Transparent screen film and method for manufacturing the same

Abstract

To provide a transparent screen film and a method for manufacturing the same that can be used with both transmissive and reflective projection methods and has excellent transparency. [Solution] The transparent screen film contains a water-soluble resin and acrylic particles having hydrophilic groups, with the median diameter of the acrylic particles being between 100 nm and 1000 nm.

Description

Technical Field

[0001] The present invention relates to a film for a transparent screen and a method for manufacturing the same.

Background Art

[0002] A film for a transparent screen is generally used by being disposed on a transparent substrate such as window glass. When the film for a transparent screen is disposed, usually (when not projecting), a view (background) through the film for a transparent screen can be visually recognized, while when an image is projected from an image display device such as a projector, the image can be projected onto the film. Therefore, it is expected for various applications such as digital signage applications and in-vehicle information display monitors.

[0003] [[ID=十六]]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0005] Incidentally, there are two types of projection methods for transparent screen films: front projection (reflective) projection, which projects the image from the front, and rear projection (transmissive) projection, which projects the image from the rear. For both projection methods, good projection performance is required, allowing for a clear image to be projected onto the screen, while also maintaining transparency when not projected.

[0006] However, Patent Documents 1-3 only mention transmission projection and do not disclose whether they are suitable for reflection projection. Furthermore, the screens disclosed in Patent Documents 1-2 require expensive diamond particles, so alternative materials are needed. Moreover, in all of the screens in Patent Documents 1-4, particles necessary for reflection, such as diamond particles and light-diffusing particles, tend to aggregate within the film, resulting in insufficient transparency, thus requiring greater transparency.

[0007] The present invention aims to provide a transparent screen film and a method for manufacturing the same that can be used with both transmissive and reflective projection methods and have excellent transparency. [Means for solving the problem]

[0008] The present invention [1] includes a transparent screen film containing a water-soluble resin and acrylic particles having hydrophilic groups, wherein the median diameter of the acrylic particles is 100 nm or more and 1000 nm or less.

[0009] The present invention [2] includes the transparent screen film described in [1], wherein the acrylic particles are polymers of acrylic monomers having an HLB value of 9 or more and 18 or less.

[0010] The present invention [3] includes a transparent screen film according to [1] or [2], wherein the water-soluble resin contains polyvinyl alcohol.

[0011] The present invention [4] includes a transparent screen film according to any one of [1] to [3], wherein the hydrophilic group is an oxyalkylene group.

[0012] The present invention [5] includes a transparent screen film according to any one of [1] to [4], wherein the total light transmittance is 90% or more and the haze value is 1% or more and 25% or less.

[0013] The present invention [6] includes a method for manufacturing a transparent screen film, comprising, in order: a preparation step of preparing a mixed solution containing a water-soluble resin, an acrylic monomer having a hydrophilic group, an organic solvent, and water; a film-forming step of forming a coating film of the mixed solution; a removal step of removing the organic solvent and water from the coating film; and a polymerization step of polymerizing the acrylic monomer to form acrylic particles having a median diameter of 100 nm or more and 1000 nm or less.

[0014] The present invention [7] includes the manufacturing method described in [6], wherein the HLB value of the acrylic monomer is 9 or more and 18 or less.

[0015] The present invention [8] includes a method for producing the water-soluble resin according to [6] or [7], wherein the water-soluble resin comprises polyvinyl alcohol.

[0016] The present invention [9] includes a manufacturing method according to any one of [6] to [8], wherein the mixed solution further contains a polymerization initiator.

[0017] The present invention

[10] includes a manufacturing method according to any one of [6] to [9], wherein the preparation step involves mixing a first solution containing the water-soluble resin and water with a second solution containing the acrylic monomer and the organic solvent. [Effects of the Invention]

[0018] The film for a transparent screen of the present invention has good projection properties for both transmissive and reflective projection methods and also has excellent transparency. The manufacturing method of the present invention can surely manufacture a film for a transparent screen that has good projection properties for both transmissive and reflective projection methods and also has excellent transparency.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 shows a schematic diagram of a method for measuring the 45° reflectance. [Figure 2] FIG. 2 shows a schematic diagram of a method for measuring the 45° transmittance. [Figure 3] FIG. 3 shows a schematic diagram of a method for measuring the projection properties in the reflective (front type). [Figure 4] FIG. 4 shows a schematic diagram of a method for measuring the projection properties in the transmissive (rear type).

Embodiments for Carrying Out the Invention

[0020] 1. Manufacturing Method of Film for Transparent Screen An example of the manufacturing method of the film for a transparent screen of the present invention includes a preparation step, a film formation step, a removal step, and a polymerization step in this order. Each step will be described below.

[0021] (Preparation Step) In this step, a mixed solution containing a water-soluble resin, an acrylic monomer, an organic solvent, and water is prepared. Preferably, a mixed solution further containing a surfactant and / or a polymerization initiator is prepared.

[0022] The water-soluble resin functions as a matrix resin for transparent screen films, and examples include polyvinyl alcohol (PVA), polyvinylpyrrolidone, polyethylene oxide, hydroxymethylcellulose, water-soluble acrylic resin, and water-soluble urethane resin. One or more of these can be used. PVA is preferred from the viewpoint of having excellent water solubility and film-forming properties, and being able to form a smooth film. In this invention, a resin is considered water-soluble if 1 g of the resin is added to 100 g of water at 95°C and stirred, and the resin completely dissolves in the water.

[0023] The degree of saponification of the PVA is, for example, 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and also, for example, 100 mol% or less, preferably 99 mol% or less, more preferably 98 mol% or less. By using such PVA, a transparent screen film with excellent transparency and projection properties can be obtained.

[0024] The degree of polymerization of the PVA is, for example, 300 or more, preferably 1000 or more, and also, for example, 3000 or less, preferably 2500 or less. By using such PVA, a transparent screen film with excellent projection properties can be obtained.

[0025] Acrylic monomers are raw materials for light-scattering particles that exhibit projection properties as reflective screens, and have (meth)acrylic groups and hydrophilic groups. The (meth)acrylic groups are acrylic groups or methacrylic groups, and their number is, for example, 1 or more, preferably 2 or more, more preferably 3 or more, and also, for example, 10 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less. This allows for the development of appropriate crosslinking properties and the formation of light-scattering particles of good size. Examples of hydrophilic groups include oxyalkylene groups, hydroxyl groups, carboxyl groups, sulfone groups, phosphono groups, amide groups, amino groups, imide groups, aldehyde groups, and acetyl groups. Specific examples of oxyalkylene groups include polyoxyethylene groups, polyoxypropylene groups, and polyoxybutylene groups. From the viewpoint of hydrophilicity, oxyalkylene groups are preferred, and polyoxyethylene groups are preferred.

[0026] Examples of such acrylic monomers include trimethylpropane ethoxylate triacrylate (ETPTA), diethylene glycol diacrylate (DEGDA), poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) dimethacrylate (PEGDMA), polyglycerin-based acrylates, carboxyethyl acrylate, phenoxydiethylene glycol acrylate, neopentyl glycol diacrylate, glycerin propoxy triacrylate, pentaerythritol (tri / tetra)acrylate, and zirconium carboxyethyl acrylate. One or more of these can be used. From the viewpoint of imparting hydrophilic groups, ETPTA, DEGDA, and polyglycerin-based acrylates are preferred, more preferably ETPTA and polyglycerin-based acrylates, and even more preferably ETPTA.

[0027] The number-average molecular weight (Mn) of the acrylic monomer is, for example, 200 or more, preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more, and also, for example, 2000 or less, preferably 1500 or less, and more preferably 1000 or less.

[0028] The HLB value of the acrylic monomer is, for example, 4 or higher, preferably 9 or higher, more preferably 13 or higher, even more preferably 14 or higher, and also, for example, 18 or lower, preferably 17 or lower, and more preferably 16 or lower. By setting the HLB value within the above range, a good balance of hydrophilicity and hydrophobicity of the acrylic monomer is achieved. Therefore, the acrylic monomer can be reliably dissolved in the mixed solution containing water and uniformly present in the coating film during the film formation process. On the other hand, after the removal process, the acrylic monomer is not easily miscible with the water-soluble resin, so particles consisting of the acrylic monomer can be uniformly phase-separated in the water-soluble resin. Therefore, transparency and projection can be further improved. The HLB (Hydrophilic-Lipophilic Balance) value is a value based on the Griffin method and is calculated by the following formula (1).

[0029] HLB = 20 × Mh / M (1) In the formula, Mh is the molecular mass of the hydrophilic group of the molecule, and M represents the molecular mass of the entire molecule. The hydrophilic group is the one described above.

[0030] Examples of surfactants include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants, with cationic surfactants being preferred. This allows for uniform dispersion of acrylic monomers in the water-soluble resin after the drying process, thereby further improving the transparency and projectability of the transparent screen film. Examples of cationic surfactants include quaternary ammonium salt type surfactants such as hexadecyltrimethylammonium bromide (CTAB), lauryltrimethylammonium bromide, benlyditrimethylammonium bromide, hexadecyltrimethylammonium chloride (CTAC), lauryltrimethylammonium chloride, octyltrimethylammonium chloride, tetramethylammonium chloride, dodecyldimethylbenzylammonium chloride, benzyltrimethylammonium chloride, and tetramethylammonium hydroxide; alkylamine salt type surfactants such as monomethylamine hydrochloride, dimethylamine hydrochloride, and trimethylamine hydrochloride; and pyridine type surfactants such as butylpyridinium chloride, dodecylpyridinium chloride, and cetylpyridinium chloride. One or more of these can be used. Preferably, quaternary ammonium salt type surfactants are included, and more preferably, CTAB and CTAC are included.

[0031] The polymerization initiator is a component for initiating the polymerization of acrylic monomers, and may be either a photopolymerization initiator or a thermal polymerization initiator. This ensures reliable polymerization of acrylic monomers, making it easy to obtain the desired acrylic particles. Examples of thermal polymerization initiators include azo compounds such as azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylisobutyronitrile), and dimethyl-2,2'-azobis(isobutyrate); and organic peroxides such as dibenzoyl peroxide (BPO), dilauroyl peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, and diisopropyl peroxydicarbonate. Preferably, azo compounds are used. Examples of photopolymerization initiators include alkylphenone compounds such as (1-hydroxycyclohexyl)phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, and 2-hydroxy-2-methyl-1-phenylpropanone; acylphosphine oxide compounds such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,6-dichlorobenzoyldiphenylphosphine oxide; and oxime ester compounds such as 1,2-octanedione, 1-[4-(phenylthio)phenyl]-,2-(o-benzoyl oxime), ethanone, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyl oxime). Alkylphenone compounds are preferred. One or more of these polymerization initiators can be used.

[0032] Preferably, the organic solvent is a polar organic solvent. This allows the acrylic monomer and polymerization initiator to be dissolved, and acrylic particles of the desired size to be dispersed in the polymerization process. Examples of polar organic solvents include tetrahydrofuran (THF), acetone, acetonitrile, methanol, ethanol, n-propanol, isopropyl alcohol, and ethylene glycol. One or more of these can be used. Preferably, THF, acetone, and methanol are used, and more preferably, THF.

[0033] The preparation method involves simultaneously or sequentially mixing a water-soluble resin, an acrylic monomer, an organic solvent, and water. Preferably, a first solution containing the water-soluble resin and water, and a second solution containing the acrylic monomer and an organic solvent are prepared separately, and then the first and second solutions are mixed. In particular, when adding a surfactant, it may be mixed in advance with either the first or second solution, and the surfactant should be mixed into the solution in which it is more soluble. Preferably, the surfactant is mixed into the first solution. Similarly, when adding a polymerization initiator, it may be mixed in advance with either the first or second solution, and the polymerization initiator should be mixed into the solution in which it is more soluble. Preferably, the polymerization initiator is mixed into the second solution. This ensures that a mixed solution in which the water-soluble resin, acrylic monomer, surfactant, and polymerization initiator are dissolved in liquid can be reliably obtained. That is, aggregation or precipitation of each component in the solution can be suppressed.

[0034] For the preparation of the first solution, for example, a water-soluble resin and a surfactant are added to water simultaneously or sequentially and stirred. For the preparation of the second solution, for example, an acrylic monomer and a polymerization initiator are added to an organic solvent simultaneously or sequentially and stirred.

[0035] Regarding the mixing ratio, any ratio that allows each component to dissolve in the first and second solutions is acceptable. The content of the water-soluble resin in the total amount of the first solution is, for example, 3% by mass or more, preferably 5% by mass or more, and also, for example, 30% by mass or less, preferably 20% by mass or less. The content of the surfactant in the first solution is, for example, 1 part by mass or more, preferably 2 parts by mass or more, and also, for example, 10 parts by mass or less, preferably 8 parts by mass or less, per 100 parts by mass of the water-soluble resin. The content of the acrylic monomer in the total amount of the second solution is, for example, 10% by mass or more, preferably 30% by mass or more, and also, for example, 80% by mass or less, preferably 70% by mass or less. The content of the polymerization initiator in the second solution is, for example, 1 part by mass or more, preferably 2 parts by mass or more, and also, for example, 20 parts by mass or less, preferably 15 parts by mass or less, per 100 parts by mass of the acrylic monomer. The mixing ratio of the first solution and the second solution should be such that the proportion of acrylic monomer (acrylic particles after the polymerization process) in 100 parts by mass of water-soluble resin is, for example, 1 part by mass or more, preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and also, for example, 25 parts by mass or less, preferably 15 parts by mass or less, more preferably 5 parts by mass or less. As an example, the second solution may be mixed in an amount of, for example, 1 to 100 parts by volume (preferably 3 to 50 parts by volume) to 1000 parts by volume of the first solution.

[0036] This yields a mixed solution containing a water-soluble resin, an acrylic monomer, an organic solvent, and water. Preferably, a mixed solution further containing a surfactant and / or a polymerization initiator is obtained. In the mixed solution, the water-soluble resin, the acrylic monomer, and the additional surfactant and polymerization initiator are completely dissolved in the water / organic solvent mixture.

[0037] (Film forming process) In this step, a coating film of the mixed solution is formed. For example, the mixed solution is applied to the desired substrate using a known film-forming device such as an applicator.

[0038] The film thickness of the coating during application (wet film thickness) is, for example, 300 μm or more, preferably 500 μm or more, and also, for example, 2000 μm or less, preferably 1000 μm or less. By setting the film thickness within the above range, water and organic solvents can be evaporated at relatively low temperatures, and a transparent screen film of the desired thickness can be obtained.

[0039] It is preferable to select a substrate that is easily peelable from the transparent screen film after obtaining the transparent screen film from the coating. Examples of substrates include polyimide film, polyethylene terephthalate film, and polytetrafluoroethylene film.

[0040] This results in the formation of a wet coating film on the substrate.

[0041] (Removal process) In this step, organic solvents and water are removed from the coating film. In other words, the coating film is dried.

[0042] Specifically, the coating film is heated to evaporate the organic solvent and water. The heating temperature is, for example, 30°C or higher, preferably 40°C or higher, and also, for example, 60°C or lower, preferably 50°C or lower. By keeping the heating temperature below the above upper limit, the organic solvent and water can be gradually removed, making the acrylic monomer insoluble in the water-soluble resin and allowing for phase separation. Furthermore, polymerization of the acrylic monomer by the thermal polymerization initiator can be suppressed. Heating may be carried out under either reduced pressure or atmospheric pressure, but from the viewpoint of workability, it is preferable to carry it out under atmospheric pressure.

[0043] The heating time is determined appropriately according to the heating temperature, but for example, it is 30 minutes or more, preferably 60 minutes or more, and for example, 24 hours or less, preferably 12 hours or less.

[0044] In the removal process, the process should be carried out until the ratio of the film thickness after the removal process (dry film thickness) to the film thickness at the time of application (wet film thickness) is, for example, 20% or less, preferably 10% or less, and more preferably 5% or less. In the removal process, it is not necessary to completely remove the organic solvent and water from the film; small amounts of organic solvent and water may remain. Most of the remaining organic solvent and water will be removed in the polymerization process described later.

[0045] This results in the formation of a dry coating film on the substrate.

[0046] After the removal process, the dried coating film is mainly composed of a water-soluble resin, an acrylic monomer, a surfactant, and an additional polymerization initiator. Because the acrylic monomer has a (meth)acrylic group, it is not easily miscible with the water-soluble resin, and the acrylic monomer undergoes phase separation in a uniformly dispersed state within the water-soluble resin, and these particles grow without agglomerating with each other. As a result, a dried coating film is formed in which acrylic monomer particles of a predetermined size are uniformly dispersed. Preferably, the inclusion of a surfactant leads to greater dispersion and the formation of smaller particles. In the process of gradually removing water and polar solvents, the acrylic monomer particles may be compressed inward in the vertical direction due to the compressive force associated with the decrease in volume of the water-soluble resin (decrease in coating film thickness), resulting in an ellipsoidal shape.

[0047] (Polymerization process) In this process, acrylic monomers are polymerized.

[0048] For example, if the polymerization initiator is a thermal polymerization initiator, the dry coating film is heated. The heating temperature is, for example, 60°C or higher, preferably 80°C or higher, and also, for example, 150°C or lower, preferably 100°C or lower. The heating time is, for example, 10 minutes or more, preferably 20 minutes or more, and also, for example, 240 minutes or less, preferably 120 minutes or less. On the other hand, if the polymerization initiator is a photopolymerization initiator, the dry coating film is irradiated with ultraviolet light, for example. The irradiation time is, for example, 5 minutes or more, preferably 20 minutes or more, and also, for example, 240 minutes or less, preferably 120 minutes or less. Even when a photopolymerization initiator is used, the above heating may be performed as needed.

[0049] In the polymerization process, particles made of acrylic monomers undergo a polymerization reaction to become acrylic particles made of acrylic polymers. The median diameter of the primary acrylic particles is, for example, 100 nm or more, preferably 200 nm or more, and also, for example, 1000 nm or less, preferably 500 nm or less. When the particle diameter is within the above range, projected light can be appropriately scattered by the acrylic particles, resulting in excellent projection performance. Acrylic particles often have shapes such as spheres or ellipsoids, and are particularly often ellipsoidal. In the case of ellipsoids, the median diameter can be determined by measuring the major axis of the ellipsoid.

[0050] This forms a transparent screen film on the substrate. If necessary, the transparent screen film is peeled off the substrate. In the resulting transparent screen film, acrylic particles are uniformly dispersed in a water-soluble resin.

[0051] The transparent screen film can also be used as a laminate with the substrate without being peeled off. Furthermore, a protective layer may be placed on any surface of the laminate. The protective layer may be a coating film, or a new substrate may be used. In the case of a substrate, this can be done, for example, by bonding adjacent components together via an adhesive layer or similar.

[0052] Transparent screen films can be applied to surfaces such as glass windows, glass walls, transparent partitions, and automobile windshields via adhesive layers or other bonding agents.

[0053] The manufacturing method of the present invention makes it possible to produce a transparent screen film that has excellent transparency and can be used with both transmissive and reflective projection methods. In particular, the manufacturing method of the present invention makes it possible to uniformly disperse acrylic particles (light-scattering particles) of a predetermined size necessary to exhibit the function of a transparent screen in a water-soluble resin (matrix resin). This is presumed to be because, by using a crosslinkable monomer (acrylic monomer having a hydrophilic group) that dissolves in the solvent (water) but is poorly compatible with the matrix resin (water-soluble resin) and a surfactant, and by carrying out a solvent removal step and a polymerization step, the acrylic monomer is uniformly present in the wet coating film when the coating film is formed, and after the solvent removal step, the acrylic monomer is uniformly dispersed in the dry coating film (water-soluble resin) at a predetermined size and polymerizes.

[0054] (Film for transparent screens) The transparent screen film of the present invention contains a water-soluble resin and acrylic particles. The transparent screen film of the present invention can be suitably manufactured, for example, by the manufacturing method described above. In this case, the transparent screen film preferably contains a water-soluble resin, acrylic particles, a surfactant, and a polymerization initiator.

[0055] The water-soluble resin, acrylic particles, surfactant, and polymerization initiator are the water-soluble resin, acrylic particles, surfactant, and polymerization initiator described above in the manufacturing method of the present invention.

[0056] The content of water-soluble resin in the transparent screen film is, for example, 75% by mass or more, preferably 90% by mass or more, and also, for example, 98% by mass or less, preferably 95% by mass or less.

[0057] The content of acrylic particles is, for example, 1 part by mass or more, preferably 2 parts by mass or more, more preferably 3 parts by mass or more, and also, for example, 25 parts by mass or less, preferably 15 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of water-soluble resin. By setting the content of acrylic particles to above the lower limit above, excellent projection properties are obtained. On the other hand, by setting the content of acrylic particles to below the upper limit above, excellent transparency properties are obtained.

[0058] If a surfactant is included, its content is, for example, 0.5 parts by mass or more, preferably 1 part by mass or more, and also, for example, 10 parts by mass or less, preferably 5 parts by mass or less, per 100 parts by mass of water-soluble resin. If the surfactant content is within the above range, the acrylic particles can be uniformly dispersed in the water-soluble resin, resulting in good transparency and excellent projection characteristics for both transmission and reflection.

[0059] If a polymerization initiator is included, its content is, for example, 1 part by mass or more, preferably 2 parts by mass or more, and also, for example, 20 parts by mass or less, preferably 10 parts by mass or less, per 100 parts by mass of acrylic particles.

[0060] In addition to the components listed above, the transparent screen film may also contain other components as needed, such as UV absorbers, antioxidants, and lubricants.

[0061] The film thickness (dry film thickness) of the transparent screen film is, for example, 10 μm or more, preferably 20 μm or more, and also, for example, 500 μm or less, preferably 100 μm or less.

[0062] The total light transmittance of the transparent screen film is, for example, 85% or more, preferably 90% or more, and also, for example, 99% or less, preferably 95% or less. The haze value is, for example, 1% or more, preferably 3% or more, and also, for example, 25% or less, preferably 10% or less. This results in excellent transparency of the transparent screen film. The total light transmittance and haze value can be measured in accordance with JIS K7361 and JIS K7136.

[0063] The transparent screen film of the present invention possesses excellent transparency and is compatible with both transmissive and reflective projection methods. In particular, it has high total light transmittance and moderately low haze, resulting in superior transparency. Furthermore, its high 45-degree reflectance and 45-degree transmittance provide excellent projection performance for both transmissive and reflective projection methods. The transparent screen film of the present invention can be used as a screen for both transmissive and reflective projection methods and can be installed and used, for example, in glass windows, glass walls, transparent partitions, and automobile windshields. [Examples]

[0064] The present invention will now be described in detail with reference to examples and comparative examples, but the scope of the present invention is not limited thereto.

[0065] <Measurement methods for evaluating various physical properties and performance> (molecular weight) Acrylic monomers were dissolved in tetrahydrofuran (THF) to a concentration of 0.1 w / v% and filtered through a 0.45 μm syringe filter. Gel permeation chromatography (GPC) was performed on this solution (using the GULLIVER SYSTEM, manufactured by JASCO Corporation) to calculate the number-average molecular weight (Mn) in PEG equivalent. The measurement conditions were as follows. Column: HSPgel TM HR 1.0+HSPgel TM HR 2.0+HSPgel TM HR 2.5 (Waters brand) Column temperature: 40℃ Mobile phase: THF Flow rate: 0.3mL / min Detector: Differential refractometer (manufactured by Lab System Equipment Co., Ltd., "RI-2000")

[0066] (HLB value) For acrylic monomers, the HLB value was calculated using the formula "HLB value = 20 × Mh / M". Mh is the molecular mass of the hydrophilic group in the acrylic monomer, and M is the number-average molecular weight Mn of the acrylic monomer obtained from the molecular weight measurement described above.

[0067] (Film thickness measurement) The film thickness was measured using a film thickness gauge (SWT-8000II, manufactured by Sanko Electronics Laboratory). The film thickness was defined as the average of five points within the plane of the film.

[0068] (Particle size) The median diameter of primary particles in acrylic-based particles was determined by cross-sectional observation using a scanning electron microscope (JEOL Ltd., "JSM-7610F"). Specifically, the film was frozen and cut in liquid nitrogen, and the cross-section was imaged using an acceleration voltage of 1 kV, a working distance of 15 mm, and LEI mode. In the obtained SEM image (magnification 10,000x, area 9 × 12 μm), the length of all particles within the area was measured using the image processing software ImageJ, and the median diameter was determined. If the particles were ellipsoidal, their major axis was measured.

[0069] (Total light transmittance) The turbidity was measured using a turbidimeter (NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7361.

[0070] (Haze value) The turbidity was measured using a turbidimeter (NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136.

[0071] (45°reflectance) Light was shone from a halogen light source 2 (Ocean Optics) equipped with a collimating optical fiber (Ocean Optics, "74-UV", "P600-2-UV / VIS") onto film 1 in the direction normal to the film (0°), and the reflected light at the 45° direction was detected using a spectrometer 3 (Ocean Optics, "USB2000+") equipped with a collimating optical fiber (see Figure 1). A white light diffuser made of barium sulfate was used as the standard (100% reference), and the intensity ratio to its reflected light intensity was determined as the 45° reflectance.

[0072] (45°transparency) Light with a wavelength of 525 nm was shone from an LED light source 4 (manufactured by CivilLaser) equipped with a collimating optical fiber, in the direction normal to film 1 (0°). The transmitted light at 45° behind film 1 (135° from the direction of illumination) was detected using a spectrometer 3 (same as above) equipped with a collimating optical fiber (see Figure 2). The intensity of the film prepared in Comparative Example 1 was set as the standard (1x), and the degree of multiplication of its transmitted light intensity was determined as the 45° transmittance.

[0073] (transparency) Film 1 for transparent screens was fixed in a filter holder, and subject 5 was placed behind the film. Subject 5 was visually observed through the film from an angle of 45° from the normal direction of film 1 (see Figures 3 and 4: the dashed arrows in each figure indicate the line of sight, and the solid arrows in each figure indicate the projection direction of the image). The transparency of the film at this time was evaluated based on the following criteria. 5: The outline of the subject could be observed very clearly. 4: The outline of the subject could be observed sufficiently. 3: I was able to observe the outline of the subject in general. 2: The outline of the subject was slightly blurred. 1: The subject's outline was completely blurred.

[0074] (Reflective projection) A transparent screen film 1 was fixed in a filter holder, and the subject 5 was placed behind the film. A projector 6 was also installed on the viewing side, 20 cm away from the film 1 in the normal direction (0°) (see Figure 3). An image was projected from the projector 6 onto the film 1, and the film 1 was observed visually. The projection quality at this time was evaluated based on the following criteria. 5: The projected image was very bright, and the image content was clearly visible. 4: The projected image was sufficiently bright, and the image content could be clearly seen. 3: The projected image was bright, and the image content could be confirmed. 2: The projected image was slightly dark, but the image content was discernible. 1: The projected image was dark, and parts of the image content could not be seen.

[0075] (Transmissive projection properties) A transparent screen film 1 was fixed with a filter holder, and the subject 5 was placed behind the film. A projector 6 was also installed on the opposite side of the film (through the film) from the viewing side, at a distance of 20 cm from the film 1 in the normal direction (0°) (see Figure 4). An image was projected from the projector 6 onto the film 1, and the film 1 was observed visually. The projection quality at this time was evaluated based on the same criteria as for the reflective projection quality described above.

[0076] <Example 1> Polyvinyl alcohol powder (PVA, manufactured by Nippon Vitro Vale Co., Ltd., trade name "JM17") and water were mixed and stirred at 95°C for 4 hours to prepare a 9 wt% PVA aqueous solution. To 5 g of the PVA aqueous solution, 12.5 mg of hexadecyltrimethylammonium bromide (CTAB) was added to prepare the first solution. On the other hand, to 100 mg of the crosslinkable monomer trimethylpropaneethoxylate triacrylate (ETPTA, manufactured by Sigma-Aldrich, product number "412198", Mn1000 (as per the above molecular weight measurement result)), 50 μL of azobisisobutyronitrile (AIBN) tetrahydrofuran solution (10 w / v%) was added to prepare the second solution (approximately 140 μL) in which the ratio of AIBN to ETPTA was 5 wt%.

[0077] 15 μL of the second solution was added to the first solution, and the mixture was stirred and degassed. At this time, the amounts of each solid component in the mixed solution were PVA 450 mg, CTAB 12.5 mg, ETPTA 10.8 mg, and AIBN 0.54 mg. At this point, it was confirmed that the mixed solution was a clear, viscous solution.

[0078] The mixed solution was applied onto a polyimide film using an applicator to form a wet film with a thickness of 750 μm. The organic solvent and water were removed by drying the film at 40°C for 1 hour. At this point, the dry film thickness was 24 μm.

[0079] Next, the dried coating was polymerized by placing it at 80°C for 30 minutes. This resulted in obtaining a transparent screen film on the substrate. After that, the transparent screen film was peeled off the substrate after natural cooling.

[0080] The resulting transparent screen film had a total light transmittance of 91.5% and a haze value of 1.0%. The 45° reflectance was 0.73%, and the 45° transmittance was 40 times. The median diameter of the primary acrylic particles in the film was 117 nm.

[0081] <Examples 2-11> The transparent screen films for each example were manufactured in the same manner as in Example 1, except that the materials and manufacturing conditions were changed as shown in Table 1. The physical properties of these transparent screen films are shown in Table 2.

[0082] <Examples 12-13> The materials and manufacturing conditions were changed as shown in Table 1, and the transparent screen film for each example was manufactured in the same manner as in Example 1, except that the polymerization process involved irradiation with ultraviolet light at a wavelength of 254 nm for 30 minutes. The physical properties of this transparent screen film are shown in Table 2.

[0083] <Example 14> A transparent screen film was manufactured in the same manner as in Example 1, except that the materials and manufacturing conditions were changed as shown in Table 1, and the amount of CTAB was set to 20 mg. The physical properties of this transparent screen film are shown in Table 2.

[0084] <Comparative Examples 1-2> A comparative example of a transparent screen film was manufactured in the same manner as in Example 1, except that the materials and manufacturing conditions were changed as shown in Table 1. In Comparative Example 2, instead of adding the second solution, 10 mg of Al2O3 was added. The physical properties of this transparent screen film are shown in Table 2.

[0085] <Comparative Example 3> A commercially available transparent screen film was used as the film for the transparent screen. This film is made of PET resin coated with a paint containing zirconia nanoparticles as a light-diffusing layer. The physical properties of this transparent screen film are shown in Table 2.

[0086] [Table 1]

[0087] [Table 2]

[0088] The abbreviations listed in the table refer to the following: JM17: Polyvinyl alcohol powder, manufactured by Nippon Vi-Poval Co., Ltd., degree of polymerization 1700, degree of saponification 95.5-97.5 mol%, the value in parentheses indicates the aqueous solution concentration (weight percentage). JF05: Polyvinyl alcohol powder, manufactured by Nippon Vi-Poval Co., Ltd., degree of polymerization 500, degree of saponification 98.0-99.0 mol%, the value in parentheses indicates the aqueous solution concentration (weight percentage). • CTAB: Hexadecyltrimethylammonium bromide, manufactured by Tokyo Chemical Industry Co., Ltd., product code "H0081", cationic surfactant • CTAC: Hexadecyltrimethylammonium chloride, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product code "087-06032", cationic surfactant • ETPTA: Trimethylpropane ethoxylate triacrylate, manufactured by Sigma-Aldrich, product number "412198", Mn 1000 (as per the molecular weight measurement above), HLB value 15 SA-TE12: Polyglycerin-based acrylate, manufactured by Sakamoto Pharmaceutical Co., Ltd., 6 acrylic groups, Mn 1000 (as per the molecular weight measurement above), HLB value 13 • PEGDA n=9: Polyethylene glycol diacrylate (n=approx. 9), manufactured by Tokyo Chemical Industry Co., Ltd., product code "P2708", average number of oxyethylene addition moles 8.5~9.5, Mn400 (as measured by the above molecular weight measurement), HLB value 14 • PEGDA n=14: Polyethylene glycol diacrylate (n=approx. 14), manufactured by Tokyo Chemical Industry Co., Ltd., product code "P2757", average number of oxyethylene addition moles 13.5~15.0, Mn 800 (as measured by the above molecular weight measurement), HLB value 17 • DEGDA: Diethylene glycol diacrylate, manufactured by Tokyo Chemical Industry Co., Ltd., product code "D5381", Mn250 (as per the molecular weight measurement above), HLB value 11 • Al2O3: α-alumina, 0.5 μm, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product code "015-13001" • AIBN: Azobisisobutyronitrile, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product code "019-04932", thermal polymerization initiator Irgacure® 184: (1-Hydroxycyclohexyl)phenyl ketone, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product code "326-50042", photopolymerization initiator. • BPO: Dibenzoyl peroxide, manufactured by Nacalai Tesque, product code "044-22", thermal polymerization initiator [Explanation of symbols]

[0089] 1. Transparent screen film 2. Halogen light source 3 Spectrometer 4 LED light source 5 Subject 6 Projectors

Claims

1. It contains a water-soluble resin and acrylic particles having hydrophilic groups. A transparent screen film in which the median diameter of the acrylic particles is 100 nm or more and 1000 nm or less.

2. The transparent screen film according to claim 1, wherein the acrylic particles are polymers of acrylic monomers having an HLB value of 9 or more and 18 or less.

3. The transparent screen film according to claim 1, wherein the water-soluble resin contains polyvinyl alcohol.

4. The transparent screen film according to claim 1, wherein the hydrophilic group is an oxyalkylene group.

5. A transparent screen film according to claim 1, wherein the total light transmittance is 90% or more and the haze value is 1% or more and 25% or less.

6. Preparation step of preparing a mixed solution containing a water-soluble resin, an acrylic monomer having a hydrophilic group, an organic solvent, and water. A film-forming step of forming a coating film of the mixed solution, A removal step to remove the organic solvent and water from the coating film, and, Polymerization step of polymerizing the acrylic monomer to form acrylic particles having a median diameter of 100 nm or more and 1000 nm or less. A method for manufacturing a transparent screen film, comprising the following elements in order.

7. The manufacturing method according to claim 6, wherein the HLB value of the acrylic monomer is 9 or more and 18 or less.

8. The manufacturing method according to claim 6, wherein the water-soluble resin contains polyvinyl alcohol.

9. The manufacturing method according to claim 6, wherein the mixed solution further contains a polymerization initiator.

10. The manufacturing method according to claim 6, wherein the preparation step involves mixing a first solution containing the water-soluble resin and water with a second solution containing the acrylic monomer and the organic solvent.

Images