JP2005115363A - Projection screen and projection system with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection screen that can sharply display an image even under bright environmental light and has improved brightness distribution and an improved angle of view, and a projection system with the same. <P>SOLUTION: A projection screen 10-1 includes: a polarized-light selective reflection layer 11 having a cholesteric liquid crystalline structure, capable of selectively diffuse-reflecting a specific polarized-light component; a substrate 12 for supporting the polarized-light selective reflection layer 11; and an optical member 40 provided on the observation side of the polarized-light selective reflection layer 11. The optical member 40 diffuses imaging light which the polarized-light selective reflection layer diffuse-reflects, while maintaining the state of polarization of the imaging light. The optical member 40 diffuses right-handed circularly polarized light 31R that is projected on the projection screen 10-1 into diffused light 31a. Right-handed circularly polarized light incident on the polarized-light selective reflection layer 11 is diffuse-reflected owing to the scattering property of the polarized-light selective reflection layer 11 to become diffused light 31a2. The diffused light 31a2 when traveling from the side of the polarized-light selective reflection layer 11 to an observation side is further diffused by the optical member 40 to becomes diffused light 31a3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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, the visibility that can clearly display the image and improve the luminance distribution and the viewing angle. The present invention relates to an excellent projection screen and a projection system including the same.

  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 etc. are proposed (refer patent documents 1 and 2).

  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 a wavelength selectivity, but does not have a polarization selectivity, and there is a problem that an image can be clearly displayed only within a certain limit. 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.

  Specifically, in the above-mentioned Patent Document 1, a cholesteric liquid crystal that reflects light of each color of red, green, and blue (right circularly polarized light or left circularly polarized light) included in video light is used, and the circularly polarized light separation function of the cholesteric liquid crystal is used. Describes a projection screen that does not reflect approximately half of the ambient light.

  However, in the projection screen described in Patent Document 1, since the cholesteric liquid crystal is in the planar alignment state, when light is reflected by such a cholesteric liquid crystal, the reflection of light becomes specular reflection, and the light is reflected. It is difficult to visually recognize as an image. That is, in order to visually recognize light as an image, the reflected light needs to have a scattering effect. However, the projection screen described in Patent Document 1 does not consider this point at all.

  On the other hand, the above-mentioned Patent Document 2 is a projection screen that uses a diffusive multilayer reflective polarizer as a reflective polarization element, and reflects a part of ambient light by a polarization separation function such as a multilayer reflective polarizer. It is described that the scattering effect is given to the reflected light by the interface reflection of the materials having different refractive indexes constituting the multilayer reflective polarizing material or the diffusion element provided separately from the multilayer reflective polarizing material. Has been. Further, Patent Document 2 discloses a projection screen using a cholesteric reflective polarizing material or the like as a reflective polarizing element, and using the reflective polarizing element and a diffusing element in combination, polarization of a cholesteric reflective polarizing material or the like. There is a description that a part of the ambient light is not reflected by the separation function and a scattering effect is given to the reflected light by a diffusion element provided separately from the cholesteric reflective polarizing material.

  However, the former one described in Patent Document 2 is based on a linearly polarizing element such as a multilayer reflective polarizing material (such as DBEF manufactured by 3M), and is therefore incorporated in a projection system or the like. When used in a projector, it is necessary to match the plane of polarization with a projector such as a liquid crystal projector that emits linearly polarized light. If the planes of polarization do not match, a good image display cannot be realized. There is a problem.

  Moreover, in the latter one described in Patent Document 2, although a circularly polarizing element such as a cholesteric reflective polarizing material is used as the reflective polarizing element, it is provided on the observation side of the reflective polarizing element. Since the diffusing element imparts a scattering effect to the reflected light, the polarization separation function provided by the reflective polarizing element is impaired, and there is a problem that the visibility of the image cannot be sufficiently improved.

  That is, since the diffusing element is provided on the observation side of the reflective polarizing element, the light is transmitted through the diffusing element before entering the reflective polarizing element, and the polarization state is disturbed (this is referred to as “depolarization”). "). Here, there are two types of light that pass through the diffusing element: ambient light (external light, etc.) and image light. When the polarization state of the ambient light is disturbed by the diffusing element, The light to be transmitted is converted into a component reflected by the reflective polarizing element by depolarization, and is reflected by the reflective polarizing element 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 reflective polarizing element is converted to a component that is not reflected by the reflective polarizing element due to the depolarization. The element is transparent. Due to these two phenomena, the original polarization separation function is impaired, and there is a problem that the visibility of the image cannot be sufficiently improved.

As described above, in the conventional projection screen described above, both the one using a hologram and the one using a polarization separation layer as described in Patent Documents 1 and 2 are constant under bright ambient light. Therefore, the video can be displayed clearly only at the limit, and the visibility of the video cannot be sufficiently improved.
JP-A-5-107660 JP 2002-540445 A

  The present invention has been made in consideration of such points, and is a projection screen with excellent visibility capable of clearly displaying an image even under bright ambient light and improving the luminance distribution and the viewing angle. An object is to provide a projection system including the same.

  The projection screen according to the present invention includes a polarization selective reflection layer that selectively diffuses and reflects light of a specific polarization component in the projection screen that reflects the image light projected from the observation side and displays the image, and the polarization selection A polarization maintaining diffusion layer is provided on the observation side of the reflection layer and diffuses the image light diffusely reflected by the polarization selective reflection layer while maintaining its polarization state. In this specification, “maintaining the polarization state of the image light” means maintaining the polarization state of the image light substantially constant. Specifically, the polarization state of the image light is 80%. As mentioned above, it means holding preferably 90% or more.

  In the above-described projection screen according to the present invention, the polarization-maintaining diffusion layer has an uneven portion on one or both of the observation-side surface and the polarization-selective reflection layer-side surface of the polarization-maintaining diffusion layer. It is preferable that is formed.

  In the above-described projection screen according to the present invention, it is preferable that the polarization maintaining diffusion layer is at least one optical member selected from the group consisting of frosted glass and holographic optical elements.

  Furthermore, in the above-described projection screen according to the present invention, it is preferable that the light of the specific polarization component is right circularly polarized light or left circularly polarized light. The light of the specific polarization component may be one linearly polarized light.

  Furthermore, in the above-described projection screen according to the present invention, the polarization selective reflection layer diffuses the light reflected by the polarization selective reflection layer main body that reflects the light of the specific polarization component and the polarization selective reflection layer main body. And a diffusing element. Further, the polarization selective reflection layer itself may have diffusibility. In the latter case, it is preferable that the polarization selective reflection layer has a cholesteric liquid crystal structure and diffuses the light of the specific polarization component due to structural nonuniformity of the cholesteric liquid crystal structure. Here, the cholesteric liquid crystal structure preferably includes a plurality of spiral structure regions having different spiral axis directions.

  Furthermore, it is preferable that the projection screen according to the present invention further includes a support base material that supports the polarization selective reflection layer. Here, the support base material may be an absorption base material including a light absorption layer that absorbs light in the visible light range, or a transparent base material that transmits at least part of light in the visible light range. May be.

  Furthermore, in the above-described projection screen according to the present invention, it is preferable that the polarization selective reflection layer has at least two partial selective reflection layers laminated on each other. Here, it is preferable that an intermediate layer having a barrier property or an easy adhesion property is provided between adjacent partial selective reflection layers of the polarization selective reflection layer.

  Furthermore, the projection screen according to the present invention described above further includes a functional holding layer including at least one layer selected from the group consisting of a hard coat layer, an antireflection layer, an ultraviolet absorption layer, and an antistatic layer. preferable.

  A projection system according to the present invention includes the above-described projection screen according to the present invention, and a projector that projects image light on the projection screen.

  According to the present invention, (1) the image light diffused and reflected by the polarization selective reflection layer is maintained in the polarization state on the observation side of the polarization selective reflection layer that selectively diffuses and reflects light of a specific polarization component. Since the polarization maintaining diffusion layer is provided to diffuse, the polarization maintaining diffusion layer diffuses the image light incident from the observation side toward the polarization selective reflection layer while maintaining the polarization state. Video light emitted toward the observation side after being diffusely reflected by the selective reflection layer can be diffused while maintaining its polarization state. That is, the projected image light is diffused by the polarization-maintaining diffusion layer without disturbing its polarization state, and then incident on the polarization selective reflection layer, and then selectively diffusely reflected by the polarization selective reflection layer. Specifically, the light is again diffused by the polarization maintaining diffusion layer and then emitted to the observation side. For this reason, the image can be clearly displayed without impairing the original polarization separation function of the polarization selective reflection layer, and even if the scattering effect (diffusion effect) by the polarization selective reflection layer is insufficient The luminance distribution and viewing angle of the screen can be improved.

  (2) Here, as the polarization maintaining diffusion layer, one having an uneven portion formed on one or both of the observation side surface and the polarization selective reflection layer side surface of the polarization maintaining diffusion layer is used. By doing so, the light passing through the polarization maintaining diffusion layer is not multiple-reflected within the polarization maintaining diffusion layer, and the polarization state of the light can be more reliably maintained. In addition, when the uneven | corrugated | grooved part is provided in the surface by the side of observation among polarization maintaining diffusion layers, an uneven | corrugated | grooved part becomes a glare-proof layer and it can also anticipate preventing the glare of a projection screen. In addition, when the unevenness portion is provided on the surface of the polarization maintaining diffusion layer of the polarization maintaining diffusion layer and the surface on the observation side is kept flat (smooth), a functional retaining layer such as an antireflection layer is provided. It can be easily provided on the surface on the observation side.

  (3) Moreover, if frosted glass, a holographic optical element, or the like is used as the polarization maintaining diffusion layer, the light passing through the polarization maintaining diffusion layer can be diffused in a more appropriate manner. In particular, in frosted glass, high diffusibility can be obtained depending on the accuracy when one side is ground by sandblasting or the like (for example, matte processing in one direction or both vertical and horizontal directions). In addition, in the holographic optical element, for example, the light diffusion angle can be set to an arbitrary angle by a special hologram pattern (collection of fine concave and convex groove surfaces) provided on the back surface of the substrate, and high diffusibility is achieved. Can be obtained.

  (4) Here, the polarization selective reflection layer is only light of a specific polarization component (for example, right circular polarization when the light of the specific polarization component is right circular polarization or left circular polarization) due to its polarization separation characteristic. Therefore, ambient light having no polarization characteristics, such as ambient light and illumination light, can be reflected by only about 50% by the polarization selective reflection layer. For this reason, even when the brightness of the bright display portion such as white display is the same, the brightness of the dark display portion such as black display can be substantially halved and the contrast of the image can be approximately doubled. At this time, if the projected image light mainly includes light having the same polarization component as that of the light selectively reflected by the polarization selective reflection layer (for example, right circularly polarized light), the projected image light is projected. The image light can be reflected almost 100% by the polarization selective reflection layer, and the image light can be reflected efficiently. Note that even if a projector such as a liquid crystal projector that projects image light onto a projection screen emits linearly polarized light, a linearly polarized light can be obtained by using a retardation plate for converting the linearly polarized light into circularly polarized light. Regardless of the direction, it can be used as a projector for such a projection screen.

  (5) The light of a specific polarization component that is selectively reflected by the polarization selective reflection layer may be one of linearly polarized light (P-polarized light or S-polarized light). Also in this case, since the polarization selective reflection layer selectively reflects only light of a specific polarization component (for example, P-polarized light) due to its polarization separation characteristic, ambient light such as outside light or illumination light having no polarization characteristic is used. Can be made to reflect only about 50% by the polarization selective reflection layer. For this reason, even when the brightness of the bright display portion such as white display is the same, the brightness of the dark display portion such as black display can be substantially halved and the contrast of the image can be approximately doubled. At this time, if the projected image light mainly includes light having the same polarization component as that of the light selectively reflected by the polarization selective reflection layer (for example, P-polarized light), the projected image is displayed. Light can be reflected almost 100% by the polarization selective reflection layer, and image light can be efficiently reflected. In addition, when the light of the specific polarization component selectively reflected by the polarization selective reflection layer is one linearly polarized light, by aligning the projection screen in the direction of the linearly polarized light of the projector that emits the linearly polarized light, The image can be displayed brightly.

  (6) The polarization selective reflection layer may include a polarization selective reflection layer main body that reflects light of a specific polarization component and a diffusion element that diffuses light reflected by the polarization selective reflection layer main body. Good. In this case, since the polarization separation characteristic and the diffusion characteristic can be made independent, the respective characteristics can be easily controlled.

  (7) Moreover, the polarization selective reflection layer itself may have diffusibility. In this case, since the polarization state of incident light is not disturbed, a strong reflection intensity can be obtained. Specifically, when a diffusing element that does not maintain the polarization state of incident light is provided on the observation side of the reflective polarizing element, the light passes through the diffusing element before entering the reflective polarizing element. , The polarization state is disturbed (this is called “depolarization”). Here, there are two types of light that pass through the diffusing element: ambient light (external light, etc.) and image light. When the polarization state of the ambient light is disturbed by the diffusing element, The light to be transmitted is converted into a component reflected by the reflective polarizing element by depolarization, and is reflected by the reflective polarizing element 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 reflective polarizing element is converted to a component that is not reflected by the reflective polarizing element due to the depolarization. The element is transparent. Due to these two phenomena, the original polarization separation function is impaired, and the visibility of the image cannot be sufficiently improved. However, when the polarization selective reflection layer itself has diffusibility, the above-mentioned problem of “depolarization” does not occur, while maintaining the original polarization separation function of the polarization selective reflection layer, The visibility of the image can be improved.

  (8) The polarization selective reflection layer preferably has a cholesteric liquid crystal structure, and diffuses light of a specific polarization component due to the structural nonuniformity of the cholesteric liquid crystal structure. In this case, the above-mentioned “depolarization” problem does not occur with respect to ambient light and image light transmitted through the polarization selective reflection layer, while maintaining the original polarization separation function of the polarization selective reflection layer. Visibility can be improved. Specifically, in the polarization selective reflection layer, the cholesteric liquid crystal structure has structural non-uniformity. For example, the direction of the helical axis of the helical structure region included in the cholesteric liquid crystal structure varies, thereby Light is diffusely reflected, not specularly reflected, making it easier to view the image. At this time, the polarization selective reflection layer diffuses the selectively reflected light due to the structural non-uniformity of the cholesteric liquid crystal structure. This light can be transmitted without being diffused.

  (9) Further, a functional holding layer including at least one layer selected from the group consisting of a hard coat layer, an antireflection layer, an ultraviolet absorption layer, and an antistatic layer is provided on the observation side surface of the polarization selective reflection layer, for example. If provided, scratches, dirt, glare, excessive reflection of light, and discoloration due to ultraviolet components can be prevented, and static electricity can be removed.

  (10) Further, as the projection system, a projection system including the above-described projection screen and a projector that projects image light on the projection screen can be used. In this case, for example, the structure of the cholesteric liquid crystal structure of the polarization selective reflection layer is improved while suppressing the influence of ambient light such as external light and illumination light by the polarization separation characteristic of the polarization selective reflection layer of the projection screen and increasing the contrast of the image. Due to general non-uniformity and the like, it is possible to give a scattering effect to the reflected light of the image light without reducing the visibility of the image. In addition, the polarization maintaining diffusion layer provided on the observation side of the polarization selective reflection layer allows the image light projected from the observation side to be selectively reflected without being disturbed even when passing through the polarization maintaining diffusion layer. After being incident on the layer, it is selectively diffused and reflected by the polarization selective reflection layer, and further diffused by the polarization maintaining diffusion layer, so that the image is clearly displayed without impairing the original polarization separation function of the polarization selective reflection layer. In addition, the luminance distribution and viewing angle of the projection screen can be improved even when the scattering effect (diffusion effect) by the polarization selective reflection layer is insufficient.

BEST MODE FOR CARRYING OUT THE INVENTION

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

Projection Screen First, a projection screen according to an embodiment of the present invention will be described with reference to FIG. 1A.

  As shown in FIG. 1A, a projection screen 10-1 according to the present embodiment reflects an image light projected from the observation side (upper side in the drawing) and displays an image, and has a specific polarization component. The polarization selective reflection layer 11 having a cholesteric liquid crystal structure that selectively diffuses and reflects the light of the light, the support base 12 that supports the polarization selective reflection layer 11, and the observation side of the polarization selective reflection layer 11 are provided. An optical member (polarization maintaining diffusion layer) 40 that diffuses the image light diffusely reflected by the layer 11 while maintaining its polarization state is provided. The projection screen main body 10 is constituted by the polarization selective reflection layer 11 and the support base 12.

[Projection screen body]
Next, the projection screen body 10 will be described with reference to FIG. 1B.

  As shown in FIG. 1B, the polarization selective reflection layer 11 constituting the projection screen body 10 is made of a liquid crystalline composition exhibiting cholesteric regularity, and a director of liquid crystal molecules is a layer as a physical molecular arrangement of liquid crystal molecules. It has a spiral structure that is continuously rotated in the thickness direction.

  The polarization selective reflection layer 11 has a polarization separation characteristic for separating a circularly polarized light component in one direction and a circularly polarized light component in the opposite direction based on the physical molecular arrangement of the liquid crystal molecules. ing. That is, in the polarization selective reflection layer 11, non-polarized light incident along the spiral axis is separated into two polarized light (right circularly polarized light and left circularly polarized light), one of which is transmitted and the remaining is reflected. Is done. 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 perpendicular 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. 1B, unpolarized light (right circularly polarized light 31R and left circularly polarized light 31L within the selective reflection wavelength region, right circularly polarized light 32R and left circularly polarized light outside the selective reflection wavelength region, incident from the observation side of the projection screen body 10 in FIG. 32L) is one circularly polarized light component (for example, within the selective reflection wavelength region) belonging to the range (selective reflection wavelength region) of the wavelength bandwidth Δλ centered on the selective reflection center wavelength λ ₀ according to the polarization separation characteristic as described above. Right circularly polarized light 31R) is reflected as reflected light 33, and other light (for example, left circularly polarized light 31L within the selective reflection wavelength region, right circularly polarized light 32R and left circularly polarized light 32L outside the selective reflection wavelength region) is transmitted.

  Note that such a cholesteric liquid crystal structure of the polarization selective reflection layer 11 includes a plurality of spiral structure regions 30 having different directions of the spiral 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 state in which at least a part of the surface of the same XY direction in the XY direction is not parallel to the surface of the polarization selective reflection layer 11 (when a cross-sectional TEM photograph of the dyed cholesteric liquid crystal structure film is taken, a gray pattern A state in which a continuous curve of the appearing layers is not parallel to the substrate surface), or a state in which fine particles of cholesteric liquid crystal are dispersed as a pigment. Further, “diffusion” that causes such structural nonuniformity of the cholesteric liquid crystal structure is such that the observer can recognize the reflected light (image light) reflected by the projection screen body 10 as an image. It means spreading or scattering.

  On the other hand, a general cholesteric liquid crystal structure is in a planar alignment state, and as shown in FIG. 2B, the direction of the helical 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 helical structure region 30 included in the cholesteric liquid crystal structure of the polarization selective reflection layer 11 selectively selects light in a specific wavelength range that covers only a part of the visible light range (for example, a wavelength range of 400 to 700 nm). It is preferable to have a specific helical pitch length to reflect. More specifically, the cholesteric liquid crystal structure of the polarization selective reflection layer 11 has a wavelength range of image light projected by a projector such as a liquid crystal projector (for example, light in a specific wavelength range that covers only a part of the visible light range). It is preferable to have at least two types of helical pitch lengths that are discontinuously different so as to selectively reflect only light in a wavelength region corresponding to). In general, the projector 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 spiral pitch of the cholesteric liquid crystal structure so as to selectively reflect light having a selective reflection center wavelength in the range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm on the basis of the case where light is incident vertically. The length should 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 ranges of red (R), green (G), and blue (B) are expressed as selective reflection wavelength ranges that are independent from each other, the cholesteric liquid crystal structure of the polarization selective reflection layer 11 is discontinuous. It is preferable to have three different helical pitch lengths. 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 structure of the polarization selective reflection layer 11 has two or more types of helical pitch lengths that are discontinuously different, the polarization selective reflection layer 11 is a partial selection of at least two or more layers having different helical pitch lengths. It can be configured by stacking reflective layers on each other. Specifically, as shown in FIG. 3, a partial selective reflection layer 11a that selectively reflects light in the blue (B) wavelength region and a portion that selectively reflects light in the green (G) wavelength region. The selective reflection layer 11b and the partial selective reflection layer 11c that selectively reflects light in the red (R) wavelength region may be stacked in order from the support base 12 side. In addition, the order of stacking the partial selective reflection layers 11a, 11b, and 11c is not necessarily limited to this, and an arbitrary order can be appropriately taken. In FIG. 3, each of the partial selective reflection layers 11a, 11b, and 11c emits light of a specific polarization component (for example, right circularly polarized light) in the same manner as the polarization selective reflection layer 11 shown in FIGS. 1B and 2A. It has a cholesteric liquid crystal structure that selectively reflects and has a cholesteric liquid crystal structure that diffuses selectively reflected light due to its structural non-uniformity.

  The thickness of the polarization selective reflection layer 11 (or each of the partial selective reflection layers 11a, 11b, and 11c constituting the polarization selective reflection layer 11) reflects substantially 100% of light in a specific polarization state that is selectively reflected. It is preferable to set the size to such a degree that the reflectance is saturated. 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). Note that the reflectance of the polarization selective reflection layer 11 (or the partial selective reflection layers 11a, 11b, and 11c constituting the polarization selective reflection layer 11) directly depends on the number of helical pitches, but the helical pitch length is If it is fixed, it indirectly depends on the thickness of the polarization selective reflection layer 11 (or each partial selective reflection layer 11a, 11b, 11c constituting the polarization selective reflection layer 11). 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 ), Partially selective reflecting layers 11a, 11b, and 11c for reflecting light in one of the wavelength ranges of green (G) and blue (B), a thickness of about 1 to 10 μm is required. On the other hand, the thickness of the polarization selective reflection layer 11 (or the partial selective reflection layers 11a, 11b, and 11c constituting the polarization selective reflection layer 11) is not as good as it is thick. The above-mentioned range is appropriate because it becomes difficult, unevenness occurs, and the degree of light absorption by the material itself increases.

  Next, the support base 12 will be described.

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

  Here, the support substrate 12 preferably includes a light absorption layer that absorbs light in the visible light range.

  Specifically, for example, as shown in FIG. 4, the support base 12 (12 </ b> A) may be formed using a plastic film (for example, a black PET film containing carbon) kneaded with a black pigment. . In this case, the entire support substrate 12 (12A) becomes a light absorption layer (light absorption substrate). As a result, light that should not be reflected as reflected light 33 among unpolarized light incident from the observation side of the projection screen body 10 (left circularly polarized light 31L within the selective reflection wavelength region, right circularly polarized light outside the selective reflection wavelength region). 32R and left circularly polarized light 32L) and light incident from the back side of the projection screen main body 10 are absorbed to generate reflected light caused by ambient light such as external light and illumination light, and stray light caused by image light. Can be effectively prevented.

  In addition to the embodiment of the support substrate 12 (12A) shown in FIG. 4, as shown in FIGS. 5 and 6, on the surface on either side of the transparent support film 14 such as a plastic film, The support substrate 12 (12B, 12C) may be formed by forming the light absorption layer 15 made of a black pigment or the like.

  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 and the support film 14 includes polycarbonate polymers, polyester polymers such as polyethylene terephthalate, polyimide polymers, polysulfone polymers, and polyethersulfone polymers. Molecule, polystyrene polymer, polyolefin polymer such as polyethylene and polypropylene, polyvinyl alcohol polymer, cellulose acetate polymer, polyvinyl chloride polymer, polyacrylate polymer, polymethyl methacrylate polymer, etc. A film made of a thermoplastic polymer or the like can be used. In addition, the material of the support base material 12 and the support film 14 is not limited to this, Materials, such as a metal, a paper material, a cloth material, glass, can also be used.

  In addition, when laminating the polarization selective reflection layer 11 on the support substrate 12, as described later, it is common to apply an alignment treatment and a curing treatment after applying a liquid crystalline composition exhibiting cholesteric regularity. It is.

  In this case, since it is necessary to control the cholesteric liquid crystal structure of the polarization selective reflection layer 11 so as not to be in the planar alignment state, the support substrate 12 has an alignment ability on the surface on which the liquid crystalline composition is applied. It is preferable to use those not used.

  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, or controlling the material of the liquid crystalline composition and the process conditions for aligning the liquid crystalline composition, the cholesteric liquid crystal structure of the polarization selective reflection layer 11 is planar aligned. It is possible to control so as not to be in a state.

  Further, when the surface of the support substrate 12 on which the liquid crystalline composition is applied has orientation ability, as shown in FIG. 7, the polarization selective reflection layer 11 and the support substrate 12 (12A ) Between the cholesteric liquid crystal structure of the polarization selective reflection layer 11 and the intermediate layer 13 in the cholesteric liquid crystal structure of the polarization selective reflection layer 11. It is also possible for the director of the liquid crystal molecules in the vicinity of the interface to face in a plurality of directions. In addition, when providing intermediate | middle layers 13, such as an easily bonding layer, the adhesiveness between the polarization selective reflection layer 11 and the support base material 12 can also be improved. In addition, as such an intermediate | middle layer 13, 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 the thing marketed generally is used. be able to. 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 13 can also be used as a light absorbing layer that kneads a black pigment or the like and absorbs light in the visible light region, like the support base 12 (12A) shown in FIG.

  Here, when the surface of the support substrate 12 does not have the alignment ability and the adhesion between the polarization selective reflection layer 11 and the support substrate 12 is sufficiently high, the intermediate layer 13 is necessarily provided. There is no. Moreover, as a method for improving the adhesiveness between the polarization selective reflection layer 11 and the support substrate 12, process methods such as corona treatment and UV cleaning can be used.

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

  First, the support base material 12 on which the polarization selective reflection layer 11 is laminated is prepared. If necessary, an intermediate layer 13 such as an easy adhesion layer is laminated on the surface of the support base 12 on the side where the polarization selective reflection layer 11 is provided. At this time, the surface of the support substrate 12 on which the liquid crystalline composition is applied (or the surface when the intermediate layer 13 is present) is made to have no orientation ability.

  Next, after applying a liquid crystalline composition exhibiting cholesteric regularity on the support substrate 12 thus prepared, the polarization selective reflection layer 11 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 layer 11 will be described.

(Coating process)
In the coating step, a cholesteric liquid crystal layer is formed by coating a liquid crystalline composition exhibiting cholesteric regularity on the support substrate 12. 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 support base material 12, the chiral nematic liquid crystal and cholesteric liquid crystal which show cholesteric regularity can be used. 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 layer 11 which is 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. Moreover, a polymerization initiator and a suitable additive 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 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, easily subjected to hydrolysis, and the compound itself 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 has 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 layer 11 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, the cholesteric liquid crystal structure of the polarization selective reflection layer 11 finally obtained, and the like. 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%.

(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.

  Here, the cholesteric liquid crystal structure of the polarization selective reflection layer 11 to be finally obtained is not a planar alignment state as shown in FIG. 2B, but a plurality of helical structures as shown in FIG. Although the orientation of the spiral axis L of the region 30 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, and (3) radiation. 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 crystal composition which 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 in which liquid crystal molecules in the liquid crystalline composition are thermally polymerized by heating to cure the cholesteric liquid crystal layer. 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. 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, methyl benzoyl 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, the addition amount of the photopolymerization initiator added to the liquid crystalline composition is 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. Preferably there is.

  The projection screen 10 including the polarization selective reflection layer 11 made of a single cholesteric liquid crystal layer can be manufactured by performing the above-described series of steps (coating step, alignment step and curing step). By repeating the above-described series of steps, it is possible to manufacture the projection screen 10 including the polarization selective reflection layer 11 composed of a plurality of cholesteric liquid crystal layers. Thus, for example, as shown in FIG. 3, as the polarization selective reflection layer 11, a partial selective reflection layer 11a that selectively reflects light in the blue (B) wavelength region, and light in the green (G) wavelength region. The projection screen main body 10 in which a partial selective reflection layer 11b that selectively reflects light and a partial selective reflection layer 11c that selectively reflects light in the red (R) wavelength region are sequentially laminated from the support base 12 side. Can be manufactured.

  In this case, if the lower cholesteric liquid crystal layer is formed and fixed, the same method can be used when applying the liquid crystalline composition of the second and subsequent cholesteric liquid crystal layers. 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 (see reference numeral 13 in FIG. 8) 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.

  Thus, the projection screen body 10 includes the polarization selective reflection layer 11 having a cholesteric liquid crystal structure that selectively reflects light of a specific polarization component, and the helical axis L of the helical structure region 30 included in the cholesteric liquid crystal structure. Due to the structural non-uniformity of the cholesteric liquid crystal structure due to variations in the direction of the light, the selectively reflected light is diffused.

  At this time, the polarization selective reflection layer 11 selectively reflects only light of a specific polarization component (for example, right circularly polarized light) due to the polarization separation characteristic of the cholesteric liquid crystal structure. Thus, it is possible to reflect only about 50% of the ambient light such as by the polarization selective reflection layer 11. For this reason, even when the brightness of the bright display portion such as white display is the same, the brightness of the dark display portion such as black display can be substantially halved and the contrast of the image can be approximately doubled. At this time, if the projected image light mainly includes light having the same polarization component as that of the light selectively reflected by the polarization selective reflection layer 11 (for example, right circularly polarized light), the projected image light is projected. The image light can be reflected almost 100% by the polarization selective reflection layer 11, and the image light can be reflected efficiently.

  Further, in the polarization selective reflection layer 11, the cholesteric liquid crystal structure has structural non-uniformity, and the direction of the helical axis L of the helical structure region 30 included in the cholesteric liquid crystal structure varies. Is diffusely reflected rather than specularly reflected, making it easier to visually recognize the image. At this time, the polarization selective reflection layer 11 diffuses the selectively reflected light due to the structural nonuniformity of the cholesteric liquid crystal structure, so that light of a specific polarization component (for example, a right circle in the selective reflection wavelength region). While diffusing the polarized light 31R), other light (for example, the left circularly polarized light 31L within the selective reflection wavelength region, the right circularly polarized light 32R and the left circularly polarized light 32L outside the selective reflection wavelength region) is transmitted without being diffused. be able to. For this reason, the above-described “depolarization” problem does not occur with respect to ambient light and image light transmitted through the polarization selective reflection layer 11, while maintaining the original polarization separation function of the polarization selective reflection layer 11. Visibility can be improved.

  As described above, according to the projection screen main body 10 described above, the influence of ambient light such as external light and illumination light is suppressed by the polarization separation characteristic of the cholesteric liquid crystal structure, and the contrast of the image is increased. The scattering effect can be given to the reflected light of the image light without reducing the visibility of the image due to the structural non-uniformity, and the image can be clearly displayed even under bright ambient light.

  Further, according to the projection screen main body 10 described above, the polarized light selective reflection layer 11 selectively reflects light in a specific wavelength range that covers only a part of the visible light range. The contrast of the image can be increased by further suppressing the influence of ambient light such as illumination light, and the visibility of the image can be further improved.

  In the projection screen main body 10 described above, as shown in FIG. 9, the projection screen main body 10 is incident on the support substrate 12 on the side of the support substrate 12 opposite to the surface on which the polarization selective reflection layer 11 is provided. A light reflecting layer 16 that reflects the light to be emitted may be provided. Thereby, in the case where the support base 12 includes the light absorption layer in the manner shown in FIGS. 4 to 6, external light or illumination light incident from the back side of the projection screen 10-1 having the projection screen body 10. Environmental light such as can be effectively reflected before it reaches the support substrate 12 (especially the light absorption layer contained therein), and heat generation of the support substrate 12 can be effectively suppressed. it can. As the light reflection layer 16, it is preferable to use a white scattering layer (paper material, white film, paint film, etc.), a metal plate, an aluminum powder film, or the like.

  Further, as shown in FIG. 9, the polarization selective reflection is performed on the surface of the support base 12 opposite to the surface on which the polarization selective reflection layer 11 is provided (the back side of the light reflection layer 16 in FIG. 9). You may make it provide the adhesion layer 17 for affixing the support base material 12 in which the layer 11 was provided to an external member. Thereby, the projection screen 10-1 provided with the projection screen main body 10 can be attached to an external member such as a white board or a wall as necessary when in use. In addition, as the adhesive layer 17, it is preferable that the support base material 12 provided with the polarization selective reflection layer 11 can be detachably attached to an external member, and a re-peeling adhesive film (manufactured by Panac Corporation). It is preferable to use a weak adhesive film such as Moreover, it is preferable to affix the peeling film 18 on the surface of the adhesion layer 17 for the purpose of protecting the adhesion layer 17 when not in use.

  Further, as shown in FIG. 9, on the observation side surface of the projection screen 10-1 having the projection screen body 10 (here, the observation side surface of the optical member 40 provided on the observation side of the projection screen body 10). The functional holding layer 19 may be provided. As the functional retention layer 19, various types can be used. For example, a hard coat layer (HC layer), an antireflection layer (AR layer), an ultraviolet absorption layer (UV absorption layer), and an antistatic layer (AS) Layer).

  Here, the hard coat layer (HC layer) is a layer for protecting the surface of the projection screen 10-1 to prevent scratches and dirt from being attached. The antireflection layer (AR layer) is a layer for suppressing reflection of light on the surface of the projection screen 10-1. The ultraviolet absorbing layer (UV absorbing layer) is a layer for absorbing an ultraviolet component that causes the liquid crystalline composition to change to yellow among the light incident on the projection screen 10-1. The antistatic layer (AS layer) is a layer for removing static electricity generated in the projection screen 10-1. When the functional holding layer 19 is used as an antistatic layer, the functional holding layer 19 is not necessarily the surface on the observation side of the projection screen 10-1 (the optical member 40 provided on the observation side of the projection screen body 10). It is not necessary to be provided on the surface on the observation side), and it may be provided on the surface on the back side of the support base material 12, or by kneading carbon particles or the like into the support base material 12 itself. A function of removing static electricity may be added to the.

[Optical member (polarization maintaining diffusion layer)]
Next, the optical member (polarized light diffusing layer) 40 provided on the observation side of the projection screen body 10 will be described.

  First, the configuration of the optical member 40 will be described with reference to FIG. 1A.

  As shown in FIG. 1A, the optical member 40 is provided on the observation side of the polarization selective reflection layer 11, and an uneven portion 40 a is formed on one surface (observation side surface), and the other surface (polarization light). A flat portion 40b is formed on the surface of the selective reflection layer 11 side.

  Here, as the optical member 40, for example, an optical member such as frosted glass or a holographic optical element is used. The polarization state of the light transmitted through the optical member 40 is assumed to be disturbed mainly by multiple reflection, but the members such as the frosted glass and the holographic optical element described above do not multiply reflect the light transmitted through the inside. It can be diffused while maintaining the polarization state of light. In addition, as an optical member which produces multiple reflection, an opal light diffusion glass etc. are mentioned, for example.

  Here, when frosted glass is used as the optical member 40, high diffusibility can be obtained depending on the accuracy when one side is ground by sandblasting or the like (for example, matte processing in one direction or both vertical and horizontal directions). In addition, when using a holographic optical element, for example, the light diffusion angle can be set to an arbitrary angle by a special hologram pattern (collection of fine concavo-convex groove surfaces) provided on the back surface of the substrate. Diffusivity can be obtained. In addition, a frosted glass, a holographic optical element, etc. normally have a concavo-convex portion only on one side, and do not cause multiple reflection.

  The optical member 40 is not limited to the above-described frosted glass or holographic optical element, and any optical member can be used as long as it can diffuse light while maintaining its polarization state. It is also possible to use a mat film having a concavo-convex shape on the surface thereof and having substantially no phase difference.

  1A and 10, the optical function of the projection screen 10-1 provided with the optical member 40 having the above-described configuration is imaged from the projector 21 arranged in the manner shown in FIG. 10. A case where light is projected will be described as an example. Here, it is assumed that the polarization selective reflection layer 11 included in the projection screen body 10 of the projection screen 10-1 reflects the right circularly polarized light 31R within the selective reflection wavelength region.

  As shown in FIG. 10, the projector 21 is disposed on the normal line passing through the substantially central portion of the projection screen 10-1 on the observation side (observer 50 side) of the projection screen 10-1. In this manner, image light (for example, right circularly polarized light 31R within the selective reflection wavelength region) is projected onto the entire projection screen 10-1. For this reason, the image light (for example, right circularly polarized light 31R within the selective reflection wavelength region) projected from the projector 21 onto the projection screen 10-1 has different incident positions and incident angles as shown in FIG. Incident on the projection screen 10-1. Specifically, the incident angle is substantially vertical at the center of the projection screen body 10-1, whereas the end of the projection screen body 10-1 is inclined toward the center. The incident angle at the end of the projection screen body 10-1 is defined by, for example, the size of the projection screen body 10-1, the distance between the projection screen body 10-1 and the projector 21, and the like.

  Here, in the projection screen 10-1, as shown in FIG. 1A, the image light projected onto the projection screen 10-1 (for example, the right circularly polarized light 31R within the selective reflection wavelength region) is incident on the optical member 40. Then, the light passes through the concavo-convex portion 40a formed on the surface on the observation side and is diffused while the polarization state is maintained. When the image light projected on the projection screen 10-1 is unpolarized light, the light reflected by the polarization selective reflection layer 11 included in the projection screen body 10 is shown in FIG. 1A. Light other than (right circularly polarized light 31R within the selective reflection wavelength range) (left circular polarized light 31L within the selective reflection wavelength range, right circular polarized light 32R and left circular polarized light 32L outside the selective reflection wavelength range) is also diffused by the optical member 40. However, the polarization state of these lights (the left circularly polarized light 31L within the selective reflection wavelength region, the right circularly polarized light 32R and the left circularly polarized light 32L outside the selective reflection wavelength region) is maintained even after passing through the optical member 40. Therefore, as a result, the polarized light selective reflection layer 11 is transmitted.

  Hereinafter, the behavior of light reflected by the polarization selective reflection layer 11 (right circularly polarized light 31R in the selective reflection wavelength region) among the image light projected on the projection screen 10-1 will be described.

  In the projection screen 10-1, the right circularly polarized light 31R projected onto the projection screen 10-1 is diffused while the polarization state is maintained by the concave and convex portion 40a of the optical member 40, and is selectively reflected as diffused light 31a1. Incident on the layer 11. Next, the diffused light 31a1 is selectively reflected by the scattering property of the polarization selective reflection layer 11 (the structural nonuniformity of the cholesteric liquid crystal structure including a plurality of helical structure regions 30 having different directions of the helical axis L). The light is diffused and reflected by the property of diffusing light, and enters the optical member 40 in a state of being diffused in a substantially constant diffusion range as diffused light 31a2. Thereafter, the diffused light 31a2 is diffused by the concavo-convex portion 40a of the optical member 40, and is emitted as a diffused light 31a3 (reflected light 33-1) to the observation side while being diffused in a wider diffusion range. Note that image light emitted from the projection screen 10-1 to the observation side is reflected with a wider diffusion range than reflected light (reference numerals 33 and 33A in FIG. 10) in the case of only the projection screen main body 10 described later. It becomes light (reference numeral 33-1 in FIG. 10).

  As described above, the image light projected on the projection screen 10-1 is diffused by the optical member 40 without disturbing the polarization state thereof and then incident on the polarization selective reflection layer 11, and then the polarization selective reflection layer 11. Is diffused and reflected selectively, and finally diffused again by the optical member 40 and then emitted to the observation side. That is, in the projection screen 10-1, since the optical member 40 maintains the polarization state of the light that passes through the optical member 40, the polarization selective reflection layer 11 does not impair the original polarization separation function of the polarization selective reflection layer 11. While reflecting the light to be reflected, the light to be transmitted is not transmitted and the reflection efficiency is not lowered, so that the image can be clearly displayed. Further, even when the scattering effect (diffusion effect) by the polarization selective reflection layer 11 is insufficient, the image light selectively diffused and reflected by the polarization selective reflection layer 11 is further diffused by the optical member 40, so that the projection is performed. Regardless of the incident position (center portion, end portion, etc.) of the image light on the screen 10-1, the observer 50 can easily observe and improve the luminance distribution and the viewing angle of the projection screen 10-1. be able to. Moreover, in the projection screen 10-1, since the uneven part 40a of the optical member 40 is formed on the surface on the observation side, the uneven part 40a also functions as an antiglare layer and prevents glare of the projection screen 10-1. You can also expect to.

  Here, for comparison, according to FIGS. 11 and 12, the optical function of the projection screen main body 10 in which the optical member 40 is removed from the projection screen 10-1, the projector arranged in the manner shown in FIG. The case where the image light is projected from 21 will be described as an example.

  As shown in FIG. 11, the projector 21 is arranged on the normal side passing through the substantially central portion of the projection screen main body 10 on the observation side (observer 50 side) of the projection screen main body 10, and FIG. The image light (for example, right circularly polarized light 31R within the selective reflection wavelength region) is projected on the entire projection screen body 10 in the manner as shown in FIG. Therefore, the image light projected from the projector 21 onto the projection screen body 10 (for example, the right circularly polarized light 31R in the selective reflection wavelength region) has different incident positions and incident positions as shown in FIGS. It enters the projection screen main body 10 at an angle. Specifically, the incident angle is substantially vertical at the center of the projection screen 10, whereas the end of the projection screen 10 is inclined toward the center as shown in the figure. The incident angle at the end of the projection screen 10 is defined by, for example, the size of the projection screen 10 and the distance between the projection screen 10 and the projector 21.

  Here, in the projection screen main body 10, the image light projected onto the projection screen main body 10 (for example, the right circularly polarized light 31 </ b> R within the selective reflection wavelength region) is incident on the polarization selective reflection layer 11, and Due to the scattering property, the reflected light 33, 33A is emitted to the observation side in a state of being diffused in a substantially constant diffusion range. At this time, the image light projected from the projector 21 onto the projection screen main body 10 (for example, the right circularly polarized light 31R within the selective reflection wavelength region) is sent to the projection screen main body 10 as shown in FIGS. Are reflected and reflected from the polarization selective reflection layer 11 as reflected light 33 and 33A having different diffusion directions. Therefore, in the projection screen main body 10 described above, the reflected light 33 diffused toward the observer 50 is easily observed by the observer 50, but is diffused outward from the end of the projection screen main body 10. It is difficult for the observer 50 to observe the reflected light 33A. For this reason, in the projection screen body 10, when the scattering effect (diffusion effect) by the polarization selective reflection layer 11 is insufficient, the end of the projection screen 10 looks dark, and the luminance distribution of the projection screen body 10 Variation occurs, and the viewing angle also decreases.

  In the above, as the optical member 40 included in the projection screen 10-1, as shown in FIG. 1A and FIG. 13 (a), an uneven portion 40a is formed on one surface (observation surface), The case where the flat surface 40b formed on the other surface (the surface on the side of the polarization selective reflection layer 11) is used has been described as an example. However, as shown in FIG. In this case, a flat portion 40b may be formed on the surface (observation side surface), and an uneven portion 40a may be formed on the other surface (polarization selective reflection layer 11 side surface). In this case, the light incident on the optical member 40 from the observation side passes through the uneven portion 40a after passing through the flat portion 40b. Rather, it is diffused while maintaining the polarization state of the light. In addition, as long as the optical member 40 does not carry out multiple reflection, the uneven | corrugated | grooved part 40a may be formed in both surfaces of the optical member 40. FIG.

  FIG. 14 is a schematic sectional view showing a projection screen according to another embodiment of the present invention. 14 except that the flat portion 40b of the optical member 40 is formed on the surface on the observation side and the uneven portion 40a is formed on the surface on the polarization selective reflection layer 11 side. The others are substantially the same as the projection screen 10-1 shown in FIG. 1A. Regarding the configuration and function of each member of the projection screen 10-2 shown in FIG. 14, the description of the overlapping parts with the projection screen 10-1 will be omitted as appropriate.

  As shown in FIG. 14, in the projection screen 10-2, the right circularly polarized light 31 </ b> R projected on the projection screen 10-2 is diffused while the polarization state is maintained by the uneven portion 40 a of the optical member 40, The light enters the polarization selective reflection layer 11 as diffused light 31b1. Next, the diffused light 31b1 is diffusely reflected by the scattering property of the polarization selective reflection layer 11, and enters the optical member 40 in a state of being diffused in a substantially constant diffusion range as the diffused light 31b2. Thereafter, the diffused light 31b2 is diffused by the concavo-convex portion 40a of the optical member 40, and is emitted to the observation side as diffused light 31b3 (reflected light 33-2) in a state of being diffused in a wider diffusion range.

  Here, in the projection screen 10-2, since the flat portion 40b of the optical member 40 is formed on the surface on the observation side, a functional holding layer layer such as an antireflection layer can be easily provided on the flat portion 40b. it can.

  In the projection screen 10-2, since the concavo-convex portion 40 a of the optical member 40 and the polarization selective reflection layer 11 are opposed to each other, an air layer (gap) is generated between the optical member 40 and the polarization selective reflection layer 11. However, this gap can be filled with an adhesive having an appropriate refractive index, whereby desired optical characteristics can be maintained.

  Further, the optical member 40 can be provided on the observation side of the polarization selective reflection layer 11 so as to be peelable or non-peelable by an appropriate bonding method such as pressure bonding or adhesion. The luminance distribution and viewing angle can be improved.

  In the above description, the projection screen main body 10 constituting the projection screens 10-1 and 10-2 is provided with the polarization selective reflection layer 11 as shown in FIG. The case of using a polarization selective reflection layer 11 having a cholesteric liquid crystal structure having a cholesteric liquid crystal structure in which the direction of L varies within the layer is not described, but diffused reflection of light of a specific polarization component However, the present invention is not limited to this, and a layer including a polarization selective reflection layer having an arbitrary structure can be used.

  Specifically, for example, the polarization selective reflection layer 11 has a polarization selective reflection layer body that reflects a specific polarization component (for example, a cholesteric liquid crystal structure in a planar alignment state as shown in FIG. The polarization selective reflection layer) and a diffusing element that diffuses the light reflected by the polarization selective reflection layer main body. Thereby, since the polarization separation characteristic and the diffusion characteristic can be made independent, the respective characteristics can be easily controlled. The diffusing element is, for example, on the observation side of the polarization selective reflection layer, and is provided between the optical member 40 and the polarization selective reflection layer main body described above. Further, the diffusing element may be, for example, a bulk diffusing material, a surface diffusing material, a hologram diffusing material, or any combination of these diffusing materials. The bulk diffusing material may be, for example, particles disposed in a transparent medium. The surface diffusing material may be, for example, a structural surface, a fine structure surface, or a roughened surface. The diffusion provided by the diffusing material may be random, ordered, or partially ordered.

  The polarization selective reflection layer 11 may be a layer that diffusely reflects linearly polarized light as light of a specific polarization component. Here, the linearly polarized light can be divided into two polarization states and has two directions orthogonal to each other. Therefore, the direction of the linearly polarized light of the projector that emits the linearly polarized light and this layer is diffusely reflected. By matching the direction of linearly polarized light, the image can be displayed brightly. Examples of the layer that diffusely reflects linearly polarized light as light of a specific polarization component include, for example, a diffusive multilayer reflective polarizing material (such as DBEF manufactured by 3M) formed of materials having different refractive indexes. . Since linearly polarized light can be expressed by combining so-called P-polarized light (component parallel to the incident surface) and S-polarized light (component perpendicular to the incident surface), a layer that diffusely reflects this linearly polarized light If only the light of a specific polarization component (for example, P-polarized light or S-polarized light) is diffusely reflected, the contrast of the image can be increased similarly to the polarization selective reflection layer 11 described above, and the projected image light If P is mainly composed of P-polarized light or S-polarized light, the image light can be reflected efficiently.

  Furthermore, in the above, the case where the support base material 12 of the projection screen body 10 constituting the projection screens 10-1 and 10-2 is an absorption base material including a light absorption layer that absorbs light in the visible light region is an example. However, the present invention is not limited to this, and the support substrate 12 may be a transparent substrate that transmits at least part of light in the visible light region. In this case, although the advantage of increasing the contrast of the image is lost, the transparency of the projection screens 10-1 and 10-2 when the image is not displayed is high, so that the background can be seen through clearly. 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.

  Furthermore, in the above, in the projection screen body 10 constituting the projection screens 10-1 and 10-2, the partial selection between the polarization selective reflection layer 11 and the support base 12 or the polarization selective reflection layer 11 is selected. An intermediate layer (easily adhesive layer) having easy adhesion can be provided between the partially selective reflective layers adjacent to each other among the reflective layers 11a, 11b, and 11c. In addition to the property (or instead of easy adhesion), a barrier property may be provided. The barrier property referred to here means that when a polarization selective reflection layer is directly laminated on a support substrate, or when another partial selective reflection layer is directly laminated on one partial selective reflection layer, It refers to a function of preventing a constituent part from moving (penetrating) into an upper layer and an upper layer constituent part from moving (penetrating) into a lower layer. When a substance moves between the upper layer and the lower layer, the original optical function (wavelength selectivity, polarization selectivity, diffusibility, etc.) of the polarization selective reflection layer (or partial selective reflection layer) constituting the upper layer or the lower layer However, it can be prevented by using an intermediate layer (barrier layer) having a barrier property as described above. Specifically, for example, in the case of laminating another partially selective reflective layer on one partially selective reflective layer by applying a liquid crystalline composition having cholesteric regularity, the material and process conditions of the liquid crystalline composition In some cases, the nematic liquid crystal component contained in the liquid crystalline composition for forming the upper partial selective reflection layer penetrates into the lower partial selective reflection layer, and changes (increases) the helical pitch length of the lower partial selective reflection layer. ). However, even in this case, if a barrier layer is provided between the lower partial selective reflection layer and the upper partial selective reflection layer, such movement (penetration) of the nematic liquid crystal component is eliminated, and the partial selective reflection layer is eliminated. These optical functions (wavelength selectivity, polarization selectivity, diffusivity, etc.) can be maintained well.

  Examples of such a barrier layer include modified acrylate, urethane acrylate, polyester acrylate, and epoxy resin. These may be monofunctional or polyfunctional, and there are types of monomers and oligomers. Specifically, ethoxylated trimethylolpropane triacrylate, propoxylated glyceryl triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hydroxypentaacrylate, ethoxylated pentaerythritol tetraacrylate, pentaacrylate ester, pentaerythritol Triacrylate, trimethylolpropane triacrylate, trimethylolpropane PO modified triacrylate, isocyanuric acid EO modified triacrylate, trimethylolpropane EO modified triacrylate, dipentaerythritol penta and hexaacrylate, urethane adduct, aliphatic polyamine epoxy Resin, polyaminoamide epoxy resin Aromatic diamine epoxy resin, alicyclic diamine epoxy resin, phenol resin epoxy resin, amino resin epoxy resin, mercaptan compound epoxy resin, dicyandiamide epoxy resin, Lewis acid complex compound epoxy resin, etc. Can do.

Projection System The projection screens 10-1 and 10-2 described above can be used by being incorporated in a projection system 20 including a projector 21, as shown in FIG. Here, the projection system 20 in which the projection screen 10-1 is incorporated will be described as an example, but the basic configuration and operation of the projection system in which the other projection screen 10-2 is incorporated are the same. .

  As shown in FIG. 15, the projection system 20 includes a projection screen 10-1 and a projector 21 that projects image light on the projection screen 10-1.

  Among these, as the projector 21, a CRT, a liquid crystal projector, a DLP (digital light processing) projector, or the like can be used, but is not particularly limited. However, the image light projected on the projection screen 10-1 by the projector 21 is light having the same polarization component as the light component selectively reflected by the projection screen 10-1 (for example, right circularly polarized light). It is preferable to contain mainly.

  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, the linearly polarized light can be converted into circularly polarized light without loss of light quantity by emitting the image light emitted from the projector 21 through the phase difference plate 22 or the like as a polarization conversion element. it can.

  In addition, as the phase difference plate 22, what has a 1/4 wavelength phase difference is used preferably, and what specifically has a phase difference of 137.5 nm 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.

  As shown in FIG. 15, such a phase difference plate 22 may be incorporated in the projector 21 in addition to being externally attached to the exit of 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, it is caused by light having a polarization component different from the polarization component of light selectively reflected by the polarization selective reflection layer 11 of the projection screen 10-1 (for example, left circularly polarized light). It is possible to effectively prevent the occurrence of stray light and increase the contrast of the image. Note that when linearly polarized light is produced by the optical system inside the projector 21, only a retardation plate may be used without using a linearly polarizing plate.

  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. On the other hand, 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. For this reason, in the projection screen 10-1, it is preferable to selectively reflect only light in a wavelength region corresponding to the wavelength region of the image light projected by the projector 21. Thereby, reflection of light in the visible light range that is out of the above-described wavelength range among ambient light such as external light and illumination light can be prevented, and the contrast of the image can be increased.

  In addition, the projection system 20 is normally provided with the illumination light source 23 installed in the illumination light source installation part 25, such as an indoor ceiling, and illuminates the observation space where the projection screen 10-1 is installed.

  Here, as shown in FIG. 15, when the illumination light source 23 is arranged so that the illumination light 34 emitted from the illumination light source 23 is directly irradiated onto the projection screen 10-1, the illumination light source. The illumination light 34 emitted from the projector 23 toward the projection screen 10-1 mainly includes light having a polarization component different from the polarization component of light selectively reflected by the projection screen 10-1 (for example, left circularly polarized light). It is preferable to make it. Thereby, it is possible to effectively prevent the illumination light 34 from being reflected by the polarization selective reflection layer 11 of the projection screen 10-1 and to increase the contrast of the image. Here, the illumination light 34 is diffused by the optical member 40 provided on the observation side of the projection screen body 10 in the projection screen 10-1 and then enters the projection screen body 10. At this time, the illumination light 34 is diffused by the optical member 40, but the polarization state is maintained, so that the illumination light 34 is transmitted through the polarization selective reflection layer 11.

  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.

  In the projection system 20 shown in FIG. 15, the illumination light 34 emitted from the illumination light source 23 is directly irradiated onto the projection screen 10-1, but the present invention is not limited to this, as shown in FIG. The illumination light source 23 is installed in the illumination light source installation unit 26 other than the ceiling, and the illumination light 35 emitted from the illumination light source 23 is reflected on the projection screen 10-1 as illumination light 35 'via the illumination light reflector 27 such as the ceiling. The same can be applied to the case where the light is indirectly irradiated. However, in this case, since the polarization state of the circularly polarized light is reversed when the light is reflected by the illumination light reflector 27, the illumination light 35 emitted from the illumination light source 23 toward the illumination light reflector 27 is Similarly to the case shown in FIG. 15, by arranging a polarizing film 24 ′ that transmits right circularly polarized light, the light having the same polarization component as that of the light selectively reflected by the projection screen 10-1 (for example, It is preferable to include mainly right circularly polarized light. In addition, as polarizing film 24 ', the thing similar to the polarizing film 24 mentioned above can be used. Thereby, the illumination light 35 ′ whose polarization state is reversed by the illumination light reflector 27 is light having a polarization component different from the polarization component of the light selectively reflected by the projection screen 10-1 (for example, left circular polarization). Thus, it is possible to effectively prevent the illumination light 35 ′ from being reflected by the polarization selective reflection layer 11 of the projection screen 10-1, thereby increasing the contrast of the image. Here, the illumination light 35 ′ is diffused by the optical member 40 provided on the observation side of the projection screen body 10 in the projection screen 10-1, and then enters the projection screen body 10. At this time, the illumination light 34 is diffused by the optical member 40, but the polarization state is maintained, so that the illumination light 34 is transmitted through the polarization selective reflection layer 11.

  In the projection system 20, the projector 21 is normally disposed near the normal line of the approximate center of the projection screens 10-1 and 10-2. However, the present invention is not limited to this. It may be arranged. In such an arrangement relationship between the projector 21 and the projection screens 10-1 and 10-2 (so-called offset arrangement relationship), for example, in the optical member 40 provided on the observation side of the projection screen main body 10, it has been described above. Such a function may not be given to the entire area of the optical member 40, but may be given only to a limited area (for example, the upper half or the lower half).

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

(Example)
A first cholesteric compound having a selective reflection center wavelength at 440 nm is prepared by dissolving a monomer mixed liquid crystal in which a chiral agent (5.3 wt%) is added to a main agent (94.7 wt%) composed of an ultraviolet curable nematic liquid crystal and dissolved in cyclohexanone. A liquid crystal solution was prepared.

  Note that a liquid crystal containing a compound represented by the above chemical formula (2-xi) was used as the nematic liquid crystal.

  As the polymerizable chiral agent, the compound represented by the above chemical formula (5) was used.

  Further, 5% by weight of a photopolymerization initiator (Ciba Specialty Chemicals) was added to the first cholesteric liquid crystal solution.

  Then, the first cholesteric liquid crystal solution prepared as described above is placed on a support substrate (Lumirror / AC-X, manufactured by Panac Corporation) having an easy-adhesion layer formed on a 200 × 200 mm black PET film. The coating method was applied.

  Next, the film was heated in an oven at 80 ° C. for 90 seconds to perform alignment treatment (drying treatment) to obtain a cholesteric liquid crystal layer from which the solvent was removed.

Thereafter, the cholesteric liquid crystal layer was irradiated with 365 nm ultraviolet light at 50 mW / cm ² for 1 minute to cure the cholesteric liquid crystal layer, thereby obtaining a first partial selective reflection layer having a selective reflection center wavelength at 440 nm. .

  Similarly, the second cholesteric liquid crystal solution was directly applied on the first partially selective reflection layer, and an alignment treatment (drying treatment) and a curing treatment were performed. As a result, a second partial selective reflection layer having a selective reflection center wavelength at 550 nm was obtained. The second cholesteric liquid crystal solution is prepared by the same method as the first cholesteric liquid crystal solution, and the selective reflection center wavelength is set to 550 nm by controlling the mixing ratio of the nematic liquid crystal and the chiral agent. To have.

  Similarly, the third cholesteric liquid crystal solution was directly applied onto the second partially selective reflection layer, and subjected to alignment treatment (drying treatment) and curing treatment. As a result, a third partial selective reflection layer having a selective reflection center wavelength at 600 nm was obtained. The third cholesteric liquid crystal solution is prepared by the same method as the first cholesteric liquid crystal solution, and the selective reflection center wavelength is set to 600 nm by controlling the mixing ratio of the nematic liquid crystal and the chiral agent. To have.

  As described above, as the polarization selective reflection layer, the first partial selective reflection layer that selectively reflects light in the blue (B) wavelength region (light having a selective reflection center wavelength at 440 nm), and green (G) A second partial selective reflection layer that selectively reflects light in the wavelength range (light having a selective reflection center wavelength at 550 nm) and light in the red (R) wavelength range (light having a selective reflection center wavelength at 600 nm). A projection screen main body was obtained, in which the third partial selective reflection layer that selectively reflects () was laminated in order from the support substrate side. The thickness of the first partial selective reflection layer was 3 μm, the thickness of the second partial selective reflection layer was 4 μm, and the thickness of the third partial selective reflection layer was 5 μm. The cholesteric liquid crystal structure of each partial selective reflection layer of the polarization selective reflection layer of the projection screen thus obtained was not in the planar alignment state.

  And the projection screen 1 was obtained by sticking a hologram diffusion plate on the observation side of the polarization selective reflection layer of the projection screen main body thus obtained. The hologram diffusion plate is an LSD sheet (manufactured by Physical Optics Corporation) having a diffusion angle of 40 degrees. Further, a strong adhesive sheet manufactured by Panac Co. was used for attaching the polarization selective reflection layer and the hologram diffusion plate.

(Comparative example)
As the projection screen 2, a projection screen consisting only of the projection screen body used in the projection screen 1 was prepared. That is, the projection screen 2 is different from the projection screen 1 in that a hologram diffusion plate is not attached to the observation side of the polarization selective reflection layer.

(Evaluation results)
The projection screens 1 and 2 described above were installed perpendicular to the floor. Further, the projector was disposed at a position approximately 2.5 m away from the projection screens 1 and 2 in the direction perpendicular to the projection screens (direction parallel to the floor). Here, a DLP projector was used as the projector, and a circularly polarizing plate was attached to the exit of the projector so that the light emitted from the projector became circularly polarized light. In addition, a fluorescent lamp (polarization control was not performed) was used as indoor lighting. This fluorescent lamp is arranged above the projection screens 1 and 2 so that illumination light from the fluorescent lamp enters from above the projection screens 1 and 2.

  In this state, the projector projects image light (a still image whose viewing angle is easy to check) on the projection screens 1 and 2, observes the surface of the screen on which the image is projected, and further, Contrast was measured.

  As a result, in the projection screen 2, high visibility was obtained when observed from the vicinity of the front of the screen, but when observed from an oblique direction, the image became dark and the visibility was lowered.

  On the other hand, in the projection screen 1, the image did not become dark regardless of whether it was observed from the vicinity of the front of the screen or obliquely, and high visibility could be obtained.

1 is a schematic sectional view showing a projection screen according to an embodiment of the present invention. FIG. 1B is a schematic sectional view showing details of a projection screen main body of the projection screen shown in FIG. 1A. The schematic diagram for demonstrating the orientation state and optical function of the polarization selective reflection layer of the projection screen main body shown to FIG. 1B. FIG. 6 is a schematic cross-sectional view showing a modification of the projection screen main body shown in FIG. 1B. FIG. 6 is a schematic cross-sectional view showing another modification of the projection screen main body shown in FIG. 1B. FIG. 6 is a schematic cross-sectional view showing still another modification of the projection screen main body shown in FIG. 1B. FIG. 6 is a schematic cross-sectional view showing still another modification of the projection screen main body shown in FIG. 1B. FIG. 6 is a schematic cross-sectional view showing still another modification of the projection screen main body shown in FIG. 1B. FIG. 6 is a schematic cross-sectional view showing still another modification of the projection screen main body shown in FIG. 1B. FIG. 2 is a schematic cross-sectional view showing a modification of the projection screen shown in FIG. 1A. The conceptual diagram for demonstrating the display condition of the image | video in the projection system using the projection screen shown to FIG. 1A. The conceptual diagram for demonstrating the display condition of the image | video in the projection system which used the projection screen main body shown to FIG. 1B as a projection screen. FIG. 12 is a schematic sectional view for explaining an optical function of a projection screen used in the projection system shown in FIG. 11. It is a schematic sectional drawing which shows the detail of the optical member of the projection screen shown to FIG. 1A. FIG. 6 is a schematic sectional view showing a projection screen according to another embodiment of the present invention. Schematic which shows an example of the projection system provided with the projection screen shown to FIG. 1A. Schematic which shows the other example of the projection system provided with the projection screen shown to FIG. 1A.

Explanation of symbols

10-1, 10-2 Projection screen 10 Projection screen body 11 Polarization selective reflection layers 11a, 11b, 11c Partial selective reflection layers 12, 12A, 12B, 12C Support base material 13 Intermediate layer 14 Support film 15 Light absorption layer 16 Light reflection Layer 17 Adhesive layer 18 Release film 19 Functional holding layer 20 Projection system 21 Projector 22 Retardation plate 23 Illumination light source 24, 24 'Polarization film 25, 26 Illumination light source installation part 27 Illumination light reflector 30 Spiral structure region 31R Selective reflection Right circularly polarized light 31L in the wavelength region Left circularly polarized light 32R in the selective reflection wavelength region Right circularly polarized light 32L outside the selective reflection wavelength region Left circularly polarized light 31a1, 31a2, 31a3 outside the selective reflection wavelength region Diffused light 31b1, 31b2, 31b3 Diffused light 33-1 , 33-2, 33, 33A, reflected light 34, 35, 35 'illumination light 40 optical member 40a concave Part 40b flat portion 50 observer L helical axis

Claims (18)

In the projection screen that reflects the image light projected from the observation side and displays the image,
A polarization selective reflection layer that selectively diffuses and reflects light of a specific polarization component;
A projection screen, comprising: a polarization maintaining diffusion layer that is provided on the observation side of the polarization selective reflection layer and diffuses image light diffusely reflected by the polarization selective reflection layer while maintaining its polarization state.   2. The projection screen according to claim 1, wherein the polarization maintaining diffusion layer has a concavo-convex portion formed on the observation side surface of the polarization maintaining diffusion layer.   2. The projection screen according to claim 1, wherein the polarization maintaining diffusion layer has a concavo-convex portion formed on a surface of the polarization maintaining diffusion layer on the polarization selective reflection layer side.   The projection screen according to claim 1, wherein the polarization maintaining diffusion layer is at least one optical member selected from the group consisting of frosted glass and holographic optical elements.   The projection screen according to claim 1, wherein the light of the specific polarization component is right circularly polarized light or left circularly polarized light.   The projection screen according to claim 1, wherein the light of the specific polarization component is one linearly polarized light.   The polarization selective reflection layer includes: a polarization selective reflection layer main body that reflects light of the specific polarization component; and a diffusion element that diffuses light reflected by the polarization selective reflection layer main body. Item 7. The projection screen according to any one of Items 1 to 6.   The projection screen according to claim 1, wherein the polarization selective reflection layer itself has diffusibility.   The projection according to claim 8, wherein the polarization selective reflection layer has a cholesteric liquid crystal structure, and diffuses light of the specific polarization component due to structural nonuniformity of the cholesteric liquid crystal structure. screen.   The projection screen according to claim 9, wherein the cholesteric liquid crystal structure includes a plurality of spiral structure regions having different spiral axis directions.   The projection screen according to claim 1, further comprising a support base material that supports the polarization selective reflection layer.   The projection screen according to claim 11, wherein the support substrate is an absorption substrate including a light absorption layer that absorbs light in a visible light region.   The projection screen according to claim 11, wherein the support substrate is a transparent substrate that transmits at least part of light in a visible light region.   The projection screen according to claim 1, wherein the polarization selective reflection layer includes at least two partial selective reflection layers stacked on each other.   The projection screen according to claim 14, wherein an intermediate layer having a barrier property is provided between adjacent partial selective reflection layers of the polarization selective reflection layer.   The projection screen according to claim 14, wherein an intermediate layer having easy adhesion is provided between adjacent partial selective reflection layers of the polarization selective reflection layer.   The functional holding layer including at least one layer selected from the group consisting of a hard coat layer, an antireflection layer, an ultraviolet absorption layer, and an antistatic layer is further provided. The projection screen according to one item. A projection screen according to any one of claims 1 to 17,
A projection system comprising: a projector that projects image light on the projection screen.

Images