JP2023140838A - window film - Google Patents

Abstract

To provide a window film having high electromagnetic wave transmissivity of a high frequency band used in communication equipment.SOLUTION: A window film in which a base material and a metal layer are laminated in this order, wherein an adhesive layer formed from an adhesive composition is arranged adjacent to the metal layer, and the metal layer contains indium, the adhesive composition contains an acrylic copolymer, a content of an acid group-containing vinyl monomer is 5 wt.% or less in all monomers constituting the acrylic copolymer, and the content of vinyl carboxylate is 10 mass% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to window films.

In recent years, window films that are attached to the windows of buildings and vehicles have come into widespread use. Such window films, for example, have an infrared shielding ability that suppresses the intrusion of infrared rays and prevents the temperature inside a building from rising excessively, reducing the use of air conditioners and achieving energy savings. Further, window films are sometimes required to have visible light shielding properties so that the inside of the room cannot be seen from outside. Furthermore, window films are required to have radio wave transparency for the purpose of communication from the outside to indoor equipment. In recent years, various communication devices use different wavelength ranges, so radio wave transparency in a wide range of wavelengths is required. For example, in Japan's ETC system, the communication frequency band between the tollgate antenna and on-board device is 5.8 GHz, and in 5G (fifth generation mobile communication system), the frequency band in Japan is around 30 GHz. It is used. Therefore, radio wave transparency in the above frequency bands is required.

In order to provide a window film with infrared shielding properties, visible light shielding properties, and radio wave transparency, there is a technique of forming a metal layer (for example, see Patent Document 1). Aluminum is typically used as the metal for the metal layer.

In addition, window films are required to have high resistance to heat and humidity when exposed to sunlight through the glass, exposure to large temperature changes, and dew condensation.

JP2019-188798A

However, when aluminum is used as the metal of the metal layer, radio wave transparency in the above frequency band is not sufficient.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a window film that is used in communication equipment and has high radio wave transparency in a high frequency band. Another object of the present invention is to provide a window film with high heat and humidity resistance.

The present invention provides the following.

(1) A window film in which a base material and a metal layer are laminated in this order, an adhesive layer formed from an adhesive composition is disposed adjacent to the metal layer, and the metal layer contains indium, the adhesive composition contains an acrylic copolymer, and the content of the acid group-containing vinyl monomer is 5% by mass or less in all monomers constituting the acrylic copolymer. , and the content of carboxylic acid vinyl ester is 10% by mass or less.

(2) The window film according to (1), wherein the base material is transparent.

(3) The window film according to (1) or (2), further comprising a second base material on the metal layer side opposite to the base material.

(4) The window film according to any one of (1) to (3), wherein the content of the carboxylic acid vinyl ester is 5% by mass or less based on the total monomers.

(5) The window film according to any one of (1) to (4), which has a visible light transmittance of 1 to 60%.

According to the window film of the present invention, it is possible to provide a window film with high radio wave transparency in a high frequency band used in communication equipment. Moreover, a window film with high moisture and heat resistance can be provided.

FIG. 1 is a cross-sectional view of a window film according to an embodiment of the present invention. It is a sectional view of the window film of other embodiments of the present invention. It is a sectional view of a window film of still other embodiment of the present invention. This is a SEM image showing a sea-island structure of indium vapor deposition.

The present invention provides a window film in which a base material and a metal layer are laminated in this order, wherein an adhesive layer formed from an adhesive composition is disposed adjacent to the metal layer, and the metal layer is laminated in this order. contains indium, the adhesive composition contains an acrylic copolymer, the content of acid group-containing vinyl monomer is 5% by mass or less in all monomers constituting the acrylic copolymer, and carbon The content of acid vinyl ester is 10% by mass or less.

One of the performance requirements for window films is indoor shielding properties and infrared shielding properties. One way to improve these performances using a metal layer is to increase the thickness of the metal layer. However, as the thickness of the metal layer increases, the radio wave transmittance of commonly used aluminum significantly decreases. On the other hand, when indium is used as the metal, it has become possible to create a window film with high radio wave transparency while maintaining indoor shielding properties and infrared shielding properties.

However, when a metal layer containing indium is placed adjacent to an adhesive layer for adhesion, it has been confirmed that visible light transmittance cannot be maintained over time. The present inventors have discovered that the cause of this problem is that the acid present in the adjacent adhesive layer (or the acid that can be generated by hydrolysis) affects indium. Based on this knowledge, it has become possible to increase the moisture and heat resistance of window films by keeping the amount of acid (or acid that can be generated by hydrolysis) in the monomer below a certain level.

In this specification, the range "X to Y" means "more than or equal to X and less than or equal to Y." Further, unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20 to 25° C.)/relative humidity of 45 to 55% RH. Moreover, in this specification, "(meth)acrylic acid" refers to "acrylic acid or methacrylic acid", and "(meth)acrylate" refers to "acrylate or methacrylate".

Embodiments of the present invention will be described below with reference to the attached drawings. In addition, in the description of the drawings, the same elements are given the same reference numerals, and redundant description will be omitted. Furthermore, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is a cross-sectional view of a window film according to an embodiment of the present invention. Note that the drawings are exaggerated for convenience of explanation, and the dimensional ratio of each component in the drawings may be different from the actual size. In FIG. 1, a window film 10 is composed of a base material 11, a metal layer 12, an adhesive layer 13, and a release liner 14. The adhesive layer 13 is arranged for the purpose of bonding a window, which is an adherend, and a window film. The release liner 14 is a member that has the function of protecting the adhesive layer 13 and preventing a decrease in adhesiveness. The release liner 14 is then peeled off from the window film when it is applied to an adherend. Thus, window films that do not have a release liner 14 are also within the scope of the present invention.

In the form of FIG. 1, the window film 10 is composed of a base material 11, a metal layer 12, an adhesive layer 13, and a release liner 14. As long as the metal layer 12 and the adhesive layer 13 are arranged in this order, and the metal layer 12 and the adhesive layer 13 are arranged adjacent to each other, other functional layers (for example, a printing layer, a surface protection layer, an antistatic layer, an adhesion improving layer, etc. layer, light shielding layer, antireflection layer, stress relaxation layer, antifogging layer, antifouling layer, infrared absorbing layer, infrared reflective layer, ultraviolet reflective layer, etc.) may be present.

FIG. 2 is a cross-sectional view of a window film according to another embodiment of the present invention. In FIG. 2, the window film 20 is composed of a base material 11, an adhesive layer 13, a metal layer 12, a second base material 15, a second adhesive layer 16, and a release liner 14. By arranging the second base material 15, it is possible to suppress the corrosion of the metal layer due to the intrusion of water used when applying water, for example, and it is possible to improve the moisture and heat resistance. In this embodiment, the adhesive layer 13 is arranged for the purpose of adhering the base material 11 and the metal layer 12, and the second adhesive layer 16 is arranged for the purpose of adhering the window which is the adherend and the window film. It will be placed in

FIG. 3 is a cross-sectional view of a window film according to yet another embodiment of the present invention. In FIG. 3, the window film 30 is composed of a base material 11, a metal layer 12, an adhesive layer 13, a second base material 15, a second adhesive layer 16, and a release liner 14. By arranging the second base material 15, it is possible to suppress the corrosion of the metal layer due to the intrusion of water used when applying water, for example, and it is possible to improve the moisture and heat resistance. In this embodiment, the adhesive layer 13 is arranged for the purpose of adhering the metal layer 12 and the second base material 15, and the second adhesive layer 16 is arranged for adhering the window which is the adherend and the window film. placed for the purpose of

Hereinafter, the constituent members of the window film of the present invention will be explained below.

(Base material)
The material forming the base material is not particularly limited, but a resin base material is preferred. The base material may be a single layer or a laminated film of two or more layers.

The resin base material may be a stretched film such as a uniaxially stretched film or a biaxially stretched film, or may be an unstretched film, or may be formed using a process material by a casting method or the like. .

The base material is preferably transparent because visible light and infrared rays can be reflected by the metal layer. Here, transparent means that the total light transmittance is 80% or more, preferably 90% or more (upper limit: 100%). Here, the transmittance of the base material can be measured according to JIS K7361-1:1997 (Test method for total light transmittance of plastic transparent materials).

The material constituting the resin base material is not particularly limited, and examples include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyethylene, polypropylene, poly4-methylpentene-1, polybutene-1, and the like. Polyolefin resins; cellulose resins such as cellophane, diacetylcellulose, triacetylcellulose, and acetylcellulose butyrate; polyvinyl chloride resins; polyvinylidene chloride resins; polyvinyl alcohol resins; polystyrene resins; polycarbonate resins; polysulfone resins Examples include resins; fluorine resins; acrylic resins; cyclic olefin resins such as norbornene resins; polyamide resins; styrene resins. Among these, from the viewpoint of transparency, the material constituting the resin base material is preferably polyester or polyolefin, more preferably polyethylene terephthalate, polyethylene, or polypropylene, and even more preferably polyethylene terephthalate. .

The base material contains stabilizers, lubricants, fillers, colorants, processing aids, softeners, metal powder, antifogging agents, ultraviolet absorbers, antioxidants, antistatic agents, flame retardants, etc., as necessary. may be included as appropriate.

The thickness of the base material may be, for example, 5 to 100 μm, 7 to 50 μm, or 10 to 30 μm. It is preferable that the base material has a degree of transparency that allows visible light to pass therethrough.

Further, regarding the second base material as well, specific examples of material and thickness, and preferred embodiments are the same as those for the above-mentioned base material.

(metal layer)
The metal layer contains indium as a main component. Here, "containing as a main component" refers to containing indium in the metal layer in an amount of 80% by mass or more (up to 100% by mass), preferably 90% by mass or more, more preferably It is 95% by mass or more, particularly preferably 100% by mass. Indium here refers to indium alone, and does not include compounds with other elements such as indium oxide.

The metal layer may contain other additives in addition to indium. Examples of additives include metals other than indium (eg, aluminum, gold, silver, copper, nickel, cobalt, chromium, tin, zinc, etc.), metal oxides, silicon dioxide, and the like.

The metal layer may or may not be provided in direct contact with one surface of the base material or the second base material. For example, an anchor coat layer, which is a cured product of a coating agent, may be formed on one surface of the (second) base material in order to improve the adhesion between the (second) base material and the metal layer. In this case, the metal layer is formed further above the anchor coat layer formed on one surface of the (second) base material, and the metal layer and the (second) base film do not come into direct contact.

The thickness of the metal layer is preferably such that visible light can be transmitted through it.

As an example, the thickness of the metal layer may be 1 nm or more and 1000 nm or less, 1 nm or more and 500 nm or less, 1 nm or more and 200 nm or less, or 10 nm or more and 100 nm or less.

The thickness of the metal layer can be determined as the average value obtained by measuring the thickness at 10 randomly selected locations.

Moreover, the thickness of the metal layer can be determined based on the value of visible light transmittance. In the present invention, it is preferable to appropriately set the thickness of the metal layer so that the visible light transmittance is within a preferable range of 1 to 60% as described below.

Examples of methods for forming the metal layer include vapor deposition, sputtering, and the like. Examples of the vapor deposition method include resistance heating vacuum evaporation, electron beam heating vacuum evaporation, ion plating, and ion beam assisted vacuum evaporation. In a preferred embodiment of the present invention, the metal layer is an indium vapor deposited layer.

Moreover, it is preferable that the metal layer has a sea-island structure. With such a sea-island structure, radio wave transparency is further improved. The sea-island structure is an island structure in which flattened indium particles are attached to the surface of the base material, and the base material is exposed without indium particles attached, creating gaps between the island parts. (See FIG. 4). The sea-island structure formed by indium on the surface of the base material can be confirmed using a scanning electron microscope (SEM) or the like. A method of forming a sea-island structure using indium by a vapor deposition method can be performed using a method disclosed in Japanese Patent Application Laid-Open No. 2021-066022. In addition, the visible light transmittance of the laminate of the metal layer (indium vapor deposited layer) obtained by the vapor deposition process and the holding film (for example, the base material) was measured, and the visible light transmittance of the laminate was 1% to 60%. It is preferable to control the formation rate of the indium vapor deposition layer so that the indium vapor deposition layer is formed.

(Adhesive layer)
The adhesive layer is disposed adjacent to the metal layer. It may be placed on the base material side of the metal layer or on the opposite side of the metal layer to the base material. Alternatively, they may be placed on both sides.

<Acrylic copolymer>
The adhesive composition contains an acrylic copolymer. Further, the acrylic copolymer is obtained by copolymerizing the constituent monomers.

Acrylic copolymers contain alkyl (meth)acrylate as the main monomer component, and if necessary, use monomers that can be copolymerized with alkyl (meth)acrylate (copolymerizable monomers). It is formed. Here, the main component refers to 50% by mass or more in the monomer, preferably 65% by mass or more (upper limit 100% by mass), more preferably 85% by mass or more, and even more preferably 90% by mass. The content is most preferably 95% by mass or more. The content of alkyl (meth)acrylate in all monomers is, for example, 99% by mass or less, and may be 98% by mass or less.

The alkyl group of the alkyl (meth)acrylate may be a linear, branched, or cyclic alkyl group. The alkyl group is preferably an alkyl group having 1 to 24 carbon atoms, more preferably an alkyl group having 1 to 18 carbon atoms.

Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, Isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylate ) Decyl acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, and the like. These may be used alone or in combination of two or more. Among them, from the viewpoint of adhesiveness, it is preferable to use n-butyl (meth)acrylate and/or 2-ethylhexyl (meth)acrylate, more preferably to use n-butyl (meth)acrylate, and Even more preferred is the use of n-butyl. One preferred form is that n-butyl (meth)acrylate and/or 2-ethylhexyl (meth)acrylate is contained in a proportion of 50% by mass or more (more preferably 65% by mass or more, more preferably 85% by mass) based on the total amount of monomers. % or more, even more preferably 90% by mass or more). The content of n-butyl (meth)acrylate and/or 2-ethylhexyl (meth)acrylate is, for example, 99% by mass or less, and may be 98% by mass or less, based on the total monomers.

Further, as the monomer constituting the acrylic copolymer, it is preferable to use a hydroxyl group-containing monomer from the viewpoint of improving the cohesive force of the adhesive and the adhesion to the base material. Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and glycerin dimethacrylate. Examples include. These may be used alone or in combination of two or more. The hydroxyl group-containing monomer may be contained in an amount of 0.1 to 20% by mass, or 1 to 10% by mass, based on the total monomers.

The content of the acid group-containing vinyl monomer in all the monomers constituting the acrylic copolymer is 5% by mass or less. When the content of the acid group-containing vinyl monomer exceeds 5% by mass, deterioration (increase in total light transmittance) in a moist heat environment is observed, and the initial optical properties of the film cannot be maintained. The content of the acid group-containing vinyl monomer in the total monomers is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. , 0.1% by mass or less is particularly preferred, and most preferably 0.05% by mass or less. In addition, a very small amount of acid group-containing vinyl monomer may be used in order to advance the crosslinking reaction, and specifically, the content of acid group-containing vinyl monomer in all the monomers constituting the acrylic copolymer is is preferably 0.01 to 5% by mass, more preferably 0.01 to 3% by mass, even more preferably 0.01 to 1% by mass, and even more preferably 0.01 to 0. It is even more preferably 5% by weight, particularly preferably 0.01-0.1% by weight, most preferably 0.01-0.05% by weight.

Acid group-containing vinyl monomers include carboxyl group-containing vinyl monomers (ethylenic double bonds and Compounds containing carboxylic anhydride groups in the same molecule); Vinyl monomers containing carboxylic anhydride groups such as maleic anhydride and itaconic anhydride (compounds having ethylenic double bonds and carboxylic anhydride groups in the same molecule); Acrylic monomers having a phosphoric acid group such as 2-methacryloyloxyethyl diphenyl phosphate (meth)acrylate, trimethacryloyloxyethyl phosphate (meth)acrylate, and triacryloyloxyethyl phosphate (meth)acrylate; Examples include acrylic monomers having a sulfonic acid group such as sodium propyl (meth)acrylate, sodium 2-sulfoethyl (meth)acrylate, and sodium 2-acrylamido-2-methylpropanesulfonate.

Moreover, the content of carboxylic acid vinyl ester is 10% by mass or less in all the monomers constituting the acrylic copolymer. When the content of carboxylic acid vinyl ester exceeds 10% by mass, deterioration (increase in total light transmittance) in a moist heat environment is observed, and the initial optical properties of the film cannot be maintained. The content of carboxylic acid vinyl ester in all monomers is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and 0. It is even more preferably 5% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

Carboxylic acid vinyl ester is an ester of carboxylic acid and vinyl alcohol. Specific examples of carboxylic acid vinyl esters include vinyl acetate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl chloroacetate, divinyl adipate, etc. can be mentioned.

The monomer constituting the acrylic copolymer may also contain other copolymerizable monomers that can be copolymerized with alkyl (meth)acrylate. Examples of copolymerizable monomers that can be copolymerized with alkyl (meth)acrylate include amide group-containing monomers such as acrylamide, methacrylamide, N-vinylpyrrolidone, and N,N-dimethylacrylamide; Examples include amino group-containing monomers such as aminoethyl acrylate and (meth)acryloylmorpholine; aromatic vinyl compounds such as styrene and substituted styrene; and cyano group-containing monomers such as acrylonitrile. These may be used alone or in combination of two or more.

When using other copolymerizable monomers, it is preferably 5% by mass or less (lower limit 0% by mass), more preferably 3% by mass or less, and 1% by mass or less based on the total monomers. Even more preferably, it is particularly preferably substantially free. Here, "substantially not contained" means that the content of impurities is allowed, and specifically, it is 0.01% by mass or less, and further, 0% by mass.

The weight average molecular weight of the acrylic copolymer is not particularly limited, but is preferably from 100,000 to 1,000,000. The weight average molecular weight is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

The content of the acrylic copolymer in the adhesive composition is preferably 50 to 100% by mass, more preferably 60 to 100% by mass.

The method for producing the acrylic copolymer is not particularly limited, and conventional methods such as solution polymerization using a polymerization initiator, emulsion polymerization, suspension polymerization, reversed-phase suspension polymerization, thin film polymerization, and spray polymerization can be used. Known methods can be used. In addition to the method of starting polymerization using a polymerization initiator, a method of starting polymerization by irradiating with radiation, electron beams, ultraviolet rays, etc. can also be adopted.

<Other ingredients>
The adhesive composition may contain a crosslinking agent. As the crosslinking agent, known crosslinking agents can be used. Examples include, but are not limited to, isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, aziridine crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, and the like. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of reactivity.

The crosslinking agent may be used alone or in the form of a mixture of two or more.

When adding a crosslinking agent, the amount of the crosslinking agent added is preferably 0.1 to 10 parts by weight, and preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer. More preferred.

The adhesive composition may further contain other conventionally known additives. Examples of such additives include fillers, pigments, and ultraviolet absorbers. Examples of the filler include zinc white, silica, and calcium carbonate.

<Formation method>
The method for forming the adhesive layer is not particularly limited, but the adhesive layer may be formed by directly coating the adhesive composition on the (second) base material, or on the release liner. After forming an adhesive layer on the adhesive layer, this may be bonded to a metal layer (a laminate containing the adhesive layer), a second base material, and the like.

The method of applying the adhesive composition to the base material or release liner is not particularly limited, and for example, a known method such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater can be used. Coating can be performed using a coating device. Drying conditions are not particularly limited, and are usually carried out at 60 to 150°C for 10 to 60 seconds.

The thickness of the adhesive layer (film thickness after drying) is usually 5 to 100 μm, preferably 10 to 50 μm.

(Second adhesive layer)
The adhesive used in the second adhesive layer is not particularly limited, and includes acrylic adhesive, rubber adhesive, silicone adhesive, urethane adhesive, polyester adhesive, and styrene-diene block copolymer adhesive. A vinyl alkyl ether adhesive or the like can be used. The above adhesives may be used alone or in combination of two or more.

Furthermore, the same adhesive composition as that for the adhesive layer may be used for the second adhesive layer.

(Hard coat layer)
In the present invention, a hard coat layer may be provided on the surface of the base material opposite to the metal layer side. The hard coat layer is provided to improve scratch resistance and is provided on the outermost surface of the film.

The hard coat layer is, for example, a cured product of a hard coat agent obtained by applying the hard coat agent to the surface of the base material opposite to the pressure-sensitive adhesive layer. Hard coating agents include dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, tetramethylolmethane acrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate, Examples include polyfunctional acrylate monomers such as ditrimethylolpropane tetraacrylate, pentaerythritol tetramethacrylate, and ditrimethylolpropane tetramethacrylate, and polyfunctional acrylate oligomers such as urethane acrylate, polyester acrylate, and epoxy acrylate.

The provision of the hard coat layer reduces the susceptibility of the window film to scratches, so it is also excellent in that it is less likely to be scratched even when the surface of the window film is rubbed with a squeegee.

The hard coat layer may contain an infrared shielding metal compound. Examples of infrared-shielding metal oxides include, but are not limited to, zinc oxide, tungsten oxide, antimony-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), gallium-doped zinc oxide (GZO), and aluminum-doped zinc oxide. Examples include zinc oxide, tin oxide, antimony-doped tin oxide (ATO), and indium-doped tin oxide (ITO). These may be used alone or in combination of two or more. The content of the infrared shielding metal compound in the hard coat layer is, for example, 10 to 60% by mass.

(Visible Light Transmittance)
The upper limit of the visible light transmittance of the window film is preferably 60% or less, more preferably 40% or less. When the visible light transmittance is below the above upper limit, the infrared reflectance is high and the shielding coefficient can be made small. Furthermore, the thicker the metal layer, the lower the visible light transmittance, but the thicker the metal layer, the lower the radio wave transmittance. On the other hand, according to the configuration of the present application, high radio wave transmittance can be maintained even if the visible light transmittance is 60% or less.

The lower limit of the visible light transmittance of the window film is preferably 1% or more, more preferably 2% or more. When the lower limit of the visible light transmittance is equal to or higher than the above lower limit, the amount of attenuation of radio waves is less likely to decrease as much as that of glass, and the detection degree of radio waves can be maintained at the same level as that of glass.

The visible light transmittance of the window film is preferably 1 to 60%, more preferably 2 to 40%.

(Infrared reflectance)
The infrared reflectance of the window film is preferably 5% or more, more preferably 10% or more. When the infrared reflectance of the window film is at least the above lower limit, it has sufficient heat shielding properties. Further, the infrared reflectance of the window film is, for example, 80% or less.

(Release liner)
The release liner is a member that protects the adhesive layer and prevents the adhesive from decreasing. Then, the release liner is peeled off from the adhesive sheet when it is attached to an adherend. Therefore, the window film according to the present invention includes a window film that does not have a release liner.

Release liners include, but are not limited to, polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; plastic films such as polyolefin films such as polypropylene and polyethylene; high-quality paper, glassine paper, and clay coated paper. , paper such as polyethylene laminated paper; and the like.

The thickness of the release liner is usually about 10 to 400 μm. Furthermore, a layer made of a release agent made of silicone or the like may be provided on the surface of the release liner to improve the releasability of the adhesive layer. When such a layer is provided, the thickness of the layer is usually about 0.01 to 5 μm.

(Application)
The window film of the present invention can be used as various window films such as a heat-shielding film, an anti-scattering film, and a UV-shielding film. Further, the window film of the present invention can be applied to windows of buildings, vehicles (for example, vehicles), and the like. Examples of vehicles include cars, trains, streetcars, and the like. When a window film is applied to a car window, examples of the car window glass to which the film is applied include a windshield, a rear glass, a front bench glass, a front door glass, a rear door glass, a rear quarter glass, and a rear side glass. Among the automobile window glasses listed above, rear glass, rear door glass, rear quarter glass, and rear side glass are preferred. Furthermore, suitable materials for forming the window include, for example, glass, glass substitute resin, and the like. Glass substitute resins are not particularly limited, and include polycarbonate resins, polysulfone resins, acrylic resins, polyolefin resins, polyether resins, polyester resins, polyamide resins, polysulfide resins, unsaturated polyester resins, epoxy resins, melamine resins, phenolic resins, Examples include diallyl phthalate resin, polyimide resin, styrene resin, and vinyl chloride resin.

The effects of the present invention will be explained using the following examples and comparative examples. In the examples, "parts" or "%" may be used, but unless otherwise specified, "parts by mass" or "% by mass" is indicated. Furthermore, unless otherwise specified, each operation is performed at room temperature (25° C.).

(Example 1)
1. Preparation of base material and adhesive layer laminate Monomer composition: n-butyl acrylate (n-BA)/2-hydroxyethyl methacrylate (2-HEMA)/methacrylic acid (MAAc) = 93.76/6. 2/0.04 (mass ratio) of an acrylic copolymer (weight average molecular weight: 400,000) toluene solution (solid content: 40% by mass), solid content: 100 parts by mass, isocyanate crosslinking agent Coronate ( 1 part by mass (solid content) of HL (registered trademark) HL (manufactured by Tosoh Corporation) was added to obtain an adhesive composition.

The obtained adhesive composition was coated on a transparent base PET film (thickness 25 μm, Lumirror (registered trademark) T60 (manufactured by Toray Industries, Inc.) using a knife coater so that the film thickness after drying was 10 μm, It was then dried to obtain an adhesive layer.

A hard coat layer was formed on the side of the PET film opposite to the pressure-sensitive adhesive layer forming side in the following manner.

(Formation of hard coat layer)
100 parts by mass of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd., Aronix M-305), 10 parts by mass of a photopolymerization initiator (manufactured by IGM Resins, Omnirad 184), and silicone as a silicone leveling agent. (manufactured by Dow Toray Industries, Inc., DOWSIL 8032 Additive) 0.3 parts by mass and diluted with 80 parts by mass of methyl ethyl ketone and 80 parts by mass of toluene as diluting solvents to prepare a hard coat layer forming material (solid content concentration 40% by mass) did.

The hard coat layer forming material was applied onto the PET film so that the film thickness after drying was 2 μm. Thereafter, using a high-pressure mercury lamp, ultraviolet rays were irradiated at 100 mJ/cm ² to photocure the hard coat layer forming material to form a hard coat layer.

2. Preparation of second base material and metal layer laminate A transparent PET film (thickness 25 μm, Lumirror (registered trademark) T60 (manufactured by Toray Industries, Inc.) as a second base material was coated with indium as shown in Table 1. A metal layer was formed on the second base material by vapor deposition so as to have a light transmittance.

3. Preparation of Second Adhesive Layer and Release Liner Laminate The above adhesive composition was coated on the release liner using a knife coater so that the film thickness after drying was 20 μm to obtain a second adhesive layer.

4. Formation of laminate: 1. Formation of laminate: base material - adhesive layer - metal layer - second base material - second adhesive layer - release liner. , 2. and 3. The laminates obtained were laminated to obtain a window film.
(Example 2)
A window film was obtained in the same manner as in Example 1, except that indium was vapor-deposited so as to have the visible light transmittance shown in Table 1.

(Example 3)
A window film was obtained in the same manner as in Example 1, except that indium was vapor-deposited so as to have the visible light transmittance shown in Table 1.

(Comparative example 1)
A window film was obtained in the same manner as in Example 1, except that aluminum was vapor-deposited so as to have the visible light transmittance shown in Table 1.

(Comparative example 2)
A forming material for forming a hard coat layer in which 40 parts by mass of indium tin oxide (ITO) was further added in Example 1 on a PET film (thickness 25 μm, Lumirror (registered trademark) T60 (manufactured by Toray Industries, Inc.) as a transparent base material. A hard coat layer was formed using the PET film of the laminate.The surface of the second adhesive layer of the laminate of the second adhesive layer and release liner prepared in Example 1 was transferred to the base material to form a window film. was created.

[Evaluation method 1: Visible light transmittance]
It was measured according to the test method described in JIS A5759:2016 (Film for architectural window glass - Visible light transmittance test). Note that measurements were taken with the glass surface of the test piece facing the light source.

[Evaluation method 2: Infrared reflectance]
The infrared reflectance value was measured using a spectrophotometer (UV-3600, manufactured by Shimadzu Corporation), and the average infrared reflectance in the range of 780 to 2500 nm was defined as the infrared reflectance.

[Evaluation method 3: Shielding coefficient]
It was measured according to the test method described in JIS A5759:2016 (film for architectural window glass).

[Evaluation method 4: Radio wave transparency]
The prepared sheet sample was attached to a 3 mm float glass, and the amount of attenuation (dB) at each frequency (5.8 GHz, 28 GHz) was measured using a network analyzer ("N5222B" manufactured by Keysight) to calculate the amount of radio wave attenuation.

The results are shown in Table 1 below.

From the above results, the window film of the example has a high visible light shielding property with a visible light transmittance of 60% or less, an infrared reflectance of 10% or more, which guarantees infrared shielding property, and radio wave transmittance. is high. On the other hand, although the window film of Comparative Example 1 had a visible light transmittance of 60% or less and an infrared reflectance of 10% or more, the radio wave transmittance was significantly reduced. Furthermore, although the window film of Comparative Example 2 had high radio wave transmittance, it was not sufficient in terms of indoor shielding properties and infrared shielding properties.

(Example 4)
Other than using an acrylic copolymer whose monomer composition is n-butyl acrylate/vinyl acetate/2-hydroxyethyl methacrylate/methacrylic acid = 88.76/5/6.20/0.04. A window film was obtained in the same manner as in Example 2.

(Example 5)
Other than using an acrylic copolymer whose monomer composition is n-butyl acrylate/vinyl acetate/2-hydroxyethyl methacrylate/methacrylic acid = 83.76/10/6.20/0.04. A window film was obtained in the same manner as in Example 2.

(Comparative example 3)
Other than using an acrylic copolymer whose monomer composition is n-butyl acrylate/vinyl acetate/2-hydroxyethyl methacrylate/methacrylic acid = 78.76/15/6.20/0.04. A window film was obtained in the same manner as in Example 2.

(Comparative example 4)
A window film was obtained in the same manner as in Example 2, except that an acrylic copolymer having a monomer composition of n-butyl acrylate/acrylic acid = 90/10 was used.

[Evaluation method 5: Total light transmittance]
It was measured according to the test method described in JIS K7361-1:1997 (Test method for total light transmittance of plastic transparent materials). After each sample was attached to a 3 mm float glass, the total light transmittance (TT) was measured at 60° C. and 95% RH after 3 days and 10 days. The results are shown in Table 2 below.

From the above results, compared to the window film of the comparative example, the difference in total light transmittance between the window film of the example and the initial state was smaller even after storage in a heat-and-moisture environment. Therefore, it can be seen that the window film of the example has high moisture and heat resistance.

10, 20, 30 window film,
11 base material,
12 metal layer,
13 adhesive layer,
14 release liner,
15 second base material,
16 Second adhesive layer.

Claims (5)

A window film in which a base material and a metal layer are laminated in this order,
An adhesive layer formed from an adhesive composition is disposed adjacent to the metal layer,
the metal layer contains indium,
The adhesive composition contains an acrylic copolymer,
A window film in which the content of acid group-containing vinyl monomer is 5% by mass or less and the content of carboxylic acid vinyl ester is 10% by mass or less among all monomers constituting the acrylic copolymer. . The window film of claim 1, wherein the substrate is transparent. The window film according to claim 1 or 2, further comprising a second base material on the opposite side of the metal layer to the base material. The window film according to any one of claims 1 to 3, wherein the content of the carboxylic acid vinyl ester is 5% by mass or less based on the total monomers. The window film according to any one of claims 1 to 4, having a visible light transmittance of 1 to 60%.