JP4184186B2 - Projection screen - Google Patents

Description

  The present invention relates to a projection screen used for projection by a projector, for example.

  2. Description of the Related Art Conventionally, a projection system for projecting light from a projector onto a projection screen and projecting an image or the like is used for business use or home use.

  A projection screen used in such a projection system usually has a transparent or translucent porous fine particle held in a transparent medium and a reflective material disposed behind the transparent fine particle. 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 was a problem of being.

  In order to solve such problems, a projection screen (see Patent Document 1) that suppresses reflection of external light or the like using cholesteric liquid crystal has been proposed. However, since the surface of the cholesteric liquid crystal is a mirror surface, since the projected light is specularly reflected, it has not been put into practical use.

  As another method, Patent Document 2 discloses a projection screen that uses a diffusive multilayer reflective polarizer or the like as a reflective polarization element. In addition to preventing reflection of light, the reflection of the reflected light is imparted by interfacial reflection of materials having different refractive indexes constituting the multilayer reflective polarizing material or by a diffusing element provided separately from the multilayer reflective polarizing material. Things are listed. Further, the projection screen uses a cholesteric reflective polarizing material as a reflective polarizing element, and the reflective polarizing element and the diffusing element are used in combination. In addition, there is also described that the light is not reflected, and a scattering effect is given to the reflected light by a diffusing element provided separately from the cholesteric reflective polarizing material.

  However, the former described in Patent Document 2 is based on a linear polarization element such as a multilayer reflective polarizing material (such as DBEF manufactured by 3M), and is incorporated in a projection system or the like. When used, 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, good image display cannot be realized. There was a problem.

  Moreover, in the latter thing described in the said patent document 2, although circularly polarizing elements, such as a cholesteric reflective polarizing material, are used as a reflective polarizing element, the spreading | diffusion provided in the observer side of the reflective polarizing element Since the 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.

  In other words, since the diffusing element is provided on the viewer 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 (which is Called "bias"). 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 in that the visibility of images cannot be sufficiently improved.

  In addition, since the projection screen is wound into a cylindrical shape, for example, when stored, there is a drawback in that the surface is rubbed together and frictional scratches are likely to occur.

JP-A-5-107660 Special Table 2002-540445

  In view of the above, it is desired to provide a projection screen that can be used even in a bright environment and has high brightness and scratch resistance.

  The present invention includes a base material and a polarization selective reflection layer having a cholesteric liquid crystal structure which is formed on the base material and selectively reflects light of a specific polarization component, and the light irradiated from the projector is The polarization selective reflection layer has a structure in which the cholesteric liquid crystal structure is structurally non-uniform so that the projected light is diffused by separating polarized light. The projection screen is characterized in that a hard coat layer for preventing the surface of the projection screen from being damaged is provided on the outermost surface on the projector side.

  In the present invention, by providing a hard coat layer, it is possible to improve the scratch resistance, for example, when the projection screen is rolled up, for example, when stored, the surface is rubbed together, and the friction scratches easily. Such scratches can be made difficult to protect and the surface of the projection screen can be protected. Further, the polarization selective reflection layer impairs the polarization separation function of the projected light because the cholesteric liquid crystal structure is structurally non-uniform so that the projected light is diffused by separating the polarized light. It is possible to make the projection screen excellent in image visibility. Further, by polarizing the light projected from the projector into a predetermined circularly polarized light, the projected light can be efficiently reflected. Furthermore, since the influence of reflection of external light can be prevented by the specific wavelength reflectivity and circular polarization of the cholesteric liquid crystal, a projection screen with high brightness can be obtained even in a bright environment.

  In the present invention, the hard coat layer preferably has a pencil hardness of 2H or more according to JIS K 5400. This is because a hard coat layer having a hardness within the above range is sufficiently effective in improving the scratch resistance of the projection screen.

  Furthermore, in the present invention, the hard coat layer preferably has an antireflection function for suppressing reflection of outside light or an antiglare function for preventing glare of the projection screen. This is because, in the present invention, a projection screen having a simple structure and excellent quality can be efficiently manufactured by using a hard coat layer having such other functions.

  Furthermore, in the present invention, it is preferable that the polarization selective reflection layer has a wavelength region having a reflection intensity that is more than half of the maximum reflection intensity of the polarization selective reflection layer in only a part of the visible light region. This makes it possible to selectively reflect light having a specific wavelength in the visible light range. In addition, by matching the specific wavelength range to the light from the projector, etc., only the image light is efficiently reflected, and the amount of light reflected by the cholesteric liquid crystal structure is reduced for external light and illumination light. This is because a projection screen with high brightness can be obtained even in a brighter environment.

  In the present invention, the polarization selective reflection layer has a selective reflection center wavelength in a range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm on the basis of a case where light is perpendicularly incident on the polarization selective reflection layer. It is preferable to selectively reflect light existing in the light source. This is because, for example, it is possible to reflect the light in the three primary color wavelength ranges irradiated from a liquid crystal projector or the like, and to obtain a projection screen capable of good color display.

  In the present invention, by providing a hard coat layer, it is possible to improve the scratch resistance, for example, when the projection screen is rolled up, for example, when stored, the surface is rubbed together, and the friction scratches easily. Such scratches can be made difficult to protect and the surface of the projection screen can be protected. Further, the polarization selective reflection layer impairs the polarization separation function of the projected light because the cholesteric liquid crystal structure is structurally non-uniform so that the projected light is diffused by separating the polarized light. It is possible to make the projection screen excellent in image visibility. Further, by polarizing the light projected from the projector into a predetermined circularly polarized light, the projected light can be efficiently reflected. Furthermore, since the influence of reflection of external light can be prevented by the specific wavelength reflectivity and circular polarization of the cholesteric liquid crystal, a projection screen with high brightness can be obtained even in a bright environment.

  The projection screen of the present invention will be described below.

  The projection screen of the present invention has a base material and a polarization selective reflection layer having a cholesteric liquid crystal structure that is formed on the base material and selectively reflects light of a specific polarization component, and is irradiated from the projector. The polarization selective reflection layer, wherein the cholesteric liquid crystal structure is structurally non-uniformly formed so that the projected light is separated and diffused. The outermost surface of the projection screen on the projector side is provided with a hard coat layer for preventing the surface of the projection screen from being damaged.

  For example, as shown in FIG. 1, the projection screen of the present invention includes a base material 1 and a polarization selective reflection layer 2 formed on the base material 1, and further, the surface of the projection screen 5 is damaged. For protection, a hard coat layer 3 is formed on the outermost surface of the projection screen 5 on the projector 10 side. In the present invention, since the cholesteric liquid crystal structure of the polarization selective reflection layer 2 is structurally non-uniform so that the projected light is separated and diffused, the projection is projected from the projector 10. The diffused light can be diffused and reflected.

  In the present invention, the polarization selective reflection layer is made of a liquid crystalline composition exhibiting cholesteric regularity, and the liquid crystal molecule director rotates continuously in the thickness direction of the layer as the physical molecular arrangement of the liquid crystal molecules. Based on the physical molecular arrangement of such liquid crystal molecules, it has polarization separation characteristics that separates a circularly polarized light component in one direction and a circularly polarized light component in the opposite direction. is doing. That is, in the polarization selective reflection layer, 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 other is reflected. The This phenomenon is known as circular dichroism, and when a spiral direction in the spiral structure of liquid crystal molecules is appropriately selected, a circularly polarized component having the same optical rotation direction as this spiral direction is selectively reflected.

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

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

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

Δλ = Δn · p (2)
That is, for example, as shown in FIG. 2, unpolarized light (right circularly polarized light 11R and left circularly polarized light 11L within the selective reflection wavelength region, right circularly polarized light 12R outside the selective reflection wavelength region, and the like, which is incident from the viewer side of the projection screen. The left circularly polarized light 12L) has one circularly polarized component (for example, selective reflection) 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 11R in the wavelength range is reflected as reflected light 13, and other light (for example, left circular polarized light 11L in the selective reflection wavelength range, right circular polarized light 12R and left circular polarized light 12L outside the selective reflection wavelength range) is transmitted. .

  Therefore, according to the present invention, the projected light can be efficiently reflected by using the polarization selective reflection layer as a layer that reflects a specific wavelength of polarized light on the same side as the light emitted from a projector or the like. Therefore, a projection screen with high brightness can be obtained. In addition, for external light, illumination light, and the like, only light having a specific wavelength is reflected by the polarization selective reflection layer, and light having other wavelengths is not reflected. As a result, it is possible to transmit more than half of the wavelengths included in the external light and the like, and a projection screen with high brightness can be obtained even in an environment where illumination light, external light, or the like exists.

  Hereinafter, each configuration of the projection screen of the present invention will be described.

1. First, the hard coat layer used in the projection screen of the present invention will be described. The hard coat layer used in the projection screen of the present invention is a member that is formed on the outermost surface of the projection screen on the projector side and prevents the projection screen surface from being damaged.

  The hardness of the hard coat layer in the present invention is not particularly limited as long as it can hardly cause damage such as frictional scratches. Specifically, the pencil hardness according to JIS K 5400 is 2H. It is preferable that it is above, and above all, it is preferable that it is 4H or more. If the hard coat layer has a hardness in the above range, for example, even when the projection screen is wound and stored, the surface is less likely to be scratched, and the scratch resistance of the projection screen can be improved. is there.

  Further, such a hard coat layer is not particularly limited as long as it has a hard coat function that protects the surface of the projection screen from scratches, but in addition to the hard coat function, it is a hard coat layer having other functions. There may be. For example, other functions include an antireflection function that suppresses reflection of external light, an antiglare function that prevents glare on the surface of the projection screen, and an ultraviolet ray that is absorbed to prevent yellowing of the polarization selective reflection layer due to ultraviolet rays. And UV absorbing function. In the present invention, the hard coat layer preferably has at least one of the antireflection function, the antiglare function, and the ultraviolet absorption function. This is because a projection screen having a simple structure and excellent quality can be efficiently manufactured.

  For example, as shown in FIG. 4A, the polarization selective reflection layer 2 is formed on the substrate 1, and the hard coat layer 40a is formed on the outermost surface of the projection screen 5 on the projector side. If the hard coat layer 40a contains an ultraviolet absorber having a function of absorbing ultraviolet rays, the hard coat layer 40a having an ultraviolet absorption function can be obtained. Further, as shown in FIG. 4B, the surface of the hard coat layer 40b formed on the outermost surface of the projection screen 5 on the projector side is made uneven so that glare of the projection screen 5 is prevented. It can be set as the hard coat layer 40b which has a function. Moreover, although not shown in figure, it can be set as the hard-coat layer which has an antireflection function by forming a hard-coat layer so that reflection of external light can be suppressed. Furthermore, it may be a case having an ultraviolet absorption function and one of an antireflection function and an antiglare function. That is, it may be a hard coat layer having an ultraviolet absorption function and an antireflection function, or a hard coat layer having an ultraviolet absorption function and an antiglare function.

  The hard coat layer in the present invention is located on the outermost surface on the projector side of the projection screen. For example, as shown in FIG. 4C, an antireflection layer 41 is formed on the polarization selective reflection layer 2. Further, when the antiglare layer 42 is laminated on the antireflection layer 41 and the ultraviolet absorbing layer 43 is laminated on the antiglare layer 42, the outermost surface on the projector side of such a projection screen. Since the member located at is the ultraviolet absorbing layer 43, a hard coat layer having an ultraviolet absorbing function can be obtained by forming the ultraviolet absorbing layer 43 so as to have a hard coat function. Separately from the above-mentioned members, a hard coat layer having only a hard coat function is formed on the ultraviolet absorbing layer, thereby having each member such as an ultraviolet absorbing layer, and further, the outermost component on the projector side. A projection screen having a hard coat layer formed on the surface can be obtained.

  Examples of the resin for forming such a hard coat layer include a thermosetting resin, a thermoplastic resin, an ultraviolet curable resin, an electron beam curable resin, and a two-component mixed resin. Among these, an ultraviolet curable resin capable of efficiently forming a hard coat layer by a simple treatment by a curing treatment by ultraviolet irradiation is preferable.

  Examples of the ultraviolet curable resin include various types such as polyester, acrylic, urethane, amide, silicone, and epoxy, and examples include ultraviolet curable monomers, oligomers, and polymers. Of these, urethane-based ones are preferred. Examples of the ultraviolet curable resin preferably used include those having an ultraviolet polymerizable functional group, particularly those containing an acrylic monomer or oligomer component having 2 or more, particularly 3 to 6 functional groups.

  Further, in order to adjust the hardness of the hard coat layer, it may be formed by containing fine particles. Specifically, those having transparency such as various metal oxides, glass, and plastic can be used without particular limitation. For example, inorganic fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide and antimony oxide, polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, Examples thereof include crosslinked or uncrosslinked organic fine particles and silicone fine particles composed of various polymers such as benzoguanamine, melamine, and polycarbonate.

  The shape of the fine particles is not particularly limited, and may be a bead-shaped sphere or may be an indeterminate type such as a powder. These fine particles can be used by appropriately selecting one kind or two or more kinds. The average particle diameter of the fine particles is 1 to 10 μm, preferably 2 to 5 μm. The fine particles may be dispersed and impregnated with ultrafine metal oxide particles for the purpose of controlling the refractive index and imparting conductivity.

  The content of the fine particles is appropriately determined in consideration of the average particle size of the fine particles, the film thickness of the hard coat layer, and the like, but is generally in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the resin. Among them, it is preferable to be within the range of 5 to 15 parts by weight.

  In addition, you may use a photoinitiator, a leveling agent, a thixotropy agent, an antistatic agent etc. as an additive.

  In addition, as a method for forming a hard coat layer, generally, a hard coat layer forming coating solution in which each of the above-described materials is dissolved or dispersed in an appropriate solvent is applied, dried and cured. In this case, examples of the solvent used for the hard coat layer forming coating solution include toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, isopropyl alcohol, and ethyl alcohol.

  The film thickness of the hard coat layer in the present invention is preferably in the range of 0.1 to 100 μm, and more preferably in the range of 1 to 10 μm. If the film thickness is thinner than the above range, if there is a hard coat function that protects the surface of the projection screen and other functions such as an antireflection function, these functions may not be sufficiently obtained. If the film thickness is made larger than the above range, these functions are sufficiently achieved, but it is not preferable because the light projected from the projector may be prevented from being transmitted and the brightness may be lowered.

2. Next, the polarization selective reflection layer used in the projection screen of the present invention will be described. The polarization selective reflection layer used in the projection screen of the present invention is formed on a base material to be described later, and has a cholesteric liquid crystal structure that selectively reflects light of a specific polarization component, and the projected light is polarized. The cholesteric liquid crystal structure is structurally nonuniform so as to be separated and diffused.

  Here, to make the cholesteric liquid crystal structure structurally non-uniform means that when the polarization selective reflection layer is oriented, the orientation directions of the liquid crystal phases are not uniform and are in a disordered state. To do. Specifically, as shown in FIG. 3, the direction of the helical axis L of the helical structure region 30 included in the cholesteric liquid crystal structure of the polarization selective reflection layer 2 varies, although not shown, a nematic layer surface (liquid crystal A state in which at least part of the molecular directors are the same in the XY directions) is not parallel to the plane of the polarization selective reflection layer (when a cross-sectional TEM photograph of the dyed cholesteric liquid crystal structure film is taken) Examples include a state in which a continuous curve of layers appearing in a pattern is not parallel to the substrate surface), a state in which fine particles of cholesteric liquid crystal are dispersed as a pigment, and the like. In either case, the cholesteric liquid crystal structure is structurally non-uniform so that the projected light is diffused with its polarization separated, so that the image light projected from the projector is diffused rather than specularly reflected. Reflected and the image becomes easy to see. At this time, the polarization selective reflection layer diffuses selectively reflected light due to its structural non-uniformity, so that while reflecting light of a specific polarization component while diffusing, other light is reflected. Can be transmitted without being diffused. For this reason, the problem of depolarization does not occur with respect to the environmental light and video light transmitted through the polarization selective reflection layer, and the visibility of the video can be improved while maintaining the polarization separation function of the polarization selective reflection layer.

  For example, the method for forming the cholesteric liquid crystal structure in a non-uniform manner in this way is not particularly limited, but for example, a method in which a substrate described later does not have a certain orientation, A method of adjusting the amount of a photopolymerization initiator or a leveling agent generally used for forming a reflective layer, a method of adding a non-liquid crystalline polymerizable compound in a polarization selective reflection layer, and incorporating liquid crystalline fine particles Methods and the like. These methods are arbitrarily selected, and these methods may be used in combination.

  Further, “diffusion” caused by the structural non-uniformity of the cholesteric liquid crystal structure as described above is that the observer recognizes the reflected light (image light) reflected by the projection screen 5 as an image as shown in FIG. To spread or scatter to the extent that can be done.

  Here, in the polarization selective reflection layer used in the present invention, the wavelength region having a reflection intensity of more than half of the maximum reflection intensity of the polarization selective reflection layer is a visible light region (for example, a wavelength region of 400 nm to 700 nm). It is preferable that it is only a part. This makes it possible to selectively reflect light having a specific wavelength in the visible light range. As described above, since the cholesteric liquid crystal strongly reflects light having a specific wavelength, light having a wavelength other than the specific wavelength is almost absorbed by the substrate or the like. Therefore, when external light, illumination light, or the like is incident on the projection screen, reflection of external light or illumination light is made by making the wavelength region of light strongly reflected by the cholesteric liquid crystal structure part of visible light. This is because a projection screen with high brightness can be obtained even in a brighter environment. The wavelength range reflected by the cholesteric liquid crystal constituting the polarization selective reflection layer is determined by the length of the helical pitch of the cholesteric liquid crystal.

  In addition, the polarization selective reflection layer of the present invention may be composed of one type of helical pitch length as long as it can reflect light having a wavelength irradiated from a light source such as a projector. When the wavelength band of red (R) and green (G) is included in the wavelength bandwidth of the selective reflection wavelength band with one spiral pitch length, the spiral pitch length of these wavelengths and the blue (B) spiral It is preferable to have a pitch length, and it is particularly preferable to have a helical pitch length of each wavelength of red (R), blue (B), and green (G). This is because the light normally emitted from the projector consists of red (R), blue (B), and green (G), and color display is realized by these three primary colors.

  In the present invention, although it depends on the type of the projector, the above wavelengths are specifically 430 nm to 460 nm for blue (B), 540 nm to 570 nm for green (G), and 580 nm to 620 nm for red (R). It is preferable to selectively reflect the wavelength. This is because a color screen can be displayed even if there is a difference in wavelength depending on the design of the apparatus, the type of light source, and the like, and a projection screen capable of expressing good white can be obtained.

  Such a polarization selective reflection layer having a plurality of helical pitch lengths can be formed by laminating layers having a cholesteric liquid crystal structure each having a helical pitch length.

  Moreover, it is preferable that the polarization selective reflection layer (each layer in the case where the polarization selective reflection layer is composed of a plurality of layers) has a thickness that reflects 100% of specific polarized light. The reflectance of the polarization selective reflection layer with respect to the polarization depends on the thickness of the polarization selective reflection layer, and is less than 100% with respect to light of a specific polarization component (for example, right circularly polarized light) that is selectively reflected. This is because the image light cannot be reflected efficiently if the reflectance is. In order to set the reflectance to 100%, it is usually preferable to set the pitch to 4 to 8 pitches. Specifically, although it depends on the type of material of the polarization selective reflection layer and the wavelength of specific polarization, 1 μm to 10 μm. If it is thinner than the above film thickness, the reflectance will be low, making it difficult to reproduce the image projected on the projection screen with good brightness, and if it is thicker than the above film thickness, it will be difficult to control the cholesteric liquid crystal structure. This is because unevenness may occur.

  Here, as the material of the polarization selective reflection layer described above, chiral nematic liquid crystal or cholesteric liquid crystal can be used, and any material having cholesteric regularity is not particularly limited. A polymerizable liquid crystal material having a polymerizable functional group at the terminal is preferable. This is because an optically stable projection screen can be obtained after curing. In addition, when the polymerizable liquid crystal material exhibits nematic regularity or smectic regularity, a polymerizable chiral agent may be used. Hereinafter, the material used for the polarization selective reflection layer of the present invention and the method for forming the polarization selective reflection layer will be described.

(1) Polymerizable liquid crystal material As an example of the polymerizable liquid crystal material having such a polymerizable functional group, for example, compound (I) represented by the following general formula (1) can be given. As the compound (I), it is also possible to use a mixture of two compounds included in the general formula (1). Furthermore, it may be composed of the compound (I) and the compound (II) represented by the following general formulas (2) to (12).

  As the compound (I), two kinds of compounds included in the general formula (1) can be mixed and used.

In the general formula (1) representing the compound (I), R ¹ and R ² each represent hydrogen or a methyl group, but R ¹ and R ² are both hydrogen due to the wide temperature range showing the liquid crystal phase. preferable. 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, a and b which show the chain length of the (meth) acryloyloxy group of the molecular chain both ends of compound (I), and the alkylene group which is a spacer with an aromatic ring are respectively arbitrary integers in the range of 2-12. Although it can take, it is preferable that it is the range of 4-10, and it is more preferable that it is the range of 6-9. The compound of the general formula (1) in which a = b = 0 is poor in stability, is susceptible to hydrolysis, and has high crystallinity. In addition, the compound of the general formula (1) in which a and b are each 13 or more has a low isotropic transition temperature (TI). For this reason, both of these compounds are not preferred because the temperature range showing liquid crystallinity is narrow.

  In the example described above, an example of a polymerizable liquid crystal monomer has been described. However, in the present invention, a polymerizable liquid crystal oligomer, a polymerizable liquid crystal polymer, or the like can be used. As such a polymerizable liquid crystal oligomer and a polymerizable liquid crystal polymer, those conventionally proposed can be appropriately selected and used.

(2) Chiral agent In the present invention, a chiral nematic liquid crystal having a cholesteric regularity obtained by adding a chiral agent to a nematic liquid crystal can also be suitably used.

  The chiral agent used in the present invention is a low molecular compound having an optically active site and means a compound having a molecular weight of 1500 or less. The chiral agent is mainly used for the purpose of inducing a helical pitch in the positive uniaxial nematic regularity expressed by the polymerizable liquid crystal material as shown in, for example, the compound (I) or the compound (II) used as necessary. . As long as this object is achieved, the polymerizable liquid crystal material, for example, the compound (I) or a mixture of the compound (I) and the compound (II) is compatible with each other in a solution state or a molten state, and the above nematic regularity is obtained. As long as the desired helical pitch can be induced in the polymerizable liquid crystal material without impairing the liquid crystallinity of the polymerizable liquid crystal material, the kind of the low-molecular compound as a chiral agent shown below is not particularly limited. It is preferable to have a polymerizable functional group in order to obtain an optical element having good heat resistance. It is essential that the chiral agent used for inducing a helical pitch in the liquid crystal has at least some chirality in the molecule. Accordingly, the chiral agent that can be used in the present invention 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, a chiral sulfoxide, Alternatively, compounds having axial asymmetry such as cumulene and binaphthol can be exemplified. More specifically, commercially available chiral nematic liquid crystal, for example, S-811 manufactured by Merck Co., etc. may be mentioned.

  However, depending on the properties of the selected chiral agent, nematic regularity destruction and orientation formed by the polymerizable liquid crystal material as exemplified by compound (I) or a mixture of compound (I) and compound (II) Or when the compound is non-polymerizable, the curability of the liquid crystalline composition may be lowered and the reliability of the cured film may be lowered. Furthermore, the use of a large amount of a chiral agent having an optically active site causes an increase in the cost of the composition. Therefore, when producing a circularly polarized light controlling optical element having a short pitch cholesteric regularity, a helical pitch is induced in a chiral agent having an optically active site to be contained in the polymerizable liquid crystal material used in the present invention. It is preferable to select a chiral agent having a large effect. Specifically, the low molecular compound (III) having axial asymmetry in the molecule as represented by the general formula (13), (14) or (15) Use is preferred.

In the general formula (13) or (14) representing the chiral agent (III), 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) It is preferable that Moreover, d and e which show the chain length of an alkylene group can take arbitrary integers in the range of 2-12 individually, but it is preferable that it is the range of 4-10, and is the range of 6-9. Is more preferable. The compound of general formula (13) or (14) in which the value of d or e is 0 or 1 lacks stability, is susceptible to hydrolysis, and has high crystallinity. On the other hand, a compound having a d or e value of 13 or more has a low melting point (Tm). These compounds are less compatible with the compound (I) exhibiting liquid crystallinity or with the mixture of the compound (I) and the compound (II), and may cause phase separation depending on the concentration.

  The amount of the chiral agent blended in the polymerizable liquid crystal material of the present invention is determined in consideration of the helical pitch inducing ability and the cholesteric property of the finally obtained circularly polarized light controlling optical element. Specifically, although it varies greatly depending on the polymerizable liquid crystal material to be used, 0.01 to 60 parts by weight, preferably 0.1 to 40 parts by weight, more preferably 100 parts by weight of the total amount of the polymerizable liquid crystal material. Is selected in the range of 0.5 to 30 parts by weight, most preferably 1 to 20 parts by weight. When the blending amount is less than the above range, the polymerizable liquid crystal material may not be provided with sufficient cholesteric properties. When the blending amount exceeds the above range, the orientation of the molecule is inhibited and adversely affects when cured by actinic radiation. There is a risk of affecting.

  In the present invention, it is not essential that such a chiral agent has polymerizability. However, in consideration of the thermal stability and the like of the obtained polarization selective reflection layer, it is preferable to use a polymerizable chiral agent that can be polymerized with the above-described polymerizable liquid crystal material and fix the cholesteric regularity.

(3) Others In addition to the polymerizable liquid crystal material and the chiral agent, the polarization selective reflection layer used in the present invention may be a photopolymerization initiator, a sensitizer, a leveling agent, or the like, if necessary. A material used for such a polarization selective reflection layer may be appropriately used.

  Examples of the photopolymerization initiator used in the present invention include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, benzoyl methyl benzoate, and 4-benzoyl-4'-methyl diphenyl sulfide. Benzylmethyl ketal, dimethylaminomethyl benzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3'-dimethyl-4-methoxybenzophenone, methylobenzoyl formate, 2 -Methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, -(4 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-propoxythioxanthone And so on. 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.

  Here, the addition amount of the photopolymerization initiator used in the present invention is 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. Is preferred.

  In the present invention, as described above, the cholesteric liquid crystal structure is structurally structured so that the polarized light selectively reflects and diffuses the polarized light by adjusting the addition amount of these materials. In some cases, they are formed unevenly. For example, by adding a large amount of the photopolymerization initiator, the molecular chain of the cholesteric liquid crystal can be shortened, and the orientation of the cholesteric liquid crystal surface can be disturbed. In this case, the photopolymerization initiator after completion of the reaction also serves as an impurity that disturbs the orientation of the cholesteric liquid crystal in the cholesteric liquid crystal.

  Also, by adding a non-liquid crystalline polymerizable compound having no liquid crystal orientation, the orientation of the cholesteric liquid crystal is disturbed and can be formed structurally non-uniformly. Further, it may be a case where the orientation of the cholesteric liquid crystal is disturbed by adding liquid crystal fine particles. In the present invention, the above methods may be used in combination, and the type and amount of these additives are appropriately selected depending on the purpose and the like.

(4) Formation of polarization selective reflection layer In the present invention, the above-mentioned polarization selective reflection layer can be obtained by applying a composition obtained by mixing the above-mentioned materials onto a substrate described later, orienting and solidifying. it can.

  As a method of applying the composition on the substrate, the composition obtained by mixing the above materials may be applied as it is, but from the viewpoint of adjusting the viscosity and orientation, it is used by dissolving in an organic solvent. Is preferred. In this case, the solvent used is not particularly limited as long as it does not erode the base material described later. For example, acetone, 3-methoxybutyl acetate, diglyme, cyclohexanone, tetrahydrofuran, toluene, xylene, chlorobenzene , Methylene chloride, methyl ethyl ketone, and the like can be used. In this case, the composition is usually diluted to 5% to 50% by weight, particularly 10% to 30% by weight.

  In addition, as a method for applying the composition, a generally used method can be used. For example, a roll coating method, a gravure coating method, a bar coating method, a slide coating method, a die coating method, a slit coating method. It can be carried out by a method, a dipping method or the like. When the substrate is a plastic film, roll-to-roll film coating may be used.

  Subsequently, the composition is held at a predetermined temperature at which the cholesteric liquid crystal structure is expressed, and the composition is oriented. Note that the cholesteric liquid crystal structure of the polarization selective reflection layer finally obtained in the present invention is not in a planar alignment state but structurally non-uniform and in a disordered alignment state. Processing is required. 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 substrate is not required, but an alignment process that forms a plurality of helical structure regions in the cholesteric liquid crystal structure is necessary. Because it becomes.

  The alignment treatment can be performed by maintaining the above composition at a predetermined temperature at which the cholesteric liquid crystal structure develops. As a result, the cholesteric liquid crystal exhibits a liquid crystal phase, and the liquid crystal molecules themselves are self-assembled to produce a liquid crystal. A helical structure is formed, in which molecular directors are continuously rotated in the layer thickness direction. The cholesteric liquid crystal structure developed in such a liquid crystal phase can fix the cholesteric liquid crystal by a method as described later.

  In addition, when the solvent is contained in the liquid crystalline composition apply | coated on the base material, 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.

  Next, the cholesteric liquid crystal structure that has been aligned in the above-described alignment treatment step is solidified in the liquid crystal phase in the polarization selective reflection layer, and the cholesteric liquid crystal structure that is expressed in the liquid crystal phase is fixed.

  Here, as a method used in the solidification 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 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 liquid crystal material exhibiting nematic regularity contained in the liquid crystal composition that is a material of the polarization selective reflection layer. In this method, the liquid crystal polymer is applied to the substrate in a state of being dissolved in a solvent such as an organic solvent. In this case, the solidification with cholesteric regularity can be achieved simply by removing the solvent by a drying process. The polarized light selective reflection 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 polarization selective reflection layer by thermally polymerizing liquid crystal molecules in the liquid crystalline composition by heating. In this method, the bonding state of the liquid crystal molecules changes depending on the heating (baking) temperature. Therefore, if there is temperature unevenness in the plane of the polarization selective reflection layer during heating, physical properties such as film hardness and optical characteristics will be 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 polarization selective reflection layer formed on the substrate 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 or between the hot plate. A method can be used in which a slight air layer is provided and held so as to be 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.

  The heating temperature generally requires a high temperature of 100 ° C. or higher, but is preferably about 150 ° C. due to the heat resistance of the substrate. However, if a film specialized in heat resistance is used as the material of the substrate, heating at a high temperature of 150 ° C. or higher is also possible.

  The method (3) is a method of curing the polarization selective reflection 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 as described above. 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.

  By performing the above-described series of steps (coating step, alignment step and solidification step), a projection screen having a single polarization selective reflection layer can be manufactured. By repeating, it is possible to manufacture a projection screen having a plurality of polarization selective reflection layers. Here, when a polarization selective reflection layer is further coated on the polarization selective reflection layer having light diffusivity, the orientation state of the lower layer is continued, so there is no need to provide a layer for controlling the orientation in between. However, you may form other layers, such as an easily bonding layer, for example.

3. Next, the base material used for the projection screen of the present invention will be described. The base material used for the projection screen of the present invention is not particularly limited as long as the above-mentioned polarization selective reflection layer can be formed. In the present invention, the light of the visible light wavelength is absorbed. It is preferable that it absorbs light within a range of 400 nm to 700 nm. This prevents reflection when circularly polarized light opposite to the circularly polarized light of the cholesteric liquid crystal or light having a wavelength other than a specific wavelength reflected by the polarization selective reflection layer is incident, and projection with high brightness is possible. This is because it can be a screen.

  As a base material that absorbs the wavelength in the visible light region, for example, as shown in FIG. 5A, a plastic film 50 in which a black pigment is kneaded can be used. Further, as shown in FIG. 5B, a light absorption layer 52 may be formed on a transparent plastic film 51 or the like, and this light absorption layer 52 is formed by the polarization selective reflection layer. It may be formed on the side to be formed, or may be formed on the opposite side as shown in FIG.

  In the present invention, as described above, since the cholesteric liquid crystal structure in the polarization selective reflection layer is structurally non-uniformly formed, the base material may be a material with little surface alignment. As a material with less surface orientation, for example, a plastic film that has not been stretched or a material that has not been rubbed can be used. Usually, the polarization selective reflection layer is formed on a plastic film or the like that has been subjected to stretching or rubbing treatment so that the regularity is good, but in the present invention, it is subjected to stretching or rubbing treatment or the like. By forming the polarization selective reflection layer on a non-base material, the liquid crystal on the base material surface is not regularly aligned, and the light projected from the projector is diffused by separating the polarized light. This is because the orientation of the structure can be disturbed.

  The material used for the substrate is not particularly limited, and examples thereof include a plastic film, metal, paper, and glass. Examples of the plastic film include polycarbonate polymers, polyester polymers such as polyarylate and polyethylene terephthalate, polyimide polymers, polysulfone polymers, polyethersulfone polymers, polystyrene polymers, polyethylene and polypropylene. A film made of a thermoplastic polymer such as a polyolefin polymer, a polyvinyl alcohol polymer, a cellulose acetate polymer, a polyvinyl chloride polymer, or a polymethyl methacrylate polymer can be used.

  Further, the film thickness of the base material used in the present invention is appropriately selected depending on the use and type of the projection screen. For example, when the projection screen is used in a roll-up manner, it is usually 15 μm to 300 μm. In particular, the thickness may be 25 μm to 100 μm. In addition, the film thickness of the base material is not particularly limited when the film is not used in a roll-up type and does not require flexibility such as a panel type.

  In addition, the base material used in the present invention may have a surface treated by, for example, corona treatment or UV cleaning in order to improve the adhesion with the polarization selective reflection layer.

  Furthermore, a plastic film or the like on which an easy-adhesion layer is formed may be used. For example, PET film A4100 with an easy-adhesion layer (trade name, manufactured by Toyobo Co., Ltd.) and easy-adhesion materials AC-X, AC-L, AC-W (Trade name, manufactured by Panac) may be used.

4). Projection Screen If the projection screen of the present invention has the polarization selective reflection layer on the base material and a hard coat layer is formed on the outermost surface on the projector side of such a projection screen, There is no particular limitation. For example, as shown in FIG. 6, the adhesion improving layer 4 is formed on the substrate 1, the polarization selective reflection layer 2 is formed on the adhesion improvement layer 4, and the polarization selective reflection layer 2 is further formed. In addition, the hard coat layer 3 may be formed. Further, as described above, the polarization selective reflection layer is not limited to one layer. For example, as shown in FIG. 6, a red polarization selective reflection layer (2R), a green polarization selective reflection layer (2G), It may be a blue polarized light selective reflection layer (2B) or the like, and may further be provided with layers of other colors. Further, as described above, the hard coat layer 3 may have only a hard coat function for protecting the surface of the projection screen, or in addition to the hard coat function, an antireflection function, an antiglare function, or an ultraviolet absorption function. It may be a case having other functions such as a function. Moreover, according to the aspect of the projection screen, for example, an antireflection layer, an antiglare layer, an ultraviolet absorption layer, or the like may be provided separately.

  According to the present invention, by providing the hard coat layer, for example, even when the surfaces are rubbed together and easily scratched, the scratches are not easily damaged, and the surface of the projection screen is protected. Therefore, it is possible to provide a projection screen having excellent scratch resistance. Furthermore, since the polarization selective reflection layer selectively reflects only light of a specific polarization component (for example, right-handed circularly polarized light) due to the polarization separation characteristic of the cholesteric liquid crystal structure, ambient light such as outside light or illumination light that does not have polarization characteristics. 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, 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.

  In addition, in the polarization selective reflection layer, the liquid crystal structure has structural non-uniformity so that the light projected from the projector is separated from the polarized light and diffused, and the spiral structure region included in the cholesteric liquid crystal structure Since the direction of the spiral axis L varies, the image light is diffusely reflected, not specularly reflected, and the image is easily visible. At this time, the polarization selective reflection layer diffuses selectively reflected light due to the structural non-uniformity of the cholesteric liquid crystal structure, so that light of a specific polarization component (for example, right circularly polarized light within the selective reflection wavelength region). ) While being diffused, other light (for example, left circularly polarized light within the selective reflection wavelength region, right circularly polarized light and left circularly polarized light outside the selective reflection wavelength region) can be transmitted without being diffused. For this reason, the above-mentioned “depolarization” problem does not occur with respect to ambient light and image light transmitted through the polarization selective reflection layer, and image visibility is maintained while maintaining the original polarization separation function of the polarization selective reflection layer. Can be improved.

  As described above, according to the present invention, 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 to increase the contrast of the image, while the structure included in the cholesteric liquid crystal structure. Due to the effect of the non-uniformity, a scattering effect can be given to the reflected light of the image light without reducing the visibility of the image, and the image can be displayed clearly even under bright ambient light.

  In the present invention, the adhesion improving layer is preferably formed, and this adhesion improving layer is provided in order to improve the adhesion between the substrate and the polarization selective reflection layer. There are no particular limitations on the type and material of such an adhesion improving layer, and for example, an acrylic or epoxy material can be used.

  In the present invention, the device that emits an image on the projection screen is not particularly limited as long as it can project an image on the projection screen with light shading. It may be like a projector that forms an image by disposing a film or the like. In the present invention, it is particularly preferable to use a light-emitting type projector such as a CRT system, a liquid crystal system, a DLP system, etc., and it is particularly preferable to polarize emitted light into circularly polarized light. For example, in the case of a liquid crystal projector, by passing through a phase difference plate that converts linearly polarized light to be converted into circularly polarized light, it is possible to convert it into circularly polarized light with almost no loss of light quantity. In this case, the retardation plate used preferably has a quarter wavelength, and specifically, it is preferable to use a plate having a wavelength of 137.5 nm in accordance with the highest visibility of 550 nm. Furthermore, since it is applied to all wavelengths of emitted RGB, it is particularly preferable that it is a broadband quarter wavelength phase difference plate. In addition, a single retardation plate by controlling the birefringence of the material, or a combination of a 1/4 wavelength retardation plate and a 1/2 wavelength retardation plate may be used. Here, the retardation plate may be incorporated in the projector, or may be externally attached to the injection port.

  In addition, since the CRT type and DLP type projectors are not controlled in polarization, it is preferable that the CRT type and DLP type projectors be linearly polarized via an optical element and a phase difference plate be disposed. In this case, the light quantity of the projector itself is halved, but it is possible to obtain a contrast improvement effect.

  Further, in the present invention, it is preferable that indoor illumination or outside light in which the projection screen is used be circularly polarized light opposite to the circularly polarized light reflected by the projection screen. As a result, even when external light, illumination, or the like is incident on the projection screen, the projection screen absorbs the light without reflecting the light, so that the brightness can be high even in a bright environment. It is. At this time, as a method for controlling the illumination and external light, an absorption type circularly polarizing plate, a reflective type circularly polarizing plate using a circularly polarized light separating layer, a linearly polarized light separating layer, or the like can be used.

5. Projection Screen Manufacturing Method Finally, the projection screen manufacturing method of the present invention will be described. In the projection screen manufacturing method of the present invention, after adjusting the above-described base material, a composition in which a material for forming a polarization selective reflection layer is mixed as described above is applied onto the base material, and is oriented and solidified. Applying the polarization selective reflection layer forming process to form the polarization selective reflection layer and the hard coat layer forming coating liquid for forming the hard coat layer on the outermost surface of the projection screen side of the projection screen to form the hard coat layer And a hard coat layer forming step. As a result, it is possible to manufacture a projection screen in which the polarization selective reflection layer is formed on the substrate and the hard coat layer is formed on the outermost surface of the projection screen on the projector side.

  In such a projection screen manufacturing method, the method of forming the polarization selective reflection layer formed in the polarization selective reflection layer step is the same as that described in “2. Polarization selective reflection layer” described above. Description is omitted. Hereinafter, the hard coat layer forming step will be described.

(Hard coat layer forming process)
In the hard coat layer forming step in the present invention, a hard coat layer is formed on the outermost surface on the projector side of the projection screen in a projection screen having a base material and a polarization selective reflection layer formed on the base material. In this step, a hard coat layer forming coating solution is applied to form a hard coat layer.

  The hard coat layer forming coating solution used in this step is not particularly limited as long as the material used for forming the hard coat layer described above is dissolved or dispersed in an appropriate solvent. In addition, since the hard coat layer in the present invention preferably has at least one of an antireflection function, an antiglare function and an ultraviolet absorption function as described above, in such a case, In addition to the material used for forming the hard coat layer, a coating liquid in which materials necessary for expressing each function are mixed can be used as the hard coat layer forming coating liquid in the present invention.

  It is possible to form a hard coat layer by applying such a coating liquid for forming a hard coat layer. As a coating method at this time, a generally used method can be used. Is possible. For example, it can be performed by 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. Moreover, when a base material is a plastic film, roll-to-roll film coating may be sufficient.

  In addition, since the thing regarding a hard-coat layer is the same as that of what was described in the item of "1. hard-coat layer" mentioned above, description here is abbreviate | omitted. Moreover, the projection screen which has these can be manufactured by forming an adhesive improvement layer, an antireflection layer, a glare-proof layer, an ultraviolet absorption layer, etc. as needed.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
[Example]
A monomer mixed liquid crystal in which a chiral agent was added to a main component composed of an ultraviolet curable nematic liquid crystal was dissolved in cyclohexanone, and 5% by weight of a photopolymerization initiator (manufactured by Ciba Geigy) was added. The cholesteric liquid crystal coating liquid 1 obtained above was applied to a 200 mm □ stretched black pet base material (manufactured by Panac Co., Ltd.) by bar coating. Thereafter, drying and alignment treatment were performed in an oven at 80 ° C. for 90 seconds to obtain a cholesteric liquid crystal film from which the solvent was removed. Next, ultraviolet light (50 mW / cm ² , 1 minute) was irradiated and cured to obtain a polarization selective reflection layer having a selective reflection band at 440 nm of the first layer. Next, the coating liquid 2 for the second layer was applied directly on the polarized light selective reflection layer in the same manner as for the first layer, followed by drying, orientation and curing treatment. The coating liquid 2 for the second layer was prepared in the same manner as the coating liquid 1, and a liquid crystal composition having a selective reflection center wavelength at 550 nm was obtained by adding the chiral agent. In the same manner as described above, a polarization selective reflection layer having a selective reflection center wavelength at 600 nm was laminated as the third layer. Thus, a projection screen 1 having a polarization selective reflection function including 440, 550, and 600 nm as selection wavelengths was obtained. The thickness of each layer was 3 μm for the first layer, 4 μm for the second layer, and 5 μm for the third layer.

  Thus, a screen having a diffusion cholesteric layer having a diffusion angle of ± 30 ° was obtained. The diffusion angle here refers to the measurement of the maximum reflection intensity (excluding interface reflection) when light is incident at an angle of 30 ° with respect to the normal direction of the screen plane and the backscattering at that time is measured. When the angle is 0 °, it means a measurement angle having a reflection intensity of 1/3 of the maximum reflection intensity.

Adeka optomer KRX-559-7 (Asahi Denka Kogyo Co., Ltd.) was directly applied by bar coating as a material for forming a hard coat layer on the prepared selective reflection layer, dried at 80 ° C. for 5 minutes, and then UV Was hardened by irradiation at 750 mJ / cm ² to form a hard coat layer having a thickness of 5 μm. Thereby, a projection screen on which a hard coat layer was laminated was obtained.

[Comparative example]
In the above example, a projection screen was produced in the same manner as in the above example except that the hard coat layer was not provided.

Table 1 below shows the results of the wear test in the examples and comparative examples.

It is explanatory drawing which shows an example of the projection screen of this invention. It is explanatory drawing for demonstrating the optical function of the polarization selective reflection layer in this invention. It is explanatory drawing for demonstrating the structural nonuniformity of the cholesteric liquid crystal structure which the polarization selective reflection layer in this invention has. It is a schematic sectional drawing which shows the other example of the projection screen of this invention. It is a schematic sectional drawing which shows the other example of the base material in this invention. It is a schematic sectional drawing which shows the other example of the projection screen of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Polarization selective reflection layer 3 ... Hard-coat layer 5 ... Projection screen 10 ... Projector

Claims (7)

A projection screen having a base material and a polarization selective reflection layer formed on the base material and having a cholesteric liquid crystal structure that selectively reflects light of a specific polarization component, and projects light emitted from a projector Because
The polarization selective reflection layer is formed in a disordered state in which the orientation of each liquid crystal phase is not aligned in a uniform direction so that projected light is diffused by separating polarized light,
A projection screen, characterized in that a hard coat layer is provided on an outermost surface of the projection screen on the projector side to prevent the surface of the projection screen from being damaged.   The polarization selective reflection layer has a thickness in the range of 1 μm to 10 μm, the spiral pitch of the cholesteric liquid crystal structure is 4 to 8 pitches, and the reflectance of the polarization component is 100%. The projection screen according to claim 1. The projection screen according to claim 1 , wherein the hard coat layer has a pencil hardness of 2H or more according to JIS K 5400. The projection screen according to any one of claims 1 to 3 , wherein the hard coat layer has an antireflection function for suppressing reflection of external light. The projection screen according to any one of claims 1 to 3 , wherein the hard coat layer has an anti-glare function for preventing glare of the projection screen. The wavelength range having a reflection intensity of the polarization selective reflection layer that is more than half of the maximum reflection intensity of the polarization selective reflection layer is only a part of the visible light range. The projection screen according to claim 5 . The polarization selective reflection layer emits light having a selective reflection center wavelength in a range of 430 to 460 nm, 540 to 570 nm, and 580 to 620 nm with reference to a case where light is incident perpendicularly to the polarization selective reflection layer. The projection screen according to claim 6 , wherein the projection screen selectively reflects.

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