Laminated film and image display device

Abstract

To provide a laminated film that provide design having high luminance and color unevenness suppressed.SOLUTION: A laminated film has: a decorative layer which has a first principal surface and a second principal surface, the first principal surface having an uneven structure; a low-refractive index layer provided on the first principal surface of the decorative layer; and a high-refractive index layer provided on the low-refractive index layer on an opposite side from the decorative layer. In one embodiment, the low-refractive index layer has a refractive index of 1.30 or less and a thickness of 0.3 μm or larger, and / or the high-refractive index layer has a refractive index of 1.60 to 2.20 and a thickness of 0.3 μm or larger.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated film and an image display device. [Background technology]

[0002] Decorative films are used as a means of improving the design of various products. For example, a technique has been proposed in which a decorative film is attached to a cover case for housing a smartphone, tablet terminal, or the like and / or to a glass panel constituting the back surface (the surface not involved in image display) of an image display device to impart design to the image display device itself. For example, a decorative film having a concave-convex layer and a low refractive index layer is known. However, conventional decorative films can cause problems such as insufficient brightness of the imparted design and / or uneven color in the imparted design. Therefore, a decorative film that can further enhance the commercial value of image display devices is desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-57471 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-47594 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a laminated film that can realize a design with high brightness and reduced color unevenness. [Means for solving the problem]

[0005] [1] A laminated film according to an embodiment of the present invention has a first main surface and a second main surface, and the first main surface has a concave-convex structure. unevennesslayer; unevenness a low refractive index layer provided on a first main surface of the layer; unevenness and a high refractive index layer disposed on the opposite side of the layer. [2] In the above [1], the refractive index of the low refractive index layer is 1.30 or less, and the thickness is 0.3 μm or more. [3] In the above [1] or [2], the refractive index of the high refractive index layer is 1.60 to 2.20, and the thickness is 0.3 μm or more. [4] In any of [1] to [3] above, unevenness The layer has a light redirecting function. [5] In any of [1] to [4] above, unevenness When the height of the projections and recesses in the projection-recess structure of the layer is H and the pitch of the projections and recesses is P, P / H is 1.5 or more. [6] In any one of the above [1] to [5], the laminated film further has a colored layer on the side of the high refractive index layer opposite to the low refractive index layer. [7] According to another aspect of the present invention, there is provided an image display device having an image display surface and a back surface, and a laminate film according to any one of [1] to [6] above disposed on the back surface. [Effects of the Invention]

[0006] According to an embodiment of the present invention, a laminated film can be provided that can realize a design with high brightness and reduced color unevenness. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a laminated film according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of a laminated film according to another embodiment of the present invention. [Figure 3] FIG. 2 is a schematic cross-sectional view illustrating a usage form of the laminated film of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. Note that the drawings are drawn schematically or conceptually to facilitate visibility and understanding, and the length, width, shape, size, ratio, direction, number, etc. may differ from the actual ones, and there may be no correspondence between the drawings.

[0009] A. Overall structure of laminated film 1 is a schematic cross-sectional view of a laminated film according to one embodiment of the present invention. The illustrated laminated film 100 is unevenness It has a layer 10, a low refractive index layer 20 and a high refractive index layer 30. unevenness The layer 10 has a first major surface 10a and a second major surface 10b, and the first major surface 10a has an uneven structure. unevenness The high refractive index layer 30 is provided on the first major surface 10a of the low refractive index layer 20. unevenness It is provided on the opposite side to layer 10. unevenness By providing a combination of the low refractive index layer 20 and the high refractive index layer 30 in such a positional relationship with respect to the layer 10, a laminated film can be obtained that can realize a design with high brightness and suppressed color unevenness. The low refractive index layer 20 and the high refractive index layer 30 are typically arranged as shown in the example in the figure, in view of the relationship between their thickness and the height (depth) of the uneven structure. unevenness On the other hand, either the low refractive index layer 20 or the high refractive index layer 30 fills in the recesses of the recessed and projected structure, unevenness The side opposite the layer may be a flat surface.

[0010] In an embodiment of the present invention, unevenness Layer 10 typically has the function of redirecting light. unevenness The layer 10 can realize a design according to the purpose by controlling the uneven structure and, for example, controlling the transmission, reflection, diffraction, scattering, and diffusion of light in combination. unevenness The laminated film includes the layers: unevennessDepending on the type of layer, the following effects can be achieved: (1) the surface of various products can be decorated to improve their design; (2) the color of the surface of various products can be changed depending on the viewing angle; and (3) different images, characters, etc. can be displayed on the surface of various products depending on the viewing angle. Therefore, the laminate film according to the embodiment of the present invention can also be called a decorative film, an optical laminate, etc. unevenness Depending on the specific configuration, layer 10 may exhibit a design on one or both of the first and second principal surfaces. unevenness The layer 10 preferably has a design that appears at least on the side indicated by the arrow in FIG. unevenness Any appropriate configuration can be adopted for the layer as long as it has the above-mentioned functions. unevenness The specific configuration of the layers will be explained in Section B below.

[0011] The low refractive index layer 20 typically has a refractive index of 1.30 or less. By providing such a low refractive index layer at a predetermined position, unevenness The low refractive index layer 20 can realize an appropriate reflection at the interface with the low refractive index layer 20. As a result, the reflectance of the laminated film can be increased, and therefore, a design with high brightness can be realized. unevennessThe low refractive index layer 20 may be formed on the first main surface 10a of the layer 10 via an adhesive layer, or may be formed directly on the first main surface. Preferably, the low refractive index layer is formed directly on the first main surface. This configuration avoids adverse effects due to the refractive index of the adhesive layer. Such direct formation can be achieved, for example, by coating or printing a low refractive index layer-forming liquid, as described below. Furthermore, the thickness of the low refractive index layer 20 is preferably 0.3 μm or more. When the thickness of the low refractive index layer is within this range, the effects of the embodiment of the present invention can be more pronounced. Specifically, hue change in the laminated film can be suppressed, and as a result, color unevenness in the resulting design can be suppressed. This is presumably because thin film interference between the low refractive index layer and the high refractive index layer is suppressed. The specific configuration of the low refractive index layer will be described in Section C below. The adhesive layer may be composed of a pressure-sensitive adhesive or an adhesive. Since the adhesive layer (or the adhesive or pressure-sensitive adhesive constituting the adhesive layer) may have a configuration well known in the art, detailed description will be omitted. Hereinafter, unless otherwise specified, the same applies to other "adhesive layers."

[0012] The high refractive index layer 30 typically has a refractive index of 1.60 to 2.20. By providing such a high refractive index layer at a predetermined position, the synergistic effect with the effect of providing a low refractive index layer can achieve even better reflection in the laminate film. As a result, a design with higher brightness can be realized than when a low refractive index layer is provided alone. The high refractive index layer 30 may be formed on the low refractive index layer 20 via an adhesive layer, or may be formed directly on the low refractive index layer 20. Preferably, the high refractive index layer is formed directly on the low refractive index layer. This configuration can avoid adverse effects caused by the refractive index of the adhesive layer. Such direct formation can be achieved, for example, by coating or printing a high refractive index layer-forming liquid, as described below. Furthermore, the thickness of the high refractive index layer 30 is preferably 0.3 μm or more. When the thickness of the high refractive index layer is within this range, the effects of the present invention can be more pronounced, similar to when the thickness of the low refractive index layer is set to a predetermined value or more. Specifically, hue change in the laminate film can be suppressed, and as a result, color unevenness in the resulting design can be suppressed. In one embodiment, the high refractive index layer is thicker than the low refractive index layer. In this case, the difference between the thicknesses of the high refractive index layer and the low refractive index layer may be, for example, 0.2 μm to 3.0 μm, or may be, for example, 1.0 μm to 2.0 μm. The specific configuration of the high refractive index layer will be described in Section D below.

[0013] FIG. 2 is a schematic cross-sectional view of a laminate film according to another embodiment of the present invention. The laminate film 101 in the illustrated example further includes a colored layer 40 on the side of the high refractive index layer 30 opposite the low refractive index layer 20. By providing the colored layer 40, the design that appears due to reflection can be made clearer. The colored layer 40 may be formed on the high refractive index layer 30 via an adhesive layer, or may be formed directly on the high refractive index layer 30. In the illustrated example, the colored layer 40 is formed on the high refractive index layer 30 via an adhesive layer 50. The adhesive layer in this embodiment may typically be a pressure-sensitive adhesive layer. The specific configuration of the colored layer will be described in Section E below.

[0014] If necessary, a pressure-sensitive adhesive layer (not shown) may be provided as the outermost layer on the high refractive index layer 30 side. By providing such a pressure-sensitive adhesive layer, the laminate film can be attached to an image display device. In practice, it is preferable that a release liner (not shown) is temporarily attached to the laminate film until it is used. Temporarily attaching the release liner protects the pressure-sensitive adhesive layer and enables the laminate film to be formed into a roll.

[0015] The components of the laminated film will be described in detail below.

[0016] B. unevenness layer In an embodiment of the present invention, unevenness Layer 10 typically has the function of redirecting light as described above. unevenness Specific examples of the layer include a shaped film, a reflective hologram film, a microlens array film, a prism film, and a lenticular lens. Although a reflective hologram film and the like can also be included in the shaped film, in this specification, for convenience, the shaped film and the reflective hologram film and the like are both referred to.

[0017] As the shaped film, any appropriate configuration can be adopted depending on the purpose. Examples of the uneven structure of the shaped film include a structure in which rectangular parallelepiped unevenness is arranged in a checkerboard pattern in a plan view, a structure in which the recesses have inclined surfaces at different angles as shown in Figure 1 (vertical surfaces and inclined surfaces in the illustrated example), a structure in which the recesses are in the shape of a quadrangular pyramid, a structure in which the recesses are in the shape of a truncated quadrangular pyramid, a structure in which the recesses are in the shape of a dome, an uneven shape having convex portions with a rectangular cross section extending in one direction at regular intervals (striped shape in a plan view, so-called line and space), an uneven shape having convex portions with a wavy cross section extending in one direction at regular intervals, an uneven shape having convex portions with a triangular cross section extending in one direction at regular intervals, and combinations thereof.

[0018] The shaped film can be produced by any appropriate method. For example, the shaped film can be produced by transferring the relief structure of a mold to a soft resin sheet. Examples of soft resin sheets include semi-cured thermosetting or active energy ray curable resin sheets and thermoplastic resin sheets softened by heating. After the relief structure is transferred to the thermosetting or active energy ray curable resin sheet, it is cured by heating or irradiation with active energy rays (typically visible light or ultraviolet light), and the relief structure is fixed. After the relief structure is transferred to the thermoplastic resin sheet, it is solidified by cooling, and the relief structure is fixed.

[0019] The reflection hologram film may have any suitable configuration depending on the purpose. The uneven shape of the reflection hologram film may be any suitable fine uneven shape capable of exhibiting functions such as light diffusion, light scattering, light reflection, and light diffraction. Typical examples include a Fourier transform structure, a lenticular lens, a light diffraction pattern, and a moth-eye structure. Furthermore, uneven shapes such as hairline patterns, matte patterns, line patterns, and interference patterns may be used, which do not have a light diffraction function but can exhibit unique brilliance. In one embodiment, the reflection hologram film can convert reflected light into diffracted light.

[0020] A microlens array film typically has a flat base and a lens section provided on one surface of the base. The lens section is composed of a plurality of lenses. The lenses constituting the lens section are typically convex lenses, and may have, for example, a dome shape. The lenses may be arranged in a matrix, in a predetermined pattern (for example, stripes), or randomly.

[0021] A prism film typically has a flat base portion and a prism portion. The prism portion typically comprises an array of unit prisms that extend in one direction and have a triangular cross section that is convex on the side opposite the base portion. The extension direction of the unit prisms (the ridge direction of the unit prisms) can be appropriately set depending on the purpose.

[0022] A lenticular lens typically has a plurality of convex cylindrical lenses, each having a semicircular cross section, arranged in parallel (that is, in a stripe pattern).

[0023] In one embodiment, unevenness When the height of the projections and recesses in the projection-recess structure of layer 10 is H and the pitch of the projections and recesses is P, P / H is preferably 1.5 or more, more preferably 2.0 or more, even more preferably 3.0 or more, and particularly preferably 5.0 or more. On the other hand, P / H is preferably 100 or less, more preferably 70 or less, even more preferably 60 or less, and particularly preferably 50 or less. unevenness If the P / H of the concave-convex structure of the layer is within this range, the effects of the embodiment of the present invention can be more pronounced. If the P / H is too small, the low refractive index layer may not be properly formed. The upper limit of the P / H can be determined depending on the desired design. In this specification, the "height of the concave-convex structure" refers to the distance from a peak (or apex) to a valley (or flat end) in one concave-convex structure, and if the concave-convex structure is irregular, it refers to the average distance from a peak (or apex) to a valley (or flat end) in each concave-convex structure. Furthermore, the "pitch of the concave-convex structure" refers to the distance from adjacent peaks (or apexes) to each other, and if the concave-convex structure is irregular, it refers to the average distance from adjacent peaks (or apexes) to each other.

[0024] The pitch P of the irregularities and the height H of the irregularities can be appropriately set as long as the desired P / H is obtained. The pitch P is preferably 10 μm to 500 μm, more preferably 30 μm to 200 μm, and even more preferably 50 μm to 100 μm. The height H is preferably 0.1 μm to 100 μm, more preferably 1 μm to 50 μm, and even more preferably 2 μm to 20 μm.

[0025] unevennessThe thickness of the layer (the maximum thickness corresponding to the convex portions) is preferably 50 μm to 3 mm (3000 μm), and more preferably 100 μm to 1 mm (1000 μm).

[0026] C. Low refractive index layer The refractive index of the low refractive index layer 20 is typically 1.30 or less, as described above, with the lower limit exceeding 1.00. The refractive index of the low refractive index layer 20 is preferably 1.13 to 1.28, more preferably 1.14 to 1.27, even more preferably 1.15 to 1.26, and particularly preferably 1.16 to 1.25. When the refractive index of the low refractive index layer is within this range, unevenness By providing a layer on the first main surface (concave and convex surface) of the layer unevenness The refractive index is measured at a wavelength of 550 nm unless otherwise specified. The refractive index is a value measured, for example, by the method described in the Examples below.

[0027] The total light transmittance of the low refractive index layer 20 is preferably 85% to 99%, more preferably 87% to 98%, and even more preferably 89% to 97%. unevenness By providing the layer on the first main surface (concave and convex surface), for example, excellent transparency can be achieved for the entire laminate film. As a result, for example, when the laminate film is applied to various products, the visibility of the design that can be expressed can be ensured. The total light transmittance can be measured, for example, using a haze meter described below.

[0028] The haze of the low refractive index layer 20 is preferably less than 5%, more preferably less than 3%. On the other hand, the haze is, for example, 0.1% or more, and may be 0.2% or more. unevennessBy providing the layer on the first main surface (concave and convex surface), for example, it is possible to achieve excellent transparency for the entire laminate film. As a result, for example, when the laminate film is applied to various products, it is possible to ensure the visibility of the design that can be expressed. For example, the haze can be calculated from the following formula using the value measured with a haze meter (for example, "HM-150" manufactured by Murakami Color Research Laboratory Co., Ltd.). Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] x 100 (%)

[0029] As described above, the thickness of the low refractive index layer 20 is preferably 0.3 μm or more, more preferably 1.0 μm or more, even more preferably 1.2 μm or more, particularly preferably 1.5 μm or more, and particularly preferably 1.8 μm or more. The thickness of the low refractive index layer may be, for example, 2.2 μm or more, or may be, for example, 2.5 μm or more, or may be, for example, 2.8 μm or more. On the other hand, the thickness of the low refractive index layer may be, for example, 20 μm or less, or may be, for example, 10 μm or less, or may be, for example, 8 μm or less, or may be, for example, 5 μm or less. If the thickness of the low refractive index layer is within this range, as described above, hue change in the laminate film can be suppressed, and as a result, color unevenness in the resulting design can be suppressed.

[0030] The low-refractive index layer may have any suitable structure that can achieve the desired properties. Examples of materials that can be used for the low-refractive index layer include those described in International Publication No. 2004 / 113966, Japanese Patent Application Laid-Open No. 2013-254183, and Japanese Patent Application Laid-Open No. 2012-189802. Representative examples of materials that can be used for the low-refractive index layer include silicon compounds. Examples of silicon compounds include silica-based compounds; hydrolyzable silanes and their partial hydrolyzates and dehydration condensates; silicon compounds containing silanol groups; and activated silica obtained by contacting silicate with acid or ion-exchange resin. Examples of materials that can be used for the low-refractive index layer include organic polymers; polymerizable monomers (e.g., (meth)acrylic monomers and styrene-based monomers); and curable resins (e.g., (meth)acrylic resins, fluorine-containing resins, and urethane resins). These materials may be used alone or in combination.

[0031] In one embodiment, the low refractive index layer may contain spaces such as pores and gaps therein. In this case, the porosity of the low refractive index layer is preferably 20 to 60 volume %, more preferably 25 to 55 volume %, even more preferably 30 to 50 volume %, and particularly preferably 35 to 45 volume %. Such a porosity allows the refractive index of the low refractive index layer to be within an appropriate range and ensures strength. Here, the porosity is a value calculated from the refractive index measured with an ellipsometer using the Lorentz-Lorenz formula.

[0032] The size of the pores that can be contained in the low refractive index layer can be adjusted to a desired size depending on the purpose and application. The size of the pores that can be contained in the low refractive index layer is, for example, 2 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, the size of the pores that can be contained in the low refractive index layer is, for example, 500 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. Note that the size of the pores refers to the diameter of the major axis of the pores, out of the diameter of the major axis and the diameter of the minor axis.

[0033] The pore size can be quantified by the BET test method. In one embodiment, 0.1 g of a measurement sample (e.g., a formed low refractive index layer) is placed in the capillary of a specific surface area measurement device (e.g., "ASAP2020" manufactured by Micromeritics), and then the sample is dried under reduced pressure at room temperature for 24 hours to remove gases contained in the measurement sample. Then, nitrogen gas is adsorbed onto the measurement sample, and an adsorption isotherm is drawn to determine the pore distribution. This allows the pore size to be evaluated.

[0034] Examples of the low refractive index layer having a space therein include a porous layer made of a porous material and / or a layer containing an air layer at least in part. The low refractive index layer typically contains aerogel and / or particles (which may be hollow fine particles and / or porous particles, for example). The low refractive index layer is preferably a nanoporous layer (specifically, a layer in which 90% or more of the pores have a diameter of 10 -1 nm~10 3 The porous layer may be in the range of 100 nm.

[0035] Any suitable particles may be used as the particles. The particles are typically made of a silica-based compound. Examples of particle shapes include spherical, plate-like, needle-like, string-like, and bunch-of-grapes shapes. Examples of string-like particles include particles in which a plurality of spherical, plate-like, or needle-like particles are strung together like beads, short fiber-like particles (e.g., the short fiber-like particles described in JP 2001-188104 A), and combinations thereof. The string-like particles may be linear or branched. Examples of bunch-of-grapes-like particles include particles in which a plurality of spherical, plate-like, and needle-like particles are aggregated to form a bunch of grapes. The particle shape can be confirmed, for example, by observation using a transmission electron microscope.

[0036] An example of a low refractive index layer is a structure composed of one or more types of structural units that form a fine void structure, and these structural units are bonded together (for example, chemically bonded via catalytic action). Examples of the shape of the structural units include particulate, fibrous, rod-like, and flat-plate-like. The structural units may have only one shape, or may have two or more shapes in combination.

[0037] A specific example of a low refractive index layer is a porous layer composed of a porous body in which particles having micropores (hereinafter referred to as microporous particles) are chemically bonded to each other. Such a porous layer can be obtained, for example, by chemically bonding the microporous particles to each other. The shape of the microporous particles is not particularly limited and may be, for example, spherical or other shapes. Furthermore, the microporous particles may be, for example, sol-gel beaded particles, nanoparticles (e.g., hollow nanosilica nanoballoon particles), nanofibers, etc. Representative microporous particles include inorganic substances. Specific examples of inorganic substances include silicon (Si), magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), and zirconium (Zr). These may be used alone or in combination of two or more. In one embodiment, the microporous particles are, for example, microporous particles of a silicon compound, and the porous body is, for example, a silicone porous body. The microporous particles of a silicon compound include, for example, a pulverized gel silica compound.

[0038] Another example of a low refractive index layer is a layer containing a fibrous material such as nanofibers, in which spaces are formed by the entanglement of the fibrous material. Further examples of a low refractive index layer include a layer formed using hollow nanoparticles or nanoclay, or a layer formed using hollow nanoballoons or magnesium fluoride. The low refractive index layer may be composed of a single constituent material or multiple constituent materials. The low refractive index layer may be composed of a single form of the above examples, or multiple forms of the above examples.

[0039] The porous layer may have, for example, an open-cell structure, in which the pores are interconnected. An open-cell structure refers to a porous body (e.g., a porous silicone body) in which the pores are interconnected three-dimensionally, and can also be described as a state in which the pore spaces are interconnected. The open-cell structure of the porous layer can enhance porosity. It is difficult to form an open-cell structure using closed-cell particles with individual pores, such as hollow particles (e.g., hollow silica). However, when using silica sol particles (a pulverized product of a gel-like silicon compound that forms a sol), the silica sol particles can have a three-dimensional dendritic structure. The dendritic particles settle and deposit in a coating film (a coating film of a sol containing a pulverized product of a gel-like silicon compound), thereby easily forming an open-cell structure. The porous layer preferably has a monolithic structure in which the open-cell structure includes a distribution of multiple pores. The monolithic structure refers to, for example, a hierarchical structure including a structure with nano-sized pores and an open-cell structure in which nano-sized pores are aggregated. The monolithic structure, for example, can provide membrane strength through fine pores while providing high porosity through a coarse open-cell structure, thereby achieving both membrane strength and high porosity.

[0040] For example, the monolith structure can be formed by controlling the pore distribution of the resulting void structure in a gel (gel silicon compound) prior to pulverization into silica sol particles. Furthermore, for example, when pulverizing a gel silicon compound, the monolith structure can be formed by controlling the particle size distribution of the pulverized silica sol particles to a predetermined size. The particle size distribution can be measured, for example, using a particle size distribution evaluation device such as a dynamic light scattering method or a laser diffraction method, or an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0041] As described above, the porous layer may contain pulverized gel compounds such as gel silicon compounds, and the pulverized particles are chemically bonded to each other. The chemical bonds are not particularly limited, and examples thereof include cross-linking, covalent bonding, and hydrogen bonding. The volume average particle size of the pulverized particles in the porous layer is, for example, 0.10 μm or more, preferably 0.20 μm or more, and more preferably 0.40 μm or more. Meanwhile, the volume average particle size of the pulverized particles in the porous layer is, for example, 2.00 μm or less, preferably 1.50 μm or less, and more preferably 1.00 μm or less. The volume average particle size is an index of the particle size variation of the pulverized particles and is determined by particle size distribution measurement.

[0042] The low refractive index layer may contain silicon atoms. For example, the silicon atoms contained in the low refractive index layer are preferably siloxane-bonded. Of all silicon atoms contained in the low refractive index layer, the proportion of unbonded silicon atoms (specifically, residual silanols) is, for example, less than 50%, preferably 30% or less, and more preferably 15% or less.

[0043] The low refractive index layer may be, for example, unevenness The low refractive index layer can be formed by coating or printing a low refractive index layer-forming liquid (sometimes referred to as a coating liquid) on the first main surface (concave and convex surface) of the layer. unevenness The low refractive index layer can be formed by heating a coating film or a printed layer of a low refractive index layer-forming liquid formed on the first main surface (concave and convex surface) of the layer.

[0044] In one embodiment, the coating film can be formed using a coating liquid containing microporous particles, and the microporous particles can be chemically bonded to each other by heating (including drying) the coating liquid. The coating liquid containing microporous particles is, for example, a suspension. For example, a catalyst (crosslinking reaction accelerator) that accelerates crosslinking between the microporous particles (e.g., a dehydration condensation reaction of residual silanol groups that may be contained in the microporous particles) and / or a substance that generates a catalyst (crosslinking reaction accelerator) (catalyst generator) may be added to the coating liquid. Examples of catalysts include photoactivated catalysts and thermally activated catalysts. Examples of catalyst-generating substances (catalyst generators) include photocatalyst generators and thermal catalyst generators. Examples of photocatalyst generators include photobase generators (catalysts that generate a basic catalyst upon light irradiation) and photoacid generators (substances that generate an acidic catalyst upon light irradiation). For example, the microporous particles are a pulverized product of a gel-like compound (preferably a gel-like silicon compound), and the low refractive index layer is a porous layer composed of a porous body (preferably a silicone porous body) containing the pulverized product of the gel-like compound. Such microporous particles may have the three-dimensional structure of the gel-like compound before pulverization dispersed in the three-dimensional basic structure. Using such microporous particles, a structure based on the three-dimensional basic structure can be formed. Specifically, a new structure different from the three-dimensional structure of the gel-like compound can be formed. Thus, the finally obtained low refractive index layer (porous layer) may have a refractive index as low as, for example, an air layer. Furthermore, by chemically bonding the microporous particles to each other, the three-dimensional basic structure can be fixed, and the finally obtained low refractive index layer (porous layer) can have sufficient strength. Details of the specific configuration and formation method of the low refractive index layer (porous layer) are described, for example, in International Publication No. 2019 / 151073. The disclosure of this publication is incorporated herein by reference.

[0045] The coating thickness of the coating liquid can be set according to the thickness desired for the low refractive index layer. The heating temperature of the coating film (coating liquid) is, for example, 20°C or higher, preferably 50°C or higher. On the other hand, the heating temperature of the coating film (coating liquid) is, for example, 200°C or lower, preferably 150°C or lower. The heating time of the coating film (coating liquid) is, for example, 10 seconds or longer. On the other hand, the heating time of the coating film (coating liquid) is, for example, 24 hours or shorter, preferably 1 hour or shorter, more preferably 30 minutes or shorter, and even more preferably 10 minutes or shorter.

[0046] D. High refractive index layer The refractive index of the high refractive index layer 30 is typically 1.60 to 2.20, as described above. The refractive index of the high refractive index layer 30 is preferably 1.62 to 2.00, more preferably 1.63 to 1.90, even more preferably 1.65 to 1.85, and particularly preferably 1.67 to 1.80. If the refractive index of the high refractive index layer is within this range, even better reflection can be achieved in the laminate film. As a result, a design with extremely high brightness can be realized.

[0047] The total light transmittance of the high refractive index layer 30 is preferably 85% to 99%, more preferably 87% to 98%, and even more preferably 89% to 97%. If the total light transmittance of the high refractive index layer is within this range, for example, when the laminate film is applied to various products, the visibility of the design that can be expressed can be ensured well.

[0048] The haze of the high refractive index layer 30 is preferably less than 2%, more preferably less than 1.5%. On the other hand, the haze may be, for example, 0.1% or more, or 0.2% or more. If the haze of the high refractive index layer is in this range, for example, when the laminate film is applied to various products, the visibility of the design that can be expressed can be ensured well.

[0049] As described above, the thickness of the high refractive index layer 30 is preferably 0.3 μm or more, more preferably 1.0 μm or more, even more preferably 1.2 μm or more, particularly preferably 1.5 μm or more, and particularly preferably 1.8 μm or more. The thickness of the high refractive index layer may be, for example, 3.0 μm or more, or, for example, 3.5 μm or more, or, for example, 4.0 μm or more. On the other hand, the thickness of the high refractive index layer may be, for example, 20 μm or less, or, for example, 12 μm or less, or, for example, 10 μm or less, or, for example, 7 μm or less. If the thickness of the high refractive index layer is within this range, as described above, hue change in the laminate film can be suppressed, and as a result, color unevenness in the resulting design can be suppressed.

[0050] The high refractive index layer 30 may have any suitable configuration as long as it satisfies the above-mentioned characteristics. The high refractive index layer typically includes a binder resin (matrix) and a refractive index adjusting material. Any suitable resin can be used as the binder resin. A water-soluble resin is preferred. Typical examples of water-soluble resins include polyvinyl alcohol (PVA)-based resins and water-soluble acrylic resins. PVA-based resins are preferred. Any suitable resin can be used as the PVA-based resin. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers.

[0051] The saponification degree of the PVA resin is preferably 93.5 mol% or more, more preferably 95.0 mol% or more, and even more preferably 99.0 mol% or more. The upper limit of the saponification degree may be, for example, 100 mol%, or may be, for example, 99.95 mol%, or may be, for example, 99.93 mol%. By using a PVA resin with such a saponification degree, a high refractive index layer with excellent durability can be obtained.

[0052] The weight-average molecular weight of the PVA resin can be appropriately selected depending on the purpose. The weight-average molecular weight is preferably 20,000 to 110,000, more preferably 30,000 to 100,000, and even more preferably 40,000 to 80,000. The weight-average molecular weight can be measured, for example, by gel permeation chromatography (GPC).

[0053] The refractive index adjusting material is essentially used to increase the refractive index of the layer to be formed. Therefore, the refractive index adjusting material is typically a high refractive index material, and may have a refractive index of 2.30 or higher, for example. Any appropriate configuration can be adopted as the refractive index adjusting material, as long as it has such a refractive index. Representative examples of the refractive index adjusting material include metal oxide fine particles. Specific examples of metal oxides include titanium oxide (TiO2), silica (SiO2), zirconium oxide (ZrO2), cerium oxide (CeO2), tin oxide (SnO2), iron oxide (Fe2O3, Fe3O4), zinc oxide (ZnO), antimony tin oxide (ATO), indium tin oxide (ITO), phosphorus tin compounds (PTO), antimony oxide (Sb2O5), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), and zinc antimonate (ZnSb2O6). The metal oxide fine particles may be used alone or in combination of two or more.

[0054] The average particle diameter of the high refractive index fine particles is preferably 1 nm to 100 nm, more preferably 2 nm to 50 nm, and even more preferably 5 nm to 20 nm. Such an average particle diameter provides excellent transparency and ease of handling. The average particle diameter is a value measured without distinguishing between primary and secondary particles, regarding secondary particles as one particle. The average particle diameter can be determined, for example, by observing a predetermined region of the cross section of the high refractive index layer with a transmission electron microscope and averaging the particle diameters of particles (e.g., 50 particles) observed in that region.

[0055] The content of the high refractive index fine particles in the high refractive index layer may be, for example, 40 to 300 parts by weight, and is, for example, 70 to 150 parts by weight, relative to 100 parts by weight of the binder resin.

[0056] E. Colored layer The colored layer 40 may be a monochromatic layer or a design layer having a predetermined design. The colored layer is preferably a monochromatic layer, more preferably a black monochromatic layer. With such a configuration, the design that appears due to reflection in the laminated film can be made clearer.

[0057] The colored layer typically contains a binder resin (matrix) and a colorant. Examples of binder resins include chlorinated polyolefins (e.g., chlorinated polyethylene and chlorinated polypropylene), polyester-based resins, urethane-based resins, acrylic resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, and cellulose-based resins. The binder resins may be used alone or in combination of two or more. In one embodiment, the binder resin is a thermopolymerizable resin. Since thermopolymerizable resins can be used in smaller amounts than photopolymerizable resins, the amount of colorant used (colorant content in the colored layer) can be increased. As a result, particularly when forming a black colored layer, a colored layer with extremely low total light transmittance and excellent hiding power can be formed. In one embodiment, the binder resin is an acrylic resin, preferably an acrylic resin containing a polyfunctional monomer (e.g., pentaerythritol triacrylate) as a copolymerization component. By using an acrylic resin containing a polyfunctional monomer as a copolymerization component, a colored layer with an appropriate elastic modulus can be formed.

[0058] Any appropriate colorant can be used depending on the purpose. Specific examples of colorants include inorganic pigments such as titanium white, zinc white, carbon black, iron black, red iron oxide, chrome vermilion, ultramarine blue, cobalt blue, yellow lead, and titanium yellow; organic pigments or dyes such as phthalocyanine blue, indanthrene blue, isoindolinone yellow, benzidine yellow, quinacridone red, polyazo red, perylene red, and aniline black; metal pigments consisting of scaly flakes of aluminum, brass, and the like; and pearlescent pigments consisting of scaly flakes of titanium dioxide-coated mica, basic lead carbonate, and the like. When forming a black colored layer, carbon black, iron black, and aniline black are preferably used. In this case, it is preferable to use a combination of colorants. This is because they absorb visible light widely and evenly, allowing for the formation of a colorless (i.e., completely black) colored layer. For example, azo compounds and / or quinone compounds can be used in addition to the above colorants. In one embodiment, the colorant contains carbon black as a main component and other colorants (for example, an azo compound and / or a quinone compound). This configuration makes it possible to form a colored layer that is free from coloration and has excellent stability over time. When forming a black colored layer, the colorant can be used in a ratio of preferably 50 to 200 parts by weight per 100 parts by weight of the binder resin. In this case, the content of carbon black in the colorant is preferably 80% to 100%. By using the colorant (particularly carbon black) in such a ratio, it is possible to form a colored layer that has an extremely low total light transmittance and excellent stability over time.

[0059] The thickness of the colored layer may be, for example, 1 μm to 3 mm (3000 μm), or may be, for example, 10 μm to 1 mm (1000 μm). Furthermore, the colored layer preferably has a total light transmittance of 0.01% or less at a thickness of 100 μm, more preferably 0.008% or less. If the total light transmittance is within this range, the design that appears by reflection in the laminated film can be made exceptionally clear.

[0060] F. Image display device The laminate film according to the embodiment of the present invention is used in an image display device. Therefore, such an image display device can also be included in the embodiment of the present invention. Representative examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (e.g., an organic EL display device or an inorganic EL display device). Examples of product forms of the image display device include a smartphone and a tablet terminal. Furthermore, the laminate film according to the embodiment of the present invention may be used in a cover case that houses the image display device.

[0061] FIG. 3 is a schematic cross-sectional view illustrating an image display device according to one embodiment of the present invention (i.e., a usage form of the laminate film of FIG. 1). The image display device 200 in the illustrated example has an image display surface 201 and a back surface (a surface not involved in image display) 202. The laminate film 100 of FIG. 1 is disposed on the back surface 202 of the image display device 200. More specifically, the laminate film 100 is attached to the back surface 202 of the image display device 200 via the adhesive layer 120, with the high refractive index layer 30 facing the image display device 200. According to this embodiment, the laminate film allows a design to appear on the back surface 202 of the image display device 200, thereby imparting design appeal to the image display device itself. According to this embodiment, for example, when a smartphone is not used with a case, the commercial value of the smartphone can be enhanced. As is clear from FIG. 3, the design of the laminate film appears on the back surface 202 of the image display device 200, as indicated by the arrow, and is not involved in image display.

[0062] Figure 3 illustrates an embodiment in which the laminate film of Figure 1 is placed in an image display device, but it goes without saying that laminate films according to other embodiments of the present invention (e.g., the laminate film of Figure 2, laminate films according to embodiments not shown) can also be placed in an image display device. [Example]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Unless otherwise specified, "%" and "parts" in the examples are by weight.

[0064] (1) Refractive index The low refractive index layer or high refractive index layer used in the examples and comparative examples was formed on an acrylic film. The resulting laminate was cut to a size of 25 mm x 50 mm. The cut laminate was attached to the surface of a glass plate (thickness: 3 mm) via an adhesive. The center of the back surface of the glass plate (diameter: approximately 20 mm) was filled in with black marker to create a sample that did not reflect light from the back surface of the glass plate. The sample was placed in an ellipsometer (JA Woollam Japan: VASE), and the refractive index was measured at a wavelength of 550 nm and an incident angle of 50 to 80 degrees.

[0065] (2) Thickness The thickness was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000").

[0066] (3)Reflectance The spectral reflectance in the visible light region of the laminated films obtained in the examples and comparative examples was determined using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, product name "U4100") and evaluated according to the following criteria. ○ (Good): Reflectance is 5.0% or more × (Poor): Reflectance is less than 5.0%

[0067] (4) Hue change The chromaticity value (x, y) was calculated from the spectral reflectance obtained in (3) above. The amount of change Δxy from the achromatic value (x', y') was calculated using the following formula: Δxy={(xx´) 2 +(yy´) 2} 1 / 2 The obtained Δxy was evaluated as an index of hue change according to the following criteria. ◎(Excellent) :Δxy(×10 2 ) is less than 3.0 ○(Good) :Δxy(×10 2 ) is between 3.0 and 5.0 △(Acceptable): Δxy(×10 2 ) is 5.0 or more and less than 7.0

[0068] [Production Example 1] Preparation of coating liquid for forming low refractive index layer (1) Gelation of silicon compounds Mixture A was prepared by dissolving 0.95 g of methyltrimethoxysilane (MTMS), a precursor of a silicon compound, in 2.2 g of dimethyl sulfoxide (DMSO). 0.5 g of a 0.01 mol / L aqueous solution of oxalic acid was added to this mixture A, and the mixture was stirred at room temperature for 30 minutes to hydrolyze the MTMS, producing mixture B containing tris(hydroxy)methylsilane. To 5.5 g of DMSO, 0.38 g of 28 wt % aqueous ammonia and 0.2 g of pure water were added, and then the above mixed solution B was further added and stirred at room temperature for 15 minutes to gel the tris(hydroxy)methylsilane, thereby obtaining mixed solution C containing a gel-like silicon compound. (2) Aging treatment The mixed solution C containing the gel-like silicon compound prepared as above was incubated as is at 40° C. for 20 hours for aging treatment. (3) Crushing Next, the gel-like silicon compound aged as described above was crushed into granules of several mm to several cm in size using a spatula. Next, 40 g of isopropyl alcohol (IPA) was added to mixed solution C, and after light stirring, the mixture was left to stand at room temperature for 6 hours, and the solvent and catalyst in the gel were decanted. The same decantation process was repeated three times to replace the solvent, yielding mixed solution D. The gel-like silicon compound in mixed solution D was then crushed (high-pressure media-less crushing). The crushing process (high-pressure media-less crushing) was carried out using a homogenizer (manufactured by SMT Corporation, product name "UH-50"), with 1.85 g of the gel-like compound and 1.15 g of IPA in mixed solution D weighed into a 5 cc screw bottle, and crushed for 2 minutes at 50 W and 20 kHz. This grinding process pulverized the gel-like silicon compound in the mixed solution D, turning the mixed solution D into a pulverized sol solution E. The volume average particle size, which indicates the particle size variation of the pulverized material contained in sol solution E, was measured using a dynamic light scattering Nanotrac particle size analyzer (manufactured by Nikkiso Co., Ltd., UPA-EX150 model) and found to be 0.50 to 0.70 μm. Furthermore, 0.015 g of a 1.5 wt % MEK (methyl ethyl ketone) solution of a photobase generator (Wako Pure Chemical Industries, Ltd., product name: WPBG266) and 0.005 g of a 5% MEK solution of a bis-crosslinking accelerator ((trimethoxysilyl)hexane) were added to 0.75 g of sol solution E to obtain a coating solution 1 for forming a low refractive index layer. The refractive index of the low refractive index layer formed using this coating solution was 1.16.

[0069] [Production Example 2] Preparation of coating liquid for forming low refractive index layer Except for adding 0.060 g of a 1.5 wt % MEK (methyl ethyl ketone) solution of a base generator (Wako Pure Chemical Industries, Ltd., product name: WPBG266) and 0.018 g of a 5% MEK solution of a bis-crosslinking accelerator ((trimethoxysilyl)hexane) to 0.75 g of sol solution E, the same procedure as in Production Example 1 was carried out to obtain low refractive index layer-forming coating solution 2. The refractive index of the low refractive index layer formed using this coating solution was 1.19.

[0070] [Production Example 3] Preparation of coating liquid for forming low refractive index layer Except for adding 0.180 g of a 1.5 wt % MEK (methyl ethyl ketone) solution of a base generator (Wako Pure Chemical Industries, Ltd., product name: WPBG266) and 0.054 g of a 5% MEK solution of a bis-crosslinking accelerator ((trimethoxysilyl)hexane) to 0.75 g of sol solution E, the same procedure as in Production Example 1 was carried out to obtain low refractive index layer-forming coating solution 3. The refractive index of the low refractive index layer formed using this coating solution was 1.25.

[0071] [Production Example 4] Preparation of coating liquid for forming high refractive index layer A 6.0% aqueous solution of polyvinyl alcohol (product name "JC-25" manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.) was prepared. 72 parts (solids) of titanium oxide sol (product name "M-6" manufactured by Taki Chemical Co., Ltd.; average particle size of titanium oxide: 5 nm) was added to 100 parts (solids) of this aqueous solution to obtain Coating Solution A for forming a high refractive index layer. The refractive index of the high refractive index layer formed using this coating solution was 1.65.

[0072] [Production Example 5] Preparation of coating liquid for forming high refractive index layer Except for adding 130 parts (solid content) of titanium oxide sol to 100 parts (solid content) of the PVA aqueous solution, the same procedure as in Production Example 4 was carried out to obtain Coating Solution B for forming a high refractive index layer. The refractive index of the high refractive index layer formed using this coating solution was 1.70.

[0073] [Production Example 6] Preparation of coating liquid for forming high refractive index layer Except for adding 240 parts (solid content) of titanium oxide sol to 100 parts (solid content) of the PVA aqueous solution, the same procedure as in Production Example 4 was carried out to obtain Coating Solution C for forming a high refractive index layer. The refractive index of the high refractive index layer formed using this coating solution was 1.75.

[0074] [Example 1] unevenness An acrylic film having an uneven structure on one side was used as the layer. The coating liquid 1 for forming a low refractive index layer prepared in Production Example 1 was applied to the uneven surface of the acrylic film. The coating film was treated and dried at a temperature of 100°C for 1 minute, forming a low refractive index layer (thickness 3.0 μm) on the uneven surface of the acrylic film. The refractive index of the low refractive index layer was 1.16 as described above. Next, the coating liquid B for forming a high refractive index layer prepared in Production Example 5 was applied to the surface of the low refractive index layer. The coating film was treated and dried at a temperature of 100°C for 3 minutes, forming a high refractive index layer (thickness 4.5 μm) on the low refractive index layer. The refractive index of the high refractive index layer was 1.70 as described above. In this way, unevenness A laminate film having a structure of a layer / low refractive index layer / high refractive index layer was obtained. The obtained laminate film was subjected to the evaluation of "reflectance" and "hue change" as described above. The results are shown in Table 1.

[0075] [Examples 2 to 8] A laminate film was obtained in the same manner as in Example 1, except that the types and coating thicknesses of the low-refractive-index layer-forming coating liquid and the high-refractive-index layer-forming coating liquid were changed to form low-refractive-index layers and high-refractive-index layers having the refractive indices and thicknesses shown in Table 1. The obtained laminate film was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0076] [Comparative Example 1] The acrylic film used in Example 1 was directly subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0077] Comparative Example 2 The same procedure as in Example 2 was carried out except that the high refractive index layer was not formed. unevenness A laminated film having a structure of a layer / a low refractive index layer was obtained. The obtained laminated film was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

[0078] [Table 1]

[0079] As is clear from Table 1, the examples of the present invention provide laminated films with high reflectance and reduced hue change. Such laminated films can realize designs with high brightness and reduced color unevenness. [Industrial Applicability]

[0080] The laminate film according to the embodiment of the present invention can be suitably used as a decorative film, and in particular, can be suitably used as a decorative film to be applied to the back surface (the surface not involved in image display) of an image display device. [Explanation of symbols]

[0081] 10 unevenness layer 10a First principal surface 10b Second principal surface 20 Low refractive index layer 30 High refractive index layer 100 Laminated Film 120 adhesive layer 200 Image display device

Claims

1. a concavo-convex layer having a first main surface and a second main surface, the first main surface having a concavo-convex structure; a low refractive index layer provided on a first major surface of the concave-convex layer; a high refractive index layer provided on the low refractive index layer opposite to the uneven layer; and The relief layer is a shaped film, a reflective hologram film, a microlens array film, a prism film, or a lenticular lens. Laminated film.

2. 2. The laminated film according to claim 1, wherein the low refractive index layer has a refractive index of 1.30 or less and a thickness of 0.3 μm or more.

3. 3. The laminated film according to claim 2, wherein the high refractive index layer has a refractive index of 1.60 to 2.20 and a thickness of 0.3 μm or more.

4. The laminated film according to claim 1 , wherein the uneven layer has a function of converting the direction of light.

5. 2. The laminated film according to claim 1, wherein P / H is 1.5 or more, where H is the height of the projections and recesses in the projection-recess structure of the projection-recess layer, and P is the pitch of the projections and recesses.

6. The laminate film according to claim 1 , further comprising a colored layer on the opposite side of the high refractive index layer from the low refractive index layer.

7. having an image display surface and a back surface, The laminated film according to any one of claims 1 to 5 is disposed on the back surface. Image display device.

8. having an image display surface and a back surface, The laminated film according to claim 6 is disposed on the back surface. Image display device.

Images