattering portion 57B includes a light scattering material and a transparent material. As the transparent resin portion 56B, the same material as the transparent material used for the light scattering layer 55B shown in FIG. 5 can be used.

  Note that the light scattering layer 55B of the present embodiment is formed on the surface of the base material 54B, but may be formed on one of the surfaces of the transparent plates 30 and 40 instead. Further, the light scattering layer 55B of the present embodiment is covered with the adhesive layer, but may be covered with one of the plurality of transparent plates 30 and 40. In these cases, the plurality of adhesive layers 51 and 52 and the base material 54B are unnecessary.

  Although the embodiments of the transparent screen and the like have been described above, the present invention is not limited to the above embodiments and the like, and various modifications and improvements are possible within the scope of the present invention described in the claims. is there.

  For example, the transparent screen may have a functional layer not shown in FIGS. Examples of the functional layer include an anti-reflection layer that reduces light reflection, a light attenuation layer that attenuates a part of light, and an infrared shielding layer that suppresses transmission of infrared light. The number of functional layers and the positions of the functional layers are not particularly limited.

  Regarding the optical characteristics of the reflection type transparent screen, it is preferable that the transmittance is 5% or more and 90% or less, the reflectance is 5% or more and 70% or less, and the front haze is 20% or less. The transmittance, the reflectance, and the front haze are measured using a D65 light source specified in JIS Z8720 (2012) “Standard illuminant (standard light) and standard light source for color measurement”, respectively. The rear haze means the degree of haze (%) in the reflection of light incident on the transparent screen, and the total reflectance (%) measured using the D65 light source is the diffuse reflectance (%) measured using the D65 light source. It is shown by the ratio (%) divided by.

  The optical characteristics of the transmission type transparent screen are such that the transmittance is 5% or more and 90% or less, the front haze is 4% or more and 40% or less, and the rear haze is 0% or more and 60% or less. preferable. The transmittance, the front haze, and the rear haze are each measured using a D65 light source defined in JIS Z8720 (2012) “Standard illuminant (standard light) and standard light source for color measurement”.

10 User 20 Transparent screen 30 Transparent plate 40 Transparent plate 50 Screen body 51 Adhesive layer 52 Adhesive layer 53 Screen sheet 53A Reflective screen sheet 54A Base material 55A Uneven layer 56A Light reflecting layer 57A Coating layer 58A Protective layer 53B Transmissive screen Sheet 54B Base material 55B Light scattering layer 60 Light absorbing member

Claims (10)

A screen body that displays an image projected from the front or the back to the user in front, and allows the user to see the background behind, and a transparent screen having a transparent plate supporting the screen body,
An uneven structure is formed on at least one of an end face of the screen main body and an end face of the transparent plate,
A transparent screen, wherein a light absorbing member that absorbs at least a part of light that propagates inside the transparent screen when projecting an image is provided on an outer peripheral portion of the transparent screen.   The transparent screen according to claim 1, wherein the light absorbing member is provided in contact with an end surface of the screen main body.   The transparent screen according to claim 1, wherein the light absorbing member is provided in contact with an end surface of the transparent plate.   The transparent screen according to any one of claims 1 to 3, wherein the light absorbing member is provided on an outer peripheral portion of a surface of the transparent plate opposite to the screen body.   The transparent screen according to claim 1, wherein the light absorbing member is provided on an outer peripheral portion of a front surface of the transparent screen.   The transparent screen according to claim 1, wherein the light absorbing member includes at least one of a pigment and a dye.   The transparent screen according to claim 1, wherein the transparent plate is provided on both sides of the screen main body.   The transparent screen according to claim 1, wherein the transparent plate is a glass plate. The screen body is
Displaying the image projected from the front to the user in front,
An uneven layer having unevenness on the surface,
A light reflecting layer formed along the irregularities on the surface of the irregular layer, reflecting part of light from the front, and transmitting part of light from the rear to the front,
The transparent screen according to any one of claims 1 to 8, further comprising: a coating layer that covers irregularities of the light reflection layer. The screen body is
Displaying the image projected from behind to the user in front,
The transparent screen according to any one of claims 1 to 8, further comprising a light scattering layer including a transparent material and a light scattering material having a different refractive index from the transparent material.

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