JP4200123B2 - Projection screen and projection system including the same - Google Patents

Description

  The present invention relates to a projection system for projecting image light onto a projection screen by a projector and displaying the image, and in particular, effectively suppressing the influence of ambient light such as illumination light and displaying the image clearly. The present invention relates to a projection screen excellent in visibility capable of changing a viewing angle of an image and a projection system including the projection screen.

  As a conventional projection system, an image light projected by a projector is projected on a projection screen, and an observer observes the reflected light as an image.

  As a projection screen used in such a conventional projection system, a white paper material or a cloth material, or a plastic film coated with an ink that scatters white light is generally used. Further, as a higher quality projection screen, a screen that includes a scattering layer in which beads, pearls and the like are kneaded, and the scattering state of image light is controlled by this scattering layer is commercially available.

  By the way, in recent years, the demand for home use such as a home theater has increased with the miniaturization of the projector main body and the price reduction, and the projection system is often used in general homes. In this case, the projection system is often installed in a living space at home, but such a place is usually designed to easily receive ambient light such as outside light and illumination light. For this reason, a projection screen used in a projection system for home use is desired to be able to realize a good video display even under bright ambient light.

  However, in the above-described conventional projection screen, ambient light such as outside light and illumination light is reflected in the same manner as image light, so that it is difficult to realize a good image display under bright ambient light. There is a problem.

  Specifically, in the conventional projection system, the shade of the image is created by the difference in intensity of the projection light (image light) from the projector projected onto the projection screen. For example, a white picture is projected on a black background. In such a case, the portion where the projection light hits the projection screen is white and the other portion is black, and the shade of the image is created by such a difference in brightness between black and white. In this case, in order to realize a good video display, it is necessary to make the white display portion brighter and the black display portion darker to increase the contrast difference.

  However, since the above-described conventional projection screen reflects ambient light such as external light and illumination light without distinction from image light, both the white display portion and the black display portion become bright, and the brightness of black and white is increased. The difference in height will be small. For this reason, with the conventional projection screen described above, it is difficult to realize a good image display unless the influence of ambient light such as outside light or illumination light is suppressed by using a means or environment for darkening the room. There is a problem that.

Under such a background, conventionally, a projection screen capable of realizing a good image display even under bright ambient light has been studied, for example, using a hologram or using a polarization separation layer. A thing (refer patent documents 1 and 2) etc. is proposed. In addition, as a projection screen using the latter polarization separation layer, a projection screen having a polarization separation layer that reflects right circularly polarized light and left circularly polarized light has been proposed (see Patent Document 3).
JP-A-5-107660 JP 2002-540445 A Japanese Patent Laid-Open No. 3-150546

  However, among the conventional projection screens described above, the projection screen using a hologram can control the scattering effect to make the white display portion brighter, and can display a relatively good image under bright ambient light. Although it can be realized, the hologram has wavelength selectivity but does not have polarization selectivity, so it is difficult to darken the black display part, and the image is sharpened only to a certain extent. There is a problem that it cannot be displayed. Further, a projection screen using a hologram has a problem that it is difficult to enlarge the screen due to a manufacturing problem.

  On the other hand, in the projection screen using the polarization separation layer, it is possible to make the white display portion brighter while making the black display portion darker. The video can be displayed clearly.

  However, in the projection screen using such a polarization separation layer, it is necessary to give a diffused effect to the reflected light in order to visually recognize the light as an image. However, in the projection screen described in Patent Document 1, No consideration is given to points. Moreover, although the said patent document 2 has described the projection screen which gives a diffused effect to reflected light by the diffusion element etc. which were provided separately from the polarization separation layer, by the diffusion element etc. which were provided separately from the polarization separation layer When the diffusion effect is given, the original polarization separation function is impaired, and the visibility of the image cannot be sufficiently improved. That is, since the diffusing element is provided on the viewer side of the polarization separation layer, light is transmitted through the diffusion element before entering the polarization separation layer, and the polarization state is disturbed (this is referred to as “depolarization”). Called). Here, there are two types of light that pass through the diffusing element: ambient light (external light, etc.) and image light. If the polarization state of the ambient light is disturbed by the diffusing element, it is originally transmitted through the polarization separation layer. The light to be converted is converted into a component reflected by the polarization separation layer due to depolarization, and is reflected by the polarization separation layer as unnecessary light. In addition, when the polarization state of the image light is disturbed by the diffusing element, the light that should be reflected by the polarization separation layer is converted to a component that is not reflected by the polarization separation layer due to depolarization, and is transmitted through the polarization separation layer. Resulting in. Due to these two phenomena, the original polarization separation function is impaired, and the visibility of the image cannot be sufficiently improved.

  Further, in the projection screen described in Patent Document 3, the diffusion characteristics of the polarization separation layer are not taken into consideration at all. In addition, although the said patent document 3 describes the projection screen which reflects the light (right circularly polarized light and left circularly polarized light) of a different polarization state by a polarization separation layer, the point which controls the viewing angle of these reflected light There is no consideration for.

  Under such a background, the present inventor previously provided a polarization selective reflection layer having a cholesteric liquid crystal structure, and the image non-uniformity of the cholesteric liquid crystal structure prevents the image light from being deteriorated. A projection screen that can give a diffused effect to reflected light has been proposed (Japanese Patent Application No. 2003-165687).

  The present invention has been made for the purpose of further improving such a projection screen, and can effectively suppress the influence of ambient light such as illumination light and display an image clearly even under bright ambient light. An object of the present invention is to provide a projection screen with excellent visibility and a projection system including the projection screen.

  It is another object of the present invention to provide a projection screen with excellent visibility that can change the viewing angle of an image in accordance with the observation state of the image and a projection system including the projection screen.

  As a first solution, the present invention provides a first polarization selective reflection layer that selectively reflects the first polarization having a specific polarization component, and the first polarization that is reflected by the first polarization selective reflection layer. Includes a second polarization selective reflection layer that selectively reflects second polarized light having different polarization components, and the first polarization selective reflection layer and the second polarization selective reflection layer receive reflected light according to their own structures. The diffusion angle of the first polarization reflected by the first polarization selective reflection layer and the diffusion angle of the second polarization reflected by the second polarization selective reflection layer are different from each other. A projection screen is provided.

  In the first solving means described above, it is preferable that one of the first polarized light and the second polarized light is right circularly polarized light and the other is left circularly polarized light.

Further, in the first aspect described above, the first polarized-light selective reflection layer and the second polarized-light selective reflection layer preferably has a cholesteric liquid crystal structure. Here, it is preferable that the cholesteric liquid crystal structures of the first polarization selective reflection layer and the second polarization selective reflection layer include a plurality of spiral structure regions having different spiral axis directions.

  Furthermore, in the first solving means described above, the first polarization selective reflection layer and the second polarization selective reflection layer selectively reflect light in a specific wavelength range that covers only a part of the visible light range. It is preferable.

  Furthermore, in the first solving means described above, the selective reflection center wavelengths of the first polarized light selective reflection layer and the second polarized light selective reflection layer are different from the first polarized light selective reflection layer and the second polarized light selective reflection layer. Thus, it is preferable that the light is in any of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm on the basis of the case where the light is vertically incident.

Furthermore, in the first solving means described above, the first polarized light selective reflection layer and the second polarized light selective reflection layer are preferably made of a polymerizable liquid crystal material after solidification .

  Furthermore, it is preferable that the first solving means described above further includes a support base material that supports the first polarized light selective reflection layer and the second polarized light selective reflection layer. Here, the support substrate may include a light absorption layer that absorbs light in a visible light region. The support substrate may be a transparent substrate that transmits at least part of light in the visible light range.

  The present invention includes, as a second solving means, a projection screen according to the first solving means described above, and a projector that projects image light on the projection screen, and the image light projected from the projector is It is preferable that the polarization state is switched so as to have a polarization component of either the first polarization or the second polarization.

  In the second solving means described above, an illumination light source that irradiates illumination light toward the projection screen is further provided, and the illumination light emitted from the illumination light source includes the first polarization selective reflection layer and the It is preferable that the first polarization and the second polarization reflected by the second polarization selective reflection layer have substantially the same wavelength dispersion as the wavelength dispersion.

  Further, in the second solving means described above, the illumination light emitted from the illumination light source is reflected by the first polarized light selective reflection layer and the second polarized light selective reflection layer and the second polarized light. It is preferable that the polarization component has the same polarization component as the polarization component having the smaller diffusion angle.

  According to the present invention, the first polarization selective reflection layer that selectively reflects the first polarization having a specific polarization component and the first polarization component that is different from the first polarization reflected by the first polarization selection reflection layer. A second polarization selective reflection layer that selectively reflects two polarized light, and in the first polarization selective reflection layer and the second polarization selective reflection layer, the reflected light is diffused by its own structure, and the first polarization selective reflection is performed. The diffusion angle of the first polarization reflected by the layer and the diffusion angle of the second polarization reflected by the second polarization selective reflection layer are made different from each other.

  At this time, according to the present invention, each polarization selective reflection layer (first polarization selective reflection layer and second polarization selective reflection layer) selectively reflects light of different polarization components at different diffusion angles. By controlling the polarization state of ambient light (illumination light, etc.) and image light incident on a projection screen comprising such a polarization selective reflection layer, ambient light (illumination light, etc.) and images reflected by each polarization selective reflection layer The light diffusion angle can be adjusted. Specifically, for example, by controlling the polarization state of ambient light (illumination light, etc.) and image light incident on each polarization selective reflection layer, the image light is reflected by the polarization selective reflection layer having a larger diffusion angle. If the ambient light (illumination light, etc.) is reflected by the polarization selective reflection layer having a small diffusion angle, the ambient light (illumination light, etc.) incident on the projection screen from an oblique direction will be reflected in each polarization selective reflection layer. However, since the directivity is strong, the reflected light is reflected in a direction different from the observation direction in a form close to specular reflection. For this reason, even in bright ambient light where illumination light exists, it is effectively reduced that ambient light (illumination light, etc.) overlaps the image light, so the brightness of the dark display part such as black display is reduced. Becomes darker and the contrast of the image can be improved.

  In each polarization selective reflection layer (first polarization selective reflection layer and second polarization selective reflection layer), the reflected light is diffused by its own structure (for example, a cholesteric liquid crystal structure having structural nonuniformity). Therefore, the image light is diffusely reflected, not specularly reflected, and the image is easy to visually recognize. At this time, each polarization selective reflection layer diffuses reflected light by its own structure, so that it reflects while diffusing light of a specific polarization component, while allowing other light to pass through without diffusing. Can do. For this reason, unlike the case where a diffusion layer is provided separately from each polarization selective reflection layer, the above-mentioned “depolarization” problem occurs with respect to environmental light (illumination light, etc.) and image light transmitted through each polarization selective reflection layer. Thus, the visibility of the image can be improved while maintaining the original polarization separation function of each polarization selective reflection layer. An example in which the cholesteric liquid crystal structure has structural non-uniformity includes a case where the direction of the helical axis of the helical structure region included in the cholesteric liquid crystal structure varies.

  Further, according to the present invention, each polarization selective reflection layer (first polarization selective reflection layer and second polarization selective reflection layer) selectively reflects light of different polarization components at different diffusion angles. By switching and controlling the polarization state of the image light incident on the projection screen made of the selective reflection layer, the diffusion angle of the image light reflected by the projection screen, that is, the viewing angle of the image can be changed. Specifically, for example, if the right circularly polarized light is reflected by the polarization selective reflection layer having a smaller diffusion angle and the left circular polarization is reflected by the polarization selective reflection layer having a larger diffusion angle, If the polarization state is controlled so that the image light projected on the projection screen becomes right circularly polarized light, the projection screen can be made to function as a narrow field screen (a narrow field angle but a bright screen). A high brightness screen suitable for observation by a number of people can be obtained. On the other hand, if the polarization state is controlled so that the image light projected from the projector onto the projection screen becomes left circularly polarized light, the projection screen can function as a wide-field screen (screen with a wide viewing angle). Thus, a screen suitable for observation with a large number of people can be obtained. Furthermore, if the polarization state is controlled so that the image light projected from the projector onto the projection screen is unpolarized or linearly polarized, the intermediate characteristics of the two screens (the narrow-field screen and the wide-field screen) described above can be obtained. You can get the screen you have.

  Furthermore, according to the present invention, each polarization selective reflection layer (the first polarization selective reflection layer and the second polarization selective reflection layer) selectively selects light in a specific wavelength range that covers only a part of the visible light range. By reflecting, the projection screen composed of such a polarization selective reflection layer can further suppress the influence of ambient light such as outside light and illumination light, and can enhance the contrast of the image, thereby improving the visibility of the image. It can be improved further. That is, a projector that projects image light on a projection screen generally realizes color display with light in the wavelength ranges of red (R), green (G), and blue (B), which are the three primary colors of light. The light having a selective reflection center wavelength in the range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm is projected on the basis of the case where the light is vertically incident on the projection screen. For this reason, in the projection screen, by selectively reflecting only the light in the wavelength range corresponding to the wavelength range of the image light projected by the projector, the above-mentioned environmental light such as external light and illumination light is the above-mentioned. Thus, reflection of light in the visible light range that is out of the wavelength range is prevented, and the contrast of the image can be increased.

  Furthermore, according to the present invention, the wavelength dispersion of ambient light (such as illumination light) incident on each polarization selective reflection layer (the first polarization selective reflection layer and the second polarization selective reflection layer) is reduced in each polarization selective reflection layer. By making it substantially the same as the wavelength dispersion of the reflected polarized light, it is possible to further suppress the influence of ambient light (illumination light, etc.) and increase the contrast of the image, further improving the visibility of the image. be able to. That is, an illumination light source or the like that irradiates illumination light serving as ambient light is usually installed on a ceiling or a wall and irradiates illumination light from an oblique direction to the projection screen. On the other hand, the projector that projects the image light is installed at the front position of the projection screen. In other words, the illumination light that becomes the ambient light is incident on the projection screen at an angle different from that of the image light, so that the wavelength of the light reflected by each polarization selective reflection layer shifts due to the difference in the incident angle. It becomes. Specifically, the wavelength λ (θ) of light when the light incident at the incident angle θ is reflected by each polarization selective reflection layer is represented by λ (θ) = λ (0) × cos θ. The illumination light incident from an oblique direction is shifted to the short wavelength side. For this reason, the reflectance of the illumination light reflected by each polarization selective reflection layer is lower than the reflectance of the image light, and does not hinder the visibility of the image.

BEST MODE FOR CARRYING OUT THE INVENTION

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a projection system including a projection screen according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIGS. 1 and 2, the projection system 20 according to the present embodiment includes a projection screen 10 and a projector 21 that projects image light 31 on the projection screen 10.

  Among these, the projection screen 10 displays the image by reflecting the image light 31 projected by the projector 21 from the viewer 45 side, and the first polarized light (for example, right circularly polarized light) having a specific polarization component. The first polarization selective reflection layer 11-1 that selectively reflects the second polarization (for example, left circular polarization) having a polarization component different from the first polarization reflected by the first polarization selective reflection layer 11-1. A second polarization selective reflection layer 11-2 that selectively reflects, and a support substrate 12 that supports the first polarization selective reflection layer 11-1 and the second polarization selective reflection layer 11-2 are provided.

  Each of the first polarization selective reflection layer 11-1 and the second polarization selective reflection layer 11-2 has a cholesteric liquid crystal structure, and diffuses reflected light due to the structural nonuniformity of the cholesteric liquid crystal structure. It has become.

In addition, the first polarized light selective reflection layer 11-1 and the second polarized light selective reflection layer 11-2 have different diffusion characteristics, and the first polarized light (for example, right) reflected by the first polarized light selective reflection layer 11-1. The diffusion angle of the circularly polarized light and the diffusion angle of the second polarized light (for example, left circularly polarized light) reflected by the second polarized light selective reflection layer 11-2 are different from each other. Specifically, for example, the diffusion angle of the reflected light of the first polarized light reflected by the first polarized-light selective reflection layer 11-1 (e.g. right circularly polarized light) (see diffusion angle theta ₁ of the reflected light 41 shown in FIG. 1) is is smaller than the second polarizing diffusion angle of reflected light reflected by the second polarized-light selective reflection layer 11-2 (see diffusion angle theta ₂ of the reflected light 42 shown in FIG. 2).

  The image light 31 projected from the projector 21 onto the projection screen 10 is configured such that its polarization state is switched so as to have a polarization component of either right circular polarization or left circular polarization. Specifically, for example, when the projector 21 emits linearly polarized light, the polarization control member 22 made of a linearly polarizing film and a phase difference film (1 / 4λ phase difference plate) is provided at the exit of the projector 21. Is provided so that the image light 31 can be switched to an arbitrary polarization state (right circularly polarized light or left circularly polarized light) in accordance with the rotation of the slow axis of the retardation film (¼λ retardation plate). . Thus, if the polarization state is controlled so that the image light 31 projected from the projector 21 onto the projection screen 10 becomes right circularly polarized light, the projection screen becomes a narrow-field screen (screen with a narrow viewing angle but a bright screen). And a high brightness screen suitable for observation with a small number of people can be obtained. On the other hand, if the polarization state is controlled so that the image light 31 projected from the projector 21 onto the projection screen 10 becomes left circularly polarized light, the projection screen functions as a wide-field screen (screen with a wide viewing angle). And a screen suitable for observation with a large number of people can be obtained. Furthermore, if the polarization state is controlled so that the image light 31 projected from the projector 21 onto the projection screen 10 becomes non-polarized light or linearly polarized light, the intermediate between the two screens described above (the narrow-field screen and the wide-field screen). You can get a screen with the characteristics of In addition to the method of providing the polarization control member 22 at the exit of the projector 21, a method of controlling the polarization state of the image light 31 inside the projector 21 may be used. For example, a DMD projector If so, the polarization state can be controlled by switching the light source itself.

  Here, as the projector 21, a CRT, a liquid crystal projector, a DLP (digital light processing) projector, a laser projector, or the like can be used, but is not particularly limited. However, the image light 31 projected on the projection screen 10 by the projector 21 is preferably circularly polarized light. Here, when a liquid crystal projector is used as the projector 21, in many cases, substantially linearly polarized light is emitted from the operation principle. In such a case, linearly polarized light can be converted into circularly polarized light without loss of light quantity by emitting the image light 31 emitted from the projector 21 through a phase difference plate or the like. When such a retardation plate is provided, the above-described polarization state control (switching) can be realized by rotating the optical axis of the retardation plate.

  In addition, as a phase difference plate, what has a quarter wavelength phase difference is used preferably, and specifically, the thing which has a phase difference of 137.5 nm according to 550 nm with the highest visibility is ideal. In addition, a broadband quarter-wave retardation plate is more preferable in the sense that it can be applied to light emitted in all the wavelength regions of red (R), green (G), and blue (B). Furthermore, a single retardation plate obtained by controlling the birefringence of the material, or a combination of a quarter wavelength retardation plate and a half wavelength retardation plate can be used. Such a phase difference plate may be externally attached to the exit of the projector 21 or may be incorporated in the projector 21. When a CRT or DLP projector is used as the projector 21, the light emitted from the projector 21 is non-polarized light. Therefore, when the circularly polarized light is emitted, a linearly polarizing plate and a phase difference are used. It is necessary to arrange a circularly polarizing plate made of a plate. In this case, although the light quantity of the projector 21 itself is halved, the stray light caused by the light having a polarization component different from the polarization component of the light selectively reflected by the polarization selective reflection layers 11-1 and 11-2 of the projection screen 10 is obtained. It is possible to effectively prevent the occurrence of the above and increase the contrast of the image.

  Here, the projector 21 generally realizes color display with light in the wavelength ranges of red (R), green (G), and blue (B), which are the three primary colors of light. The light having a selective reflection center wavelength in the range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm is projected on the basis of the case where light is incident vertically.

  As shown in FIG. 3, the projection system 20 normally includes an illumination light source 23 installed in an illumination light source installation unit 25 such as an indoor ceiling so as to illuminate an observation space where the projection screen 10 is installed. It has become.

  Here, the illumination light 34 irradiated from the illumination light source 23 toward the projection screen 10 is diffused among the polarized light (right circularly polarized light and left circularly polarized light) reflected by the polarization selective reflection layers 11-1 and 11-2. It is preferable to have the same polarization component as the polarization component of the polarized light having a smaller angle (for example, right circularly polarized light). As a result, the illumination light 34 incident on the projection screen 10 from an oblique direction is diffusely reflected by the polarization selective reflection layers 11-1 and 11-2, but has high directivity, so that the reflected light 43 is specularly reflected. Is reflected in a direction different from the observation direction. For this reason, since the illumination light 34 overlaps the image light 31 effectively even under bright ambient light where the illumination light 34 exists, the contrast of the image can be improved.

  The polarization state of the illumination light 34 emitted from the illumination light source 23 can be controlled by providing a polarizing film 24 that transmits left circularly polarized light in the vicinity of the illumination light source 23. Here, as the polarizing film 24, an absorption-type circularly polarizing plate or a polarizing separation plate (reflection-type circularly polarizing plate) can be used. As the polarization separation plate, a circular polarization separation plate using a cholesteric liquid crystal layer or a retardation plate for converting linearly polarized light into circularly polarized light on the output side of the linearly polarized light separation plate is used. it can. Note that such a polarization separation plate is preferable in the sense that the loss of light amount is smaller than that of the absorption-type circularly polarizing plate.

  The illumination light 34 emitted from the illumination light source 23 is substantially the same as the wavelength dispersion of the right circularly polarized light and the left circularly polarized light reflected by the polarization selective reflection layer 11-1 and the second polarization selective reflection layer 11-2. It is preferable to have the same wavelength dispersion. That is, the illumination light 34 preferably has a selective reflection center wavelength in the range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm. Here, the illumination light source 23 irradiates the projection screen 10 with illumination light 34 from an oblique direction, while the projector 21 irradiates the projection screen 10 with image light 31 from the illumination direction. That is, since the illumination light 34 enters the projection screen 10 at an angle different from that of the image light 31, the wavelength of the light reflected by each of the polarization selective reflection layers 11-1 and 11-2 is the incident angle. It will shift due to the difference. Specifically, the wavelength λ (θ) of light when the light incident at the incident angle θ is reflected by the polarization selective reflection layers 11-1 and 11-2 is λ (θ) = λ (0) × The illumination light 34 incident from an oblique direction is shifted to the short wavelength side. For this reason, the reflectance of the illumination light 34 reflected by each of the polarization selective reflection layers 11-1 and 11-2 is lower than the reflectance of the image light 31, and does not hinder the visibility of the image.

  Hereinafter, the details of the respective polarization selective reflection layers 11-1 and 11-2 of the projection screen 10 shown in FIGS. 1 and 2 will be described.

  Each of the polarization selective reflection layers 11-1 and 11-2 is made of a liquid crystalline composition exhibiting cholesteric regularity, and the director of the liquid crystal molecules is continuous in the thickness direction of the layer as the physical molecular arrangement of the liquid crystal molecules. It has a spiral structure that rotates.

  Then, each of the polarization selective reflection layers 11-1 and 11-2 separates a circularly polarized component in one direction and a circularly polarized component in the opposite direction based on the physical molecular arrangement of the liquid crystal molecules. It has a polarization separation characteristic. That is, in each of the polarization selective reflection layers 11-1 and 11-2, the unpolarized light incident along the spiral axis is separated into two polarized light (right circularly polarized light and left circularly polarized light), Is transmitted and the rest is reflected. This phenomenon is known as circular dichroism, and when a spiral direction in the spiral structure of liquid crystal molecules is appropriately selected, a circularly polarized component having the same optical rotation direction as this spiral direction is selectively reflected.

In this case, the maximum optical rotation light scattering occurs at the wavelength λ ₀ of the following equation (1).

λ ₀ = nav · p (1)
Here, p is the helical pitch length in the helical structure of the liquid crystal molecules (the length per pitch of the molecular helix of the liquid crystal molecules), and nav is the average refractive index in a plane orthogonal to the helical axis.

  Further, the wavelength bandwidth Δλ of the reflected light at this time is expressed by the following equation (2). Here, Δn is a birefringence value.

Δλ = Δn · p (2)
That is, in FIG. 5, unpolarized light (the right circularly polarized light 31R and the left circularly polarized light 31L within the selective reflection wavelength region) incident from the observer (upper side of the drawing) side of each of the polarization selective reflection layers 11-1 and 11-2. The right circularly polarized light 32R and the left circularly polarized light 32L) outside the selective reflection wavelength region are centered on the selective reflection center wavelength λ ₀ in the polarization selective reflection layers 11-1 and 11-2 according to the polarization separation characteristics as described above. One circularly polarized light component (for example, the right circularly polarized light 31R within the selective reflection wavelength region) belonging to the range of the selected wavelength bandwidth Δλ (the selective reflection wavelength region) is reflected as the reflected light 33 and other light (for example, within the selective reflection wavelength region). Left circularly polarized light 31L, right circularly polarized light 32R and left circularly polarized light 32L) outside the selective reflection wavelength region are transmitted.

  The cholesteric liquid crystal structure of each of the polarization selective reflection layers 11-1 and 11-2 includes a plurality of helical structure regions 30 having different directions of the helical axis L as shown in FIG. . The light that is selectively reflected (reflected light 33) is diffused by such structural nonuniformity of the cholesteric liquid crystal structure. Here, the state in which the cholesteric liquid crystal structure has structural inhomogeneity refers to a state in which the direction of the helical axis L of the helical structure region 30 included in the cholesteric liquid crystal structure varies, as well as a nematic layer surface (die of liquid crystal molecules). A cross-sectional TEM photograph of a dyed cholesteric liquid crystal structure film in which at least a part of the surface is the same in the XY directions) is not parallel to the surfaces of the polarization selective reflection layers 11-1 and 11-2 A state in which a continuous curve of layers appearing in a shading pattern when taken is not parallel to the substrate surface). Further, the “diffusion” caused by the structural non-uniformity of the cholesteric liquid crystal structure is reflected by the projection screen 10 including the respective polarization selective reflection layers 11-1 and 11-2. It means expanding the image light to such an extent that the observer can recognize it as an image.

  On the other hand, the general cholesteric liquid crystal structure is in a planar alignment state, and as shown in FIG. 6B, the direction of the spiral axis L of each helical structure region 30 included in the cholesteric liquid crystal structure is all layers. The light that is selectively reflected (reflected light 36) is specularly reflected.

  The spiral structure region 30 included in the cholesteric liquid crystal structure of each of the polarization selective reflection layers 11-1 and 11-2 is a specific wavelength region that covers only a part of the visible light region (for example, a wavelength region of 400 to 700 nm). The wavelength region having a reflection intensity of more than half of the maximum reflection intensity of each of the polarization selective reflection layers 11-1 and 11-2 is a visible light region (for example, 400 to 700 nm). It is preferable to have a specific helical pitch length so that it is only a part of the (wavelength range). More specifically, the cholesteric liquid crystal structures of the polarization selective reflection layers 11-1 and 11-2 only emit light in a wavelength region corresponding to the wavelength region of the image light 31 projected by the projector 21 such as a liquid crystal projector. It is preferable to have at least two types of helical pitch lengths that are discontinuously different so as to selectively reflect. In general, the projector 21 realizes color display with light in the wavelength ranges of red (R), green (G), and blue (B), which are the three primary colors of light. -1 and 11-2 are selectively reflected so that light having a selective reflection center wavelength in the range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm is selectively reflected on the basis of the case where the light is perpendicularly incident on In addition, the helical pitch length of the cholesteric liquid crystal structure may be determined.

  In addition, 430-460 nm, 540-570 nm, and 580-620 nm used as a wavelength range of red (R), green (G), and blue (B) are color filters used for a display that expresses white by the three primary colors of light. This is a general wavelength range for light sources and light sources. Here, each color of red (R), green (G), and blue (B) is represented as a bright line having a peak at a specific wavelength (for example, green (G) is typically 550 nm). However, such a bright line has a certain width, and since there is a difference in wavelength depending on the design of the apparatus and the type of light source, it is preferable that each color has a wavelength bandwidth of 30 to 40 nm. In addition, when the wavelength range of each color of red (R), green (G), and blue (B) is set outside the above-described range, white cannot be expressed, and white is yellowish white Or reddish white.

  Here, when the wavelength regions of red (R), green (G), and blue (B) are represented as selective reflection wavelength regions that are independent of each other, the cholesteric of each polarization selective reflection layer 11-1, 11-2. The liquid crystal structure preferably has three different helical pitch lengths that are discontinuously different. The red (R) and green (G) wavelength ranges may be included in the wavelength bandwidth of the selective reflection wavelength range with one spiral pitch length. In this case, the cholesteric liquid crystal structure is discontinuous. It is preferable to have two different helical pitch lengths.

  When the cholesteric liquid crystal structures of the polarization selective reflection layers 11-1 and 11-2 have two or more types of helical pitch lengths that are discontinuously different, the polarization selective reflection layers 11-1 and 11-2 are In addition, at least two or more partially selective reflection layers having different helical pitch lengths can be stacked on each other. Specifically, as shown in FIG. 4, a partial selective reflection layer 11 a-1 (11 a-2) that selectively reflects light in the blue (B) wavelength region and light in the green (G) wavelength region. A selective reflection layer 11b-1 (11b-2) that selectively reflects light, and a partial selective reflection layer 11c-1 (11c-2) that selectively reflects light in the red (R) wavelength region, It is good to laminate | stack in order from the support base material 12 side. The order of stacking the partial selective reflection layers 11a-1, 11b-1, 11c-1 (11a-2, 11b-2, 11c-2) is not necessarily limited to this. In FIG. 4, the partial selective reflection layers 11a-1, 11b-1, and 11c-1 (11a-2, 11b-2, and 11c-2) are polarized light selections shown in FIGS. Similar to the reflective layer 11-1 (11-2), it has a cholesteric liquid crystal structure that selectively reflects light of a specific polarization component (for example, right circularly polarized light or left circularly polarized light), and its structural nonuniformity Thus, a cholesteric liquid crystal structure that diffuses selectively reflected light is provided. Here, the polarization components of the light selectively reflected by the partial selective reflection layers 11a-1, 11b-1, and 11c-1 are the same, and the partial selective reflection layers 11a-2 and 11b-2. , 11c-2, the polarization components of the light selectively reflected are also the same.

  The polarization selective reflection layers 11-1, 11-2 (or the partial selective reflection layers 11a-1, 11b-1, 11c-1, 11a- constituting the polarization selective reflection layers 11-1, 11-2). 2, 11 b-2, 11 c-2) has a thickness that reflects approximately 100% of light in a specific polarization state that is selectively reflected (a size that saturates the reflectivity). It is preferable. This is because video light cannot be efficiently reflected if the reflectance is less than 100% with respect to light of a specific polarization component that is selectively reflected (for example, right circularly polarized light). The polarization selective reflection layers 11-1, 11-2 (or the partial selective reflection layers 11a-1, 11b-1, 11c-1, 11a- constituting the polarization selective reflection layers 11-1, 11-2). 2, 11b-2, 11c-2) directly depends on the number of helical pitches, but if the helical pitch length is fixed, the polarization selective reflection layer or each It depends on the thickness of the partially selective reflection layer. Specifically, in order to obtain a reflectance of 100%, it is said that about 4 to 8 pitches are necessary. For example, although it depends on the type of material of the liquid crystalline composition and the selective reflection wavelength region, for example, red (R ), Green (G), and blue (B) in one wavelength of the partial selective reflection layer 11a-1, 11b-1, 11c-1, 11a-2, 11b-2, 11c. -2 requires a thickness of about 1 to 10 μm. On the other hand, the thicknesses of the partial selective reflection layers 11a-1, 11b-1, 11c-1, 11a-2, 11b-2, and 11c-2 are not as good as they are thick. The above-described range is appropriate because it is difficult to control the above, unevenness occurs, and the degree of light absorption by the material itself increases.

  In addition, in the projection screen 10 shown in FIG. 4, between the support base material 12 and the 2nd polarization selective reflection layer 11-2 (or the partial selective reflection layer 11a-2 which comprises the 2nd polarization selective reflection layer 11-2). An intermediate layer such as an easy-adhesion layer may be provided between the adjacent partial selective reflection layers, thereby forming the first polarization selective reflection layer 11-1 (or the first polarization selective reflection layer 11-1). The partial selective reflection layers 11a-1, 11b-1, 11c-1) and the second polarized light selective reflection layer 11-2 (or the partial selective reflection layers 11a-2 constituting the second polarized light selective reflection layer 11-2). , 11b-2, 11c-2) for controlling the alignment state of the cholesteric liquid crystal structure and between the partially selective reflection layers 11a-1, 11b-1, 11c-1, 11a-2, 11b-2, 11c-2. It becomes possible to improve the adhesiveness. In addition, you may make it provide a barrier layer as an intermediate | middle layer mentioned above. In this case, even when another partial selective reflection layer is directly laminated on one partial selective reflection layer, it is possible to effectively prevent the liquid crystalline composition from being mixed between adjacent partial selective reflection layers. As a result, better optical properties can be obtained.

  Next, the support base 12 will be described.

  The support base 12 is for supporting the polarization selective reflection layers 11-1 and 11-2, and can be formed using a material such as a plastic film, metal, paper, cloth, or glass.

  Here, the support substrate 12 may include a light absorption layer that absorbs light in the visible light range. Specifically, for example, the support base 12 is formed using an acrylic plate or a plastic film (for example, a black PET film kneaded with carbon) in which a black pigment is kneaded (in this case, the support base 12 Or a light absorption layer made of a black pigment or the like may be formed on the surface of either side of a transparent support film such as a plastic film. Accordingly, light that should not be reflected as reflected light among unpolarized light incident from the viewer side of the projection screen 10 (such as right circularly polarized light and left circularly polarized light outside the selective reflection wavelength region), or the projection screen 10. By absorbing the light incident from the back side, it is possible to effectively prevent the occurrence of reflected light caused by ambient light such as external light and illumination light, and stray light caused by image light.

  The thickness of the support base 12 is preferably 15 to 300 μm, more preferably 25 to 100 μm, considering that it can be wound up. On the other hand, when the support substrate 12 does not necessarily require flexibility as in the case of being used as a panel, the thickness can be increased without limitation.

  The plastic film used as the material for the support substrate 12 includes polycarbonate polymers, polyester polymers such as polyarylate and polyethylene terephthalate, polyimide polymers, polysulfone polymers, and polyethersulfone polymers. , Polystyrene polymers, polyolefin polymers such as polyethylene and polypropylene, polyvinyl alcohol polymers, cellulose acetate polymers, polyvinyl chloride polymers, polyacrylate polymers, polymethyl methacrylate polymers, etc. A film made of a thermoplastic polymer or the like can be used. In addition, the material of the support base material 12 is not limited to this, As above-mentioned, materials, such as a metal, a paper material, a cloth material, glass, can also be used.

  It should be noted that the polarization selective reflection layers 11-1 and 11-2 (or the partial selective reflection layers 11a-1, 11b-1, and 11c constituting the polarization selective reflection layers 11-1 and 11-2 on the support base 12 are provided. -1, 11a-2, 11b-2, 11c-2), as described later, after applying a liquid crystalline composition exhibiting cholesteric regularity, an alignment treatment and a curing treatment are performed. It is common.

  In this case, each polarization selective reflection layer 11-1, 11-2 (or each partial selective reflection layer 11a-1, 11b-1, 11c-1, 11a constituting each polarization selective reflection layer 11-1, 11-2). -2, 11b-2, 11c-2) Since the cholesteric liquid crystal structure must be controlled so as not to be in the planar alignment state, the support substrate 12 is aligned on the surface on which the liquid crystalline composition is applied. It is preferable to use one having no function. However, even if the material on the surface of the support substrate 12 on which the liquid crystalline composition is applied has an orientation ability on the surface, such as a stretched film, the support substrate 12 By subjecting the surface of the stretched film to surface treatment, and controlling the material of the liquid crystalline composition, the process conditions for aligning the liquid crystalline composition, etc., each of the polarization selective reflection layers 11-1 and 11-2. (Or the cholesteric liquid crystal structure of the partial selective reflection layers 11a-1, 11b-1, 11c-1, 11a-2, 11b-2, 11c-2 constituting the respective polarization selective reflection layers 11-1, 11-2) Can be controlled so as not to be in the planar alignment state.

  When the surface of the support substrate 12 on which the liquid crystalline composition is applied has orientation ability, the polarization selective reflection layer 11-2 (or polarization selection) provided on the support substrate 12 side. By providing an intermediate layer such as an easy-adhesion layer between 11a-2) constituting the reflective layer 11-2 and the support substrate 12, each polarization selective reflection layer 11-1, 11-2 (or each polarization selection) Control the alignment state of the cholesteric liquid crystal structure of the partially selective reflection layers 11a-1, 11b-1, 11c-1, 11a-2, 11b-2, 11c-2) constituting the reflection layers 11-1, 11-2. The polarization selective reflection layers 11-1, 11-2 (or the partial selective reflection layers 11a-1, 11b-1, 11c-1, 11a- constituting the polarization selective reflection layers 11-1, 11-2). 2,11b-2, 11c-2) among the cholesteric liquid crystal structures It is also possible to directors of the liquid crystal molecules near the interface between the layers is to face in multiple directions. In addition, when providing intermediate | middle layers, such as an easily bonding layer, the adhesiveness between the polarization selective reflection layer 11-2 (or 11a-2 which comprises the polarization selective reflection layer 11-2) and the support base material 12 is provided. It can also be increased. In addition, as such an intermediate | middle layer, what is necessary is just to be able to acquire high adhesiveness with respect to both the material of the polarization selective reflection layer 11 and the material of the support base material 12, and generally uses what is marketed. Can do. Specific examples include PET film A4100 with an easy-adhesion layer manufactured by Toyobo Co., Ltd., and easy-adhesive materials AC-X, AC-L, and AC-W manufactured by Panac. The intermediate layer can also be used as a light absorption layer that incorporates a black pigment or the like and absorbs light in the visible light range.

  Here, the surface of the support substrate 12 does not have the orientation ability, and the polarization selective reflection layer 11-2 (or the partial selective reflection layer 11a-2 constituting the polarization selective reflection layer 11-2) and the support group. In the case where the adhesion with the material 12 is also sufficiently high, it is not always necessary to provide an intermediate layer. Moreover, as a method for improving the adhesiveness between the polarization selective reflection layer 11-2 (or the partial selective reflection layer 11a-2 constituting the polarization selective reflection layer 11-2) and the support substrate 12, a corona treatment is performed. Process methods such as UV cleaning can also be used.

  Next, a method for manufacturing the projection screen 10 as described above will be described.

  First, the support base material 12 on which the polarization selective reflection layers 11-1 and 11-2 are laminated is prepared. Further, if necessary, an intermediate layer such as an easy adhesion layer is laminated on the surface of the support base 12 on the side where the polarization selective reflection layers 11-1 and 11-2 are provided. At this time, the surface of the support substrate 12 on which the liquid crystalline composition is applied (or the surface when there is an intermediate layer) is made to have no orientation ability.

  Next, by applying a liquid crystalline composition exhibiting cholesteric regularity in a specific spiral winding direction (for example, left-handed) on the support substrate 12 thus prepared, the alignment treatment and the curing treatment are performed. The polarization selective reflection layer 11-2 is laminated (fixed). Furthermore, after laminating the polarization selective reflection layer 11-2 on the support base 12 in this manner, a spiral different from the spiral winding direction of the polarization selective reflection layer 11-2 is formed on the polarization selective reflection layer 11-2. After applying a liquid crystalline composition exhibiting cholesteric regularity in the winding direction (for example, right-handed), the polarization selective reflection layer 11-1 is laminated (fixed) by performing an alignment treatment and a curing treatment.

  Hereinafter, details of each process (application process, alignment process process, and curing process process) for laminating (adhering) the polarization selective reflection layers 11-1 and 11-2 will be described.

(Coating process)
In the coating step, a liquid crystalline composition exhibiting cholesteric regularity in a specific spiral winding direction (left-handed or right-handed) on the support base 12 or the polarization selective reflection layer 11-2 laminated on the support base 12 Is applied to form a cholesteric liquid crystal layer. At this time, any existing method can be used as a method of applying the liquid crystalline composition. Specifically, a roll coating method, a gravure coating method, a bar coating method, a slide coating method, a die coating method, a slit coating method, a dipping method, or the like can be used. Moreover, when using a plastic film as the support base material 12, film coating by a so-called roll-to-roll system can be used.

  In addition, as a liquid crystalline composition apply | coated on the polarization | polarized-light selective reflection layer 11-2 laminated | stacked on the support base material 12 or the support base material 12, using a chiral nematic liquid crystal and a cholesteric liquid crystal which show a cholesteric regularity is used. it can. Such a material is not particularly limited as long as it is a liquid crystal material capable of forming a cholesteric liquid crystal structure, and in particular, a polymerizable liquid crystal material having a polymerizable functional group at both ends of the molecule. It is preferable for obtaining the polarization selective reflection layers 11-1 and 11-2 which are optically stable after curing.

  Hereinafter, the case where a chiral nematic liquid crystal is used as the liquid crystalline composition will be described as an example. The chiral nematic liquid crystal is a mixture of a polymerizable liquid crystal material exhibiting nematic regularity and a chiral agent. Here, the chiral agent is for controlling the helical pitch length of the polymerizable liquid crystal material exhibiting nematic regularity so that the liquid crystalline composition exhibits cholesteric regularity as a whole. The selective reflection center wavelength caused by the molecular structure of the polymerizable liquid crystal material can be controlled by changing the chiral power by changing the type of the chiral agent or by changing the concentration of the chiral agent. Further, by changing the kind of the chiral agent, the spiral winding direction of the cholesteric regularity exhibited by the liquid crystalline composition can be set to either right-handed or left-handed. In addition, a polymerization initiator, a leveling agent, and other suitable additives are added to such a liquid crystalline composition.

Examples of polymerizable liquid crystal materials exhibiting nematic regularity include, for example, compounds represented by the following general formula (1) and compounds represented by the following formulas (2-i) to (2-xi). Can be mentioned. These compounds can be used alone or in combination.

In the above general formula (1), R ¹ and R ² each represent hydrogen or a methyl group, but both R ¹ and R ² are preferably hydrogen because of the wide temperature range showing the liquid crystal phase. X may be hydrogen, chlorine, bromine, iodine, an alkyl group having 1 to 4 carbon atoms, a methoxy group, a cyano group, or a nitro group, but is preferably a chlorine or methyl group. Moreover, in the said General formula (1), a and b which show the chain length of the alkylene group which is a spacer of the (meth) acryloyloxy group and aromatic ring of the molecular chain both ends are arbitrary in the range of 2-12, respectively. Although it can take an integer, it is preferably in the range of 4 to 10, and more preferably in the range of 6 to 9. The compound of the general formula (1) in which a = b = 0 is poor in stability, is susceptible to hydrolysis, and has high crystallinity. In addition, the compound of the general formula (1) in which a and b are each 13 or more has a low isotropic transition temperature (TI). For this reason, both of these compounds are not preferable because the temperature range in which the liquid crystal phase is exhibited is narrow.

  In the above, examples of polymerizable liquid crystal monomers have been described as polymerizable liquid crystal materials exhibiting nematic regularity, but not limited thereto, polymerizable liquid crystal oligomers, polymerizable liquid crystal polymers, liquid crystal polymers, etc. It is also possible to use it. Such a polymerizable liquid crystal oligomer, polymerizable liquid crystal polymer and liquid crystal polymer can be appropriately selected from those conventionally proposed.

  On the other hand, a chiral agent is a low molecular compound having an optically active site, and is mainly a compound having a molecular weight of 1500 or less. The chiral agent is mainly used for the purpose of inducing a helical structure in the positive uniaxial nematic regularity expressed by the polymerizable liquid crystal material exhibiting nematic regularity. As long as this purpose is achieved, it is compatible with a polymerizable liquid crystal material exhibiting nematic regularity in a solution state or a molten state, without impairing the liquid crystal property of the polymerizable liquid crystal material exhibiting nematic regularity, The kind of the low molecular compound as the chiral agent is not particularly limited as long as it can induce a desired helical structure.

  In addition, the chiral agent used for inducing a helical structure in the liquid crystal in this way needs to have at least some chirality in the molecule. Accordingly, the chiral agent used here includes, for example, a compound having one or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine or chiral sulfoxide, or a cumulene. And compounds having an optically active moiety having axial asymmetry such as binaphthol. More specifically, a commercially available chiral nematic liquid crystal (for example, chiral dopant liquid crystal S-811 (manufactured by Merck)) can be mentioned.

However, depending on the properties of the selected chiral agent, the nematic regularity formed by the polymerizable liquid crystal material exhibiting nematic regularity, the orientation deterioration, or the liquid crystallinity when the chiral agent is non-polymerizable. There exists a possibility of causing the fall of the sclerosis | hardenability of a composition, and the fall of the reliability of the film after hardening. Furthermore, the use of a large amount of a chiral agent having an optically active site leads to an increase in the cost of the liquid crystal composition. Therefore, when a polarization selective reflection layer having a cholesteric regularity with a short helical pitch length is formed, a chiral agent having an optically active site to be contained in the liquid crystalline composition is a chiral agent having a large effect of inducing a helical structure. It is preferable to select an agent. Specifically, it is preferable to use a low molecular compound having axial asymmetry in the molecule as represented by the following general formula (3), (4) or (5). .

In the general formula (3) or (4), R ⁴ represents hydrogen or a methyl group. Y is any one of formulas (i) to (xxiv) shown above, and among them, any one of formulas (i), (ii), (iii), (v), and (vii) Preferably there is. Moreover, although c and d which show the chain length of an alkylene group can each take arbitrary integers in the range of 2-12, it is preferable that it is the range of 4-10, and is the range of 6-9. Is more preferable. The compound of the above general formula (3) or (4) in which the value of c or d is 0 or 1 lacks stability, is susceptible to hydrolysis, and has high crystallinity. On the other hand, a compound having a value of c or d of 13 or more has a low melting point (Tm). In these compounds, compatibility with a polymerizable liquid crystal material exhibiting nematic regularity is lowered, and phase separation or the like may occur depending on the concentration.

  In addition, such a chiral agent does not need to have polymerizability in particular. However, when the chiral agent has polymerizability, it is polymerized with a polymerizable liquid crystal material exhibiting nematic regularity, and the cholesteric regularity is stably fixed, so in terms of thermal stability, etc. Highly preferred. In particular, it is preferable to have a polymerizable functional group at both ends of the molecule in order to obtain the polarization selective reflection layers 11-1 and 11-2 having good heat resistance.

  The amount of the chiral agent contained in the liquid crystal composition is determined in consideration of the ability to induce a helical structure and the cholesteric liquid crystal structure of the finally obtained polarization selective reflection layer. Specifically, although it varies greatly depending on the material of the liquid crystal composition used, 0.01 to 60 parts by weight, preferably 0.1 to 40 parts by weight, per 100 parts by weight of the total amount of the liquid crystal composition. More preferably, it is selected in the range of 0.5 to 30 parts by weight, most preferably 1 to 20 parts by weight. When the content of the chiral agent is less than the above range, sufficient cholesteric regularity may not be imparted to the liquid crystal composition. When the content exceeds the above range, the alignment of the liquid crystal molecules is inhibited. There is a risk of adverse effects when cured by actinic radiation.

  The liquid crystalline composition can be applied as it is on the support substrate 12, but it is dissolved in an appropriate solvent such as an organic solvent for the purpose of adjusting the viscosity to a coating apparatus or obtaining a good alignment state. An ink may be used.

  Such a solvent is not particularly limited as long as it can dissolve the polymerizable liquid crystal material as described above, but is preferably one that does not erode the support substrate 12. Specific examples include acetone, 3-methoxybutyl acetate, diglyme, cyclohexanone, tetrahydrofuran, toluene, xylene, chlorobenzene, methylene chloride, methyl ethyl ketone, and the like. The degree of dilution of the polymerizable liquid crystal material is not particularly limited, but it is 5 to 50%, more preferably 10 in view of the fact that the liquid crystal itself is a material with low solubility and high viscosity. It is preferable to dilute to about 30%.

  As described above, leveling is preferably added to the liquid crystalline composition. The leveling agent gives structural nonuniformity to the cholesteric liquid crystal structure of the polarization selective reflection layer (see Japanese Patent Application No. 2003-275290). Here, a predetermined amount is added according to the diffusion characteristics required for the finally obtained polarization selective reflection layer.

  The reason why structural inhomogeneity is given to the cholesteric liquid crystal structure by adding a leveling agent is as follows. That is, when a leveling agent is added to the liquid crystalline composition, the domain of the cholesteric liquid crystal structure in the finally obtained polarization selective reflection layer is affected at the molecular level, and each domain grows. Since the appearance of a non-uniform structure is promoted, the direction of the helical axis of the helical axis structure region in the polarization selective reflection layer is consequently adjusted.

  Here, the amount of the leveling agent added to the liquid crystal composition needs to be determined in consideration of the thickness of the finally obtained polarization selective reflection layer. That is, when a liquid crystalline composition having the same leveling agent content is applied on a support substrate having the same area, the leveling agent contained in the polarization selective reflection layer is increased as the thickness of the resulting polarization selective reflection layer is increased. The amount of the leveling agent contained in the polarization selective reflection layer decreases as the thickness of the polarization selective reflection layer decreases. Accordingly, since the amount of the leveling agent contained in the polarization selective reflection layer differs depending on the thickness of the polarization selective reflection layer, the amount of the leveling agent contained in the liquid crystalline composition is considered in consideration of this point. It is preferable to change the direction of the helical axis of the helical axis structure region in the finally obtained polarization selective reflection layer by a desired angle.

  Specifically, the leveling agent content is applied to the type of leveling agent, the type of polymerizable liquid crystal material contained in the liquid crystalline composition, the type of solvent, and the liquid crystalline composition. Although depending on the type of the supporting substrate, it is preferably in the range of 0.06 to 5 parts by weight, particularly 0.06 to 3 parts by weight, based on 100 parts by weight of the total amount of the polymerizable liquid crystal material. By including the leveling agent in the liquid crystal composition in an amount within the above-described range, the direction of the helical axis of the helical axis structure region in the obtained polarization selective reflection layer is adjusted, and the optimum angle of the helical axis is obtained. This is because a cholesteric liquid crystal structure can be obtained. Moreover, it is because there exists a possibility that the liquid crystallinity of a polymeric liquid crystal material may not express when content of a leveling agent exceeds the range mentioned above.

  In addition, content of the leveling agent mentioned above is a thing in case the support base material with which a liquid crystalline composition is apply | coated does not have alignment ability. That is, when the supporting base material has orientation ability, the polymerizable liquid crystal material is oriented by the orientation ability of the supporting base material. Therefore, even if a leveling agent is added, there is structural nonuniformity in the cholesteric liquid crystal structure. It may not be given. In this case, the content of the leveling agent that does not give structural nonuniformity to the cholesteric liquid crystal structure is excluded from the above range.

  The leveling agent used here includes (1) cationic surfactants such as imidazoline, quaternary ammonium salts, alkylamine oxides, polyamine derivatives, (2) polyoxyethylene-polyoxypropylene condensates, first Secondary or secondary alcohol ethoxylate, alkylphenol ethoxylate, polyethylene glycol and its esters, sodium lauryl sulfate, ammonium lauryl sulfate, lauryl sulfate amines, alkyl-substituted aromatic sulfonates, alkyl phosphates, aliphatic or aromatic sulfones Anionic surfactants such as acid formalin condensate, (3) amphoteric surfactants such as laurylamidopropyl betaine, laurylaminoacetic acid betaine, (4) polyethylene glycol fatty acid esters, polyoxye Nonionic surfactants such as lenalkylamines, (5) perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl trimethyl ammonium salts, perfluoroalkyl groups and hydrophilicity Fluorine-containing surfactants such as group-containing oligomers, perfluoroalkyl / lipophilic group-containing oligomers perfluoroalkyl group-containing urethane, (6) polyacrylic acid, acrylic acid copolymer, methacrylic acid, methacrylic acid copolymer, etc. Examples include acrylic surfactants. Among these, acrylic surfactants are preferably used.

(Orientation process)
In the coating step described above, after applying the liquid crystalline composition on the support substrate 12 and forming the cholesteric liquid crystal layer, in the alignment treatment step, the cholesteric liquid crystal layer is maintained at a predetermined temperature at which the cholesteric liquid crystal structure is expressed, The liquid crystal molecules in the cholesteric liquid crystal layer are aligned.

  Note that the cholesteric liquid crystal structures of the polarization selective reflection layers 11-1 and 11-2 to be finally obtained are not in the planar alignment state, but as shown in FIG. Although the orientation of L varies in the layer, the orientation treatment is necessary even in this case. That is, an alignment process that aligns the directors of liquid crystal molecules having a cholesteric liquid crystal structure in a certain direction on the support substrate 12 is not required, but an alignment process that forms a plurality of helical structure regions 30 in the cholesteric liquid crystal structure. Is necessary.

  Here, when the cholesteric liquid crystal layer formed on the support substrate 12 is maintained at a predetermined temperature at which the cholesteric liquid crystal structure is developed, the cholesteric liquid crystal layer exhibits a liquid crystal phase, and the liquid crystal molecules are self-assembled by the self-integrating action of the liquid crystal molecules themselves. The spiral structure is formed by continuously rotating the director in the thickness direction of the layer. And the cholesteric liquid crystal structure expressed in such a liquid crystal phase can be fixed by curing the cholesteric liquid crystal layer by a method as described later.

  In addition, when the solvent is contained in the liquid crystalline composition apply | coated on the support base material 12, such an alignment process process is normally performed with the drying process for removing a solvent. In order to remove the solvent, a drying temperature of 40 to 120 ° C., preferably 60 to 100 ° C. is suitable. The drying time (heating time) exhibits a cholesteric liquid crystal structure, and the solvent is substantially removed. For example, it is preferably 15 to 600 seconds, and more preferably 30 to 180 seconds. In addition, when it turns out that an orientation state is inadequate after drying, it is good to extend a heating time suitably. In addition, when using the vacuum drying method in such a drying process, it is preferable to perform a separate heat treatment for the alignment process.

(Curing process)
After aligning the liquid crystal molecules in the cholesteric liquid crystal layer in the alignment treatment step described above, in the curing treatment step, the cholesteric liquid crystal layer is cured to fix the cholesteric liquid crystal structure expressed in the liquid crystal phase.

  Here, as a method used in the curing treatment step, (1) a method of drying a solvent in the liquid crystalline composition, (2) a method of polymerizing liquid crystal molecules in the liquid crystalline composition by heating, (3) radiation A method of polymerizing liquid crystal molecules in the liquid crystalline composition by irradiation of (4) and (4) a method combining these methods can be used.

  Among these, the method (1) is a method suitable when a liquid crystal polymer is used as a polymerizable liquid crystal material exhibiting nematic regularity contained in a liquid crystalline composition that is a material of a cholesteric liquid crystal layer. In this method, the liquid crystal polymer is applied to the support substrate 12 in a state dissolved in a solvent such as an organic solvent. In this case, the cholesteric regularity is obtained simply by removing the solvent by a drying process. A solidified cholesteric liquid crystal layer is formed. In addition, about the kind of solvent, drying conditions, etc., what was described in the apply | coating process and orientation process mentioned above can be used.

  The method (2) is a method of curing the cholesteric liquid crystal layer by thermally polymerizing liquid crystal molecules in the liquid crystal composition by heating. In this method, the bonding state of the liquid crystal molecules changes depending on the heating (firing) temperature. Therefore, if there is temperature unevenness in the plane of the cholesteric liquid crystal layer during heating, physical properties such as film hardness and optical characteristics are uneven. Here, in order to keep the film hardness distribution within ± 10%, the heating temperature distribution is also preferably within ± 5%, and more preferably within ± 2%.

  The method for heating the cholesteric liquid crystal layer formed on the support substrate 12 is not particularly limited as long as the uniformity of the heating temperature can be obtained, and it can be held in close contact with the hot plate, It is possible to use a method in which a slight air layer is provided between them and held parallel to the hot plate. Further, it may be a method in which the entire specific space such as an oven is heated or passed through the apparatus. In the case of using a film coater or the like, it is preferable to lengthen the drying zone so that a sufficient heating time can be taken.

  In general, a heating temperature of 100 ° C. or higher is required as the heating temperature, but it is preferably about 150 ° C. due to the heat resistance of the support base 12. However, if a film or the like specialized for heat resistance is used as the material of the support substrate 12, heating at a high temperature of 150 ° C. or higher is also possible.

  The method (3) is a method of curing the cholesteric liquid crystal layer by photopolymerizing liquid crystal molecules in the liquid crystalline composition by irradiation with radiation. In this method, an electron beam, ultraviolet rays, or the like can be appropriately used as radiation according to conditions. Usually, ultraviolet rays are preferably used from the viewpoint of easiness of the apparatus, and the wavelength is 250 to 400 nm. In the case where the cholesteric liquid crystal layer is cured by ultraviolet rays, oxygen inhibits radicals and decreases the reactivity of liquid crystal molecules, so that an inert gas such as nitrogen or argon (oxygen concentration is 5% or less, and further 0 It is preferable to cure within 5% or less. Here, when ultraviolet rays are used, it is preferable that a photopolymerization initiator is added to the liquid crystalline composition.

  Examples of the photopolymerization initiator added to the liquid crystal composition include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, benzoyl methyl benzoate, 4-benzoyl-4'- Methyldiphenyl sulfide, benzylmethyl ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-methoxybenzophenone, methylobenzoylpho Mate, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1- ON, 1- ( -Dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) 2-hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxy Examples include thioxanthone. In addition to the photopolymerization initiator, it is also possible to add a sensitizer as long as the object of the present invention is not impaired.

  In addition, content of the photoinitiator added to a liquid crystalline composition is 0.01 to 20 weight%, Preferably it is 0.1 to 10 weight%, More preferably, it is the range of 0.5 to 5 weight%. Preferably there is.

  The polarization selective reflection layers 11-1 and 11-2 made of a single cholesteric liquid crystal layer are formed on the support substrate 12 by performing the above-described series of steps (coating step, alignment step and curing step). However, by repeating the above-described series of steps, a plurality of cholesteric liquid crystal layers (partial selective reflection layers 11a-1, 11b-1, 11c-1 (11a-2, 11b-2, 11c- It is possible to form the polarization selective reflection layer 11-1 (11-2) comprising 2)). Thereby, for example, as shown in FIG. 4, as the polarization selective reflection layer 11-1 (11-2), a partial selective reflection layer 11a-1 (11a) that selectively reflects light in the blue (B) wavelength region. -2), a partial selective reflection layer 11b-1 (11b-2) that selectively reflects light in the green (G) wavelength range, and a portion that selectively reflects light in the red (R) wavelength range It is possible to form the polarization selective reflection layer 11-1 (11-2) in which the selective reflection layer 11c-1 (11c-2) is sequentially laminated from the support base material 12 side.

  When the polarization selective reflection layer 11-1 is laminated on the polarization selective reflection layer 11-2, or on the partial selective reflection layer (for example, the partial selective reflection layer 11a-1), the partial selective reflection layer (for example, partial selective reflection). In the case of laminating the layer 11b-1), if the lower cholesteric liquid crystal layer is formed and fixed, the same applies when applying the liquid crystalline composition of the second and subsequent cholesteric liquid crystal layers. This can be done by a technique. In this case, the cholesteric liquid crystal structure (alignment state) of the upper cholesteric liquid crystal layer is a continuation of the cholesteric liquid crystal structure (alignment state) of the lower cholesteric liquid crystal layer, for alignment control between stacked cholesteric liquid crystal layers. There is no need to provide a layer. However, if necessary, an intermediate layer such as an easy adhesion layer may be provided between the cholesteric liquid crystal layers to be laminated. Since the conditions and materials used for the coating process, the alignment process process, and the curing process process when forming the second and subsequent cholesteric liquid crystal layers are as described above, the description thereof is omitted here.

  In addition, in the above, the laminated body of the polarization selective reflection layers 11-1 and 11-2 constituting the projection screen 10 is peeled off from the support base 12 and the laminated body of the polarization selective reflection layers 11-1 and 11-2 alone. Can also be used.

  As described above, according to the present embodiment, in each of the polarization selective reflection layers 11-1 and 11-2, light of different polarization components is selectively reflected at different diffusion angles. The polarization selective reflection layer (polarization selective reflection layer 11-2) having a larger diffusion angle by controlling the polarization state of the ambient light (illumination light 34, etc.) and the image light 31 incident on 11-1 and 11-2. If the image light 31 is reflected and the ambient light (illumination light 34 or the like) is reflected by the polarization selective reflection layer (polarization selective reflection layer 11-1) having a smaller diffusion angle, the projection screen 10 can be reflected. Ambient light (illumination light 34, etc.) incident from an oblique direction is reflected in a direction different from the observation direction in a form close to specular reflection. For this reason, even under bright ambient light where illumination light 34 exists, it is effectively reduced that ambient light (illumination light 34 or the like) overlaps with the image light 31. The brightness of the image becomes darker and the contrast of the image can be improved.

  Moreover, according to this Embodiment, in each polarization selective reflection layer 11-1 and 11-2, the light of a different polarization component is selectively reflected with a different diffusion angle, For example, it has a smaller diffusion angle. The right circular polarized light is reflected by the polarization selective reflection layer (polarization selective reflection layer 11-1), and the left circular polarized light is reflected by the polarization selective reflection layer (polarization selective reflection layer 11-2) having a larger diffusion angle. Then, if the polarization state is controlled so that the image light 31 projected from the projector 21 onto the projection screen 10 becomes right circularly polarized light, the projection screen 10 can be made into a narrow-field screen (narrow viewing angle but a bright screen). ), And a high brightness screen suitable for observation with a small number of people can be obtained. On the other hand, if the polarization state is controlled so that the image light 31 projected from the projector 21 onto the projection screen 10 is left circularly polarized, the projection screen 10 functions as a wide-field screen (screen with a wide viewing angle). It is possible to obtain a screen suitable for observation with a large number of people. Furthermore, if the polarization state is controlled so that the image light 31 projected from the projector 21 onto the projection screen 10 becomes non-polarized light or linearly polarized light, the intermediate between the two screens described above (the narrow-field screen and the wide-field screen). You can get a screen with the characteristics of

  Furthermore, according to the present embodiment, each of the polarization selective reflection layers 11-1 and 11-2 selectively reflects light in a specific wavelength range that covers only a part of the visible light range. Therefore, in the projection screen 10 composed of the polarization selective reflection layers 11-1 and 11-2, the influence of ambient light such as external light and illumination light can be further suppressed, and the contrast of the image can be increased. The sex can be further improved.

  Furthermore, according to the present embodiment, the wavelength dispersion of ambient light (such as illumination light 34) incident on the respective polarization selective reflection layers 11-1 and 11-2 is changed to the respective polarization selective reflection layers 11-1 and 11-. 2 is substantially the same as the chromatic dispersion of the image light 31 reflected at 2, so that the reflectance of the ambient light (illumination light 34, etc.) that shifts to the short wavelength side when incident from an oblique direction is the image. It will be lower than the reflectance of the light 31. For this reason, the influence of environmental light (illumination light 34 etc.) can further be suppressed, the contrast of an image | video can be raised, and the visibility of an image | video can be improved more.

  In the above-described embodiment, the first polarization reflected by the first polarization selective reflection layer 11-1 is right circular polarization, and the second polarization reflected by the second polarization selective reflection layer 11-2. The case of left circularly polarized light has been described as an example, but the first polarized light reflected by the first polarized light selective reflection layer 11-1 is left circular polarized light and is reflected by the second polarized light selective reflection layer 11-2. Of course, the second polarized light may be right circularly polarized light. The first polarized light reflected by the first polarized light selective reflection layer 11-1 and the second polarized light reflected by the second polarized light selective reflection layer 11-2 may have different polarization components, for example, One of the first polarized light and the second polarized light may be circularly polarized light, and the other may be linearly polarized light.

  In the above-described embodiment, the polarization selective reflection layers 11-1 and 11-2 are reflected by changing the spiral winding direction of the cholesteric liquid crystal structure of the polarization selective reflection layers 11-1 and 11-2 themselves. However, the polarization selective reflection layers 11-1 and 11-2 themselves have the same spiral winding direction in the cholesteric liquid crystal structure, and the polarization selective reflection layer 11 is not limited thereto. By arranging a ½λ phase difference plate between −1 and 11-2, the polarized light reflected by the polarization selective reflection layers 11-1 and 11-2 may have different polarization components.

  Furthermore, in the above-described embodiment, the case where the support base 12 of the projection screen 10 includes a light absorption layer that absorbs light in the visible light range has been described as an example. The material 12 may be a transparent substrate that transmits at least part of light in the visible light region. In this case, since the transparency of the projection screen 10 when the image is not displayed is high, the background can be seen through clearly, and it can be used with high design such as being installed in a show window. In addition, an effective eye-catching effect can be produced by switching the viewing angle according to the situation. For this reason, the disadvantages of the conventional information tool using a projector, which could not be seen in a bright environment, can be solved and used effectively in applications such as advertising boards, information bulletin boards, and guide boards. In addition, although the thing with few hazes is preferable as a transparent base material mentioned above, Arbitrary materials, such as an acryl, glass, vinyl chloride, can be used if it is a material which permeate | transmits light. Moreover, the transparent base material mentioned above does not necessarily need to be colorless, and may be colored. Specifically, for example, a colored and transparent plastic plate or glass plate such as brown, blue, or orange used for partitions or windows can be used.

  In the embodiment described above, as the support base 12 of the projection screen 10, a method for applying the liquid crystalline composition on the support base 12, or the polarization selective reflection layer 11 formed on the support base 12. It is preferable to determine an optimum one in relation to the alignment control methods of −1 and 11-2. Specifically, for example, when the liquid crystalline composition is applied onto the support substrate 12 by film coating using a so-called roll-to-roll system, a film-like substrate is used as the support substrate 12. In addition, when the liquid crystalline composition is applied onto the support substrate 12 by single wafer coating, it is preferable to use a plate-like substrate as the support substrate 12. However, if the support substrate 12 finally obtained has various different properties with respect to flatness, bending properties, transparency, light-shielding properties, etc., these properties are used as a single substrate. It is not always necessary to satisfy the above condition, and the support substrate 12 may be configured by a combination of a plurality of substrates. Specifically, for example, after forming a polarization selective reflection layer by applying a liquid crystalline composition on a plastic film, the plastic film is affixed to a highly flat plastic plate, thereby forming the plastic film and the plastic plate. The support base 12 may be configured.

  Next, specific examples of the above-described embodiment will be described.

(Example)
A monomer mixed liquid crystal in which a right-handed chiral agent was added to a main component composed of an ultraviolet curable nematic liquid crystal was dissolved in cyclohexanone to prepare a cholesteric liquid crystal solution 1 having a selective reflection center wavelength at 440 nm. Here, as a nematic liquid crystal, a liquid crystal containing a compound represented by the above chemical formula (2-xi) was used, and as a polymerizable chiral agent, a compound represented by the above chemical formula (5) was used. .

  Furthermore, 5% by weight of a photopolymerization initiator (Ciba Specialty Chemicals) was added to the cholesteric liquid crystal solution 1, and 0.05% by weight of a leveling agent (Bic Chemie) was added.

  Then, the cholesteric liquid crystal solution 1 prepared as described above is formed on the base material (Lumirror / AC-X, manufactured by Panac Co., Ltd.) on which an easy adhesion layer is formed on a 200 mm □ black PET film by a bar coating method. Applied.

  Next, drying and alignment treatment were performed in an oven at 80 degrees for 90 seconds to obtain a cholesteric liquid crystal layer from which the solvent was removed.

Thereafter, the cholesteric liquid crystal layer was irradiated with ultraviolet rays of 365 nm at 50 mW / cm ² for 1 minute in a nitrogen atmosphere to cure the cholesteric liquid crystal layer. The cholesteric liquid crystal structure of the cholesteric liquid crystal layer thus cured was not in the planar alignment state.

  Thus, the first partial selective reflection layer having a selective reflection center wavelength at 440 nm was formed.

  Next, the cholesteric liquid crystal solution 2 is applied directly on the first partial selective reflection layer formed as described above by the same method as the method for forming the first partial selective reflection layer, and then dried. Then, alignment treatment and curing treatment were performed to form a second partial selective reflection layer having a selective reflection center wavelength at 550 nm. The cholesteric liquid crystal solution 2 was prepared in the same manner as the cholesteric liquid crystal solution 1 except that the selective reflection center wavelength was adjusted to 550 nm by adjusting the content of the chiral agent.

  Similarly, a method similar to the method of forming the cholesteric liquid crystal solution 3 directly on the second partial selective reflection layer formed as described above and forming the first and second partial selective reflection layers. Then, drying, alignment treatment and curing treatment were performed to form a second partial selective reflection layer having a selective reflection center wavelength at 600 nm. The cholesteric liquid crystal solution 3 was prepared in the same manner as the cholesteric liquid crystal solutions 1 and 2 except that the selective reflection center wavelength was adjusted to 600 nm by adjusting the content of the chiral agent.

  As described above, a right circularly polarized light selective reflection layer composed of three partial selective reflection layers having selective reflection center wavelengths at 440 nm, 550 nm, and 600 nm was formed. Here, the thickness of each partial selective reflection layer constituting the right circularly polarized light selective reflection layer is 2 μm for the first layer, 3 μm for the second layer, and 4 μm for the third layer. The thickness was 9 μm. Further, the diffusion angle β of the right circularly polarized light selective reflection layer was ± 15 °.

  Next, three types of cholesteric liquid crystal solutions 4, 5, and 6 prepared in the same manner as the cholesteric liquid crystal solutions 1, 2, and 3 for forming each partial selective reflection layer of the right circularly polarized light selective reflection layer are converted into right circularly polarized light. By sequentially applying on the selective reflection layer, and performing drying, orientation treatment and curing treatment, the same method as the method for forming each partial selective reflection layer of the right circularly polarized light selective reflection layer to 440 nm, 550 nm and 600 nm. A left circularly polarized light selective reflection layer composed of three partial selective reflection layers having a selective reflection center wavelength was formed. In addition, each of the cholesteric liquid crystal solutions 4, 5, and 6 except that the added chiral agent is for left-handed use and the content of the added leveling agent is 0.3% by weight. It was prepared in the same manner as the cholesteric liquid crystal solutions 1, 2, and 3. Here, the thickness of each partial selective reflection layer constituting the left circularly polarized light selective reflection layer is 2 μm for the first layer, 3 μm for the second layer, and 4 μm for the third layer. The thickness was 9 μm. The diffusion angle β of the left circularly polarized light selective reflection layer was ± 35 °.

  Thus, a projection screen 1 was obtained in which the right circularly polarized light selective reflection layer and the left circularly polarized light selective reflection layer were laminated on the base material.

(Comparative example)
As a commercially available existing screen, a mat type projection screen 2 (manufactured by OS Co., Ltd.) was prepared.

(Evaluation results)
The projection screen 1 according to the above-described example and the projection screen 2 according to the comparative example were installed so as to be perpendicular to the floor. The projector was placed at a distance of about 2.5 m from the projection screens 1 and 2 in a direction perpendicular to the screen (a direction parallel to the floor). Here, as a projector, a DLP projector (TDP-P5 (J) manufactured by Toshiba) was used. In addition, a circularly polarizing plate was disposed at the exit of the projector by installing a filter holder so that the polarization state of the emitted image light could be controlled.

  The indoor lighting was a white fluorescent lamp, which was arranged so as to enter the projection screens 1 and 2 at an angle of about 50 degrees from the ceiling. This illumination was emitted as right circularly polarized light by a polarizing plate. The brightness just below the projection screens 1 and 2 at this time was 200 lx when measured with a illuminometer manufactured by Topcon Corporation.

  When the image light emitted from the projector is projected on the projection screen 1 arranged in such a situation as left circularly polarized light by the left circularly polarizing plate, the viewing angle is wide and the oblique direction Even when viewed from above, a bright, high-contrast image was obtained. On the other hand, when the image light emitted from the projector is projected on the projection screen 1 as right-circularly polarized light by the right-circular polarizing plate, it is sufficiently bright, especially when observed near the front, and has a higher contrast. A high image was obtained.

  On the other hand, when the image light emitted from the projector was projected onto the projection screen 2, the viewing angle did not change regardless of the polarization state of the image light. Also, the contrast of the image was low due to the influence of ambient light such as illumination light.

1 is a schematic cross-sectional view showing a projection system including a projection screen according to an embodiment of the present invention. In the projection system shown in FIG. 1, the schematic cross-sectional view for demonstrating an effect | action at the time of switching the polarization state of the image light projected on a projection screen. FIG. 3 is a schematic longitudinal sectional view showing a modification of the projection system shown in FIGS. 1 and 2. FIG. 4 is a schematic sectional view showing a modification of the projection screen used in the projection system shown in FIGS. 1 to 3. FIG. 4 is a schematic diagram for explaining an optical function of each polarization selective reflection layer used in the projection screen shown in FIGS. 1 to 3. FIG. 4 is a schematic diagram for explaining an alignment state of each polarization selective reflection layer used in the projection screen shown in FIGS. 1 to 3.

Explanation of symbols

10 Projection Screen 11-1 First Polarization Selective Reflection Layer 11-2 Second Polarization Selective Reflection Layer 11a-1, 11b-1, 11c-1 Partial Selective Reflection Layer 11a-2, 11b-2, 11c-2 Partial Selective Reflection Layer 12 Support base material 20 Projection system 21 Projector 22 Polarization control member 23 Illumination light source 24 Polarization film 25 Illumination light source installation unit 30 Helical structure region 31 Image light 31R Right circularly polarized light 31L in the selective reflection wavelength region Left circle in the selective reflection wavelength region Polarized light 32R Right circularly polarized light 32L outside the selective reflection wavelength region Left circularly polarized light 33, 36 outside the selective reflection wavelength region Reflected light 34 Illumination light 41 Reflected light with right circular polarization (reflected light with a narrow viewing angle)
42 Left circularly polarized reflected light (reflected light with a wide viewing angle)
43 Reflected light of illumination light (reflected light with a narrow viewing angle)
45 observer

Claims (13)

A first polarization selective reflection layer that selectively reflects the first polarized light having a specific polarization component;
A second polarization selective reflection layer that selectively reflects a second polarization having a polarization component different from the first polarization reflected by the first polarization selective reflection layer;
The first polarized light selective reflection layer and the second polarized light selective reflection layer diffuse the reflected light by their own structure, and diffuse the first polarized light reflected by the first polarized light selective reflection layer. A projection screen, wherein an angle and a diffusion angle of the second polarized light reflected by the second polarized light selective reflection layer are different from each other.   The projection screen according to claim 1, wherein one of the first polarized light and the second polarized light is right circularly polarized light, and the other is left circularly polarized light. Wherein the first polarized-light selective reflection layer and the second polarized-light selective reflection layer is characterized by have a cholesteric liquid crystal structure, the projection screen according to claim 1 or 2.   4. The projection screen according to claim 3, wherein the cholesteric liquid crystal structures of the first polarization selective reflection layer and the second polarization selective reflection layer include a plurality of spiral structure regions having different spiral axis directions. 5.   The first polarization selective reflection layer and the second polarization selective reflection layer selectively reflect light in a specific wavelength range that covers only a part of the visible light range. The projection screen according to any one of the above.   The selective reflection center wavelength of the first polarized light selective reflection layer and the second polarized light selective reflection layer is based on the case where light is perpendicularly incident on the first polarized light selective reflection layer and the second polarized light selective reflection layer. The projection screen according to claim 5, wherein the projection screen is in a range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm. The projection screen according to claim 1, wherein the first polarization selective reflection layer and the second polarization selective reflection layer are made of a polymerizable liquid crystal material after solidification .   The projection screen according to any one of claims 1 to 7, further comprising a support base material that supports the first polarization selective reflection layer and the second polarization selective reflection layer.   The projection screen according to claim 8, wherein the support substrate includes a light absorption layer that absorbs light in a visible light range.   The projection screen according to claim 8, wherein the supporting base material is a transparent base material that transmits at least part of light in a visible light region. A projection screen according to any one of claims 1 to 10,
A projector that projects image light on the projection screen;
A projection system configured to switch a polarization state so that image light projected from the projector has a polarization component of either the first polarization or the second polarization. An illumination light source that emits illumination light toward the projection screen;
The illumination light emitted from the illumination light source is substantially the same as the wavelength dispersion of the first polarization and the second polarization reflected by the first polarization selective reflection layer and the second polarization selective reflection layer. 12. Projection system according to claim 11, characterized in that it has chromatic dispersion.   The illumination light emitted from the illumination light source is polarized light having a smaller diffusion angle among the first polarized light and the second polarized light reflected by the first polarized light selective reflection layer and the second polarized light selective reflection layer. The projection system according to claim 11, wherein the projection system has the same polarization component as the polarization component.

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