JP2020166015A - Reflective screen and projection system using it - Google Patents

Abstract

Kind Code: A1 A reflective screen is provided that has excellent transparency and suppresses changes in the color of a displayed image due to the incident angle of a light source with respect to the screen surface. The reflective screen has a selective reflection layer A and a selective reflection layer B, and the bandwidth of the spectral reflectance of light incident on the selective reflection layer A at an incident angle α degree is LA (nm), the peak value of the spectral reflectance of light incident on the selective reflection layer A at an incident angle of α degrees is PA (%), and the wavelength indicating the peak value of the selective reflection layer A is WA (nm). LB (nm) is the bandwidth of the spectral reflectance of light incident on the selective reflection layer B at an incident angle α degrees, and the peak of the spectral reflectance of light incident on the selective reflection layer B at an incident angle α degrees When the value is defined as PB (%) and the wavelength indicating the peak value of the selective reflection layer B is defined as WB (nm), the incident angle α is at least one 10 degree selected from the range of 5 to 60 degrees. It satisfies a given relationship in the width region. [Selection drawing] Fig. 1

Description

The present invention relates to a reflective screen and a projection system using the same.

As a next-generation screen, a highly transparent screen capable of projecting a highly visible image without deteriorating the visibility of the background image is expected. Applications of highly transparent screens include transparent partitions, show windows, wearable displays, head-up displays and the like. Screens are roughly classified into transparent screens that perform back projection and reflective screens that perform front projection.

As a highly transparent reflective screen, a reflective screen utilizing selective wavelength reflection of a cholesteric liquid crystal has been proposed (Patent Documents 1 and 2).

JP-A-2017-161607 Japanese Unexamined Patent Publication No. 2006-17930

The reflective screens of Patent Documents 1 and 2 have good transparency. However, the reflective screens of Patent Documents 1 and 2 have a problem that the color of the displayed image changes depending on the angle of incidence of the light source on the screen surface and the angle at which a person observes the image.

An object of the present invention is to provide a reflective screen having excellent transparency and suppressing a change in color of a displayed image due to an incident angle of a light source on a screen surface, and a projection system using the same.

That is, the present invention provides the following [1] to [3].
[1] A reflection screen, wherein the reflection screen has a selective reflection layer A and a selective reflection layer B, and the bandwidth of the spectral reflectance of light incident on the selective reflection layer A at an incident angle of α degrees is L. _{a (nm), P a (} %) of the peak value of the spectral reflectance of the light incident at an incident angle α of the selective reflection layer a, the wavelength indicating the peak value of the selective reflection layer a W _{a (nm} ) is defined to be the selective reflection layer B to the bandwidth of the spectral reflectance of the light incident at an incident angle α of L _{B (nm),} the spectral reflection of the light incident at an incident angle α of the selective reflection layer B the peak value of the rate P _{B (%),} when the wavelength indicating the peak value of the selective reflection layer B was defined as W _{B (nm),} the angle of incidence α is selected from a range of 5 to 60 degrees A reflective screen that satisfies the following equations (1) to (4) in at least one region having a width of 10 degrees.
_{W B} <W A (1)
_{L A -15nm ≦ W A -W B} ≦ L A + 15nm (2)
_{L B -15nm ≦ W A -W B} ≦ L B + 15nm (3)
_{| P A -P B | ≦ 5.0} % (4)
[2] A reflective screen, wherein the reflective screen has a selective reflective layer A and a selective reflective layer B, and the reflected light of light incident on the reflective screen at an incident angle of x degrees and x + 10 degrees on the reflective screen. When the color difference of the L ^* a ^* b ^* color system calculated from the reflected light of the light incident in is defined as ΔE ^* ab (x to x + 10),
A reflective screen satisfying the following equation (11) at at least any angle in which the incident angle x is selected from the range of 5 to 60 degrees.
ΔE ^* ab (x to x + 10) ≤ 5.0 (11)
[3] A projection system including a light source and a reflection screen according to any one of claims 1 to 5.

The reflective screen and projection system of the present invention are excellent in transparency and can suppress changes in the color of the displayed image due to the angle of incidence of the light source on the screen surface.

It is sectional drawing which shows one Embodiment of the reflection screen of this invention. The spectral reflectance of light incident on the selective reflection layer A of the reflection screen of Example 1 at an incident angle of 50 degrees (solid line of (a)), and incident on the selective reflection layer B of the reflection screen of Example 1 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Example 1 at an incident angle of 60 degrees (solid line of (b)), Example 1. It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees. The spectral reflectance (solid line of (a)) of the light incident on the selective reflection layer A of the reflection screen of Comparative Example 1 at an incident angle of 50 degrees, and the incident on the selective reflection layer B of the reflection screen of Comparative Example 1 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Comparative Example 1 at an incident angle of 60 degrees (solid line of (b)), Comparative Example 1 It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees. It is a figure which shows the spectral reflectance of the light incident on the reflection screen of Example 1 at an incident angle of 50 degrees, and the spectral reflectance of the light incident on the reflection screen of Example 1 at an incident angle of 60 degrees (50 + 10 degrees). It is a figure which shows the spectral reflectance of the light incident on the reflection screen of Comparative Example 1 at an incident angle of 50 degrees, and the spectral reflectance of the light incident on the reflection screen of Comparative Example 1 at an incident angle of 60 degrees (50 + 10 degrees). It is a figure for demonstrating the angle formed by the vibration direction of linearly polarized light emitted from a light source, and the slow axis of a retardation layer. The spectral reflectance of light incident on the selective reflection layer A of the reflection screen of Example 2 at an incident angle of 50 degrees (solid line of (a)), and incident on the selective reflection layer B of the reflection screen of Example 2 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Example 2 at an incident angle of 60 degrees (solid line of (b)), Example 2. It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees. The spectral reflectance of light incident on the selective reflection layer A of the reflection screen of Example 3 at an incident angle of 50 degrees (solid line of (a)), and incident on the selective reflection layer B of the reflection screen of Example 3 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Example 3 at an incident angle of 60 degrees (solid line of (b)), Example 3. It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees. The spectral reflectance of light incident on the selective reflection layer A of the reflection screen of Example 4 at an incident angle of 50 degrees (solid line of (a)), and incident on the selective reflection layer B of the reflection screen of Example 4 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Example 4 at an incident angle of 60 degrees (solid line of (b)), Example 4. It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees. The spectral reflectance of light incident on the selective reflection layer A of the reflection screen of Example 5 at an incident angle of 50 degrees (solid line in (a)), and incident on the selective reflection layer B of the reflection screen of Example 5 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Example 5 at an incident angle of 60 degrees (solid line of (b)), Example 5. It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees. The spectral reflectance (solid line of (a)) of the light incident on the selective reflection layer A of the reflection screen of Comparative Example 2 at an incident angle of 50 degrees, and incident on the selective reflection layer B of the reflection screen of Comparative Example 2 at an incident angle of 50 degrees. Spectral reflectance of the light (broken line of (a)), spectral reflectance of light incident on the selective reflection layer A of the reflective screen of Comparative Example 2 at an incident angle of 60 degrees (solid line of (b)), Comparative Example 2 It is a figure which shows the spectral reflectance (the broken line of (b)) of the light incident on the selective reflection layer B of a reflection screen at an incident angle of 60 degrees.

Hereinafter, embodiments of the present invention will be described.
[Reflective screen i]
The reflective screen i of the present invention has a selective reflective layer A and a selective reflective layer B.
The selective reflective layer A to the bandwidth of the spectral reflectance of the light incident at an incident angle α of L _{A (nm),} the peak value of the spectral reflectance of the light incident at an incident angle α of the selective reflection layer A P _a (%), the wavelength indicating the peak value of the selective reflection layer a is defined as _W a (nm),
The selective reflection layer B to the bandwidth of the spectral reflectance of the light incident at an incident angle α of L _{B (nm),} the peak value of the spectral reflectance of the light incident at an incident angle α of the selective reflection layer B P _B (%), when the wavelength indicating the peak value of the selective reflection layer B was defined as _W B (nm),
The following equations (1) to (4) are satisfied in at least one region having a width of 10 degrees in which the incident angle α is selected from the range of 5 to 60 degrees.
_{W B} <W A (1)
_{L A -15nm ≦ W A -W B} ≦ L A + 15nm (2)
_{L B -15nm ≦ W A -W B} ≦ L B + 15nm (3)
_{| P A -P B | ≦ 5.0} % (4)

FIG. 1 is a cross-sectional view showing an embodiment of the reflective screen i of the present invention and the reflective screen ii of the present invention described later. The reflective screen (100) of FIG. 1 has a selective reflective layer A (11) and a selective reflective layer B (12). Further, the reflection screen (100) of FIG. 1 has a selective reflection layer A (11) and a selective reflection layer B (12) between the retardation layer A (21) and the retardation layer B (22). ing. Further, the reflective screen (100) of FIG. 1 has a selective reflective layer A (11) and a selective reflective layer B (12) between the transparent substrate A (31) and the transparent substrate B (32). ing. Further, the reflective screen (100) of FIG. 1 has an adhesive layer 40 between the selective reflective layer A (11) and the selective reflective layer B (12).

As used _{herein, L A (nm), P} A (%) and _W A (nm) is intended to mean a value at the selective reflection layer A monolayer. In the present _{specification, L B (nm), P} B (%) and _W B (nm) is intended to mean a value at the selective reflection layer B monolayer.
Further, in the present specification, "light incident on XX at an incident angle of YY degrees" means "light incident on XX from a direction deviated by YY degrees from the normal direction of XX".
In the present _{specification, L A (nm), P} A (%), W A (nm), L B (nm), a light source in measuring or simulating a _P B (%) and _W B (nm) Is an unpolarized parallel ray. Further, the spectral reflectance shall include specular reflection and diffuse reflection.
Further, in the present specification, the "region having a width of 10 degrees" means a region of "x to x + 10 degrees" when the reference angle is x degrees.
Further, in the present specification, "the incident angle α satisfies" xxx "in at least one region having a width of 10 degrees selected from the range of the incident angle α of 5 to 60 degrees" means that the incident angle α is 5 to 60 degrees. It means that the condition is satisfied if "xxx" is satisfied in at least one region having a width of 10 degrees within the range of degrees, and it is not necessary to satisfy "xxx" in the other regions having a width of 10 degrees. For example, if equation (z) is satisfied with a 10-degree width of an incident angle of 50 to 60 degrees, it means that it is not necessary to satisfy "xxx" with a 10-degree width of an incident angle of 45 to 55 degrees. However, when comparing the parameters of the selective reflection layer A and the selective reflection layer B, it is assumed that the parameters are compared at the same incident angle in a region having a width of 10 degrees. For example, when the width of 10 degrees is 50 to 60 degrees, the same incident angles in the region, such as 50 degrees, 51 degrees, ..., 59 degrees, and 60 degrees, are compared. In addition, "xxx" means various conditions such as equations (1) to (4) in this specification related to the incident angle α.

In the equations (1) to (4), α is defined as "a range of 5 to 60 degrees" because it defines a general incident angle of the light source with respect to the selective reflection layer in the reflection screen. is there. Further, in the equations (1) to (4), "at least one 10 degree width" is defined that the difference in observation angle based on the difference in the height of the line of sight of a person is approximately within 10 degrees. Is taken into consideration. That is, the reflection screen satisfying the equations (1) to (4) can adjust the condition considering the difference in the height of the human line of sight (10 degrees) within the range of the incident angle of a general light source. Means.

<Equations (1) to (4)>
The reflective screen i of the present invention satisfies the equations (1) to (4), and when the incident angle of the light source with respect to the screen surface and / or the angle at which a person observes an image is different, the color of the displayed image is different. Can be suppressed from changing.
Hereinafter, the technical significance of the equations (1) to (4) will be described.

<< Equation (1) >>
Equation (1) is a wavelength exhibiting a peak value of the spectral reflectance of the selectively reflective layer A and the "W _{A (nm)",} a wavelength showing the peak value of the spectral reflectance of the selectively reflective layer B "W _B (Nm) ”is different. In short, in the equation (1), the selective reflection layer A and the selective reflection layer B have different wavelength ranges in at least one region having a width of 10 degrees in which the incident angle α is selected from the range of 5 to 60 degrees. It stipulates that light is selectively reflected.

W wavelength range of the _A and W _B can not be said sweepingly because it varies depending on the number of selective reflection layer reflecting screen has. If the number of selective reflection layer is 2 (selective reflective layer A and the selective reflection layer B), in the range of incident angle α is 5 to 60 degrees, it is preferred that the _{W A} is 600 to 800 nm, at 600~750nm More preferably, it is more preferably 600 to 700 nm. Similarly, when the number of selective reflection layer is 2 (selective reflective layer A and the selective reflection layer B), in the range of incidence angle α is 5 to 60 degrees, preferably _{W B} is 400 to 600 nm, 400 to It is more preferably 550 nm, and even more preferably 400 to 500 nm.

<< Equation (2) to Equation (4) >>
First, the expression "L _A" as used (2) shows the bandwidth of the spectral reflectance of the light incident at an incident angle α of the selective reflection layer A, has been used in equation (3) " “ _LB ” indicates the bandwidth of the spectral reflectance of the light incident on the selective reflection layer B at an incident angle of α degrees.

In the present specification, "bandwidth" means Δλ of the formula (24) described later.

FIG. 2A shows the spectral reflectance of light incident on the selective reflection layer A and the selective reflection layer B of the reflection screen of Example 1 at an incident angle of 50 degrees. In FIG. 2A, the solid line shows the spectral reflectance of the selective reflective layer A of Example 1, and the broken line shows the spectral reflectance of the selective reflective layer B of Example 1.
Further, FIG. 3A shows the spectral reflectance of light incident on the selective reflection layer A and the selective reflection layer B of the reflection screen of Comparative Example 1 at an incident angle of 50 degrees. In FIG. 3A, the solid line shows the spectral reflectance of the selective reflective layer A of Comparative Example 1, and the broken line shows the spectral reflectance of the selective reflective layer B of Comparative Example 1.
Note that FIGS. 2 (a) and 3 (a) show a sine wave passing through the selective reflection center wavelength (wavelength indicating the peak value) and the bandwidth obtained by simulation using the formulas (21) to (24) described later. It was created as a curve. Further, in FIGS. 2 (a) and 3 (a), the peak value of the spectral reflectance is such that light is incident on the soda lime glass side of the laminated body having the selective reflection layer on the soda glass having a refractive index of 1.51. It was calculated from the difference (V1-V2) between the measured value V1 of the peak value of the spectral reflectance at that time and the measured value V2 of the peak value of the spectral reflectance of the soda lime glass alone having a refractive index of 1.51.

Further, in the equation (2) and (3), W _A -W _B shows the intervals of the wavelength indicating the peak value of the spectral reflectance of the selectively reflective layer A and the selective reflective layer B.
Therefore, to satisfy the equation (2) and (3), as compared to the spacing of the wavelength indicating the peak value of the spectral reflectance of the selectively reflective layer A and the selective reflective layer B, the bandwidth L _A selective reflection layer A and bandwidth L _B selective reflection layer B indicates that it is not and too wide nor too narrow.
Then, satisfying the equation (4) indicates that the spectral reflectances of the selective reflection layer A and the selective reflection layer B are about the same.
Therefore, by satisfying the equations (2) to (4), the spectral reflectance distribution when the selective reflection layer A and the selective reflection layer B are laminated can be formed as shown in FIG. FIG. 4A is a diagram showing the spectral reflectance of light incident on the reflection screen of Example 1 at an incident angle of 50 degrees, and FIG. 4B is a diagram showing an incident angle of 60 degrees on the reflection screen of Example 1. It is a figure which shows the spectral reflectance of the incident light at (50 + 10 degrees). From the comparison between FIGS. 4 (a) and 4 (b), when the equations (2) to (4) are satisfied, the distribution shape of the spectral reflectance hardly changes even if the incident angle is shifted, in other words, the incident. It can be seen that the change in color can be suppressed even if the angle is shifted.

On the other hand, when any of the equations (2) to (4) is not satisfied, the change in the distribution shape of the spectral reflectance when the incident angle is shifted becomes large, and the change in color cannot be suppressed.
FIG. 5A is a diagram showing the spectral reflectance of light incident on the reflection screen of Comparative Example 1 at an incident angle of 50 degrees, and FIG. 5B is a diagram showing an incident angle of 60 degrees on the reflection screen of Comparative Example 1. It is a figure which shows the spectral reflectance of the incident light at (50 + 10 degrees). Reflective screen of Comparative Example _1, as compared to W A -W _B, is too narrow _{L A} and _{L B,} are those which do not satisfy the formula (2) and (3). From the comparison between FIGS. 5 (a) and 5 (b), when the equations (2) to (3) are not satisfied, the change in shape due to the spectral reflectance when the incident angle is shifted is large, in other words. It can be seen that the change in color when the incident angle is shifted cannot be suppressed.
Further, even satisfies Expression (2) and (3), if equation (4) is not _satisfied, W A (nm) or _W B (nm) spectral reflectance distribution in the vicinity of flat as shown in FIG. 4 _not, the W a (nm) or _W B (nm) shape with a peak in the vicinity. Therefore, when the incident angle is shifted, the distribution shape of the spectral reflectance changes, and the change in color cannot be suppressed.
Moreover, if compared to the _{L A} and _{L B} is _W A -W _B does not satisfy the too small formula (2) and (3), the spectral reflectance distribution does not become flat as shown in FIG. 4, _{W A} (nm) and W _{B (nm)} and for a shape having a peak wavelength around the intermediate can not suppress the change in color when shifting the angle of incidence. Further, _{if L} compared to _A and _{L B} is _W A -W _B does not satisfy the too large formula (2) and (3), the spectral reflectance distribution does not become flat as shown in FIG. 4, _{W A} (nm) and W _{B (nm)} and the wavelength in the vicinity of the intermediate is recessed in, unable to suppress the change in color when shifting the angle of incidence.

In one embodiment of the reflection screen i of the present invention, it is preferable that the above equations (1) to (4) are satisfied in all regions having an incident angle α of 40 to 60 degrees and having a width of 10 degrees. It is more preferable that the above equations (1) to (4) are satisfied in all the regions having an incident angle α selected from the range of 45 to 60 degrees and having a width of 10 degrees. The same applies to other conditions in the present specification relating to the incident angle α (for example, each equation such as equation (2-1) described later). The range of the incident angle α in the above-mentioned preferred embodiment takes into consideration the suitable arrangement relationship between the light source and the reflection screen.

One embodiment of the reflective screen i of the present invention preferably satisfies the following formula (2-1), and more preferably the following formula (2-2).
_{L A -10nm ≦ W A -W B} ≦ L A + 10nm (2-1)
_{L A -7nm ≦ W A -W B} ≦ L A + 7nm (2-2)

One embodiment of the reflective screen i of the present invention preferably satisfies the following formula (3-1), and more preferably the following formula (3-2).
_{L B -10nm ≦ W A -W B} ≦ L B + 10nm (3-1)
_{L B -7nm ≦ W A -W B} ≦ L B + 7nm (3-2)

One embodiment of the reflective screen i of the present invention preferably satisfies the following formula (4-1), and more preferably the following formula (4-2).
_{| P A -P B | ≦ 3.0} % (4-1)
_{| P A -P B | ≦ 2.0} % (4-2)

W preferred range of the difference between _A and W _B (W A _{-W B)} can not be said sweepingly because it varies depending on the number of selective reflection layer reflecting screen has.
If the number of selective reflection layer is 2 (selective reflective layer A and the selective reflection layer B) is, in the region of at least one 10-degree width angle of incidence α is selected from a range of 5 to 60 degrees, and W _A the difference between W _B preferably satisfies the following formula (5-1), it is more preferable to satisfy the following formula (5-2), more preferably satisfies the following formula (5-3).
_{100nm ≦ W A -W B ≦ 350nm} (5-1)
_{100nm ≦ W A -W B ≦ 300nm} (5-2)
_{150nm ≦ W A -W B ≦ 250nm} (5-3)

L _A and scope of L _B is different because it is not said unconditionally by the number of selective reflection layer reflecting screen has. It the case where the number of selective reflection layer is 2 (selective reflective layer A and the selective reflection layer B), in the range of incident angle α is 5 to 60 degrees, it _{L A} is 100nm or more preferably, 150 nm or more Is more preferable, and 200 nm or more is further preferable. Similarly, when the number is two selective reflection layer (selective reflective layer A and the selective reflection layer B), the range of incident angle α is 5 to 60 degrees, preferably _{L B} is 100nm or more, at 150nm or more More preferably, it is more preferably 200 nm or more.
Incidentally, in the region of at least one 10-degree width angle of incidence α is selected from a range of 5 to 60 degrees, the absolute value of the difference between L _A and L _B is preferably at 40nm or less.

An embodiment of a reflection screen i of the present invention, in the region of at least one 10-degree width angle of incidence α is selected from a range of 5 to 60 degrees, the range of P _A and P _B, respectively, 10% The above is preferable, 15% or more is more preferable, and 20% or more is further preferable. By setting _PA and P _B to 10% or more, the visibility of information such as an image projected from a light source can be improved.
The theoretical limit of P _A and P _B is 50%. Also, P _A and P _B is preferably 45% or less from the viewpoint of improving transparency, more preferably 35% or less, more preferably 30% or less.

An embodiment of a reflection screen i of the present invention, in the region of at least one 10-degree width angle of incidence α is selected from a range of 5 to 60 degrees, the spectral reflectance at a wavelength within the region of the band width L _A The average (hereinafter referred to as "the average of the spectral reflectances of the selective reflection layer A") is preferably 5 to 30%, more preferably 10 to 25%, and further preferably 15 to 20%. preferable.
By setting the average spectral reflectance of the selective reflective layer A to 5% or more, the visibility of information such as an image projected from the light source can be improved. Further, by setting the average spectral reflectance of the selective reflective layer A to 30% or less, the transparency of the reflective screen can be easily improved.

An embodiment of a reflection screen i of the present invention, in the region of at least one 10-degree width angle of incidence α is selected from a range of 5 to 60 degrees, the spectral reflectance at a wavelength within the region of the band width L _B The average (hereinafter referred to as "the average of the spectral reflectances of the selective reflection layer B") is preferably 5 to 30%, more preferably 10 to 25%, and further preferably 15 to 20%. preferable.
By setting the average spectral reflectance of the selective reflective layer B to 5% or more, the visibility of information such as an image projected from the light source can be improved. Further, by setting the average spectral reflectance of the selective reflective layer B to 30% or less, the transparency of the reflective screen can be easily improved.

In one embodiment of the reflection screen i of the present invention, the average of the spectral reflectances of the selective reflection layer A and the selective reflection in at least one region having a width of 10 degrees in which the incident angle α is selected from the range of 5 to 60 degrees. The ratio of the spectral reflectance of the layer B to the average (the average of the spectral reflectance of the selective reflective layer A / the average of the spectral reflectance of the selective reflective layer B) preferably satisfies the following formula (6-1). It is more preferable to satisfy the formula (6-2), and it is further preferable to satisfy the following formula (6-3). By satisfying the following formula (6-1) or the like, it is possible to more easily suppress the change in color when the incident angle is shifted.
| Average spectral reflectance of selective reflective layer A-Average spectral reflectance of selective reflective layer B | ≤5% (6-1)
| Average spectral reflectance of selective reflective layer A-Average spectral reflectance of selective reflective layer B | ≤4% (6-2)
| Average spectral reflectance of selective reflective layer A-Average spectral reflectance of selective reflective layer B | ≤3% (6-3)

_{L A (nm), W A} (nm), L B (nm) and _W B (nm), for example, as described below, the refractive index of the cholesteric liquid crystal layer can be adjusted by the birefringence index and the helical pitch. Also, P A _(%) and P _{B (%)} can be adjusted by the thickness (a small thickness and the reflectance of the selectively reflective layer A and the selective reflective layer B is lowered, the thickness is thick and the reflectance becomes higher tendency There is.).

<Selective reflective layer>
The selective reflection layer reflects a specific polarized light in a specific wavelength range and transmits other light. Examples of the selective reflection layer having such properties include the following (i) and (ii).
(I) A cholesteric liquid crystal layer that reflects right-handed or left-handed circularly polarized light in a specific wavelength range and transmits other light (sometimes referred to as "CLC layer" in the present specification).
(Ii) A reflective polarizing layer that reflects p-waves or s-waves in a specific wavelength range and transmits the other (sometimes referred to as "DBEF layer" in the present specification).

The reflective screen of the present invention has a selective reflection layer A and a selective reflection layer B as the selective reflection layer. The reflective screen of the present invention may have a selective reflection layer other than the selective reflection layer A and the selective reflection layer B as the selective reflection layer, but from the viewpoint of thinning and cost, the selective reflection layer may be provided. Two layers, a selective reflection layer A and a selective reflection layer B, are preferable. Further, the selective reflection layer A and the selective reflection layer B are preferably CLC layers.

<< CLC layer >>
As used herein, the CLC layer refers to a layer composed of liquid crystal molecules exhibiting cholesteric regularity. Cholesteric regularity means that the molecular axes are aligned in a certain direction on one plane, but the direction of the molecular axes shifts at a slight angle in the next plane that overlaps with it, and further shifts in the next plane. As described above, the structure is such that the angle of the molecular axis in the plane is deviated (twisted) as it sequentially passes through the planes arranged in an overlapping manner. The structure in which the direction of the molecular axis is twisted in this way is a chiral structure.

The CLC layer generally has an optical rotation selection property that separates an optical rotation component in one direction and an optical rotation component in the opposite direction based on the physical molecular arrangement. Light incident on such a liquid crystal layer along the helical axis of the planar arrangement of the liquid crystal is divided into two circular polarizations, right-handed and left-handed, one of which is transmitted and the other of which is reflected. This phenomenon is known as circular dichroism, and by appropriately selecting the turning direction in the spiral structure of the liquid crystal molecule, it is possible to selectively reflect the circular polarization having the same turning direction as the turning direction.

The maximum optical rotation polarized light reflection in this case occurs at the wavelength λ ₀ of the following equation (21). That is, λ ₀ means a wavelength indicating a peak value of spectral reflectance (sometimes referred to as “selective reflection center wavelength” in the present specification).
λ ₀ = nav · p (21)
Here, p is the helical pitch in the helical structure of the liquid crystal molecule, and nav is the average refractive index in the plane orthogonal to the helical axis.
When the angle of incidence changes, the average index of refraction is affected by Snell's law.
When incident from the air (refractive index P1 = 1.0) at an angle θ1, the incident angle θ2 in the CLC layer is given by the following equation (22).
sin (θ2) = sin (θ1) / nav (22)
Therefore, the selective reflection center wavelength λ _θ when the incident angle θ1 is calculated with respect to λ ₀ when the incident angle is 0 degrees is calculated by the following equation (23).

It should also be noted that in the case of CLC liquid crystal, the average refractive index is affected by the wavelength dispersion depending on the peak wavelength. (Note that in the case of a positively dispersed liquid crystal, the average refractive index on the long wavelength side is low.)
The wavelength bandwidth Δλ of the reflected light at this time is represented by the following equation (24).
Δλ = Δn · p (24)
Here, Δn is the birefringence value of the liquid crystal material.

The polarization separation action of the CLC layer alone will be described.
First, when unpolarized light is incident on the CLC layer, one of the right-handed or left-handed circularly polarized light components in the wavelength bandwidth Δλ centered on the wavelength λ ₀ is reflected, and the other circularly polarized light component and the other. Light (unpolarized light) in the wavelength range of is transmitted. Note that the reflected right-handed or left-handed circularly polarized light is reflected as it is without phase inversion, unlike normal reflection.
Further, when the circularly polarized light is incident on the CLC layer, if the turning direction of the circularly polarized light and the turning direction of the spiral structure of the liquid crystal molecules of the CLC layer match, the wavelength bandwidth centered on the wavelength λ ₀ Circularly polarized light in the range of Δλ is reflected, and circularly polarized light in other wavelength ranges is transmitted. Note that the reflected right-handed or left-handed circularly polarized light is reflected as it is without phase inversion, unlike normal reflection.
From the viewpoint of increasing the reflection efficiency and improving the visibility of the reflection screen, it is preferable to design the circularly polarized light so as to enter the CLC layer. More specifically, it is preferable to design so that the turning direction of the circularly polarized light and the turning direction of the spiral structure of the liquid crystal molecules of the CLC layer coincide with each other.

Examples of the CLC layer include a cured product of a curable composition containing a liquid crystal monomer or oligomer having a polymerizable group, and a layer made of a liquid liquid polymer in a glass state.
Among the above, the CLC layer is preferably a cured product of a curable composition containing a liquid crystal monomer or oligomer having a polymerizable group. This is because when the CLC layer is a cured product of the curable composition, the liquid crystal molecules can be optically immobilized in the cholesteric liquid crystal state, and the handleability is also improved.
The curable composition may be either ionizing radiation curable or thermosetting, but is preferably an ionizing radiation curable composition from the viewpoint of immobilization described above. In the present specification, the ionizing radiation means an electromagnetic wave or a charged particle beam having an energy quantum capable of polymerizing or cross-linking a molecule, and an ultraviolet ray (UV) or an electron beam (EB) is usually used. In addition, electromagnetic waves such as X-rays and γ-rays, and charged particle beams such as α-rays and ion rays can also be used.

Examples of the polymerizable group include an ethylenically unsaturated group such as a (meth) acryloyl group, a vinyl group and an allyl group, and an epoxy group and an oxetanyl group. From the viewpoint of polymerizable property, a (meth) acryloyl group or a vinyl group is preferable, and a (meth) acryloyl group is more preferable.
The liquid crystal monomer or oligomer having a polymerizable group may have at least one of the above polymerizable groups, but from the viewpoint of obtaining a CLC layer in which the liquid crystal molecules are optically fixed by three-dimensional cross-linking, it is sufficient. It is preferable to have two or more polymerizable groups, and a bifunctional liquid crystal monomer or oligomer having polymerizable groups at both ends is more preferable.

Examples of the liquid crystal monomer having a polymerizable group include liquid crystal monomers disclosed in JP-A-7-258638 and JP-A-10-508882. Examples of the liquid crystal oligomer having a polymerizable group include a cyclic organopolysiloxane compound having a cholesteric phase as disclosed in Japanese Patent Application Laid-Open No. 57-165480.

Specific examples of the liquid crystal monomer having a polymerizable group include a liquid crystal monomer having an acryloyl group at both ends represented by the following structural formula (I).

The CLC layer is more preferably a cured product of a curable composition containing a liquid crystal monomer or oligomer having a polymerizable group and a chiral agent. When the liquid crystal monomer or oligomer is formed into a liquid crystal layer at a predetermined temperature, it becomes a nematic state, but when a chiral agent is added thereto, it becomes a chiral nematic liquid crystal (that is, a cholesteric liquid crystal). Further, the helical pitch in the spiral structure of the liquid crystal molecules contained in the CLC layer can be adjusted by changing the type of the chiral agent used to change the chiral power or by changing the blending amount of the chiral agent. Therefore, the selective reflection wavelength range of the CLC layer can be adjusted.

The CLC liquid crystal layer may be made of a discotic liquid crystal. As the CLC liquid crystal layer, for example, a chiral discotic compound as described in JP-A-2000-086591 may be used, and JP-A-2000-111734 and JP-A-2000-171637 may be used. A copolymer of a non-chiral discotic liquid crystal compound and a chiral discotic compound having a polymerizable group as described in Japanese Patent Application Laid-Open No. 2000-347039 may be used.

From the viewpoint of obtaining a CLC layer in which liquid crystal molecules are optically fixed by three-dimensional cross-linking, the CLC layer is curable containing a liquid crystal monomer or oligomer having a polymerizable group and a chiral agent having a polymerizable group. It is more preferably a cured product of the composition.
The chiral agent having a polymerizable group is preferably a chiral agent having two or more polymerizable groups from the viewpoint of obtaining a CLC layer in which liquid crystal molecules are optically fixed by three-dimensional cross-linking, and is preferably at both ends. More preferably, it is a bifunctional chiral agent having a polymerizable group. Examples of the polymerizable group include an ethylenically unsaturated group such as a (meth) acryloyl group, a vinyl group and an allyl group, and an epoxy group and an oxetanyl group. From the viewpoint of polymerizable property, a (meth) acryloyl group or a vinyl group is preferable, and a (meth) acryloyl group is more preferable.

Examples of the chiral agent include chiral compounds disclosed in JP-A-7-258638 and JP-A-10-508882.
Examples of commercially available chiral agents include a chiral agent "Pariocolor (registered trademark) LC756" (manufactured by BASF) having an acryloyl group as a polymerizable group at both ends.

The amount of the chiral agent in the CLC layer is not particularly limited as long as the desired wavelength selectivity can be obtained, but the liquid crystal monomer, the liquid crystal oligomer, and the chiral in the curable composition used for forming the CLC layer are not particularly limited. When the total amount of the agents is 100 parts by mass, the blending amount of the chiral agent is usually 0.5 to 20 parts by mass, preferably 1 to 15 parts by mass, and more preferably 2 to 10 parts by mass.

The curable composition used for forming the CLC layer is preferably one that is cured by irradiation with the above-mentioned ionizing radiation. When an electron beam is used as the ionizing radiation, the accelerating voltage thereof can be appropriately selected depending on the material used and the thickness of the layer, but it is usually preferable to cure at an accelerating voltage of about 70 to 300 kV.
When ultraviolet rays are used as ionizing radiation, those containing ultraviolet rays having a wavelength of 190 to 380 nm are usually emitted. The ultraviolet source is not particularly limited, and for example, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, a carbon arc lamp, or the like is used.

When the curable composition used for forming the CLC layer is an ultraviolet curable composition, it is preferable to further contain a photopolymerization initiator. This is because the liquid crystal monomer or oligomer having a polymerizable group in the curable composition and the chiral agent having a polymerizable group can be cured by irradiation with ultraviolet rays.
Examples of the photopolymerization initiator include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzyl dimethyl ketal, benzoyl benzoate, α-acyloxime ester, thioxanthones and the like.
The above photopolymerization initiator may be used alone or in combination of two or more.
The amount of the photopolymerization initiator in the curable composition is 1 to 10% by mass as the blending amount of the photopolymerization initiator when the total amount of the liquid crystal monomer, the liquid crystal oligomer, and the chiral agent is 100 parts by mass. It is preferably parts, more preferably 2 to 8 parts by mass.

The curable composition used for forming the CLC layer is a photopolymerization accelerator, a lubricant, a plasticizer, a filler, an antistatic agent, an antiblocking agent, a cross-linking agent, and a light stabilizer as long as the effects of the present invention are not impaired. , UV absorber, antioxidant, conductive agent, refractive index adjuster, solvent and other other components may be contained.

When the material constituting the CLC layer is a liquid crystal polymer, as a specific example thereof, a polymer in which a mesogen group exhibiting liquid crystal property is introduced at the position of the main chain, the side chain, or the main chain and the side chain, or a cholesteryl group is side Examples of the polymer cholesteric liquid crystal introduced into the chain include a liquid crystal polymer disclosed in JP-A-9-133810, a liquid crystal polymer disclosed in JP-A-11-293252, and the like.
As the liquid crystal polymer, the cholesteric liquid crystal polymer itself having a chiral ability in the liquid crystal polymer itself may be used, or a mixture of the nematic liquid crystal polymer and the cholesteric liquid crystal polymer may be used. The state of such a liquid crystal polymer changes depending on the temperature. For example, when the glass transition temperature is 90 ° C. and the isotropic transition temperature is 200 ° C., the liquid crystal polymer exhibits a cholesteric liquid crystal state between 90 and 200 ° C., which is at room temperature. When cooled to, it can be solidified in a glass state while maintaining the cholesteric structure.

When the liquid crystal material constituting the CLC layer has a glass transition temperature such as a liquid crystal polymer, it is possible to control the ON / OFF of the liquid crystal by changing the temperature.

In order to adjust the selective reflection wavelength range of the incident light due to the cholesteric structure of the liquid crystal polymer, the chiral power in the liquid crystal polymer molecule may be adjusted by a known method. When a mixture of nematic liquid crystal polymer and cholesteric liquid crystal polymer is used, the mixing ratio is adjusted.

The optimum range of the thickness of the CLC layer varies depending on the liquid crystal monomer or oligomer used, the type of polymer or chiral agent, and the desired reflection wavelength range of the CLC layer, but from the viewpoint of increasing the reflectance of incident light. Is preferably 0.2 μm or more, more preferably 0.5 μm or more, still more preferably 1 μm or more.
From the viewpoint of thinning the reflective screen, the thickness of the CLC layer is preferably 100 μm or less, more preferably 80 μm or less, still more preferably 50 μm or less, still more preferably 30 μm or less, still more preferably 20 μm or less. Even more preferably, it is 10 μm or less. The thickness of the CLC layer is the thickness of each selective reflection layer.

The thickness of the CLC layer can be calculated from the average value of the values at 10 points by measuring the thickness at 10 points from the image of the cross section taken by, for example, a scanning transmission electron microscope (STEM). The accelerating voltage of STEM is preferably 10 kV to 30 kV. The magnification of STEM is preferably 1,000 to 7,000 times when the measured film thickness is on the order of microns, and preferably 50,000 to 300,000 times when the measured film thickness is on the nano order.

The method for forming the CLC layer is not particularly limited, and a known method can be used. Hereinafter, the case where the CLC layer is a cured product of the ionizing radiation curable composition containing the above-mentioned liquid crystal monomer or oligomer will be described as an example.
First, an alignment film is formed on a base material such as a glass substrate, and then ionizing radiation curing for forming a CLC layer containing a liquid crystal monomer or oligomer, a chiral agent, and other components such as a photopolymerization initiator and a solvent. The sex composition is applied, and the liquid crystal molecules (liquid crystal monomers and oligomers) are oriented by the orientation regulating force of the alignment film. Next, the liquid crystal monomer or oligomer can be three-dimensionally crosslinked by irradiating ionizing radiation in this oriented state to obtain a CLC layer which is a cured product of the curable composition.
Examples of the method for applying the curable composition include a spin coating method, a dip method, a spray method, a die coating method, a bar coating method, a roll coater method, a meniscus coater method, a flexographic printing method, a screen printing method, and a bead coater method. Various known methods such as, etc. can be mentioned.
When the curable composition contains a solvent, it is preferable to dry the curable composition at 30 to 120 ° C. for 10 to 120 seconds after applying the curable composition.

The alignment film can be produced by a conventionally known method. For example, a method of forming a polyimide film on a substrate such as a glass substrate and rubbing it; a method of forming a polymer compound to be a photoalignment film on a glass substrate and irradiating it with polarized UV (ultraviolet rays); a stretched PET A method using a (polyethylene terephthalate) film; a method of patterning using a mask; and the like can be mentioned.

When the CLC layer is made of the liquid crystal polymer described above, an alignment film is formed on a substrate such as a glass substrate in the same manner as described above, and a composition containing the liquid crystal polymer is formed on the alignment film by the above method. It is applied and the polymer is oriented by the orientation regulating force of the alignment film. The CLC layer can be obtained by cooling the liquid crystal polymer in a glass state after drying if necessary.

Further, a reflective screen having a plurality of CLC layers can be obtained by preparing a plurality of laminates having CLC layers formed on the base material and laminating these laminates via an adhesive or the like.

The CLC layer may be one that exhibits positive dispersibility or one that exhibits reverse dispersibility.
"Positive dispersibility" is a characteristic that the in-plane phase difference given to transmitted light decreases as the wavelength becomes longer. Specifically, the in-plane phase difference (Re450) at a wavelength of 450 nm and the in-plane phase difference at a wavelength of 550 nm are used. The relationship with the phase difference (Re550) is a characteristic that Re450> Re550. On the other hand, "reverse dispersibility" is a characteristic that Re450 <Re550.
In the present specification, the in-plane retardation (Re) has an in-plane refractive index in the slow axis direction as nx, an in-plane refractive index in the direction orthogonal to nx as ny, and a film thickness as d (nm). At that time, it can be expressed by the following formula.
In-plane phase difference (Re) = (nx-ny) x d

The in-plane phase difference (Re550) of the CLC layer is preferably 20 nm or less, and more preferably 10 nm or less.

Among the CLC layers which are examples of the selective reflection layer, the liquid crystal compounds exemplified above generally exhibit positive dispersibility.
Among the CLC layers, those exhibiting inverse dispersibility can be obtained by applying a liquid crystal material exhibiting inverse dispersion wavelength characteristics or a liquid crystal material having a cyclohexane structure.
Examples of the liquid crystal material exhibiting reverse dispersibility include JP-A-2010-522892, JP-A-2006-243470, JP-A-2007-243470, JP-A-2009-75494, and JP-A-2009-62508. Examples thereof include liquid crystal compounds described in Japanese Patent Application Laid-Open No. 2009-179563, Japanese Patent Application Laid-Open No. 2009-242717, Japanese Patent Application Laid-Open No. 2009-242718, Japanese Patent No. 4222360, Japanese Patent No. 4186981 and the like.
Examples of the liquid crystal material having a cyclohexane structure include JP 2001-163833, JP 2007-91612, JP 2007-91796, JP 2006-241403, JP 2006-70080, JP 2006-37005, and JP. A material prepared by imparting a polymerizable group such as an acrylate group to the molecular end of the liquid crystal material described in 2006-8928, or a material described in JP-A-2008-274204 can be applied.

<< DBEF layer >>
Examples of the DBEF layer include a multilayer optical film reflective polarizer, for example, the reflective polarizer described in US Pat. No. 5,882,774, and DBEF-D2-400 available from 3M Company. , DBEF-D4-400 and the like are exemplified.

The DBEF layer transmits light having a single polarized state and reflects the remaining light. The DBEF layer transmits one of p-wave (also called p-polarized light, polarized light whose electric field oscillates in the incident surface) or s-wave (also called s-polarized light, polarized light whose electric field oscillates perpendicular to the incident surface), and passes the other. reflect. It is also possible to select the wavelength of the polarized light component to be reflected as described later. Since polarized sunglasses are usually designed to absorb s-waves, it is preferable that the reflective screen having a DBEF layer be arranged so as to reflect p-waves.
Specifically, the DBEF layer is preferably a multi-layer laminate in which a layer A having birefringence and a layer B having substantially no birefringence are alternately laminated. For example, the total number of layers of such a multi-layer laminate can be 50-1,000. The refractive index nx _{A in} the x-axis direction of the A layer is larger than the refractive index ny _{A in the} y-axis direction (nx _A > ny _A ), and the refractive index nx _B in the x-axis direction and the refractive index ny _{B in the} y-axis direction of the B layer. Is substantially the same as (nx _B ≈ ny _B ). Therefore, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis, and the y-axis direction becomes the transmission axis. The difference in refractive index between the A layer and the B layer in the x-axis direction is preferably 0.1 to 0.4, more preferably 0.2 to 0.3. The x-axis direction corresponds to the stretching direction of the DBEF layer in the method for manufacturing the DBEF layer. If the difference in refractive index between the A layer and the B layer in the x-axis direction is large, the reflectance increases, so that the number of layers can be reduced. On the other hand, in order to increase the difference in refractive index, stronger stretching is required, so it is necessary to select materials and optimize the process, and it is thought that the Boeing phenomenon is likely to occur and productivity is likely to decrease. Be done.

The layer A is preferably composed of a material that exhibits birefringence by stretching. Representative examples of such materials include polyester naphthalenedicarboxylic acid (eg, polyethylene naphthalate), polycarbonate and acrylic resins (eg, polymethylmethacrylate). Of these, polyethylene naphthalate is preferable. The B layer is preferably composed of a material that does not substantially exhibit birefringence even when stretched. A typical example of such a material is a copolyester of naphthalenedicarboxylic acid and terephthalic acid.

The DBEF layer completely separates the p-wave and the s-wave by repeatedly using the slight difference in reflectance between the p-wave and the s-wave at the interface between the A-layer and the B-layer by forming a multilayer structure. It transmits one and reflects the other.
Further, in the DBEF layer, the wavelength and the bandwidth indicating the peak value of the spectral reflectance of the reflected polarizing component can be adjusted by adjusting the refractive index and the number of layers of each layer.

The total thickness of the DBEF layer is appropriately set according to the total number of layers included in the DBEF layer, and is usually about 10 μm to 150 μm.

The polarization separation action of the DBEF layer alone will be described.
First, when unpolarized light is incident on the DBEF layer, light having one of the polarization components of p-wave or s-wave and having a wavelength selected by the above means is reflected, and the other light is transmitted.
Further, when the linearly polarized light is incident on the DBEF layer, if the vibration direction of the linearly polarized light and the direction of the x-axis (reflection axis) match, the light having the wavelength selected by the above means is reflected. Light of the remaining wavelengths is transmitted.
From the viewpoint of increasing the reflection efficiency and improving the visibility of the reflection screen, it is preferable to design so that the linearly polarized light is incident on the DBEF layer. More specifically, it is preferable to design so that the vibration direction of the linearly polarized light and the direction of the x-axis (reflection axis) of the DBEF layer coincide with each other.

The DBEF layer can typically be made by combining coextrusion and transverse stretching. Coextrusion can be done in any suitable manner. For example, it may be a feed block system or a multi-manifold system. For example, the material forming the A layer and the material forming the B layer are extruded in the feed block, and then multi-layered using a multiplier. Such a multi-layer device is known to those skilled in the art. Next, the obtained elongated multilayer laminate is typically stretched in a direction (TD) orthogonal to the transport direction. The material (for example, polyethylene naphthalate) constituting the layer A has an increased refractive index only in the stretching direction due to the lateral stretching, and as a result, exhibits birefringence. The refractive index of the material constituting the B layer (for example, copolyester of naphthalene dicarboxylic acid and terephthalic acid) does not increase in any direction by the transverse stretching. As a result, a reflective polarizer having a reflection axis in the stretching direction (TD) and a transmission axis in the transport direction (MD) can be obtained. The stretching operation can be performed using any suitable device.

<Transparent base material>
One embodiment of the reflective screen i of the present invention preferably has a transparent substrate. The transparent base material has a role as a support when forming the selective reflection layer or the like, or a role of protecting the selective reflection layer or the like.

In one embodiment of the reflective screen i of the present invention, a transparent base material is provided on at least one of the side of the selective reflective layer A opposite to the selective reflective layer B and the side of the selective reflective layer B opposite to the selective reflective layer A. It is more preferable to have a transparent base material on the side of the selective reflection layer A opposite to the selective reflection layer B and on the side of the selective reflection layer B opposite to the selective reflection layer A.
Further, there may be a plurality of transparent substrates arranged on the side of the selective reflection layer A opposite to the selective reflection layer B and on the side of the selective reflection layer B opposite to the selective reflection layer A.

The transparent substrate may be formed from a polymer or glass. Examples of the polymer include cellulose acylate, polycarbonate polymer, polyester polymer such as polyethylene terephthalate and polyethylene naphthalate, acrylic polymer such as polymethyl methacrylate, and styrene polymer such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Etc. can be used. In addition, polyolefins such as polyethylene and polypropylene, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamides, imide polymers, sulfone polymers, and polyether sulfone polymers. , Polyether ether ketone polymer, polyphenylene sulfide polymer, vinylidene chloride polymer, vinyl alcohol polymer, vinyl butyral polymer, allylate polymer, polyoxymethylene polymer, epoxy polymer, or a mixture of these polymers. Be done.

The thickness of the transparent base material is usually about 25 to 125 μm in the case of a transparent base material formed of a polymer, and usually about 100 μm to 5 mm in the case of a transparent base material formed of glass.

<Phase difference layer>
One embodiment of the reflective screen i of the present invention may have a retardation layer. The retardation layer has a role of adjusting the viewing angle characteristic, a role of converting the light emitted from the light source, and the like. As an example of converting the light emitted from the light source, the linearly polarized light emitted from the light source is converted into a retardation layer (single layer of λ / 4 retardation layer, or λ / 2 retardation layer and λ / 4 retardation. Layer) can be converted to circularly polarized light.

One embodiment of the reflective screen i of the present invention preferably has the following configuration (1) or (2), and more preferably has the following configuration (3). In the case of the following configuration (1) or (2), it is preferable that the surface having the retardation layer is the light incident surface of the reflection screen.
(1) The retardation layer A is provided on the side of the selective reflection layer A opposite to the selective reflection layer B.
(2) The retardation layer B is provided on the side of the selective reflection layer B opposite to the selective reflection layer A.
(3) The selective reflection layer A has a retardation layer A on the opposite side of the selective reflection layer B from the selective reflection layer B, and has a retardation layer B on the opposite side of the selective reflection layer B from the selective reflection layer A.

In the above (1) and (3), when the retardation layer A and the transparent substrate are provided on the opposite side of the selective reflection layer A from the selective reflection layer B, the retardation layer A is on the opposite side to the selective reflection layer A. It is preferable to arrange a transparent base material in. Further, in the above (2) and (3), when the retardation layer B and the transparent base material are provided on the opposite side of the selection reflection layer B from the selection reflection layer A, the selection reflection layer B of the retardation layer B is different from the selection reflection layer B. It is preferable to place the transparent substrate on the opposite side.

When the selective reflection layer A and the selective reflection layer B are cholesteric liquid crystal layers, the retardation layer A and the retardation layer B have a single-layer structure of a λ / 4 retardation layer, or a λ / 4 retardation layer and λ /. A laminated structure with two retardation layers is preferable. Hereinafter, the λ / 4 retardation layer and the λ / 2 retardation layer as the retardation layer A are referred to as the λ / 4 retardation layer A and the λ / 2 retardation layer A, and λ / 4 as the retardation layer B. The retardation layer and the λ / 2 retardation layer may be referred to as the λ / 4 retardation layer B and the λ / 2 retardation layer B.
The linearly polarized light emitted from the light source is used as the retardation layer of the preferred embodiment described above (single-layer structure of λ / 4 retardation layer or laminated structure of λ / 4 retardation layer and λ / 2 retardation layer). By incident on the reflective screen from the side having the above, the linearly polarized light of the light source is converted into circularly polarized light, the reflectance of a specific wavelength can be increased, and the visibility can be improved. In this case, the angle formed by the slow axis of the retardation layer and the vibration direction of the linearly polarized light emitted from the light source is preferably any of the following (A) to (D).
In the present specification, the angle formed by the slow axis of the retardation layer and the vibration direction of linear polarization refers to an acute angle formed by both, and further, the angle is clockwise with respect to the vibration direction of linear polarization. If an acute angle is present, the acute angle is defined as positive (in the case of FIG. 6), and if the acute angle is present in the counterclockwise direction with respect to the vibration direction of linear polarization, the acute angle is defined as minus. ing.

<(A) When the retardation layer is either one of the retardation layer A and the retardation layer B, and the retardation layer has a single-layer structure of a λ / 4 retardation layer>
In this case, the angle formed by the slow axis of the λ / 4 retardation layer and the vibration direction of the linearly polarized light emitted from the light source is preferably 45 ± 10 degrees or −45 ± 10 degrees, preferably 45 ± 5. It is more preferably degree or −45 ± 5 degrees, further preferably 45 ± 3 degrees or −45 ± 3 degrees, and even more preferably 45 ± 1 degree or −45 ± 1 degree. When the above-mentioned angle is on the plus side, the linearly polarized light is converted into counterclockwise circular polarization, and when the angle is on the minus side, the linearly polarized light is converted into clockwise circularly polarized light (also (B) to (D) below). Similarly).

<(B) When the retardation layer is either one of the retardation layer A and the retardation layer B, and the retardation layer has a laminated structure of a λ / 4 retardation layer and a λ / 2 retardation layer>
In this case, the angle formed by the slow axis of the λ / 4 retardation layer and the vibration direction of the linearly polarized light emitted from the light source is preferably 75 ± 10 degrees or −75 ± 10 degrees, preferably 75 ± 5. It is more preferably degree or −75 ± 5 degrees, further preferably 75 ± 3 degrees or −75 ± 3 degrees, and even more preferably 75 ± 1 degree or −75 ± 1 degree. The angle formed by the slow axis of the λ / 2 retardation layer and the vibration direction of the linearly polarized light emitted from the light source is preferably 15 ± 10 degrees or -15 ± 10 degrees, preferably 15 ± 5 degrees. Alternatively, it is more preferably -15 ± 5 degrees, further preferably 15 ± 3 degrees or -15 ± 3 degrees, and even more preferably 15 ± 1 degree or -15 ± 1 degree. The angle formed by the slow axis of the λ / 4 retardation layer and the angle formed by the slow axis of the λ / 2 retardation layer shall be the same plus or minus (for example, of the λ / 4 retardation layer). When the angle formed by the slow axis is 75 ± 10 degrees, the angle formed by the slow axis of the λ / 2 retardation layer is 15 ± 10 degrees).

<(C) When the retardation layer is both the retardation layer A and the retardation layer B, and the retardation layer A and the retardation layer B have a single layer structure of λ / 4 retardation layer>
In this case, the angle formed by the slow axis of the λ / 4 retardation layer A and the vibration direction of the linearly polarized light emitted from the light source is preferably 45 ± 10 degrees or −45 ± 10 degrees, preferably 45 ±. It is more preferably 5 degrees or −45 ± 5 degrees, further preferably 45 ± 3 degrees or −45 ± 3 degrees, and even more preferably 45 ± 1 degree or −45 ± 1 degree. Further, it is preferable that the slow axis of the λ / 4 retardation layer B is arranged so as to be substantially orthogonal to the slow axis of the λ / 4 retardation layer A. The range of substantially orthogonality will be described later.

<(D) The retardation layer is both the retardation layer A and the retardation layer B, and the retardation layer A and the retardation layer B have a laminated structure of a λ / 4 retardation layer and a λ / 2 retardation layer. In this case, the angle formed by the slow axis of the λ / 4 retardation layer A and the vibration direction of the linearly polarized light emitted from the light source is preferably 75 ± 10 degrees or −75 ± 10 degrees. It is more preferably 75 ± 5 degrees or -75 ± 5 degrees, further preferably 75 ± 3 degrees or -75 ± 3 degrees, and even more preferably 75 ± 1 degree or -75 ± 1 degree. preferable. Further, the angle formed by the slow axis of the λ / 2 retardation layer A and the vibration direction of the linearly polarized light emitted from the light source is preferably 15 ± 10 degrees or -15 ± 10 degrees, preferably 15 ± 5. It is more preferably degree or -15 ± 5 degrees, further preferably 15 ± 3 degrees or -15 ± 3 degrees, and even more preferably 15 ± 1 degree or -15 ± 1 degree. It should be noted that the angle formed by the slow axis of the λ / 4 retardation layer A and the angle formed by the slow axis of the λ / 2 retardation layer A shall be the same plus or minus. Further, the slow axis of the λ / 4 retardation layer B is arranged so as to be substantially orthogonal to the slow axis of the λ / 4 retardation layer A, and the slow axis of the λ / 2 retardation layer B is λ /. It is preferable to arrange the two retardation layers A so as to be substantially orthogonal to the slow axis. The range of substantially orthogonality will be described later.

In the case of a laminated structure of the λ / 4 retardation layer and the λ / 2 retardation layer, it is preferable to arrange the λ / 4 retardation layer so as to be on the selective reflection layer side rather than the λ / 2 retardation layer. For example, it is preferable to arrange the λ / 4 retardation layer A on the selective reflection layer A side rather than the λ / 2 retardation layer A. Further, it is preferable to arrange the λ / 4 retardation layer B on the selective reflection layer B side rather than the λ / 2 retardation layer B.

When the selective reflection layer A and the selective reflection layer B are cholesteric liquid crystal layers and have the configuration of (C) or (D) above (hereinafter, the configuration may be referred to as "configuration x"), they correspond to each other. It is preferable to arrange the retardation layer A and the retardation layer B so that the angles formed by the slow axes of the retardation layers are substantially orthogonal to each other. For example, the angle formed by the slow axis of the λ / 4 retardation layer A and the slow axis of the λ / 4 retardation layer B, or the slow axis of the λ / 2 retardation layer A and the λ / 2 retardation layer. It is preferable to arrange the retardation layer A and the retardation layer B so that the angles formed by the slow axis of B with the slow axis are substantially orthogonal to each other. In addition, substantially orthogonal means 90 ± 10 degrees, preferably 90 ± 5 degrees, more preferably 90 ± 3 degrees, still more preferably 90 ± 1 degree.
By emitting linearly polarized light from a light source and incident on the reflection screen of the configuration x, the light converted to circularly polarized light in the retardation layer on the light incident side is converted back to linearly polarized light in the retardation layer on the light emitting side. Can be converted. Therefore, by adopting the following configuration (i) or (ii), it is possible to suppress the interfacial reflection of the reflective screen (particularly the reflection at the air interface) and improve the visibility. Considering the visibility when wearing polarized sunglasses, the configuration of (i) below is preferable (because polarized sunglasses are usually designed to absorb s-polarized light).
(I) Let the linearly polarized light that is reconverted be p-polarized light. (If the linearly polarized light emitted from the light source is p-polarized light, the linearly polarized light that is reconverted is p-polarized light.)
(Ii) A polarizer that absorbs the linearly polarized light that is reconverted is arranged on the light emitting side rather than the retardation layer on the light emitting side.

The λ / 4 retardation layer has a Re550 of preferably 100 to 180 nm, more preferably 110 to 160 nm, and even more preferably 110 to 150 nm.
The λ / 2 retardation layer has a Re550 of preferably 200 to 300 nm, more preferably 220 to 280 nm, and even more preferably 220 to 270 nm.

The retardation layer such as the λ / 4 retardation layer and the λ / 2 retardation layer may exhibit positive dispersibility or reverse dispersibility, but in the selective reflection layer, From the viewpoint of improving the efficiency of reflecting light in a specific wavelength range, those exhibiting reverse dispersibility are preferable.

The ratio of Re450 of the λ / 4 retardation layer to Re550 of the λ / 4 retardation layer (Re450 / Re550)) is preferably 0.95 or less, more preferably 0.93 or less, still more preferably 0.91. Below, it is even more preferably 0.89 or less. Further, Re450 / Re550 is preferably 0.78 or more, more preferably 0.80 or more, and further preferably 0.82 or more.

The ratio of Re450 of the λ / 2 retardation layer to Re550 of the λ / 2 retardation layer (Re450 / Re550)) is preferably 0.95 or less, more preferably 0.93 or less, still more preferably 0.91. Below, it is even more preferably 0.89 or less. Further, Re450 / Re550 is preferably 0.78 or more, more preferably 0.80 or more, and further preferably 0.82 or more.

The thickness of the retardation layer such as the λ / 4 retardation layer and the λ / 2 retardation layer can be appropriately adjusted in the range of 0.1 to 10 μm in consideration of the added retardation.

The retardation layer can be formed, for example, by forming from a composition containing a liquid crystal compound or by stretching a polymer film. The retardation layer formed from the composition containing the liquid crystal compound is preferably formed on the transparent substrate. The retardation layer formed on the transparent substrate may be used as it is, or may be transferred to another member (for example, a selective reflection layer) for use.

The type of the liquid crystal compound used for forming the retardation layer is not particularly limited. For example, a retardation layer obtained by immobilizing a low-molecular-weight liquid crystal compound in a liquid crystal state and then immobilizing it by photocrosslinking or thermal cross-linking, or a polymer liquid crystal compound in a nematic orientation in a liquid crystal state is formed and then cooled. A retardation layer obtained by immobilizing the orientation may be used.
Even when a liquid crystal compound is used for the retardation layer, it is no longer necessary to exhibit liquid crystallinity after the layer is formed. The polymerizable liquid crystal compound may be a polyfunctional polymerizable liquid crystal compound or a monofunctional polymerizable liquid crystal compound. Further, the liquid crystal compound may be a discotic liquid crystal compound or a rod-shaped liquid crystal compound.

The retardation layer can be formed, for example, by applying, drying, and curing a composition for forming a retardation layer on a transparent substrate. Further, the composition for forming a retardation layer is preferably applied on the alignment film. The composition for forming a retardation layer can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

<Other layers>
One embodiment of the reflective screen i of the present invention may have other layers.
Examples of other layers include an alignment film for facilitating the orientation of the retardation layer, an ultraviolet absorbing layer, an intermediate film, and an adhesive layer. The interlayer film is a layer formed to impart impact resistance, shatterproofness, and the like to the reflective screen i, and can be formed from, for example, polyvinyl butyral.

<Optical properties>
In one embodiment of the reflective screen i of the present invention, the total light transmittance measured in accordance with JIS K7361-1: 1997 is preferably 60% or more, more preferably 70% or more, 80. It is more preferably% or more.
Further, in one embodiment of the reflective screen i of the present invention, the haze measured in accordance with JIS K7136: 2000 is preferably 2.0% or less, and more preferably 1.0% or less.

In one embodiment of the reflection screen i of the present invention, the maximum value of the spectral reflectance of light incident on the reflection screen at an incident angle of α degrees at 420 to 640 nm is R ₁ (%), and the light is incident on the reflection screen at an incident angle of α degrees. When the minimum value of the spectral reflectance of the emitted light at 420 to 640 nm is defined as R ₂ (%), the following equation (7) is used in an arbitrary 10-degree width region where the incident angle α is within the range of 5 to 60 degrees. ) Is preferably satisfied.
R _1- R ₂ ≤ 5.0% (7)

By satisfying the above equation (7), it is possible to easily suppress a change in the color of the displayed image due to the angle of incidence of the light source on the screen surface.
R _1- R ₂ more preferably satisfies the following formula (7-1), further preferably satisfies the following formula (7-2), and further preferably satisfies the following formula (7-3).
R ₁ −R ₂ ≦ 3.0% (7-1)
R _1- R ₂ ≤ 2.0% (7-2)
R ₁ −R ₂ ≦ 1.0% (7-3)

[Reflective screen ii]
The reflective screen ii of the present invention has a selective reflective layer A and a selective reflective layer B.
The color difference of the L ^* a ^* b ^* color system calculated from the reflected light of the light incident on the reflection screen at an incident angle of x degrees and the reflected light of the light incident on the reflection screen at x + 10 degrees is ΔE. ^* When defined as ab (x to x + 10)
The following equation (11) is satisfied at least at any angle at which the incident angle x is selected from the range of 5 to 60 degrees.
ΔE ^* ab (x to x + 10) ≤ 5.0 (11)

The reflection screen ii of the present invention satisfies the above equation (11) at at least any angle in which the incident angle x is selected from the range of 5 to 60 degrees. The definition of x in the range of 5 to 60 degrees defines the general angle of incidence of the light source on the reflective screen. Further, the reason why the color difference between the incident angle x degree and the incident angle x + 10 degree is set is that the difference in the observation angle based on the difference in the height of the line of sight of a person is approximately within 10 degrees. That is, the reflective screen satisfying the equation (11) means that the condition considering the difference in the height of the human line of sight (x to x + 10 degrees) can be adjusted within the range of the incident angle of a general light source. ing.
One embodiment of the reflection screen ii of the present invention preferably satisfies the above equation (11) at all angles where the incident angle x is selected from the range of 5 to 50 degrees, and the incident angle x is 40 to 50 degrees. It is more preferable to satisfy the above formula (11) at all angles selected from the range of 45 to 50 degrees, and the above formula (11) is satisfied at all angles selected from the range of the incident angle x of 45 to 50 degrees. Is even more preferable. The same applies to the formulas (11-1) and (11-2) described later. The range of the incident angle x in the above-mentioned preferred embodiment takes into consideration the preferable arrangement relationship between the light source and the reflection screen.

ΔE ^* ab (x to x + 10) more preferably satisfies the following formula (11-1), and further preferably satisfies the following formula (11-2).
ΔE ^* ab (x to x + 10) ≤ 4.0 (11-1)
ΔE ^* ab (x to x + 10) ≤ 3.0 (11-2)

In order for the reflective screen ii to satisfy the above equation (11), it is preferable to satisfy the equations (1) to (4) which are essential constituent requirements of the reflective screen i, and as a preferable embodiment in the reflective screen i. It is more preferable to satisfy the illustrated configuration.

Further, as one embodiment of the reflective screen ii, a transparent base material, a retardation layer and other layers may be provided. As the transparent base material, the retardation layer and the other layers having as one embodiment of the reflective screen ii, the same ones as those exemplified as the embodiment of the reflective screen i can be used.

In the present specification, the light source for measuring the color difference is an unpolarized parallel ray. Further, the reflected light for which the color difference is calculated shall include specular reflection and diffuse reflection.
In this specification, the L ^* a ^* b ^* color system is standardized by the International Commission on Illumination (CIE) in 1976. The L ^* a ^* b ^* color system is adopted in JIS Z8781-4: 2013.

<Use>
The reflective screens i and ii of the present invention can be suitably used for transparent partitions, show windows, wearable displays, head-up displays and the like.

[Projection system]
The projection system of the present invention comprises a light source and the reflection screen of the present invention described above.

The reflective screen constituting the projection system of the present invention may be either the reflective screen i or ii.

The light source is not particularly limited. Examples of the light projected from the light source include non-polarized light, linearly polarized light, and circularly polarized light.
Examples of the light source capable of projecting linearly polarized light include a light source in which a polarizer is arranged on a display element such as an organic EL, and a liquid crystal projector. Examples of the light source capable of projecting circularly polarized light include a light source capable of projecting linearly polarized light with a retardation layer added.

When a light source capable of projecting linearly polarized light is used, as described above, the vibration direction of the linearly polarized light emitted from the light source, the type of selective reflection layer (CLC layer or DBEF layer), the presence or absence of a retardation layer, and the phase difference. It is preferable to appropriately arrange the light source and the reflection screen in consideration of the type of layer (single layer of λ / 4 retardation layer or lamination of λ / 4 retardation layer and λ / 2 retardation layer). ..

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples. In addition, "part" and "%" are based on mass unless otherwise specified.

[Example 1]
1. 1. Preparation and preparation of materials 1-1. Formation of alignment film and λ / 4 retardation layer A photoalignment film was applied on a transparent substrate (triacetyl cellulose film having a thickness of 60 μm) and dried to form an alignment film having a thickness of 0.2 μm.
Next, a coating solution obtained by diluting a liquid crystal material of Re450 / Re550 = 0.85 with a solvent (toluene / cyclopentanone = 7/3) to a solid content of 20% was applied onto the alignment film, dried, and dried at the λ / 4 position. A retardation layer was formed, and a laminate 1 having a transparent substrate, an alignment film, and a λ / 4 retardation layer in this order was obtained. The thickness of the λ / 4 retardation layer was adjusted so that Re (550) was 142 nm. In addition, two laminated bodies 1 were produced.

1-2. Formation of Selective Reflective Layer A chiral agent having 93.25 parts of polymerizable liquid crystal monomer and acryloyl at both ends on the λ / 4 retardation layer of one of the laminates 1 obtained in 1-1 above (Pariocolor®). ) LC756, manufactured by BASF) 6.85 parts by mass, photopolymerization initiator (IRGACURE (registered trademark) 907; 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one) 4 parts by mass Part, acrylic leveling agent (BYK-361N, manufactured by Big Chemie Japan Co., Ltd.) 0.1 part by mass was coated with cyclopentanone diluted to a solid content of 20%, and a CLC layer with a thickness of 1.0 μm ( The selective reflection layer A) was formed. As a result, a laminate 2 having a transparent base material, an alignment film, a λ / 4 retardation layer A, and a selective reflection layer A in this order was obtained.
A chiral agent having 93.25 parts of polymerizable liquid crystal monomer and acryloyl at both ends on the λ / 4 retardation layer of the other laminate 1 obtained in 1-1 above (Pariocolor (registered trademark) LC756, BASF). ) 3.84 parts by mass, photopolymerization initiator (IRGACURE (registered trademark) 907; 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one) 4 parts by mass, acrylic leveling Agent (BYK-361N, manufactured by Big Chemie Japan Co., Ltd.) 0.1 parts by mass diluted with cyclopentanone to a solid content of 20% is coated, and a CLC layer (selective reflection layer B) having a thickness of 1.2 μm is applied. Was formed. As a result, a laminate 3 having a transparent base material, an alignment film, a λ / 4 retardation layer B, and a selective reflection layer B in this order was obtained.

1-3. Fabrication of Reflective Screen The surface of the laminate 2 obtained in 1-2 above on the selective reflection layer A side and the surface of the laminate 3 obtained in 1-2 above on the selective reflection layer B side are optically formed with a thickness of 50 μm. It was bonded via an isotropic transparent pressure-sensitive adhesive layer to obtain a reflective screen of Example 1. The slow axis of the λ / 4 retardation layer A and the slow axis of the λ / 4 retardation layer B were orthogonal to each other.

[Example 2]
A reflection screen of Example 2 was obtained in the same manner as in Example 1 except that the selective reflection center wavelength of the selective reflection layer B of Example 1 was changed from 640 nm to 655 nm.

[Example 3]
A reflection screen of Example 3 was obtained in the same manner as in Example 1 except that the selective reflection center wavelength of the selective reflection layer B of Example 1 was changed from 640 nm to 665 nm.

[Example 4]
Reflection of Example 4 in the same manner as in Example 1 except that the selective reflection center wavelength of the selective reflection layer A of Example 1 was changed from 460 nm to 475 nm and the selective reflection center wavelength of the selective reflection layer B was changed from 640 nm to 620 nm. Got a screen.

[Example 5]
A reflection screen of Example 5 was obtained in the same manner as in Example 1 except that the peak value of the spectral reflectance of the selective reflection layer B of Example 1 at an incident angle of 50 degrees was changed from 25% to 30%.

[Comparative Example 1]
Reflection of Comparative Example 1 in the same manner as in Example 1 except that the selective reflection center wavelength of the selective reflection layer A of Example 1 was changed from 460 nm to 450 nm and the selective reflection center wavelength of the selective reflection layer B was changed from 640 nm to 670 nm. Got a screen.

[Comparative Example 2]
A reflective screen of Comparative Example 2 was obtained in the same manner as in Example 1 except that the peak value of the spectral reflectance at an incident angle of 50 degrees of the selective reflective layer B of Example 1 was changed from 25% to 40%.

2. Simulation calculation formula such as bandwidth by like (21) to the original in (24), the angle of incidence α is in the range of 5 to 60 _{degrees, L A (nm), W} A (nm), L B (nm), It was calculated by simulation W _B of the (nm). Further, the measured value V1 of the peak value of the spectral reflectance when light is incident from the soda lime glass side of the laminated body having the selective reflective layer A or the selective reflective layer B on the soda glass having a refractive index of 1.51 and a refractive index of 1.51 source - from the difference between the measured value V2 of the peak value of da-lime glass single spectral reflectance _(V1-V2), was calculated _P a (%) and _P B (%). Then, in a specific region having a width of 10 degrees (incident angle 50 to 60 degrees), it is determined whether or not the following equations (1) to (7-3) are satisfied, and those satisfying are "○" and those not satisfying are satisfied. It was set as "x". The results are shown in Table 1.
Further, an example at an incident angle of 50 degrees and a sine curve created as a sine curve passing through the peak value of the spectral reflectance, the selective reflection center wavelength (wavelength indicating the peak value) and the bandwidth obtained by the above simulation and the like. The distribution map of the spectral reflectance of the selective reflective layer A of the comparative example and the distribution map of the spectral reflectance of the selective reflective layer B of the examples and the comparative examples at an incident angle of 60 degrees are shown in FIGS. 2, 3, 7 to 11. Shown.
Further, in a region having an incident angle α of 10 to 20 degrees and a width of 10 degrees, it is determined whether or not the following equations (1) to (7-3) are satisfied, and those satisfying are "○" and those not satisfying are "○". × ”. The results are shown in Table 2.

_{W B} <W A (1)
_{L A -15nm ≦ W A -W B} ≦ L A + 15nm (2)
_{L A -10nm ≦ W A -W B} ≦ L A + 10nm (2-1)
_{L A - 7nm ≦ W A -W} B ≦ L A + 7nm (2-2)
_{L B -15nm ≦ W A -W B} ≦ L B + 15nm (3)
_{L B -10nm ≦ W A -W B} ≦ L B + 10nm (3-1)
_{L B - 7nm ≦ W A -W} B ≦ L B + 7nm (3-2)
_{| P A -P B | ≦ 5.0} % (4)
_{| P A -P B | ≦ 3.0} % (4-1)
_{| P A -P B | ≦ 2.0} % (4-2)
_{100nm ≦ W A -W B ≦ 350nm} (5-1)
_{100nm ≦ W A -W B ≦ 300nm} (5-2)
_{150nm ≦ W A -W B ≦ 250nm} (5-3)
| Average spectral reflectance of selective reflective layer A-Average spectral reflectance of selective reflective layer B | ≤5% (6-1)
| Average spectral reflectance of selective reflective layer A-Average spectral reflectance of selective reflective layer B | ≤4% (6-2)
| Average spectral reflectance of selective reflective layer A-Average spectral reflectance of selective reflective layer B | ≤3% (6-3)
R _1- R ₂ ≤ 5.0% (7)
R ₁ −R ₂ ≦ 3.0% (7-1)
R _1- R ₂ ≤ 2.0% (7-2)

3. 3. Calculation of color difference based on actual measurement The L ^* a ^* b ^* color system L ^* value, a ^* value, and b ^* value were calculated from the reflected light of the light incident on the reflection screen at an incident angle of x degrees. Further, the L ^* value, a ^* value, and b ^* value of the L ^* a ^* b ^* color system were calculated from the reflected light of the light incident on the reflection screen at an incident angle of x + 10 degrees. Based on the obtained values, the color difference (ΔE ^* ab (x to x + 10)) of the L ^* a ^* b ^* color system was calculated. When x was 50 degrees, it was determined whether or not the following equations (11) to (11-2) were satisfied, and those satisfying were designated as “〇” and those not satisfying were designated as “x”. The results are shown in Table 1. Further, when the incident angle x was 10 degrees, it was determined whether or not the following equations (11) to (11-2) were satisfied, and those satisfying were designated as “◯” and those not satisfying were designated as “x”. The results are shown in Table 2.
The measuring device was V-670 manufactured by JASCO Corporation, and the following measurement conditions were used.
<Measurement conditions>
Light source: Random light (unpolarized)
Incident angle: Variable from 5 to 75 degrees at 1 degree intervals Measurement wavelength range: 380 to 780 nm (measurement wavelength interval 1 nm)

ΔE ^* ab (x to x + 10) ≤ 5.0 (11)
ΔE ^* ab (x to x + 10) ≤ 4.0 (11-1)
ΔE ^* ab (x to x + 10) ≤ 3.0 (11-2)

4. Evaluation (color)
It was projected onto the reflective screens of Examples and Comparative Examples at an incident angle of 55 degrees. The projected image was compared with the sample printed matter, and it was evaluated whether or not the color of the printed matter was properly reproduced in the projected image. Five men and women with a height of 150 cm or more and less than 160 cm, with 3 points for which the color is properly reproduced, 2 points for which cannot be said, and 1 point for which the color is not properly reproduced. A total of 30 men and women with a height of 160 cm or more and less than 170 cm and 5 men and women with a height of 170 cm or more and less than 180 cm were visually evaluated from a distance of 100 cm, and the average score was calculated.
As a result, those with an average score of 2.5 or more were rated as "○", those with an average score of 1.5 or more and less than 2.5 were designated as "B", and those with an average score of less than 1.5 were designated as "x". .. The results are shown in Table 1.
Table 2 shows the results of the same evaluation as above with the incident angle set to 15 degrees.
A liquid crystal projector capable of projecting linearly polarized light was used as the light source. Further, the liquid crystal is provided under the condition that the linearly polarized light becomes circularly polarized light in the λ / 4 retardation layer and the turning direction of the circularly polarized light matches the turning direction of the spiral structure of the liquid crystal molecules of the CLC layer. A projector and a reflective screen were placed.

5. The total light transmittance (JISK7361-1: 1997) of the reflection screens of Examples and Comparative Examples was measured using a total light transmittance haze meter (HM-150, manufactured by Murakami Color Technology Research Institute). Those having a total light transmittance of 60% or more were evaluated as "○", and those having a total light transmittance of less than 60% were evaluated as "x".

From the results of Tables 1 and 2, it can be confirmed that the reflective screens of Examples 1 to 5 are excellent in transparency and can suppress the change in color of the displayed image depending on the angle of incidence of the light source on the screen surface.
Similar evaluation results were obtained when a projector capable of projecting non-polarized light was used as the projector for evaluating the color.

11: Selective reflective layer A
12: Selective reflective layer B
21: Phase difference layer A
22: Phase difference layer B
31: Transparent base material A
32: Transparent base material B
40: Adhesive layer 100: Reflective screen

Claims (7)

A reflective screen, the reflective screen having a selective reflective layer A and a selective reflective layer B.
The selective reflective layer A to the bandwidth of the spectral reflectance of the light incident at an incident angle α of L _{A (nm),} the peak value of the spectral reflectance of the light incident at an incident angle α of the selective reflection layer A P _a (%), the wavelength indicating the peak value of the selective reflection layer a is defined as _W a (nm),
The selective reflection layer B to the bandwidth of the spectral reflectance of the light incident at an incident angle α of L _{B (nm),} the peak value of the spectral reflectance of the light incident at an incident angle α of the selective reflection layer B P _B (%), when the wavelength indicating the peak value of the selective reflection layer B was defined as _W B (nm),
A reflective screen satisfying the following equations (1) to (4) in at least one region having a width of 10 degrees in which the incident angle α is selected from the range of 5 to 60 degrees.
_{W B} <W A (1)
_{L A -15nm ≦ W A -W B} ≦ L A + 15nm (2)
_{L B -15nm ≦ W A -W B} ≦ L B + 15nm (3)
_{| P A -P B | ≦ 5.0} % (4) Wherein _{P A} and the _{P B} is 10 to 45%, respectively, the reflective screen according to claim 1. The reflective screen according to claim 1 or 2, wherein the selective reflective layer A and the selective reflective layer B are cholesteric liquid crystal layers. Claims 1 to 3 have a retardation layer A on the side opposite to the selective reflection layer B of the selective reflection layer A, and have a retardation layer B on the side opposite to the selective reflection layer A of the selective reflection layer B. The reflective screen according to any one of the above. A reflective screen, the reflective screen has a selective reflection layer A and a selective reflection layer B, and the reflected light of light incident on the reflection screen at an incident angle of x degrees and incident on the reflection screen at x + 10 degrees. When the color difference of the L ^* a ^* b ^* color system calculated from the reflected light of light is defined as ΔE ^* ab (x to x + 10),
A reflective screen satisfying the following equation (11) at at least any angle at which the incident angle x is selected from the range of 5 to 60 degrees.
ΔE ^* ab (x to x + 10) ≤ 5.0 (11) A projection system including a light source and a reflective screen according to any one of claims 1 to 5. The projection system according to claim 6, wherein the light source is a light source capable of projecting linearly polarized light.