Reflection control film for automobiles

Abstract

To provide an in-vehicle reflection control film having an optical characteristic suited for in-vehicle use.SOLUTION: An in-vehicle reflection control film 10 includes a base material 1 and a reflection control layer 5 stacked on the base material 1. When a light amount of specularly reflected light of light incident from an oblique direction of 30° with respect to a normal line of the base material 1 on the base material 1 on which the reflection control layer 5 is not stacked, is defined as 100%, a light amount of specularly reflected light of light incident from an oblique direction of 30° with respect to the normal line of the reflection control film 10 on the reflection control layer 5 of the in-vehicle reflection control film 10 is 0 to 20.61%, a light amount of reflected light in a direction of a reflection angle ±5° of the specularly reflected light is 0.3 to 2.0%, and haze is 3 to 11%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an in-vehicle reflection control film used in an in-vehicle display device or the like. [Background technology]

[0002] Traditionally, center information displays and center console displays have been used as in-vehicle display devices for car navigation systems, etc. In recent years, the number of in-vehicle display devices has been increasing, and new in-vehicle display devices such as digital outer monitors, digital inner monitors, and digital meter clusters are expected to be used. Since light enters the interior of a vehicle from various directions through the windows, the visibility of in-vehicle display devices can be ensured by providing them with optical films with anti-reflection properties.

[0003] For example, Patent Document 1 describes an antireflection film that is configured by laminating multiple layers on an optical substrate and has a reflectance of 0.1% or less for light incident at an angle of 45 degrees in the wavelength range of 300 to 660 nm. Also, Patent Document 2 describes an optical sheet in which translucent inorganic particles and / or translucent organic particles are dispersed on at least one surface of a transparent substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-74903 [Patent Document 2] Patent No. 5725216 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to the image displayed on the display surface of an in-vehicle display device, images such as the light from nearby vehicles or streetlights may be reflected. Until now, it has been common to suppress reflections on the display surface to ensure the visibility of the displayed image, but adequate control of reflected light in in-vehicle display devices has not been fully studied, and there is also room for improvement in the optical properties required for optical films used in in-vehicle display devices.

[0006] Therefore, an object of the present invention is to provide an in-vehicle reflection control film having optical properties suitable for in-vehicle use. [Means for solving the problem]

[0007] The reflection control film for vehicle use according to the present invention is an in-vehicle reflection control film comprising a substrate and a reflection control layer laminated on the substrate, wherein the reflection control layer comprises an antiglare layer laminated on the substrate and a low refractive index layer laminated on the antiglare layer without any other layer therebetween, and when the amount of specularly reflected light of light incident on a substrate not laminated with a reflection control layer from a direction obliquely at 30° with respect to the normal line of the substrate is taken as 100%, the amount of specularly reflected light of light incident on the reflection control layer of the in-vehicle reflection control film from a direction obliquely at 30° with respect to the normal line of the reflection control film is 17.89 ~ 25 % and The reflected light amount at a reflection angle of 26° is 0.95 to 1.48%, and the reflected light amount at a reflection angle of 34° is 0.85 to 1.18%. The haze is 3 to 11%. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an in-vehicle reflection control film having optical properties suitable for in-vehicle use. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an in-vehicle reflection control film according to an embodiment. [Figure 2] FIG. 2 is a diagram for explaining the direction of reflection of light. DETAILED DESCRIPTION OF THE INVENTION

[0010] FIG. 1 is a cross-sectional view showing the configuration of an in-vehicle reflection control film according to an embodiment.

[0011] The reflection control film 10 for in-vehicle use according to this embodiment (hereinafter simply referred to as the “reflection control film”) includes a substrate 1 and a reflection control layer 5 laminated on one surface of the substrate 1.

[0012] The substrate 1 is a film that serves as the base of the reflection control film 10 and is made of a material that has excellent transparency to visible light. Materials that can be used to form the substrate 1 include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyacrylates such as polymethyl methacrylate, polyamides such as nylon 6 and nylon 66, polyimides, polyarylates, polycarbonates, triacetyl cellulose, polyacrylates, polyvinyl alcohol, polyvinyl chloride, cycloolefin copolymers, norbornene-containing resins, polyether sulfones, and transparent resins such as polysulfones, and inorganic glass. Among these, a film made of polyethylene terephthalate is preferably used. The thickness of the substrate 1 is not particularly limited, but is preferably 10 to 200 μm.

[0013] The surface of the substrate 1 may be subjected to a surface modification treatment in order to improve adhesion to the reflection control layer 5. Examples of surface modification treatments include alkali treatment, corona treatment, plasma treatment, sputtering treatment, application of a surfactant or a silane coupling agent, and Si vapor deposition.

[0014] In this embodiment, the reflection control layer 5 includes an antiglare layer 2 and a low reflection layer 3 in this order from the substrate 1 side.

[0015] The antiglare layer 2 is an optically functional layer that has fine irregularities on its surface and scatters external light with these irregularities to reduce glare from the external light. The antiglare layer 2 is formed by applying a coating liquid containing a binder resin and organic and / or inorganic fine particles to the substrate 1 and curing the coating film.

[0016] As the binder resin, an active energy ray-curable resin that is cured by irradiation with ionizing radiation or ultraviolet light can be used, and for example, a monofunctional, difunctional, trifunctional or higher functional (meth)acrylate monomer can be used. In this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryloyl" is a general term for both acryloyl and methacryloyl.

[0017] Examples of monofunctional (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isobornyl (meth)acrylate. acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphate (meth)acrylate, ethylene oxide-modified phosphate (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide-modified phenoxy (meth)acrylate, propylene oxide Oxide-modified phenoxy (meth)acrylate, nonylphenol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, propylene oxide-modified nonylphenol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, ) acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, 2-adamantane,Examples include adamantane derivative mono(meth)acrylates such as adamantyl acrylate having a monovalent mono(meth)acrylate derived from adamantanediol.

[0018] Examples of bifunctional (meth)acrylate compounds include di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and hydroxypivalic acid neopentyl glycol di(meth)acrylate.

[0019] Examples of trifunctional or higher (meth)acrylate compounds include tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethylisocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, etc., trifunctional (meth)acrylate compounds such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate. and polyfunctional (meth)acrylate compounds having three or more functional groups such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate, as well as polyfunctional (meth)acrylate compounds in which a portion of these (meth)acrylates is substituted with an alkyl group or ε-caprolactone.

[0020] Urethane (meth)acrylates can also be used as the active energy ray-curable resin. Examples of urethane (meth)acrylates include those obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer, and then reacting the resulting product with a (meth)acrylate monomer having a hydroxyl group.

[0021] Examples of urethane (meth)acrylates include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer.

[0022] The active energy ray-curable resins described above may be used alone or in combination of two or more. In addition, the active energy ray-curable resins described above may be in the form of a monomer in the coating liquid or a partially polymerized oligomer.

[0023] Furthermore, as the active energy ray-curable resin, in addition to the compounds having the above-mentioned radically polymerizable functional groups, monomers, oligomers, and prepolymers having cationically polymerizable functional groups such as epoxy groups, vinyl ether groups, and oxetane groups can be used alone or in combination. Examples of the monomer include unsaturated polyesters, epoxy acrylates, epoxy compounds such as tetramethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether, and various alicyclic epoxies, and oxetane compounds such as 3-ethyl-3-hydroxymethyloxetane, 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, and di[1-ethyl(3-oxetanyl)]methyl ether.

[0024] The resin material described above can be cured by irradiation with ultraviolet light, provided that a photopolymerization initiator is added. As the photopolymerization initiator, radical polymerization initiators such as acetophenones, benzophenones, thioxanthones, benzoin, and benzoin methyl ether, and cationic polymerization initiators such as aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, and metallocene compounds can be used alone or in combination.

[0025] The organic fine particles are a material that mainly forms fine irregularities on the surface of the antiglare layer 2 and provides the function of diffusing external light. Examples of organic fine particles that can be used include resin particles made of a light-transmitting resin material such as acrylic resin, polystyrene resin, styrene-(meth)acrylic acid ester copolymer, polyethylene resin, epoxy resin, silicone resin, polyvinylidene fluoride, and polyethylene fluoride resin. The refractive index of the resin particle material is preferably 1.40 to 1.75. Two or more types of resin particles with different materials (refractive indexes) may be mixed and used to adjust the refractive index and dispersion of the resin particles.

[0026] The inorganic fine particles added to the base resin of the optical functional layer are preferably nanoparticles with an average particle size of 10 to 200 nm, and the amount of inorganic fine particles added is preferably 0.1 to 5.0%.

[0027] The inorganic fine particles are primarily materials for controlling the sedimentation and aggregation of the organic fine particles in the antiglare layer 2. Examples of inorganic fine particles that can be used include silica fine particles, metal oxide fine particles, and various mineral fine particles. Examples of silica fine particles that can be used include colloidal silica and silica fine particles surface-modified with reactive functional groups such as (meth)acryloyl groups. Examples of metal oxide fine particles that can be used include alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titania, and zirconia. Examples of mineral fine particles that can be used include mica, synthetic mica, vermiculite, montmorillonite, iron-montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, ilealite, kanemite, layered titanic acid, smectite, and synthetic smectite. The mineral fine particles may be natural or synthetic (including substituted or derivative) materials, or a mixture of both may be used. Among mineral fine particles, layered organic clay is more preferred. Layered organic clay refers to a swelling clay in which organic onium ions have been introduced between its layers. The organic onium ions are not limited as long as they can be organized by utilizing the cation exchange properties of the swelling clay. When a layered organic clay mineral is used as the mineral microparticles, the above-mentioned synthetic smectite can be suitably used. Synthetic smectite has the function of increasing the viscosity of the coating liquid for forming the antiglare layer, suppressing the sedimentation of resin particles and inorganic microparticles, and adjusting the uneven shape of the surface of the optical functional layer.

[0028] A leveling agent may also be added to the coating solution for forming the antiglare layer. The leveling agent orients itself on the surface of the coating film during drying, thereby equalizing the surface tension of the coating film and reducing surface defects of the coating film.

[0029] Furthermore, the resin composition for forming the optical functional layer may contain an organic solvent as appropriate. Examples of the organic solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropyl alcohol, and isobutanol; ketones such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ketone alcohols such as diacetone alcohol; aromatic hydrocarbons such as benzene, toluene, and xylene; glycols such as ethylene glycol, propylene glycol, and hexylene glycol; glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, diethyl carbitol, and propylene glycol monomethyl ether; esters such as methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, and amyl acetate; ethers such as dimethyl ether and diethyl ether; N-methylpyrrolidone, dimethylformamide, and water. These organic solvents may be used singly or in combination.

[0030] The low-reflection layer 3 is an optically functional layer that reduces the surface reflection of the reflection control film 10 by canceling out light reflected on the surface of the low-reflection layer 3 through interference with light reflected on the interface between the low-reflection layer 3 and the anti-glare layer 2. The low-reflection layer 3 can be formed by applying a coating liquid containing a binder resin and low-refractive-index fine particles to the surface of the anti-glare layer 2 and curing the coating film.

[0031] The binder resin used to form the low reflective layer 3 is not particularly limited, and the compounds exemplified as the material for the antiglare layer 2 can be used.

[0032] Suitable low-refractive-index particles include, for example, particles of LiF, MgF, 3NaF·AlF, or AlF (all of which have a refractive index of 1.4), or Na3AlF6 (cryolite, refractive index of 1.33), as well as silica particles with internal voids. Silica particles with internal voids can have the refractive index of the voids (approximately 1) of air, making them ideal for lowering the refractive index of the low-reflection layer 3. Specifically, porous silica particles and silica particles with a shell structure can be used.

[0033] The average particle diameter of the low-refractive-index fine particles is preferably 1 nm or more and 100 nm or less. If the average particle diameter of the low-refractive-index fine particles exceeds 100 nm, light may be significantly reflected due to Rayleigh scattering, causing the low-reflection layer 3 to whiten and reducing the transparency of the reflection control film 10. On the other hand, if the average particle diameter of the low-refractive-index fine particles is less than 1 nm, problems such as particle non-uniformity in the low-reflection layer 3 may occur due to particle aggregation.

[0034] If necessary, a solvent or various additives may be added to the coating liquid for forming the low-reflection layer 3. As the solvent, for example, those exemplified as materials for the antiglare layer 2 may be used. Furthermore, as the additive, for example, an antifoaming agent, a leveling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a polymerization inhibitor, a photosensitizer, etc. may be used.

[0035] When the coating film of the coating liquid for forming the low-reflection layer is cured by ultraviolet irradiation, a photopolymerization initiator is added to the coating liquid. As the photopolymerization initiator, any of the materials exemplified for the antiglare layer 2 can be used.

[0036] The refractive index of the low-reflection layer 3 is preferably lower than that of the anti-glare layer 2 and falls within the range of 1.25 to 1.50. The lower the refractive index of the refractive index layer, the closer it is to the refractive index of air (refractive index = 1) and the easier it is to achieve low reflectance; however, since a large amount of low-refractive index material must be added, the mechanical strength may be reduced and the film may be more susceptible to scratches. On the other hand, if the refractive index of the low-reflection layer exceeds 1.50, the difference in refractive index with air becomes so large that the reflectance may increase.

[0037] The film thickness of the low-reflection layer 3 is preferably in the range of 5 nm to 1 μm in view of the properties as an optical interference layer, but it is more preferable in terms of thinning and suppressing reflectance to design the low-reflection layer 3 so that the optical film thickness obtained by multiplying the film thickness of the low-reflection layer 3 by the refractive index of the low-reflection layer 3 is approximately equal to 1 / 4 of the wavelength of visible light (the wavelength to be suppressed).

[0038] Fig. 2 is a diagram for explaining the direction of light reflection, and is a diagram of the in-vehicle display device as seen from above.

[0039] External light, such as light from nearby vehicles or streetlights, may penetrate the display surface of an in-vehicle display device. To reduce glare from reflected light and ensure visibility of the display surface of the in-vehicle display device, it is preferable to suppress reflection of external light on the display surface of the in-vehicle display device. Conventionally, optical films used in image display devices have been designed primarily to improve the visibility of displayed images and to minimize the reflection of incident light onto the display surface. Meanwhile, the external light image reflected on the display surface of the in-vehicle display device can be considered as information representing the situation around the vehicle. In particular, digital outer monitors and digital inner monitors, which are expected to see increased use in the future, are installed in or near the positions where optical mirrors were previously located, and are prone to receiving light from nearby vehicles or streetlights. Therefore, it would be useful if the reflected image could be used as information for understanding the surrounding situation. However, there has been no technical concept to ensure the visibility and distinctiveness of the reflected image on the display surface so that it can be used as a type of information, and the attributes required for optical films to ensure the visibility and distinctiveness of the reflected image have not been explored.

[0040] Image discrimination is important for utilizing an image reflected on the display surface of an in-vehicle display device as information about the vehicle's surroundings. Image discrimination refers to the ability of an occupant to distinguish between the displayed image displayed on the image display device and the reflected image and to recognize the nature of the reflected image. The inventors of the present application have found that if the external light image reflected on the display surface of the in-vehicle display device is too clear, it becomes difficult to distinguish between the displayed image and the external light image. However, if the reflection of the external light incident on the display surface is excessively suppressed, the visibility of the displayed image improves, but the external light image cannot be used to grasp the situation around the vehicle. Furthermore, while there are methods for reducing reflectance by diffusion, such as using an anti-glare film, it has been found that if the light diffusion on the display surface of the in-vehicle display device is too strong, the external light image becomes blurred, making it difficult to discern the nature of the reflected image.

[0041] In order to ensure the discernibility of images reflected on a display surface, we conducted a detailed study of the attributes (optical properties) required for optical films for in-vehicle applications. We found that it is effective to control the amount of specularly reflected light Lr of light Li incident at a 30° angle with respect to the normal to the display surface of the in-vehicle display device, and the amount of reflected light Lr' and Lr'' reflected at reflection angles of ±5° from this specularly reflected light (see Figure 2). More specifically, we assumed that in-vehicle display devices would be digital outer monitors or digital inner mirrors, which are installed in positions where external light is relatively likely to enter. By considering the installation position of the in-vehicle display device, the orientation of the display surface facing the driver, and the angle of the display surface relative to the longitudinal direction of the vehicle, we found that light is likely to enter the display surface of the in-vehicle display device at a 30° angle with respect to the normal. Furthermore, when light Li is incident at a 30° angle with respect to the normal to the display surface of the in-vehicle display device, the light that enters the eyes of a driver viewing the in-vehicle display device is light with a reflection angle of approximately ±5° centered on the specularly reflected light Lr. Although FIG. 2 assumes a vehicle in which the driver's seat is on the left side, the same applies when the driver's seat is on the right side.

[0042] Therefore, various studies were conducted focusing on the light intensity of specularly reflected light Lr (reflection angle: 30°), reflected light Lr' (reflection angle: 25°), and reflected light Lr'' (reflection angle: 35°), and it was found that the optical characteristics shown in the following items (1) to (3) are necessary to ensure the discernibility of reflected images. In the following, the reference light intensity (=100%) is defined as the light intensity of specularly reflected light of light incident on a substrate on which no reflection control layer is laminated, at an angle of 30° with respect to the normal to the substrate. (1) The amount of specularly reflected light Lr, which is light that is specularly reflected from light Li incident on a reflection control layer stacked on a substrate at an angle of 30° with respect to the normal line of the substrate, is 0 to 25% of the reference light amount, (2) For a reflection control layer laminated on a substrate, the amount of light reflected in directions at a reflection angle of ±5° of specularly reflected light Lr of light Li incident from a direction at an oblique angle of 30° with respect to the normal line of the substrate, i.e., the amount of reflected light Lr' reflected in a direction at an oblique angle of 25° with respect to the normal line of the substrate and the amount of reflected light Lr'' reflected in a direction at an angle of 35° with respect to the normal line, are both 0.3 to 2.0% of the reference light amount, (3) The haze of the reflection control film 10 is 3 to 11%. The haze is a value measured in accordance with JIS K7105.

[0043] By having these optical properties, the reflection control film 10 according to the present invention suppresses the reflection of incident light Li from a direction oblique at 30° to the normal to the display surface of the in-vehicle display device and moderately diffuses the incident light Li. As a result, the image of the incident light Li can be visually recognized by the driver as an image that is neither too clear nor too blurred. Therefore, the image of the incident light Li can be easily distinguished from the display image, making it easier to understand what the image is, and improving the identifiability of the reflected image.

[0044] The light intensity of reflected light Lr' and Lr'' is a parameter that mainly affects the blurring of the reflected image. If the light intensity of reflected light Lr' and Lr'' exceeds 2.0% of the reference light intensity, the reflected image will be too blurred, making it difficult to recognize what the reflected image is. On the other hand, if the light intensity of reflected light Lr' and Lr'' is less than 0.3% of the reference light intensity, the reflected image will be too clear, which may make it difficult to distinguish between the displayed image and the reflected image. In particular, if the light intensity of reflected light Lr' and Lr'' is less than 0.3% of the reference light intensity and the light intensity of specular reflected light Lr exceeds 25% of the reference light intensity, the reflected image will be too clear, making it difficult to distinguish between the displayed image and the reflected image. Furthermore, regardless of the light intensity of reflected light Lr' and Lr'', if the light intensity of specular reflected light Lr exceeds 25% of the reference light intensity, the specular reflected light will be too bright, which may reduce the visibility of the displayed image. Furthermore, haze is a parameter related to all of the light amounts of specularly reflected light Lr and reflected light Lr' and Lr''. If the haze of reflection control film 10 is less than 3%, the light diffusion property decreases and the light amounts of reflected light Lr' and Lr'' become smaller than the above-mentioned lower limit, which tends to make it difficult to blur the reflected image appropriately. On the other hand, if the haze of reflection control film 10 exceeds 11%, the light diffusion property increases and the light amounts of reflected light Lr' and Lr'' become larger than the above-mentioned upper limit, which tends to make the reflected image more blurred and difficult to recognize.

[0045] As explained above, reflection control film 10 according to the present invention is intended to utilize an external light image reflected on the display surface of an image display device as a type of information representing the situation around the vehicle, and by providing the optical properties described in items (1) to (3) above, it is possible to achieve both visibility of the displayed image and the ability to distinguish the external light image reflected on the display surface. Conventionally, there has been no idea of ​​utilizing the external light image reflected on the display surface of an image display device as information, and therefore the requirements for an optical film for utilizing the external light image as information have not been considered. However, reflection control film 10 according to the present invention has excellent distinguishability of the reflected image as described above, and is therefore extremely effective as an optical film that realizes an unprecedented idea.

[0046] Although reflection control film 10 according to the present invention is typically used as an optical film provided on the outermost surface of an image display device, there are no particular limitations on the position of the film in the laminate constituting the image display device, as long as the desired optical properties can be exhibited. Furthermore, one or more optically functional layers, such as an antistatic layer, an antifouling layer, an infrared absorbing layer, an ultraviolet absorbing layer, or a color correction layer, may be provided on reflection control layer 5 of reflection control film 10. [Example]

[0047] Hereinafter, examples in which the reflection control film according to the embodiment was specifically implemented will be described.

[0048] (Examples 1 to 5, Comparative Examples 9 to 11) A reflection control film was produced by laminating an antiglare layer and a low-reflection layer in this order on a substrate as an antireflection layer. A 40 μm-thick triacetyl cellulose film was used as the substrate. An antiglare layer-forming coating liquid was applied to the substrate, dried, and then polymerized and cured to form the antiglare layer. Then, a low-reflection layer-forming coating liquid was applied to the antiglare layer, dried, and then polymerized and cured to form the low-reflection layer.

[0049] A reflection control film was produced by laminating an antiglare layer on a substrate as an antireflection layer. A 40 μm-thick triacetyl cellulose film was used as the substrate. A coating solution for forming the antiglare layer was applied to the substrate, dried, and then polymerized and cured to form the antiglare layer. (Comparative Examples 1 to 8) A reflection control film was produced by laminating an antiglare layer on a substrate as an antireflection layer. A 40 μm-thick triacetyl cellulose film was used as the substrate. A coating solution for forming the antiglare layer was applied to the substrate, dried, and then polymerized and cured to form the antiglare layer.

[0050] (Comparative Example 12) A reflection control film was produced by laminating a hard coat layer and a low-reflection layer as an anti-reflection layer on a substrate. A 40 μm-thick triacetyl cellulose film was used as the substrate. A hard coat layer-forming coating liquid was applied to the substrate, dried, and then polymerized and cured to form the hard coat layer. A low-reflection layer-forming coating liquid was then applied to the hard coat layer, dried, and then polymerized and cured to form the low-reflection layer.

[0051] The compositions of the coating liquid for forming the antiglare layer, the coating liquid for forming the low-reflection layer, and the coating liquid for forming the hard coat layer used in the examples and comparative examples are shown in Tables 1 to 3. Each coating liquid was diluted with the solvent shown in Tables 1 to 3 to a concentration suitable for coating.

[0052] [Table 1]

[0053] [Table 2]

[0054] [Table 3]

[0055] [Haze value] The haze was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7105.

[0056] [Reflected light amount] Using a goniophotometer (GP-5, Murakami Color Research Laboratory Co., Ltd.), light similar to a D65 light source was irradiated from the anti-reflection layer side at an incident angle of 30°, and the intensity of the specular reflected light at a reflection angle of 30° and the reflected light at reflection angles of 23° to 37° was measured.

[0057] [evaluation] With the reflection-control films of Examples 1 to 5 and Comparative Examples 1 to 12 attached to the surface of a liquid crystal display device iPad (registered trademark) Air (4th generation), an image was displayed on the display screen under darkroom conditions (no ambient light incident), with the center of the liquid crystal display device positioned 100 cm above the floor and the evaluator's viewing position 50 cm horizontally in a straight line from the center of the display screen. In this state, fluorescent light was incident at an incident angle of 30°, and evaluation was performed under three conditions: the specular reflection direction and the specular reflection direction ±5°.

[0058] The evaluation criteria in Table 4 are as follows: the average score of the three conditions of the 15 evaluators is 4 to 5 points (〇), 3 to 4 points (△), and 1 to 3 points (×). " was rated as a pass. <Evaluation criteria> 5 points: The displayed image and the reflected fluorescent light image can be clearly recognized and distinguished. 4 points: The displayed image and the reflected fluorescent light image can be recognized and distinguished. 3 points: The displayed image and the reflected fluorescent light image can be recognized and distinguished, but the displayed image or the reflected fluorescent light image is partially blurred. 2 points: Either the displayed image or the reflected fluorescent light image cannot be recognized, or the displayed image and the reflected fluorescent light image cannot be distinguished. Score 1: Neither the displayed image nor the reflected fluorescent light image can be recognized or distinguished.

[0059] Table 4 summarizes the layer structure, haze, reflected light intensity (amount of reflected light at reflection angles of 30°, 25°, and 35°), and image discrimination evaluations of the reflection control films according to Examples 1 to 5 and Comparative Examples 1 to 12. In Table 3, "AGLR" in the layer structure indicates that the antireflection layer is composed of an antiglare layer and a low-reflection layer, "AG" indicates that the antireflection layer is composed of an antiglare layer, and "HCLR" indicates that the antireflection layer is composed of a low-reflection layer on a hard coat layer. The unit of reflected light intensity is "%," and the value of reflected light intensity is expressed as 100% when the intensity of specularly reflected light is incident on a substrate not laminated with an antireflection layer and light approximating a D65 light source at an incident angle of 30°.

[0060] [Table 4]

[0061] The reflection control films according to Examples 1 to 5 had a haze of 3 to 11%, which moderately diffused incident light, and the low-reflection layer suppressed surface reflection, with the amount of specularly reflected light being 25% or less and the intensity of reflected light at reflection angles of 25° and 35° being within the range of 0.3 to 2.0%. It was confirmed that the reflection control films that satisfied these conditions made it possible to distinguish between the displayed image and the reflected image of the fluorescent lamp, and to recognize what the reflected image was.

[0062] The reflection control films according to Comparative Examples 1 to 5 had a haze within the range of 3 to 11%, but because they did not have a low-reflection layer, the amount of specular reflected light exceeded 25%, and the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° also exceeded 2.0%. Because the amount of specular reflected light was high, it was possible to recognize the image of the fluorescent light reflected, but the high amount of specular reflected light made it difficult to distinguish between the displayed image and the reflected image, resulting in lower ratings than Examples 1 to 5.

[0063] The reflection control films according to Comparative Examples 6 and 7 did not have a low-reflection layer, but because their haze was high, the diffusion of incident light was high, and the amount of specularly reflected light was suppressed to a level lower than in Comparative Examples 1 to 5. This made it possible to distinguish between the displayed image and the reflected image. However, while the amount of specularly reflected light was suppressed to a certain extent, the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° was close to 5.0%, so the image of the reflected fluorescent light was relatively dark and blurred, making it impossible to identify what the reflected image was.

[0064] The reflection control film of Comparative Example 8 did not have a low-reflection layer and the amount of reflected light was not suppressed, so the amount of specularly reflected light was too high, making it impossible to distinguish between the displayed image and the image of the fluorescent light reflected in it.

[0065] In the reflection control films of Comparative Examples 9 and 10, the reflection control layer was composed of an antiglare layer and a low-reflection layer, as in Examples 1 to 5, but the high haze increased the diffusivity of incident light, and the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° exceeded 2.0%. While the amount of specularly reflected light was suppressed to 25% or less, the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° increased, so the reflected image was relatively dark and blurred, making it impossible to identify the image.

[0066] The reflection control films according to Comparative Examples 11 and 12 had small haze, so that the amount of reflected light at a reflection angle of 25° and at a reflection angle of 35° was less than 0.3%. As a result, the reflected image became clear, and it was impossible to distinguish between the displayed image and the reflected image of the fluorescent lamp.

[0067] From the above, it was confirmed that the reflection control film of the present invention can distinguish between the displayed image and the reflected image of the image display device when light is incident at an angle of 30° to the normal to the display surface of the image display device, and that it is possible to recognize what the reflected image is.

[0068] Tables 5 to 8 show the haze, reflected light amount (amount of reflected light at reflection angles of 23°, 24°, 25°, 26°, 27°, 30°, 33°, 34°, 35°, 36°, and 37°), the sum of the reflected light amounts at reflection angles of 23° and 24°, the sum of the reflected light amounts at reflection angles of 26° and 27°, and the sum of the reflected light amounts at reflection angles of 23° and 24° and the sum of the reflected light amounts at reflection angles of 25° for the reflection control films of Examples 1 to 5 and Comparative Examples 1 to 12. The evaluation of image discrimination is summarized below. The unit of reflected light intensity is "%", and the value of reflected light intensity is expressed as 100% when the intensity of specular reflected light when D65 approximation light is incident on a substrate without an anti-reflection layer at an incident angle of 30°. The value of the sum of the reflected light intensity at reflection angles of 26° and 27° divided by the amount of reflected light at a reflection angle of 25°, the sum of the reflected light intensity at reflection angles of 33° and 34°, the sum of the reflected light intensity at reflection angles of 36° and 37° divided by the amount of reflected light at a reflection angle of 35°. The units for the value obtained by dividing the sum of the reflected light amounts at reflection angles of 23° and 24° by the amount of reflected light at a reflection angle of 25°, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25°, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35°, and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 36° and 37° by the amount of reflected light at a reflection angle of 35° are dimensionless. Haze and evaluation were the same as those described in Table 4.

[0069] [Table 5]

[0070] [Table 6]

[0071] [Table 7]

[0072] [Table 8]

[0073] The reflection control films according to Examples 1 to 5 had a haze of 3 to 11%, which moderately diffused incident light, and the low-reflection layer suppressed surface reflection, resulting in a specular reflection of 25% or less and a reflected light intensity of 0.3 to 2.0% at reflection angles of 25° and 35°. Furthermore, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the reflected light amount at a reflection angle of 25° was within a range of 8.30 to 9.50. The value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the reflected light amount at a reflection angle of 35° was within a range of 6.89 to 7.87. It was confirmed that the reflection control films satisfying these conditions enabled the display image to be distinguished from the reflected image of a fluorescent lamp, and allowed the viewer to recognize the nature of the reflected image.

[0074] The reflection control films according to Comparative Examples 1 to 5 had a haze within the range of 3 to 11%, but because they did not have a low refractive index layer, the amount of specularly reflected light exceeded 25%, and the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° also exceeded 2.0%. Furthermore, the value obtained by dividing the sum of the amount of reflected light at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25° was within the range of 5.77 to 6.20. The value obtained by dividing the sum of the amount of reflected light at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35° was within the range of 5.36 to 5.62. Because the amount of specularly reflected light was high, it was possible to identify the reflected image, but the high amount of specular reflected light made it difficult to distinguish between the displayed image and the reflected image, resulting in lower ratings than Examples 1 to 5.

[0075] The reflection control films of Comparative Examples 6 and 7 did not have a low refractive index layer, but their high haze increased the diffusion of incident light, and the amount of specularly reflected light was reduced compared to Comparative Examples 1 to 5. This made it possible to distinguish between the displayed image and the reflected image. However, while the amount of specularly reflected light was somewhat reduced, the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° was close to 5.0%, making the reflected image relatively dark and blurred, making it difficult to identify the image. Furthermore, the sum of the reflected light amounts at reflection angles of 26° and 27° divided by the reflected light amount at a reflection angle of 25° was 4.74 in Comparative Example 6 and 3.73 in Comparative Example 7. The sum of the reflected light amounts at reflection angles of 33° and 34° divided by the reflected light amount at a reflection angle of 35° was 4.78 in Comparative Example 6 and 3.63 in Comparative Example 7.

[0076] The reflection control film of Comparative Example 8 did not have a low refractive index layer and the amount of reflected light was not suppressed, so the amount of specularly reflected light was too high, making it impossible to distinguish between the displayed image and the reflected image. Furthermore, the sum of the reflected light amounts at reflection angles of 26° and 27° divided by the reflected light amount at a reflection angle of 25° was 17.12. The sum of the reflected light amounts at reflection angles of 33° and 34° divided by the reflected light amount at a reflection angle of 35° was 11.91.

[0077] The reflection control films of Comparative Examples 9 and 10, like Examples 1 to 5, had a reflection control layer composed of an antiglare layer and a low refractive index layer. However, due to the high haze, the diffusion of incident light was increased, and the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° exceeded 2.0%. While the amount of specularly reflected light was suppressed to 25% or less, the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° increased. As a result, the reflected image was relatively dark and blurred, making it impossible to identify the image. Furthermore, the sum of the reflected light amounts at reflection angles of 26° and 27° divided by the reflected light amount at a reflection angle of 25° was 5.11 in Comparative Example 9 and 4.41 in Comparative Example 10. The sum of the reflected light amounts at reflection angles of 33° and 34° divided by the reflected light amount at a reflection angle of 35° was 5.08 in Comparative Example 9 and 4.30 in Comparative Example 10.

[0078] The reflection control films of Comparative Examples 11 and 12 had low haze, so the amount of reflected light at a reflection angle of 25° and a reflection angle of 35° was less than 0.3%. As a result, the reflected image was clear, and it was impossible to distinguish between the displayed image and the reflected image. Furthermore, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the reflected light amount at a reflection angle of 25° was 18.19 for Comparative Example 11 and 97.00 for Comparative Example 12. The value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the reflected light amount at a reflection angle of 35° was 13.65 for Comparative Example 11 and 5.00 for Comparative Example 12.

[0079] The value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25° is larger than the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35°. This is because the closer the reflection angle is to 0°, the more susceptible the light is to the influence of incident light. Furthermore, in Examples 1 to 5, the smaller the haze, the smaller the value obtained by dividing the sum of the reflected light amounts at reflection angles of 23° and 24° by the amount of reflected light at a reflection angle of 25°, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25°, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35°, and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 36° and 37° by the amount of reflected light at a reflection angle of 35°. Furthermore, when Examples 1 to 5 are compared with Comparative Examples 1 to 5 in which a low refractive index layer is not formed, the lower the reflectance, the smaller the value obtained by dividing the sum of the reflected light amounts at reflection angles of 23° and 24° by the amount of reflected light at a reflection angle of 25°, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25°, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35°, and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 36° and 37° by the amount of reflected light at a reflection angle of 35°. Therefore, reducing the haze and reducing the reflectance contribute to reducing the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25°, etc.

[0080] There were no significant differences between the Examples and Comparative Examples in the value obtained by dividing the sum of the reflected light amounts at reflection angles of 23° and 24° by the amount of reflected light at a reflection angle of 25°, and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 36° and 37° by the amount of reflected light at a reflection angle of 35°. On the other hand, there were significant differences between the Examples and Comparative Examples in the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25°, and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35°. In particular, in Examples 1 to 5, the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25° and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35° were 6.89 to 9.50, and therefore the evaluation results were superior to those of Comparative Examples 1 to 12. This means that if the relationship between the amount of reflected light at reflection angles of 25° to 7° and the amount of reflected light at reflection angles of 33° to 35° meets the above conditions, it is believed that this will be advantageous for distinguishing between the displayed image and the reflected image of the fluorescent light when the human eye sees light incident at an angle, and for recognizing what the reflected image is.

[0081] Since the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the amount of reflected light at a reflection angle of 25° and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the amount of reflected light at a reflection angle of 35° are within the above ranges, it has been confirmed that the reflection control film of the present invention can distinguish between the displayed image and the reflected image of the image display device when light is incident at an angle of 30° to the normal to the display surface of the image display device, and that it is possible to recognize what the reflected image is. [Industrial Applicability]

[0082] The reflection control film according to the present invention can be used as an optical film for use in image display devices, and is particularly suitable for use in in-vehicle display devices. [Explanation of symbols]

[0083] 1 Base material 2 Anti-glare layer 3 Low reflective layer 5 Reflection Control Layer 10. Reflection control film for automobiles

Claims

1. A reflection control film for vehicle installation comprising a substrate and a reflection control layer laminated on the substrate, the reflection control layer comprises an antiglare layer laminated on the substrate and a low refractive index layer laminated on the antiglare layer without any other layer therebetween; When the amount of specularly reflected light of light incident on a substrate not laminated with a reflection control layer from a direction obliquely at 30° with respect to the normal to the substrate is taken as 100%, the amount of specularly reflected light of light incident on the reflection control layer of the in-vehicle reflection control film from a direction obliquely at 30° with respect to the normal to the reflection control film is 17.89 to 25%, the amount of reflected light at a reflection angle of 26° is 0.95 to 1.48%, and the amount of reflected light at a reflection angle of 34° is 0.85 to 1.18%; An in-vehicle reflection control film having a haze of 3 to 11%.

2. 2. The reflection control film for vehicle installation according to claim 1, wherein the value obtained by dividing the sum of the reflected light amounts at reflection angles of 26° and 27° by the reflected light amount at a reflection angle of 25° and the value obtained by dividing the sum of the reflected light amounts at reflection angles of 33° and 34° by the reflected light amount at a reflection angle of 35° are 6.89 to 9.50.

Images