WO2024117068A1

WO2024117068A1 - Reflective film

Info

Publication number: WO2024117068A1
Application number: PCT/JP2023/042319
Authority: WO
Inventors: 帆奈美伊藤; 圭太碓井
Original assignee: 日東電工株式会社
Priority date: 2022-11-30
Filing date: 2023-11-27
Publication date: 2024-06-06

Abstract

A reflective film (X) according to the present invention comprises, in order in the thickness direction, a substrate film (10), a metal reflective layer (20), and a blackened layer (30). The blackened layer (30) is an inorganic blackened layer that includes a metal oxide and has a thickness of 400 nm or less.

Description

Reflective Film

The present invention relates to a reflective film.

A liquid crystal display device comprises a liquid crystal panel having an image display surface, a backlight that emits light toward the rear surface of the panel, and a housing that houses these. The housing has a bezel portion as a frame around the image display surface. A reflective film is disposed on the inner wall surface of the bezel portion. This reflective film is used to prevent light from the backlight from leaking out from the bezel portion (preventing light leakage). Such a reflective film is described, for example, in Patent Document 1 listed below.

JP 2004-184443 A

Patent Document 1 describes a reflective film that includes a white resin film, a metal thin film layer, and a black ink layer in that order in the thickness direction. According to Patent Document 1, the black ink layer is formed by printing black ink on the surface of the metal thin film layer on the white resin film. The black ink contains a resin binder and a black pigment. The preferred thickness of the black ink layer is 0.5 to 3 μm. From the viewpoint of preventing pinholes from being formed in the black ink layer, it is preferable that multiple black ink layers are laminated. In such a reflective film with a black ink layer, the above-mentioned light leakage is prevented by the light reflection by the metal thin film layer and the light blocking by the black ink layer.

However, in the reflective film of Patent Document 1, the adhesion of the black ink layer to the thin metal layer is insufficient.

　Black ink layers containing a resin binder are prone to compressive residual stress after the layer is formed. The compressive residual stress on the exposed side (the side opposite the metal thin film layer) is greater than the compressive residual stress on the side of the black ink layer that is fixed to the metal thin film layer. The thicker the black ink layer, the greater the difference in compressive residual stress on both sides. And the greater the difference in compressive residual stress on both sides of the black ink layer, the poorer the adhesion of the black ink layer to the metal thin film layer. Black ink layers with insufficient adhesion are prone to peeling. Peeling of the black ink layer impairs the reflective film's ability to prevent light leakage.

The present invention provides a reflective film suitable for ensuring adhesion of a blackening layer to a metal reflective layer.

The present invention [1] includes a reflective film having a base film, a metal reflective layer, and a blackening layer in this order in the thickness direction, the blackening layer being an inorganic blackening layer containing a metal oxide and having a thickness of 400 nm or less.

The present invention [2] includes the reflective film described in [1] above, in which the metal reflective layer is an aluminum layer.

The present invention [3] includes the reflective film described in [1] or [2] above, in which the thickness of the metal reflective layer is 30 nm or more.

The present invention [4] includes the reflective film according to any one of [1] to [3] above, in which the thickness of the metal reflective layer is 500 nm or less.

The present invention [5] includes the reflective film described in any one of [1] to [4] above, in which the thickness of the blackening layer is 5 nm or more.

The present invention [6] includes the reflective film described in any one of [1] to [5] above, which has a cured resin layer on the side of the blackening layer opposite the metal reflective layer.

The present invention [7] includes a reflective film according to any one of [1] to [6] above, in which the blackened layer does not peel off in a peel test conforming to JIS K 5400.

As described above, the reflective film of the present invention comprises a base film, a metal reflective layer, and a blackening layer in this order in the thickness direction, and the blackening layer is an inorganic blackening layer containing metal oxide and having a thickness of 400 nm or less. The blackening layer being a thin inorganic blackening layer of 400 nm or less is suitable for reducing the difference in compressive residual stress that occurs on both sides of the blackening layer in the thickness direction after film formation. Reducing the difference in compressive residual stress is suitable for ensuring the adhesion of the blackening layer to the metal reflective layer.

1 is a schematic cross-sectional view of one embodiment of a reflective film of the present invention. FIG. 2 shows a method for manufacturing the reflective film shown in FIG. 1. FIG. 2A shows a step of preparing a substrate film, FIG. 2B shows a step of forming a metal reflective layer on the substrate film, FIG. 2C shows a step of forming a blackened layer on the metal reflective layer, and FIG. 2D shows a step of forming a cured resin layer on the blackened layer. 1 is a schematic cross-sectional view of a modified example of the reflective film of the present invention, which does not have a cured resin layer on a blackening layer.

Reflective film X according to one embodiment of the present invention comprises a base film 10, a metal reflective layer 20, a blackening layer 30, and a cured resin layer 40, in this order in the thickness direction H, as shown in FIG. 1. Reflective film X extends in a direction (plane direction) perpendicular to the thickness direction H. Reflective film X is, for example, a reflective film that prevents light from a backlight of a liquid crystal display device from leaking out of the housing.

The base film 10 is a base material that ensures the strength of the reflective film X. The base film 10 has a first surface 11 and a second surface 12 opposite to the first surface 11. The base film 10 is, for example, a transparent resin film having flexibility. Examples of the material of the base film 10 include polyester resin, polyolefin resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, polyimide resin, cellulose resin, and polystyrene resin. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer. Examples of the acrylic resin include polymethacrylate. From the viewpoints of transparency and strength, the material of the base film 10 is preferably polyester resin, and more preferably PET.

The base film 10 is preferably a white film from the viewpoint of ensuring significant light reflectivity of the base film 10. The white film can be obtained, for example, by incorporating particles such as inorganic fillers that cause light scattering into the resin film described above. Examples of such particles include titanium oxide, calcium carbonate, barium sulfate, silica, and talc, and preferably titanium oxide and/or silica are used. These particles may be used alone or in combination of two or more types. The average particle size of the particles is, for example, 0.05 μm or more, preferably 0.1 μm or more, and, for example, 2 μm or less, preferably 1 μm or less. The content ratio of the particles in the base film 10 as a white film is, for example, 5 mass% or more, preferably 10 mass% or more, and, for example, 50 mass% or less, preferably 40 mass% or less.

From the viewpoint of the strength of the reflective film X, the thickness of the base film 10 is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 35 μm or more. From the viewpoint of ensuring the handleability of the base film 10 in the roll-to-roll method, the thickness of the base film 10 is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less.

The first surface 11 of the substrate film 10 may be subjected to a surface modification treatment in order to ensure adhesion of the metal reflective layer 20 to the substrate film 10. Examples of surface modification treatments include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

In this embodiment, the metal reflective layer 20 is disposed on the first surface 11 of the base film 10. That is, in this embodiment, the metal reflective layer 20 is in contact with the first surface 11.

The metal reflective layer 20 is formed from a metal having light reflectivity. Examples of metal materials that form the metal reflective layer 20 include aluminum (Al), silver (Ag), titanium (Ti), and alloys thereof. From the viewpoint of ensuring good light reflectivity of the metal reflective layer 20 for visible light, the material of the metal reflective layer 20 is preferably aluminum or silver.

The thickness of the metal reflective layer 20 is preferably 30 nm or more, more preferably 50 nm or more, even more preferably 70 nm or more, even more preferably 90 nm or more, and particularly preferably 100 nm or more, from the viewpoint of ensuring the light reflectivity of the metal reflective layer 20 and the reflective film X. The thickness of the metal reflective layer 20 is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, even more preferably 150 nm or less, and even more preferably 120 nm or less, from the viewpoint of ensuring the adhesion of the metal reflective layer 20 to the substrate film 10.

The luminous reflectance (Y value) of the metal reflective layer 20 at wavelengths of 380 nm to 780 nm in the CIE-XYZ color system is preferably 70% or more, more preferably 75% or more, and even more preferably 80% or more, from the viewpoint of ensuring the light reflectivity of the metal reflective layer 20 and the reflective film X. The luminous reflectance is, for example, 90% or less, 95% or less, or 100% or less. The luminous reflectance can be measured, for example, by a spectrophotometer (product name "U-4100", manufactured by Hitachi High-Tech Science Corporation). The method for measuring the luminous reflectance is specifically described below in relation to the examples.

In this embodiment, the blackening layer 30 is disposed on the metal reflective layer 20. That is, in this embodiment, the blackening layer 30 is in contact with the metal reflective layer 20.

The blackening layer 30 contains a metal oxide having high light absorption. Examples of the metal (first metal) forming the metal oxide include copper (Cu), indium (In), molybdenum (Mo) and iron (Fe). The metal oxide preferably contains at least one selected from the group consisting of Cu, In, Mo and Fe. As the metal oxide, an oxide containing Cu and In is preferable from the viewpoint of ensuring adhesion of the cured resin layer 40 to the blackening layer 30 and from the viewpoint of ensuring stability during sputtering film formation when a sputtering method is adopted as a film formation method for the blackening layer 30. That is, as the metal oxide, copper indium oxide is preferable. In the copper indium oxide, the proportion of Cu in the total amount of Cu and In is preferably 10 atomic % or more, more preferably 20 atomic % or more, and even more preferably 30 atomic % or more, from the viewpoint of ensuring adhesion of the cured resin layer 40 to the blackening layer 30. The proportion of Cu is preferably 90 atomic % or less, more preferably 80 atomic % or less, and even more preferably 70 atomic % or less.

The blackening layer 30 may contain an elemental metal in addition to the metal oxide. Examples of the elemental metal (second metal) include In, Cu, Mo, and Fe. The elemental metal is preferably at least one selected from the group consisting of In, Cu, Mo, and Fe. When the blackening layer 30 contains multiple elemental metals, it is preferable that the multiple elemental metals include a metal different from the first metal in the above-mentioned metal oxide. More preferably, the elemental metal is a metal other than the first metal.

The proportion of the first metal in the blackening layer 30 is preferably 10 atomic % or more, more preferably 20 atomic % or more, and is preferably 90 atomic % or less, more preferably 80 atomic % or less, from the viewpoint of realizing high light blocking properties in the blackening layer 30. The proportion of the second metal in the blackening layer 30 is preferably 10 atomic % or more, more preferably 20 atomic % or more, and is preferably 90 atomic % or less, more preferably 80 atomic % or less, from the viewpoint of realizing high light blocking properties in the blackening layer 30.

From the viewpoint of realizing high light-shielding properties in the blackening layer 30, the blackening layer 30 preferably contains a metal oxide and a single metal other than the first metal, and more preferably contains indium oxide as the metal oxide and copper as the single metal. When the blackening layer 30 contains indium oxide and copper, the proportion of In in the blackening layer 30 is preferably 40 atomic % or more, more preferably 50 atomic % or more, and is preferably 90 atomic % or less, more preferably 80 atomic % or less, from the viewpoint of realizing high light-shielding properties in the blackening layer 30. When the blackening layer 30 contains indium oxide and copper, the proportion of Cu in the blackening layer 30 is preferably 5 atomic % or more, more preferably 10 atomic % or more, and is preferably 50 atomic % or less, more preferably 40 atomic % or less, from the viewpoint of realizing high light-shielding properties in the blackening layer 30.

The thickness of the blackening layer 30 is 400 nm or less, preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 110 nm or less, from the viewpoint of ensuring adhesion of the blackening layer 30 to the base (metal reflective layer 20 in this embodiment). The thickness of the blackening layer 30 is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 50 nm or more, from the viewpoint of ensuring the light-shielding properties of the blackening layer 30 and the reflective film X.

The luminous transmittance (Y value) of the blackening layer 30 at wavelengths of 380 nm to 780 nm in the CIE-XYZ color system is preferably 0.1% or less, more preferably 0.05% or less, and even more preferably 0.03% or less, from the viewpoint of ensuring the light-shielding properties of the blackening layer 30 and the reflective film X. The luminous transmittance is, for example, 0.001% or more, 0.005% or more, or 0.01% or more. The luminous transmittance can be measured, for example, by a spectrophotometer (product name "U-4100", manufactured by Hitachi High-Tech Science Corporation). The method for measuring the luminous transmittance is specifically described below in the examples.

The blackening layer 30 is preferably a dry coating film from the viewpoint of ensuring adhesion of the blackening layer 30 to the undercoat. Examples of dry coating films include a sputtered film formed by a sputtering method and a vapor deposition film formed by a vapor deposition method, with a sputtered film being preferred.

In this embodiment, the cured resin layer 40 is disposed on the blackening layer 30. That is, in this embodiment, the cured resin layer 40 is in contact with the blackening layer 30. The cured resin layer 40 is a hard coat layer that makes it difficult for scratches to form on the reflective film X.

The cured resin layer 40 is a cured product of a curable resin composition. The curable resin composition contains a curable resin. Examples of the curable resin include polyester resin, acrylic urethane resin, acrylic resin (excluding acrylic urethane resin), urethane resin (excluding acrylic urethane resin), amide resin, silicone resin, epoxy resin, and melamine resin. These curable resins may be used alone or in combination of two or more types. From the viewpoint of ensuring high hardness of the cured resin layer 40, at least one selected from the group consisting of acrylic urethane resin and acrylic resin is preferably used as the curable resin.

In addition, examples of the curable resin include ultraviolet-curable resin and thermosetting resin. As the curable resin can be cured without high temperature heating, ultraviolet-curable resin is preferred from the viewpoint of improving the manufacturing efficiency of the reflective film X.

The curable resin composition may contain particles. Examples of the particles include inorganic oxide particles and organic particles. Examples of the inorganic oxide particle material include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Examples of the organic particle material include polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate. The particles may be used alone or in combination of two or more kinds. The particles are preferably inorganic oxide particles, and more preferably at least one selected from silica particles and zirconia particles.

The average particle diameter (D50) of the particles is preferably 20 nm or more, more preferably 25 nm or more, and even more preferably 30 nm or more, from the viewpoint of ensuring the hardness of the cured resin layer 40. The average particle diameter (D50) of the particles is preferably 300 nm or less, and particularly preferably 100 nm or less, from the viewpoint of uniform dispersion of the particles in the cured resin layer 40. The average particle diameter (D50) of the particles is the median diameter in the volume-based particle size distribution (the particle diameter at which the volume cumulative frequency reaches 50% from the small diameter side), and is determined, for example, based on the particle size distribution obtained by a laser diffraction/scattering method.

The proportion of particles in the cured resin layer 40 is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of ensuring the hardness of the cured resin layer 40. The proportion of particles in the cured resin layer 40 is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, from the viewpoint of uniform dispersion of the particles in the cured resin layer 40.

The thickness of the cured resin layer 40 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more, from the viewpoint of providing sufficient abrasion resistance in the cured resin layer 40. The thickness of the cured resin layer 40 is preferably 5 μm or less, more preferably 3 μm or less, even more preferably 2 μm or less, and even more preferably 1.5 μm or less, from the viewpoint of ensuring adhesion of the cured resin layer 40 to the blackening layer 30.

The luminous reflectance (Y value) of the reflective film X at wavelengths of 380 nm to 780 nm in the CIE-XYZ color system is preferably 80% or more, more preferably 82% or more, and even more preferably 85% or more, from the viewpoint of ensuring the light leakage prevention properties of the reflective film X described below. The luminous reflectance is, for example, 90% or less, 95% or less, or 100% or less. The luminous reflectance (Y value) of the reflective film X is the reflectance of light irradiated onto the reflective film X from the substrate film 10 side.

The luminous transmittance (Y value) of the reflective film X at wavelengths of 380 nm to 780 nm in the CIE-XYZ color system is preferably 0.10% or less, more preferably 0.09% or less, and even more preferably 0.07% or less, from the viewpoint of ensuring the light leakage prevention properties of the reflective film X described below. The luminous transmittance is, for example, 0.001% or more, 0.005% or more, or 0.01% or more. The luminous transmittance (Y value) of the reflective film X is the transmittance of light irradiated onto the reflective film X from the substrate film 10 side.

The reflective film X preferably does not peel off the blackened layer 30 in a peel test conforming to JIS K 5400. The peel test conforming to JIS K 5400 is a checkerboard peel test. The specific method for carrying out the peel test is as described below in relation to the examples.

Reflective film X is manufactured using a roll-to-roll method, for example, as follows.

First, as shown in FIG. 2A, a base film 10 is prepared (base film preparation process). The first surface 11 of the base film 10 is subjected to a surface modification treatment as necessary. When a plasma treatment is used as the surface modification treatment, argon gas, for example, is used as an inert gas. The discharge power in the plasma treatment is, for example, 10 W or more and, for example, 5000 W or less.

Next, as shown in FIG. 2B, a metal reflective layer 20 is formed on the base film 10 (metal reflective layer formation process). Specifically, a metal material is deposited on the first surface 11 of the base film 10 by a dry coating method to form the metal reflective layer 20. Examples of dry coating methods include a sputtering method and a vapor deposition method, with the sputtering method being preferred.

In the sputtering method, for example, a sputtering deposition apparatus capable of performing a film formation process using a roll-to-roll method is used. Specifically, in the sputtering method, a sputtering gas (inert gas) is introduced under vacuum conditions into a deposition chamber equipped with the sputtering deposition apparatus, while a negative voltage is applied to a target placed on a cathode in the deposition chamber. This generates a glow discharge to ionize gas atoms, and the gas ions collide with the target surface at high speed, ejecting the target material from the target surface, and the ejected target material is deposited on the substrate film 10.

The target material placed on the cathode in the film formation chamber (i.e., the material of the metal reflective layer 20) is a sintered body of the metal material described above for the metal reflective layer 20, and preferably a sintered body of Al or an Al alloy. The air pressure in the film formation chamber during film formation by sputtering (sputter film formation) is, for example, 0.02 Pa or more and, for example, 1 Pa or less. Examples of power sources for applying voltage to the target include DC power sources, AC power sources, MF power sources, and RF power sources (the same applies to the sputter film formation described below for the blackened layer 30). The absolute value of the discharge voltage during sputter film formation is, for example, 50 V or more and, for example, 500 V or less (the same applies to the sputter film formation described below for the blackened layer 30).

Next, as shown in FIG. 2C, a blackening layer 30 is formed on the metal reflective layer 20 (blackening layer formation process). Specifically, a metal oxide-containing material is deposited on the metal reflective layer 20 by a dry coating method to form a blackening layer 30 having a thickness of 400 nm or less. Examples of dry coating methods include a sputtering method and a vapor deposition method, with the sputtering method being preferred.

The target material placed on the cathode in the deposition chamber (i.e., the material of the blackening layer 30) may be, for example, a sintered body of the metal oxide described above, preferably a sintered body of copper indium oxide. Alternatively, the target material is preferably a sintered body containing the metal oxide and elemental metal described above for the blackening layer 30. The air pressure in the deposition chamber during sputter deposition of the blackening layer 30 is, for example, 0.02 Pa or more, and, for example, 1 Pa or less.

The blackening layer 30 formed from an inorganic material containing metal oxide is less susceptible to compressive residual stress than the above-mentioned black ink layer formed with a resin component. In addition, the blackening layer 30 is thin, with a thickness of 400 nm or less. In such a thin blackening layer 30 (inorganic blackening layer), the difference between the compressive residual stress on the side fixed to the metal reflective layer 20 and the compressive residual stress on the side opposite the metal reflective layer 20 is small (the thinner the blackening layer 30, the smaller the difference in compressive residual stress on both sides). Furthermore, the small difference in compressive residual stress on both sides of the thickness direction H of the blackening layer 30 helps ensure adhesion of the blackening layer 30 to the metal reflective layer 20.

The entire process from the metal reflective layer formation process to the blackened layer formation process is carried out on one pass line while the work film is transported using the roll-to-roll method. During the process on one pass line, the work film is never exposed to the atmosphere. Forming the blackened layer 30 on the metal reflective layer 20 without exposing the work film to the atmosphere after the formation of the metal reflective layer 20 helps to ensure the adhesion of the blackened layer 30 to the metal reflective layer 20.

Next, as shown in FIG. 2D, a cured resin layer 40 is formed on the blackened layer 30 (cured resin layer forming step). The cured resin layer 40 can be formed by applying the above-mentioned curable resin composition on the blackened layer 30 to form a coating film, and then curing the coating film. If the curable resin composition contains an ultraviolet-curable resin, the coating film is cured by ultraviolet irradiation. If the curable resin composition contains a thermosetting resin, the coating film is cured by heating.

In this manner, reflective film X can be manufactured.

The reflective film X may not have a cured resin layer 40, as shown in FIG. 3. Such a reflective film X can be manufactured by not carrying out the above-mentioned cured resin layer forming process (FIG. 2D). In order to ensure the abrasion resistance of the reflective film X on the side opposite to the second surface 12, it is preferable that the reflective film X has a cured resin layer 40.

As described above, the reflective film X comprises a base film 10, a metal reflective layer 20, and a blackening layer 30 in this order in the thickness direction H, and the blackening layer 30 is an inorganic blackening layer containing metal oxide and has a thickness of 400 nm or less. With such a reflective film X, the above-mentioned light leakage can be prevented by the light reflection at the metal reflective layer 20 and the light blocking by the blackening layer 30.

In the reflective film X, the blackening layer 30 is a thin inorganic blackening layer of 400 nm or less, which is suitable for reducing the difference in compressive residual stress that occurs on both sides of the thickness direction H of the blackening layer 30 after film formation. Reducing the difference in compressive residual stress helps ensure the adhesion of the blackening layer 30 to the metal reflective layer 20. Therefore, the reflective film X is suitable for ensuring the adhesion of the blackening layer 30 to the metal reflective layer 20. And the higher the adhesion of the blackening layer 30 to the metal reflective layer 20, the more the peeling of the blackening layer 30 is suppressed, and the reflective film X can exhibit good light leakage prevention function.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples. Furthermore, the specific numerical values of the compounding amounts (contents), physical properties, parameters, etc. described below can be replaced with the upper limits (numerical values defined as "equal to or less than") or lower limits (numerical values defined as "equal to or more than") of the corresponding compounding amounts (contents), physical properties, parameters, etc. described in the above-mentioned "Form for carrying out the invention."

Example 1
First, a white polyethylene terephthalate (PET) film (product name: "Lumirror E20", thickness: 38 μm, manufactured by Toray Industries, Inc.) was prepared as a substrate film.

Next, a metal reflective layer and a blackening layer were formed in that order on one side (first side) of the PET film by sputtering (sputter deposition process). In this sputter deposition process, a roll-to-roll sputter deposition device (DC magnetron sputter deposition device) was used. The device is equipped with a pay-out chamber, a first deposition chamber, a second deposition chamber, and a winding chamber. The pay-out chamber is equipped with a pay-out roller. A roll of the above-mentioned base film was set on the pay-out roller as the work film. The winding chamber is equipped with a winding roller that can wind up the work film. In the first and second deposition chambers, the deposition process can be carried out while the work film is running from the pay-out chamber to the winding chamber by the roll-to-roll method.

In the sputter deposition process, specifically, the first sputter deposition in the first deposition chamber and the second sputter deposition in the second deposition chamber were carried out in sequence, after which the work film (substrate film/metal reflective layer/blackened layer) was wound around the winding roller in the winding chamber. In the first sputter deposition, a 75 nm thick aluminum (Al) layer was formed as a metal reflective layer on the first surface of the PET film. In the subsequent second sputter deposition, a 30 nm thick blackened layer was formed on the Al layer. The conditions for each sputter deposition were as follows:

In the first sputter deposition, the sputter deposition equipment (the payout chamber, the first and second deposition chambers, and the winding chamber) was evacuated to a vacuum, and then argon (Ar) was introduced into the first deposition chamber as a sputtering gas, and the air pressure in the first deposition chamber was set to 0.3 to 0.4 Pa. An Al target was used as the target. A DC power supply was used as the power supply for applying voltage to the target. The deposition temperature (the temperature of the substrate film on which the Al layer is laminated) was set to 40°C.

In the second sputtering deposition, after the above-mentioned evacuation of the sputtering deposition apparatus, Ar was introduced as a sputtering gas into the second deposition chamber, and the pressure in the second deposition chamber was set to 0.3 to 0.4 Pa. In addition, a black inorganic target (product name "DIABLA12", a mixed target of indium oxide (In ₂ O ₃ ) and copper (Cu), In ratio of 67.3 (±3) mass%, manufactured by Mitsubishi Materials Corporation) was used as the target. A DC power supply was used as the power source for applying voltage to the target. The deposition temperature (the temperature of the workpiece film on which the blackened layer is formed) was set to 40°C.

Next, a first curable resin composition was applied onto the blackened layer to form a coating. The first curable resin composition contains an ultraviolet-curable acrylic urethane resin (product name: AICA ITRON Z844, manufactured by AICA Corporation) and methyl ethyl ketone as a solvent. Next, the coating was dried and then cured by exposure to ultraviolet light to form a 1 μm-thick hard coat (HC) layer.

In this manner, the reflective film of Example 1 was produced. The reflective film of Example 1 has a laminated structure of a substrate film (thickness 38 μm), a metal reflective layer (Al layer, thickness 75 nm), a blackened layer (thickness 30 nm), and an HC layer (thickness 1 μm). In Example 1, the metal reflective layer, the blackened layer, and the HC layer on the substrate film form a multilayer film (the same applies to Example 2 described below).

Example 2
The reflective film of Example 2 was produced in the same manner as the reflective film of Example 1, except for the following. In forming the HC layer, the second curable resin composition was used instead of the first curable resin composition. The second curable resin composition contains 100 parts by mass of an ultraviolet-curable acrylic urethane resin (product name "AICA ITRON Z844", manufactured by AICA Corporation), 1 part by mass of crosslinked polymethyl methacrylate particles having an average particle size (D50) of 2.5 μm (product name "MBX-2H", manufactured by Sekisui Chemical Industry Co., Ltd.), and methyl ethyl ketone as a solvent.

Example 3
Except for not forming an HC layer on the blackened layer, the reflective film of Example 3 was produced in the same manner as the reflective film of Example 1. In Example 3, the metal reflective layer and the blackened layer on the substrate film form a multilayer film (the same applies to Example 4 described below).

Example 4
The reflective film of Example 4 was produced in the same manner as the reflective film of Example 1, except for the following: The thickness of the blackened layer formed by the second sputtering deposition in the sputtering deposition process was set to 350 nm. No HC layer was formed on the blackened layer.

<Thickness of metal reflective layer, thickness of blackened layer>
The thicknesses of the metal reflective layer and the blackening layer in each of the reflective films of Examples 1 to 4 were measured by observation with a field emission transmission electron microscope (FE-TEM). Specifically, first, samples for cross-sectional observation of the metal reflective layer and the blackening layer in Examples 1 to 4 were prepared by the FIB microsampling method. In the FIB microsampling method, an FIB device (product name "FB2200", manufactured by Hitachi) was used, and the acceleration voltage was set to 10 kV. Next, the cross-section of the metal reflective layer and the blackening layer in the cross-sectional observation sample was observed by FE-TEM, and the thickness of the metal reflective layer and the thickness of the blackening layer were measured in the observed image. In the observation, an FE-TEM device (product name "JEM-2800", manufactured by JEOL) was used, and the acceleration voltage was set to 200 kV. The measurement results are shown in Table 1.

<Visual transmittance>
The luminous transmittance of each of the reflective films of Examples 1 to 4 was measured. Specifically, the measurements were as follows.

First, a piece of film for measurement (first film piece) was cut out from the reflective film. Next, the luminous transmittance of the first film piece was measured using a spectrophotometer (product name "U-4100", manufactured by Hitachi High-Tech Science Corporation). This transmittance is the luminous transmittance (Y value) in the CIE-XYZ color system of light with wavelengths of 380 nm to 780 nm transmitted through the first film piece. In this measurement, the first film piece was placed in the spectrophotometer so that light was incident on the base film side. The measurement results are shown in Table 1.

<Visual reflectance>
The luminous reflectance of each of the reflective films of Examples 1 to 4 was measured. Specifically, the measurements were as follows.

First, the side of the reflective film opposite the base film was attached to a black acrylic plate via a specified adhesive. This resulted in a laminated film. Next, a film piece for measurement (second film piece) was cut out from the laminated film. The luminous reflectance of the second film piece was then measured using a spectrophotometer (product name "U-4100", manufactured by Hitachi High-Tech Science Corporation). This reflectance is the luminous reflectance (Y value) in the CIE-XYZ color system of light with a wavelength of 380 nm to 780 nm irradiated onto the second film piece. In this measurement, the second film piece was placed in the spectrophotometer so that light was irradiated from the base film side onto the second film piece. The measurement results are shown in Table 1.

Peel test
For each of the reflective films of Examples 1 to 4, the adhesion of the blackening layer was examined as follows.

First, a sample film was prepared for each reflective film. In preparing the sample films, a film piece (50 mm x 50 mm) was first cut out from the reflective film. Next, 11 parallel first incisions (1 mm apart) extending linearly in a first direction and 11 parallel second incisions (1 mm apart) extending linearly in a second direction perpendicular to the first direction were made in the multilayer film on the base film in the film piece, and 100 grids were formed by the first and second incisions. In this way, a sample film was obtained. Each incision reached from the exposed surface of the multilayer film to the base film in the thickness direction.

Next, a peel test (checkerboard peel test) was conducted for each sample film in accordance with JIS K 5400. Specifically, a specified single-sided adhesive tape was first applied to the multilayer surface of the sample film so as to cover all 100 squares. Next, the adhesive tape was peeled off in a first direction. The squares were then observed after the adhesive tape was peeled off to check whether or not they had peeled off. In each of the reflective films of Examples 1 to 4, the number of squares that had at least partially peeled off was 0 (no peeling had occurred in any of the squares).

The above-described embodiments are merely examples of the present invention, and the present invention should not be interpreted as being limited by these embodiments. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the claims below.

The reflective film of the present invention can be used, for example, as a reflective film placed inside the bezel of the housing of a liquid crystal display device.

X: Reflective film H: Thickness direction 10: Base film 11: First surface 12: Second surface 20: Metallic reflective layer 30: Blackened layer 40: Cured resin layer

Claims

A reflective film comprising a base film, a metal reflective layer, and a blackened layer in this order in a thickness direction,
A reflective film, wherein the blackening layer is an inorganic blackening layer containing a metal oxide and having a thickness of 400 nm or less.
The reflective film of claim 1, wherein the metal reflective layer is an aluminum layer.
The reflective film of claim 1, wherein the thickness of the metal reflective layer is 30 nm or more.
The reflective film of claim 1, wherein the thickness of the metal reflective layer is 500 nm or less.
The reflective film of claim 1, wherein the thickness of the blackening layer is 5 nm or more.
The reflective film according to claim 1, further comprising a cured resin layer on the side of the blackening layer opposite the metal reflective layer.
The reflective film according to claim 1 , wherein the blackened layer does not peel off in a peel test in accordance with JIS K 5400.