CN100489653C - Screen and its manufacturing method - Google Patents

Abstract

A screen with high contrast and high gain, and a method of manufacturing the same, which is advantageous for mass production. The optical multilayer structure of the screen is composed of a transparent substrate (11) and first optical films (12H) and second optical films (12L) alternately appearing on each side of the transparent substrate, wherein the first The optical film (12H) has a high refractive index, the second optical film (12L) has a lower refractive index than the first optical film (12H), and the outermost layer is the first optical film (12H). The number of optical films of the multilayer structure is 2n+1 (n is an integer of 1 or more). Each optical film has high reflective properties for light in a specific wavelength range and high transmissive properties for light other than the specific wavelength range (at least light in the visible wavelength range).

Description

Screen and its preparation method

technical field

The invention relates to a screen and a preparation method thereof.

Background technique

In recent years, overhead projectors and slide projectors have been widely used as means for presenting materials by conference speakers and the like. Also, home video projectors and moving picture movie projectors using liquid crystals are gaining popularity. The projection method adopted in these projectors is to modulate light emitted from a light source by a light valve to form image light, and transmit the image light on a screen through an optical system such as a lens.

Projectors of this type include projectors that allow the display of color images, using lamps that emit white light (including the three primary colors of red (R), green (G), and blue (B)) as a light source, and employing a transmissive liquid crystal panel as a light valve. In such a projector, white light emitted from a light source is decomposed into light rays of red light, green light, and blue light by an illuminating optical system, and the light rays are converged on predetermined light paths. These luminous fluxes are spatially modulated by the liquid crystal panel according to the image signal, and the modulated luminous fluxes are mixed by the light mixing part to form a colored image light, and the mixed color image light is amplified by means of a projection lens and projected on the screen on the screen so that the viewer can see the image on the screen.

In addition, as a projector capable of displaying color images, a narrow-band three-primary-color light source is recently developed as a light source (such as a laser oscillator emitting narrow-band light for each of the three primary colors of RGB) and a grating light valve (hereinafter referred to as "GLV") is used. Devices that act as light valves. In this type of projector, the luminous flux of each color light emitted by the laser oscillator is spatially modulated by the GLV according to the image signal, and the modulated luminous flux is mixed by the light mixing part, thereby forming a larger than any conventional projector. Color image Sharper color image light. The colored image light is magnified by the projection lens and transmitted on the screen so that the viewer can see the image on the screen.

For example, as a screen used in such a projector, there is a screen that reflects image light emitted by the projector (front projector) in front of the screen so that an observer can see an image projected on the screen by observing the reflected light, And there have been provided such screens, for example, a structure in which a reflective layer, a light absorbing layer, and a scattering layer having predetermined viewing angle characteristics are sequentially formed on a substrate while having improved contrast performance (see Patent Document 1, for example).

Patent Document 1: Specification of Japanese Patent No. 3103802 (paragraphs 0017 and 0018, FIG. 1 )

However, in the above-mentioned screen, the reflective layer made of aluminum foil reflects not only image light but also ambient light, and thus improvement in contrast performance is not satisfactory. In addition, the light-absorbing layer on the side closer to the surface than the reflective layer absorbs not only ambient light but also image light reflected by the reflective layer, causing a problem in that the white light level of images on the screen decreases.

In view of the above-mentioned problems accompanying the conventional technology, the task of the present invention is to provide a screen with high contrast and high gain and a method of manufacturing the same, which is advantageous for mass production.

Contents of the invention

In order to solve the above-mentioned problems, the same applicant as the present applicant has proposed a screen that mainly reflects image light emitted from a projector without reflecting light from Light other than a projector, such as light originating from fluorescent lighting, the sun, etc., that is, ambient light (for example, Japanese Patent Application No. 2002-070799). This screen has a selective reflection layer formed on a substrate, a scattering layer formed on the front side of the selective reflection layer for scattering reflected light, and an absorption layer formed on the rear side of the selective reflection layer for absorbing transmitted light . The selective reflection layer is an optical multilayer film including high-refractive-index optical films and low-refractive-index optical films stacked alternately with each other, and has such a property that it reflects light in the wavelength range of projector light, such as the three primary colors of red (R ), green (G), blue (B) wavelength ranges of light, and transmits other light wavelength ranges other than the three primary colors. In such a screen, the adverse effects of ambient light can be significantly suppressed, so that even in a brightly lit room, the black level can be reduced without reducing the screen gain, so that a high-contrast image can be presented on the screen. Sharp image.

However, the high-refractive-index layer and the low-refractive-index layer must be formed by a dry method such as sputtering, and the size of the vacuum processing chamber in the deposition machine is limited, so the size of the substrate that can be placed in the processing chamber is limited, making it difficult Increase the size of the screen. In addition, the use of dry processes limits mass production.

Furthermore, in order to obtain an optical film with high reflectivity, it is necessary to increase the number of laminated layers constituting the optical film, thereby inevitably increasing the number of steps for forming the optical film, resulting in a decrease in the product yield of the screen.

The present inventors have noticed the fact that the dry method causes the above-mentioned problems, and conducted extensive and intensive research. As a result, they completed the invention of a screen and its preparation method, which is not only advantageous in that it can be increased in size and has characteristics favorable for mass production, but also that it can achieve high contrast and high gain as well as high reflectivity.

Specifically, the screen of the invention of claim 1 for solving the above-mentioned problems is characterized in that it includes an optical multilayer film on a substrate, the optical multilayer film consisting of (2n+1) layers (where n is 1 or more large integer), each layer has high reflectivity for light in a specific wavelength range, and at least has high transmittance for visible light outside the specific wavelength range; wherein the optical multilayer film is formed by a coating method.

According to the invention of claim 1, an optical multilayer film can be formed on a substrate larger in size than that used in the dry process, thereby enabling realization of a large-sized screen with high contrast and high gain.

The screen of the invention of claim 2 for solving the above-mentioned problems is the screen according to the invention of claim 1, characterized in that the base is transparent, and the optical multilayer film is formed on both surfaces of the base by a coating method. .

According to the invention of claim 2, the total number of laminated layers constituting the optical multilayer film in the screen is twice that of the conventional screen having the optical multilayer film on only one surface, even when the laminated layers of the optical multilayer film constituting each surface The number of layers is the same as a conventional screen, so high reflectivity can be achieved.

Formation of the optical thin film on both surfaces of the substrate can be carried out by immersing the substrate in a predetermined coating composition. In this case, it is preferable that the transparent substrate has a refractive index of 1.30 to 1.69.

The screen of the invention of claim 3 for solving the above-mentioned problems is the screen according to the invention of claim 1, characterized in that the optical multilayer film has a stacked structure including a first optical film having a high refractive index and a refractive A second optical film having a lower rate than the first optical film, wherein the first optical film and the second optical film are stacked on top of each other, and the outermost layer of the optical multilayer film is composed of the first optical film.

The screen of the invention of claim 4 for solving the above-mentioned problems is the screen according to the invention of claim 3, characterized in that the first optical film is a film containing metal oxide fine particles, a dispersant, and a binder, and the The second optical film is a film containing fluorine-containing resin or _SiO2 fine particles.

The screen of the invention of claim 5 for solving the above problems is the screen according to the invention of claim 4, characterized in that the metal oxide fine particles are _TiO2 or _ZrO2 fine particles.

According to the inventions of claims 3 to 5, the optical multilayer film is composed of an odd number of layers so that the outermost layers on the light incident side and the opposite side of the projector are all composed of the first optical film having a high refractive index, thus Has a good selective reflective layer function. In addition, the thicknesses of the first optical film and the second optical film can be selected arbitrarily, so that the formed optical multilayer film has the property of reflecting light in the desired wavelength range and transmitting other light outside the wavelength range, thereby realizing A screen with high contrast and high gain and high reflectivity consistent with the light source of a projector.

The screen of the invention of claim 6 for solving the above-mentioned problems is the screen according to the invention of claim 3, characterized in that the specific wavelength range includes wavelength ranges of red, green, and blue light.

According to the invention of claim 6, a screen from which a good image with high contrast to RGB light sources can be seen can be obtained.

Specifically, in the invention of claim 3, when the refractive index of the first optical film is adjusted to 1.70 to 2.10, the refractive index of the second optical film is adjusted to 1.30 to 1.69, and the first optical film and the second optical film When the thicknesses of the films are all adjusted to 80 nm to 15 μm, an optical multilayer film having properties of reflecting projector light in the wavelength range of RGB three primary colors and transmitting other light outside the wavelength range of the three primary colors can be obtained.

The screen of the invention of claim 7 for solving the above problems is the screen according to the invention of claim 1, characterized by having a light absorbing layer to absorb light passing through the optical multilayer film.

According to the invention of claim 7, light passing through the optical multilayer film is absorbed, so that an excellent image with higher contrast can be seen on the screen.

A black film may be laminated at a predetermined position as a light absorbing layer.

The screen of the invention of claim 8 for solving the above-mentioned problems is the screen according to the invention of claim 1, characterized by having a light scattering layer on the outermost layer of the optical multilayer film to scatter light reflected by the optical multilayer film.

According to the invention of claim 8, the light selectively reflected by the optical multilayer film is scattered while passing through and leaving the light scattering layer, so the observer can see a natural image by observing the scattered reflected light.

The method of manufacturing a screen of the invention of claim 9 for solving the above-mentioned problems is a method of manufacturing a screen comprising an optical multilayer film consisting of (2n+1) layers (where n is 1 or Larger integers), each layer has high reflectivity to light in a specific wavelength range, and at least has high transmittance to visible light outside the specific wavelength range; wherein the method for preparing the optical multilayer film is characterized in that it comprises a first a coating step to form a first optical film having a high refractive index by a coating method; and a second coating step to form a second optical film having a lower refractive index than the first optical film by a coating method, and the The first coating step and said second coating step are carried out alternately.

According to the invention of claim 9, an optical multilayer film can be more easily formed on a substrate having a larger size than that used in the dry process, so that large-sized screens with high contrast and high gain can be produced in large batches.

Preferably, the first coating step and the second coating step are carried out alternately for a predetermined number of cycles, and the final step of the method is the first coating step. Thus, the optical multilayer film is composed of (2n+1) layers, so that the outermost layers on the light-incident side and the opposite side of the projector are composed of optical films with high refractive index, thus having a good selective reflection layer function.

The method of manufacturing a screen of the invention of claim 10 for solving the above-mentioned problems is a method of manufacturing a screen comprising an optical multilayer film each composed of (2n+1) layers on both surfaces of a transparent substrate (wherein n is an integer of 1 or more), each layer has high reflectivity to light in a specific wavelength range, and at least has high transmittance to visible light outside the specific wavelength range; wherein the preparation of the optical multilayer film The method is characterized in comprising a first coating step to form a first optical film having a high refractive index on both surfaces of a substrate to be coated by a dip coating method; and a second coating step to form a first optical film having a high refractive index by a dip coating method A second optical film having a lower refractive index than the first optical film is formed on both surfaces of the substrate to be coated; and the first coating step and the second coating step are alternately performed.

According to the invention of claim 10, an optical multilayer film composed of a required number of stacked layers can be produced while reducing the number of steps for forming an optical film, so a large-sized film with high contrast and high gain and high reflectance can be improved. The product yield of the screen makes it possible to prepare the screen in large batches.

The method of manufacturing a screen of the invention of claim 11 for solving the above-mentioned problems is a method according to the invention of claim 10, characterized by including the step of forming a light absorbing layer on the outermost layer of one of said optical multilayer films, to Light transmitted through the optical multilayer film is absorbed.

The method of manufacturing a screen of the invention of claim 12 for solving the above-mentioned problems is a method according to the invention of claim 11, characterized in the step of forming a light-scattering layer on the outermost layer of another optical multilayer film so as to be scattered by the The light emitted by the optical multilayer film.

According to the invention of claim 12, a light scattering layer is formed which scatters light selectively reflected by the optical multilayer film and allows it to pass through, so that it is possible to prepare a natural image on which an observer can see by observing the scattered reflected light screen.

According to the invention of claim 11, forming a light absorbing layer which absorbs light transmitted through the optical multilayer film makes it possible to prepare a screen on which an excellent image with higher contrast can be seen.

Description of drawings

FIG. 1 is a cross-sectional view of a screen structure according to one embodiment of the present invention.

Fig. 2 is a cross-sectional view of a screen structure according to another embodiment of the present invention.

Detailed ways

Hereinafter, embodiments of the screen of the present invention will be explained. The following embodiments are merely examples, and should not be considered as limiting the scope of the present invention.

An example of the structure of the screen of the present invention is shown in FIG. 1 . The screen 10 has a structure in which an optical multilayer film 12 , a light absorbing layer 13 and a light scattering layer 14 are formed on a base 11 .

The substrate 11 can be made of any material that is transparent and satisfies required optical properties, such as a transparent film, a glass plate, an acrylic resin plate, a methacrylic styrene resin plate, a polycarbonate plate, a lens, and the like. The optical properties of the material constituting the substrate 11 are preferably such that the refractive index is 1.3 to 1.7, the haze is 8% or less, and the light transmittance is 80% or more. The substrate 11 may have an anti-glare function.

The transparent film is preferably a plastic film, and as examples of materials constituting the film, cellulose derivatives such as diacetyl cellulose, triacetyl cellulose (TAC), propionyl cellulose, butyryl cellulose, acetyl cellulose, etc. propionyl cellulose and nitrocellulose); (meth)acrylic resins such as polymethyl methacrylate, and methyl methacrylate with other vinyl monomers such as alkyl (meth)acrylates or benzene Copolymers of ethylene; polycarbonate resins such as polycarbonate and diethylene glycol diallyl carbonate (CR-39); thermosetting (meth)acrylic resins such as (brominated) bisphenol A bis(methyl ) homopolymers or copolymers of acrylates, and polymers or copolymers of (brominated) bisphenol A mono(meth)acrylate urethane-modified monomers; polyesters, especially polyethylene terephthalate Diesters, polyethylene naphthalate, and unsaturated polyesters; acrylonitrile-styrene copolymers; polyvinyl chloride; polyurethanes; and epoxy resins. In addition, aramid resin having heat resistance can also be used. In this case, the upper limit of the heating temperature is 200° C. or higher, and therefore, a wider temperature range of the film is desired.

The plastic film can be obtained by a method in which the above-mentioned resin is stretched or diluted with a solvent and formed into a film, followed by drying. From the viewpoint of obtaining rigidity, the thickness of the film is preferably large, and from the viewpoint of suppressing turbidity, the thickness of the film is preferably small, and is usually about 25 to 500 μm.

The surface of the plastic film can be covered with a coating material such as a hard coat layer, and the coating material composed of inorganic materials and organic materials formed under the optical multilayer film improves various properties such as adhesion, hardness, chemical resistance , durability and dyeability.

Alternatively, an optically functional film or primary layer may be formed on the substrate 11 as a surface treatment for the transparent substrate. Examples of the base layer include metal organoalkoxides, polyesters, acrylic-modified polyesters, and polyurethanes. In addition, it is preferable that the substrate is subjected to corona discharge treatment or UV irradiation treatment.

The basic feature of the present invention resides in an optical multilayer film 12 comprising an optical film 12H having a high refractive index by coating a material A for the following optical film on a substrate as a first optical film, obtained by curing it; and an optical film 12L having a low refractive index, which is obtained by coating material B for the following optical film as a second optical film and curing it, wherein the optical film 12H and optical films 12L are stacked alternately with each other. Specifically, the optical multilayer film 12 has a structure in which an optical film 12H having a high refractive index is first formed on a substrate, and then an optical film 12L having a low refractive index is formed thereon, and then the optical film 12H and the optical film 12H are alternately formed. film 12L, and finally form the optical film 12H, in other words, the optical multilayer film 12 is a stacked film composed of (2n+1) layers (where n is an integer of 1 or more).

The optical film 12H is an optical film obtained by coating the material A for an optical film on the substrate 11 or the optical film 12L, and then performing a curing reaction of the material. The optical film 12H contains fine particles for controlling the refractive index.

The optical film 12H preferably has a thickness of 80 nm to 15 μm, more preferably 600 to 1000 nm. When the thickness of the optical film 12H is greater than 15 μm, the amount of haze components composed of undispersed fine particles increases, making it difficult to realize a suitable optical film function.

The optical film 12H preferably has a refractive index of 1.70 to 2.10. When the refractive index of the optical film 12H is higher than 2.10, the scattering performance of the fine particles is not satisfactory, so that the function of the optical film deteriorates. On the other hand, if the optical film 12H has a refractive index lower than 1.70, the reflection performance achieved after stacking the optical film 12L on the optical film 12H is unsatisfactory, so that the resulting screen disadvantageously has unsatisfactory performance.

The optical film 12L is an optical film having a refractive index of 1.30 to 1.69, which is formed by coating the material B for an optical film on the optical film 12H, and then performing a curing reaction of the material. The refractive index of the optical film 12L depends on the type of resin contained in the optical film material B, and optionally the type and amount of contained fine particles. When the refractive index of the optical film 12L is higher than 1.69, the difference in refractive index between the optical film 12L and the optical film 12H cannot be guaranteed, and therefore, the reflective performance realized after stacking the optical film 12L on the optical film 12H is not satisfactory, so that The resulting screens disadvantageously have unsatisfactory properties. In addition, it is difficult to form a thin film with a refractive index lower than 1.3, so 1.3 is the lower limit of the refractive index from the viewpoint of production.

The optical film 12L preferably has a thickness of 80 nm to 15 μm, more preferably 600 to 1000 nm.

Due to the above structure, the optical multilayer film 12 has high reflectivity for light in three wavelength ranges, ie, red, green, and blue wavelength ranges, and has high transmittance for at least visible light outside the three wavelength ranges. By changing the respective refractive indices or thicknesses of the optical films 12H, 12L, the wavelengths in the three wavelength ranges to be reflected by the optical multilayer film 12 can be changed or controlled so that the optical multilayer film 12 can properly process the light emitted by the projector wavelength.

There is no particular limitation on the number of layers of the optical films 12H, 12L constituting the optical multilayer film 12, and the optical films 12H, 12L may have a desired number of layers. It is preferable that the optical multilayer film 12 is composed of an odd number of layers so that the outermost layers on the projector light incident side and the opposite side are both composed of the optical film 12H. For the wavelength ranges of the three primary colors, an optical multilayer film 12 composed of odd-numbered layers has a more favorable color filter function than an optical multilayer film composed of even-numbered layers.

Specifically, it is preferable that the optical multilayer film 12 is composed of odd-numbered layers of 3 to 7 layers. When the number of layers is two or less, the optical multilayer film 12 cannot satisfactorily function as a reflective layer. On the other hand, the larger the number of layers constituting the optical multilayer film, the higher the reflectivity of the optical multilayer film, but when the number of layers is eight or more, the increase rate of the reflectivity is small, and the expected pass through cannot be achieved. The effect of increasing the number of times of forming the optical multilayer film 12 to increase the reflectance.

The light absorbing layer 13 absorbs light passing through the optical multilayer film 12 , for example, FIG. 1 shows an embodiment in which a black film is stacked on the outermost surface of the optical multilayer film 12 .

Alternatively, the light absorbing layer 13 may be a coating obtained by coating a black coating composition.

Examples of black coating compositions include fine particles such as carbon black fine particles and carbon black-coated silicon oxide fine particles. These fine particles can be electrically conductive.

As a method for producing carbon black fine particles, an oil furnace method, a tunnel method, a lamp method and a thermal method are known methods.

When the fine particles are used to deepen the blackness, the primary particle size and scattering properties of the fine particles are important factors in determining the blackness of the film, and the fine particles with a smaller primary particle size and a larger surface area also increase the jet-blackness (jet-blackness). ). Carbon black with a large number of surface functional groups has a high affinity for carriers such as alkyd resins with polar functional groups (such as OH groups or carboxyl groups), and when used with low-polarity hydrocarbon solvents, carbon black increases the affinity for The wettability of the resin, thereby improving the gloss and jetness of the resulting film. In addition, it is preferable to add a curing agent having an isocyanate group or a carboxyl group reactive to the functional group in the above-mentioned resin to the fine particles to cure the film.

Generally, the number of surface functional groups in tunnel carbon is greater than that in furnace carbon, but the number of functional groups in carbon prepared according to the furnace method can be increased by oxidizing it. Preferably the carbon black has a primary particle size of 30 nm or less, more preferably 20 nm or less. When carbon black having a larger particle size is used, the blackness of the resulting film decreases, degrading the performance of the film as a light absorbing layer.

The coating method may be a known method such as curtain coating, knife coating or spray coating.

The light absorbing layer 13 preferably has a thickness of about 10 to 50 μm, more preferably 15 to 25 μm. If the thickness of the light-absorbing layer is less than 10 μm, the blackness is disadvantageously reduced, especially when a spray coating method is used. On the other hand, if its thickness is greater than 50 μm, the resulting film is so brittle that cracks can form in the film.

The light-scattering layer 14 has an uneven surface, and there is no particular limitation on the constituent material of the light-scattering layer as long as it transmits light in the wavelength range used in projectors, glass or plastic commonly used in the scattering layer can be used. For example, a clear epoxy can be applied to the optical multilayer film 12 and embossed to form an uneven surface, or a diffuser film having an uneven surface can be laminated to the optical multilayer film. The light selectively reflected by the optical multilayer film 12 is scattered as it passes through and out of the light scattering layer 14, so that a viewer can see a natural image by observing the scattered reflected light. The scattering angle of the light scattering layer 14 is an important factor determining visibility, and the scattering angle can be increased by controlling the refractive index of the material constituting the scattering sheet or the shape of the uneven surface.

When the light source of the projector is laser light, it is preferable that the surface shape pattern of the light scattering layer 14 is random in order to prevent a speckle pattern which is a kind of scattering on the screen.

The screen 10 can be selectively reflective so that light of a specific wavelength from the projector is reflected, while other light incident on the screen (such as ambient light) having a wavelength range outside the specific wavelength range is transmitted and absorbed, reducing the The black level of the image on the screen 10 achieves high contrast, so that an image with high contrast appears on the screen even in a brightly lit room. For example, when light from an RGB light source such as a grating projector using a grating light valve (GLV) is projected on the screen 10, good images with high contrast without adverse effects of ambient light can be observed at large viewing angles.

Specifically, the incident light on the screen 10 passes through the light scattering layer 14 and reaches the optical multilayer film 12, the optical multilayer film 12 transmits the ambient light component contained in the incident light, and the ambient light component is absorbed by the light absorbing layer 13, Only light of a specific wavelength range responsible for an image is selectively reflected, and the reflected light is scattered by the surface of the light-scattering layer 14, and transmitted to the observer as image light at a large viewing angle. Therefore, the adverse influence of ambient light on image light, which is reflected light, can be removed at a high level, so that a higher contrast ratio than conventional screens can be obtained.

The screen of the present invention may have the structure shown in FIG. 2, which includes an optical multilayer film formed on the front side of the substrate and having the same structure as that described above, a light scattering layer formed on the surface of the outermost layer of the optical multilayer film, and A light absorbing layer formed on the rear side of the substrate. The screen reflects light of a specific wavelength from the projector, and transmits and absorbs other incident light in a wavelength range different from the specific wavelength (such as ambient light) to reduce the black level (black level) on the screen, thereby achieving high contrast.

Materials A and B for the optical film, which are coating compositions for forming the first optical film and the second optical film, will be described below.

(1) Material A for optical film

Material A for an optical film contains fine particles, an organic solvent, a binder absorbing energy for curing reaction, and a dispersant including lipophilic groups and hydrophilic groups.

The fine particles are fine particles composed of high refractive index materials added to control the refractive index of the formed optical film, examples of which include Ti, Zr, Al, Ce, Sn, La, In, Y, Sb, etc. oxides, and alloy oxides such as In-Sn. Even if the Ti oxide contains an appropriate amount of oxides of Al, Zr, etc. that inhibit photocatalysis, the effects of the present invention are not impaired.

The fine particles preferably have a specific surface area of 55 to 85 m ² /g, more preferably 75 to 85 m ² /g. When the specific surface area of the fine particles falls within this range, the dispersion treatment of the fine particles causes the fine particles to have a particle size of 100 nm or less in the optical film material, whereby an optical film with very little haze can be obtained.

As examples of organic solvents, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone; alcohol solvents such as methanol, ethanol, propanol, butanol or isobutanol; or ester solvents such as Methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, or ethylene glycol acetate. These organic solvents do not have to be as high as 100% pure, and they may contain impurities such as isomers, unreacted substances, decomposition products, oxides or moisture in amounts of 20% or less. In order to apply the composition to a substrate or an optical film having low surface energy, a solvent having a lower surface tension is preferable, and examples of such a solvent include methyl isobutyl ketone, methanol, ethanol, and the like.

Examples of the binder include thermosetting resins, ultraviolet (UV) curable resins, and electron beam (EB) curable resins. Examples of thermosetting resins, UV curable resins and EB curable resins include polystyrene resins, styrene copolymers, polycarbonates, phenolic resins, epoxy resins, polyester resins, polyurethane resins, urea resins, melamine resins, polyamine resins , and urea-formaldehyde resin. A polymer having another cyclic (aromatic, heterocyclic or alicyclic) group may be used. Alternatively, resins having fluorine or silanol groups in their carbon chains may be used.

The method of carrying out the curing reaction of the resin may be any method of radiation or heating, however, when the curing reaction of the resin is carried out by ultraviolet radiation, it is preferable that the reaction is carried out in the presence of a polymerization initiator. Examples of radical polymerization initiators include azo-based initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile); and peroxide Bioinitiators such as benzoyl peroxide, lauroyl peroxide, and t-butyl peroctoate. The initiator is used in an amount of 0.2 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, relative to a total of 100 parts by weight of the polymerizable monomer.

Dispersants include lipophilic groups and hydrophilic groups, which improve the dispersibility of fine particles. The weight average molecular weight of the lipophilic group in the dispersant is 110-3000. When the molecular weight of the lipophilic group is lower than 110, there arises a problem that the dispersant cannot be satisfactorily dissolved in an organic solvent, and when the molecular weight is larger than 3000, satisfactory fine particle dispersibility in an optical film cannot be obtained. The dispersant may have a functional group that undergoes a curing reaction with the binder.

As the hydrophilic group contained in the dispersant, the amount of the polar functional group is 10 ^-3 to 10 ^-1 mol/g. When the amount of the functional group is less than or greater than this range, there is no effect on the dispersion of fine particles, resulting in reduced dispersibility. The functional groups given below are effective polar functional groups as they do not lead to any aggregation state. Examples thereof include -SO ₃ M, -OSO ₃ M, -COOM, P=O(OM) ₂ (wherein M represents a hydrogen atom or an alkali metal such as lithium, potassium or sodium), a tertiary amine, and a quaternary ammonium salt R ₁ (R ₂ )(R ₃ )NHX (in the formula, R ₁ , R ₂ and R ₃ each represent a hydrogen atom or a hydrocarbon group, and X- represents a halogen such as chlorine, bromine or iodine ion or an inorganic or organic ion). In addition, examples thereof include polar functional groups such as -OH, -SH, -CN and epoxy groups. These dispersants can be used alone or in combination. In the film used in the present invention, the total amount of the dispersant is 20-60 parts by weight, preferably 38-55 parts by weight, based on 100 parts by weight of fine particles.

The material A for optical film is coated into a film, and then the curing reaction of the film is promoted by radiation or heating to form a first optical film of high refractive index type.

(2) Material B for optical film

Material B for the optical film contains an organic solvent and a binder. The binder is dissolved in an organic solvent, and when necessary, fine particles may be added and dispersed in the solution of the binder.

The binder is a resin with functional groups in the molecule, which undergoes a curing reaction by radiation such as ultraviolet rays or heat energy, and is preferably a fluororesin or the like.

The fine particles are fine particles composed of a low-refractive index material optionally added to control the refractive index of the formed optical film, examples of which include SiO ₂ , MgF ₂ , hollow fine particles, and fine particles composed of fluororesins. Oxides of Ti, Zr, Al, Ce, Sn, La, In, Y, Sb, etc., or alloy oxides of In—Sn, etc., may be added. Even if Ti oxide contains an appropriate amount of oxides of Al, Zr, etc. for suppressing photocatalysis, the effect of the present invention is not impaired.

As examples of organic solvents, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, propanol, butanol, and isobutanol; ester solvents, Such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate and ethylene glycol acetate; and fluorinated solvents, such as fluorinated aromatic hydrocarbons, such as perfluorobenzene, pentafluorobenzene, 1,3- Bis(trifluoromethyl)benzene and 1,4-bis(trifluoromethyl)benzene, fluorinated alkylamines, such as perfluorotributylamine and perfluorotripropylamine, fluorinated aliphatic hydrocarbons, such as perfluorotripropylamine Fluorohexane, perfluorooctane, perfluorodecane, perfluorododecane, perfluoro-2,7-dimethyloctane, 1,3-dichloro-1,1,2,2,3- Pentafluoropropane, 1H-1,1-dichloroperfluoropropane, 1H-1,3-dichloroperfluoropropane, 1H-perfluorobutane, 2H,3H-perfluoropentane, 3H,4H-perfluoropropane -2-methylpentane, 2H, 3H-perfluoro-2-methylpentane, perfluoro-1,2-dimethylhexane, perfluoro-1,3-dimethylhexane, 1H- Perfluorohexane, 1H, 1H, 1H, 2H, 2H-perfluorohexane, 1H, 1H, 1H, 2H, 2H-perfluorooctane, 1H-perfluorooctane, 1H-perfluorodecane and 1H , 1H, 1H, 2H, 2H-perfluorodecane, fluorine-containing alicyclic hydrocarbons, such as perfluorodecalin, perfluorocyclohexane and perfluoro-1,3,5-trimethylcyclohexane, and Fluoroethers such as perfluoro-2-butyltetrahydrofuran and fluorine-containing low molecular weight polyethers. For example, using methyl isobutyl ketone as the organic solvent used in material A of the optical film, using a mixed solvent (95:5) of fluorine-containing alcohol (C ₆ F ₁₃ C ₂ H ₄ OH) and perfluorobutylamine Organic solvent used in material B as optical film. These organic solvents do not have to be as high as 100% pure, and they may contain impurities such as isomers, unreacted substances, decomposition products, oxides or moisture in amounts of 20% or less.

The material B of the optical film is coated into a film and then subjected to a curing reaction to form a second optical film having a lower refractive index than the first optical film.

The production methods of Materials A and B for optical films include a kneading step and a dispersion step, and optionally a mixing step before or after the above steps. Any raw materials used in the present invention, including fine particles, resins and solvents, may be added at the beginning of each step or during each step. Each raw material may be divided into two or more parts, and may be added separately in two or more steps. The dispersion and kneading can be performed using known equipment such as a stirrer or a paint shaker.

The method of manufacturing the reflective screen 10 of the present invention will be explained below.

(s1) prepare a polyethylene terephthalate (PET) film as the base 11, and apply material A for an optical film to both surfaces of the base 11 in a predetermined amount by a dip coating method, In the dip coating method, the substrate 11 is dipped in a container containing the material A for an optical film, and then taken out therefrom.

(s2) The thin films of the material A for optical films are dried to form optical films 12H each having a predetermined thickness.

(s3) Then, the material B for an optical film is coated in a predetermined amount on the optical film 12H positioned on both sides of the substrate 11 by a dip coating method in which the optical film is formed thereon. The substrate 11 of 12H was dipped in a container containing the material B for optical film, and then taken out therefrom.

(s4) The material B for the optical film is dried to form the optical film 12L each having a predetermined thickness, thereby forming a stacked structure including the optical film 12H and the optical film 12L.

(s5) Then, the material A for an optical film is coated in a predetermined amount on each of the optical films 12L constituting the outermost layers on both sides of the substrate 11 by the method in which the The substrates 11 of the optical films 12H and 12L were dipped in the container containing the material A for the optical film, and then taken out therefrom.

(s6) The film of material A for optical film is dried and then irradiated with ultraviolet rays to cure material A for optical film to form optical films 12H each having a predetermined thickness. Next, the processing cycle in steps s3 to s6 is repeated a predetermined number of times to form the optical multilayer film 12 on both sides of the substrate 11 .

(s7) A low-refractive-index transparent adhesive (EPOTEK 396 manufactured and sold by Epoxy Technology Inc.) is coated on the optical multilayer film 12 located on the front side, and a plate-shaped light-scattering layer 14 is placed on on the coated adhesive so that the surface of the light scattering layer 14 on the opposite side of the uneven surface is in contact with the adhesive, and then the adhesive is cured to serve as an adhesive for bonding the optical multilayer film 12 and the light scattering layer 14. layer.

(s8) A resin containing a black light absorber is coated on the optical multilayer film 12 on the rear side to form the light absorbing layer 13, thereby obtaining the reflective screen 10 of the present invention.

In the given example, the materials A and B for the optical film were coated by dip coating, however, both the materials A and B for the optical film can be coated by a known coating method such as gravure coating. Cloth, roller, knife or die coating methods for coating.

In addition, the screen according to another embodiment of the present invention may have the structure shown in FIG. 2, which includes an optical multilayer film 12 having the same structure as that formed on the front side of the substrate 11 described above; a light-scattering layer 14 formed on the surface of the outermost layer of the optical multilayer film 12; and a light-absorbing layer 13 formed on the rear side of the substrate. The screen 20 reflects light of a specific wavelength from the projector, and transmits and absorbs incident light of a wavelength range different from the specific wavelength (eg, ambient light) to reduce the black level on the screen and thereby achieve high contrast.

(Example)

Hereinafter, examples for carrying out the present invention will be described. The following examples are merely examples and should not be construed as limiting the scope of the present invention.

(Example 1)

The formulation and preparation method of the coating composition (I) corresponding to the optical film material A and the coating composition (II) corresponding to the optical film material B, and the method of preparing the screen in Example 1 will be described below. The "parts by weight" used below refers to the weight ratio of each component added, relative to the total weight constituting the coating composition.

(1) Coating composition (I)

Fine particle: _TiO2 fine particle

(Manufactured and sold by Ishihara Sangyo Co., Ltd.; average particle size: about 20nm; refractive index: 2.48)

100 parts by weight (2% by weight)

Dispersant: silane coupling agent

(A-174; manufactured and sold by Nippon Unicar Co., Ltd.)

20 parts by weight (0.4% by weight)

Organic solvent: methyl ethyl ketone

4800 parts by weight (97.6% by weight)

First, fine particles, a dispersant, and an organic solvent are mixed together in predetermined amounts and dispersed by means of a paint shaker to obtain a fine particle dispersion. To this fine particle dispersion was added 33 parts by weight (equivalent to 33% by weight based on the weight of _TiO2 ) of dipentaerythritol hexaacrylate which is a UV curable resin as a binder with respect to ₁₀₀ parts by weight of TiO2 fine particles. A mixture of ester and dipentaerythritol pentaacrylate (trade name: DPHA; manufactured and sold by Nippon Kayaku Co., Ltd.), and 3 parts by weight relative to the binder (equivalent to 3% by weight, based on UV-curable resin (dipentaerythritol hexaacrylate) ester and the mixture of dipentaerythritol pentaacrylate)) Darocure 1173 as a polymerization initiator, and stirred by means of a stirrer to prepare a coating composition (I). The coating composition had a viscosity of 2.3 cps and a specific gravity of 0.9 g/cm ³ .

(2) Coating composition (II)

The final formulation of the coating composition (II) for the low refractive index film is as follows.

Binder: Vinyl fluoride copolymer resin

(Tetrafluoroethylene copolymer; manufactured and sold by DAIKIN INDUSTRIES Co., Ltd.; solvent: butyl acetate; solid content: 50% by weight; refractive index: 1.42)

20 parts by weight (16.7% by weight)

Organic solvent: methyl isobutyl ketone

100 parts by weight (83.3% by weight)

The coating composition had a viscosity of 4.0 cps and a specific gravity of 0.84 g/cm ³ .

(3) Method of forming optical thin film

(s11) The coating composition (I) was coated on both surfaces of a transparent PET film (thickness: 188 μm; trade name: U426; manufactured and sold by Toray Industries Inc.) by a dip coating method. The conditions of dip coating are as follows:

Dipping speed: 400mm/min

Retention time: 1 minute

Take out speed: 350mm/min

(s12) Drying the film of the coating composition (I) at room temperature to form a high-refractive-index optical film having a thickness of 780 nm per surface.

(s13) Next, the coating composition (II) is coated on the high-refractive-index optical film by a dip coating method. The conditions of dip coating are as follows:

Dipping speed: 400mm/min

Retention time: 1 minute

Take out speed: 160mm/min

(s14) Dry the films of the coating composition (II) at room temperature to form low-refractive-index optical films each having a thickness of 1120 nm.

(s15) Coating the coating composition (I) on the optical film (II) under the same conditions as step s11.

(s16) Dry the film of the coating composition (I) at room temperature, and then perform ultraviolet (UV) curing (500mJ/cm ² ) to form a high-refractive-index optical film with a thickness of 780nm on each surface, thereby forming a film on the PET film Optical multilayer films each consisting of three layers (ie, optical film (I)/optical film (II)/optical film (I)) were obtained.

In the evaluation of the formed optical film, the respective refractive indexes of the optical film (I) and the optical film (II) were measured by Filmetrics (manufactured and sold by Matsushita Inter-techno Co., Ltd.). In addition, the haze of the optical multilayer film was also measured by a haze meter (JASCOV-560 type). In addition, the reflection performance of the optical multilayer film was also measured using Filmetrics (manufactured and sold by Matsushita Inter-techno Co., Ltd.). In terms of reflective performance, reflectance was measured separately for each wavelength of the three primary colors (ie, blue wavelength: 480 nm, green wavelength: 560 nm, red wavelength: 665 nm).

In addition, a black PET film was laminated on the surface of the outermost layer of one of the resulting optical multilayer films via an adhesive layer, and a diffusion film was laminated on the outermost layer of the other optical multilayer film via an adhesive layer. On the surface, a screen was prepared, and the gain of the screen was measured by a spectroradiance meter (CS-1000, manufactured and sold by KONICAMINOLTA HOLDINGS, INC.). Gain refers to the maximum value of the ratio of the brightness of the screen (cd/m ² ) to the brightness of the whiteboard when it is illuminated by light (the value is 1).

In addition, the luminance of the screen was measured by the above-mentioned luminance meter to determine the contrast. Specifically, the brightness of the screen is measured when it is illuminated by white light from a projector, then the brightness of the screen is measured when it is illuminated by black light from the projector, and the contrast ratio is measured from the ratio of the brightness of the white light to the brightness of the black light.

(Example 2)

Under substantially the same conditions as in Example 1, an optical multilayer film and a screen were produced, except that the number of optical films stacked in Example 1 was changed to 7, that is, the optical film (I)/ Optical film (II)/optical film (I)/optical film (II)/optical film (I)/optical film (II)/optical film (I).

(Example 3)

A screen was prepared under substantially the same conditions as in Example 1, except that the optical multilayer film in Example 1 was formed on one main surface of a PET film as a base, and was layered on the other main surface via an adhesive layer. A black PET film was laminated, and a diffuser film was laminated on the surface of the outermost layer of the optical multilayer film through an adhesive layer.

(Example 4)

The screen was produced under substantially the same conditions as in Example 1, except that instead of laminating a black PET film in Example 1, a black coating composition was applied to the rear side of the PET film by spraying. surface (the surface of the outermost layer of one of the optical multilayer films), and held at 75° C. for 30 minutes in the drying and curing step to form a light absorbing layer.

The black paint composition used was obtained by adding a solvent to the following composition.

Carbon black fine particles: trade name, ORIGIPLATE; manufactured and sold by Origin ELECTRIC Co., Ltd. (primary particle size: 15 nm)

Resin: Alkyd resin with hydroxyl groups

Curing agent used: trade name, POLYHARD MH (isocyanate-based curing agent), manufactured and sold by Origin ELECTRIC Co., Ltd.

(Example 5)

A screen was produced under substantially the same conditions as in Example 2, except that instead of laminating a black PET film in Example 2, the same treatment as in Example 4 was performed.

(Example 6)

A screen was produced under substantially the same conditions as in Example 3, except that instead of laminating a black PET film in Example 3, the same treatment as in Example 4 was performed.

(comparative example 1)

Under substantially the same conditions as in Example 1, an optical multilayer film and a screen were produced except that the number of optical films stacked in Example 1 was changed to 1, ie, the optical film (I).

(comparative example 2)

Under substantially the same conditions as in Example 1, an optical multilayer film and a screen were produced, except that the number of optical films stacked in Example 1 was changed to 2, that is, the optical film (I)/ Optical films (II).

The results are shown in Table 1.

The optical multilayer film with double-sided three-layer structure in embodiment 1 and 4 all has the reflectivity of 55%, and confirms that along with the increase of the stacked layer number of optical multilayer film, the reflectivity of optical multilayer film also In addition, the reflectances of the optical multilayer films with double-sided seven-layer structure in Examples 2 and 5 are both 90%. In addition, the reflectance of the optical multilayer film having a double-sided three-layer structure (Example 1) was 10% higher than that of the optical multilayer films having a single-side three-layer structure in Examples 3 and 6.

For screens, it has been confirmed that the increase in gain is proportional to the number of stacked layers constituting the optical multilayer film, and for screens with a double-sided seven-layer structure, when the light-absorbing layer is composed of black PET film (implementation In Example 2), a gain of 1.8 can be obtained, and when the light absorbing layer is formed of a black coating film (Example 5), a gain of 2.2 can be obtained. In addition, the contrast ratio is as follows: 26:1 in Example 1; 42:1 in Example 2; 21:1 in Example 3; 35:1 in Example 4; 55:1 in 5; 28:1 in Example 6.

The results of the comparative examples are as follows.

Comparative Example 1: The reflectance of the optical multilayer film is 17%, and the gain and contrast of the screen are 0.3 and 8:1, respectively.

Comparative Example 2: The reflectance of the optical multilayer film is 17%, and the gain and contrast of the screen are 0.3 and 8:1, respectively.

Table 1

Industrial Applicability

According to the invention of claim 1, a large-sized screen with high contrast and high gain can be realized.

According to the invention of claim 2, high reflectivity can be realized.

According to the inventions of claims 3 to 5, it is possible to form an optical multilayer film having the ability to reflect light in a desired wavelength range and transmit light other than the wavelength range, so that high contrast and high gain can be achieved in conformity with projector light sources and a high reflectivity screen.

According to the invention of claim 6, it is possible to obtain a screen from which a high-quality image with high contrast can be viewed with respect to RGB light sources.

According to the invention of claim 7, a high-quality image with higher contrast can be viewed from the screen.

According to the invention of claim 8, the observer can see a natural image on the screen by observing the scattered reflected light.

According to the invention of claim 9, large-sized screens with high contrast and high gain can be produced in large quantities.

According to the invention of claim 10, the production yield of large-sized screens having high contrast and high gain and high reflectance can be improved, so that screens can be manufactured in large quantities.

According to the inventions of claims 11 and 12, an optical film having a desired refractive index can be formed.

According to the invention of claim 12, it is possible to prepare a screen on which an observer can see a natural image by observing the scattered reflected light.

According to the invention of claim 11, a screen from which a high-quality image with higher contrast can be seen can be prepared.

Claims (11)

1. A screen, characterized in that it comprises: An optical multilayer film on a substrate, the optical multilayer film consisting of (2n+1) layers (where n is an integer of 1 or greater), each layer being highly reflective to light of a specific wavelength range, while at least High transmission of visible light outside this specific wavelength range; Wherein the optical multilayer film is formed by a coating method; Wherein the substrate is transparent, and the optical multilayer film is formed on both surfaces of the substrate by a coating method. 2. The screen according to claim 1, characterized in that said optical multilayer film comprises a stacked structure in which first optical films having a high refractive index and second optical films having a lower refractive index than the first optical films are stacked alternately with each other , and the outermost layer of the optical multilayer film is formed by the first optical film. 3. The screen according to claim 2, characterized in that said first optical film is a film comprising metal oxide fine particles, a dispersant and a binder; said second optical film is a film comprising fluorine-containing resin or _SiO2 fine particles granular film. 4. The screen according to claim 3, characterized in that the metal oxide fine particles are _TiO2 or _ZrO2 fine particles. 5. The screen according to claim 2, characterized in that said specific wavelength range includes wavelength ranges of red light, green light and blue light. 6. The screen according to claim 1, comprising a light absorbing layer to absorb light transmitted through said optical multilayer film. 7. The screen according to claim 1, characterized in that a light scattering layer is included on the outermost layer of said optical multilayer film to scatter light reflected by said optical multilayer film. 8. A method for preparing a screen comprising an optical multilayer film on a substrate, the optical multilayer film consisting of (2n+1) layers (wherein n is an integer of 1 or greater), each layer having a specific wavelength range Light is highly reflective and highly transmissive, at least for visible light outside that particular wavelength range; where The method for preparing the optical multilayer film comprises: A first coating step to form a first optical film with a high refractive index by a coating method; a second coating step to form a second optical film having a lower refractive index than the first optical film by a coating method; and The first coating step and the second coating step are performed alternately. 9. A method of preparing a screen comprising an optical multilayer film on both surfaces of a transparent substrate, wherein each optical multilayer film consists of (2n+1) layers (wherein n is an integer of 1 or greater), Each layer is highly reflective to light in a particular wavelength range and highly transmissive at least to visible light outside that particular wavelength range; wherein The method for preparing the optical multilayer film comprises: A first coating step to form a first optical film with a high refractive index on both surfaces of the substrate to be coated by a dip coating method; A second coating step to form a second optical film having a lower refractive index than the first optical film on both surfaces of the substrate to be coated by a dip coating method; and The first coating step and the second coating step are performed alternately. 10. The method of preparing a screen according to claim 9, characterized in that it comprises: A step of forming a light absorbing layer on the outermost layer on one side of the optical multilayer film to absorb light transmitted through the optical multilayer film. 11. The method for preparing a screen according to claim 10, characterized in that it comprises: A step of forming a light scattering layer on the outermost layer on the other side of the optical multilayer film to scatter light emitted by the optical multilayer film.

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