JP2006221070A - Reflection type screen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type screen capable of reducing the sence of oppression in such a state as to be always installed not as a winding type but as a screen. <P>SOLUTION: The reflection type screen 10 provided with a selective reflection sheet (substrate 11, optical multilayer film 12) having a selective reflection characteristic is constituted as follows: a light diffusion layer 13 is made by holding a polymer dispersion liquid crystal layer A where fine particles of liquid crystal are dispersed and fixed in a polymer matrix between two sheets of transparent substrates having transparent conductive films (a) and is disposed on one side surface of the selective reflection sheet; and a light absorbing layer 14 is made by holding a polymer dispersion liquid crystal layer B where fine particles comprising liquid crystal and a dichroic black pigment are dispersed and fixed in a polymer matrix between two sheets of transparent substrates having transparent conductive films (b) and is disposed on the other side surface of the selective reflection sheet. Voltages are applied between the transparent conductive films (a) of the light diffusion layer 13, and between the transparent conductive films (b) of the light absorbing layer 14 respectively, and the respective polymer dispersion liquid crystal layers A, B are made into the light transmission state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reflective screen including a selective wavelength reflective optical multilayer film in which a projected image by projector light has high contrast even under bright light and has excellent color reproducibility.

  In recent years, overhead projectors and slide projectors have been widely used as methods for presenting materials by speakers in meetings and the like. In general households, video projectors and moving picture film projectors using liquid crystals are becoming popular. In these projector projection methods, light output from a light source is modulated by, for example, a transmissive liquid crystal panel to form image light, and the image light is emitted through an optical system such as a lens and projected on a screen. Is.

  For example, a front projector capable of forming a color image on a screen separates light rays emitted from a light source into light rays of red (R), green (G), and blue (B) colors and puts them in a predetermined optical path. An illumination optical system that converges, a liquid crystal panel (light valve) that optically modulates light beams of RGB colors separated by the illumination optical system, and a light combining unit that combines light beams of RGB colors light-modulated by the liquid crystal panel The color image synthesized by the light synthesis unit is enlarged and projected on the screen by the projection lens.

  Recently, a projector device has been developed that uses a narrow-band three-primary-color light source as a light source, and spatially modulates the luminous flux of each RGB color using a grating light valve (GLV) instead of a liquid crystal panel. Yes.

Further, in the projector as described above, a projection screen is used to obtain a projection image. The projection screen is roughly divided into a transmission type in which projection light is irradiated from the back surface of the screen and viewed from the screen surface. There is a reflection type that irradiates projection light from the front side of the screen and sees the reflection light of the projection light on the screen.
In any method, in order to realize a screen with good visibility, it is necessary to obtain a bright image and an image with high contrast.

  However, unlike a self-luminous display or a rear projector, a front projector cannot reduce the reflection of external light using, for example, an ND filter, and can increase the bright place contrast on a reflective screen. There was a problem that it was difficult.

  To solve this problem, the thickness of each optical film of the dielectric multilayer film is designed by simulation based on the matrix method, and has high reflection characteristics with respect to light in a specific wavelength region. A reflection type screen having an optical thin film (optical multilayer film) made of a dielectric multilayer film having high transmission characteristics for light in the visible wavelength range has been proposed (see, for example, Patent Document 1).

  Further, as shown in FIG. 1, it has a high reflection characteristic with respect to light in a specific wavelength region, which is formed by a wet method such as dipping, and is high in at least a visible wavelength region other than the specific wavelength region. A reflective screen including an optical multilayer film 12 composed of 2n + 1 (n is an integer of 1 or more) layers having transmission characteristics has been proposed (see, for example, Patent Document 2). In this screen, a sheet, a microlens array, a diffraction grating, or the like formed by dispersing or applying a diffusing material is used as the light diffusing layer 93. Further, the light absorption layer 94 is formed by applying black particles such as carbon.

  In the above screen, the optical multilayer film functions as a so-called wavelength band filter, and most of light in a specific wavelength region is reflected by the action of the optical multilayer film. For example, when outside light is incident, most of the region other than the specific wavelength region is transmitted through the optical thin film and hardly reflected.

  As described above, the reflection type screen can selectively reflect only light of a specific wavelength, and can suppress reflection of external light relative to a normal screen, and thus is formed on the screen. In addition, a decrease in contrast of the image is suppressed and reflection of external light is effectively reduced, so that a bright image can be obtained. Also, with this reflective screen, a clear image can be obtained even when the projection environment is bright, and a clear image can be obtained without being affected by the brightness of the projection environment. In particular, when the spectrum of a light source such as GLV is steep and the half-value width of the light source spectrum is narrower than the half-value width of the specific wavelength reflectance of the screen, extremely high contrast can be obtained and the ability of the light source side can be fully demonstrated. I can do it.

JP 2003-270725 A JP 2004-341407 A

  However, when the image is not displayed on the screen, the screen appears as a black screen, so the presence is large as it is, and it is particularly a factor that feels a sense of pressure when placed in a white walled room. It was.

  As a countermeasure, it is possible to use a screen winding method, but this time, new countermeasures such as a curl countermeasure are required. In addition, the winding method has a problem that it takes time to wind up / down, a feeling of luxury is lost, and an outlet is necessary at a high part near the ceiling, and the preference is divided.

  The present invention has been made in view of the above problems in the prior art, and an object thereof is to provide a reflective screen that can reduce the feeling of pressure in a state where it is always installed as a screen without using a winding method. And

  The present invention provided to solve the above-mentioned problems is a selective reflection sheet having high reflection characteristics with respect to light in a specific wavelength region and having high transmission characteristics with respect to at least a visible wavelength region other than the wavelength region. A polymer dispersed liquid crystal layer A in which liquid crystal microparticles are dispersed and fixed in a polymer matrix is sandwiched between two transparent substrates having a transparent conductive film a, and one surface of the selective reflection sheet Two sheets having a transparent conductive film b, a light diffusing layer disposed thereon, and a polymer dispersed liquid crystal layer B in which fine particles containing liquid crystal and a black dichroic dye are dispersed and fixed in a polymer matrix A reflective screen comprising a light absorption layer disposed on the other surface of the selective reflection sheet, between the transparent conductive film a of the light diffusion layer, and the light absorption layer. A voltage is applied between the transparent conductive films b. A reflective screen each polymer dispersed liquid crystal layer A, B is characterized by comprising a light transmitting state Te.

  Here, the light diffusing layer is applied with a voltage lower than a voltage at which the polymer-dispersed liquid crystal layer A is in a light transmission state between the transparent conductive films a or when no voltage is applied, the selective reflection sheet. It is preferable that the light reflected by is diffused and emitted.

  Moreover, it is preferable that the said light absorption layer absorbs the transmitted light of the said selective reflection sheet, when a voltage is not applied between the said transparent conductive films b.

  According to the present invention, when a reflective screen is not used, that is, when an image is not displayed on the screen, the light diffusing layer and the light absorbing layer are set in a transmissive state so that external light incident on the reflective screen is reflected. Since all the layers constituting the mold screen (light diffusion layer, optical multilayer film, light absorption layer) are transmitted, the screen is transparent in appearance, and the presence can be reduced even if it is arranged as it is. In addition, when displaying an image on the screen, the light diffusion layer is controlled to have a light diffusion function as in the past, and the light absorption layer is controlled to have a light absorption function as in the past. An image with excellent visibility and color reproducibility can be viewed.

The configuration of the reflective screen according to the present invention will be described below.
FIG. 2 is a cross-sectional view showing the configuration of the reflective screen according to the present invention.
As shown in FIG. 2, the reflective screen 10 has reflection characteristics with respect to light in the wavelength regions of light of each of the three primary colors of RGB among the wavelength regions of projector light on both surfaces of the substrate 11. And a light diffusing layer 13 disposed on one main surface of the selective reflection sheet (the outermost layer of the optical multilayer film 12). And a light absorption layer 14 disposed on the other main surface of the selective reflection sheet (a surface opposite to the surface on which the light diffusion layer 13 of the optical multilayer film 12 is disposed). The present invention is characterized by the light diffusion layer 13 and the light absorption layer 14.

  The substrate 11 may be transparent as long as it satisfies the desired optical characteristics such as a transparent film, a glass plate, an acrylic plate, a methacrylstyrene plate, a polycarbonate plate, and a lens. As optical characteristics, the material constituting the substrate 11 preferably has a refractive index of 1.3 to 1.7, a haze of 8% or less, and a transmittance of 80% or more. Further, the substrate 11 may have an antiglare function.

The transparent film is preferably a plastic film, and examples of the material forming the film include cellulose derivatives (eg, diacetylcellulose, triacetylcellulose (TAC), propionylcellulose, butyrylcellulose, acetylpropionylcellulose and nitrocellulose), polymethyl (Meth) acrylic resins such as methacrylates and copolymers of vinyl methacrylates such as methyl methacrylate and other alkyl (meth) acrylates, styrene, etc .; polycarbonate resins such as polycarbonate and diethylene glycol bisallyl carbonate (CR-39); (Brominated) bisphenol A type di (meth) acrylate homopolymer or copolymer, (brominated) bisphenol A mono (meth) acrylate Thermosetting (meth) acrylic resins such as polymers and copolymers of tan-modified monomers; polyesters, especially polyethylene terephthalate, polyethylene naphthalate and unsaturated polyesters; acrylonitrile-styrene copolymers, polyvinyl chloride, polyurethane, epoxy Resins are preferred. In addition, an aramid resin considering heat resistance can be used. In this case, the upper limit of the heating temperature is 200 ° C. or higher, and the temperature range is expected to be widened.
The plastic film can be obtained by a method such as stretching these resins, diluting them in a solvent, forming a film and drying them. The thickness is preferably thick from the viewpoint of rigidity, but is preferably thin from the haze side, and is usually about 25 to 500 μm.

  In addition, the surface of the plastic film may be coated with a coating material such as a hard coat, and the presence of this coating material in the lower layer of an optical multilayer film composed of an inorganic substance and an organic substance allows adhesion, hardness, Various physical properties such as chemical resistance, durability, and dyeability can also be improved.

  The optical multilayer film 12 is a film having selective reflection characteristics in which a high refractive index film 12H and a low refractive index film 12L having a lower refractive index than the high refractive index film 12H are alternately stacked.

  The high refractive index film 12H and the low refractive index film 12L can be formed by any of a dry process such as sputtering, or a wet process such as spin coating or dip coating.

In the case of forming by a dry process, various materials can be used as the constituent material of the high refractive index film 12H as long as the refractive index is about 2.0 to 2.6. Similarly, the constituent material of the low refractive index film 12L has a refractive index of about 1.3 to 1.5, and various materials can be used. For example, the high refractive index film 12H may be made of TiO ₂ , Nb ₂ O ₅ or Ta ₂ O ₅ , and the low refractive index film 12L may be made of SiO ₂ or MgF ₂ .

When formed by a dry process, the thickness of each optical multilayer film 12 is determined so that the optical thin film has high reflection characteristics with respect to light in a specific wavelength band by simulation based on a matrix method, and at least visible light other than the wavelength band light is visible. The film thickness may be designed so as to have high transmission characteristics for light in the wavelength band. The simulation based on the matrix method here is a method disclosed in Japanese Patent Application Laid-Open No. 2003-270725, and an angle θ is applied to a multilayer optical thin film system that is composed of a plurality of different materials and causes multiple reflection at the boundary of each layer. _When light is incident at ₀ , the phase is aligned depending on the type and wavelength of the light source to be used and the optical film thickness (product of refractive index and geometric film thickness) of each layer, and the reflected light velocity shows coherence. A simulation is performed using an equation based on a principle that causes cases to interfere with each other, and a film thickness of an optical film having desired characteristics is designed.

  In the present invention, as the specific wavelength region, the wavelength region of each of the RGB three primary colors used as image light by the projector light source is selected, and only light in these wavelength regions is reflected by a simulation based on the matrix method. The film thickness may be designed so as to transmit light in a wavelength region other than these wavelength regions. By superposing the high-refractive index film 12H and the low-refractive index film 12L having such thicknesses, the optical multilayer film 12 that functions well as a three primary color wavelength band filter can be reliably realized.

  Further, the number of layers of the optical film constituting the optical multilayer film 12 formed by the dry process is not particularly limited and can be set to a desired number of layers. It is preferable that the outer layer is composed of an odd number of layers (per one surface of the substrate 11) which is the high refractive index film 12H.

  When the optical multilayer film 12 is formed by a wet process, a high refractive index film 12H obtained by applying and curing a solvent-based paint for a high refractive index film, and an optical having a lower refractive index than the high refractive index film 12H. It is preferable to use an odd-numbered layer in which low-refractive index films 12L obtained by applying and curing a low-refractive index film solvent-based paint to be a film are alternately laminated. Each optical film may be formed by applying a paint containing a resin that absorbs energy applied by heating, ultraviolet irradiation, or the like and causes a curing reaction. For example, the high refractive index film 12H is formed of a thermosetting resin JSR Opster (JN7102, refractive index 1.68), and the low refractive index film 12L is a thermosetting resin JSR Opster (JN7215, refractive index 1.41). ). Thereby, the optical multilayer film 12 has flexibility.

  Here, the high refractive index film 12H is not limited to the thermosetting resin, but is a solvent-based paint capable of ensuring a refractive index of about 1.6 to 2.1, such as the high light diffusion film. Any optical film material having a refractive index may be used. The low refractive index film 13L is not limited to the thermosetting resin, but a solvent-based paint capable of ensuring a refractive index of about 1.3 to 1.59, such as the low light diffusion film shown above. Any optical film material having a refractive index may be used. Note that the larger the difference in refractive index between the high refractive index film 12H and the low refractive index film 12L, the smaller the number of layers.

  When formed by a wet process, each film thickness of the optical multilayer film 12 is, for example, highly reflective with, for example, a reflectance of 50% or more with respect to light in the three primary color wavelength regions including light in the wavelength regions of red, green, and blue. In addition to having the characteristics, it is designed to have a high transmission characteristic of, for example, a transmittance of 80% or more with respect to light in a wavelength band other than the three primary color wavelength band lights.

Here, each film thickness of the optical multilayer film 12 is such that the thickness of each film is d, the refractive index of each film is n, and the wavelength of light incident on the optical multilayer film is λ. The target thickness nd is preferably designed so as to satisfy the following expression (1) with respect to the wavelength λ of the incident light.
nd = λ (α ± 1/4) (1)
(However, α is a natural number.)

  For example, the film thickness of the high refractive index film 12H (refractive index 1.68) is 1023 nm, the film thickness of the low refractive index film 12L (refractive index 1.41) is 780 nm, the high refractive index film 12H, and the low refractive index film 12L. Nine layers are alternately stacked, and the optical multilayer film 12 having a 19-layer structure in which the high refractive index film 12H is stacked on the stacked layers is used as a projector light (from a projector light source using the laser oscillator described above). The light has a high reflectance of 80% or more for the light of the three primary colors, and has a high transmittance of 20% or less for the wavelength light (stray light) before and after the three primary wavelengths. It can be set as the film | membrane which has.

  The light diffusion layer 13 is formed by sandwiching a polymer-dispersed liquid crystal layer A in which fine particles of liquid crystal are dispersed and fixed in a polymer matrix between two transparent substrates having a transparent conductive film A.

As shown in FIG. 3, the light diffusion layer 13 includes a polymer-dispersed liquid crystal layer 131 in which liquid crystal microparticles 131 _LC are dispersed and fixed in a polymer matrix 131 _m , and the polymer-dispersed liquid crystal layer 131. It is composed of two transparent substrates 132 having a transparent conductive film 132e sandwiched therebetween, and a voltage is applied from the power source E to the transparent conductive film 132e.

The polymer-dispersed liquid crystal layer 131 is made of a so-called polymer-dispersed liquid crystal material (PDLC (Polymer Dispersed Liquid Crystal)), and uses a solution containing the polymer material and liquid crystal to encapsulate, polymerize phase separation, and thermal phase. The liquid crystal microparticles 131 _LC are dispersed and fixed in a matrix 131 _m made of a polymer material by a separation method, a solvent evaporation phase separation method, or the like.

The material constituting the polymer matrix 131 _m is not particularly limited as long as it is transparent polymer substantially coincident with the refractive index corresponding to ordinary ray of the liquid crystal in which the refractive index constitutes a microparticle 131 _LC It is preferable. In view of suitability as such an optical material, an acrylic resin is preferable.

The shape of the liquid crystal microparticle 131 _LC is not particularly limited, such as a spherical shape, a droplet shape, or a rugby ball shape. The material (liquid crystal) constituting the fine particles 131 _LC in is not limited particularly as long as it can be used in the polymer dispersed liquid crystal material (PDLC). For example, a commonly used liquid crystal material such as nematic liquid crystal or cholesteric liquid crystal may be used. At this time, it is preferable to control Δn (index of refractive index anisotropy) by adjusting the substituent of the liquid crystal and the synthesis method so that the diffusion characteristics and transmission characteristics suitable for the light diffusion layer 13 can be obtained. The structural formulas of liquid crystal compounds that can be used in the present invention are exemplified below.

  When the thickness of the polymer-dispersed liquid crystal layer 131 is increased, the diffusibility is improved, the transparency is deteriorated and the imaging effect is increased, but the response of the liquid crystal alignment is deteriorated, and the necessary applied voltage is increased. Such disadvantages also come out. It is preferable to be within a thickness range of 5 to 50 μm.

  The transparent substrate 132 is obtained by forming a transparent conductive film 132e on a transparent base substrate 132b. The base substrate 132b may be a transparent polymer film or glass, and the transparent conductive film 132e may be a thin film of indium tin oxide (ITO), for example.

FIG. 4 is a schematic diagram showing the state of the polymer-dispersed liquid crystal layer 131 depending on whether or not a voltage is applied from the power source E to the transparent conductive film 132e.
When no voltage is applied from the power source E to the transparent conductive film 132e (OFF state, FIG. 4A), the binding force of the wall (polymer matrix 131 _m ) that is in contact with the liquid crystal LC constituting the microparticle 131 _LC is small. It works dominantly, and the liquid crystal is randomly oriented and diffuses or reflects part of the incident light.

When voltage is applied from the power source E to the transparent conductive film 132e (ON state, FIG. 4B), when the applied voltage is sufficiently large, the dielectric anisotropy of the liquid crystal LC constituting the microparticle 131 _LC is The liquid crystal is aligned in a direction perpendicular to the electric field generated between the two transparent conductive films 132e. As a result, the polymer-dispersed liquid crystal layer 131 transmits light of all wavelengths of incident light.

In the present invention, the alignment state of the liquid crystal LC constituting the microparticle 131 _LC is set to the OFF state (FIG. 4 (a)) and the ON state (FIG. 4) depending on whether an image is displayed on the reflective screen 10 or not. (B)) is used properly to change the diffusion characteristics and transmission characteristics of the light diffusion layer 13.

As shown in FIG. 5, the light absorbing layer 14 is a polymer-dispersed liquid crystal layer 141 in which fine particles 141 _LCp containing a liquid crystal LC and a black dichroic dye p are dispersed and fixed in a polymer matrix 141 _m. And two transparent substrates 142 having a transparent conductive film 142e sandwiching the polymer dispersed liquid crystal layer 141, and a voltage is applied from the power source E to the transparent conductive film 142e.

Here, the configurations of the polymer matrix 141 _m and the liquid crystal LC may be the same as those of the polymer matrix 131 _m and the liquid crystal LC constituting the light diffusion layer 13, respectively.

  The dichroic dye p is a black dye obtained by mixing dyes having absorption edges of the three primary colors RGB. Examples of dichroic dyes that can be used are shown in the table below.

In order to optimize the absorption characteristics and transmission characteristics of the light absorption layer 14 as a reflection type screen, the type of the polymer material constituting the polymer matrix 141 _m , the type of the dichroic dye p, the content in the liquid crystal LC, etc. It is good to adjust. Further, if the thickness of the polymer-dispersed liquid crystal layer 141 is increased, light absorption to the dichroic dye p is improved, and an effect that black is well sinked as a screen is obtained. Problems such as deterioration and a necessary applied voltage increase occur. Therefore, it is preferable to be within a thickness range of 10 to 20 μm.

FIG. 6 is a schematic diagram showing a state of the polymer dispersed liquid crystal layer 141 depending on whether or not a voltage is applied from the power source E to the transparent conductive film 142e.
When no AC voltage is applied from the power source E to the transparent conductive film 142e (OFF state, FIG. _6A ), the liquid crystal LC constituting the microparticle 141 _LCp is randomly oriented as in FIG. 4A. Accordingly, the dichroic dye p is similarly randomly oriented. As a result, the incident light is absorbed.

When an AC voltage is applied from the power source E to the transparent conductive film 142e (ON state, FIG. 6B), the liquid crystal LC constituting the microparticle 141 _LCp has two transparent conductive _films as in FIG. 4B. The dichroic dye p is similarly oriented in the same direction as the electric field generated between the films 142e. As a result, the polymer-dispersed liquid crystal layer 141 is in a state of transmitting light of all wavelengths of incident light.

In the present invention, the alignment state of the liquid crystal LC constituting the microparticle 141 _LCp is _set to the OFF state (FIG. _6A ) and the ON state (FIG. 6) depending on whether an image is displayed on the reflective screen 10 or not. (B)) is used properly to change the absorption characteristics and transmission characteristics of the light absorption layer 14.

The function and effect of the reflective screen of the present invention will be described with reference to FIG.
FIG. 7A shows a state when the reflective screen 10 is not used, that is, when an image is not displayed on the screen 10. Here, a voltage is applied between the transparent conductive film 132e of the light diffusion layer 13 and between the transparent conductive film 142e of the light absorption layer 14, and the light diffusion layer 13 and the light absorption layer 14 are respectively shown in FIG. As shown in FIG. 6B, light is transmitted. Therefore, the external light Lo incident on the reflection type screen 10 is transmitted through all the layers constituting the reflection type screen 10 (light diffusion layer 13, optical multilayer film 12, substrate 11, light absorption layer 14). It looks transparent on the screen. Therefore, even if this reflective screen 10 is arranged as it is, the presence can be reduced.

  On the other hand, FIG. 7B shows a state when the reflective screen 10 is used, that is, when an image is displayed on the screen 10. Here, no voltage is applied between the transparent conductive film 132e of the light diffusing layer 13 and between the transparent conductive film 142e of the light absorbing layer 14, and the light diffusing layer 13 is light-transmitted as shown in FIG. The light absorption layer 14 is in a state of absorbing light as shown in FIG. Therefore, the light incident on the reflective screen 10 passes through the light diffusion layer 13 and reaches the optical multilayer film 12, and the external light component Lo included in the incident light is transmitted through the optical multilayer film 12 to absorb light. Only light in a specific wavelength region (three primary color wavelength regions) corresponding to the light Lp absorbed by the layer 14 and projected from the projector light source is selectively reflected. Then, the reflected light is diffused on the surface of the light diffusion layer 13 and provided to the viewer as image light having a wide viewing angle. Therefore, it is possible to eliminate the influence of external light on the image light that is the reflected light at a high level, and it is possible to display a high-contrast image with uniform color expression that has not existed in the past.

  In FIG. 7B, by applying a voltage lower than the voltage at which the polymer dispersed liquid crystal layer 131 is in a transmissive state between the transparent conductive films 132e of the light diffusion layer 13, the diffusion characteristics of the light diffusion layer 13 are improved. You may make it adjust.

  Further, the reflective screen according to the present invention may have a configuration in which the optical multilayer film 12 having the same configuration as described above is formed on one side of the substrate 11 and the light absorption layer 14 is formed on the back side of the substrate 11.

Next, a method for manufacturing the reflective screen 10 according to the present invention will be described below.
First, an example in which the optical multilayer film 12 constituting the reflective screen 10 is formed by a coating method will be described.
(S11) A polyethylene terephthalate (PET) film is prepared as the substrate 11, and a predetermined amount of the optical film material A for high refractive index is applied to both surfaces of the substrate 11 by dipping. Here, the coating amount of the optical film material A is set to an amount that becomes the target film thickness of the high refractive index film 12H.
(S12) The coating film of the optical film material A is dried and then cured by irradiating with ultraviolet rays to form a high refractive index film 12H having a predetermined thickness.
(S13) Next, a predetermined amount of the low refractive index optical film material B is applied onto the high refractive index film 12H by dipping. Here, the coating amount of the optical film material B is set to an amount that becomes the target film thickness of the low refractive index film 12L.
(S14) The coating film is dried and then thermally cured to form a low refractive index film 12L having a predetermined thickness. Thereby, it becomes a laminated structure of the high refractive index film | membrane 12H and the low refractive index film | membrane 12L.
(S15) Next, the processing of steps s11 to s12 is performed on the low refractive index film 12L on the outermost layer of the substrate 11 to form the high refractive index film 12H, and the substrate 11 and the optical multilayer film 12 (12H / 12L / 12H). Is completed.

  The coating method of the optical film materials A and B is not limited to dipping coating, but may be applied by a conventionally known coating method such as gravure coating, roll coating, blade coating, die coating, cap coater.

Next, the light diffusion layer 13 may be manufactured as follows, for example. Here, an example by the polymerization phase separation method is shown.
(S21) A liquid crystal (nematic liquid crystal, for example, p-alkyle-p′-alkoxyazoxybenzene) is dissolved with a raw material (polymerizable monomer or oligomer) of the polymer matrix 131 _m to prepare a solution. Specifically, the raw material of the polymer matrix 131 _m and the liquid crystal are put into a container at a predetermined volume ratio, and are stirred and melted using a stirrer until uniform.

The starting material of a polymer matrix 131 _m, the solubility in the liquid crystal, it is important to have a durability, for example, a monomer of the ultraviolet curable type which occur crosslinking polymerization reaction by ultraviolet irradiation is preferred.
In addition, the mixing volume ratio of resin and liquid crystal is 50:50 as a standard, but in the mixing of resin and liquid crystal, the diffusibility increases as the mixing ratio of liquid crystal increases, and the permeability tends to deteriorate. The mixing ratio may be set based on the image performance.

(S22) The solution is applied to the transparent substrate 132 on which the transparent conductive film 132e is formed with a uniform thickness by a doctor blade method or the like.
(S23) The other transparent substrate 132 is placed on the coating film so that the transparent conductive film 132e is in contact with the coating film, and the two transparent substrates are sandwiched by the spacers through the spacer. Note that the thickness of the polymer dispersed liquid crystal layer 131 may be adjusted by the spacer.
(S24) The ultraviolet curable monomer is photopolymerized by irradiating ultraviolet rays from either one of the transparent substrates 132. Irradiation with ultraviolet rays is preferably performed under the condition that the photopolymerization is necessary and sufficient, for example, 15 mW / cm ² and about 60 seconds. Thereby, the polymer dispersed liquid crystal layer 131 in which the microparticles 131 _LC of the liquid crystal LC are dispersed and fixed in the polymer matrix 131 _m is formed.
(S25) An electrode for applying a voltage from the power source E is attached to the transparent conductive film 132e of the transparent substrate 132 to complete the light diffusion layer 13.

Next, the light absorption layer 14 may be manufactured, for example, as follows. Here, an example by the polymerization phase separation method is shown.
(S31) A liquid crystal in which a black dichroic dye is dissolved in advance with a raw material (polymerizable monomer or oligomer) of the polymer matrix 141 _m is dissolved to prepare a solution. Specifically, the raw material of the polymer matrix 141 _m and the liquid crystal are put into a container at a predetermined volume ratio, and are stirred and melted using a stirrer until uniform. Although the amount of the dichroic dye dissolved in the liquid crystal varies depending on the type of the liquid crystal, the effect of light absorption (FIG. 6 (a)) is increased when the dichroic dye is dissolved in a large amount.

(S32) The solution is applied to the transparent substrate 142 on which the transparent conductive film 142e is formed with a uniform thickness by a doctor blade method or the like.
(S33) The other transparent substrate 142 is placed on the coating film so that the transparent conductive film 142e is in contact with the coating film, and the two transparent substrates sandwich the coating film via the spacer. Note that the thickness of the polymer dispersed liquid crystal layer 141 may be adjusted by the spacer.
(S34) The ultraviolet curable monomer is photopolymerized by irradiating ultraviolet rays from either one of the transparent substrates 142. As a result, the polymer dispersed liquid crystal layer 141 in which the fine particles 141 _LCp containing the liquid crystal LC and the black dichroic dye p are dispersed and fixed in the polymer matrix 141 _m is formed.
(S35) An electrode for applying a voltage from the power source E is attached to the transparent conductive film 142e of the transparent substrate 142 to complete the light absorption layer 14.

  Finally, the light diffusion layer 13 is attached to one main surface (the outermost layer surface of the optical multilayer film 12) of the selective reflection sheet produced as described above via an adhesive layer or an adhesive layer, and the other of the selective reflection sheet The light absorbing layer 14 is attached to the main surface (the surface opposite to the surface where the light diffusing layer 13 is attached) of the optical multilayer film 12 via an adhesive layer or an adhesive layer, thereby completing the reflective screen 10.

The transparent substrate 132 in step S22 or S23 of the manufacturing process of the light diffusion layer 13 may be made of the optical multilayer film 12 and a transparent conductive film formed on the optical multilayer film 12. Further, the transparent substrate 142 in step S32 or S33 of the manufacturing process of the light absorption layer 14 may be made of the optical multilayer film 12 and a transparent conductive film formed on the optical multilayer film 12.
With this manufacturing method, the base substrate in the transparent substrate 132 and / or the transparent substrate 142 can be omitted, so that the loss of light due to the optical interface can be reduced.

Examples of the present invention will be described below.
(1) Sample preparation conditions (a) Selective reflection sheet Composition of coating material (I) as optical film material A, coating material (II) as optical film material B, and method for producing optical multilayer film using these coating materials Is shown below.
(I) Optical film material A (paint (I))
Fine particles: TiO ₂ fine particles (Ishihara Sangyo Co., Ltd., average particle diameter of about 20 nm, refractive index 2.48) 100 parts by weight Dispersant: SO ₃ Na group-containing molecule (weight average molecular weight: 1000, SO ₃ Na group concentration: 2 × 10 ⁻³ mol / g)
20 parts by weight-Binder: Mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (Nippon Kayaku UV curable resin, trade name DPHA) 30 parts by weight-Organic solvent: methyl isobutyl ketone (MIBK) 4800 Part by weight First, a predetermined amount of fine particles, a dispersant, and an organic solvent were mixed and dispersed with a paint shaker to obtain a TiO ₂ fine particle dispersion. Next, a binder was added to the dispersion, and the mixture was stirred with a stirrer to obtain paint (I).
(Ii) Optical film material B (paint (II))
・ Polyfluorobutenyl vinyl ether polymer with terminal carboxyl group (product name: Cytop, manufactured by Asahi Glass Co., Ltd.)

(Iii) Manufacturing method of optical multilayer film (S41) The coating material (I) is applied to both surfaces of the transparent support by the dipping method.
(S42) The coating film of paint (I) is dried at 80 ° C. and then cured by ultraviolet (UV) (1000 mJ / cm ² ) to form an optical film 12H having a film thickness of 850 nm and a refractive index of 1.94 per side.
(S43) Next, paint (II) is applied on the optical film 12H by dipping.
(S44) The coating film of paint (II) is dried at 90 ° C. to form an optical film 12L having a thickness of 1020 nm and a refractive index of 1.34.
(S45) The coating material (I) is applied on the optical film 12L under the same conditions as in step S41.
(S46) A coating film of paint (I) is formed under the same conditions as in step S42 to form an optical film 12H having a film thickness of 850 nm and a refractive index of 1.94 per side. As a result, a selective reflection sheet having a total of six optical multilayer films of three layers of optical film 12H / optical film 12L / optical film 12H per side on a transparent support was obtained. The selective reflection characteristic of this selective reflection sheet is shown in FIG.

(B) Light diffusion layer 13
The light diffusion layer 13 was produced under the following conditions.
(S51) A solution was prepared by changing the following materials to a polymer raw material: liquid crystal in a weight ratio of 10:90 to 30:70 and making them compatible.
-Polymer raw material (monomer); Nippon Kayaku HX-620 (Caprolacton-modhified hydroxyl pivalic acid ester neopentyglycol diacrylate)
Polymerization initiator: Merck Darocure 1173 (2-hydroxy-2-methyl-1-phenylpropan-1-one)
・ Liquid crystal (nematic liquid crystal); pyridine derivatives of the following structural formula

(S52) The solution was applied to the transparent substrate 132 on which the transparent conductive film 132e was formed with a uniform thickness by a doctor blade method.
(S53) The other transparent substrate 132 is placed on the coating film so that the transparent conductive film 132e is in contact with the coating film, and the two transparent substrates 132 sandwich the coating film via a spacer. In addition, the space | interval of the transparent substrate 132 was 11 micrometers by the spacer.
(S54) The ultraviolet curable monomer was photopolymerized by irradiating ultraviolet rays of 100 mW / cm ² or less from the outside of one transparent substrate 132. As a result, the polymer dispersed liquid crystal layer 131 in which the liquid crystal microparticles 131 _LC are dispersed and fixed in the polymer matrix 131 _m is formed.
(S55) The light diffusion layer 13 is completed by attaching an electrode for applying a voltage from the power source E to the transparent conductive film 132e of the transparent substrate 132.

(C) Light absorption layer 14
In the manufacturing process of the light diffusion layer 13, in step S51, a black pigment obtained by mixing the following red, blue, and blue-green merocyanine dichroic pigments in advance is dissolved in liquid crystal, and then a polymer raw material The light absorption layer 14 was produced by dissolving in the material and thereafter producing it under the same conditions as the production process of the light diffusion layer 13.

  As described above, the light diffusing layer 13 is attached to one main surface (the outermost layer surface of the optical multilayer film 12) of the selective reflection sheet produced in the present example via the optical adhesive layer, and the other main surface of the selective reflection sheet. The light absorbing layer 14 was attached to the surface (the surface opposite to the surface to which the light diffusing layer 13 was attached) of the optical multilayer film 12 via the optical adhesive layer to complete the reflective screen 10.

(2) Sample evaluation (a) Light diffusion layer 13
With respect to the obtained light diffusion layer 13, a light scattering state when light is incident from the front of the light diffusion layer 13 in each case of voltage application between the transparent conductive films (incident light intensity is 1) The light intensity measured for each positional relationship between the incident light and the light diffusion layer 13) was measured using an original scatterometer combined with an integrating sphere. The polymer dispersed liquid crystal layer 131 has a thickness of 11 μm and a birefringence of 0.220. Further, voltage application was performed using the drive circuit shown in FIG. The results are shown below.
(I) When voltage is applied (transmission state)
-Forward scattering: 0.06
・ Backscattering: 0.02
-Total scattered light: 0.08
・ Linear transmitted light: 0.82
-Regular reflection light: 0.09
(Ii) When no voltage is applied (cloudy state)
-Forward scattering: 0.54
・ Backscattering: 0.10
-Total scattered light: 0.64
・ Linear transmitted light: <0.001
-Regular reflection light: 0.05

(B) Light absorption layer 14
About the obtained light absorption layer 14, the light scattering state was measured on the same conditions as the said light-diffusion layer 13. FIG. The results are shown below.
(I) When voltage is applied (transmission state)
-Forward scattering: 0.05
-Backscattering: 0.01
-Total scattered light: 0.07
・ Linear transmitted light: 0.80
-Regular reflection light: 0.08
(Ii) When no voltage is applied (black state)
-Forward scattering: 0.04
-Backscattering: 0.04
-Total scattered light: 0.08
・ Linear transmitted light: <0.001
-Regular reflection light: <0.02

(C) Reflective screen 10
About the obtained reflective screen 10, when the reflective screen 10 was visually observed from the front in the state where the voltage of the condition shown in FIG. 9 was applied between the transparent conductive films of the light diffusion layer 13 and the light absorbing layer 14, The reflective screen 10 was in a transparent state, and the state behind it was seen through.
Further, when image light is projected from the projector onto the reflective screen 10 under bright light without applying a voltage between the transparent conductive films of the light diffusion layer 13 and the light absorption layer 14, a clear image with high contrast is observed. It was.

It is sectional drawing which shows the structure of the conventional reflective screen. It is sectional drawing which shows the structure of the reflection type screen which concerns on this invention. It is sectional drawing which shows the structure of the light-diffusion layer of this invention. It is sectional drawing which shows the operation state of the light-diffusion layer of this invention. It is sectional drawing which shows the structure of the light absorption layer of this invention. It is sectional drawing which shows the operation state of the light absorption layer of this invention. It is sectional drawing which shows the operation state of the reflection type screen which concerns on this invention. It is a figure which shows the selective reflection characteristic of a selective reflection sheet. It is a figure which shows the drive circuit example of the light-diffusion layer of this invention, and a light absorption layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,90 ... Reflective type screen, 11 ... Substrate, 12 ... Optical multilayer film, 12H ... High refractive index film, 12L ... Low refractive index film, 13, 93 ... Light diffusion layer, 14, 94 ... Light absorption layer, 131, 141 ... polymer dispersed liquid crystal layer, 131 _LC , 141 _LCp ... liquid crystal microparticles, 131 _m , 141 _m ... polymer matrix, 132, 142 ... transparent substrates, 132b, 142b ... Base substrate, 132e, 142e ... transparent conductive film, E ... power source, LC ... liquid crystal, p ... dichroic dye

Claims (3)

A selective reflection sheet having high reflection characteristics for light in a specific wavelength region, and having high transmission characteristics for at least a visible wavelength region other than the wavelength region;
A polymer-dispersed liquid crystal layer A in which fine particles of liquid crystal are dispersed and fixed in a polymer matrix is sandwiched between two transparent substrates having a transparent conductive film a, on one surface of the selective reflection sheet A light diffusing layer disposed on,
A polymer dispersed liquid crystal layer B in which fine particles containing liquid crystal and black dichroic dye are dispersed and fixed in a polymer matrix is sandwiched between two transparent substrates having a transparent conductive film b, A reflective screen comprising a light absorbing layer disposed on the other surface of the selective reflection sheet,
A reflection type wherein a voltage is applied between the transparent conductive film a of the light diffusing layer and the transparent conductive film b of the light absorbing layer, and the polymer dispersed liquid crystal layers A and B are in a light transmission state. screen.   In the light diffusion layer, a voltage lower than a voltage at which the polymer dispersed liquid crystal layer A is in a light transmission state is applied between the transparent conductive films a, or the selective reflection sheet is reflected when no voltage is applied. The reflective screen according to claim 1, wherein the light is diffused and emitted. The reflective screen according to claim 1, wherein the light absorbing layer absorbs light transmitted through the selective reflection sheet when no voltage is applied between the transparent conductive films b.

Images