JP2005070768A - Projection screen and projection system provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection screen capable of sharply displaying an image by minimizing the influence of the loss of light that occurs on a polarized-light selective reflection layer and of providing high image visibility. <P>SOLUTION: The projection screen includes: a polarized-light selective reflection layer 11 that selectively reflects a specific polarized-light component; and a substrate 12 that supports the polarized-light selective reflection layer 11. The polarized-light selective reflection layer 11 includes a plurality of partial selective reflection layers 11a, 11b and 11c that are laminated to one another, and the partial selective reflection layers have cholesteric liquid crystalline structures, owing to which they selectively reflect a specific polarized-light component. The cholesteric liquid crystalline structure of each partial selective reflection layer 11a, 11b and 11c comprises a plurality of helical structure parts that are different in direction of helical axis, and, owing to structural non-uniformity in the cholesteric liquid crystalline structure, diffuses light (reflected light 33) that is selectively reflected. <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, includes a projection screen excellent in visibility capable of clearly displaying an image and the same. It relates to a projection system.

  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.

  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).
JP-A-5-107660 JP 2002-540445 A

  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. In addition, a projection screen using a hologram has a problem that it is difficult to increase the screen size due to manufacturing problems.

  On the other hand, in the projection screen using the polarization separation layer, the white display portion can be brightened while the black display portion can be made darker, which is brighter than that using the hologram as described above. Images can be clearly displayed under light.

  Regarding the projection screen using such a polarization separation layer, the present inventor previously provided a polarization selective reflection layer having a cholesteric liquid crystal structure, and reduces the visibility of the image due to the structural nonuniformity of the cholesteric liquid crystal structure. Japanese Patent Application No. 2003-165687 proposes a projection screen that can give a scattering effect to reflected light of image light without any problem.

  The present invention is an improvement over the invention described in Japanese Patent Application No. 2003-165687, and is capable of displaying images clearly with minimal effects of light loss in the polarization selective reflection layer. An object of the present invention is to provide a projection screen excellent in performance and a projection system including the projection screen.

  As a first solution, the present invention provides a polarization selective reflection layer that selectively reflects light of a specific polarization component in a projection screen that reflects projected image light and displays an image, and is laminated on each other. A polarization selective reflection layer having at least two partial selective reflection layers, each partial selective reflection layer having a structure that selectively reflects light of a specific polarization component, and each partial selective reflection The structures of the layers are different from each other so as to selectively reflect light in different wavelength ranges among the red (R), green (G), and blue (B) wavelength ranges, Projection characterized in that a partial selective reflection layer that selectively reflects light in the green (G) wavelength region is disposed on the far side from the image light projection side of the polarization selective reflection layer. Provide a screen.

  In the first solving means described above, the light of the specific polarization component is preferably right circularly polarized light or left circularly polarized light. The light of the specific polarization component may be one linearly polarized light.

  In the first solving means described above, it is preferable to further include a diffusing element for diffusing the light reflected by the polarization selective reflection layer, or to make the polarization selective reflection layer itself diffusive.

  Further, in the first solving means described above, the polarization selective reflection layer has a cholesteric liquid crystal structure, and due to the structural nonuniformity of the cholesteric liquid crystal structure, the selectively reflected light can be diffused. preferable. In this case, it is preferable that the cholesteric liquid crystal structure of each of the partial selective reflection layers includes a plurality of spiral structure regions having different spiral axis directions.

  Furthermore, in the first solving means described above, a support base material that supports the polarization selective reflection layer including the partial selective reflection layers, and selectively reflects light in the green (G) wavelength region. It is preferable to further include a support base disposed on the side of the partially selective reflection layer. The support substrate may be an absorption substrate including a light absorption layer that absorbs light in the visible light region, or a transparent substrate that transmits at least part of light in the visible light region. Also good.

  Furthermore, in the first solving means described above, it is preferable that an intermediate layer having easy adhesion or barrier properties is provided between adjacent partial selective reflection layers of the polarization selective reflection layer.

  Furthermore, in the first solving means described above, a functional holding layer including at least one layer selected from the group consisting of a hard coat layer, an antiglare layer, an antireflection layer, an ultraviolet absorption layer and an antistatic layer is further provided. It is preferable to provide. Here, when the functional retention layer is an antiglare layer, the antiglare layer is preferably composed of an isotropic layer having an irregular uneven shape, for example, a TAC having a mat surface. A film may be used. An uneven shape may be formed on the surface of the polarized light selective reflection layer on which video light is projected, and the anti-glare function may be imparted to the polarized light selective reflection layer by the uneven shape.

  Furthermore, in the first solving means described above, each of the partial selective reflection layers is preferably made of a polymerizable liquid crystal material.

  The present invention provides, as a second solution means, a projection system comprising the projection screen according to the first solution means described above and a projector that projects image light on the projection screen. .

  According to the present invention, the structure of each partial selective reflection layer of the polarization selective reflection layer selectively reflects light in different wavelength ranges among the red (R), green (G), and blue (B) wavelength ranges. And the partial selective reflection layer that selectively reflects light in the green (G) wavelength region among the partial selective reflection layers, and the side on which the image light is projected among the polarization selective reflection layers It is arranged on the far side. Here, the light in the wavelength range of each color incident from the observation side is reflected by the corresponding partial selective reflection layer of the polarization selective reflection layer and returns to the observation side, but each partial selective reflection layer has a specific color. In addition to the selective reflection wavelength region that selectively reflects light in the wavelength region of the light, it has a sideband that selectively reflects light outside the wavelength region of the specific color (polarization selection having cholesteric regularity) FIG. 8 shows the case of a reflective layer). For this reason, a part of the light reflected by a partial selective reflection layer and returning to the observation side is reflected by the sideband of the partial selective reflection layer located closer to the observation side than the partial selective reflection layer, and a part thereof is stray light. This causes light loss. In the present invention, as described above, the partial selective reflection layer that selectively reflects light in the green (G) wavelength range with high visibility is formed of red (R) and blue (B) with low visibility. Since it is arranged on the side farther from the observation side than the partially selective reflection layer that selectively reflects light in the wavelength range, loss of light in the red (R) and blue (B) wavelength ranges with low visibility. The light in the red (R), green (G) and blue (B) wavelength ranges can be reflected in a balanced manner from the viewpoint of visibility, and as a result, the image can be displayed clearly. Can do.

  In addition, according to the present invention, each partial selective reflection layer of the polarization selective reflection layer selectively reflects only light of a specific polarization component (for example, right circularly polarized light). It is possible to reflect only about 50% of ambient light such as 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, the projected image light mainly includes light having the same polarization component as that of the light selectively reflected by each partial selective reflection layer of the polarization selective reflection layer (for example, right circularly polarized light). By doing so, the projected image light can be reflected almost 100% by each partial selective reflection layer of the polarization selective reflection layer, and the image light can be efficiently reflected.

  Furthermore, according to the present invention, each partial selective reflection layer of the polarization selective reflection layer has a cholesteric liquid crystal structure, and the cholesteric liquid crystal structure has structural nonuniformity (for example, a spiral included in the cholesteric liquid crystal structure). If the direction of the spiral axis of the structural region varies), the image light is diffusely reflected instead of being specularly reflected, so that the image can be easily viewed. At this time, each partial selective reflection layer of the polarization selective reflection layer diffuses the selectively reflected light due to the structural non-uniformity of the cholesteric liquid crystal structure, so that the light of a specific polarization component is diffused. While reflecting, other light can be transmitted without being diffused. For this reason, there is no problem of so-called depolarization in which the polarization state of the ambient light and image light transmitted through each partial selective reflection layer of the polarization selective reflection layer is disturbed, and the original polarization separation function of the polarization selective reflection layer The visibility of the video can be improved while maintaining the above.

  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.

  As shown in FIG. 1, the projection screen 10 according to the present embodiment reflects an image light projected from the observer side (the upper side of the drawing) and displays an image, and has a specific polarization component. A polarization selective reflection layer 11 that selectively reflects light (for example, right circularly polarized light) and a support base 12 that supports the polarization selective reflection layer 11 are provided.

  Among these, the polarization selective reflection layer 11 includes three partial selective reflection layers 11a, 11b, and 11c stacked on each other, and each of the partial selective reflection layers 11a, 11b, and 11c is light of a specific polarization component. Has a cholesteric liquid crystal structure that selectively reflects light.

  Here, each of the partial selective reflection layers 11a, 11b, and 11c is made of a liquid crystalline composition exhibiting cholesteric regularity, and a director of liquid crystal molecules is continuous in the thickness direction of the layer as a physical molecular arrangement of liquid crystal molecules. It has a spiral structure.

  The partial selective reflection layers 11a, 11b, and 11c are polarized light that separates 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. Has separation characteristics. That is, in each of the partial selective reflection layers 11a, 11b, and 11c, the unpolarized 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 rest is reflected. This phenomenon is known as circular dichroism, and when a spiral direction in the spiral structure of liquid crystal molecules is appropriately selected, a circularly polarized component having the same optical rotation direction as this spiral direction is selectively reflected.

In this case, the maximum optical rotation light scattering occurs at the wavelength λ ₀ of the following equation (1).
λ ₀ = nav · p (1)
Here, p is the helical pitch length in the helical structure of the liquid crystal molecules (the length per pitch of the molecular helix of the liquid crystal molecules), and nav is the average refractive index in a plane 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. 1, unpolarized light incident from the viewer side of the projection screen 10 (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). 32L) belongs 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 characteristics as described above in each of the partial selective reflection layers 11a, 11b, and 11c. One circularly polarized component (for example, the right circularly polarized light 31R within the selective reflection wavelength region) is reflected as reflected light 33, and the other light (for example, the left circularly polarized light 31L within the selective reflection wavelength region, the right circularly polarized light 32R outside the selective reflection wavelength region, and the like) Left circularly polarized light 32L) is transmitted. FIG. 8 is a schematic diagram showing a selective reflection spectrum of such reflected light 33. As shown in FIG. 8, each of the partial selective reflection layers 11 a, 11 b, and 11 c is in addition to the selective reflection wavelength range that selectively reflects light in a specific color wavelength range, and other than the specific color wavelength range. Sidebands that selectively reflect the light.

  Note that the cholesteric liquid crystal structure of each of the partial selective reflection layers 11a, 11b, and 11c 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. The “diffusion” caused by the structural non-uniformity of the cholesteric liquid crystal structure allows the observer to recognize the reflected light (image light) reflected by the projection screen 10 as an image. To spread or scatter to the extent.

  On the other hand, a general cholesteric liquid crystal structure is in a planar alignment state, and as shown in FIG. 2B, in the polarization selective reflection layer 11 ′, each spiral structure region 30 included in the cholesteric liquid crystal structure. The directions of the helical axis L all extend uniformly in parallel with the layer thickness direction, and the selectively reflected light (reflected light 36) is specularly reflected.

  Here, the cholesteric liquid crystal structures of the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 shown in FIG. 1 are red (R) and green included in a visible light region (for example, a wavelength region of 400 to 700 nm). The helical pitch lengths are different from each other so as to selectively reflect light in different wavelength regions of the (G) and blue (B) wavelength regions. In addition, as a wavelength range of red (R), green (G), and blue (B) here, the wavelength range of video light projected by a projector such as a liquid crystal projector (for example, each partial selective reflection layer 11a, It is preferable to use a selective reflection center wavelength of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm) with reference to the case where light is incident perpendicular to 11b and 11c.

  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, in the present embodiment, in order to minimize the influence of light loss, as shown in FIG. 1, a partial selective reflection layer 11a that selectively reflects light in the green (G) wavelength region; The partial selective reflection layer 11b that selectively reflects light in the blue (B) wavelength region and the partial selective reflection layer 11c that selectively reflects light in the red (R) wavelength region are supported in this order. The layers are laminated in order from the substrate 12 side. That is, the partial selective reflection layer 11a that selectively reflects light in the green (G) wavelength region is disposed on the side of the polarization selective reflection layer 11 that is far from the image light projection side (the support base material 12 side). It is arranged.

  In addition, the thickness of each partial selective reflection layer 11a, 11b, 11c is a magnitude | size of the grade which reflects the light of the specific polarization state selectively reflected substantially 100% (a magnitude | size which is a grade which a reflectance is saturated). It is preferable that This is because video light cannot be efficiently reflected if the reflectance is less than 100% with respect to light of a specific polarization component that is selectively reflected (for example, right circularly polarized light). The reflectivity of each of the partial selective reflection layers 11a, 11b, and 11c directly depends on the number of helical pitches. However, if the helical pitch length is fixed, each partial selective reflection layer 11a is indirectly used. , 11b, and 11c. 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 thicknesses of the partial selective reflection layers 11a, 11b, and 11c are not as good as they are thick. If they are too thick, it becomes difficult to control the orientation, unevenness, etc. Since the degree of light absorption increases, the above-mentioned range is appropriate.

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, the support base 12 is formed using an acrylic plate or a plastic film (for example, a black PET film kneaded with carbon) in which a black pigment is kneaded (in this case, the support base 12 Or a light absorption layer made of a black pigment or the like may be formed on the surface of either side of a transparent support film such as a plastic film. Thereby, light that should not be reflected as reflected light among unpolarized light incident from the viewer side of the projection screen 10 (left circularly polarized light within the selective reflection wavelength region, right circularly polarized light outside the selective reflection wavelength region, and left (Circularly polarized light) and light incident from the back side of the projection screen 10 are absorbed to effectively prevent generation of reflected light caused by ambient light such as outside light and illumination light, and stray light caused by image light. can do.

  The plastic film used as the material for the support substrate 12 includes polycarbonate polymers, polyester polymers such as polyethylene terephthalate, polyimide polymers, polysulfone polymers, polyethersulfone polymers, and polystyrene films. Thermoplastic polymers such as polymers, polyolefin polymers such as polyethylene and polypropylene, polyvinyl alcohol polymers, cellulose acetate polymers, polyvinyl chloride polymers, polyacrylate polymers, polymethyl methacrylate polymers The film which consists of etc. can be used. In addition, the material of the support base material 12 is not limited to this, Materials, such as a metal, paper material, cloth material, glass, can also be used.

  In addition, when laminating | stacking each partial selection reflection layer 11a, 11b, 11c on the support base material 12, after apply | coating the liquid crystalline composition which shows a cholesteric regularity, as mentioned later, an orientation process and a hardening process are carried out. It is common to do it.

  In this case, since the cholesteric liquid crystal structures of the partial selective reflection layers 11a, 11b, and 11c need to be controlled so as not to be in the planar alignment state, the support substrate 12 is a surface on the side on which the liquid crystalline composition is applied. It is preferable to use one having no orientation ability. However, even if the material on the surface of the support substrate 12 on which the liquid crystalline composition is applied has an orientation ability on the surface, such as a stretched film, the support substrate 12 By subjecting the surface of the stretched film to surface treatment, and controlling the material of the liquid crystalline composition and the process conditions for aligning the liquid crystalline composition, the cholesteric of each of the partially selective reflection layers 11a, 11b, 11c The liquid crystal structure can be controlled so as not to be in the planar alignment state.

Next, a method for manufacturing the projection screen 10 as described above will be described.
First, the support base material 12 on which the polarization selective reflection layer 11 is laminated is prepared. At this time, the surface of the support substrate 12 on the side on which the liquid crystalline composition is applied should not have alignment ability.

  Next, after applying a liquid crystalline composition exhibiting cholesteric regularity on the support substrate 12 prepared in this manner, the first partially selective reflective layer 11a is subjected to an alignment treatment and a curing treatment. Are laminated (fixed).

  Hereinafter, details of each process (application process, alignment process process, and curing process process) for laminating (adhering) the first partial selective reflection layer 11a 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 a partially selective reflection layer 11a 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. The selective reflection center wavelength caused by the molecular structure of the polymerizable liquid crystal material can be controlled by changing the chiral power by changing the type of the chiral agent or by changing the concentration of the chiral agent. 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 forming a partially selective reflection layer having a cholesteric regularity with a short helical pitch length, a chiral agent having an optically active site to be contained in the liquid crystalline composition is a chiral agent having a large effect of inducing a helical structure. It is preferable to select an agent. Specifically, it is preferable to use a low molecular compound having axial asymmetry in the molecule as represented by the following general formula (3), (4) or (5). .

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

  In addition, such a chiral agent does not need to have polymerizability in particular. However, when the chiral agent has polymerizability, it is polymerized with a polymerizable liquid crystal material exhibiting nematic regularity, and the cholesteric regularity is stably fixed, so in terms of thermal stability, etc. Highly preferred. In particular, it is preferable to have a polymerizable functional group at both ends of the molecule in order to obtain a partially selective reflection layer 11a with 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 partial selective reflection layer 11a 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. You may make it ink.

  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.

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

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

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

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

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

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

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

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

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

  The method (3) is a method of curing the cholesteric liquid crystal layer by photopolymerizing liquid crystal molecules in the liquid crystalline composition by irradiation with radiation. In this method, an electron beam, ultraviolet rays, or the like can be appropriately used as radiation according to conditions. Usually, ultraviolet rays are preferably used from the viewpoint of easiness of the apparatus, and the wavelength is 250 to 400 nm. 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.

  Thereafter, by repeating the above-described series of steps (coating step, alignment treatment step, and curing treatment step), another cholesteric liquid crystal layer (partial selective reflection layer) is sequentially laminated on the partial selective reflection layer 11a, and a plurality of steps are performed. It is possible to manufacture the projection screen 10 including the polarization selective reflection layer 11 composed of the partial selective reflection layers 11a, 11b, and 11c. That is, while controlling the selective reflection center wavelength of the liquid crystalline composition exhibiting cholesteric regularity to be applied, a plurality of cholesteric liquid crystal layers are sequentially laminated on the support substrate 12 to obtain a green color as the polarization selective reflection layer 11. The partial selective reflection layer 11a that selectively reflects light in the wavelength range (B), the partial selective reflection layer 11b that selectively reflects light in the blue (B) wavelength range, and the red (R) wavelength range It is possible to manufacture the projection screen 10 in which the partial selective reflection layer 11c that selectively reflects the light is sequentially laminated in this order from the support base material 12 side.

  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 such as an easy adhesion layer may be provided between the cholesteric liquid crystal layers to be laminated.

  As described above, according to the present embodiment, in the cholesteric liquid crystal structures of the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11, the wavelength ranges of red (R), green (G), and blue (B) The spiral pitch lengths are made different from each other so as to selectively reflect light in different wavelength regions, and light in the green (G) wavelength region is selected from the partial selective reflection layers 11a, 11b, and 11c. The partially selective reflection layer 11a that reflects the light is disposed on the side of the polarization selective reflection layer 11 that is far from the side on which the image light is projected (the support substrate 12 side). That is, the partial selective reflection layer 11a that selectively reflects light in the green (G) wavelength region with high visibility is selectively used for light in the red (R) and blue (B) wavelength regions with low visibility. It arrange | positions in the side (support base material 12 side) far from the observation side rather than the partial selection reflection layers 11b and 11c to reflect. Therefore, for the light in the green (G) wavelength region that is reflected by the partial selective reflection layer 11a and returns to the observation side, the sidebands of the partial selective reflection layers 11b and 11c that are located closer to the observation side than the partial selective reflection layer 11a. (Refer to FIG. 8). Some of the light is lost, but the light in the blue (B) and red (R) wavelength regions reflected by the partial selective reflection layers 11b and 11c and returning to the observation side. Is less light loss than light in the green (G) wavelength region. This is because only the partial selective reflection layer 11c exists on the observation side of the partial selective reflection layer 11b that selectively reflects light in the blue (B) wavelength range, and light in the red (R) wavelength range. This is because there is no partial selective reflection layer on the observation side with respect to the partial selective reflection layer 11c that selectively reflects. From the above, light loss in the red (R) and blue (B) wavelength regions with low visibility is minimized, and light in the red (R), green (G) and blue (B) wavelength regions is reduced. Reflection can be performed in a balanced manner from the viewpoint of visibility, and as a result, an image can be clearly displayed.

  In addition, according to the present embodiment, each of the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 has only a specific polarization component (for example, right circularly polarized light) due to the polarization separation characteristic of the cholesteric liquid crystal structure. Therefore, it is possible to reflect only about 50% of ambient light such as external light or illumination light having no polarization characteristic 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, the projected image light has the same polarization component as that of the light selectively reflected by the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 (for example, right circularly polarized light). ) Can be reflected substantially 100% by the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11, and the image light can be efficiently reflected. Can do.

  Furthermore, according to the present embodiment, the cholesteric liquid crystal structure of each of the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 has structural nonuniformity, and the helical structure region included in the cholesteric liquid crystal structure Since the direction of the spiral axis L of 30 varies, the image light is diffusely reflected, not specularly reflected, and the image is easily visible. At this time, each of the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 diffuses the selectively reflected light due to the structural nonuniformity of the cholesteric liquid crystal structure. Light (for example, the right circularly polarized light 31R within the selective reflection wavelength region) is reflected while diffusing, while the other light (for example, the left circularly polarized light 31L within the selective reflection wavelength region, the right circularly polarized light 32R outside the selective reflection wavelength region, and the left circle) is reflected. The polarized light 32L) can be transmitted without being diffused. For this reason, there is no problem of so-called depolarization in which the polarization state of the ambient light and the image light transmitted through the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 is disturbed, and the polarization selective reflection layer. Thus, it is possible to improve the visibility of the image while maintaining the 11 original polarization separation function.

  In the embodiment described above, the polarization selective reflection layer 11 selects the partial selective reflection layer 11a that selectively reflects light in the green (G) wavelength region and the light in the blue (B) wavelength region. The case where the partial selective reflection layer 11b that reflects automatically and the partial selective reflection layer 11c that selectively reflects light in the red (R) wavelength range are sequentially laminated in this order from the support base material 12 side is taken as an example. Although mentioned and demonstrated, the order of lamination | stacking of each partial selection reflection layer 11a, 11b, 11c is not necessarily restricted to this. That is, of the partial selective reflection layers 11a, 11b, and 11c, the partial selective reflection layer 11a that selectively reflects light in the green (G) wavelength region is from the side of the polarized light selective reflection layer 11 where the image light is projected. As long as it is arranged on the far side (supporting substrate 12 side), light in the wavelength range of green (G) is selectively used in the mode shown in FIG. 3 in addition to the mode shown in FIG. A partial selective reflection layer 11a that reflects light, a partial selective reflection layer 11c that selectively reflects light in the red (R) wavelength region, and a partial selective reflection that selectively reflects light in the blue (B) wavelength region. You may make it laminate | stack the layer 11b in order from the support base material 12 side in this order. Note that the light in the red (R) and blue (B) wavelength regions has lower visibility than the light in the green (G) wavelength region. The order is arbitrary.

  In the above-described embodiment, the wavelength ranges of red (R), green (G), and blue (B) are represented as three selective reflection wavelength ranges that are independent of each other. Although the case where each is realized by each of the corresponding partial selective reflection layers among the three partial selective reflection layers 11a, 11b, and 11c has been described as an example, red (R), green (G), and blue In the case where at least two wavelength ranges in the wavelength range (B) are continuously connected, the polarization selective reflection layer 11 can be constituted by two partial selective reflection layers. Here, taking as an example a case where the wavelength range of red (R) and green (G) is included in one selective reflection wavelength range, the polarization selective reflection layer 11 is configured as shown in FIG. ) And green (G) wavelength selective reflection layer 11d selectively reflective, blue (B) wavelength selective reflection layer selective reflection layer 11b selectively reflective in this order They are laminated in order from the support base 12 side. Even in this case, the partial selective reflection layer 11d that selectively reflects light in the green (G) wavelength region is farther from the image light projection side of the polarization selective reflection layer 11 (the support base 12 side). ), The loss of light in the red (R) and blue (B) wavelength regions with low visibility is minimized, and red (R), green (G) and blue (B) Light in the wavelength range can be reflected with a good balance from the viewpoint of visibility.

  As described in the above embodiment, the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 are most preferably those having a cholesteric liquid crystal structure having structural non-uniformity. However, the present invention is not limited to this, and the following polarization selective reflection layer can also be used.

  That is, in the above-described embodiment, the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 are those having a cholesteric liquid crystal structure that selectively reflects right circularly polarized light or left circularly polarized light. However, the present invention is not limited to this, and one having a structure that selectively reflects one linearly polarized light such as a linearly polarizing element such as a multilayer reflective polarizing material may be used.

  Furthermore, in the embodiment described above, the selectively reflected light is diffused as the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 due to the structural non-uniformity of the cholesteric liquid crystal structure. However, as long as the visibility of an image is ensured, a cholesteric liquid crystal structure having a planar alignment state and selectively reflecting specularly reflected light may be used.

  Furthermore, in the above-described embodiment, each of the partial selective reflection layers 11a, 11b, and 11c of the polarization selective reflection layer 11 itself has diffusibility. However, the present invention is not limited to this, and is reflected by the polarization selective reflection layer 11. A diffusing element that diffuses the light may be provided separately from the polarization selective reflection layer 11.

  Furthermore, in the above-described embodiment, it is preferable to use a support substrate 12 that does not have alignment ability on the surface on which the liquid crystalline composition is applied. When the surface on the side on which the composition is applied has orientation ability, as shown in FIG. 5, the partial selective reflection layer 11 a and the support group on the support base material 12 side in the polarization selective reflection layer 11. By providing an intermediate layer 13 such as an easy-adhesion layer between the material 12, the orientation state of the cholesteric liquid crystal structure of each of the partial selective reflection layers 11 a, 11 b, 11 c is controlled, and in particular, partial selective reflection on the support base 12 side Of the cholesteric liquid crystal structure of the layer 11a, the director of liquid crystal molecules in the vicinity of the interface with the intermediate layer 13 may be directed in a plurality of directions. In addition, when providing intermediate | middle layers 13, such as an easily bonding layer, the adhesiveness between the partial selection reflection layer 11a by the side of the support base material 12 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 (partial selective reflection layer 11a) and the material of the support base material 12, and generally What is marketed can be used. 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 absorption layer that kneads a black pigment or the like and absorbs light in the visible light region, like the supporting base material. If necessary, as shown in FIG. 5, intermediates such as easy adhesion between adjacent partial selective reflection layers among the partial selective reflection layers 11 a, 11 b, and 11 c laminated on the support substrate 12. The layer 13 may be provided.

  Furthermore, in the above-described embodiment, a functional holding layer 19 may be provided on the observation side surface of the projection screen 10 (polarization selective reflection layer 11) as shown in FIG. As the functional retention layer 19, various types can be used. For example, a hard coat layer (HC layer), an antiglare layer (AG 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 to prevent scratches and dirt. The antiglare layer (AG layer) is a layer for preventing the projection screen 10 from being roughened. The antireflection layer (AR layer) is a layer for suppressing reflection of light on the surface of the projection screen 10. 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. The antistatic layer (AS layer) is a layer for removing static electricity generated in the projection screen 10. In the case where the functional holding layer 19 is used as an antistatic layer, the functional holding layer 19 is not necessarily provided on the observation side surface of the projection screen 10, and is not provided on the back side of the support base 12. The support substrate 12 itself may be provided with a function of removing static electricity by kneading carbon particles or the like into the support substrate 12.

  The functional holding layer 19 used as an antiglare layer plays a role of preventing a phenomenon in which the space in which the viewer is present is reflected on the surface of the projection screen 10, and is important for viewing images well. It is. In this case, as the antiglare layer, a transparent layer having a concavo-convex shape on the surface is preferably used, thereby effectively preventing a mirror-like image from being formed due to interface reflection on the projection screen 10 surface. can do. In addition, as a method for forming such a transparent layer, for example, a sandblast method, a surface shape transfer at the time of mold formation, a chemical treatment, or other various methods such as a transparent resin or glass surface. A method of shaping the uneven shape can be used. Here, the concavo-convex shape formed on the surface of the transparent layer may be irregular or regular. In this case, in order not to impair the polarization separation function of the polarization selective reflection layer 11, the antiglare layer is preferably a layer having an isotropic refractive index. As a material for the antiglare layer, for example, glass, acrylic resin, polyester resin, or the like can be used, and a TAC (triacetyl cellulose) film having a mat surface can also be used.

  In addition, when providing the anti-glare function to the projection screen 10, as shown to Fig.6 (a), in addition to implement | achieving an anti-glare layer by the functional holding layer 19 separate from the polarization selective reflection layer 11, As shown in FIG. 6B, an uneven shape (see reference numeral 11e) is formed on the observation-side surface of the polarization selective reflection layer 11 (the surface of the partial selective reflection layer 11c positioned closest to the observation side). Thus, the anti-glare function may be imparted to the polarization selective reflection layer 11 itself.

  Furthermore, in the above-described embodiment, the case where the support base 12 of the projection screen 10 is an absorption base including a light absorption layer that absorbs light in the visible light range has been described as an example. Not limited to this, the support substrate 12 may be a transparent substrate that transmits at least part of light in the visible light range. In this case, the advantage of increasing the contrast of the video is lost, but the transparency of the projection screen 10 when the video is not displayed is high, so that the background can be seen through clearly and installed in a show window. It can be used with high design. 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.

  Further, in the above-described embodiment, in the projection screen 10, between the polarization selective reflection layer 11 and the support base 12, or among the partial selective reflection layers 11 a, 11 b, 11 c constituting the polarization selective reflection layer 11. As described above, the intermediate layer 13 (adhesive layer) having easy adhesion can be provided between the adjacent partial selective reflection layers. In addition (or instead of easy adhesion), barrier properties 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 type 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 screen 10 described above can be used by being incorporated in a projection system 20 having a projector 21 as shown in FIG.

  As shown in FIG. 7, the projection system 20 includes a projection screen 10 and a projector 21 that projects image light on the projection screen 10.

  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 onto the projection screen 10 by the projector 21 mainly includes light having the same polarization component as the light component selectively reflected by the projection screen 10 (for example, right circularly polarized light). preferable.

  Here, when a liquid crystal projector is used as the projector 21, in many cases, substantially linearly polarized light is emitted from the operation principle. In such a case, linearly polarized light can be converted into circularly polarized light without loss of light quantity by emitting the image light emitted from the projector 21 via the phase difference plate 22 or the like.

  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. 7, 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, the amount of light of the projector 21 itself is halved, but stray light 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 (for example, left circularly polarized light). It is possible to effectively prevent the occurrence of the above and increase the contrast of the image.

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

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

(Example)
Prepare a first cholesteric liquid crystal solution having a selective reflection center wavelength at 550 nm by dissolving a monomer-mixed liquid crystal in which a chiral agent (5 wt%) is added to a main agent (95 wt%) composed of an ultraviolet curable nematic liquid crystal in cyclohexanone. did.

  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.

  Furthermore, 5 wt% of an acetophenone photopolymerization initiator manufactured by Ciba Specialty Chemicals was added to the first cholesteric liquid crystal solution.

  And the 1st cholesteric liquid crystal solution adjusted as mentioned above was apply | coated by the bar-coat method on a 200 mm □ black acrylic board.

  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 is irradiated with ultraviolet light of 365 nm at 10 mW / cm ² for 1 minute in a nitrogen atmosphere to cure the cholesteric liquid crystal layer, thereby partially selective reflection of the first layer having a selective reflection center wavelength at 550 nm. A layer was obtained.

  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 450 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 450 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 green (G) wavelength region (light having a selective reflection center wavelength at 550 nm), and the blue (B) A second partial selective reflection layer that selectively reflects light in the wavelength range (light having a selective reflection center wavelength at 450 nm) and light in the red (R) wavelength range (light having a selective reflection center wavelength at 600 nm). A projection screen was obtained in which the third partial selective reflection layer that selectively reflects () was sequentially laminated in this order from the support substrate side. The thickness of the first partial selective reflection layer was 4 μm, the thickness of the second partial selective reflection layer was 3 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.

(Comparative example)
Except for changing the order in which the first cholesteric liquid crystal solution, the second cholesteric liquid crystal solution, and the third cholesteric liquid crystal solution are applied, a polarization selective reflection layer is manufactured by the same method as the above-described embodiment, A first partially selective reflection layer that selectively reflects light in the blue (B) wavelength range (light having a selective reflection center wavelength at 450 nm) and light in the green (G) wavelength range (selective reflection at 550 nm). A second partial selective reflection layer that selectively reflects light having a central wavelength) and three layers that selectively reflect light in the red (R) wavelength region (light having a selective reflection central wavelength at 600 nm). A projection screen was obtained in which the partial selective reflection layer of the eyes was laminated in this order from the support substrate side.

(Evaluation results)
The image light emitted from the projector was projected on each projection screen according to the example and the comparative example, and the contrast was measured. A liquid crystal projector (ELP-52, manufactured by Epson Corporation) was used as the projector.

  Here, a circularly polarizing plate was disposed at the exit of the projector so that the emitted image light was circularly polarized. In addition, the indoor lighting where the projector and the projection screen are installed is performed by a fluorescent lamp installed on the ceiling (which emits non-polarized light) and is illuminated on the projection screen at an angle of about 50 degrees from the ceiling. They were placed in such a relationship that they were irradiated with light. At this time, the brightness just below the projection screen was 200 lux (lx) as measured by an illuminometer (digital illuminometer 510-02, manufactured by Yokogawa M & C).

  The projection screen was installed perpendicular to the floor. In addition, the projector was arranged at a position approximately 2.5 m away from the projection screen in a direction perpendicular to the projection screen (a direction parallel to the floor).

  In this state, image light (a still image with white and black areas) was projected onto the projection screen by the projector, and the contrast of the image was measured. Specifically, the luminance of each of the white and black images at the center of the projection screen is measured with a luminance meter (luminance meter BM-8, manufactured by Topcon Corporation), and the ratio is determined as the contrast (contrast = brightness of the white image). ÷ Intensity of black image).

Table 1 below shows the contrast of each projection screen according to the example and the comparative example. As shown in Table 1 below, sufficient contrast was obtained with each projection screen according to the example and the comparative example.

  Moreover, although each projection screen was observed visually, in this case, each projection screen of the example and the comparative example was able to visually recognize images satisfactorily.

  However, the position where the incident light of the image light is oblique (in a state where the image light (the still image with the red, green, and blue pattern patterns) is projected onto the projection screens according to the example and the comparative example by the projector ( When the image is visually observed at a position of an angle of 15 ° or more with the normal direction of the screen plane being 0 °, the image of the projection screen according to the example is more vivid than the projection screen according to the comparative example. Is displayed.

1 is a schematic sectional view showing a projection screen according to an embodiment of the present invention. The schematic diagram for demonstrating the orientation state and optical function of the polarization selective reflection layer of the projection screen shown in FIG. FIG. 6 is a schematic sectional view showing a modification of the projection screen shown in FIG. 1. FIG. 10 is a schematic cross-sectional view showing another modification of the projection screen shown in FIG. 1. FIG. 10 is a schematic cross-sectional view showing still another modification of the projection screen shown in FIG. 1. FIG. 10 is a schematic cross-sectional view showing still another modification of the projection screen shown in FIG. 1. Schematic which shows an example of the projection system provided with the projection screen which concerns on one embodiment of this invention. The figure which shows the selective reflection spectrum of the reflected light reflected by the polarization selective reflection layer (partial selective reflection layer) which has cholesteric regularity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Projection screen 11 Polarization selective reflection layer 11a, 11b, 11c, 11d Partial selection reflection layer 11e Uneven shape 12 Support base material 13 Intermediate | middle layer 19 Functional maintenance layer 20 Projection system 21 Projector 22 Phase difference plate 30 Spiral structure area | region 31R selection Right circularly polarized light 31L within the reflection wavelength region Left circularly polarized light 32R within the selective reflection wavelength region Right circularly polarized light 32L outside the selective reflection wavelength region Left circularly polarized light 33 outside the selective reflection wavelength region Reflected light

Claims (18)

In the projection screen that reflects the projected image light and displays the image,
A polarization selective reflection layer that selectively reflects light of a specific polarization component, the polarization selective reflection layer having at least two partially selective reflection layers stacked on each other;
Each of the partial selective reflection layers has a structure that selectively reflects light of a specific polarization component, and each of the partial selective reflection layers includes red (R), green (G), and blue (B). A partial selective reflection layer that selectively reflects light in the green (G) wavelength region among the partial selective reflection layers, so as to selectively reflect light in different wavelength regions of A projection screen, characterized in that the projection screen is disposed on a side farther from a side on which image light is projected in the polarization selective reflection layer.   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 having the specific polarization component is one linearly polarized light.   4. The projection screen according to claim 1, further comprising a diffusing element that diffuses light reflected by each of the partial selective reflection layers of the polarization selective reflection layer. 5.   5. The projection screen according to claim 1, wherein each of the partial selective reflection layers of the polarization selective reflection layer has diffusibility itself.   Each of the partial selective reflection layers of the polarization selective reflection layer has a cholesteric liquid crystal structure, and diffuses light selectively reflected due to structural nonuniformity of the cholesteric liquid crystal structure. The projection screen according to claim 5.   The projection screen according to claim 6, wherein the cholesteric liquid crystal structure of each of the partial selective reflection layers includes a plurality of spiral structure regions having different spiral axis directions.   A support base material that supports the polarized light selective reflection layer including the partial selective reflection layers, and is disposed on the side of the partial selective reflection layer that selectively reflects light in the green (G) wavelength region. The projection screen according to claim 1, further comprising a base material.   The projection screen according to claim 8, 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 8, wherein the supporting base material is a transparent base material that transmits at least part of light in a visible light region.   The projection screen according to any one of claims 1 to 10, wherein an intermediate layer having easy adhesion is provided between adjacent partial selective reflection layers of the polarization selective reflection layer. .   The projection screen according to claim 1, wherein an intermediate layer having a barrier property 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 antiglare layer, an antireflection layer, an ultraviolet absorption layer, and an antistatic layer is further provided. The projection screen according to claim 12.   The projection screen according to claim 13, wherein the functional holding layer is an antiglare layer, and the antiglare layer is composed of a layer having an irregular uneven shape and an isotropic refractive index.   The projection screen according to claim 14, wherein the antiglare layer is a TAC film having a mat surface.   2. An uneven shape is formed on a surface of the polarization selective reflection layer on which video light is projected, and the anti-glare function is imparted to the polarization selective reflection layer by the uneven shape. A projection screen according to any one of claims 12 to 12.   The projection screen according to claim 1, wherein each of the partial selective reflection layers is made of a polymerizable liquid crystal material. 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.

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