JP2000352608A - Light-diffusing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet having optimum diffusion characteristics for an observer and to suppress decrease in the contrast when the sheet is used for a transmission type display device or the like by forming a plurality of grooves each having almost V-shape cross section parallel to one another either in a one-dimensional direction or in two-dimensional directions on the observation face of a light-diffusing layer. SOLUTION: The transparent base sheet 12 used consists of a transparent resin sheet such as a polyethylene terephthalate sheet, and the light emitted from a light source enters the entrance face 12A and can transmit in the thickness direction of the sheet. The light-diffusing layer 14 laminated on the transparent base sheet 12 consists of a UV-curing transparent resin, and a plurality of grooves 18 each having a V-shape cross section are formed parallel to one another in a one-dimensional direction on the observation face 14A of the light- diffusing layer 14. Further, the light-transmitting sheet 16 applied to cover the observation face 14A consists of a transparent resin sheet same as the transparent base sheet 12, and a light-absorbing layer 20 consisting of resin having a low refractive index and colored into black is formed on the surface of the light-transmitting sheet 16 facing the grooves 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source suitable for a CRT display device used for a computer or a television, a liquid crystal display device or a plasma display device, and a rear projection display device using a CRT or a liquid crystal light valve. The present invention relates to a diffusion sheet, a transmission screen using the light diffusion sheet, and a transmission display device.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display devices, CRT display devices, various projection display devices, and the like using a light diffusion sheet as a screen in order to enhance the visibility of an observer are known.

The light diffusing sheet is, for example, a light transmissive film whose surface is made uneven, a resin film containing light diffusing fine particles, and a columnar lens.
There is a lenticular lens sheet or the like arranged in parallel on two planes. In addition, a combination of two or three of these sheets is used.

[0004] These devices use a difference in refractive index between a film, the atmosphere, fine particles and the like to refract image light in multiple directions at these boundaries, diffuse the image light over a wide range, and emit the image light to the observer side. This improves visibility.

[0005]

However, on the other hand, a large amount of light-diffusing fine particles and a sheet surface on which many irregularities are formed cause irregular reflection of image light to generate a lot of stray light. This has led to a decrease in surface brightness and a decrease in contrast.

[0006] In addition, those having a diffusivity due to the surface unevenness treatment have an angle dependence in the diffusivity and transparency, and there is a problem that the visibility changes depending on the viewing angle of the display. For example, in a display,
Although an image with good visibility can be obtained from the front, there is a phenomenon that the image becomes white as the viewing angle increases.

On the other hand, the light diffusing property of the light diffusing sheet also leads to an increase in the scattered reflection of external light, resulting in a problem that the contrast is remarkably reduced and an image is easily blurred.

In particular, when the light diffusion sheet is used in a liquid crystal display device using cholesteric liquid crystal, scattered light of external light generated by the light diffusion sheet is incident on the liquid crystal element from all angles, so that an observer can observe the light. There has been a problem that a color tone change is caused by a change in the viewing angle.

The present invention has been made in view of the above problems, and diffuses image light by a method different from the conventional method.
It is an object of the present invention to provide a light diffusion sheet that suppresses a decrease in contrast, a transmission screen using the light diffusion sheet, and a transmission display device.

[0010]

According to the present invention, there is provided a light diffusion sheet provided with a light diffusion layer for diffusing light transmitted in a thickness direction, wherein a plurality of substantially V-shaped cross sections are provided on an observation surface of the light diffusion layer. The above object is achieved by a light diffusion sheet characterized in that the grooves are formed in parallel in either one-dimensional direction or two-dimensional direction.

In the light diffusion sheet, the groove may have a sectional shape in which two sides of the V-shape are equal in length.

Further, the angle between the two walls constituting the groove and the observation surface connected to each of the two walls may be 95 degrees to 105 degrees.

Further, the groove may be filled with a substance which is any of gas, liquid and solid and has a lower refractive index than the light diffusion layer.

Further, both walls constituting the groove may be covered with a substance which is either liquid or solid and has a lower refractive index than the light diffusion layer.

Still further, the substance may be a particulate solid.

Still further, the substance may be a black liquid or solid.

The substance may be a resin.

Further, a light absorbing layer may be provided in the groove.

Further, a light-transmitting sheet may be provided in contact with the observation surface, and a light-absorbing layer may be provided on a surface of the light-transmitting sheet facing the groove.

Further, a second light diffusion layer for diffusing light transmitted in the thickness direction may be arranged on the incident surface side of the light diffusion layer.

Further, a plurality of prisms may be provided on the incident surface side of the light diffusion layer.

Furthermore, at least one of an antireflection layer, a polarizing filter layer, an antistatic layer, an antiglare treatment layer, and a hard coat layer may be provided on the observation surface side of the light diffusion layer.

According to a second aspect of the present invention, there is provided a transmissive screen including the light diffusion sheet according to the first aspect of the invention and a Fresnel lens sheet disposed on an incident side of the light diffusion sheet in parallel with the light diffusion sheet. Thereby, the above object is achieved.

According to a third aspect of the present invention, the above object is achieved by a transmissive display device comprising the light diffusion sheet of the first aspect.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a light diffusion sheet 10 according to a first embodiment of the present invention comprises a transparent base sheet 12, a light diffusion layer 14, and a light transmissive sheet 16. They are stacked in this order from the light source side.

The transparent substrate sheet 12 is made of a transparent resin sheet, for example, a polyethylene terephthalate (PET) sheet, and the light (image light) emitted from the light source is incident on the incident surface 12.
A, and the light can be transmitted in the thickness direction.

The light diffusion layer 14 laminated on the transparent substrate sheet 12 is made of an ultraviolet-curable transparent resin, and a plurality of grooves having a V-shaped cross section are formed on the observation surface 14A of the light diffusion layer 14. 18 are formed in parallel in a one-dimensional direction (the left-right direction in FIG. 1).

The translucent sheet 16 disposed so as to cover the observation surface 14A is made of a transparent resin sheet such as a PET sheet like the transparent base sheet 12, and the translucent sheet 16 in the translucent sheet 16 is used. A light-absorbing layer 20 made of a resin having a low refractive index and colored in black is provided on the surface facing the groove 18. The remaining space of the groove 18 is filled with air.

The groove 18 has a V-shaped cross section V-shaped.
The two sides 18A of the groove corresponding to each side of the V-shape are formed so that the lengths of the sides are equal.
A between each observation A and the observation surface 14A that is continuous with
, Respectively, such that 95 degrees ≦ α ≦ 105 degrees.

Therefore, when the angle α is 100 degrees, as shown in FIG. 2A, the incident light N which is perpendicularly incident on the incident surface 12A is 10 ° incident on the wall 18A.
It has a tilt angle of degrees and is totally reflected at the wall 18A. The totally reflected light exits at an inclination angle of about 20 degrees with respect to the direction perpendicular to the observation surface 14A, and the light-transmitting sheet 1
At 6, the light is slightly refracted and becomes the emitted light S to the observer side. or,
Incident light N that has not been reflected by the wall 18A and has passed between the grooves 18 is linearly emitted toward the observer without being refracted.

Similarly, as shown in FIG.
The incident light N is ± 15 with respect to the direction perpendicular to the incident surface 12A.
When set to be diffused within a range of degrees, the wall 1
8A and the light totally reflected by the wall 18A,
Approximately ± 30 including light transmitted between each groove 18.
The light is emitted in a diffusion angle range of degrees to about ± 40 degrees.

As shown by the dotted line in FIG. 2, diffused light generated by external light and stray light generated by other factors do not undergo total reflection because the angle of entering the wall 18A is large. The light is refracted into and absorbed by the light absorbing layer 20.

Next, a method and an apparatus for manufacturing the light diffusion sheet 10 will be described with reference to FIG.

The manufacturing apparatus 22 used in the first step is shown in FIG.
As shown in FIG. 2A, a forming roll 24 having a convex portion 24A having a shape opposite to that of the desired groove 18 (the convex portion 24A is exaggerated) is formed on the surface,
4 and the transparent substrate sheet 12 is
4, a pressing roll 26 that can be pressed against
A peeling roll 27 that is disposed in contact with and is capable of peeling off the cured sheet on the forming roll 24;
A coating nozzle 28 capable of uniformly applying an ultraviolet curable resin to the surface of the roll, a pump 30 for supplying the ultraviolet curable resin to the coating nozzle 28, and an ultraviolet light applied to the roll surface of the forming roll 24. An ultraviolet irradiation device 32 for curing the curable resin.

In order to obtain the light diffusion sheet 10, first, an ultraviolet curable resin is applied to the surface of the forming roll 24. The transparent base sheet 12 is guided by the pressing roll 26 so as to be laminated on the ultraviolet curable resin layer, and thereafter, ultraviolet rays are irradiated from the outside. Ultraviolet rays pass through the transparent base material sheet 12 to cure the ultraviolet curable resin layer, and are separated from the forming roll 24 by the peeling roll 27 in a state where the resin and the transparent base material sheet 12 are integrated. . Accordingly, as shown in an enlarged manner in FIG. 3A, the light diffusion layer 15 having the desired grooves 18 formed on the surface thereof is laminated on the transparent base sheet 12, and the first step is completed.

Next, the manufacturing apparatus 34 used in the second step is:
As shown in FIG. 3B, a pair of pressing rolls 36 that can sandwich and press two sheets together, an ultraviolet irradiation device 32 that irradiates ultraviolet light to the sheet that has passed through the roll pair 36, It is comprised including.

In the second step, the pressing roll pair 3
The sheet manufactured in the first step is supplied from above the light-transmitting sheet 16 supported in the horizontal direction by sandwiching the light-diffusing layer 15 against the light-transmitting sheet 16. . In addition, as shown by the two-dot chain line,
It is also preferable to apply an adhesive layer to the surface of the translucent sheet 16 from the beginning in order to enhance the mutual adhesion.

A low-refractive-index resin 37 colored black is supplied between the two sheets on the roll entry side of the press roll pair 36. The low-refractive-index resin 37 is pushed into the groove 18 by the holding force of the pair of pressing rolls 36, and these sheets are integrally carried out. The low-refractive-index resin 37 has an ultraviolet curing property, and then is cured by irradiating ultraviolet rays to form the light absorbing layer 20 shown in FIG. 1 and finally obtain the light diffusing sheet 10. Can be.

In addition to the above-mentioned manufacturing method, for example, a hot pressing method using a known thermoplastic resin, or a method in which a thermoplastic or curable resin is filled in a mold having a shape reverse to that of the light diffusion layer 15 and molded. The light diffusion sheet 10 can be manufactured by the injection molding method described below. When these methods are used, the transparent base sheet 12 is omitted, so that the light diffusion sheet 10 can be further thinned.

As shown in FIG. 2, the light diffusion sheet 10 has a light diffusion characteristic having directivity in a direction perpendicular to the direction in which the grooves 18 are formed. Therefore, the groove 1
When the light diffusion sheet 10 is installed on a display such that the light 8 is in the vertical direction, incident light (image light) is diffused mainly in the horizontal direction, so that the display is very easy for an observer to see.

Most of the stray light passing through the light diffusion sheet 10 is absorbed by the light absorbing layer 20, so that a decrease in contrast and the like can be prevented. The light absorbing layer 20 also functions as a black stripe (BS), so that a high-contrast image can be obtained.

The external light incident on the light diffusion sheet 10 from the observer side, except for the one that is directly absorbed by the light absorbing layer 20, follows the light path shown in FIG.
Outgoing to the side. Therefore, even in the case of external light obliquely incident on the observer side surface, the traveling direction is corrected in a direction perpendicular to the boundary surface of each layer, so that total reflection at each boundary can be suppressed, External light can be effectively absorbed on the rear surface of the display.

On the other hand, the above properties are also effective when used in a reflective display device. That is, the light diffusion sheet 10 is located closer to the viewer than the reflection plate of the reflection type display.
Is installed, the external light can be made incident on the reflector in a direction perpendicular to the reflector, and the light reflected by the reflector can be diffused again and emitted to the observer side. Use is planned.

Further, the above-mentioned property is satisfied by the light diffusing sheet 1
This is also effective when 0 is used for a liquid crystal display device. That is, as a result of external light always being incident on the liquid crystal element in a substantially vertical direction, it is possible to suppress a change in color tone due to a change in the viewing angle of the observer.

Next, a light diffusion sheet 10A according to a second example of the embodiment shown in FIG. 4 will be described.

In the light diffusion sheet 10A, a plurality of columnar prisms 40 each having a trapezoidal cross section perpendicular to the groove 18 are arranged in parallel on the incident surface 12A of the light diffusion sheet 10 shown in the first example of the embodiment. It is formed. Since other configurations are almost the same as those of the light diffusion sheet 10 of the first example of the embodiment, the same parts as those of the light diffusion sheet 10 are denoted by the same reference numerals, and the description is omitted.

The light diffusion sheet 10A is connected to the light path A shown in FIG.
As shown in the figure, since the image light obliquely incident on the light diffusion sheet 10A is totally reflected inside the columnar prism 40 and can be perpendicularly incident on the light diffusion layer 14, particularly, It is suitable for use in a rear projection display device or the like in which image light is projected onto a screen from obliquely above or below.

Also, unlike the lenticular lens sheet having an arc-shaped unevenness on the incident surface, the light diffusing sheet 10A can directly form the columnar prism 40 on the incident surface side. 10 makes it possible to configure a screen.

Although the light diffusing sheet 10A has a plurality of columnar prisms 40 each having an equilateral triangular cross section, the present invention is not limited to this.
Any type of mold can be selected depending on the application, such as a cylinder type or a rope-eye type. Further, fine irregularities may be formed on the surfaces of these prisms so as to have a light diffusing property.

In the light diffusion sheets 10 and 10A, the case where the groove 18 is filled with air has been described, but the present invention is not limited to this. This groove 18
Is preferably filled with a substance having a lower refractive index than that of the light diffusion layer 14 (a gas, a liquid, or a solid can be used). More preferably, the substance is colored black and the light absorption layer and the BS are filled. You may make it also serve the role.

Further, for convenience in manufacturing the light diffusion sheets 10 and 10A, the substance may be formed into fine particulate solids and laid inside the grooves 18. In this case, since the interface is air, the refractive index of the substance can be freely set, and a preferable situation is provided for coloring the substance black.

Further, the light diffusion sheet according to the present invention is not limited to the case where the groove 18 is filled with a substance.
The liquid or solid substance may be applied to 8A to totally reflect incident light on the wall 18A.

However, considering the easiness of production, it is preferable to use a resin other than air, and in particular, in order to prevent outflow during use, the resin is cured by ultraviolet rays or electron beams. It is desirable to use a possible curable resin.

Next, a transmission screen 42 according to a third example of the embodiment shown in FIG. 5 will be described.

The transmissive screen 42 includes a light diffusion sheet 10 B in which a second light diffusion layer 46 containing light diffusing fine particles 44 is laminated in place of the transparent base sheet 12, and an incident light of the light diffusion sheet 10 B. And a Fresnel lens sheet 48 disposed on the surface 14A side.

According to the transmission type screen 42, first, the image light is condensed in the vertical direction on the screen by the Fresnel lens sheet 48, and is vertically incident on the second light diffusion layer 46. The second light diffusion layer 46 is isotropic
The diffusion characteristics are set to an angle range of 15 degrees, and the image light that has passed through the second light diffusion layer 46 has passed through the light diffusion layer 14 and has been approximately ±± as shown in FIG. It will be emitted with a diffusion angle of 30 degrees to about ± 40 degrees.

Therefore, if this transmission type screen 42 is installed in the rear projection type display so that the groove 18 is vertical, the horizontal diffusion angle range is about ± 30 degrees to about ± 40 degrees, and the vertical diffusion angle range is It is possible to obtain an optimal outgoing light having an angle range of about ± 15 degrees.

The second light diffusing layer 46 is not limited to the one using the light diffusing fine particles 44. The second light diffusing layer 46 may be formed into a mat by treating the surface with fine irregularities, or the light diffusing layer shown in the example of the embodiment. 14 may be arranged.

Next, a transmission type display device 48 according to a fourth example of the embodiment shown in FIG. 6 will be described.

The transmissive display device 48 includes two first and second light diffusion sheets 50 and 50A, a first polarizing sheet 52, and a liquid crystal panel 54 similar to those shown in the first example of the embodiment. , The second polarizing sheet 52A, and the backlight device 56 are arranged in this order from the most observer side. The liquid crystal panel 54 includes a color filter layer,
A transparent electrode layer, a liquid crystal layer and the like are laminated in a predetermined order.

The backlight device 56 is set by an array-like prism sheet or the like so that the light source light has an isotropic diffusion angle range of about ± 15 degrees. Also, the first and second light diffusion sheets 50 and 50A are formed with each other in a groove 1.
8 are displaced by 90 degrees so that the directions are vertical.

According to the transmissive display device 48, about ± 1 light passing through each of the polarizing sheets 52 and 52 A and the liquid crystal panel 54.
The image light in the diffusion range of 5 degrees is diffused by the first and second light diffusion sheets 50 and 50A in the range of about ± 30 degrees to about ± 40 degrees in the two-dimensional direction, and emitted.

Therefore, it is possible to obtain a transmissive display device 48 having a high contrast and a wide viewing angle and excellent visibility.

In order to obtain emitted light having a two-dimensional diffusion characteristic, a plurality of the grooves 18 are formed in the diffusion layer of one light diffusion sheet in parallel in the two-dimensional direction.
That is, it is also preferable to form the mesh.

The observation surface 14 of the light diffusion sheet 10, 10A, 10B, 50, 50A shown in the example of the above embodiment.
It is also preferable to provide at least one of an antireflection layer, a polarizing filter layer, an antistatic layer, an antiglare treatment layer, and a hard coat layer on the side. Here, the outlines of the antireflection layer, the low refractive index layer, the polarizing filter layer, the antistatic layer, the antiglare treatment layer, and the hard coat layer will be described.

First, the antireflection layer can be obtained by, for example, laminating a film having a function of suppressing the reflectance of external light entering the surface, or directly performing antireflection treatment on the surface of the light diffusion sheet. The film preferably has a refractive index of less than 1.60, more preferably 1.60.
45 or less.

The anti-glare treatment layer can be obtained by laminating a film having an anti-glare function or by directly performing anti-glare treatment on the light diffusion sheet surface. In addition, this anti-glare film has a type in which particles such as cohesive silica are aggregated on the surface to form an uneven shape on the surface, and an organic filler having a particle diameter equal to or larger than the thickness of the resin coating is coated in the resin coating. To be added to
There is a type that forms an uneven shape on the surface of the resin layer.

The antistatic layer can be obtained by laminating an antistatic film on the surface or by directly performing an antistatic treatment on the surface of the light diffusion sheet.

The hard coat layer can be obtained by laminating an abrasion-resistant film whose surface strength is increased to prevent scratches or the like, or by directly hard-coating the light diffusion sheet surface.

The polarizing filter layer is the same as that of the fourth embodiment.
It serves as the first polarizing sheet 52 of the transmission type display device 48 shown in the example, and is obtained by directly laminating this polarizing sheet on the surface of the light diffusion sheet.

The light diffusing sheet according to the present invention is not limited to the light diffusing sheet having the light absorbing layer 20 and the light transmissive sheet 16, and the groove has a V-shaped cross section. Are not limited to those in which. These are appropriately determined in consideration of the contrast, luminance, diffusion characteristics, and the like required according to the use of the light diffusion sheet.

As described above, the light diffusion sheet, the transmission screen, and the transmission display device according to the present invention have been specifically described through the examples of the embodiments. However, the present invention is not limited to these. The present invention includes a combination of the features of the light diffusing sheet shown in the specific examples, and a simple design change without departing from the gist of the present invention.

[0074]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A transmission type display device according to an embodiment of the present invention will be specifically described.

As shown schematically in FIG. 7, the transmissive display device 48A uses a liquid crystal light valve 58 as an image light source, and diagonally above the liquid crystal light valve 58 according to the second embodiment of the present invention. The liquid crystal light valve 58 is provided with the diffusion sheet 10A.
The video light is projected obliquely upward toward.

The positional relationship between the liquid crystal light valve 58 and the light diffusion sheet 10A is such that the angle between the image light beam emitted from the liquid crystal light valve 58 to the upper end of the light diffusion sheet 10A and the light diffusion sheet 10A is 30 degrees. The angle between the image light source emitted to the lower end of the diffusion sheet 10A and the light diffusion sheet 10A is set to be 45 degrees.

As shown in FIG. 8, the light diffusion sheet 10A is arranged so that the groove 18 is in the vertical direction and the columnar prism 40 is in the horizontal direction.

The columnar prism 40 has an apex angle of 37 degrees and is curved in a horizontal direction into a substantially concave arc shape. This is to prevent the image light emitted from the liquid crystal light valve 58 from being distorted on the left and right sides in the horizontal direction, since the image light travels radially. The columnar prism 4
0 is matted, and isotropic about ±
It is set so that diffused light of 15 degrees is obtained.

The size of the groove 18 is set so that the apex angle is 10 degrees, and the inside of the groove is filled with black particles. The size of each groove 18 is such that the pitch L between the grooves 18 is twice as large as the maximum width S of the groove 18.

When the characteristics of the light diffusing sheet 10A in the transmissive display device 48A were examined, the result was a reflectance of about 4.5% and a transmittance of about 85%. When an anti-reflection film is laminated on the surface of the light diffusion sheet 10A on the most observer side, the reflectance is about 50.8% and the transmittance is about 8%.
The result was 8%.

[0081]

According to the present invention, a light diffusion sheet having an optimum diffusion characteristic for an observer and in which a decrease in contrast is suppressed, a transmission screen using the light diffusion sheet, a transmission display device Can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a light diffusion sheet according to a first example of an embodiment of the present invention.

FIG. 2 is a schematic view showing a state in which incident light of the light diffusion sheet is diffused.

FIG. 3 is a schematic view showing a manufacturing apparatus and a manufacturing method of the light diffusion sheet.

FIG. 4 is a perspective view showing a light diffusion sheet according to a second example of the mortuary body according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a transmission screen according to a third example of the mortuary body according to the embodiment of the present invention;

FIG. 6 is a perspective view showing a transmission type display device according to a fourth example of a corpse according to the present invention.

FIG. 7 is a schematic side view showing a transmission type display device according to an embodiment of the present invention.

FIG. 8 is a perspective view showing a light diffusion sheet used in the transmission type display device.

[Explanation of symbols]

 10, 10A: Light diffusion sheet 12: Transparent base sheet 12A: Incident surface 14, 46: Light diffusion layer 14A: Observation surface 16: Translucent sheet 18: Groove 20: Light absorbing layer 40: Columnar prism 42: Transmission type Screen 46A: second light diffusion layer 48, 48A: transmissive display device

Claims (15)

[Claims] 1. A light diffusion sheet having a light diffusion layer for diffusing light transmitted in a thickness direction, wherein a plurality of grooves each having a substantially V-shaped cross section are formed on an observation surface of the light diffusion layer.
A light diffusion sheet formed in parallel in one of a two-dimensional direction and a two-dimensional direction. 2. The light diffusion sheet according to claim 1, wherein the cross-sectional shape of the groove is such that two sides of the V-shape are equal in length. 3. The angle according to claim 1, wherein an angle between both walls constituting the groove and the observation surface continuous with each of the two walls is 95 to 105 degrees. Light diffusion sheet. 4. The groove according to claim 1, 2 or 3, wherein the groove is filled with a substance that is one of gas, liquid and solid and has a lower refractive index than the light diffusion layer. Light diffusion sheet. 5. The device according to claim 1, wherein both walls constituting said groove are covered with a substance which is either liquid or solid and has a lower refractive index than said light diffusion layer. Characteristic light diffusion sheet. 6. The light diffusion sheet according to claim 4, wherein the substance is a particulate solid. 7. The light diffusing sheet according to claim 4, wherein the substance is a black liquid or a solid. 8. The light diffusion sheet according to claim 4, wherein the substance is a resin. 9. The light diffusion sheet according to claim 1, wherein a light absorbing layer is provided in the groove. 10. A light-transmitting sheet according to claim 1, wherein a light-transmitting sheet is disposed in contact with said observation surface, and a light-absorbing layer is provided on a surface of said light-transmitting sheet facing said groove. A light diffusion sheet, which is provided. 11. The light diffusion layer according to claim 1, further comprising: a second light diffusion layer for diffusing light transmitted in a thickness direction, on a light incident surface side of the light diffusion layer. Light diffusion sheet. 12. The light diffusion sheet according to claim 1, wherein a plurality of prisms arranged in a substantially concentric arc shape or in parallel are provided on the incident surface side of the light diffusion layer. 13. The method according to claim 1, wherein at least one of an anti-reflection layer, a polarizing filter layer, an anti-static layer, an anti-glare treatment layer, and a hard coat layer is provided on the observation surface side of the light diffusion layer. A light diffusion sheet, which is provided. 14. A transmission comprising: the light diffusion sheet according to any one of claims 1 to 13; and a Fresnel lens sheet disposed parallel to the light diffusion sheet on an incident side of the light diffusion sheet. Type screen. 15. A transmissive display device comprising the light diffusion sheet according to claim 1. Description: