JP2007249185A - Light diffuser and transmissive screen - Google Patents

Abstract

Light diffuser and transmission capable of suppressing shift of color tone of light source light when viewed through light diffuser and eliminating white light source from being colored when passing through light diffuser The object is to provide a mold screen.
A light diffusing body 1 of the present invention is formed of a transparent resin and spherical fine particles having a refractive index different from that of the transparent resin, and scatters all the spherical fine particles contained per unit area of the light diffusing body 1. A value (E) obtained by dividing the sum of the cross-sectional areas by the sum of the geometric cross-sectional areas of all the spherical fine particles is calculated for each central wavelength in the blue, green, and red wavelength regions, and the calculated blue, green, and red are calculated. When the maximum value (E _max ) and the minimum value (E _min ) are compared among the values (E) in the wavelength region, the relationship of E _min / E _max ≧ 0.90 is satisfied.
[Selection] Figure 1

Description

  The present invention relates to a light diffuser and a transmissive screen, and suppresses a shift in color tone of light source light when the light source is viewed through the light diffuser. In particular, a white light source is colored when the light diffuser is passed through. The present invention relates to a light diffuser and a transmissive screen that can prevent the phenomenon that appears.

  Conventionally, light diffusers have been used in various optical applications including transmission screens.

  Light diffusers used in transmissive screens must have the characteristics that the projector's light source on the back cannot be seen directly and the brightness of the entire screen will not decrease. A light diffusing plate (see Patent Document 1) and a transmissive screen (see Patent Document 2) in which a balance between transmission and diffusion is considered have been proposed.

  In addition, in a transmissive screen that can be seen through the projector side, the projector is not installed in the front but is installed obliquely so that the light source cannot be seen directly.

  However, even when installed obliquely, the light source may be visible near the screen. In addition, if a transparent screen that can be seen through has a high haze, the projector may be installed in the front, and in that case, the light source may be seen.

  In these cases, when the light source is viewed through the light diffuser, a phenomenon occurs in which the light source looks red, yellow, blue, or the like. For this reason, there is a problem that the color of the light source having a color overlaps with the image projected on the screen and the image appears to be colored.

JP-A-1-269901 (prior art) Japanese Patent Laying-Open No. 2005-024942 (Problems to be Solved by the Invention)

  Accordingly, the present invention provides a light diffuser that suppresses the color tone of the light source light from shifting when the light source is viewed through the light diffuser and prevents the phenomenon that the white light source appears colored when it passes through the light diffuser. An object is to provide a transmission screen.

  In order to achieve the above object, the present inventors have proposed an internal scattering system to which Mie scattering theory is applied, that is, a scattering system in which fine particles having a particle diameter of 50 μm or less having different refractive indexes are dispersed in a transparent medium. We have intensively studied the wavelength dependence of the scattering property. As a result, the phenomenon that the color of the light source seen through the light diffuser shifts to a color tone such as red, yellow, and blue is due to the wavelength dependence of the scattering cross section that determines the light scattering property, and the scattering cross section The wavelength dependence depends on the particle size distribution, and it has been found that the above phenomenon can be prevented by giving an appropriate scattering cross section distribution characteristic considering the particle size distribution, and the present invention has been completed.

That is, the light diffusing body of the present invention is a light diffusing body formed of a transparent resin and spherical fine particles having different refractive indexes, and all the spherical shapes included per unit area of the light diffusing body. When a value obtained by dividing the sum of the scattering cross sections of the fine particles by the sum of the geometric cross sectional areas of all the spherical fine particles (hereinafter referred to as effective scattering efficiency) is calculated for each of a plurality of wavelengths, The minimum value (E _min ) of the value is 90% or more of the maximum value (E _max ).

In particular, the effective scattering efficiency (E) is calculated for each central wavelength in the blue, green, and red wavelength regions, and the maximum value (E _max ) among the calculated values (E) in the blue, green, and red wavelength regions. ) And the minimum value (E _min ), the relationship of E _min / E _max ≧ 0.90 is satisfied.

  The effective scattering efficiency E of the light diffuser can be expressed by (Equation 1) when the particle size distribution function is f (r).

式（１）中、Ｑは１個の球状微粒子の散乱断面積で波長λと粒子径ｒの関数、f(r)は粒子径分布関数を表す。ｒ_maxは、粒子の最大粒子半径を表す。

In the formula (1), Q is a scattering cross section of one spherical fine particle and is a function of the wavelength λ and the particle diameter r, and f (r) is a particle diameter distribution function. r _max represents the maximum particle radius of the particle.

The scattering cross section Q of one spherical fine particle is obtained by (Equation 2) by Mie's scattering theory, where the refractive index of the fine particle is n _s , the refractive index of the transparent resin is n _m , and the wavelength of incident light is λ. Can do.

［ここでＲは｛｝内の実数部を表す。］

[Where R represents the real part in {}. ]

It is. In addition, ψ ′ _k (z) and ζ ′ _k (z) in Equation (3) and Equation (4) represent the differentiation of ψ _k (z) and ζ _k (z) with respect to z, respectively, J _{k + 1/2} (z) and Y _{k + 1/2} (z) in equation (8) are Bessel functions of the first kind and second kind, respectively. Note that i is an imaginary unit.

  The transmission screen of the present invention is characterized by comprising the light diffuser.

Hereinafter, the principle by which the light diffuser of the present invention can suppress the wavelength shift of scattered light will be described.
As a method for scattering light, there are external scattering in which light is scattered by fine irregularities on the surface and internal scattering in which light is scattered by a minute refractive index distribution inside the light diffuser. The light diffuser of the present invention is a light diffuser that scatters light by internal scattering. In general, external scattering is not scattering when the surface irregularities are filled, so the light diffuser cannot be used with another member attached with an adhesive or the like, but internal scattering is related to the surface state. Therefore, it can be used by being bonded to another member with an adhesive or the like.

  In order to create a minute refractive index distribution to cause internal scattering, a method of dispersing spherical fine particles having a refractive index different from that in a transparent resin is generally used. The method is adopted.

  In this kind of light diffuser, even if it is the same light diffuser, the light scattering property changes with wavelengths of incident light. This is because, even in the same combination of transparent resin and spherical fine particles, the scattering cross section that determines the light scattering property varies depending on the wavelength of incident light. That is, the light scattering property (scattering cross section) is different for each of the blue, green, and red wavelengths constituting the white light of the projector. When incident light passes through the light diffuser, light with a wavelength having a large scattering cross-section is easily scattered, so that the amount of parallel light rays of the wavelength transmitted without being scattered is relatively small. On the other hand, for light having a wavelength with a small scattering cross section, the light is not scattered so much, so that the amount of parallel light rays in the wavelength region that are transmitted without being scattered is relatively large. As a result, when the light source that has passed through the light diffuser is viewed, a phenomenon occurs in which the white light source light appears to be shifted to a color tone such as red, yellow, and blue.

  Furthermore, the diameter of the spherical fine particles used for this application is generally 50 μm or less, but the scattering cross section of the spherical fine particles having a particle diameter in this range varies greatly depending on the particle diameter. FIG. 6 shows an example in which the scattering cross section per geometric cross section of the spherical fine particles (hereinafter, this may be referred to as “scattering efficiency” of the particles) is plotted against the particle diameter. From this figure, it can be seen that the particle diameters exhibiting substantially the same scattering efficiency for light of all the wavelengths of blue, green and red are only in a very narrow range (in the case of FIG. 6, around 4.6 μm). If monodispersed spherical fine particles having a diameter in this range are used, the color tone of the light source light hardly shifts. However, the use of monodispersed spherical fine particles is expensive, and the allowable range of particle diameters is extremely narrow, so that even if the particle diameter variation between lots of particles is taken into account, the cost increases and stable light scattering is maintained. It will be difficult to do.

  On the other hand, it is possible to use polydisperse spherical fine particles having a particle size distribution, but the scattering efficiency of particles having various diameters contained therein varies greatly even within the range of the included particle diameters. It can be seen that there is no point in comparing the scattering efficiency with the average particle size.

  On the other hand, in the present invention, the light source is viewed through the light diffuser by reducing the difference in scattering due to the respective wavelengths of blue, green, and red in consideration of the particle size distribution of the spherical fine particles forming the light diffuser. It is possible to prevent the color tone of the light source light from shifting, particularly when the white light source appears to be colored.

  Hereinafter, embodiments of the light diffuser of the present invention will be described.

The light diffuser of the present invention has a light diffusion layer formed of a transparent resin and spherical fine particles having different refractive indexes. The light diffusion layer, the minimum value of the plurality of effective scattering efficiency E was calculated for each wavelength (E _min) is the maximum value (E _max) of more than 90%, i.e., the maximum value (E _max) and minimum (E _min The ratio E _min / E _max to 0.9) is 0.9 or more.

  The light of a plurality of wavelengths is, for example, the three primary colors of light constituting a projector image, blue, green, and red. Specifically, the wavelength region is blue (420 nm to 480 nm, center wavelength 450 nm), green (520 nm to 580 nm, center wavelength 550 nm), red (590 nm to 650 nm, center wavelength 620 nm). In the present embodiment, these three primary colors will be described. However, the combination, number, and wavelength region of a plurality of lights may be different depending on the projector.

The effective scattering efficiency E is a value (E) obtained by dividing the sum of the scattering cross sections of all the spherical fine particles contained per unit area of the light diffuser by the sum of the geometric cross sectional areas of all the spherical fine particles, It can be calculated if the resin (refractive index) and particles (refractive index, particle size distribution) constituting the light diffuser are determined. This value is calculated for each central wavelength in the blue, green, and red wavelength regions. When the effective scattering efficiency obtained for each wavelength is E _B , E _G , E _R , the ratio E _min / E _max between the maximum value (E _max ) and the minimum value (E _min ) is 0.90. The light diffuser of the present invention is composed of a combination of resin and particles satisfying 1 or less. By setting the ratio E _min / E _max to 0.90 or more, the color tone of the light source light is prevented from shifting when the light source is viewed through the light diffuser, and the white light source is colored when the light diffuser is passed through. You can eliminate what you see. As the ratio value (E _min / E _max ) is closer to 1, the color can be eliminated. Therefore, it is preferably 0.95 or more, more preferably 0.99 or more.

In order to set the ratio between the maximum value and the minimum value of the effective scattering efficiency E within the above-described range, for example, the following method can be used. First, a combination of particles composed of a resin and predetermined components is determined. Thereby, the refractive index of resin and particle | grains is determined. Next, with respect to particle samples having various particle size distributions and average particle sizes, the effective scattering efficiency E for each central wavelength in the blue, green, and red wavelength regions in the selected resin is determined from the refractive index and the particle size distribution. Ask for. From these results, E _min and E _max for each sample are determined, a ratio E _min / E _max is calculated, and a combination of resin and particles in which the ratio E _min / E _max falls within the above range is selected. The particle size distribution and the average particle size can be known by measuring the particle size distribution of each sample by a Coulter counter method or the like.

Next, the structure of the light diffuser of the present invention will be described with reference to the drawings.
In the light diffusing body 1 of the present invention, as shown in FIG. 1, the light diffusing layer 2 formed of a transparent resin and spherical fine particles having a refractive index different from that of the transparent resin may be a single layer. As described above, a transparent polymer film 3 or the like may be provided on at least one surface of the light diffusion layer 2. Moreover, the transparent polymer film 3 may be provided on both surfaces of the adhesive light diffusion layer 2a as shown in FIG. 3, and the transparent polymer film 3 is provided on one surface of the light diffusion layer 2 as shown in FIG. The antireflection layer 4 may be provided on the other surface.

  Since the light diffuser of the present invention utilizes internal scattering, it is preferable that the surface of the light diffuser is substantially smooth when the light diffusion layer is located on the surface. Specifically, the arithmetic average roughness (Ra) in JIS B0601: 2001 is 0.30 μm or less, preferably 0.15 μm or less.

  As the transparent resin forming the light diffuser, a resin such as a thermoplastic resin, a thermosetting resin, or an ionizing radiation curable resin can be used. Specifically, polyester resin, acrylic resin, acrylic urethane resin, polyester acrylate resin, polyurethane acrylate resin, epoxy acrylate resin, urethane resin, epoxy resin, polycarbonate resin, cellulose resin, acetal Resin, vinyl resin, polyethylene resin, polystyrene resin, polypropylene resin, polyamide resin, melamine resin, phenol resin, silicone resin, fluorine resin and the like. These resins may be used alone or in combination of two or more. Thereby, it is possible to adjust to a desired refractive index.

  Moreover, a light diffuser can be made into a sticky light diffuser by using an adhesive resin. Specific examples of the adhesive resin include resins used as known transparent adhesives such as acrylic adhesives, rubber adhesives, urethane adhesives, and silicone adhesives.

The spherical fine particles must have a refractive index different from that of the selected transparent resin. Specifically, it is preferable that the relative refractive index n _sm calculated from the above formula (6) is 0.91 <n _sm <1.09 (where n _sm ≠ 1.00).

  As such spherical fine particles, inorganic fine particles such as silica, alumina, talc, zirconia, zinc oxide and titanium dioxide can be used, and from the viewpoint of easily obtaining a spherical shape, polymethyl methacrylate resin, polystyrene resin, Organic fine particles such as polyurethane resin, benzoguanamine resin, and silicone resin are preferable.

In the present invention, as described above, since the combination of the resin and the particles is determined from the effective scattering efficiency E (ratio thereof), the particle diameter of the spherical fine particles is satisfied as long as E _min / E _max ≧ 0.90 is satisfied. The particle size distribution is not particularly limited. However, the particle diameter is preferably 50 μm or less, which is a general particle diameter for a light diffuser utilizing internal scattering. A wider particle size distribution is more preferable because fluctuations in scattering efficiency due to particle diameter can be more averaged. That is, in the graph of the scattering efficiency by the particle diameter shown in FIG. 6, the fluctuation of the scattering efficiency by the particle diameter can be averaged more in the particle having the particle size distribution width of b than in the particle of the particle diameter distribution. The variation coefficient of the particle size distribution is preferably in the range of 10% to 50%, preferably 20% or more, more preferably 30% or more. The upper limit is preferably 40% or less.

The particle content is not particularly limited as long as it satisfies E _min / E _max ≧ 0.90 in the combination of a predetermined resin and particles, but the particle content is not limited to haze or transmission of the light diffuser. Affects sex. Therefore, even if the light diffuser satisfies the above conditions, if it is preferable that the haze is high depending on the use of the light diffuser, select a high content, and if it is preferable that the haze is low, Choose a small amount.

The light diffuser described above is obtained by melting a transparent resin and forming a sheet by adding spherical fine particles to the light diffuser, or forming a spherical fine particle together with a transparent resin on a transparent polymer film or the like. It can be formed.
The transparent polymer film only needs to have a high transmittance, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polystyrene, triacetyl cellulose, acrylic, polyvinyl chloride, and cyclic olefin. A polymer film having excellent transparency is used.

The thickness of the transparent polymer film is not particularly limited as long as the light scattering property of the light diffusion layer is not inhibited.
When the antireflection layer 4 is provided on the light diffusion layer 2 as shown in FIG. 4, a spherical fine particle coated with a transparent resin may be formed on the antireflection film, or the light diffusion layer 2 may be formed. An antireflection film may be laminated on the antireflection layer 4. As the antireflection film, a known material such as an antireflection film in which layers having different refractive indexes are laminated can be used. By providing the antireflection layer, reflection of light can be prevented.

Next, the transmission screen of the present invention will be described. The transmission screen of the present invention is provided with the above-described light diffuser. Hereinafter, an embodiment of the transmission screen of the present invention will be described with reference to FIG.
A transmissive screen 7 shown in FIG. 5 includes a light diffusion layer 2 on one surface of the transparent polymer film 3 and a hard coat layer 5 on the other surface. The transparent polymer film 3 is provided. The light diffusion layer 2 is formed of a transparent resin and spherical fine particles having different refractive indexes, and the ratio between the maximum value and the minimum value of the effective scattering efficiency E calculated for each of a plurality of wavelengths is the light described above. Satisfies the diffuser requirements.

  The transparent polymer film only needs to have a high transmittance, and the same material as that used for the light diffuser of the present invention can be used. In particular, as a transmissive screen, a biaxially stretched polyethylene terephthalate film is excellent in mechanical strength and dimensional stability and can be suitably used. Moreover, what provided the easy-adhesion layer etc. suitably in these transparent polymer films is also used suitably.

  The thickness of the transparent polymer film is not particularly limited, but can be appropriately selected in consideration of handleability.

  The transmission screen of the present invention is not limited to a transparent polymer film, and a transparent material such as a plastic plate or glass can also be used.

  The light diffusing layer provided on one surface of the transparent polymer film is a light diffusing layer used in the above-mentioned light diffusing body, and is formed from transparent resin and spherical fine particles having different refractive indexes. By increasing or decreasing the amount of spherical fine particles per unit area of the spherical fine particles used in the light diffusion layer, values such as screen gain, haze, and transmittance can be adjusted.

  The hard coat layer provided on the other surface is for protecting the surface of the transparent polymer film, and has a scratch prevention property and a reflection prevention property. As a resin used for such a hard coat layer, a resin such as a thermoplastic resin, a thermosetting resin, or an ionizing radiation curable resin can be used as appropriate, but the ionizing radiation curable resin is particularly excellent in damage prevention. Preferably, these resins preferably contain a pigment or the like in order to obtain reflection preventing properties.

  As an adhesive layer for adhering a light diffusion layer and other transparent polymer film, known transparent adhesives such as commonly used acrylic adhesives, rubber adhesives, urethane adhesives, and silicone adhesives Can be used. The pressure-sensitive adhesive used preferably has the same refractive index as that of the binder resin that forms the light diffuser. For example, when an acrylic resin is used for the light diffusion layer, it is preferable to use an acrylic adhesive.

  The thickness of the pressure-sensitive adhesive layer is set to a thickness that does not hinder the transparency and can obtain appropriate pressure-sensitive adhesiveness. Specifically, the lower limit is preferably 0.5 μm or more, preferably 1 μm or more, more preferably 2 μm or more, and the upper limit is 30 μm or less, preferably 15 μm or less, more preferably 10 μm or less.

  For the hard coat layer and adhesive layer, each component and other components as necessary are blended and dissolved or dispersed in an appropriate solvent to prepare a coating solution. It can be formed by applying and drying by a known method such as a coating method, a spray coating method, an air knife coating method, etc., and then curing using a necessary curing method.

  According to the transmissive screen of the present embodiment, the color tone of the light source light is prevented from shifting when the light source is viewed through the screen, and the white light source is not colored when viewed through the screen. it can.

  In this embodiment, as the light diffuser 1, a light diffuser 1 in which a transparent polymer film is provided on one surface of the light diffusion layer 2 and a transparent polymer film is provided on the other surface via an adhesive layer is employed. Although the thing was demonstrated, what provided the hard-coat layer in the outermost surface as it is as the light diffuser as shown in FIGS. 1-4 can also be used as the transmission type screen of this invention.

  The following examples further illustrate the present invention. “Parts” and “%” are based on weight unless otherwise specified.

[Example 1]
A light diffusion layer coating solution having the following composition is applied to one surface of a transparent polymer film (Lumirror T60: Toray Industries, Inc.) having a thickness of 188 μm by bar coating, and cured by heating at 120 ° C. for 5 minutes, and light diffusion having a thickness of about 15 μm A layer was formed. Further, an ultraviolet curable acrylic pressure-sensitive adhesive (refractive index: 1.50) was applied on the light diffusion layer, dried, and a transparent polymer film was bonded to produce a light diffuser. The refractive index of the cured resin excluding fine particles having the following formulation was 1.519. Further, the particle size distribution of the styrene fine particles is measured, and the sum of the scattering cross-sections of all the spherical fine particles contained per unit area of the light diffuser is calculated from the equation (1), and the sum of the geometric cross-sectional areas of all the spherical fine particles. The value divided by (effective scattering efficiency E) was calculated for each central wavelength in the blue, green, and red wavelength regions. Further, Table 1 shows the calculated values (E) of the blue, green, and red wavelength regions, and E _min / E _max obtained from these values.

<Light diffusion layer coating solution>
・ Acrylic resin 14.25 parts
(Acridic A807: Dainippon Ink & Chemicals, Inc.)
(Solid content 50%)
・ 20 parts of styrene fine particles (Techpolymer SBX-12: Sekisui Plastics Co., Ltd.)
(Variation coefficient 36.76%, average particle size 11.3 μm, refractive index 1.59)
・ Dilute solvent 40 parts ・ Curing agent 2.79 parts (Takenate D110N: Mitsui Chemicals Polyurethanes)

[Example 2]
A light diffusing body was produced in the same manner as in Example 1 except that the light diffusion layer coating solution of Example 1 was changed to the following light diffusion layer coating solution.

<Light diffusion layer coating solution>
・ Acrylic resin 14.25 parts
(Acridic A807: Dainippon Ink & Chemicals, Inc.)
(Solid content 50%)
・ 20 parts of styrene fine particles (Techpolymer SBX-8: Sekisui Plastics Co., Ltd.)
(Variation coefficient 34.83%, average particle size 8.9 μm, refractive index 1.59)
・ Dilute solvent 40 parts ・ Curing agent 2.79 parts (Takenate D110N: Mitsui Chemicals Polyurethanes)

[Comparative Example 1]
A light diffusing body was produced in the same manner as in Example 1 except that the light diffusion layer coating solution of Example 1 was changed to the following light diffusion layer coating solution.

<Light diffusion layer coating solution>
・ Acrylic resin 14.25 parts
(Acridic A807: Dainippon Ink & Chemicals, Inc.)
(Solid content 50%)
・ 40 parts of styrene fine particles (Techpolymer SBX-6: Sekisui Plastics)
(Variation coefficient 35.41%, average particle size 6.3 μm, refractive index 1.59)
・ Diluted solvent 63 parts ・ Curing agent 2.79 parts (Takenate D110N: Mitsui Chemicals Polyurethanes)

  About the light diffuser obtained in Examples 1 and 2 and Comparative Example 1, the color when the light source from the projector was viewed from the front through the light diffuser was visually evaluated. The evaluation results are shown in Table 1.

In Examples 1 and 2, the ratio E _min / E _max between the maximum value (E _max ) and the minimum value (E _min ) of the effective scattering efficiency (E) in the blue, green, and red wavelength regions is Since each was close to 1, when the light source was viewed through the light diffuser, the color tone of the light source light was prevented from shifting, and the white light source appeared white without being colored.

In Comparative Example 1, the value of the ratio E _min / E _max is 0.872, the red light is best scattered than the other blue and green lights, and the parallel rays of the red light are the other blue. Because it was relatively less than green parallel rays, the color of the light source shifted when looking at the light source through the light diffuser, and the white light source looked a light bluish color.

  Moreover, the hard coat layer was provided on the surface opposite to the surface on which the light diffusion layer of the transparent polymer film of the light diffuser of Examples 1 and 2 was provided, and a transmission type screen was produced. The white light source viewed through these transmission screens was white without coloration.

Sectional drawing which shows one Example of the light diffusing body of this invention Sectional drawing which shows the other Example of the light diffusing body of this invention Sectional drawing which shows the other Example of the light diffusing body of this invention Sectional drawing which shows the other Example of the light diffusing body of this invention Sectional drawing which shows one Example of the transmission type screen of this invention Graph showing the relationship between particle diameter and scattering efficiency in each wavelength range

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light diffusing body 2 ... Light diffusing layer 2a ... Adhesive light diffusing layer 3 ... Transparent polymer film 4 ... Antireflection layer 5 ... Hard coat layer 6 ... Adhesive layer 7 ... Transparent screen

Claims (8)

The transparent resin and the transparent resin are light diffusers formed from spherical fine particles having different refractive indexes,
Calculated when a value obtained by dividing the sum of the scattering cross sections of all the spherical fine particles contained per unit area of the light diffuser by the sum of the geometric cross sectional areas of all the spherical fine particles is calculated for each of a plurality of wavelengths. A light diffuser characterized in that the minimum value for each wavelength is 90% or more of the maximum value. 2. The light diffuser according to claim 1, wherein a value E obtained by dividing the sum of the scattering cross-sections of all the spherical fine particles by the sum of the geometric cross-sectional areas of all the spherical fine particles is expressed by the following equation (1): A light diffuser characterized by being represented.

(In formula (1), Q is the scattering cross section of one spherical fine particle and is a function of wavelength λ and particle size r, and f (r) is a particle size distribution function.)   2. The light diffuser according to claim 1, wherein the plurality of wavelengths are center wavelengths of blue, green, and red wavelength regions. A light diffusing article of claim 1, wherein the refractive index n _m of the transparent resin, and the refractive index of the spherical particle and n _s, n _s / n _m is 0.91 <(n _s / n _m ) <1.09 (where n _s / n _m ≠ 1).   2. The light diffuser according to claim 1, wherein the surface of the light diffuser is substantially smooth. A light diffusing body comprising a light diffusing layer and a transparent polymer film laminated on at least one surface thereof, wherein the light diffusing layer comprises a transparent resin and spherical fine particles having different refractive indexes. Formed from
Calculated when a value obtained by dividing the sum of the scattering cross sections of all the spherical fine particles contained per unit area of the light diffuser by the sum of the geometric cross sectional areas of all the spherical fine particles is calculated for each of a plurality of wavelengths. A light diffuser characterized in that the minimum value for each wavelength is 90% or more of the maximum value.   A transmissive screen comprising the light diffuser according to claim 1.   A transmissive screen having a light diffusing layer on one surface of a transparent substrate, wherein the light diffusing body according to any one of claims 1 to 6 is used as the light diffusing layer.

Images