WO2024117069A1

WO2024117069A1 - Reflective film

Info

Publication number: WO2024117069A1
Application number: PCT/JP2023/042320
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: a resin film (10) that has a first surface (11) and a second surface (12) opposite to the first surface (11); and a metallic reflective layer (20) on the first surface (11). The surface roughness Ra of the first surface (11) is 50 nm or more.

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. The reflective film comprises, for example, a white resin film and a metal reflective layer on the film. The reflective film is used to prevent light from the backlight from leaking out of the bezel portion (light leakage prevention function of the reflective film). Technology relating to such reflective films is described, for example, in Patent Document 1 listed below.

JP 2004-184443 A

Anti-reflection films are required to have high reflectivity and low transmittance for light from a backlight in order to prevent light leakage. However, the inventors discovered that the low transmittance of conventional reflective films deteriorates (light transmittance increases) in high-temperature, high-humidity environments.

The present invention provides a reflective film suitable for suppressing an increase in light transmittance in high-temperature, high-humidity environments.

The present invention [1] includes a reflective film comprising a resin film having a first surface and a second surface opposite to the first surface, and a metal reflective layer on the first surface, the surface roughness Ra of the first surface being 50 nm or more.

The present invention [2] includes the reflective film described in [1] above, which has a luminous transmittance T1 (%), and has a luminous transmittance T2 (%) after a humidification test under conditions of 65°C, relative humidity 90%, and 500 hours, and the difference T2-T1 between the luminous transmittance T2 and the luminous transmittance T1 is 0.06 or less.

The present invention [3] includes the reflective film described in [1] or [2] above, in which the metal reflective layer is an aluminum layer.

The present invention [4] includes the reflective film according to any one of [1] to [3] above, in which the reflective film has a visual reflectance of 80% or more for light irradiated to the resin film side.

The present invention [5] includes the reflective film according to any one of [1] to [4] above, which has a blackening layer on the side of the metal reflective layer opposite the resin film.

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

As described above, the reflective film of the present invention has a metal reflective layer on the first surface of the resin film, and the surface roughness Ra of the first surface is 50 nm or more. In such a reflective film, migration of components (including carbon elements) derived from the resin film from the resin film to the metal reflective layer is suppressed in a high-temperature, high-humidity environment (this finding was obtained by the present inventors). The components derived from the resin film are impurities for the metal reflective layer, and suppressing the migration of such impurities to the metal reflective layer is suitable for maintaining the optical properties of the metal reflective layer. Therefore, the reflective film of the present invention is suitable for suppressing an increase in light transmittance in a high-temperature, high-humidity environment.

1 is a schematic cross-sectional view of one embodiment of a reflective film of the present invention. 1 is a schematic cross-sectional view of a modified example of the reflective film of the present invention, which includes a blackening layer on a metal reflective layer. 1 is a schematic cross-sectional view of a modified example of the reflective film of the present invention, which includes a cured resin layer on a metal reflective layer. 1 is a schematic cross-sectional view of a modified example of the reflective film of the present invention, which includes a blackening layer and a cured resin layer in this order on a metal reflective layer.

As shown in FIG. 1, the reflective film X of one embodiment of the present invention comprises a resin film 10 and a metal reflective layer 20 in this order in the thickness direction H. The reflective film X extends in a direction (plane direction) perpendicular to the thickness direction H. The 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 resin film 10 is a base material that ensures the strength of the reflective film X. The resin film 10 has a first surface 11 and a second surface 12 opposite to the first surface 11. The resin film 10 is, for example, a transparent resin film that has flexibility. Examples of the material of the resin 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 resin film 10 is preferably polyester resin, and more preferably PET.

The resin film 10 is preferably a white film from the viewpoint of ensuring significant light reflectivity of the resin 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. 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 resin 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 resin 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 resin film 10 in the roll-to-roll method, the thickness of the resin film 10 is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, even more preferably 100 μm or less, even more preferably 70 μm or less, and particularly preferably 50 μm or less.

The surface roughness Ra (arithmetic mean surface roughness based on JIS B 0601-2001) of the first surface 11 of the resin film 10 is 50 nm or more. Such a configuration is suitable for suppressing an increase in the light transmittance of the reflective film X in a high-temperature, high-humidity environment. The specific details are as described below. From the viewpoint of suppressing an increase in the light transmittance of the reflective film X in a high-temperature, high-humidity environment, the surface roughness Ra of the first surface 11 is preferably 53 nm or more, more preferably 57 nm or more, and even more preferably 60 nm or more. From the viewpoint of ensuring the uniformity of the thickness of the metal reflective layer 20, the surface roughness Ra of the first surface 11 is preferably 150 nm or less, more preferably 120 nm or less, even more preferably 100 nm or less, and even more preferably 80 nm or less. The method for measuring the surface roughness Ra is specifically as described below in the examples.

The surface roughness Ra of 50 nm or more on the first surface 11 can be achieved, for example, by subjecting the resin film 10 to a roughening treatment. Examples of roughening treatments include bombardment treatment, corona treatment, and UV treatment, with bombardment treatment being preferred.

The metal reflective layer 20 is disposed on the first surface 11 of the resin film 10. That is, 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 resin 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 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 resin film 10 side.

The luminous transmittance T1 (Y value) of the reflective film X at wavelengths of 380 nm to 780 nm in the CIE-XYZ color system is preferably less than 0.10%, more preferably 0.09% or less, even more preferably 0.08% 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 later. The luminous transmittance T1 is, for example, 0.00% or more, 0.01% or more, or 0.02% or more. The luminous transmittance T1 is the luminous transmittance of the reflective film X before the humidification test described later. The luminous transmittance of the reflective film X is the transmittance of light irradiated onto the reflective film X from the resin film 10 side. The luminous transmittance of the reflective film 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 as described later in the examples.

The luminous transmittance T2 (Y value) of the reflective film X at wavelengths of 380 nm to 780 nm in the CIE-XYZ color system after the humidification test is preferably less than 0.10%, more preferably 0.09% or less, even more preferably 0.08% 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 in a high-temperature and high-humidity environment. The luminous transmittance T2 is, for example, 0.00% or more, 0.01% or more, or 0.02% or more. The humidification test is a humidification test under conditions of 65°C, relative humidity of 90%, and 500 hours.

The difference T2-T1 between the luminous transmittance T2 (%) and the luminous transmittance T1 (%) is preferably 0.06 or less, more preferably 0.04 or less, even more preferably 0.03 or less, and even more preferably 0.02 or less, from the viewpoint of suppressing a decrease in the light leakage prevention properties of the reflective film X in a high-temperature and high-humidity environment. The difference T2-T1 is, for example, 0.00 or more or 0.01 or more. The value of the difference T2-T1 is expressed in units of "%".

Reflective film X can be manufactured, for example, as follows.

First, a resin film 10 is prepared. The first surface 11 (surface roughness Ra is 50 nm or more) of the resin film 10 is formed by a roughening treatment (roughening step). Examples of the roughening treatment include bombardment treatment, corona treatment, and UV treatment, and the bombardment treatment is preferred. In the bombardment treatment, argon (Ar) gas as an inert gas is ionized by high-frequency plasma and collided with the surface of the resin film. The air pressure in the treatment chamber during the bombardment treatment is preferably 0.01 Pa or more, more preferably 0.03 Pa or more, and also preferably 1.2 Pa or less, more preferably 1.0 Pa or less. The output (bombardment output) of the plasma generation source for the bombardment treatment is preferably 0.15 W/ ^cm2 or more, more preferably 0.19 W/cm2 or more, even more preferably 0.21 W/ ^cm2 or more, and is preferably 0.42 W/ ^cm2 or less, more preferably 0.38 W/ ^cm2 or less, even more preferably 0.35 W/ ^cm2 or ^less , from the viewpoint of achieving good surface roughening of the resin film 10. By adjusting the conditions of the bombardment treatment, the surface roughness Ra of the first surface 11 of the resin film 10 can be adjusted.

Next, a metal reflective layer 20 is formed on the resin film 10 (metal reflective layer formation process). In this process, for example, a dry coating method is used to deposit a metal material on the first surface 11 of the resin film 10 to form the metal reflective layer 20. Examples of dry coating methods include sputtering and vapor deposition, with sputtering being preferred.

In the sputtering method, for example, a sputtering device capable of performing a film formation process by a roll-to-roll method is used. When performing bombardment in the above-mentioned roughening process, a sputtering device capable of continuously performing bombardment and the subsequent film formation process while running the work film by a roll-to-roll method is used. Specifically, in the sputtering method, a sputtering gas (inert gas) is introduced under vacuum conditions into a film formation chamber equipped in the sputtering device, while a negative voltage is applied to a target placed on a cathode in the film formation 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 resin 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 a DC power source, an AC power source, an MF power source, and an RF power source. 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.

As described above, the reflective film of the present invention has a metal reflective layer 20 on the first surface 11 of the resin film 10, and the surface roughness Ra of the first surface 11 is 50 nm or more. In such a reflective film X, migration of components (including carbon elements) derived from the resin film 10 from the resin film 10 to the metal reflective layer 20 is suppressed in a high-temperature, high-humidity environment. The components derived from the resin film 10 are impurities for the metal reflective layer 20, and suppressing the migration of such impurities to the metal reflective layer 20 is suitable for maintaining the optical properties of the metal reflective layer 20. Therefore, the reflective film X is suitable for suppressing an increase in light transmittance in a high-temperature, high-humidity environment. Specifically, as shown in the examples and comparative examples described below.

The reflective film X may further include other layers on the metal reflective layer 20.

FIG. 2 shows a case where the reflective film X has a blackening layer 30 on the metal reflective layer 20. The reflective film X shown in FIG. 2 has a resin film 10, a metal reflective layer 20, and a blackening layer 30, in that order in the thickness direction H. In this modified example, the blackening layer 30 is disposed on the metal reflective layer 20. That is, the blackening layer 30 is in contact with the metal reflective layer 20 in this embodiment. From the viewpoint of the light blocking properties of the reflective film X, it is preferable that the reflective film X has a blackening layer 30.

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 preferably 400 nm or less, more preferably 200 nm or less, even 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 modified example). 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 blackening layer 30 can be formed, for example, by forming a film of a metal oxide-containing material on the metal reflective layer 20 by a dry coating method. Examples of dry coating methods include sputtering and vapor deposition. From the viewpoint of ensuring the adhesion of the blackening layer 30 to the metal reflective layer 20 as the base, the blackening layer 30 is a dry coating film formed by a dry coating method, and more preferably, a sputtered film formed by a sputtering method.

In the blackening layer formation process using the sputtering method, the target material placed on the cathode in the sputtering deposition chamber (i.e., the material of the blackening layer 30) is, 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 sputtering 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 a black ink layer formed from a resin component. In addition, the thickness of the blackening layer 30 is preferably 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 blackening layer formation process (if bombardment is performed before the metal reflective layer formation process, the entire process from the bombardment) is performed 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 blackening layer 30 on the metal reflective layer 20 after the formation of the metal reflective layer 20 without exposing the work film to the atmosphere helps to ensure adhesion of the blackening layer 30 to the metal reflective layer 20.

FIG. 3 shows a case where the reflective film X has a cured resin layer 40 on a metal reflective layer 20. The reflective film X shown in FIG. 3 has a resin film 10, a metal reflective layer 20, and a cured resin layer 40, in that order in the thickness direction H. In this modified example, the cured resin layer 40 is disposed on the metal reflective layer 20. That is, in this embodiment, the cured resin layer 40 is in contact with the metal reflective layer 20.

The cured resin layer 40 is a hard coat layer that makes the reflective film X less susceptible to scratches. From the viewpoint of the abrasion resistance of the reflective film X, it is preferable that the reflective film X has a cured resin layer 40.

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 cured resin layer 40 can be formed by applying the above-mentioned curable resin composition onto the metal reflective layer 20 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 exposure to ultraviolet light. If the curable resin composition contains a thermosetting resin, the coating film is cured by heating.

FIG. 4 shows a case where the reflective film X comprises the above-mentioned blackening layer 30 and the above-mentioned cured resin layer 40 on the metal reflective layer 20. The reflective film X shown in FIG. 4 comprises a resin 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. In this modified example, the blackening layer 30 is disposed on the metal reflective layer 20. That is, the blackening layer 30 contacts the metal reflective layer 20 in this embodiment. Also, in this modified example, the cured resin layer 40 is disposed on the blackening layer 30. That is, the cured resin layer 40 contacts the blackening layer 30 in this embodiment.

The reflective film X shown in FIG. 4 can be manufactured by forming a cured resin layer 40 on the blackened layer 30 of the reflective film X shown in FIG. 2. 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.

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 resin film.

Next, a sputtering device was used to sequentially perform a bombardment process as a roughening process on one side (first side) of the PET film and the formation of a metal reflective layer (sputtering process). A roll-to-roll sputtering device (DC magnetron sputtering device) was used in this sputtering process. This device is equipped with a pay-out chamber, a pre-treatment chamber, a film-forming chamber, and a winding chamber. The pay-out chamber is equipped with a pay-out roller. A roll of the above-mentioned resin film was set on the pay-out roller as the work film. The winding chamber is equipped with a winding roller capable of winding up the work film. With this sputtering device, the work film can be run from the pay-out chamber to the winding chamber using the roll-to-roll method, while the bombardment process in the pre-treatment chamber and the film-forming process in the film-forming chamber can be performed on the work film.

In the sputtering process, bombardment processing was carried out in the pretreatment chamber, followed by sputter deposition in the deposition chamber, after which the work film was wound up on the take-up roller in the take-up chamber. The transport speed of the work film was 3 m/min.

Specifically, in the bombardment treatment, argon (Ar) gas as an inert gas was ionized by high-frequency plasma and collided with the surface of the PET film. This roughened the first surface of the PET film. In this treatment, Ar was introduced into the pretreatment chamber after evacuating the inside of the sputtering device, and the pressure in the pretreatment chamber was set to 0.8 Pa. The output of the plasma generation source (bombardment output) was set to 0.32 W/ ^cm2 .

Specifically, in the sputtering deposition, a 75 nm thick aluminum (Al) layer was formed as a metal reflective layer on the first surface of the PET film. In this sputtering deposition, Ar was introduced as a sputtering gas into the deposition chamber after evacuating the sputtering device, and the air pressure in the 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 PET film on which the Al layer is laminated) was set to 40°C.

In this manner, the reflective film of Example 1 was produced. The reflective film of Example 1 has a laminated structure of a resin film (thickness 38 μm) and a metal reflective layer (Al layer, thickness 75 nm).

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 the surface roughening treatment of the resin film, the output of the bombardment treatment in the pretreatment chamber for sputtering deposition was set to 0.21 W/ ^cm2 . The reflective film of Example 2 has a laminated structure of a resin film (thickness 38 μm) and a metal reflective layer (Al layer, thickness 75 nm).

Example 3
The reflective film of Example 3 was produced in the same manner as the reflective film of Example 1, except for the following: A cured resin layer was further formed on the metal reflective layer. Specifically, the process is as follows.

First, a first curable resin composition was applied onto the metal reflective 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 cured resin layer.

The reflective film of Example 3 has a laminated structure of a substrate film (thickness 38 μm), a metal reflective layer (Al layer, thickness 75 nm), and a cured resin layer (thickness 1 μm).

Example 4
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 sputtering device was used to sequentially perform a bombardment process as a roughening process on one side (first side) of the PET film, the formation of a metal reflective layer, and the formation of a blackening layer (sputtering process). In this sputtering process, a roll-to-roll sputtering device (DC magnetron sputtering device) was used. This device is equipped with a pay-out chamber, a pre-treatment chamber, a first film-forming chamber, a second film-forming chamber, and a winding chamber. The pay-out chamber is equipped with a pay-out roller. A roll of the above-mentioned resin film was set on the pay-out roller as the work film. The winding chamber is equipped with a winding roller that can take up the work film. In this sputtering device, while the work film is run from the pay-out chamber to the winding chamber using a roll-to-roll method, the bombardment process in the pre-treatment chamber and the film-forming process in the first and second film-forming chambers can be performed on the work film.

In the sputtering process, bombardment in the pretreatment chamber, first sputter deposition in the first deposition chamber, and second sputter deposition in the second deposition chamber were carried out in sequence, after which the work film was wound up on the winding roller in the winding chamber. The transport speed of the work film was 3 m/min.

The bombardment treatment was carried out in the same manner as the above-mentioned bombardment treatment (output: 0.32 W/cm ² ) in Example 1. The first sputtering deposition was carried out in the same manner as the above-mentioned sputtering deposition in Example 1.

In the second sputtering deposition, Ar was introduced as a sputtering gas into the second deposition chamber after the above-mentioned evacuation of the sputtering device, 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.

In this manner, the reflective film of Example 4 was produced. The reflective film of Example 4 has a laminated structure of a substrate film (thickness 38 μm), a metal reflective layer (Al layer, thickness 75 nm), and a blackened layer (thickness 30 nm).

Example 5
The reflective film of Example 5 was produced in the same manner as the reflective film of Example 4, except for the following: A cured resin layer was further formed on the blackened layer.

First, a second curable resin composition was applied onto the blackened layer to form a coating. The second 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 cured resin layer.

In this manner, the reflective film of Example 5 was produced. The reflective film of Example 5 has a laminated structure of a substrate film (thickness 38 μm), a metal reflective layer (Al layer, thickness 75 nm), a blackening layer (thickness 30 nm), and a cured resin layer (thickness 1 μm).

Comparative Example 1
The reflective film of Comparative Example 1 was produced in the same manner as the reflective film of Example 1, except for the following. In the surface roughening treatment of the resin film, the output of the bombardment treatment in the pretreatment chamber for sputtering deposition was set to 0.11 W/ ^cm2 . The reflective film of Comparative Example 1 has a laminated structure of a resin film (thickness 38 μm) and a metal reflective layer (Al layer, thickness 75 nm).

<Thickness of metal reflective layer, thickness of blackened layer>
The thickness of the metal reflective layer in each of the reflective films of Examples 1 to 3 and Comparative Example 1, and the thickness of the metal reflective layer and the blackened layer in each of the reflective films of Examples 4 and 5 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 blackened layer in Examples 1 to 5 and Comparative Example 1 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 blackened layer in the sample for cross-sectional observation was observed by FE-TEM, and the thickness of the metal reflective layer and the thickness of the blackened 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 5 and Comparative Example 1 was measured (first transmittance measurement). Specifically, the measurement was 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 hitting the resin film side of the first film piece. The luminous transmittance (Y value) in the first transmittance measurement is shown in Table 1 as the luminous transmittance T1 before the humidification test.

Furthermore, for each of the reflective films of Examples 1 to 5 and Comparative Example 1, the luminous transmittance after the humidification test was measured (second transmittance measurement). In the humidification test, the reflective films were stored for 500 hours in an environment of 65°C and a relative humidity of 90%. The second transmittance measurement was carried out in the same manner as the first transmittance measurement. The luminous transmittance (Y value) in the second transmittance measurement is shown in Table 1 as the luminous transmittance T2 after the humidification test. The difference T2-T1 (%) between the above-mentioned luminous transmittance T1 and luminous transmittance T2 is also shown in Table 1.

<Visual reflectance>
The luminous reflectance of each of the reflective films of Examples 1 to 5 and Comparative Example 1 was measured. Specifically, the measurements were as follows.

First, the side of the reflective film opposite the resin film side 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 resin film side onto the second film piece. The measurement results are shown in Table 1.

<Surface roughness>
The surface roughness of the first surface (the surface on the metal reflective layer side) of the resin film was examined for each of the reflective films of Examples 1 to 5 and Comparative Example 1. Specifically, first, a metal reflective layer was formed on the resin film in the manufacturing process of the reflective film, and then the metal reflective layer was removed by etching. This exposed the first surface of the resin film. In the etching, an aqueous sodium hydroxide solution was used as an etching solution. Next, the surface roughness Ra (arithmetic mean surface roughness based on JIS B 0601-2001) of the first surface of the resin film was obtained from an observation image of 1 μm square using an atomic force microscope (product name "Dimention-Edge SPM SYSTEM", manufactured by Bruker). The surface roughness Ra (nm) is shown in Table 1.

<TOF-SIMS>
The metal reflective layer of each of the reflective films in Example 1 and Comparative Example 1 was subjected to component analysis by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Specifically, the results are as follows.

Specifically, a component analysis was performed in the thickness direction from the exposed surface of the metal reflective layer of the reflective film by TOF-SIMS (first analysis). A time-of-flight secondary ion mass spectrometer (name: TOF-SIMS 5, manufactured by ION-TOF) was used for the analysis. In this analysis, irradiation with an ion beam for etching and subsequent irradiation with an ion beam for measurement (primary ion beam) were alternately repeated. In the irradiation with the ion beam for etching, cesium ions (Cs ⁺ ) were used, the acceleration voltage was 1 kV, the irradiation range was 1000 μm×1000 μm, and each irradiation time was 5 seconds. In the irradiation with the ion beam for measurement, double-charged ions (Bi ₃ ⁺⁺ ) of bismuth clusters were used as the primary ions for irradiation, the acceleration voltage was 30 kV, the irradiation range was 100 μm×100 μm in the center of the area irradiated with the ion beam for etching, and a neutralization gun was used to correct the charging of the sample during analysis. In addition, this analysis was performed at room temperature.

This analysis obtained a profile (depth profile) in the depth direction (thickness direction of the metal reflective layer) of the mass spectrum of secondary ion (negative ion) intensity. Components detected as secondary ions (negative ions) in this analysis included carbon (C). The average ion intensity (counts/sec) of carbon was then determined at a depth of 5 μm or less (to the surface on the resin film side) from the exposed surface of the metal reflective layer. The average ion intensity in the first analysis is shown in Table 1 as the ion intensity F1 before the humidification test.

Furthermore, the metal reflective layer of each reflective film of Example 1 and Comparative Example 1 was subjected to a component analysis by TOF-SIMS after the humidification test (second analysis). In the humidification test, the reflective film was stored for 500 hours in an environment of 65°C and a relative humidity of 90%. The second component analysis was carried out in the same manner as the first component analysis. The average ionic strength in the second analysis is shown in Table 1 as the ionic strength F2 after the humidification test. The ratio of ionic strength F2 to the above-mentioned ionic strength F1 (F2/F1) is also shown in Table 1.

In the reflective film of Comparative Example 1, the surface roughness Ra of the first surface of the resin film (interface with the metal reflective layer) was 45.2 nm, which was relatively small. In such a reflective film, the ratio (F2/F1) of the ionic strength of the carbon element in the metal reflective layer before and after the humidification test was 3.2, and the increase in the amount of carbon (impurity) in the metal reflective layer was relatively large. This is thought to be because the smoothness of the first surface of the resin film is high, so the adhesion between the resin film and the metal reflective layer is low, so the penetration of moisture from the resin film to the metal reflective layer is not suppressed, and the carbon component in the resin film diffuses and migrates to the metal reflective layer together with moisture. Therefore, in the reflective film of Comparative Example 1, the optical properties of the metal reflective layer are significantly deteriorated by the humidification test, and the difference T2-T1 (increase in luminous transmittance) in the luminous transmittance before and after the humidification test was 0.09. In contrast, in each of the reflective films of Examples 1 to 5, the surface roughness Ra of the first surface of the resin film (interface with the metal reflective layer) is 50 nm or more. In such a reflective film, the ratio of the ionic strength of the carbon element in the metal reflective layer (F2/F1) before and after the humidification test was less than 3.0 (specifically, 2.2 or 2.7), and the increase in the amount of carbon (impurity) in the metal reflective layer was relatively small. Therefore, in each of the reflective films of Examples 1 to 5, the difference T2-T1 in luminous transmittance before and after the humidification test (increase in luminous transmittance) was suppressed to 0.06 or less.

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: Resin film 11: First surface 12: Second surface 20: Metallic reflective layer 30: Blackened layer 40: Cured resin layer

Claims

a resin film having a first surface and a second surface opposite to the first surface;
a metallic reflective layer on the first surface;
A reflective film, wherein the first surface has a surface roughness Ra of 50 nm or more.
The reflective film according to claim 1, wherein the reflective film has a luminous transmittance T1 (%), and has a luminous transmittance T2 (%) after a humidification test under conditions of 65°C, 90% relative humidity and 500 hours, and the difference T2-T1 between the luminous transmittance T2 and the luminous transmittance T1 is 0.06 or less.
The reflective film of claim 1, wherein the metal reflective layer is an aluminum layer.
The reflective film according to claim 1, wherein the reflective film has a visual reflectance of 80% or more for light irradiated to the resin film side.
The reflective film according to any one of claims 1 to 4, comprising a blackening layer on the side of the metal reflective layer opposite the resin film.
The reflective film according to claim 5 , further comprising a cured resin layer on the side of the blackening layer opposite to the metal reflective layer.