JP2000180968A - Transmission type projection screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the change of chromaticity from a front viewing to gallery viewing on an observation side to be small while decreasing scintillation by forming fine rugged shape on the surface of a Fresnel lens sheet on a video light entering side. SOLUTION: This screen is equipped with the Fresnel lens sheet 11 where the matted rugged shape 11a is formed on the surface of the light entering side and a circular type Fresnel lens 11b is formed on a light emitting side, and a lenticular lens sheet 12 which is arranged nearer to an observation side and where a lenticular lens for horizontal diffusion is formed on the light entering side and a black stripe is formed on the light emitting side. The matted rugged shape 11a is irregular rugged shape and is continuously arranged on the surface of the sheet 11 on the video light entering side. The rugged shape is formed by forming a matted surface having the fine ruggedness on the surface of a cylindrical roll metallic mold used for the sheeting of an acrylic plate for producing a Fresnel lens and transferring it in the case of the extrusion molding of the acrylic plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LCD (Liquid Crystal Display) or a DMD (Digital Micro-mirror).
The present invention relates to a transmission type projection screen suitable for projecting and observing an image from an image light source having a cell structure such as an image display device (or Mirror Device).

[0002]

2. Description of the Related Art Conventionally, a rear projection type television using three CRTs of red, green and blue as an image light source and a transmission type projection screen as a screen has been known. Generally, a projection screen is composed of a Fresnel lens sheet and a lenticular lens sheet, and is a screen for forming an image with image light from a projector on the screen and obtaining a directional diffusion surface. . As shown in FIG. 6, the projection screen 40 includes a Fresnel lens sheet 41 having a circular Fresnel lens 11b formed on the light exit side,
The Fresnel lens sheet 41 further includes a lenticular lens 12 having a lenticular lens for horizontal diffusion formed on the light entrance side and a black stripe formed on the light exit side, which is arranged on the observation side. The Fresnel lens has a function of forming grooves having a predetermined angle in the acrylic material at a predetermined pitch, and condensing the light diffused radially from the image light to the front. The lenticular lens is a lens mainly for obtaining diffused light having directivity in the horizontal direction, and a cylindrical lens-shaped lens is regularly formed on one plane in the vertical direction, and the light distribution characteristic is improved. It has the function of expanding horizontally.

[0003] A Fresnel lens sheet is formed by applying a predetermined amount of a liquid ultraviolet curable resin on a mold using a mold for a Fresnel lens, placing an acrylic plate on the mold, and pressing with a roll. Then, after irradiating ultraviolet rays from a metal halide lamp of an ultraviolet light source device, the Fresnel lens sheet on which the lens element is formed is peeled off from the Fresnel lens mold to obtain the sheet. The lenticular lens sheet is obtained by molding a thermoplastic resin by using an extruder using a cylindrical roll die having a predetermined shape cut.

[0004] These projection screens
When the image light source is LCD or DMD, light diffusing fine particles are added inside the Fresnel lens sheet to reduce scintillation, but there is a difference in refractive index between the base material of the screen and the light diffusing fine particles. The wavelength dependence of the refractive index difference between the material and the material causes a large chromaticity difference between the chromaticity of the image light in the optical axis direction and the chromaticity at the same time as standing, and at the same time, the particle size of the light diffusing fine particles is from several microns. When the wavelength is several tens of microns, since the light scattering efficiency for each wavelength differs depending on the particle size (Mie's scattering theory), a chromaticity difference occurs between the chromaticity of light in the optical axis direction and the chromaticity at the time of standing. Is generally known. However, hitherto, as one of the performances of the projection screen, it has been essential to add light diffusing fine particles having a refractive index difference from the screen base material into the Fresnel lens sheet so as to reduce scintillation.

[0005]

However, the aforementioned LC
Projection televisions using D or DMD require a glare of the image, called scintillation, and a chromaticity difference between the chromaticity of the image light in the optical axis direction and the chromaticity at the standing angle. When viewing images on the screen, there is a problem that the image screen is difficult to see, and this is an indispensable issue for improving the performance of rear projection type projection TVs. Attempts have been made to change the refractive index and particle size, but at present, the scintillation reduction of the image light is sufficient,
In addition, it is difficult to obtain a Fresnel lens sheet having no chromaticity in the optical axis direction and having a small chromaticity change from the chromaticity of the light in the optical axis direction to standing up. In addition, recently, the method of adding light diffusing fine particles having a refractive index difference from the screen base material to the inside of the Fresnel lens sheet has been changed, and the shape of the image light incident side surface of the Fresnel lens sheet is not flat, but has irregularities. However, a satisfactory improvement effect on the above problem has not been obtained so far.

Under such circumstances, there is a difference in the refractive index in the screen base material by contriving the unevenness on the light incident surface of the Fresnel lens sheet or adding a lens element having a substantially elliptical shape. Transmission projection that reduces the scintillation of image light equivalent to the case where a diffusing agent is added, has no color in the chromaticity in the optical axis direction, and can reduce the chromaticity change from the chromaticity of the optical axis direction light to standing up. It provides a screen.

[0007]

According to the present invention, by changing the surface shape of the image light incident surface of the Fresnel lens sheet of the transmission type projection screen as described above,
Focusing on the change in scintillation, as a result of conducting various studies, the surface of the Fresnel lens sheet on the light incident side of the image light is provided with fine irregularities, a mat shape, or an irregular shape having a diffusing agent as a nucleus. Thus, the present inventors have found that it is possible to reduce the chromaticity change from the front view to the standing view on the observation side while reducing the scintillation, thereby achieving the present invention.

The present invention relates to a light-diffusing screen for a single light source projection television having a Fresnel lens and a lenticular lens, wherein the Fresnel lens sheet has no light-diffusing element, and the Fresnel lens sheet receives image light. A transmission type projection screen characterized by having a fine uneven shape on a side surface.

[0009] The fine irregularities on the light-incident side surface of the Fresnel lens sheet on the light incident side of the image light are mat-shaped. The fine irregularities on the surface of the Fresnel lens sheet on the light incident side of the image light are lens elements having a substantially elliptical cross section in the horizontal direction. Further, the fine irregularities on the surface of the Fresnel lens sheet on the light incident side of the image light are lens elements having a substantially elliptical shape in the vertical direction. In addition, a diffusing agent having the same refractive index as the base material of the Fresnel lens sheet is added to the inside of the sheet, and the light incident side surface of the Fresnel lens sheet for image light has an irregular shape with the diffusing agent as a nucleus. Is what you do.

[0010]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG.
FIG. 1 is a diagram showing a first example of an embodiment of a transmission type projection screen according to the present invention. The transmission type projection screen 10 of this embodiment has a Fresnel lens sheet 11 in which a mat-like irregular shape 11a is formed on the light incident side surface and a circular type Fresnel lens 11b is formed on the light exit side, and the Fresnel lens sheet 11
Lenticular lens sheet 12 in which a lenticular lens for horizontal diffusion (H) is formed on the light entrance side and a black stripe is formed on the light exit side
And Here, the Fresnel lens sheet may be in the form of a sheet or a film. Further, in addition to these two sheets, a front panel sheet or the like may be arranged.

Such a mat-shaped uneven shape 11a is continuously provided on the light incident side surface of the Fresnel lens sheet in the form of unevenness having no regularity. In addition, the mat-shaped irregular shape is obtained by forming a mat surface having fine irregularities on the surface of a cylindrical roll mold used for sheeting of an acrylic plate for producing a Fresnel lens by a sandblast method or the like, and extruding the acrylic plate. In this case, the mat surface can be formed on the surface of the acrylic plate by transferring the mat surface. The matte surface has a Ra (center line average roughness) of 0.1 to less in order to prevent light scattering and diffraction.
1.0 μm, Rz (ten point average roughness) is 1.5 to 10.0
It is desirable to set it to μm.

FIG. 2 is a second example showing an embodiment of a transmission type projection screen according to the present invention. The transmission type projection screen 20 of this embodiment includes:
Lens element 2 having a substantially elliptical cross section in the horizontal direction on the light incident side surface
1a, and a Fresnel lens sheet 21 having a circular Fresnel lens 11b formed on the light exit side.
And a lenticular lens sheet 12 that is disposed on the observation side of the Fresnel lens sheet 21, has a lenticular lens for horizontal diffusion (H) formed on the light incident side, and has a black stripe formed on the light exit side. .

The lens element 21a having a substantially elliptical cross section in the horizontal direction on the light incident side has a regular pitch of one.
It is desirable to arrange them in a semi-elliptical shape with a major axis of about 100 μm and a lens height of about 5 μm. The elliptical shape is formed by cutting a cylindrical roll mold surface used for sheeting an acrylic plate for producing a Fresnel lens into a shape reverse to the elliptical lens element using a lathe machine, By transferring the elliptical shape when the plate is formed, a substantially elliptical lens element can be formed on the surface of the acrylic plate.

FIG. 3 is a third example showing an embodiment of the transmission type projection screen according to the present invention. The transmission type projection screen 30 of this embodiment includes:
A substantially elliptical lens element 31a is formed in the vertical direction on the light incident side, and a Fresnel lens sheet 31 in which a circular type Fresnel lens 11b is formed on the light emitting side, and further arranged on the observation side of the Fresnel lens sheet 31,
A lenticular lens for horizontal diffusion (H) is formed on the light entrance side, and a lenticular lens sheet 12 on which a black stripe is formed on the light exit side.

The lens element 31a having a substantially elliptical cross section in the vertical direction on the light incident side has a regular pitch of about 100 μm, a semi-elliptical shape having a major axis of about 100 μm, and a lens height of about 5 μm. It is desirable to arrange in such a shape. The above-mentioned substantially elliptical shape is formed by cutting a cylindrical roll die surface used for sheeting of an acrylic plate for producing a Fresnel lens into a shape reverse to the elliptical lens element using a lathe, By transferring the elliptical shape during extrusion molding of the acrylic plate, a substantially elliptical lens element can be formed on the surface of the acrylic plate.

FIG. 4 is a fourth example showing an embodiment of the transmission type projection screen of the present invention. The transmission projection screen 40 of this embodiment has a Fresnel lens 41 in which a concave-convex shape having a diffusing agent as a nucleus is formed on the surface on the light incident side and a circular type Fresnel lens 11b is formed on the light exit side, and this Fresnel lens sheet. 4
1 is further arranged on the observation side, and is horizontally diffused (H) on the light incident side.
And a lenticular sheet 12 on which a black stripe is formed on the light output side.

The particle size of 15 μm is formed on the light incident side surface.
The surface property of the uneven mat surface having a diffusing agent of m or less as a nucleus is Ra in order to prevent light scattering and diffraction phenomena.
(Center line average roughness) is preferably 0.1 to 1.0 μm, and Rz (ten-point average roughness) is preferably 1.5 to 10 μm. In addition, the unevenness is obtained by adding a diffusing agent having the same refractive index as that of the acrylic plate at the time of sheeting the acrylic plate for producing the Fresnel lens, and when the diffusing agent is sheeting, the base material of the acrylic plate and the heat shrinkage of the diffusing agent. Due to the difference between the two, it is possible to form a concave-convex shape on the light-incident side surface during extrusion molding of the acrylic plate by utilizing the characteristic that minute irregularities occur on the surface of the acrylic plate.

[0018]

(Example 1) An acrylic plate of a Fresnel lens sheet is made of polymethyl methacrylate resin (refractive index 1.4).
9), a crosslinked bead as an organic diffusing agent (refractive index: 1.49) obtained by crosslinking polymethyl methacrylate having a particle size of 5 μm is added, and a two-layer extrusion method is performed by an extruder for producing a Fresnel lens. It is obtained by molding to a sheet thickness of 2.0 mm. The acrylic plate sheet formed as described above has a very strong light diffusing property on the light incident side surface of the image light because an organic diffusing agent is added in a large amount (15 to 40% by weight) inside. The surface property is Ra (center line average roughness) of 0.5 μm
Thus, a mat surface having an Rz (ten-point average roughness) of 5 μm is obtained. In addition, the circular lens portion of the Fresnel lens sheet is coated on a flat Fresnel lens mold obtained by cutting the reverse shape of the circular lens shape with an ultraviolet curable resin using a Fresnel lens molding machine discharge machine. A thickness of 2.0 mm provided with a matte surface obtained by molding by the above method.
The acrylic sheet is placed with the mat surface facing up by a loading machine, pressed with a nip roll, and cured by irradiating ultraviolet rays with an ultraviolet light source device.
A Fresnel lens sheet having a surface of 8 mm, a height of the Fresnel lens portion of 0.2 mm, a sheet thickness of 2.2 mm, and a matte surface on the light incident side as described above is obtained.

Example 2 The acrylic plate of the Fresnel lens sheet is made of an impact-resistant acrylic resin (refractive index 1.52)
An organic diffusing agent obtained by crosslinking polymethyl methacrylate having the same refractive index as that of the base material and having a particle size of 6.6 μm (refractive index 1.5
2) The crosslinked beads were added, and a sheet thickness of 2.0 m was obtained by a two-layer extrusion method using an extruder for producing a Fresnel lens.
m. The sheet of the acrylic plate molded as described above has, on the light incident side surface of the image light, a surface property, Ra (center line average roughness) of 0.6 μm, and Rz (ten point average roughness). A mat surface of 5.5 μm can be formed.
In addition, the circular lens part of the Fresnel lens sheet is coated with an ultraviolet curable resin on a flat Fresnel lens mold obtained by cutting the reverse shape of the circular lens shape using a discharge machine of a Fresnel lens molding machine, and on it. A 2.0 mm-thick acrylic sheet provided with a matte surface obtained by the above-described molding process is placed on a loading machine with the mat surface facing up, pressed with a nip roll, and irradiated with an ultraviolet light source device. Irradiate and cure, Fresnel lens pitch 0.8m
m, Fresnel lens part height 0.2 mm, sheet thickness 2.2
mm, the Fresnel lens sheet having the matte surface on the light incident side having the above-mentioned surface property is obtained.

Example 3 An acrylic plate of a Fresnel lens was formed into a cylindrical roll mold used for sheeting an acrylic plate for producing a Fresnel lens by sandblasting with a surface property of Ra 0.6 μm and Rz 5.5 μm. Is formed by using an impact-resistant acrylic material and extruding the mat surface onto the light incident side surface of the image light. Thus, an acrylic plate having a sheet thickness of 2.0 mm is obtained. In addition, the circular lens part of the Fresnel lens is coated on a flat Fresnel lens mold with a reverse shape of the circular lens shape, coated with an ultraviolet curable resin using a Fresnel lens molding machine discharge machine. 1. A thickness provided with a matte surface obtained by molding by the above method.
A 0 mm acrylic plate is placed on a loading machine with the mat surface facing upward, pressed with a nip roll, and cured by irradiating ultraviolet rays with an ultraviolet light source device, and has a Fresnel lens pitch of 0.8.
mm, the Fresnel lens part height is 0.2 mm, the Fresnel lens sheet thickness is 2.2 mm, and the matte surface on the light incident side surface of the image light is Ra 0.6 μm and the Rz 5.5 μm is obtained.

Example 4 An acrylic plate of a Fresnel lens sheet was formed in a semi-elliptical shape having a pitch of 100 μm and a major axis of 100 μm in the horizontal direction of a roll on the surface of a cylindrical roll mold used for sheeting of an acrylic plate for producing a Fresnel lens. A lens element having a height of 5 μm and an inverse shape are provided by cutting with a lathe, and are formed by molding with an extruder using an impact-resistant acrylic resin (refractive index: 1.52).
In this way, an acrylic plate having a 2.0 mm sheet thickness and having substantially elliptical lens elements formed in the horizontal direction on the light incident side surface of the image light is obtained. In addition, the circular lens part of the Fresnel lens is coated with a UV curable resin on a flat Fresnel lens mold obtained by cutting the circular lens shape with a Fresnel lens molding machine and then molded by the above method. A 2.0-mm-thick acrylic plate obtained by processing is placed on a loading machine with the light-incident side surface facing upwards, pressed with a nip roll, and cured by irradiating ultraviolet rays with an ultraviolet light source device. A Fresnel lens sheet having 0.8 mm, a Fresnel lens height of 0.2 mm, a sheet thickness of 2.2 mm, and forming the above-mentioned substantially elliptical lens element in the horizontal direction on the light incident side surface is obtained.

Example 5 An acrylic plate of a Fresnel lens sheet was formed on a cylindrical roll mold surface in a semi-elliptical shape with a pitch of 100 μm and a major axis of 100 μm in a direction perpendicular to the roll by using an acrylic sheet sheeting machine for producing a Fresnel lens. A lens element having a height of 5 μm and an inverted shape are provided by cutting with a lathe, extruded with an extruder, and molded with impact-resistant acrylic (refractive index 1.52). Can be In this way, a sheet-shaped acrylic plate having no diffusion element and having a sheet thickness of 2.0 mm, which is substantially elliptical in the direction perpendicular to the light incident side surface of the image light, is obtained. In addition, the circular lens portion of the Fresnel lens is coated with an ultraviolet curable resin on a flat Fresnel lens mold obtained by cutting the inverse shape of the circular lens shape with a discharge machine of a Fresnel lens molding machine, and on that, The acrylic plate having a thickness of 2.0 mm obtained by the above-described method is placed on a loading machine with the light incident side surface in an upward state, pressed with a nip roll, and cured by irradiating ultraviolet rays with an ultraviolet light source device. A Fresnel lens sheet having a Fresnel lens pitch of 0.8 mm, a Fresnel lens part height of 0.2 mm, a sheet thickness of 2.2 mm, and the above-mentioned substantially elliptical lens element formed in a direction perpendicular to the light incident side surface is obtained.

COMPARATIVE EXAMPLE 1 The same shape as in Example 1 was used. The base material was an impact-resistant acrylic material having a refractive index of 1.52. The diffusing agent was a glass bead diffusing agent having a particle diameter of 5 μm and a refractive index of 1.56. And an acrylic plate having a sheet thickness of 2.0 mm is obtained by molding using a material having a refractive index difference from the above. Then, a Fresnel lens sheet is formed from the circular lens portion and the above-mentioned acrylic plate in the same manner as described in Examples 1 to 5.

(Comparative Example 2) The same shape as in Example 1 was used. The base material was a reinforced acrylic material having a refractive index of 1.52. The diffusing agent was an organic diffusing agent having a particle size of 5 μm and having a refractive index of 1.49. A sheet-shaped acrylic plate having a sheet thickness of 2.0 mm is obtained by molding using materials having a refractive index difference from each other. Then, a Fresnel lens sheet is formed from the circular lens portion and the above-mentioned acrylic plate in the same manner as described in Examples 1 to 5.

COMPARATIVE EXAMPLE 3 The same shape as in Example 1 was used. The base material was a metamethyl acrylate material having a refractive index of 1.49, and the diffusing agent was an organic diffusing agent having a particle diameter of 12 μm and having a refractive index of 1.53.
And an acrylic plate having a sheet thickness of 2.0 mm is obtained by molding using a material having a refractive index difference from the above. Then, a Fresnel lens sheet is formed from the circular lens portion and the above-mentioned acrylic plate in the same manner as described in Examples 1 to 5.

Here, the outline of the chromaticity measurement shown in FIG. 5 will be described in detail. Generally, the chromaticity is measured by setting the Fresnel lens sheet on the light incident side of the image light and the lenticular lens sheet on the light emitting side of a single light source type liquid crystal projection television, and measuring the chromaticity of the image light (white light) with a luminance meter. Measure using In this measurement, a lenticular lens sheet which does not contain a diffusing agent serving as a diffusing element inside the lens and does not have a fine mat shape on the surface is used. The chromaticity in the optical axis direction of the light source light of the single light source type liquid crystal projection television as a reference was measured, and it was x: 0.246 and y: 0.271 in the CIE standard color system. Here, a specific chromaticity measuring method will be further described. First, as shown in FIG. 5, a single light source type liquid crystal projection television 50 and a luminance meter 51 for measuring chromaticity are placed on the same plane, and a Fresnel lens is placed in a lens set frame portion of the projection television on a light incident surface side of image light. Then, the lenticular lens sheet is set on the light emitting side. Next, the measurement center of the luminance meter comes at the same height as the center of the TV set at a position 3H perpendicular to the center of the screen (1/2 of the short side H) of the lens set. And measure the chromaticity of the light in the optical axis direction. The chromaticity measurement of the standing angle is performed by changing only the angle so that the center of the measuring unit of the luminance meter is 15 ° with respect to the horizontal direction with respect to the center of the set frame of the projection television, and is measured in the optical axis direction. Calculate the chromaticity difference between light and standing angle.

Next, the chromaticity from the chromaticity of the light in the optical axis direction (chromaticity in the optical axis direction) to the standing angle (chromaticity 15 ° above the optical axis) of the Fresnel lens sheets of Examples 1 to 5 was measured. However, the chromaticity of the light in the optical axis direction substantially matches the chromaticity of the light source light, and the change in chromaticity from the light in the optical axis direction to the viewing angle is smaller than that of the Fresnel lens sheets of Comparative Examples 1 to 3. It turns out that it is small. Here, Tables 1 and 2 show chromaticity differences from the light source chromaticity of the Fresnel lens sheets of Examples 1 to 5.

[0028]

[Table 1]

[0029]

[Table 2]

Next, the chromaticity change from the chromaticity in the optical axis direction to the standing angle of the Fresnel lens sheets described in Comparative Examples 1 to 3 was measured. Although the change in chromaticity from to the viewing angle is small, the chromaticity of the light in the optical axis direction is slightly yellow compared to the Fresnel lens sheets of Examples 1 to 5. Comparative Examples 2 and 3
In the Fresnel lens sheet described in (1), the chromaticity of the light in the optical axis direction largely fluctuates to yellow as compared with the Fresnel lens sheets of Examples 1 to 5, and the chromaticity change from the optical axis direction to the standing angle is large. As described above, when the vertical viewing angle is changed, the chromaticity change visually perceived is large. Here, Table 3
3 shows the chromaticity differences of the Fresnel lens sheets of Comparative Examples 1 to 3.

[0031]

[Table 3]

[0032]

As described above, according to the present invention, there is no light diffusing element inside the Fresnel lens sheet, and the Fresnel lens sheet has fine irregularities on the light-incident side surface of the image light, so that the screen motherboard has The same effect of reducing the scintillation of image light as when a diffusing agent having a difference in refractive index is added to the material is obtained, and there is no coloring in the chromaticity in the optical axis direction. Thus, there is an effect that a transmission type projection screen which can reduce the change in chromaticity can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first example of a transmission type projection screen of the present invention.

FIG. 2 is a diagram illustrating a second example of the transmission type projection screen of the present invention.

FIG. 3 is a diagram illustrating a third example of the transmission type projection screen of the present invention.

FIG. 4 is a diagram illustrating a fourth example of the transmission type projection screen of the present invention.

FIG. 5 is a diagram illustrating a method for measuring the chromaticity of a projection screen.

FIG. 6 is a diagram illustrating a projection screen.

[Description of Signs] 10 Transmission type projection screen 11 Fresnel lens sheet 11a Irregular shape with mat-shaped light incident side surface 11b Fresnel lens 12 Lenticular lens sheet 20 Transmission type projection screen 21 Fresnel lens sheet 21a Light incident side surface is horizontal Substantially elliptical lens shape 30 Transmission type projection screen 31 Fresnel lens sheet 31a Lens shape with light incident side surface substantially elliptical in the vertical direction 40 Transmission type projection screen 41 Fresnel lens sheet 41a Light entrance side surface has a diffusing agent as a core Mat-shaped unevenness 50 LCD projection television 51 Luminance meter

Claims (5)

[Claims] 1. A light diffusing screen for a single light source type projection television comprising a Fresnel lens and a lenticular lens, wherein the Fresnel lens sheet has no light diffusing element and the Fresnel lens sheet has a light incident side of image light. A transmission type projection screen characterized by having fine irregularities on its surface. 2. The transmissive projection screen according to claim 1, wherein the fine irregularities on the surface of the Fresnel lens sheet on the light incident side of the image light have a mat shape. 3. The transmission projection screen according to claim 1, wherein the fine irregularities on the light incident side surface of the Fresnel lens sheet are lens elements having a substantially elliptical cross section in the horizontal direction. 4. The transmission type projection screen according to claim 1, wherein the fine irregularities on the light incident side surface of the Fresnel lens sheet are lens elements having a substantially elliptical cross section in the vertical direction. 5. A Fresnel lens sheet, wherein a diffusing agent having the same refractive index as the base material of the Fresnel lens sheet is added to the inside of the sheet, and the Fresnel lens sheet has a concave-convex shape having a diffusing agent as a nucleus on a light incident side surface of image light. Item 4. A transmission type projection screen according to Item 2.