Rear projection display system

Abstract

The present invention addresses the problem of providing a rear projection display system that uses a transparent screen through which a background is visible, and that makes a projected image highly visible. The problem is solved by the present invention which includes a projector and a transparent screen. The transparent screen has a 10-30 µm thick light projection layer; the projector projects projection light such that the angle formed between the optical axis and the normal of the transparent screen is 30° or more; and the transparent screen transmits no more than 50% of light projected by the projector in the direction of the optical axis.

Description

Rear projection display system

[0001] The present invention relates to a rear-projection display system.

[0002] In recent years, a rear-projection display system has become known as one type of display system, which displays an image by projecting light projected from a projection device located on the rear side toward the front side, while also using a transparent screen that allows the background to be seen.

[0003] For example, Patent Document 1 describes a transmissive screen that transmits projected light to display an image, the transmissive screen comprising: a light-entering surface into which the projected light enters; a light-exiting surface that faces the light-entering surface and from which the projected light exits; and total reflection surfaces that are positioned between the light-entering surface and the light-exiting surface in the thickness direction of the transmissive screen, are arranged in a predetermined direction, and totally reflect at least a portion of the projected light that has entered from the light-entering surface and directs it toward the light-exiting surface, and the angle between the total reflection surface and a connecting surface formed by the light-exiting side end of a total reflection surface and the light-entering side end of an adjacent total reflection surface is an acute angle.

[0004] JP 2018-013634 A

[0005] In a rear-projection display system using a transparent screen through which the background is visible, projection light from a projection device is incident on the transparent screen at an oblique angle and projected by the transparent screen toward the direction approximately normal to the screen (front), resulting in a projected image. However, conventional rear-projection display systems using transparent screens often have insufficient visibility of the projected image. Therefore, there is a demand for the development of a rear-projection display system that provides better visibility of the projected image.

[0006] The object of the present invention is to solve the problems of the conventional technology and to provide a rear-projection display system that can improve the visibility of projected images in a rear-projection display system that uses a transparent screen through which the background can be seen.

[0007] To solve this problem, the present invention has the following configurations. [1] A rear-projection display system including a projection device that emits projection light and a transparent screen that projects the projection light emitted by the projection device in a viewing direction, wherein the transparent screen has an optical projection layer for projecting the projection light with a thickness of 10 to 30 μm, the projection device projects the projection light onto the transparent screen so that the angle between the optical axis and the normal to the transparent screen is 30° or more, and the transparent screen has a transmittance of 50% or less for the projection light in the direction of the optical axis emitted by the projection device. [2] The rear-projection display system according to [1], which includes a quarter-wave plate between the transparent screen and the projection device. [3] The rear-projection display system according to [1] or [2], wherein the transparent screen has a haze of 25% or less. [4] The rear-projection display system according to any one of [1] to [3], wherein the transparent screen has a total light transmittance of 80% or more. [5] The rear-projection display system according to any one of [1] to [4], wherein the transparent screen has at least one cholesteric liquid crystal layer as a light projection layer, and wherein the cholesteric liquid crystal layer has bright lines and dark lines derived from the cholesteric liquid crystal phase that are inclined with respect to the main surface of the cholesteric liquid crystal layer in a cross section in the thickness direction observed with a scanning electron microscope. [6] The rear-projection display system according to [5], wherein the bright lines and dark lines derived from the cholesteric liquid crystal phase are inclined at an angle of 20 to 90 degrees with respect to the main surface of the cholesteric liquid crystal layer. [7] A rear-projection display system comprising: a projection device that emits projection light; and a transparent screen that projects the projection light emitted from the projection device in an observation direction, wherein the transparent screen has an optical projection layer that projects the projection light and has a thickness of 10 to 30 μm, the projection device projects the projection light onto the transparent screen so that the angle between the optical axis and the normal to the transparent screen is 30° or more, and further, the transparent screen changes the traveling direction of 10% or more of the projection light in the optical axis direction emitted from the projection device to a direction of ±10° with respect to the normal to the transparent screen. [8] A rear-projection display system according to [7], which has a quarter-wave plate between the transparent screen and the projection device.[9] The rear-projection display system according to [7] or [8], wherein the haze of the transparent screen is 25% or less.

[10] The rear-projection display system according to any one of [7] to [9], wherein the total light transmittance of the transparent screen is 80% or more.

[11] The rear-projection display system according to any one of [7] to

[10] , wherein the transparent screen has at least one cholesteric liquid crystal layer as a light projection layer, and wherein, in a cross section observed with a scanning electron microscope, the cholesteric liquid crystal layer has bright lines and dark lines derived from the cholesteric liquid crystal phase that are inclined with respect to the main surface of the cholesteric liquid crystal layer.

[12] The rear-projection display system according to

[11] , wherein the bright lines and dark lines derived from the cholesteric liquid crystal phase are inclined at an angle of 20 to 90° with respect to the main surface of the cholesteric liquid crystal layer.

[0008] According to the present invention, a rear-projection display system using a transparent screen through which the background is visible is provided, which provides good visibility of the projected image.

[0009] FIG. 1 is a diagram conceptually illustrating an example of a first embodiment of a rear-projection display system of the present invention. FIG. 2 is a conceptual diagram for explaining the first embodiment of the rear-projection display system of the present invention. FIG. 3 is a diagram conceptually illustrating an example of a cholesteric liquid crystal layer of a transparent screen. FIG. 4 is a plan view of the cholesteric liquid crystal layer shown in FIG. 3. FIG. 5 is a diagram conceptually illustrating a cross-sectional SEM image of the cholesteric liquid crystal layer shown in FIG. 3. FIG. 6 is a schematic diagram for explaining a method for manufacturing the cholesteric liquid crystal layer shown in FIG. 3. FIG. 7 is a diagram conceptually illustrating an example of a light diffusion layer included in the rear-projection display system of the present invention. FIG. 8 is a diagram conceptually illustrating an example of a second embodiment of the rear-projection display system of the present invention. FIG. 9 is a conceptual diagram for explaining the second embodiment of the rear-projection display system of the present invention.

[0010] The rear-projection display system of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. Furthermore, the drawings shown below are conceptual diagrams for explaining the present invention, and the size, thickness, positional relationship, etc. of each component and part do not necessarily correspond to the actual objects.

[0011] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. In this specification, "(meth)acrylate" is a notation that represents both acrylate and methacrylate, "(meth)acryloyl group" is a notation that represents both acryloyl group and methacryloyl group, and "(meth)acrylic" is a notation that represents both acrylic and methacrylic. In this specification, terms such as "same" include the error range generally accepted in the technical field. In this specification, terms such as "same" regarding angles mean that the difference from the exact angle is within a range of less than 5°, unless otherwise specified. The difference from the exact angle is preferably less than 4°, and more preferably less than 3°.

[0012] Furthermore, the rear-projection display system of the present invention can be used for various purposes, including the display of various projected images. For example, it is preferable to project images onto windows of public facilities, various buildings, vehicles, etc. Specifically, it is particularly suitable for displaying projected images onto store windows and vehicle windows (cars, buses, trains, etc.).

[0013] FIG. 1 conceptually illustrates an example of a rear-projection display system of the present invention. This rear-projection display system 100 is a first embodiment of the rear-projection display system of the present invention. The rear-projection display system 100 shown in FIG. 1 includes a projection device 110 and a transparent screen 102. In the example shown in FIG. 1, the transparent screen 102 has a configuration in which a light projection layer 10 is laminated on a support 106. In the following description, for convenience, the side from which a projected image is observed by an observer U will be referred to as the front side, and the opposite side will be referred to as the back side. Therefore, the main surface of the transparent screen 102 facing the observer U is the front side, and the main surface facing the projection device 110 is the back side. Note that the "main surface" refers to the largest surface of a sheet-like object (such as a film, plate-like object, or layer) and typically refers to both sides in the thickness direction.

[0014] The projection device 110 is disposed on the rear surface 103 side of the transparent screen 102. The projection device 110 emits projection light (image light, projection light) and projects the projection light from the rear surface 103 side onto the transparent screen 102. As shown in FIG. 1 , the projection device 110 projects the projection light obliquely onto the rear surface 103 of the transparent screen 102.

[0015] The transparent screen 102 changes the traveling direction (optical path) of the projection light irradiated onto the rear surface 103 side to a direction approximately normal to the front surface 104 side as indicated by arrow I1, thereby projecting the projection light in a viewing direction by the observer U and allowing the observer U to view the projected image. Note that the normal is a direction perpendicular to a surface, and in the case of the transparent screen 102, it is a direction perpendicular to the main surface of the transparent screen 102. In addition, in the present invention, the "approximately normal direction" also includes the "normal direction." In other words, the transparent screen 102 changes the traveling direction of the projection light irradiated onto the rear surface 103 side to a direction approximately in front of the transparent screen 102 as indicated by arrow I1, thereby projecting the projection light in a viewing direction by the observer U and allowing the observer U to view the projected image. In the following description, the projection light, indicated by arrow I1, whose traveling direction is changed by the transparent screen 102 and which is viewed as a projected image by the observer U, is also referred to as projected light I1.

[0016] 1, the transparent screen 102 has a light projection layer 10 and a support 106 that supports the light projection layer 10. In the transparent screen 102, the light projection layer 10 changes the traveling direction of the projection light that is incident from an oblique direction to a direction approximately normal to the transparent screen 102 (surface 104). Examples of the light projection layer 10 include a light scattering layer containing light scattering particles and a cholesteric liquid crystal layer. The light projection layer 10 will be described in detail later.

[0017] In such a rear-projection display system 100, the projection device 110 irradiates projection light onto the transparent screen 102 from the back surface 103 side, allowing the observer U to view from the front surface 104 side, and also making the scenery (background) on the back surface 103 side of the transparent screen 102 visible.

[0018] The same applies to the second embodiment of the rear-projection display system of the present invention shown in FIG. 8, which will be described later.

[0019] In the rear-projection display system 100 of the present invention, the light projection layer 10 of the transparent screen 102, which displays the image projected by the projection device 110, has a thickness of 10 to 30 μm. The projection device 110 projects projection light onto the transparent screen 102 from an oblique direction so that the angle θ between the optical axis shown by the dashed line in Fig. 1 and the normal to the transparent screen shown by the broken line in Fig. 1 is 30° or more. The optical axis of the projection device 110 is the optical axis (center) of the light projected by the projection device 110.

[0020] Furthermore, in the rear-projection display system 100 of the present invention, the transparent screen 102 has a transmittance of 50% or less in the optical axis direction of the projection light emitted by the projection device 110. Specifically, as conceptually shown on the right side of Figure 2, in the rear-projection display system 100, the tristimulus values ​​(X, Y, Z) of straight-transmitted light I, which is projected by the projection device 110 and transmitted straight through the transparent screen 102 without being changed in direction by the projection device 110, are measured by a measuring device 112 on the optical axis (dashed dotted line) of the projection device 110. Also, as conceptually shown on the left side of Figure 2, the transparent screen 102 is removed from the rear-projection display system 100, and the tristimulus values ​​(X, Y, Z) of projection light I, emitted by the projection device 110, are measured by a measuring device 112 on the optical axis of the projection device 110 in exactly the same manner as the measurement on the right side. The transparent screen 102 of the rear-projection display system 100 of the present invention has a transmittance of 50% or less for each stimulus value, calculated using the tristimulus values ​​(X2, Y2, Z2) of the light I2 transmitted straight through the transparent screen 102 and the tristimulus values ​​(X0, Y0, Z0) of the projected light I0 that does not pass through the transparent screen 102, measured on the optical axis of the projection device 110 in this manner: (X2 / X0) x 100 = X transmittance [%] (Y2 / Y0) x 100 = Y transmittance [%] (Z2 / Z0) x 100 = Z transmittance [%] Hereinafter, the X transmittance, Y transmittance, and Z transmittance of the transparent screen 102 on the optical axis of the projection device 110, measured in this manner, will be referred to simply as the "transparent screen transmittance."

[0021] By adopting such a configuration, the present invention realizes a rear-projection display system that provides good visibility of projected images.

[0022] As mentioned above, in a rear-projection display system using a transparent screen through which the background is visible, the transparent screen has high optical transparency. Therefore, as shown by the straight-transmitted light I2 indicated by the arrow I2 in Figure 1, a portion of the projected light projected by the projection device travels straight through the transparent screen without being changed to a direction approximately normal to the screen. If this straight-transmitted light I2 (through-hole light) is visible to the viewer U, it will be obscured by the projected light I1, which is directed in a direction approximately normal to the screen, resulting in poor visibility.

[0023] In contrast, in the rear-projection display system 100 of the present invention, the transparent screen 102 has a transmittance of 50% or less of the projection light in the optical axis direction of the projection light emitted by the projection device 110. That is, the rear-projection display system 100 of the present invention has a low transmittance of the straight-transmitted light I2, which travels straight and passes through the transparent screen 102 without being changed in its direction of travel. Therefore, the rear-projection display system 100 of the present invention can reduce the amount (brightness) of the straight-transmitted light I2, thereby preventing the straight-transmitted light I2 from being perceived by the observer U, thereby improving the visibility of the projected image. Additionally, in the rear-projection display system 100 of the present invention, the projection device 110 directs the projection light onto the transparent screen 102 so that the angle θ between the normal to the transparent screen 102 (dashed line) and the optical axis of the projection device 110 (dotted line) is 30° or greater. Therefore, in the present invention, the straight-traveling transmitted light I2, which passes through the transparent screen 102 without being changed in its traveling direction, is less likely to be visible to the observer U. This configuration prevents the straight-traveling transmitted light I2 from being obscured by the projected light I1 directed in a substantially normal direction by the transparent screen 102, thereby further improving visibility.

[0024] Furthermore, the transparent screen 102 of the rear-projection display system 100 of the present invention changes the direction of travel of the projection light and projects the projection image I1 observed by the observer U, and the thickness of the light projection layer 10 is 10 to 30 μm. Therefore, the rear-projection display system 100 of the present invention has good background visibility, and not only does it provide good background visibility when no projection image is being projected, but it also allows the background to be clearly seen when a projection image is being projected.

[0025] In the rear-projection display system 100 of the present invention, as described above, the transmittance of the transparent screen 102 on the optical axis of the projection device 110 is 50% or less, calculated from the tristimulus values ​​(X, Y, Z) of the straight-transmitted light I that travels straight through and is transmitted through the transparent screen 102 and the tristimulus values ​​(X, Y, Z) of the projected light that does not travel through the transparent screen 102. If the transmittance of the transparent screen 102 exceeds 50%, the straight-transmitted light I is easily visible to the observer U, resulting in problems such as an insufficient improvement in the visibility of the projected image and a deterioration in the visibility of the projected image due to the straight-transmitted light I reflected by the walls and ceiling. The transmittance of the transparent screen 102 is preferably 47.5% or less, and more preferably 45% or less.

[0026] In terms of visibility of the projected image, the lower the transmittance of the transparent screen 102, the better. However, taking into consideration the visibility of the background, it is preferable that the transmittance of the transparent screen 102 on the optical axis of the projection device 110 be 20% or more.

[0027] In the present invention, the transmittance of the transparent screen 102 may be measured at 5 nm intervals across the entire wavelength range of the projection light projected by the projection device 110, for example. For example, if the projection device 110 emits green light in the wavelength range of 495 to 570 nm, i.e., projects a green image, the transmittance of the transparent screen 102 is measured at 5 nm intervals from 495 nm to 570 nm. Furthermore, if the projection device 110 emits light in the visible light region in the wavelength range of 380 to 780 nm, i.e., projects a full-color image, the transmittance of the transparent screen 102 is measured at 5 nm intervals from 380 nm to 780 nm. The transmittance (tristimulus values) may be measured using, for example, a spectroradiometer.

[0028] In the rear-projection display system 100 of the present invention, the transmittance of the transparent screen 102 may be the average value of the transmittances measured at each wavelength. However, taking into consideration the color balance of the projected image and the suppression of background coloring, the transmittance of the transparent screen 102 in the present invention is preferably 50% or less in tristimulus values ​​(X, Y, Z) when displaying white, and more preferably the transmittances of the tristimulus values ​​(X, Y, Z) are the same.

[0029] 1, in the rear-projection display system 100 of the present invention, the angle θ formed between the optical axis (dash-dotted line) of the projection device 110 and the normal line (dashed line) of the transparent screen 102 is 30° or greater. If this angle θ is less than 30°, problems occur, such as the straight-transmitted light I2 being easily visible to the observer U and the reflection of the straight-transmitted light I2 deteriorating the visibility of the projected image. The angle θ is preferably 35° or greater, and more preferably 40° or greater.

[0030] It is also preferable to set the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen 102 to 45 to 65°, i.e., close to the Brewster angle (56°). In this case, it is more preferable for the projection device 110 to emit P-polarized projection light. This reduces the amount of projection light reflected by the rear surface 103 of the transparent screen 102, improving the utilization efficiency of the projection light emitted by the projection device 110. Furthermore, reducing the amount of projection light reflected by the rear surface 103 of the transparent screen 102 prevents this reflected light from being observed by the viewer U, improving the visibility of the projected image.

[0031] The angle θ should be 30° or greater, but if the angle θ is too large, depending on the type of projection device 110 and / or transparent screen 102, it may be impossible to properly project the projected image, or the reflection from the back surface of the transparent screen 102 may become too large, and this reflected light may be reflected by the walls and ceiling, thereby reducing the visibility of the projected image. Taking this into consideration, the angle θ is preferably 60° or less, and more preferably 57.5° or less.

[0032] In the illustrated rear-projection display system 100, the projection device 110 emits projection light from above at an angle of 30 degrees or more with respect to the normal to the transparent screen 102. However, the present invention is not limited to this, and projection light may also be emitted from below at an angle of 30 degrees or more with respect to the normal to the transparent screen 102.

[0033] In the rear-projection display system 100 of the present invention, the transparent screen 102 has a light projection layer 10 that projects the projection light in the observation direction and has a thickness of 10 to 30 μm. That is, in the rear-projection display system 100 of the present invention, the light projection layer 10 that changes the traveling direction of the projection light that is incident at an angle of 30° or more with respect to the normal to the transparent screen 102 to a direction approximately normal to the transparent screen 102 has a thickness of 10 to 30 μm.

[0034] If the thickness of the light projection layer 10 is less than 10 μm, the projection light incident on the transparent screen 102 cannot be sufficiently directed in a direction approximately normal to the transparent screen 102, the transmittance of the transparent screen becomes high, and the visibility of the projected image becomes poor due to the influence of the straight-through transmitted light I2. If the thickness of the light projection layer exceeds 30 μm, the transparency of the transparent screen 102, i.e., the visibility of the background, becomes poor, and the resolution of the projected image becomes poor, resulting in poor visibility. The thickness of the light projection layer 10 of the transparent screen 102 is preferably 10 to 27.5 μm, more preferably 10 to 26 μm, and even more preferably 12 to 26 μm.

[0035] In the rear-projection display system 100 of the present invention, the haze of the transparent screen 102 is not limited, but is preferably 25% or less. By setting the haze of the transparent screen 102 to 25% or less, the light transmittance of the transparent screen 102 can be improved, thereby improving the visibility of the projected image, improving the visibility of the background, and achieving a balance between the visibility of the projected image and the background. The haze of the transparent screen 102 is more preferably 22.5% or less, and even more preferably 20% or less.

[0036] In the present invention, "haze" may be measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. Theoretically, haze means a value represented by the following formula: (scattered transmittance of natural light from 380 to 780 nm) / (scattered transmittance of natural light from 380 to 780 nm + direct transmittance of natural light) × 100% Scattered transmittance is a value that can be calculated by subtracting direct transmittance from omnidirectional transmittance obtained using a spectrophotometer and an integrating sphere unit. Direct transmittance is the transmittance at 0° when based on values ​​measured using an integrating sphere unit. In other words, low haze means that the amount of direct transmitted light is high out of the total amount of transmitted light.

[0037] Furthermore, although there are no limitations on the light transmittance of the transparent screen 102, it is preferable that the total light transmittance be 80% or more. By setting the total light transmittance of the transparent screen 102 to 80% or more, it is possible to achieve both visibility of the projected image and visibility of the background, which is preferable. The total light transmittance of the transparent screen 102 is more preferably 82.5% or more, and even more preferably 85% or more. The total light transmittance of the transparent screen may be measured using a spectrophotometer or the like in accordance with JIS K 7361.

[0038] As described above, the rear-projection display system of the present invention includes the projection device 110 and the transparent screen 102. The transparent screen 102 also includes the support 106 and the light projection layer 10. The light projection layer 10 is a layer that changes the traveling direction of the projection light emitted by the projection device 110 to a direction approximately normal to the transparent screen 102 and displays a projected image that is observed by the observer U as projection light I1. In other words, the light projection layer 10 is a layer that tilts the optical path of the projection light emitted by the projection device 110 to a direction approximately normal to the transparent screen 102 to form the projection light I1.

[0039] In the rear-projection display system 100 of the present invention, there are no limitations on the projection device 110, and various known projection devices (display systems, projectors) used in rear-projection display systems, etc., can be used. One example of a projection device is a projection device having a display and a projection lens.

[0040] In the rear-projection display system of the present invention, there are no limitations on the display, and various known displays used in, for example, AR glasses, can be used. Examples of displays include liquid crystal displays, organic electroluminescence displays, and scanning displays using DLP (Digital Light Processing) and MEMS (Micro Electro Mechanical Systems) mirrors. In the present invention, liquid crystal displays include LCOS (Liquid Crystal On Silicon) displays.

[0041] When the rear projection display system is configured to display a multicolor image, a display that displays a multicolor image is used.

[0042] In the projection device used in the rear-projection display system of the present invention, the projection lens is also a known projection lens used in rear-projection display systems and the like.

[0043] As described above, the transparent screen 102 projects projection light obliquely onto the rear surface thereof in a direction approximately normal to the front surface thereof. In the rear-projection display system of the present invention, there are no limitations on the transparent screen, and various known transparent screens used in rear-projection display systems and the like can be used.

[0044] As shown in FIG. 1, the transparent screen 102 includes a support 106 and a light projection layer 10 that changes the direction of projection light emitted by a projection device 110 to a substantially normal direction to display a projected image.

[0045] The support 106 can be made of various sheet-like materials (films, plates) as long as they can support the light projection layer 10. It is preferable that the support has high transparency. Specifically, the support 106 preferably has a total light transmittance of 50% or more, more preferably 70% or more, and even more preferably 85% or more.

[0046] There are no limitations on the thickness of the support, and it is sufficient to set a thickness that can support the light projection layer depending on the material forming the support, etc. The thickness of the support is preferably 1 to 2000 μm, more preferably 3 to 500 μm, and even more preferably 5 to 250 μm.

[0047] The support may be a single layer or a multilayer. Examples of the single layer support include supports made of resins such as glass, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, and polyolefin. Alternatively, a glass substrate may be used as the support. Examples of the multilayer support include a substrate containing any of the above-mentioned single layer supports, with another layer provided on the surface of this substrate.

[0048] The support may be the same as the support used when forming the light projection layer, or the light projection layer may be formed on a separate temporary support and then transferred onto the support.

[0049] As described above, the light projection layer 10 changes the direction of projection light incident from an oblique direction, where the angle θ between the optical axis (dash line) and the normal to the transparent screen 102 (dashed line) is 30° or greater, to a direction approximately normal to the transparent screen 102, i.e., approximately forward. The light projection layer 10 can be any light projection layer used in various known transparent screens, as long as it has a thickness of 10 to 30 μm and exhibits this function. Examples of light projection layers include light-scattering layers containing light-scattering particles and cholesteric liquid crystal layers. Among these, cholesteric liquid crystal layers are preferably used because they are 10 to 30 μm thick and can effectively change the direction of projection light incident from an oblique direction, where the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen 102 is 30° or greater, to a direction approximately normal to the transparent screen 102.

[0050] The cholesteric liquid crystal layer is formed by fixing a cholesteric liquid crystal phase. Here, the cholesteric liquid crystal layer used as the light projection layer 10 is such that, when observed in a cross section perpendicular to the main surface of the cholesteric liquid crystal layer using a scanning electron microscope (SEM), bright lines (bright areas) and dark lines (dark areas) resulting from the cholesteric liquid crystal phase are inclined with respect to the main surface of the cholesteric liquid crystal layer.

[0051] Fig. 3 is a diagram conceptually showing an example of the orientation state of liquid crystal compounds in a cholesteric liquid crystal layer used as a light projection layer. Fig. 4 is a schematic plan view of the cholesteric liquid crystal layer shown in Fig. 3. Fig. 5 is a diagram conceptually showing a cross-sectional SEM image of the cholesteric liquid crystal layer shown in Fig. 3, observed with an SEM in a cross section perpendicular to the main surface.

[0052] 3 to 5, the direction X and the direction Y indicate the orientations of two coordinate axes that are orthogonal to each other on the principal surface of the cholesteric liquid crystal layer. The direction Z is perpendicular to the principal surface of the cholesteric liquid crystal layer. FIGS. 3 and 5 are views of the X-Z plane, and the direction perpendicular to the paper surface is the Y direction. FIG. 4 is a view of the X-Y plane, and the direction perpendicular to the paper surface is the Z direction. In FIG. 1, the transparent screen 102 is disposed so that the direction Z corresponds to the left-right direction in the figure.

[0053] The cholesteric liquid crystal layer 10a is a layer formed by fixing a cholesteric liquid crystal phase in which a liquid crystal compound 40 is cholesterically aligned. The examples shown in Figures 3 and 4 are examples in which the liquid crystal compound is a rod-shaped liquid crystal compound. In the present invention, it is sufficient for the cholesteric liquid crystal layer to retain the optical properties of the cholesteric liquid crystal phase within the layer, and the liquid crystal compound in the layer does not need to exhibit liquid crystallinity.

[0054] 3, the cholesteric liquid crystal layer 10a contains liquid crystal compounds 40. The liquid crystal compounds 40 are aligned in a helical manner along a helical axis C1. That is, the cholesteric liquid crystal layer 10a has a helical structure in which the liquid crystal compounds 40 are stacked in a helical manner, and the helical structure in which the liquid crystal compounds 40 are stacked in a helical manner by one rotation (360° rotation) is defined as one helical pitch.

[0055] The helical axis C1 is perpendicular to the optical axis 40A of the liquid crystal compound 40. The helical axis C1 is inclined with respect to the normal to each of the two principal surfaces of the cholesteric liquid crystal layer 10a. A region in which the optical axis 40A is parallel to the observation direction is observed as a dark line in the cross-sectional SEM image. A region in which the optical axis 40A is perpendicular to the observation direction is observed as a bright line in the cross-sectional SEM image. In this description, the observation direction refers to a direction perpendicular to the observation surface. Furthermore, "parallel" includes a position close to parallel. Furthermore, "perpendicular" includes a position close to perpendicular.

[0056] Therefore, as shown in Fig. 5, when the X-Z plane of the cholesteric liquid crystal layer 10a is observed with an SEM, a striped pattern is observed in which bright lines 42 and dark lines 44 are alternately arranged and the bright lines 42 and dark lines 44 are inclined at a predetermined angle β with respect to the normal to the main surface (X-Y plane). Note that two bright lines 42 and two dark lines 44 in Fig. 5 correspond to one pitch of the spiral, i.e., one winding of the spiral.

[0057] As shown in Figure 4, the liquid crystal compounds 40 observed on the major surface of the cholesteric liquid crystal layer 10a are aligned along one of the in-plane directions of the cholesteric liquid crystal layer 10a. That is, the liquid crystal compounds 40 observed on the major surface of the cholesteric liquid crystal layer 10a are aligned along one of the in-plane directions of the cholesteric liquid crystal layer 10a, the direction of the alignment axis D1. Furthermore, on each alignment axis D1, the direction of the optical axis 40A of the liquid crystal compounds 40 changes while continuously rotating in one in-plane direction along the alignment axis D1. Here, for the sake of explanation, it is assumed that the alignment axis D1 is oriented in the X direction. Furthermore, in the Y direction, the liquid crystal compounds 40 having the same optical axis 40A are aligned at equal intervals.

[0058] The expression "the orientation of the optical axis 40A of the liquid crystal compound 40 changes while continuously rotating in the direction of the alignment axis D1" specifically means that the angle formed between the optical axis 40A of the liquid crystal compound 40 aligned along the direction of the alignment axis D1 and the direction of the alignment axis D1 varies depending on the position in the direction of the alignment axis D1, and the angle formed between the optical axis 40A and the direction of the alignment axis D1 changes sequentially along the direction of the alignment axis D1 from θ to θ+180° or θ-180°. The difference in angle between the optical axes 40A of the liquid crystal compounds 40 adjacent to each other in the direction of the alignment axis D1 is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0059] In the present invention, the liquid crystal compounds 40 are assumed to rotate in a direction such that the angle formed by the optical axes 40A of the liquid crystal compounds 40 adjacent to each other along the alignment axis D decreases. Therefore, in the cholesteric liquid crystal layer 10a shown in Figure 4, the optical axes 40A of the liquid crystal compounds 40 rotate leftward (counterclockwise) along the direction of the arrow of the alignment axis D.

[0060] On the other hand, the liquid crystal compound 40 forming the cholesteric liquid crystal layer 10a has the same orientation of the optical axis 40A in the Y direction perpendicular to the direction of the alignment axis D, i.e., the Y direction perpendicular to the direction in which the optical axis 40A continuously rotates. In other words, the liquid crystal compound 40 forming the cholesteric liquid crystal layer 10a has the same angle between the optical axis 40A of the liquid crystal compound 40 and the direction of the alignment axis D in the Y direction.

[0061] In the cholesteric liquid crystal layer, the surfaces along the bright and dark lines substantially coincide with the reflective surfaces. Therefore, in the present invention, the cholesteric liquid crystal layer 10a has a reflective surface that is inclined with respect to the principal surface of the cholesteric liquid crystal layer 10a. Therefore, in the rear-projection display system 100 of the present invention, light incident on the transparent screen 102 (cholesteric liquid crystal layer 10a) is specularly reflected by the reflective surface of the cholesteric liquid crystal layer 10a and non-specularly reflected by the principal surface of the transparent screen 102, with the angle of incidence and the angle of reflection being different. As a result, the transparent screen 102 having the above-described cholesteric liquid crystal layer 10a as a light projection layer can emit light that is obliquely incident on the rear surface of the transparent screen 102 in a direction substantially normal to the front surface (a direction substantially perpendicular to the principal surface).

[0062] Here, the bright lines 42 and dark lines 44 of the cholesteric liquid crystal layer 10a are preferably inclined at an angle of 20 to 90 degrees with respect to the major surface of the cholesteric liquid crystal layer 10a. That is, as shown in FIG. 5, the angle β formed between the major surface of the cholesteric liquid crystal layer 10a and the bright lines 42 and dark lines 44 of the cholesteric liquid crystal layer 10a is preferably 20 to 90 degrees. By setting the angle β within this range, even when the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen 102 is 30 degrees or greater and the thickness of the light projection layer 10 is as thin as 10 to 30 μm, light incident obliquely on the rear surface of the transparent screen 102 can be suitably emitted in a direction approximately normal to the front surface. The angle β is more preferably 35 to 87.5 degrees, and even more preferably 50 to 85 degrees.

[0063] Furthermore, when a cholesteric liquid crystal layer 10a is used as the light projection layer 10, the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen is preferably 30 to 60°, and more preferably 35 to 57.5°. When a cholesteric liquid crystal layer 10a is used as the light projection layer 10, setting the angle θ to 30 to 60° is preferable in that light that is obliquely incident on the back surface of the transparent screen 102 can be properly emitted in the normal direction to the front surface, and linear transmitted light can be reduced.

[0064] Furthermore, when the above-described cholesteric liquid crystal layer 10a is used as the light projection layer 10, a larger amount of light incident obliquely on the rear surface of the transparent screen 102 can be emitted in a direction approximately normal to the front surface side, compared to when the light scattering layer 10b described below is used. Therefore, the cholesteric liquid crystal layer 10a can be made thinner and more transparent than the light scattering layer 10b described below. In other words, by using the cholesteric liquid crystal layer 10a as the light projection layer 10, the thickness of the light projection layer 10 can be suitably set to 10 to 30 μm, as described above.

[0065] When the cholesteric liquid crystal layer 10a is used as the light projection layer 10, the transparent screen 102 may have one cholesteric liquid crystal layer 10a or multiple cholesteric liquid crystal layers 10a with different selective reflection wavelengths. For example, when the projection device projects a full-color image of RGB, the light projection layer 10 may have a cholesteric liquid crystal layer that selectively reflects red light, a cholesteric liquid crystal layer that selectively reflects green light, and a cholesteric liquid crystal layer that selectively reflects blue light.

[0066] Furthermore, when the above-described cholesteric liquid crystal layer 10a is used as the light projection layer 10, the transparent screen 102 may have cholesteric liquid crystal layers 10a with different circular polarization selectivities. That is, the transparent screen 102 may have a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized light and a cholesteric liquid crystal layer that selectively reflects left-handed circularly polarized light. For example, the transparent screen 102 may have a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized red light, a cholesteric liquid crystal layer that selectively reflects left-handed circularly polarized red light, a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized green light, a cholesteric liquid crystal layer that selectively reflects left-handed green light, a cholesteric liquid crystal layer that selectively reflects right-handed circularly polarized blue light, and a cholesteric liquid crystal layer that selectively reflects left-handed blue light.

[0067] Furthermore, when the above-described cholesteric liquid crystal layer 10a is used as the light projection layer 10, the transparent screen 102 may have an alignment film between the support 106 and the cholesteric liquid crystal layer 10a. The alignment film will be described later.

[0068] Such a cholesteric liquid crystal layer 10a can be manufactured, for example, as follows: Note that the manufacturing method of the cholesteric liquid crystal layer that serves as the light projection layer 10 of the transparent screen 102 used in the present invention is not limited to the method described below, as long as it is a method that can manufacture a cholesteric liquid crystal layer in which bright and dark lines observed in a cross-sectional SEM image perpendicular to the main surface of the cholesteric liquid crystal layer are inclined with respect to the main surface of the cholesteric liquid crystal layer.

[0069] The above-described method for producing a cholesteric liquid crystal layer preferably includes a step of applying a composition containing a liquid crystal compound and a chiral agent onto a support (temporary support) (hereinafter also referred to as "step (A)"), and a step of applying shear force to the surface of the composition applied onto the support (hereinafter also referred to as "step (B)"). A cholesteric liquid crystal layer can be formed on the support through steps (A) and (B). Applying shear force to the composition containing a liquid crystal compound and a chiral agent in step (B) can form a cholesteric liquid crystal layer in which the bright and dark lines observed in a cross-sectional SEM image are inclined relative to the main surface of the cholesteric liquid crystal layer. Furthermore, by repeating steps (A) and (B), multiple cholesteric liquid crystals can be formed on the support. Each step will be described in detail below.

[0070] (Step (A)) In step (A), a composition containing a liquid crystal compound and a chiral agent is applied onto a support. "Applying a composition onto a support" is not limited to directly contacting the composition with the support, but also includes contacting the composition with the support via an optional layer. The optional layer may be one of the components of the support, or may be a layer formed on the support before the application of the composition. An example of the optional layer is an alignment film for aligning the liquid crystal compound. A method for forming an alignment film will be described later.

[0071] -Support- Examples of the support used in step (A) include the support described above for support 106. Preferred aspects of the support used in step (A) are the same as those of the support described above for support 106. An alignment film may be provided in advance on the surface of the support used in step (A).

[0072] Liquid Crystal Compound As the liquid crystal compound contained in the composition, for example, a known liquid crystal compound that forms a cholesteric liquid crystal can be used. The composition may contain one type of liquid crystal compound alone, or two or more types of liquid crystal compounds.

[0073] The liquid crystal compound may have a polymerizable group. The liquid crystal compound may have one type of polymerizable group alone or two or more types of polymerizable groups. The liquid crystal compound may have two or more polymerizable groups of the same type. When the liquid crystal compound has a polymerizable group, the liquid crystal compound can be polymerized. By polymerizing the liquid crystal compound, the stability of the cholesteric liquid crystal can be improved.

[0074] Examples of the polymerizable group include a group having an ethylenically unsaturated double bond, a cyclic ether group, and a nitrogen-containing heterocyclic group capable of undergoing a ring-opening reaction.

[0075] Examples of the group having an ethylenically unsaturated double bond include an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, a vinyl group, a vinylphenyl group, and an allyl group.

[0076] Examples of the cyclic ether group include an epoxy group and an oxetanyl group.

[0077] An example of a nitrogen-containing heterocyclic group capable of undergoing a ring-opening reaction is an aziridinyl group.

[0078] The polymerizable group is preferably at least one selected from the group consisting of a group having an ethylenically unsaturated double bond and a cyclic ether group. Specifically, the polymerizable group is preferably at least one selected from the group consisting of an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, a vinyl group, a vinylphenyl group, an allyl group, an epoxy group, an oxetanyl group, and an aziridinyl group, more preferably at least one selected from the group consisting of an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group, and particularly preferably at least one selected from the group consisting of an acryloyloxy group and a methacryloyloxy group.

[0079] Liquid crystal compounds are classified into, for example, rod-shaped liquid crystal compounds and discotic liquid crystal compounds according to their chemical structures. Rod-shaped liquid crystal compounds are known as liquid crystal compounds having a rod-shaped chemical structure. As the rod-shaped liquid crystal compound, for example, known rod-shaped liquid crystal compounds can be used. As the discotic liquid crystal compound, for example, known discotic liquid crystal compounds can be used.

[0080] From the viewpoint of adjusting the optical properties (particularly the light diffraction properties) of the cholesteric liquid crystal layer, the liquid crystal compound is preferably a rod-shaped liquid crystal compound, more preferably a rod-shaped thermotropic liquid crystal compound.

[0081] A rod-shaped thermotropic liquid crystal compound is a compound that has a rod-shaped chemical structure and exhibits liquid crystallinity in a specific temperature range. As the rod-shaped thermotropic liquid crystal compound, for example, a known rod-shaped thermotropic liquid crystal compound can be used.

[0082] Examples of rod-shaped thermotropic liquid crystal compounds include those described in "Makromol. Chem., Vol. 190, p. 2255 (1989)" and "Advanced Materials 5, p. 107 (1993)", U.S. Pat. No. 4,683,327, U.S. Pat. No. 5,622,648, U.S. Pat. No. 5,770,107, WO 95 / 22586, WO 95 / 24455, WO 97 / 00600, WO 98 / 23580, WO 98 / 52905, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-T-11-513019, JP-A-11-80081, JP-A-2001-328973, and compounds described in JP-A-2007-279688 are exemplified. Examples of rod-shaped thermotropic liquid crystal compounds include the liquid crystal compounds represented by general formula 1 in JP-A-2016-81035 and the compounds represented by general formula (I) or general formula (II) in JP-A-2007-279688.

[0083] The rod-shaped thermotropic liquid crystal compound is preferably a compound represented by the following general formula (1):

[0084]

[0085] In general formula (1), Q 1 and Q 2 each independently represents a polymerizable group; L 1 , L 2 , L 3 , and L 4 each independently represents a single bond or a divalent linking group; A 1 , and A 2 each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and M represents a mesogenic group.

[0086] In general formula (1), Q 1 and Q 2 Examples of the polymerizable group represented by Q include the polymerizable groups described above. 1 and Q 2 The preferred embodiments of the polymerizable group represented by the formula (I) are the same as those of the polymerizable group described above.

[0087] In general formula (1), L 1 , L 2 , L 3 and L 4 The divalent linking group represented by the formula (I) is preferably a divalent linking group selected from the group consisting of -O-, -S-, -CO-, -NR-, -CO-O-, -O-CO-O-, -CO-NR-, -NR-CO-, -O-CO-, -O-CO-NR-, -NR-CO-O-, and NR-CO-NR-. R in the divalent linking group above represents an alkyl group having 1 to 7 carbon atoms or a hydrogen atom.

[0088] In general formula (1), L 3 and L 4 At least one of these is preferably —O—CO—O—.

[0089] In general formula (1), Q 1 -L 1 - and Q 2 -L 2 Each - is preferably independently any of CH2=CH-CO-O-, CH2=C(CH3)-CO-O-, and CH2=C(Cl)-CO-O-, and more preferably CH2=CH-CO-O-.

[0090] In general formula (1), A 1 and A 2 The divalent hydrocarbon group having 2 to 20 carbon atoms represented by the formula (I) is preferably an alkylene group having 2 to 12 carbon atoms, an alkenylene group having 2 to 12 carbon atoms, or an alkynylene group having 2 to 12 carbon atoms, and more preferably an alkylene group having 2 to 12 carbon atoms. The divalent hydrocarbon group is preferably linear. The divalent hydrocarbon group may contain non-adjacent oxygen atoms or non-adjacent sulfur atoms. The divalent hydrocarbon group may have a substituent. Examples of the substituent include halogen atoms (e.g., fluorine, chlorine, and bromine), a cyano group, a methyl group, and an ethyl group.

[0091] In general formula (1), the mesogenic group represented by M is a group that forms the main skeleton of the liquid crystal compound, which contributes to the formation of liquid crystals. For the mesogenic group represented by M, reference can be made to the description in "FlussigeKristalle in Tabellen II" (VEB Deutsche Verlag fur Grundstoff Industrie, Leipzig, published in 1984) (particularly pages 7 to 16) and the description in "Liquid Crystal Handbook" (edited by the Liquid Crystal Handbook Editorial Committee, Maruzen, published in 2000) (particularly Chapter 3).

[0092] Specific examples of the structure of the mesogenic group represented by M in general formula (1) include the structures described in paragraph

[0086] of JP-A No. 2007-279688.

[0093] In general formula (1), the mesogenic group represented by M is preferably a group containing at least one cyclic structure selected from the group consisting of an aromatic hydrocarbon group, a heterocyclic group, and an alicyclic hydrocarbon group, and more preferably a group containing an aromatic hydrocarbon group.

[0094] In general formula (1), the mesogenic group represented by M is preferably a group containing 2 to 5 aromatic hydrocarbon groups, and more preferably a group containing 3 to 5 aromatic hydrocarbon groups.

[0095] In general formula (1), the mesogenic group represented by M preferably contains 3 to 5 phenylene groups, and the phenylene groups are linked to each other via --CO--O--.

[0096] In general formula (1), the cyclic structure (e.g., aromatic hydrocarbon group, heterocyclic group, and alicyclic hydrocarbon group) contained in the mesogen group represented by M may have a substituent. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms (e.g., a methyl group).

[0097] Specific examples of compounds represented by general formula (1) are shown below. However, the compounds represented by general formula (1) are not limited to the compounds shown below. In the chemical structures of the compounds shown below, "-Me" represents a methyl group.

[0098]

[0099]

[0100] Specific examples of the rod-shaped thermotropic liquid crystal compound are shown below: However, the rod-shaped thermotropic liquid crystal compound is not limited to the compounds shown below.

[0101]

[0102] The liquid crystal compound may be a synthetic product synthesized by a known method or a commercially available product, such as those available from Tokyo Chemical Industry Co., Ltd. and Merck.

[0103] From the viewpoint of heat resistance, the content of the liquid crystal compound is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to the total mass of the cholesteric liquid crystal layer. There is no upper limit to the content of the liquid crystal compound. The content of the liquid crystal compound may be determined to be 100% by mass or less, relative to the total mass of the cholesteric liquid crystal layer. When the cholesteric liquid crystal layer contains components other than the liquid crystal compound, the content of the liquid crystal compound may be determined to be less than 100% by mass (preferably 98% by mass or less or 95% by mass or less), relative to the total mass of the cholesteric liquid crystal layer. The content of the liquid crystal compound is preferably 70% by mass or more and less than 100% by mass, more preferably 80% by mass or more and less than 100% by mass, and even more preferably 90% by mass or more and less than 100% by mass, relative to the total mass of the cholesteric liquid crystal layer.

[0104] The content of the liquid crystal compound in the composition is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the solid mass of the composition. The upper limit of the content of the liquid crystal compound may be determined depending on the content of components other than the liquid crystal compound. The content of the liquid crystal compound may be determined within a range of less than 100% by mass (preferably 98% by mass or less, or 95% by mass or less), based on the solid mass of the composition.

[0105] - Chiral Dopant - The composition for forming a cholesteric liquid crystal layer contains a chiral dopant.

[0106] The type of chiral agent is not limited. For example, known chiral agents (for example, chiral agents described in "Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agents for TN and STN, p. 199, edited by the 42nd Committee of the Japan Society for the Promotion of Science, 1989") can be used.

[0107] Many chiral agents contain an asymmetric carbon atom. However, chiral agents are not limited to compounds containing an asymmetric carbon atom. Examples of chiral agents include axially asymmetric compounds and planar asymmetric compounds that do not contain an asymmetric carbon atom. Examples of axially asymmetric compounds or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. For example, a polymer having a constitutional unit derived from the chiral agent and a constitutional unit derived from the liquid crystal compound can be obtained by reacting a chiral agent having a polymerizable group with a liquid crystal compound having a polymerizable group.

[0108] Examples of the polymerizable group in the chiral agent include the polymerizable groups exemplified in the description of the liquid crystal compound described above. Preferred embodiments of the polymerizable group in the chiral agent are the same as the polymerizable groups exemplified in the description of the liquid crystal compound described above. The type of the polymerizable group in the chiral agent is preferably the same as the type of the polymerizable group in the liquid crystal compound.

[0109] Examples of chiral agents exhibiting strong twisting power include those described in JP 2010-181852 A, JP 2003-287623 A, JP 2002-080851 A, JP 2002-080478 A, and JP 2002-302487 A. For the isosorbide compounds described in the above-mentioned documents, isomannide compounds having a corresponding structure can also be used as the chiral agent. Furthermore, for the isomannide compounds described in the above-mentioned documents, isosorbide compounds having a corresponding structure can also be used as the chiral agent.

[0110] The content of the chiral agent is preferably 0.1 to 20.0 mass %, more preferably 0.2 to 15.0 mass %, and even more preferably 0.5 to 10.0 mass %, based on the mass of the solid content of the composition.

[0111] -Other Components- The composition may contain components other than the above-described components. In the following description, components other than the above-described components are also referred to as "other components." Examples of other components include a solvent, an alignment regulator, a polymerization initiator, a leveling agent, an alignment aid, and a sensitizer.

[0112] The solvent is preferably an organic solvent. Examples of the organic solvent include amide solvents (e.g., N,N-dimethylformamide), sulfoxide solvents (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbon solvents (e.g., benzene and hexane), alkyl halide solvents (e.g., chloroform and dichloromethane), ester solvents (e.g., methyl acetate and butyl acetate), ketone solvents (e.g., acetone, methyl ethyl ketone, and cyclohexanone), and ether solvents (e.g., tetrahydrofuran and 1,2-dimethoxyethane). The organic solvent is preferably at least one selected from the group consisting of alkyl halide solvents and ketone solvents, and more preferably a ketone solvent.

[0113] The composition may contain one or more solvents.

[0114] The solid content in the composition is preferably from 25 to 40% by mass, more preferably from 25 to 35% by mass, based on the total mass of the composition.

[0115] Examples of the alignment regulator include the compounds described in paragraphs

[0012] to

[0030] of JP-A No. 2012-211306, the compounds described in paragraphs

[0037] to

[0044] of JP-A No. 2012-101999, the fluorine-containing (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of JP-A No. 2007-272185, and the compounds described in detail, together with their synthesis methods, in JP-A No. 2005-099258. Also, a polymer described in JP-A No. 2004-331812 containing polymerized units of a fluoroaliphatic group-containing monomer in an amount of more than 50% by mass of all polymerized units may be used as the alignment regulator.

[0116] The alignment control agent may also be a vertical alignment agent, such as the boronic acid compounds and / or onium salts described in JP-A-2015-38598 and the onium salts described in JP-A-2008-26730.

[0117] When the composition contains an alignment-regulating agent, the content of the alignment-regulating agent is preferably more than 0% by mass and not more than 5.0% by mass, more preferably 0.3 to 2.0% by mass, based on the solid mass of the composition.

[0118] Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator.

[0119] The polymerization initiator is preferably a photopolymerization initiator from the viewpoint of suppressing deformation of the support due to heat and deterioration of the composition. Examples of the photopolymerization initiator include α-carbonyl compounds (e.g., compounds described in U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (e.g., compounds described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (e.g., compounds described in U.S. Pat. No. 2,722,512), polynuclear quinone compounds (e.g., compounds described in U.S. Pat. Nos. 3,046,127 and 2,951,758), and combinations of triarylimidazole dimers and p-aminophenyl ketones (e.g., U.S. Pat. No. 3,549,366). No. 7), acridine compounds (for example, compounds described in JP-A-60-105667 and U.S. Pat. No. 4,239,850), phenazine compounds (for example, compounds described in JP-A-60-105667 and U.S. Pat. No. 4,239,850), oxadiazole compounds (for example, compounds described in U.S. Pat. No. 4,212,970), and acylphosphine oxide compounds (for example, compounds described in JP-B-63-40799, JP-B-5-29234, JP-A-10-95788, and JP-A-10-29997).

[0120] When the composition contains a polymerization initiator, the content of the polymerization initiator is preferably 0.5 to 5.0 mass %, more preferably 1.0 to 4.0 mass %, based on the mass of the solid content of the composition.

[0121] -Method for preparing the composition- The method for preparing the composition is not limited. For example, the method for preparing the composition includes a method of mixing the above-mentioned components. Any known mixing method can be used as the mixing method. In the method for preparing the composition, after mixing the above-mentioned components, the resulting mixture may be filtered.

[0122] - Coating Method - The method for coating the composition is not limited, and examples of the composition coating method include extrusion die coater method, curtain coating method, dip coating method, spin coating method, print coating method, spray coating method, slot coating method, roll coating method, slide coating method, blade coating method, gravure coating method, and wire bar method.

[0123] The amount of the composition to be applied is not limited and may be determined appropriately depending on, for example, the desired thickness of the cholesteric liquid crystal layer and the thickness of the composition before the shear force described in the section "Step (B)" below is applied.

[0124] (Step (B)) In step (B), a shear force is applied to the surface of the applied composition.

[0125] - Means for Applying Shear Force - Examples of means for applying shear force include a blade, an air knife, a bar, and an applicator. In step (B), it is preferable to apply shear force to the surface of the composition using a blade or an air knife, and it is more preferable to apply shear force to the surface of the composition using a blade.

[0126] In the method of applying shear force to the surface of the composition using a blade, it is preferable to scrape off the surface of the composition with the blade. In the above method, the thickness of the composition may change before and after the application of shear force. The thickness of the composition after the application of shear force by the blade may be 1 / 2 or less or 1 / 3 or less of the thickness of the composition before the application of shear force. The thickness of the composition after the application of shear force by the blade is preferably 1 / 4 or more of the thickness of the composition before the application of shear force.

[0127] The material of the blade is not limited, and examples of the material of the blade include metal (e.g., stainless steel), resin (e.g., Teflon (registered trademark) and polyetheretherketone (PEEK)), etc.

[0128] The shape of the blade is not limited, and may be, for example, a plate shape.

[0129] The blade is preferably a metal plate-like member, from the viewpoint of easily applying shear force to the composition.

[0130] The thickness of the tip of the blade that comes into contact with the composition is preferably 0.1 mm or more, more preferably 1 mm or more, from the viewpoint of easily applying shear force to the composition. There is no upper limit to the blade thickness. The blade thickness may be determined, for example, in the range of 10 mm or less.

[0131] In the method of applying shear force to the surface of the composition using an air knife, compressed air is blown onto the surface of the composition with an air knife, thereby applying shear force to the surface of the composition. The shear rate applied to the composition can be adjusted depending on the blowing speed of the compressed air. The blowing speed of the compressed air is the flow rate of the compressed air.

[0132] The direction in which compressed air is blown by the air knife may be the same as or opposite to the conveying direction of the composition, but is preferably the same as the conveying direction of the composition, from the viewpoint of preventing fragments of the composition scraped off by the compressed air from adhering to the composition remaining on the support.

[0133] -Shear Rate- The higher the shear rate in step (B), the higher the alignment precision of the cholesteric liquid crystal layer that can be formed. -1 Preferably, it is 10,000 seconds or more. -1 More preferably, it is 30,000 seconds or more. -1 The upper limit of the shear rate is not particularly limited. The shear rate is, for example, 1.0 × 10 6 seconds -1 It may be determined within the following range.

[0134] The method for determining the shear rate will be described below. For example, when shear force is applied using a blade, the shear rate can be determined by "V / d" where "d" is the shortest distance between the blade and the support, and "V" is the conveying speed of the composition contacting the blade (i.e., the relative speed between the composition and the blade). Furthermore, when shear force is applied using an air knife, the shear rate can be determined by "V / 2h" where "h" is the thickness of the composition after shear force is applied, and "V" is the relative speed between the surface of the composition and the surface of the support.

[0135] -Surface temperature of composition- The surface temperature of the composition when shear force is applied may be determined according to the phase transition temperature of the liquid crystal compound contained in the composition. The surface temperature of the composition when shear force is applied is preferably 50 to 120°C, more preferably 60 to 100°C. By adjusting the surface temperature of the composition within the above range, a cholesteric liquid crystal layer with high alignment precision can be obtained. The surface temperature of the composition is measured using a radiation thermometer whose emissivity is calibrated using the temperature value measured with a non-contact thermometer. The surface temperature of the composition is measured when there is no reflective object within 10 cm of the surface opposite the surface to be measured.

[0136] - Thickness of Composition - From the viewpoint of forming a cholesteric liquid crystal layer with high alignment precision, the thickness of the composition before shear force is preferably 30 μm or less, and more preferably 15 to 25 μm.

[0137] From the viewpoint of forming a cholesteric liquid crystal layer with high alignment accuracy, the thickness of the composition after the shear force is applied is preferably 10 μm or less, more preferably 7 μm or less. There is no lower limit to the thickness of the composition after the shear force is applied. The thickness of the composition after the shear force is applied is preferably 5 μm or more.

[0138] (Step (C)) When the composition contains a solvent, the method for producing a cholesteric liquid crystal layer preferably includes, between steps (A) and (B), a step of adjusting the content of the solvent in the applied composition to a range of 50% by mass or less relative to the total mass of the composition. In the following description, this step of adjusting the solvent content is also referred to as "step (C)." By adjusting the content of the solvent in the composition to a range of 50% by mass or less, a cholesteric liquid crystal layer with high alignment precision can be formed.

[0139] In step (C), the content of the solvent in the composition is preferably 40% by mass or less, more preferably 30% by mass or less, relative to the total mass of the composition. There is no lower limit for the content of the solvent in the applied composition. The content of the solvent in the applied composition may be 0% by mass or more, relative to the total mass of the composition. The content of the solvent in the applied composition is preferably 10% by mass or more, from the viewpoint of easily suppressing deterioration of the surface condition of the applied composition.

[0140] The solvent content in the composition is measured by the bone dry method. The specific procedure of the measurement method is explained below. A sample taken from the composition is dried at 60°C for 24 hours, and then the change in mass of the sample before and after drying is determined. The solvent content in the sample is determined based on the change in mass of the sample before and after drying. The above operation is performed three times, and the arithmetic average of the values ​​obtained is taken as the solvent content. The change in mass of the sample before and after drying is the difference between the mass of the sample after drying and the mass of the sample before drying.

[0141] In the step (C), the method for adjusting the content of the solvent in the applied composition includes, for example, drying.

[0142] The composition can be dried using known drying means, such as an oven, a hot air blower, or an infrared heater.

[0143] In drying using a hot air blower, the hot air may be blown directly onto the composition, or onto the surface of the support opposite to the surface on which the composition is placed. A diffusion plate may also be installed to prevent the surface of the composition from flowing due to the hot air.

[0144] Drying may be performed by suction. For example, a vacuum chamber equipped with an exhaust mechanism may be used for drying by suction. By suctioning the gas surrounding the composition, the solvent content in the composition can be reduced.

[0145] The drying conditions are not limited as long as the solvent content in the composition can be reduced to 50% by mass or less, and may be determined depending on, for example, the components contained in the composition, the amount of the composition to be applied, the conveying speed, etc.

[0146] (Step (D)) When the composition contains a polymerizable compound (for example, a liquid crystal compound having a polymerizable group and / or a chiral agent having a polymerizable group), the method for producing a cholesteric liquid crystal layer preferably includes, after step (B), a step of curing the composition to which shear force has been applied. In the following description, this curing step is also referred to as "step (D)." By curing the composition in step (D), the molecular alignment of the liquid crystal compound can be fixed.

[0147] Methods for curing the composition include, for example, heating and irradiation with active energy rays, etc. In step (D), from the viewpoint of production suitability, it is preferable to cure the composition by irradiating the composition to which a shear force has been applied with active energy rays.

[0148] Examples of active energy rays include α rays, γ rays, X-rays, ultraviolet rays, infrared rays, visible light, and electron beams. From the viewpoints of curing sensitivity and ease of equipment availability, ultraviolet rays are preferred as the active energy rays.

[0149] Examples of ultraviolet light sources include lamps, lasers, light-emitting diodes, and cathode ray tubes. Examples of lamps include tungsten lamps, halogen lamps, xenon lamps, xenon flash lamps, mercury lamps, mercury-xenon lamps, and carbon arc lamps. Examples of lasers include semiconductor lasers, helium-neon lasers, argon ion lasers, helium-cadmium lasers, and YAG (yttrium aluminum garnet) lasers.

[0150] The peak wavelength of the ultraviolet light emitted from the ultraviolet light source is preferably 200 to 400 nm.

[0151] The exposure dose of ultraviolet light is 100 to 500 mJ / cm 2 In the following description, the amount of exposure to ultraviolet light is also referred to as the "integrated amount of light."

[0152] (Other Steps) The method for producing a cholesteric liquid crystal layer may include steps other than the steps described above. The method for producing a cholesteric liquid crystal layer may include, for example, a step of forming an alignment film on a support. The step of forming an alignment film on a support is preferably performed before step (A).

[0153] The alignment film can be formed by, for example, rubbing an organic compound, oblique deposition of an inorganic compound, or forming a layer having microgrooves. The organic compound to be rubbed is preferably a polymer.

[0154] -Alignment Film- The alignment film may be any film that can impart an alignment control force to the liquid crystal compound.

[0155] The alignment film is preferably disposed between the support and the cholesteric liquid crystal layer.

[0156] The alignment film may be, for example, a known alignment film having a function of providing an alignment control force to a liquid crystal compound. The alignment film may be an alignment film that generates an alignment function by applying an electric field, a magnetic field, or light irradiation.

[0157] The thickness of the alignment film is preferably 0.1 to 10 μm, more preferably 1 to 5 μm.

[0158] (Manufacturing Method) The manufacturing method of the cholesteric liquid crystal layer may be carried out by a roll-to-roll method. In the roll-to-roll method, for example, each step is carried out while continuously transporting a long support. The manufacturing method of the cholesteric liquid crystal layer may be carried out using supports transported one by one.

[0159] A method for manufacturing a cholesteric liquid crystal layer will be described with reference to Fig. 6. Fig. 6 is a schematic diagram for explaining an example of a method for manufacturing a cholesteric liquid crystal layer in which the bright lines and dark lines derived from the above-mentioned cholesteric liquid crystal phase are inclined with respect to the normal to the cholesteric liquid crystal layer.

[0160] 6, the cholesteric liquid crystal layer is produced by a roll-to-roll method. A long support F wound into a roll is transported in the direction of the arrow by a transport roll 500. The transport speed of the support F is preferably 10 to 100 m / min.

[0161] A composition is applied to the support F that has passed through the transport roll 500 by the coating device 150 (step (A)). The composition contains a liquid crystal compound, a chiral agent, and a solvent. The coating of the composition by the coating device 150 is preferably carried out in a region where the support F is wound around the backup roll 600. A preferred embodiment of the backup roll 600 will be described below.

[0162] The surface of the backup roll 600 may be hard chrome plated, for example. The thickness of the plating is preferably 40 to 60 μm. The surface roughness Ra of the backup roll 600 is preferably 0.1 μm.

[0163] The surface temperature of the backup roll 600 may be controlled within any temperature range by a temperature control means. The surface temperature of the backup roll 600 may be determined depending on the composition of the composition, the curing performance of the composition, the heat resistance of the support, and the like. The surface temperature of the backup roll 600 is preferably, for example, 40 to 120°C, and more preferably 40 to 100°C. Examples of the temperature control means for the backup roll 600 include a heating means and a cooling means. Examples of the heating means include induction heating, water heating, and oil heating. Examples of the cooling means include cooling with cooling water.

[0164] The diameter of the backup roll 600 is preferably 100 to 1,000 mm, more preferably 100 to 800 mm, and even more preferably 200 to 700 mm.

[0165] The wrap angle of the support F with respect to the backup roll 600 is preferably 60° or more, and more preferably 90° or more. The upper limit of the wrap angle can be set to, for example, 180°. The "wrap angle" refers to the angle between the transport direction of the support when it contacts the backup roll and the transport direction of the support when it separates from the backup roll.

[0166] After the composition is applied to the support F by the application device 150, the composition is dried by the drying device 200 (step (C)). By drying the composition, the content of the solvent in the composition is adjusted.

[0167] After the composition is dried by the drying device 200, the upper surface of the composition that has passed through the transport roll 510 is scraped off with the blade 300, thereby applying a shear force to the surface of the composition (step (B)). The shear force is applied along the transport direction of the composition, i.e., the transport direction of the support. The application of the shear force by the blade 300 is preferably carried out in the region where the support F is wrapped around the backup roll 610.

[0168] The preferred embodiment of the backup roll 610 is the same as that of the backup roll 600. The surface temperature of the backup roll 610 is preferably, for example, 50 to 120°C, and more preferably 60 to 100°C.

[0169] After applying shear force to the composition, the composition is cured by irradiating it with active energy rays from a light source 400 (step (D)). By curing the composition, a cholesteric liquid crystal layer is formed.

[0170] A cholesteric liquid crystal layer is formed on the support F obtained through the above steps. In addition, by using the support F having an alignment film in the method for producing a cholesteric liquid crystal layer shown in Fig. 6, a laminate having the support F, the alignment film, and the cholesteric liquid crystal layer in this order can be produced.

[0171] The prepared cholesteric liquid crystal layer may be used as a transparent screen together with the support F (and the alignment film), or the cholesteric liquid crystal layer may be peeled off from the support F and transferred to another support to be used as a transparent screen.

[0172] As described above, in addition to the cholesteric liquid crystal layer 10a, a light scattering layer containing light scattering particles can also be used as the light projection layer 10 of the transparent screen 102. Fig. 7 shows a conceptual diagram of a light scattering layer used as the light projection layer.

[0173] 7, the light scattering layer 10b used as the light projection layer is a layer containing light scattering particles 50 in a resin that serves as a base material 52. The light scattering layer 10b scatters incident light due to the difference in refractive index between the base material 52 and the light scattering particles 50. The light scattering layer 10b can direct projected light that is incident on the back surface from an oblique direction toward a direction approximately perpendicular to the front surface by scattering the projected light.

[0174] As the light scattering layer 10b, various known light scattering layers used in transparent screens can be used.

[0175] The light scattering particles may be either organic or inorganic particles.

[0176] The organic fine particles contained in the light-scattering layer can be selected from a wide range of conventionally known materials, including, for example, acrylic polymers, styrene-acrylic copolymers, vinyl acetate-acrylic copolymers, vinyl acetate polymers, ethylene-vinyl acetate copolymers, chlorinated polyolefin polymers, multicomponent copolymers such as ethylene-vinyl acetate-acrylic, SBR, NBR, MBR, carboxylated SBR, carboxylated NBR, carboxylated MBR, polyvinyl chloride, polyvinylidene chloride, polyesters, polyolefins, polyurethanes, polymethacrylates, polytetrafluoroethylene, polymethyl methacrylate, polycarbonates, polyvinyl acetal resins, rosin ester resins, episulfide resins, epoxy resins, silicone resins, silicone-acrylic resins, and melamine resins. Melamine resin and acrylic resin fine particles whose surfaces are coated with inorganic fine particles such as silica can also be used. Furthermore, composite particles composed of such organic fine particles and a small amount of inorganic fine particles (where the proportion of inorganic fine particles is less than 50% by mass) can also be used as essentially organic fine particles. It is also possible to use polymers in which a sulfur atom has been introduced into the monomer in order to increase the refractive index, or in which a fluorine substituent has been introduced into the monomer in order to improve weather resistance or decrease the refractive index.

[0177] The inorganic particles contained in the light scattering layer include colloidal silica, precipitated silica, gel silica, vapor-phase silica, alumina, alumina hydrate, rutile and anatase titanium oxide, zinc oxide, zinc sulfide, white lead, antimony oxides, zinc antimonate, lead titanate, potassium titanate, barium titanate, zirconium oxide, cerium oxide, hafnium oxide, tantalum pentoxide, niobium pentoxide, yttrium oxide, chromium oxide, tin oxide, molybdenum oxide, nanodiamond, ATO (antimony-doped tin oxide), ITO (indium tin oxide), and oxide glass such as silicate glass, phosphate glass, and borate glass. These composite oxides or composite sulfides can also be widely used. In addition, in the case of inorganic particles with photocatalytic activity such as titanium oxide and zinc oxide, those coated with an extremely thin layer of silica, alumina, zirconia, etc. on the surface of the inorganic particles can also be used. Furthermore, even when composite particles of inorganic particles and a small amount of organic particles are used, they can be essentially considered as inorganic particles and can be used. In this case, a small amount of organic fine particles means that the proportion of organic fine particles is less than 50% by mass.

[0178] In the present invention, the organic fine particles and inorganic fine particles used as light scattering particles may be used either alone or in combination of two or more kinds, or both organic fine particles and inorganic fine particles may be used in combination.

[0179] The light diffusion performance of the light-scattering particles in the present invention is affected by the relative refractive index between the base material of the light-scattering layer and the light-scattering particles. Therefore, the refractive index of the light-scattering particles is preferably 1.6 or more, more preferably 2.0 or more. Particularly preferred high-refractive-index light-scattering particles are titanium oxide and zirconium oxide. In order to adjust the transparency and / or color tone of the transparent screen, low-refractive-index light-scattering particles such as colloidal silica may be used in combination with high-refractive-index light-scattering particles.

[0180] Although there is no limitation on the average particle size of the light-scattering particles, it is preferably 45 to 340 nm. When the average particle size of the light-scattering particles is 45 to 340 nm, it becomes possible to achieve both high levels of light-scattering performance and high levels of transparency of the screen.

[0181] It is preferable to use a highly transparent resin as the base material of the light-scattering layer. Specific examples of the base material of the light-scattering layer include polyethylene terephthalate, acrylic, polyester, polycarbonate, triacetyl cellulose cycloolefin polymer, and cyclic olefin copolymer. Alternatively, the gelatin gel described in JP 2019-174546 A may be used as the base material of the light-scattering layer.

[0182] Furthermore, in terms of being able to sufficiently scatter incident projection light without impairing transmittance, the content of light-scattering particles in the light-scattering layer is preferably 50% by mass or less, more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass.

[0183] Furthermore, when such a light-scattering layer 10b is used as the light projection layer 10, the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen is preferably 45 to 60°, and more preferably 47.5 to 57.5°. When the light-scattering layer 10b is used as the light projection layer 10, setting the angle θ to 45 to 60° is preferable in that it allows light that is incident obliquely on the back surface of the transparent screen 102 to be properly emitted in a direction approximately normal to the front surface, and it reduces linearly transmitted light.

[0184] A conceptual diagram of an example of the second aspect of the rear-projection display system of the present invention is shown in Figure 8. Note that the rear-projection display system 120 shown in Figure 8 has a similar configuration to the rear-projection display system 100 shown in Figure 1, so the same members and parts are denoted by the same reference numerals, and the following description will mainly focus on the differences.

[0185] The rear-projection display system 120 includes a projection device 110 and a transparent screen 124. The transparent screen 124 includes a support 106 and a light projection layer 12. The projection device 110 and the support 106 are similar to those of the rear-projection display system 100 described above. Similarly to the light projection layer 10 described above, the light projection layer 12 changes the traveling direction of the projection light from the projection device 110, which is obliquely incident from the rear surface of the transparent screen 124, to a direction approximately normal to the transparent screen 124, i.e., the viewing direction of the viewer U.

[0186] In the rear-projection display system 120 according to the second embodiment of the present invention, the optical projection layer 10 of the transparent screen 124 for displaying the image projected by the projection device 110 also has a thickness of 10 to 30 μm. Also in the rear-projection display system 120 according to the second embodiment of the present invention, the projection device 110 projects projection light onto the transparent screen 124 from an oblique direction so that the angle θ between the optical axis shown by the dashed line in Fig. 8 and the normal to the transparent screen 124 shown by the broken line in Fig. 8 is 30° or greater. In the rear-projection display system 120 according to the second embodiment of the present invention, the thickness of the optical projection layer 12 and the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen 124 are the same as those in the rear-projection display system 100 according to the first embodiment described above.

[0187] In the rear-projection display system 120 according to the second embodiment of the present invention, of the projected light emitted by the projection device 110 in the optical axis direction, 10% or more of the projected light is changed in direction of ±10° with respect to the normal to the transparent screen 124. Specifically, as conceptually shown in FIG. 9 , of the projected light traveling along the optical axis of the projection device 110, the direction of the projected light I3 is changed by the transparent screen 124, and the projected light I3 travels within a range of ±10° with respect to the normal to the transparent screen 124 (dashed line). The tristimulus values ​​(X3, Y3, Z3) of the projected light I3 are measured by the measuring device 112. In the transparent screen 124 of the rear-projection display system 120 according to the second embodiment of the present invention, the tristimulus values ​​(X3, Y3, Z3) and the tristimulus values ​​(X0, Y0, Z0) of the projected light I0 emitted by the projection device 110 shown in FIG. 2 described above satisfy the following formula: (X3 / X0)×100≧10[%] (Y3 / Y0)×100≧10[%] (Z3 / Z0)×100≧10[%]

[0188] The second aspect of the rear-projection display system of the present invention has such a configuration, and thus realizes a rear-projection display system with good visibility of the projected image, similar to the first aspect of the rear-projection display system of the present invention.

[0189] In the rear-projection display system 120 of the present invention, the transparent screen 124 changes the traveling direction of 10% or more of the projection light emitted by the projection device 110 and traveling along the optical axis to a direction at ±10° from the normal. That is, the rear-projection display system 120 of the present invention can change the traveling direction (optical path) of much of the light that enters the transparent screen 124 from an oblique direction to a direction approximately normal to the transparent screen 124. As a result, the rear-projection display system 120 of the present invention can project much of the projection light emitted by the projection device 110 toward the viewing direction of the observer U using the transparent screen 124. This allows the second aspect of the rear-projection display system of the present invention to improve the visibility of the projected image. Furthermore, the fact that much of the projection light changes its traveling direction to a direction approximately normal to the transparent screen 124 means that the transmittance of the straight-traveling transmitted light I2, which travels straight and is transmitted without being changed by the transparent screen 124, is low. As a result, the rear-projection display system 120 of the present invention can reduce the amount of light (brightness) of the straight-through transmitted light I2 and prevent it from being seen by the observer U, thereby improving the visibility of the projected image in this respect as well.

[0190] In the rear-projection display system 120 of the second aspect of the present invention, the visibility of the projected image can be improved by setting the angle θ between the optical axis of the projection device 110 and the normal to the transparent screen 124 to 30° or more, just like in the rear-projection display system 100 of the first aspect. Furthermore, in the rear-projection display system 120 of the second aspect of the present invention, the thickness of the light projection layer 12 can be set to 10 to 30 μm, which is also advantageous in that it can improve the visibility of the background, just like in the rear-projection display system 100 of the first aspect.

[0191] As described above, in the rear-projection display system 120 of the present invention, the direction of travel of 10% or more of the projection light traveling along the optical axis of the projection device 110 is changed in directions at ±10° with respect to the normal to the transparent screen 124. Hereinafter, the proportion of the projection light traveling along the optical axis of the projection device 110 and having its direction changed in directions at ±10° with respect to the normal to the transparent screen 124 will also be referred to as the "proportion of projection light whose optical path is changed." In other words, in the rear-projection display system 120 of the second aspect of the present invention, the proportion of the projection light whose optical path is changed by the transparent screen 124 is 10% or more.

[0192] If the proportion of the projected light whose optical path is changed is less than 10%, it will not be possible to obtain a sufficient effect of improving the visibility of the projected image, and it will be disadvantageous in that the straight-transmitted light I2 will be easily visible to the observer U. The proportion of the projected light whose optical path is changed is preferably 12.5% ​​or more, and more preferably 15% or more.

[0193] In the present invention, the proportion of the projection light whose optical path is changed may be measured, as previously described, at 5 nm intervals across the entire wavelength range of the projection light projected by the projection device 110. Here, in the rear-projection display system 120 of the present invention, the proportion of the projection light whose optical path is changed may be the average value of each measured wavelength. However, in consideration of the color balance of the projected image and the suppression of background coloring, as previously described, in the present invention, the proportion of the projection light whose optical path is changed at the tristimulus values ​​(X, Y, Z) during white display is preferably 10% or more, and more preferably the proportion of the projection light whose optical path is changed at the tristimulus values ​​(X, Y, Z) is the same.

[0194] In the rear-projection display system 120 according to the second aspect of the present invention, various preferred aspects such as the haze of the transparent screen and the total light transmittance of the transparent screen are the same as those of the rear-projection display system 100 according to the first aspect of the present invention described above.

[0195] In the rear-projection display system 120 according to the second aspect of the present invention, the light projection layer 12 can be the same as the light projection layer 10. In particular, the cholesteric liquid crystal layer 10a is preferably used as the light projection layer 12.

[0196] In both the first and second aspects of the rear-projection display system of the present invention, a quarter-wave plate may be provided between the transparent screen and the projection device. In particular, when the light projection layer (light projection layer 10 and light projection layer 12) is a cholesteric liquid crystal layer 10a, it is preferable to provide a quarter-wave plate between the transparent screen and the projection device 110. That is, when the light projection layer is a cholesteric liquid crystal layer 10a, it is preferable that the projection light transmitted through the quarter-wave plate is incident on the transparent screen.

[0197] As is well known, a cholesteric liquid crystal layer selectively reflects specific circularly polarized light in a specific wavelength range. Therefore, when the light projection layer is a cholesteric liquid crystal layer 10a, it is preferable to use a quarter-wave plate to convert at least a portion of the projection light into circularly polarized light corresponding to the cholesteric liquid crystal layer 10a before it is incident on the transparent screen. This makes it possible to efficiently change the traveling direction of the projection light to approximately the normal direction of the transparent screen.

[0198] There are no limitations on the quarter-wave plate, and various known quarter-wave plates (λ / 4 plates, λ / 4 retardation plates) having a phase difference of approximately ¼ wavelength at any wavelength of visible light can be used. Furthermore, the quarter-wave plate may be integrated with the transparent screen or may be a separate member. Preferred examples of the quarter-wave plate include quarter-wave plates having a phase difference of 100 to 180 nm at a wavelength of 550 nm, and more preferred examples include quarter-wave plates having a phase difference of 120 to 160 nm.

[0199] Furthermore, if the projection device 110 emits unpolarized projection light, a linear polarizer may be provided between the projection device 110 and the quarter-wave plate, as necessary. There are no limitations on the linear polarizer, and various known linear polarizers can be used.

[0200] In the rear-projection display system of the present invention, the transparent screen (transparent screen 102 and transparent screen 124) may have layers other than the support 106, alignment film, and light projection layer (light projection layer 10 and light projection layer 12) described above.

[0201] For example, the transparent screen may have a louver film that transmits only light incident at a predetermined angle of incidence. The transparent screen may also have a diffraction element that diffracts incident light in a predetermined direction. By including a louver film and / or a diffraction element in the transparent screen, the amount of light transmitted in a straight line can be reduced, improving visibility. Various known louver films, such as light-blocking louver films and scattering louver films, can be used. The light-blocking louver film has alternating strips of light-transmitting and light-blocking bands, which transmit light incident from a specific direction and block the transmission of light incident from directions other than the specific direction. The scattering louver film transmits light incident from a specific direction and diffuses light incident from directions other than the specific direction. Various known diffraction elements, such as volume holograms, surface reliefs, and liquid crystal diffraction elements, can also be used.

[0202] Furthermore, the transparent screen may have an anti-reflection layer (anti-reflection film) on the rear surface 103. As the anti-reflection layer, various known anti-reflection layers can be used, such as a dielectric multilayer film formed by alternately laminating layers with high refractive index and layers with low refractive index, and a moth-eye film.

[0203] The light of the projected image from the projection device may be irradiated onto the back of the transparent screen from the ceiling or overhead, or from the wall (side) side, or from the floor side, based on the standing position of the rear-projection display system.

[0204] As described above, a rear projection display system can be used to display an image on the window glass of an automobile or building, etc., using the window glass as a transparent screen.

[0205] The rear-projection display system of the present invention has been described in detail above, but the present invention is not limited to the above-described examples, and various improvements and modifications may of course be made within the scope of the gist of the present invention.

[0206] The features of the present invention will be explained in more detail below with reference to examples. The materials, reagents, amounts used, amounts of substances, ratios, treatment details, and treatment procedures shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0207] [Preparation of Transparent Screen 1]

[0208] <Preparation of coating solution for alignment layer> A container containing pure water (96 parts by mass) was kept at 80°C, and PVA-205 (4 parts by mass, manufactured by Kuraray Co., Ltd.) was mixed and stirred to prepare a coating solution for alignment layer.

[0209] <Preparation of Coating Solution for Cholesteric Liquid Crystal Layer> The following components were mixed to prepare a coating solution for a cholesteric liquid crystal layer having the following composition: 100 parts by mass of the following liquid crystal compound mixture 1 1.2 parts by mass of the following right-handed chiral agent LC-756 (manufactured by BASF) 3 parts by mass of IRGACURE 907 (manufactured by BASF) 0.5 parts by mass of the following alignment regulator 1 part by mass of PM758 (manufactured by Nippon Kayaku Co., Ltd.) 184 parts by mass of methyl ethyl ketone 31 parts by mass of cyclohexanone

[0210] Liquid crystal compound mixture 1 The values ​​are in mass %.

[0211] ・Dextrorotatory chiral agent

[0212] ・Alignment control agent

[0213] <Formation of alignment film> The prepared alignment film layer coating solution was applied onto a triacetyl cellulose film (manufactured by Fujifilm Corporation, thickness: 80 μm) as a support using a bar with a bar count of 6, and then dried at 100° C. for 10 minutes to form an alignment film with a thickness of 2 μm on the substrate.

[0214] <Formation of Cholesteric Liquid Crystal Layer> Next, the support on which the alignment film was formed was heated to 70°C, and the prepared cholesteric liquid crystal layer coating solution was applied onto the alignment film using a bar with a bar count of 18, followed by drying at 70°C for 1 minute to form a cholesteric liquid crystal layer. The thickness of the cholesteric liquid crystal layer was 10 µm.

[0215] <Application of Shear Force> Next, while the formed cholesteric liquid crystal layer was heated to 70°C, a stainless steel blade heated to 70°C was brought into contact with the cholesteric liquid crystal layer. In this contact state, the blade was moved at a speed of 1.5 m / min to apply shear force. The shear rate was 2500 s -1 It was decided.

[0216] <Curing> After applying shear force, the cholesteric liquid crystal layer was irradiated with ultraviolet light from a metal halide lamp through a long wavelength cut filter (SH0325, manufactured by Asahi Spectroscopy Co., Ltd.) (exposure amount: 2 mJ / cm 2 After that, the long wavelength cut filter was removed, and the film was irradiated with ultraviolet light (exposure dose: 500 mJ / cm ) using a metal halide lamp in a nitrogen atmosphere (oxygen concentration: less than 100 ppm). 2 ) to prepare a transparent screen 1.

[0217] <Tilt Angle and Spacing of Bright and Dark Lines> The fabricated transparent screen 1 was cut in the thickness direction, and the cross section was observed using an SEM. As a result, it was confirmed that the angle β between the bright and dark lines and the main surface of the cholesteric liquid crystal layer was 62°. In addition, the spacing between the bright and dark lines was 0.85 μm.

[0218] [Preparation of Transparent Screen 2] Transparent screen 2 was prepared in the same manner as transparent screen 1, except that a bar having a bar count of 22 was used when applying the coating solution for the cholesteric liquid crystal layer onto the alignment film. The thickness of the formed cholesteric liquid crystal layer was 12 μm.

[0219] [Preparation of Transparent Screen 3] Transparent screen 3 was prepared in the same manner as transparent screen 1, except that a bar with a bar count of 47 was used when applying the coating solution for the cholesteric liquid crystal layer onto the alignment film. The thickness of the formed cholesteric liquid crystal layer was 26 μm.

[0220] [Preparation of Transparent Screen H1] A transparent screen H1 was prepared in the same manner as the transparent screen 1, except that a bar with a bar count of 6 was used when applying the coating solution for the cholesteric liquid crystal layer onto the alignment film. The thickness of the formed cholesteric liquid crystal layer was 3 μm.

[0221] [Fabrication of Transparent Screen H2] A transparent screen H2 was fabricated in the same manner as the transparent screen 1, except that a bar with a bar count of 16 was used when applying the coating solution for the cholesteric liquid crystal layer onto the alignment film. The thickness of the formed cholesteric liquid crystal layer was 8 μm.

[0222] [Fabrication of Transparent Screen H3] Transparent screen H3 was fabricated in the same manner as transparent screen 1, except that a bar with a bar count of 60 was used when applying the coating solution for the cholesteric liquid crystal layer onto the alignment film. The thickness of the formed cholesteric liquid crystal layer was 33 μm.

[0223] As a result of checking in the same way as for Transparent Screen 1, the angles β between the bright and dark lines and the main surface of the cholesteric liquid crystal layer, as well as the distance between the bright and dark lines, for Transparent Screens 2, 3, and Transparent Screens H1 to H3 were the same as those for Transparent Screen 1.

[0224] [Evaluation] Each of the prepared transparent screens having a cholesteric liquid crystal layer was prepared in a size of 15 cm square and attached to a transparent glass plate via an adhesive (SK adhesive, manufactured by Soken Chemical Co., Ltd.) with the cholesteric liquid crystal layer side facing the glass.

[0225] Next, a projector (MH550, manufactured by BenQ Corporation) was used as the projection device, and projection light was incident on the transparent screen to display a projected image. The projected image used was an image with "FUJIFILM" written in black in the center of an all-white screen. At this time, the projector and transparent screen were positioned so that the angle (incident angle) between the optical axis of the projector (center of the projected light) and the normal to the transparent screen was either 56°, 35°, 60°, or 28°. The projection light was incident from the glass side.

[0226] The image visibility of the projected image was evaluated visually from the front side of the transparent screen, that is, from the opposite side from the projector.

[0227] After that, the image light was set to a white display. In this state, a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation) placed on the optical axis of the projector was used to measure the tristimulus values ​​(X2, Y2, Z2) of the light that traveled straight through and was transmitted through the transparent screen, as well as the tristimulus values ​​(X0, Y0, Z0) of the light projected from the projector when a white display was being performed without a transparent screen (see Figure 2). The same spectroradiometer was also used to measure the tristimulus values ​​(X3, Y3, Z3) of the light that traveled along the optical axis and was deflected by the transparent screen in a direction of ±10° relative to the normal to the transparent screen (see Figure 9). From the measured tristimulus values, the transmittances of the transparent screen ((X2 / X0) x 100), (Y2 / Y0) x 100), and (Z2 / Z0) x 100) were calculated, as well as the proportion of projected light deflected by the transparent screen in directions ±10° from the normal to the transparent screen (i.e., the proportion of projected light whose optical path was deflected (front projection rate) ((X3 / X0) x 100), (Y3 / Y0) x 100), and (Z3 / Z0) x 100). The results are shown in the table below.

[0228] In the above table, as mentioned above, "film thickness" refers to the film thickness of the cholesteric liquid crystal layer, which is the light projection layer, and "visibility" refers to the image visibility when the projected image is viewed from the front. The transmittance of the transparent screen is the transmittance of the transparent screen obtained by measuring the tristimulus values ​​with and without the transparent screen on the optical axis. The front projection ratio is the ratio of the tristimulus values ​​of the projected light whose path is changed by the transparent screen in a direction ±10° from the normal to the projected light irradiated by the projector. The incident angle is the angle between the optical axis of the projector and the normal to the transparent screen.

[0229] The haze and total light transmittance of each transparent screen were measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. The results are shown in Table 2 below. Here, the total light transmittance is the value of (scattered transmittance of natural light in the range of 380 to 780 nm + direct transmittance of natural light) x 100%.

[0230]

[0231] As shown in the table above, by setting the incident angle of the projection light onto the transparent screen to 30° or more, the thickness of the light projection layer to 10 to 30 μm, and further setting the transmittance of the transparent screen to 50% or less and / or the projection rate of the light projected in the front direction to 10% or more, it is possible to prevent the direct transmitted light from adversely affecting the projected image and obtain high image visibility. Among these, Example 2, which satisfied both the transparent screen transmittance of 50% or less and the projection rate of the light projected in the front direction to 10% or more, and set the incident angle to the Brewster angle (56°), produced particularly good results. The above results clearly demonstrate the effectiveness of the present invention.

[0232] The present invention can be suitably used for projecting images onto window glass of various buildings and vehicles, etc., so that the background can be seen.

[0233] 10, 12 Light projection layer 10a Cholesteric liquid crystal layer 10b Light scattering layer 40 Liquid crystal compound 40A Optical axis 42 Bright line 44 Dark line 50 Light scattering particles 52 Base material 100, 120 Rear projection display system 102, 124 Transparent screen 103 Back surface 104 Front surface 106 Support 110 Projection device 150 Coating device 200 Drying device 300 Blade 400 Light source 500, 510 Transport roll 600, 610 Backup roll θ Angle I1, I3 Projected light I2 Straight transmitted light U Observer D1 Alignment axis C1 Helical axis β Angle

Claims

1. a projection device that emits projection light; and a transparent screen that projects the projection light emitted by the projection device in an observation direction; the transparent screen has a light projection layer for projecting the projection light having a thickness of 10 to 30 μm; the projection device projects the projection light onto the transparent screen so that an angle between an optical axis and a normal line of the transparent screen is 30° or more; and a transparent screen having a transmittance of 50% or less for the projection light in the optical axis direction emitted by the projection device;

2. 2. The rear-projection display system of claim 1, further comprising a quarter wave plate between the transparent screen and the projection device.

3. 3. The rear-projection display system of claim 1, wherein the transparent screen has a haze of 25% or less.

4. 3. The rear-projection display system of claim 1, wherein the transparent screen has a total light transmittance of 80% or more.

5. the transparent screen has at least one cholesteric liquid crystal layer as the light projection layer; and 3. The rear projection display system according to claim 1, wherein in a cross section of the cholesteric liquid crystal layer in the thickness direction observed by a scanning electron microscope, bright lines and dark lines derived from a cholesteric liquid crystal phase are inclined with respect to a main surface of the cholesteric liquid crystal layer.

6. 6. The rear-projection display system of claim 5, wherein the bright and dark lines originating from the cholesteric liquid crystal phase are inclined at an angle of 20 to 90 degrees with respect to a major surface of the cholesteric liquid crystal layer.

7. A rear projection display system as described in claim 1 or 2, wherein the transparent screen has a transmittance of the projection light in the optical axis direction emitted by the projection device of 50% or less for all tristimulus values ​​(X, Y, Z) when displaying white.

8. a projection device that emits projection light; and a transparent screen that projects the projection light emitted by the projection device in an observation direction; the transparent screen has a light projection layer for projecting the projection light having a thickness of 10 to 30 μm; the projection device projects the projection light onto the transparent screen so that an angle between an optical axis and a normal line of the transparent screen is 30° or more; and The transparent screen changes the traveling direction of 10% or more of the projection light emitted by the projection device in the optical axis direction to a direction of ±10° with respect to the normal to the transparent screen.

9. 9. The rear-projection display system of claim 8, further comprising a quarter wave plate between the transparent screen and the projection device.

10. 10. The rear-projection display system of claim 8, wherein the transparent screen has a haze of 25% or less.

11. 10. The rear-projection display system of claim 8, wherein the transparent screen has a total light transmittance of 80% or more.

12. the transparent screen has at least one cholesteric liquid crystal layer as the light projection layer; and 10. The rear-projection display system according to claim 8, wherein in a cross section of the cholesteric liquid crystal layer observed with a scanning electron microscope, bright lines and dark lines derived from a cholesteric liquid crystal phase are inclined with respect to a main surface of the cholesteric liquid crystal layer.

13. 13. The rear-projection display system of claim 12, wherein the bright and dark lines originating from the cholesteric liquid crystal phase are inclined at an angle of 20 to 90 degrees with respect to a major surface of the cholesteric liquid crystal layer.

14. A rear projection display system as described in claim 8 or 9, wherein the transparent screen, when displaying white, changes the direction of travel of 10% or more of the projection light in the optical axis direction emitted by the projection device to a direction of ±10° with respect to the normal to the transparent screen for all three stimulus values ​​(X, Y, Z).