JP2005037514A - Front plate and transmissive screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front plate and a transmissive screen which do not cause the loss of a light quantity, is easily manufactured, and has the improved uniformity of the luminance of a screen whichever position it is observed from. <P>SOLUTION: The front plate is equipped with a lens layer 31 where a plurality of unit lenses to emit a part of an incident light beam from an emitting part after totally reflecting it by total reflection parts (31a and 31b) are arranged side by side so that their longitudinal directions are nearly horizontal, and an external light absorption layer 32 which is provided at least on the total reflection parts (31a and 31b) and absorbs and/or attenuates external light from an emitting side. At least at the lower part than the center of the front plate 30, angles (β1 to β4) formed by the main optical path of the incident light beam and the downside total reflection surfaces 31b of the unit lenses are made larger than angles (α1 to α4) formed by the main optical axis and the upside total reflection surfaces 31a of the unit lenses. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a front plate and a transmissive screen used in a single light source such as liquid crystal or DLP (Digital Light Processor) and a multi-tube projection television in a horizontal arrangement such as a CRT.
[0002]
[Prior art]
Various proposals have been made on the transmissive screen and its front plate so that the influence of external light can be suppressed and an image with high contrast can be observed. For example, in Patent Documents 1 to 3, a louver-like light absorption wall array is arranged to improve contrast.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-167167 [Patent Document 2]
JP 2000-137294 A [Patent Document 3]
Japanese Patent Laid-Open No. 2002-207253
[Problems to be solved by the invention]
However, the louver-shaped light absorption wall row described in the above-mentioned patent document has a problem that it is difficult to manufacture.
In addition, there is a problem in that the light absorption wall array causes a loss of light amount and the light from the light source cannot be used effectively.
[0005]
An object of the present invention is to provide a front plate and a transmissive screen that do not cause a light loss, are easy to manufacture, and improve the uniformity of screen brightness even when viewed from any position.
[0006]
[Means for Solving the Problems]
The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
[0007]
The invention according to claim 1 is a front plate in which a plurality of unit lenses each having a substantially trapezoidal cross-sectional shape are arranged side by side so that the longitudinal direction is substantially horizontal, at least from the center of the front plate. The angle (β1 to β4) formed between the lower surface (31b) of the unit lens and the perpendicular to the plate surface of the front plate is the upper surface (31a) of the unit lens and the plate surface of the front plate. It is a front board (30) characterized by being larger than the angle ((alpha) 1- (alpha) 4) which the perpendicular | vertical with respect to.
[0008]
In the second aspect of the present invention, a plurality of unit lenses are arranged so that the longitudinal direction is substantially horizontal after a part of incident light rays are totally reflected by the total reflection portions (31a, 31b) and then emitted from the emission portion. Front plate of a transmissive screen provided with a lens layer (31) and an external light absorption layer (32) that is provided at least on the output side of the total reflection part and absorbs and / or attenuates external light from the output side The angle (β1 to β4) formed by the optical axis of the principal ray incident on each position and the lower total reflection surface (31b) of the unit lens at least below the center of the front plate is the light. It is a front plate (30) characterized by being larger than the angle ((alpha) 1- (alpha) 4) which an axis | shaft and the upper total reflection surface (31a) of the said unit lens make.
[0009]
According to a third aspect of the present invention, in the front plate according to the first aspect, the upper total reflection surface (31a) does not hit the optical axis of the principal ray reflected by the lower total reflection surface (31b). The front plate (30) is characterized in that it is disposed on the surface.
[0010]
The invention of claim 4 is the front plate according to claim 1 or 2, wherein the angle of the upper total reflection surface (31a) and / or the lower total reflection surface (31b) is the vertical direction of the front plate. The front plate (30) is characterized in that it differs depending on the position of the front plate.
[0011]
According to a fifth aspect of the present invention, in the front plate according to any one of the first to third aspects, the optical axis of the incident principal ray, the upper total reflection surface (31a) and the lower side of the unit lens The angle formed by the total reflection surface 31b) is a front plate (30) characterized in that both are less than 10 degrees.
[0012]
According to a sixth aspect of the present invention, in the front plate according to any one of the first to fourth aspects, the external light absorbing layer (32) is made of a material having a lower refractive index than the lens layer (31). It is the front plate (30) characterized by being formed.
[0013]
The invention of claim 7 is the front plate according to any one of claims 1 to 5, wherein the external light absorption layer (32) has a particle size of 1 μm or more and an external light absorption layer. The front plate (30) is characterized in that light-absorbing fine particles having a width of less than 5 are dispersed.
[0014]
The invention of claim 8 is characterized in that, in the front plate according to any one of claims 1 to 6, at least a part has a diffusing portion for diffusing the light beam in the vertical direction. It is a front plate.
[0015]
A ninth aspect of the present invention is the front plate according to the seventh aspect, wherein the diffusing portion is formed by mixing a diffusing agent.
[0016]
The invention of claim 10 is the front plate (30) according to any one of claims 1 to 8, the diffusion sheet (20) provided on the light source side of the front plate, and the diffusion. And a Fresnel lens sheet (10) provided further on the light source side than the sheet.
[0017]
According to an eleventh aspect of the present invention, in the transmissive screen according to the ninth aspect, the diffusion sheet (20) and / or the Fresnel lens sheet (10) is an optical axis of a principal ray incident on the front plate (30). A transmissive screen characterized by having an optical axis deflecting unit that deflects the screen downward.
[0018]
According to a twelfth aspect of the present invention, in the transmissive screen according to the ninth or tenth aspect, the diffusion sheet (20) is a double-sided lenticular lens sheet having a light absorbing layer in a non-light-collecting portion of the lenticular lens. A transmissive screen characterized by the above.
[0019]
According to a thirteenth aspect of the present invention, in the transmissive screen according to the ninth or tenth aspect, the diffusion sheet (20) causes a part of incident light rays to be totally reflected by the total reflection portion, and then from the emission portion. A lens layer in which a plurality of unit lenses to be emitted are arranged side by side so that the longitudinal direction is substantially vertical, and external light absorption that is provided at least on the emission side of the total reflection portion and absorbs and / or attenuates external light from the emission side A transmissive screen characterized by being a lens sheet provided with a layer.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a perspective view showing an embodiment of a transmission screen according to the present invention.
The transmissive screen 1 in the present embodiment is a screen used for a single light source such as liquid crystal or DLP, and a horizontal tube-type projection television such as a CRT, and includes a Fresnel lens sheet 10, a diffusion sheet 20, and a front plate 30. Overlaid.
[0021]
The Fresnel lens sheet 10 is a lens sheet in which a Fresnel lens shape is formed on the exit surface, and image light from an image light source (not shown) is substantially parallel (incident at a substantially right angle to the diffusion sheet 20). Let it emit.
[0022]
The diffusion sheet 20 includes an incident side lenticular lens portion 21, an emission side lenticular lens portion 22, and a black stripe (hereinafter, BS) layer 23. The exit-side lenticular lens unit 22 is provided in the vicinity of the focal point of the entrance-side lenticular lens unit 21, and the BS layer 23 is a non-emission unit through which light collected by the entrance-side lenticular lens unit 21 does not pass. The side lenticular lens unit 22 is provided so as to be sandwiched between unit lenticular lens shapes. The diffusion sheet 20 in the present embodiment has unit lenticular lens shapes extending in the vertical direction arranged in the left-right (horizontal) direction, so that the light is diffused in the left-right direction and hardly affects the vertical direction. In the case of a single light source, the emission side lenticular lens portion 22 is not necessary.
[0023]
FIG. 2 is a cross-sectional view showing the front plate 30 cut in the vertical direction. In FIG. 2, the front plate 30 is shown divided into four locations from above to below.
The front plate 30 includes a lens layer 31 having a unit lens having a substantially trapezoidal cross section shown in FIG. 2, and an external light absorbing layer 32 formed between the unit lenses.
A plurality of lens layers 31 are arranged side by side so that the longitudinal direction of the unit lenses is substantially horizontal. This unit lens is provided with an upper total reflection surface 31a, a lower total reflection surface 31b, and an emitting portion 31c.
In order to prevent moire between the unit lens of the lens layer 31 and the Fresnel lens sheet 10 and / or the pixel, the pitch of the unit lens is determined based on a known method.
[0024]
In FIG. 2, angles formed by the optical axis of the principal ray incident on this cross section and the upper total reflection surface 31a (hereinafter referred to as the upper total reflection surface angle) α1 to α4, the optical axis of the incident principal ray and the lower side. Angles (hereinafter referred to as lower total reflection surface angles) β1 to β4 formed with the side total reflection surface 31b are shown.
The upper total reflection surface angles α1 to α4 are larger toward the upper part of the screen, and the angle gradually changes so as to be substantially zero at the lowermost part of the screen (α1>α2>α3> α4≈0).
[0025]
On the other hand, the lower total reflection surface angles β1 to β4 gradually change so as to increase toward the lower part of the screen (β1 <β2 <β3 <β4).
The relationship between the upper total reflection surface angles α1 to α4 and the lower total reflection surface angles β1 to β4 is β1 ≧ α1, β2> α2, β3> α3, β4> α4.
[0026]
In the present embodiment, the image light that has passed through the Fresnel lens sheet 10 and the diffusion sheet 20 enters the front plate 30 at a substantially right angle in the vertical direction. Accordingly, the upper total reflection surface angles α1 to α4 and the lower total reflection surface angles β1 to β4 are respectively the optical axis of the principal ray of the image light incident on the front plate 30, the upper total reflection surface 31a, and the lower total reflection surface. It is substantially equal to the angle (in the cross section shown in FIG. 2) formed with the surface 31b. Therefore, the angle formed between the optical axis of the principal ray of the incident video light and the lower total reflection surface 31b is larger than the angle formed between the optical axis of the principal ray and the upper total reflection surface 31a.
[0027]
Note that, depending on the form of the Fresnel lens sheet and the diffusion sheet, the image light that has passed through them does not necessarily enter the front plate 30 at a substantially right angle in the vertical direction. For example, the light may be condensed or diffused by a Fresnel lens sheet. In such a case, the upper total reflection surface angle and the lower total reflection surface angle on the front plate may be appropriately changed so that a good image can be obtained at the main observation position. In that case, the magnitude relationship between the upper total reflection surface angle and the lower total reflection surface angle may deviate from the above-described relationship, but at least the optical axis and unit of the principal ray of the image ray incident on the front plate If the angle formed by the lower total reflection surface of the lens is larger than the angle formed by the optical axis of the principal ray and the upper total reflection surface of the unit lens, the effect of the present invention can be obtained and good Can be obtained.
[0028]
FIG. 3 is a diagram for explaining the operation of the front plate 30 in the present embodiment. The right side of FIG. 3 shows the optical path of the optical axis of the principal ray, and the left side of FIG. 3 shows the distribution of the image light emitted for each region.
As described above, the angle formed between the optical axis of the principal ray of the incident video light and the lower total reflection surface 31b is larger than the angle formed between the optical axis of the principal ray and the upper total reflection surface 31a. Therefore, of the image light incident on the front plate 30 of the present embodiment, the component reflected by the lower total reflection surface 31b is largely deflected upward.
On the other hand, the component of the image light reflected by the upper total reflection surface 31a is deflected downward, but the angle is smaller than the component reflected by the lower total reflection surface 31b. Further, components that are not reflected by the upper total reflection surface 31a and the lower total reflection surface 31b are emitted almost as they are.
[0029]
For example, when light incident on the front plate 30 at a right angle and hits the lower total reflection surface 31b of the lower total reflection surface angle β = 5 degrees is assumed that the refractive index of the lens layer 31 is 1.5. Since it is reflected by the lower total reflection surface 31b and is refracted when it is emitted from the emission part 31c, it is emitted toward arcsin (1.5 * sin (5 * 2)) = 15 degrees.
Accordingly, when viewed as a whole, the image light incident on the front plate 30 has more components emitted upward than when incident.
[0030]
FIG. 4 is a diagram illustrating a state in which a projection television using the transmission screen according to the present embodiment is viewed.
As shown in FIG. 4, the image light emitted from the projection television gives directivity upward at the lower end, approaches the horizontal as it goes up, and directs slightly downward at the upper end, as shown in FIG. If it is provided, the entire screen looks bright and uniform when viewed from any position (standing position, sitting position).
[0031]
Here, the angle formed by the optical axis of the principal ray of the incident image light and the upper total reflection surface 31a and the lower total reflection surface 31b of the unit lens is preferably less than 10 degrees. When this angle is 10 degrees or more, the upward component increases too much, and it becomes dark when observed from the front. More preferably, about 0 to 5 degrees is good.
[0032]
The external light absorption layer 32 is provided between the unit lenses of the lens layer 31 and is formed of a material having a refractive index lower than that of the lens layer 31. Accordingly, when light exceeding the critical angle is incident on the boundary portion between the lens layer 31 and the external light absorption layer 32, total reflection is performed. Therefore, the image light is reflected by the upper total reflection surface 31a and the lower total reflection surface 31b. Can be totally reflected and emitted without loss of image light.
Further, in the external light absorption layer 32, light absorption fine particles having a particle diameter of 1 μm or more and less than the width of the external light absorption layer 32 are dispersed, and external light coming from the observer side is effectively absorbed and attenuated. can do. Therefore, the contrast of the observed image light can be improved.
[0033]
On the other hand, in the rear projection type screen as in this embodiment, the image light transmitted through the Fresnel lens sheet 10 is stray light due to internal reflection of several percent of light at each interface on the lens surface. This stray light causes image defects such as a color cone (mainly generated at the center of the screen) and a rainbow (mainly generated at the lower part of the screen). These image defects were more likely to appear when viewed from above or below the screen than when viewed from the front of the screen.
[0034]
However, in the present embodiment, stray light having a large directivity in the vertical direction, such as a color cone or a rainbow, is incident on the upper total reflection surface 31a and the lower total reflection surface 31b at a large angle. Therefore, the stray light that has reached the upper total reflection surface 31a and the lower total reflection surface 31b passes through the upper total reflection surface 31a and the lower total reflection surface 31b without being totally reflected, and enters the external light absorption layer 32. Reaching, absorbed and attenuated. Therefore, in the present embodiment, image troubles such as color cones and rainbows can be solved.
[0035]
Further, the front plate 30 in the present embodiment can be manufactured by a method similar to a conventionally used transmission screen manufacturing method, so that it can be manufactured easily and inexpensively.
[0036]
(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
(1) For example, in the present embodiment, the example in which the cross-sectional shape of the unit lens of the lens layer 31 is a substantially trapezoidal shape has been shown, but the present invention is not limited to this, and for example, two total reflections provided in the unit lens When the two- or three-way diffusion between the total reflection light by the surface and the light that is directly emitted without being reflected by these total reflection surfaces appears excessively, and the luminance change (brightness unevenness) in the vertical direction occurs. The sectional shape of the unit lens may be a polygon such as a hexagon or an octagon (see the lens layer 231 in FIG. 5A), or the total reflection surface may be a curved surface such as an arc or a part of an ellipse [FIG. The lens layer 331 of b)] may be combined, or unit lesbians having different shapes may be combined [see the lens layers 431, 531 of FIG. 5C] to smooth the luminance change.
[0037]
(2) Additional elements (lens, diffusing material, etc.) that have a diffusion effect in the vertical direction are added to provide smooth diffusion in the vertical direction and to reduce moire and scintillation. May be.
[0038]
(3) In the present embodiment, the example in which the image light is incident on the front plate 30 at a substantially right angle in the longitudinal section [see FIG. 6A] is not limited thereto, but, for example, a Fresnel lens sheet The image light directed from the diffusion sheet 20 to the front plate 30 may be directed downward by shifting the 10 Fresnel center downward or adding a prism, a linear Fresnel lens sheet, or the like [see FIG. ]. By doing so, the angle formed between the optical axis of the principal ray of the incident video light and the lower total reflection surface is not dependent on the shape of the total reflection surface, and the optical axis of the principal ray and the upper total reflection surface are Can be made larger than the angle formed by. Therefore, even if it is difficult to manufacture a mold necessary for manufacturing the front plate 30 shown in the present embodiment due to the problem of workability of a sharp pointed portion, the same effects as in the present embodiment are obtained. be able to.
[0039]
Further, by directing the image light directed from the diffusion sheet 20 toward the front plate 30 downward, the ratio of the image light hitting the upper total reflection surface can be decreased and the ratio of hitting the lower total reflection surface can be increased. When used in combination with the front plate 30 shown in the embodiment, a higher optical axis correction effect can be expected.
[0040]
When the number of light rays that directly exit downward without hitting the total reflection surface increases, the height relative to the width of the emission portion 31c (the length of the total reflection surface: in FIG. 6, the length in the left-right direction) Just increase). However, if the light reflected by the most incident side of the lower total reflection surface hits again on the surface near the emission side of the upper total reflection surface, it will be emitted downward, so it is necessary to prevent this from happening. It is.
[0041]
(4) In the present embodiment, the example in which the emission part 31c and the external light absorption layer 32 of the front plate 30 are formed on the outermost surface is shown, but not limited to this, for example, a clear layer is laminated on these or Even if it is coated, a rigid plastic sheet may be laminated, and its surface is further treated with antireflection, non-glare treatment, scratch prevention (hard coat treatment), antistatic treatment, diffusion treatment, contamination prevention treatment, etc. May be performed.
[0042]
(5) In the present embodiment, the diffusion sheet 20 is an example of a double-sided lenticular lens sheet having the BS layer 23. However, the present invention is not limited to this. For example, a part of incident light is totally reflected by the total reflection portion. After reflecting, a lens layer in which a plurality of unit lenses to be emitted from the emission part are arranged side by side so that the longitudinal direction is substantially vertical, and provided on at least the total reflection part to absorb and / or absorb external light from the emission side. A lens sheet provided with an external light absorbing layer that attenuates may be provided as a diffusion sheet.
[0043]
(6) In the present embodiment, the diffusion plate 20 and the front plate 30 have been described by taking the form of separate lens sheets as an example. However, the present invention is not limited to this, and for example, the diffusion plate and the front plate are integrated. It may be joined.
[0044]
(7) In the present embodiment, the upper total reflection surface angles α1 to α4 are larger toward the upper part of the screen, and the lower total reflection surface angles β1 to β4 are larger toward the lower part of the screen. For example, the above-described relationship may be provided at least below the center of the screen.
[0045]
(8) In the present embodiment, the Fresnel lens sheet 10 shows an example in which the Fresnel lens surface is formed on the exit surface side. However, the present invention is not limited to this. For example, when the incident angle of the image light is large, A total reflection Fresnel lens sheet having a total reflection arc-shaped prism described in Japanese Patent Application Laid-Open No. 2000-180967 may be used. In this case, the total reflection arc-shaped prism is on the incident side.
[0046]
【The invention's effect】
As described above in detail, according to the present invention, the following effects can be obtained.
(1) At least below the center of the front plate, the angle formed by the optical axis of the principal ray incident on each position and the lower total reflection surface of the unit lens is determined by the optical axis and the upper total reflection surface of the unit lens. Because it is larger than the angle formed, it is possible to control the optical axis in the vertical direction, improving the uniformity of screen brightness even when observed from the front (center) of the screen, which is frequently observed, and from above the center of the screen To do.
[0047]
(2) Since the upper total reflection surface is arranged so that the optical axis of the principal ray reflected by the lower total reflection surface does not hit, it is possible to reliably emit the necessary light without blocking it.
[0048]
(3) Since the angle of the upper total reflection surface and / or the lower total reflection surface varies depending on the vertical position of the front plate, optimum optical characteristics can be obtained for each position. Even when observed, a uniform image can be obtained.
[0049]
(4) Since the angle formed between the optical axis of the incident principal ray and the upper total reflection surface and the lower total reflection surface of the unit lens is less than 10 degrees, the total reflection can be ensured. Can be used without waste.
[0050]
(5) Since the external light absorption layer is formed of a material having a refractive index lower than that of the lens layer, the total reflection surface can be easily formed.
[0051]
(6) Since the light absorption fine particles having a particle diameter of 1 μm or more and less than the width of the external light absorption layer are dispersed in the external light absorption layer, the external light is absorbed and attenuated while forming the total reflection surface. Can give an effect.
[0052]
(7) Since the diffusion unit that diffuses the light beam at least in the vertical direction is provided, the luminance change can be smoothed, and moire and scintillation can be reduced.
[0053]
(8) Since the diffusing part is formed by mixing a diffusing agent, the diffusing part can be formed easily and inexpensively.
[0054]
(9) Since a diffusion sheet provided on the light source side with respect to the front plate and a Fresnel lens sheet provided on the light source side with respect to the diffusion sheet are provided, the front plate is added to the conventionally used transmission type screen. The effect of this invention can be acquired only by doing.
[0055]
(10) Since the diffusion sheet and / or the Fresnel lens sheet has a function of deflecting the optical axis of the principal ray incident on the front plate downward, the manufacture of the mold necessary for the production of the front plate has a sharp angle. Even if it is difficult due to the problem of workability of the part, the effect of the present invention can be obtained.
[0056]
(11) Since the diffusion sheet is a double-sided lenticular lens sheet having a light absorbing layer in the non-condensing part of the lenticular lens, the brightness of the screen is always uniform even if the observation position moves in any direction, up, down, left, or right It can be.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a transmission screen according to the present invention.
FIG. 2 is a cross-sectional view showing a front plate 30 cut in the vertical direction.
FIG. 3 is a diagram illustrating the operation of a front plate 30 in the present embodiment.
FIG. 4 is a diagram showing a state in which a projection television using a transmission screen according to the present embodiment is viewed.
FIG. 5 is a diagram showing a modification of a lens layer shape.
FIG. 6 is a diagram showing a modification in which image light is incident on the front plate facing downward.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transmission type screen 10 Fresnel lens sheet 20 Diffusion sheet 21 Incident side lenticular lens part 22 Outgoing side lenticular lens part 23 Black stripe (BS) layer 30 Front plate 31 Lens layer 31a Upper total reflection surface 31b Lower total reflection surface 31c Output part 32 Outside light absorption layer

Claims (13)

A cross-sectional shape in a substantially vertical direction is a front plate in which a plurality of unit lenses having a substantially trapezoidal shape are arranged side by side so that the longitudinal direction is substantially horizontal,
At least below the center of the front plate, the angle between the lower surface of the unit lens and the perpendicular to the plate surface of the front plate is the angle between the upper surface of the unit lens and the normal to the plate surface of the front plate. A front plate characterized by being larger than an angle. A lens layer in which a part of incident light rays are totally reflected by the total reflection portion, and then a plurality of unit lenses that are emitted from the emission portion are arranged side by side so that the longitudinal direction is substantially horizontal, and
An external light absorbing layer that is provided at least on the output side of the total reflection portion and absorbs and / or attenuates external light from the output side;
A transmissive screen front plate comprising:
At least below the center of the front plate, the angle formed by the optical axis of the principal ray incident at each position and the lower total reflection surface of the unit lens is determined by the optical axis and the upper total reflection surface of the unit lens. A front plate characterized by being larger than an angle formed. The front plate according to claim 2,
The front plate, wherein the upper total reflection surface is arranged so that an optical axis of the principal ray reflected by the lower total reflection surface does not hit. In the front plate according to claim 2 or claim 3,
An angle of the upper total reflection surface and / or the lower total reflection surface is different depending on the position of the front plate in the vertical direction. In the front plate according to any one of claims 3 to 4,
An angle formed by the optical axis of the incident principal ray and the upper total reflection surface and the lower total reflection surface of the unit lens is less than 10 degrees. In the front plate according to any one of claims 1 to 5,
The front plate, wherein the external light absorption layer is formed of a material having a refractive index lower than that of the lens layer. In the front plate according to any one of claims 1 to 6,
A front plate, wherein the external light absorption layer is dispersed with light absorption fine particles having a particle diameter of 1 μm or more and less than the width of the external light absorption layer. The front plate according to any one of claims 1 to 7,
At least a part of the front plate has a diffusing portion for diffusing the light beam in the vertical direction. The front plate according to claim 8,
The diffusion part is formed by mixing a diffusing agent,
A front plate characterized by The front plate according to any one of claims 1 to 9,
A diffusion sheet provided on the light source side of the front plate;
And a Fresnel lens sheet provided further on the light source side than the diffusion sheet. The transmission screen according to claim 10, wherein
The transmissive screen, wherein the diffusion sheet and / or the Fresnel lens sheet includes an optical axis deflecting unit that deflects an optical axis of a principal ray incident on the front plate downward. The transmissive screen according to claim 10 or 11,
The transmissive screen is characterized in that the diffusion sheet is a double-sided lenticular lens sheet having a light absorption layer in a non-light condensing part of the lenticular lens. The transmissive screen according to claim 10 or 11,
The diffuser sheet is a lens layer in which a plurality of unit lenses are arranged so that the longitudinal direction is substantially vertical after a part of incident light rays are totally reflected by the total reflection portion, and the longitudinal direction is substantially vertical, and
A transmissive screen, comprising: a lens sheet provided with at least an external light absorption layer that is provided on the output side of the total reflection portion and absorbs and / or attenuates external light from the output side.

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