JP7793445B2 - Security window film - Google Patents

Description

The present invention relates to a security window film.

Window film is an adhesive film applied to the window glass of vehicles such as automobiles, ships, and trains, as well as buildings such as houses, apartments, and office buildings. It is widely used for purposes such as blocking ultraviolet and/or infrared rays in sunlight, protecting privacy, preventing crime, preventing glass from shattering, and providing decoration.

In particular, security window films have been launched to prevent crimes such as burglaries that involve breaking into buildings through windows. By applying the film to windows, the destruction and penetration of glass openings is significantly delayed, thereby providing security for buildings.

Increasing the overall thickness of security window films by increasing the number of films laminated or by increasing the thickness of the laminated films is effective in improving security performance, such as tear strength and tensile strength. (See, for example, Patent Document 1.)

However, if the overall thickness of the film is increased, the hard coat layer will be subjected to strong forces when it is rolled up for storage and transportation, or when it is applied to the window glass as it is harder than other window films that are not for security purposes.

As a result, cracks may appear in the hard coat layer, causing problems such as a deterioration in appearance.

Japanese Patent Application Laid-Open No. 2019-126953

The object of the present invention is to provide a security window film equipped with a hard coat layer that has excellent abrasion resistance and can effectively prevent cracks from occurring in the hard coat layer even when wound into a roll or subjected to strong force during installation.

Such an object can be achieved by the present invention described below.
The security window film of the present invention comprises a laminate in which a plurality of films made of a material containing polyethylene terephthalate are laminated via adhesive layers, a hard coat layer made of a material containing a (meth)acrylate resin and disposed on one side of the laminate, and an adhesive layer for adhering to an adherend, disposed on the side of the laminate opposite to the side on which the hard coat layer is disposed;
The (meth)acrylate resin has, as constituent components , a urethane (meth)acrylate as an oligomer and a hexafunctional (meth)acrylate as a monomer ,
a proportion of the hexafunctional (meth)acrylate in the (meth)acrylate resin is 15% by mass or more and 40% by mass or less;
The (meth)acrylate resin is characterized in that the proportion of the urethane (meth)acrylate is 60% by mass or more and 85% by mass or less .

In the present invention, the laminate preferably includes three or more layers of the film.
In the present invention, it is preferable that the thickness of each of the films is 80 μm or more and 120 μm or less.

In the present invention, the overall thickness is preferably 350 μm or more and 500 μm or less.
In the present invention, the thickness of the hard coat layer is preferably 0.1 μm or more and 20 μm or less.

The present invention provides a security window film equipped with a hard coat layer that has excellent abrasion resistance and can effectively prevent cracks from occurring in the hard coat layer even when wound into a roll or subjected to strong force during installation.

1 is a cross-sectional view showing one example of the configuration of the security window film of the present invention.

Preferred embodiments of the present invention will be described in detail below.
[1] Crime Prevention Window Film FIG. 1 is a cross-sectional view showing an example of the construction of the crime prevention window film of the present invention.

The security window film 1 comprises a laminate 10 formed by stacking multiple films (in the illustrated configuration, three films: a first PET film 11, a second PET film 13, and a third PET film 15) made of a material containing polyethylene terephthalate via adhesive layers (in the illustrated configuration, first adhesive layer 12 and second adhesive layer 14); a hard coat layer 2 made of a material containing a (meth)acrylate resin and disposed on one side of the laminate 10; and an adhesive layer 3 for adhering to an adherend and disposed on the side of the laminate 10 opposite the side on which the hard coat layer 2 is disposed. The (meth)acrylate resin constituting the hard coat layer 2 contains urethane (meth)acrylate and a hexafunctional (meth)acrylate as constituent components, and the proportion of the hexafunctional (meth)acrylate in the (meth)acrylate resin is 15% by mass or more and 40% by mass or less.

The (meth)acrylate resin that constitutes the hard coat layer 2 contains a constituent component, particularly a urethane (meth)acrylate as an oligomer component, which imparts flexibility to the hard coat layer 2 and helps prevent cracks from occurring in the hard coat layer 2. Furthermore, the (meth)acrylate resin contains a constituent component, particularly a hexafunctional (meth)acrylate as a constituent monomer, which allows the hard coat layer 2 to have excellent curability and contributes to excellent abrasion resistance.

The proportion of the hexafunctional (meth)acrylate in the (meth)acrylate resin that constitutes the hard coat layer 2 is 15% by mass or more and 40% by mass or less.

This allows the hard coat layer 2 to have sufficiently excellent curing properties and scratch resistance, while also having excellent crack resistance. As a result, even when the hard coat layer 2 is wound into a roll during transportation or when strong forces are applied during installation, scratches and cracks are less likely to occur in the hard coat layer 2, making it possible to provide a window film 1 with high security.

On the other hand, if the above conditions are not met, satisfactory results will not be obtained.
For example, if the (meth)acrylate resin constituting the hard coat layer does not contain urethane (meth)acrylate as a constituent component, the hard coat layer cannot be imparted with sufficient flexibility, and the window film will have poor crack resistance.

Furthermore, if the (meth)acrylate resin constituting the hard coat layer does not contain a hexafunctional (meth)acrylate as a constituent component, or if it does contain one but the content is below the lower limit, the abrasion resistance of the hard coat layer will not be sufficiently excellent.

Furthermore, if the content of hexafunctional (meth)acrylate in the (meth)acrylate resin constituting the hard coat layer exceeds the upper limit, the hard coat layer will not be able to be imparted with sufficient flexibility, and the window film will have poor crack resistance.

As described above, the proportion of the hexafunctional (meth)acrylate in the (meth)acrylate resin constituting the hard coat layer 2 may be 15% by mass or more and 40% by mass or less, preferably 18% by mass or more and 35% by mass or less, and more preferably 20% by mass or more and 30% by mass or less.
This makes it possible to make the above-mentioned effects more pronounced.

[1-1] Laminate The laminate 10 is formed by laminating a plurality of films made of a material containing polyethylene terephthalate with pressure-sensitive adhesive layers interposed therebetween.

In the following description, films made from materials containing polyethylene terephthalate may be referred to as "PET film."

In the illustrated configuration, the laminate 10 includes three layers of PET films: a first PET film 11, a second PET film 13, and a third PET film 15.

Thus, the laminate 10 preferably includes three or more layers of PET film.
This allows the security window film 1 to have better security performance such as tear strength and breaking strength.

On the other hand, if the number of PET films is too large, the overall thickness of the security window film 1 will increase, which may result in problems such as reduced processability, such as difficulty in winding it into a roll during production, or the film may become too hard during use, making it difficult to handle and difficult to install.

For this reason, it is preferable that the number of PET film layers contained in the laminate 10 be six or less, and more preferably five or less.

This allows the security window film 1 to achieve high levels of security performance while also being easy to process and install. It is also advantageous from the perspective of improving the productivity of the security window film 1 and reducing the production costs of the security window film 1.

In the following explanation, we will focus on the illustrated configuration in which the laminate 10 has three layers of PET film, but the present invention is not limited to this, and the number of PET film layers in the laminate 10 may be two, four or more.

In addition, in the illustrated configuration, the adhesive layers that bond adjacent PET films that make up the laminate 10 include a first adhesive layer 12 and a second adhesive layer 14. That is, in the illustrated configuration, the adhesive layers that bond adjacent PET films that make up the laminate 10 include a first adhesive layer 12 that bonds the first PET film 11 and the second PET film 13, and a second adhesive layer 14 that bonds the second PET film 13 and the third PET film 15. In other words, in the illustrated configuration, the laminate 10 has a structure in which the first PET film 11, the first adhesive layer 12, the second PET film 13, the second adhesive layer 14, and the third PET film 15 are laminated in this order.

In the security window film 1 shown in Figure 1, a hard coat layer 2 is disposed on one side of the laminate 10, in other words, on the first PET film 11, and an adhesive layer (third adhesive layer) 3 is disposed on the side of the laminate 10 opposite to the side on which the hard coat layer 2 is disposed, in other words, on the third PET film 15.

[1-1-1] PET Films The PET films constituting the laminate 10 (i.e., the first, second, and third PET films 11, 13, and 15) are films that are present on the substrate after the security window film 1 is attached to the substrate, and that substantially contribute to the security performance of the security window film 1.

The PET films that make up the laminate 10 (i.e., the first, second, and third PET films 11, 13, and 15) are made of a material containing polyethylene terephthalate, and preferably are made primarily of polyethylene terephthalate.

This further improves the security performance of the security window film 1. It also improves the handling properties of the security window film 1, improving the workability of attaching the security window film 1 to an adherend. It also makes it possible to ensure that the security window film 1 has sufficiently excellent transparency.

In this specification, "mainly" refers to the part with the highest content among the target parts.

In particular, the polyethylene terephthalate content in the PET films constituting the laminate 10 (i.e., the first, second, and third PET films 11, 13, and 15) is preferably 90% by mass or more, and more preferably 95% by mass or more.

The PET films constituting the laminate 10 (i.e., the first, second and third PET films 11, 13 and 15) are preferably biaxially stretched.
This makes the PET film less susceptible to shrinkage and has high bending rigidity.

The PET films that make up the laminate 10 (i.e., the first, second, and third PET films 11, 13, and 15) can be produced, for example, by producing an unstretched resin film using a known method such as T-die extrusion molding, and then using a known method such as sequential biaxial stretching or simultaneous biaxial stretching.

The thickness of each PET film (i.e., the first, second, and third PET films 11, 13, and 15) that constitutes the laminate 10 is preferably 80 μm or more and 120 μm or less, more preferably 85 μm or more and 115 μm or less, and even more preferably 90 μm or more and 110 μm or less.

This makes the PET film easier to handle, and, for example, when applying the security window film 1 to an adherend by wet application, the workability of removing the application liquid after wet application can be improved. Furthermore, if the PET film constituting the laminate 10 is too thin, it will be necessary to increase the number of adhesive layers to ensure the overall thickness of the laminate 10. This may result in a deterioration in the appearance of the security window film 1 (for example, distortion of transmitted images) or make it difficult to remove the application liquid with a squeegee or the like after wet application. However, by setting the thickness of each PET film constituting the laminate 10 to a value within the above range, such problems can be more effectively prevented.

The total thickness of all PET films (i.e., first, second, and third PET films 11, 13, and 15) that make up the laminate 10 is preferably 240 μm or more and 360 μm or less, more preferably 280 μm or more and 360 μm or less, and even more preferably 300 μm or more and 320 μm or less.

This allows the security window film 1 to achieve high levels of security performance while also being easy to process and install.

The PET films (first, second, and third PET films 11, 13, and 15) that make up the laminate 10 may have different properties (e.g., thickness, weight-average molecular weight, etc.), but it is preferable that they have the same properties.

[1-1-2] Pressure-sensitive adhesive layer The pressure-sensitive adhesive layers (first and second pressure-sensitive adhesive layers 12, 14) constituting the laminate 10 have the function of bonding adjacent PET films (first, second and third PET films 11, 13, 15).

The adhesive layers (first and second adhesive layers 12, 14) that make up the laminate 10 can be made of adhesives commonly used in the field of window films. Examples of such adhesives include acrylic adhesives, rubber adhesives, silicone adhesives, and polyurethane adhesives. Among these, acrylic adhesives are preferred from the standpoint of weather resistance. These adhesives may be emulsion-type, solvent-type, or solventless.

The weight average molecular weight of the adhesive is preferably 300,000 or more and 2,000,000 or less, and more preferably 500,000 or more and 1,500,000 or less.

Note that "weight average molecular weight" here refers to a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

Examples of acrylic adhesives include (meth)acrylic acid ester copolymers. Examples of (meth)acrylic acid ester copolymers include copolymers of (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms, a monomer containing a functional group with active hydrogen, and optionally other monomers.

In this specification, the term "(meth)acrylic acid" is a concept that includes both "acrylic acid" and "methacrylic acid."

Examples of (meth)acrylic acid alkyl esters having an alkyl group carbon number of 1 to 20 include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate, and these may be used alone or in combination of two or more.

Examples of monomers containing a functional group having an active hydrogen include hydroxyl group-containing monomers such as (meth)acrylic acid hydroxyalkyl esters, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; amide group-containing monomers, such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-methylol acrylamide, and N-methylolmethacrylamide; monoalkylaminoalkyl (meth)acrylates, such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate; and carboxylic acids having ethylenically unsaturated bonds, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone or in combination.

Examples of the other monomers that may be used optionally include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene-based monomers such as styrene and α-methylstyrene; diene-based monomers such as butadiene, isoprene, and chloroprene; nitrile-based monomers such as acrylonitrile and methacrylonitrile; and N,N-dialkyl-substituted acrylamides such as N,N-dimethylacrylamide and N,N-dimethylmethacrylamide. These may be used alone or in combination of two or more.

The copolymerization form of the (meth)acrylic acid ester copolymer is not particularly limited, and may be any of a random copolymer, a block copolymer, and a graft copolymer.

The adhesive may be crosslinked. The crosslinking agent used for the crosslinking treatment is not particularly limited, and examples include polyisocyanate compounds, epoxy compounds, melamine resins, urea resins, dialdehydes, methylol polymers, metal chelate compounds, metal alkoxides, and metal salts. One or more selected from these may be used in combination.

The amount of crosslinking agent used will vary depending on the type, but is preferably 0.01 to 20 parts by weight, and more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the (meth)acrylic acid ester copolymer.

The adhesive layers (first and second adhesive layers 12, 14) that make up the laminate 10 need only be composed primarily of an adhesive, and may also contain components other than an adhesive.

Such components include, for example, ultraviolet absorbers, tackifiers, fillers, softeners, antioxidants, light stabilizers, crosslinkers, colorants, modifiers, rust inhibitors, flame retardants, hydrolysis inhibitors, surface lubricants, corrosion inhibitors, heat stabilizers, lubricants, antistatic agents, polymerization inhibitors, catalysts, leveling agents, thickeners, dispersants, and defoamers.

The thickness of each of the adhesive layers (first and second adhesive layers 12, 14) that make up the laminate 10 is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

The adhesive layers (first and second adhesive layers 12, 14) that make up the laminate 10 may have different conditions (e.g., thickness, composition, etc.), but it is preferable that they have the same conditions.

[1-2] Hard Coat Layer The hard coat layer 2 has better abrasion resistance than the first, second and third PET films 11, 13 and 15, and has the function of improving the abrasion resistance of the security window film 1 as a whole.

This allows the security window film 1 to exhibit excellent abrasion resistance after being applied to the substrate. It also effectively prevents scratches during the process of applying the security window film 1 to the substrate.

[1-2-1] (Meth)acrylate Resin The hard coat layer 2 is made of a material containing a (meth)acrylate resin, and the (meth)acrylate resin has urethane (meth)acrylate and hexafunctional (meth)acrylate as constituent components.

[1-2-1-1] Urethane (meth)acrylate When the (meth)acrylate resin contains urethane (meth)acrylate as a constituent, sufficient flexibility is imparted, and thus the occurrence of cracks in the hard coat layer 2 can be suppressed.

A urethane (meth)acrylate is a compound that contains at least a (meth)acryloyl group and a urethane bond, and has the property of polymerizing and curing when irradiated with energy rays. Examples of urethane (meth)acrylates include oligomers.

Furthermore, the number of (meth)acryloyl groups (hereinafter also referred to as "functionality") in the urethane (meth)acrylate may be monofunctional, difunctional, or trifunctional or higher, but is preferably monofunctional or difunctional.

Urethane (meth)acrylate can be obtained, for example, by reacting a polyol compound with a polyisocyanate compound to obtain an isocyanate-terminated urethane prepolymer, with a (meth)acrylate having a hydroxy group. Urethane (meth)acrylates can be used singly or in combination of two or more types.

The polyol compound used as a raw material for urethane (meth)acrylate is not particularly limited as long as it has two or more hydroxy groups, and examples include alkylene diols, polyether polyols, polyester polyols, and polycarbonate polyols. Of these, polyester polyols are preferred.

The polyol compound may be a difunctional diol, a trifunctional triol, or a polyol with four or more functionalities, but a difunctional diol is preferred, and a polyester diol is more preferred.

Examples of polyisocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanatodimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate. These compounds may be used alone or in combination. Of these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred.

A urethane (meth)acrylate can be obtained by reacting a (meth)acrylate containing a hydroxy group with the isocyanate-terminated urethane prepolymer obtained by reacting the above-mentioned polyol compound with a polyisocyanate compound. The (meth)acrylate containing a hydroxy group is not particularly limited, as long as it is a compound containing a hydroxy group and a (meth)acryloyl group in at least one molecule.

Specific examples of (meth)acrylates having a hydroxy group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; hydroxy group-containing (meth)acrylamides such as N-methylol (meth)acrylamide; and reaction products obtained by reacting diglycidyl esters of vinyl alcohol, vinylphenol, or bisphenol A with (meth)acrylic acid. These may be used alone or in combination of two or more. Among these, hydroxyalkyl (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

The proportion of urethane (meth)acrylate in the (meth)acrylate resin that constitutes the hard coat layer 2 is preferably 60% by mass or more and 85% by mass or less, more preferably 65% by mass or more and 82% by mass or less, and even more preferably 70% by mass or more and 80% by mass or less.

This allows the hard coat layer 2 to have sufficiently excellent abrasion resistance while also having more suitable flexibility, making it possible to more effectively prevent cracks and other problems from occurring in the hard coat layer 2.

[1-2-1-2] Hexafunctional (meth)acrylate A hexafunctional (meth)acrylate is a (meth)acrylate-based compound that has six ethylenically unsaturated groups in the molecule and that crosslinks and cures when irradiated with active energy rays.

Note that active energy rays refer to electromagnetic waves or charged particle beams that have an energy quantum, such as ultraviolet rays or electron beams.

Examples of such hexafunctional (meth)acrylates include (meth)acrylates such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate, and one or more selected from these can be used in combination.

When the proportion of hexafunctional (meth)acrylate in the (meth)acrylate resin constituting the hard coat layer 2 is XA [mass %] and the proportion of urethane (meth)acrylate in the (meth)acrylate resin constituting the hard coat layer 2 is XB [mass %], it is preferable to satisfy the relationship 0.18≦XA/XB≦0.66, it is more preferable to satisfy the relationship 0.22≦XA/XB≦0.54, and it is even more preferable to satisfy the relationship 0.25≦XA/XB≦0.43.
This makes it possible to make the above-mentioned effects more pronounced.

[1-2-1-3] Other Components The (meth)acrylate resin constituting the hard coat layer 2 may contain urethane (meth)acrylate and hexafunctional (meth)acrylate as constituent components, and may further contain other components.

Such components include, for example, urethane (meth)acrylates, monomer components other than hexafunctional (meth)acrylates, etc.

However, the proportion of components other than urethane (meth)acrylate and hexafunctional (meth)acrylate in the (meth)acrylate resin that constitutes the hard coat layer 2 is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[1-2-2] Other Components The hard coat layer 2 may contain components other than the above-mentioned (meth)acrylate resin.

Such components include, for example, antioxidants, ultraviolet absorbers, silane coupling agents, leveling agents, antistatic agents, antifoaming agents, and resin components other than (meth)acrylate resins.

However, the proportion of components other than the (meth)acrylate resin in the hard coat layer 2 is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[1-2-3] Other Conditions The thickness of the hard coat layer 2 is not particularly limited, but is preferably from 0.1 μm to 20 μm, more preferably from 0.2 μm to 15 μm, and even more preferably from 0.4 μm to 10 μm.

This more effectively prevents the hard coat layer 2 from becoming excessively hard, while providing even better abrasion resistance. It also makes the security window film 1 easier to handle and improves the workability of attaching the security window film 1 to an adherend. It also more effectively prevents cracks and other problems.

[1-3] Adhesion Adhesive Layer The adhesion adhesive layer (third adhesive layer) 3 is a part having adhesiveness that functions to adhere the security window film 1 to an adherend.

The adhesive constituting the adhesive layer 3 can be the same as that described in [1-1-2] above.

The adhesive contained in the adhesive layers (first and second adhesive layers 12, 14) constituting the laminate 10 and the adhesive contained in the adhesive layer 3 for attachment may be of different conditions.

The thickness of the adhesive layer 3 is not particularly limited, but is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 80 μm or less, and even more preferably 10 μm or more and 60 μm or less.

This not only improves the durability of the security window film 1, but also makes it easier to handle and apply (stick) to the substrate. It also improves the film's ability to conform to the shape of curved substrates, effectively preventing wrinkles and other problems.

[1-4] Other Conditions The overall thickness of the security window film 1 is preferably 350 μm or more and 500 μm or less, and more preferably 355 μm or more and 400 μm or less.

This makes the security window film 1 easier to handle while still ensuring sufficient security performance.

Here, "total thickness" refers to the overall thickness of the security window film 1 when it is attached to an adherend. Therefore, for example, even if a release liner 20 (described below) is disposed on the adhesive layer 3 during storage of the security window film 1, the thickness of the release liner 20 is not included in the total thickness.

The tear strength of the security window film 1, measured in accordance with JIS K7128-1:1998 (trouser tear method), is preferably 9 N or more (upper limit: e.g., 20 N or less). Furthermore, the tensile strength, measured in accordance with JIS A5759:2016, is preferably 800 N/25 mm or more (upper limit: e.g., 2500 N/25 mm or less).

Furthermore, the elongation measured in accordance with JIS A5759:2016 is preferably 60% or more (upper limit: for example, 300% or less).

Here, if a release liner 20 is disposed on the adhesive layer 3 of the security window film 1, the tear strength, tensile strength, and elongation are measured with the release liner 20 peeled off. When a security window film 1 that satisfies the above ranges is applied to an adherend (for example, the indoor side of a window), sufficient security performance can be achieved.

[2] Release Liner A release liner 20 may be disposed on the adhesive layer 3 for application of the security window film 1 .

The release liner 20 is peeled off from the adhesive layer 3 when the security window film 1 is to be attached to an adherend.

The release liner 20 is not particularly limited and may be one commonly used in the field of window films. Examples of release liners 20 include those with a release layer provided on the surface of a resin film substrate or paper substrate.

Examples of materials that can be used to make resin film substrates include polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, and polyacrylate. Examples of materials that can be used to make paper substrates include polyethylene-laminated paper, polypropylene-laminated paper, clay-coated paper, resin-coated paper, glassine paper, and fine paper.

Examples of release layers include those containing release agents such as silicone, long-chain alkyl resins, and fluorine-based resins.

The thickness of the release liner 20 is not particularly limited, but is preferably, for example, 10 μm or more and 400 μm or less. Furthermore, if the release layer is provided, the thickness of the release layer is preferably, for example, 0.01 μm or more and 5 μm or less.

[3] Manufacturing Method of Security Window Film Next, a manufacturing method of security window film will be described.

The security window film 1 can be manufactured, for example, by applying a liquid composition (coating liquid) for forming the hard coat layer 2 to one surface of the laminate 10 to form the hard coat layer 2, and then applying a liquid composition (coating liquid) for forming the adhesive layer 3 to the other surface of the laminate 10 to form the adhesive layer 3. In this method, the order in which the hard coat layer 2 and the adhesive layer 3 are formed is not particularly limited.

The laminate 10 can be produced, for example, as follows.
That is, first, a composition for forming a pressure-sensitive adhesive layer is applied to one surface of a first PET film 11 and dried to form a first pressure-sensitive adhesive layer 12 .

The adhesive layer-forming composition can be prepared by dissolving or suspending the above-mentioned materials constituting the adhesive layer in an appropriate solvent. Examples of solvents include esters such as ethyl acetate and butyl acetate; ketones such as methyl isobutyl ketone, methyl ethyl ketone and cyclohexanone; and aromatic hydrocarbons such as toluene and xylene. One or more of these can be used in combination.

The adhesive layer-forming composition may be applied by a known method, such as using various coaters such as an air knife coater, blade coater, bar coater, gravure coater, roll coater, roll knife coater, curtain coater, die coater, knife coater, screen coater, Mayer bar coater, or kiss coater.

Subsequently, the second PET film 13 is laminated on the first adhesive layer 12 .
Subsequently, the second pressure-sensitive adhesive layer 14 is formed in the same manner as above on the surface of the second PET film 13 of the laminate 10 opposite to the surface on which the first pressure-sensitive adhesive layer 12 is laminated.

Next, the third PET film 15 is laminated onto the second adhesive layer 14. This results in a laminate 10 in which the first PET film 11, first adhesive layer 12, second PET film 13, second adhesive layer 14, and third PET film 15 are laminated in this order.

The hard coat layer 2 can be formed by applying a liquid composition (coating liquid) for forming the hard coat layer 2 onto the first PET film 11 using, for example, bar coating, knife coating, roll coating, blade coating, die coating, or gravure coating, and then curing the coating by irradiating it with ultraviolet rays or electron beams or by heating.

The coating liquid for forming the hard coat layer 2 may contain components other than those described above, as necessary. Examples of such components include a thermosetting catalyst, a photopolymerization initiator, and a solvent.

Examples of methods for forming the adhesive layer 3 include the same methods as those described for forming the first adhesive layer 12.

[4] Adherend Next, the adherend to which the security window film 1 is attached will be described.

The security window film 1 is suitable for use on windows in buildings such as homes and offices, and in vehicles such as automobiles and trains.

This makes it difficult for window glass to break, and even if the window glass does break, the broken glass is held in a sheet shape, preventing it from scattering, making it difficult to unlock or break into windows or doors from the outside.

[5] Method for Applying the Security Window Film 1 Next, a method for applying the security window film 1 will be described.

When applying the security window film 1 to an adherend such as window glass, if a release liner 20 is present, the release liner 20 can be first peeled off to expose the adhesive layer 3, and then the adhesive layer 3 can be adhered to the adherend. Application liquid, in which a surfactant is added to water, can be used to apply the film to the interface between the adhesive layer 3 and the adherend, and then the application liquid can be scraped off using a tool called a squeegee, a method known as water application.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these.

For example, the security window film may have a configuration other than that described above. More specifically, for example, it may have at least one intermediate layer between the PET film and the adhesive layer, or between the PET film and the hard coat layer, or it may further have at least one coating layer on the outer surface side of the hard coat layer.

The security window film may also have other functional layers. Examples of other functional layers include a heat-shielding layer, an anti-reflection layer, an ultraviolet-shielding layer, a printed layer, etc.

Furthermore, the security window film of the present invention may be manufactured by any method and is not limited to those manufactured by the methods described above.

For example, the security window film of the present invention may be formed by a transfer method in which a composition for forming an adhesive layer for application is applied to one side of a release liner, and then the release liner with the adhesive layer for application is bonded to the laminate.

In addition, in the above-described embodiment, the hard coat layer and adhesive layer for application are formed after the laminate is formed. However, for example, the hard coat layer or adhesive layer for application may be formed on a PET film that will become part of the laminate, and then the laminate may be formed using the PET film.

The present invention will be described in detail below based on specific examples, but the present invention is not limited to these. Treatments and measurements in the following examples, for which no temperature conditions are specified, were carried out at room temperature (23°C).

[6] Production of window film (Example 1)
First, a liquid composition (coating liquid) for forming a hard coat layer was prepared by mixing a urethane (meth)acrylate and a hexafunctional (meth)acrylate as constituent components (polymerizable compounds) of a (meth)acrylate-based compound in a mass ratio of 75:25.

8UX-015A (manufactured by Taisei Fine Chemical Co., Ltd.) was used as the urethane (meth)acrylate, and dipentaerythritol hexaacrylate was used as the hexafunctional (meth)acrylate.

A 100 μm thick PET film ("Lumirror (registered trademark) T-60" manufactured by Toray Industries, Inc.) was prepared as the first, second, and third PET films.

The coating solution for forming a hard coat layer was applied to one surface of the first PET film by a bar coating method while adjusting the amount of coating so that the film thickness after curing would be 2.5 μm, and the film was irradiated with ultraviolet light at an integrated light dose of 200 mJ/cm ^2. This formed a hard coat layer.

Next, a solution of acrylic adhesive (100 parts by weight of a copolymer (weight average molecular weight 600,000) of butyl acrylate/acrylic acid = 90 parts by weight/10 parts by weight, and 1 part by weight of an isocyanate-based crosslinking agent) was applied to the surface of the first PET film opposite the surface on which the hard coat layer was formed, so that the thickness after drying would be 15 μm, and this was dried at 100°C for 1 minute to form a first adhesive layer.

Next, a second PET film was laminated onto the first adhesive layer. The above-mentioned acrylic adhesive was then applied to the second PET film in the same manner as above and dried to form a second adhesive layer with a thickness of 15 μm. Next, a third PET film was laminated onto the second adhesive layer to produce a laminate with three layers of PET film, each 100 μm thick.

A 25 μm thick adhesive layer for adhesion was formed on the third PET film of the laminate, producing a security window film with a total thickness (excluding the thickness of the release liner) of 357.5 μm. A 25 μm thick release liner was laminated onto the adhesive layer of the window film.

(Examples 2 to 4)
A security window film was produced in the same manner as in Example 1, except that in preparing the coating liquid for forming the hard coat layer, the compounding ratio of the urethane (meth)acrylate and the hexafunctional (meth)acrylate was changed as shown in Table 1, and the application amount of the coating liquid for forming the hard coat layer was adjusted so that the thickness of the hard coat layer would be as shown in Table 1.

(Comparative Examples 1 to 8)
A security window film was produced in the same manner as in Example 1, except that in preparing the coating liquid for forming the hard coat layer, the compounding ratio of the urethane (meth)acrylate and the hexafunctional (meth)acrylate was changed as shown in Table 1, and the application amount of the coating liquid for forming the hard coat layer was adjusted so that the thickness of the hard coat layer would be as shown in Table 1.

(Comparative Example 9)
A security window film was produced in the same manner as in Comparative Example 8, except that the laminate consisted of a first PET film having a thickness of 188 μm, a first adhesive layer having a thickness of 15 μm, and a second PET film having a thickness of 188 μm laminated in this order. In this Comparative Example, an adhesive layer for application was formed on the second PET film.

[7] Evaluation of Security Window Film The security window film obtained was evaluated as follows.

[7-1] Crack Resistance Test of Hard Coat Layer The obtained security window film was rolled up into a cylinder having an outer diameter of 20 mm with the hard coat layer facing outward.

A needle was pushed 10 mm into the hard coat layer, and the broken surface was visually inspected to evaluate the presence or absence of cracks.

◯: No cracks ×: Cracks present

[7-2] Scratch Test of Hard Coat Layer The surface of the hard coat layer of the obtained security window film was subjected to a scratch test by moving #0000 steel wool back and forth 10 times at a pressure of 250 g/cm ² .

The surface of the hard coat layer was visually observed, and the abrasion resistance of the hard coat layer was evaluated according to the following criteria.

A: No scratches A': 3 scratches or less B: 10 scratches or less C: 20 scratches or less D: 30 scratches or more

[7-3] Adhesion Test The obtained security window film was subjected to a cross-cut peel test to evaluate the adhesion of the hard coat layer.

That is, a utility knife was used to make 11 vertical and 11 horizontal cuts at 1 mm intervals in a grid pattern on the surface of the hard coat layer of the security window film, creating a total of 100 squares, and adhesive tape (Nichiban Co., Ltd., "Cellotape®") was applied to the grids. A Cellotape® peel test was then conducted in accordance with the grid tape method of JIS K 5600-5-6 (cross-cut method), and the adhesion of the hard coat layer was evaluated according to the following criteria.

Good: When the same area was peeled twice, none of the 100 squares peeled off.
×: When the same area was peeled twice, one or more squares were peeled off.

Table 1 summarizes the main components of the security window film for each of the examples and comparative examples, as well as the results of the above evaluations. In Table 1, urethane (meth)acrylate is indicated as "UA" and hexafunctional (meth)acrylate is indicated as "hexafunctional."

As is clear from Table 1, in Examples 1 to 4, good results were obtained in all of the abrasion resistance, crack resistance and adhesion of the hard coat layer.
In contrast, the comparative examples did not provide satisfactory results.

More specifically, in Comparative Examples 1 to 3, in which the (meth)acrylate resin constituting the hard coat layer did not contain a hexafunctional (meth)acrylate, and in Comparative Examples 6 and 7, in which the proportion of hexafunctional (meth)acrylate in the (meth)acrylate resin constituting the hard coat layer was less than 15% by mass, sufficient abrasion resistance was not obtained.

Furthermore, in Comparative Examples 4, 5, 8, and 9, in which the proportion of hexafunctional (meth)acrylate in the (meth)acrylate resin constituting the hard coat layer exceeded 40% by mass, sufficient crack resistance was not obtained.

Good results were obtained with regard to adhesion in all cases, but in Comparative Example 3, which had a relatively thick hard coat layer, adhesion decreased after 168 hours when exposed to conditions of 60°C and 95% RH.

In addition, security window films were manufactured in the same manner as above, except that the thickness of each PET film making up the laminate was varied within the range of 80 μm or more and 120 μm or less, and the same evaluations as above were carried out, with the same results as above being obtained.

In addition, security window films were manufactured in the same manner as above, except that the overall thickness was varied within the range of 350 μm to 500 μm, and the same evaluations were carried out as above, with the same results obtained.

Security window films were manufactured in the same manner as above, except that the thickness of the hard coat layer was varied in the range of 0.1 μm to 20 μm, and the same evaluations were carried out as above. The same results were obtained.

1: Security window film 2: Hard coat layer 3: Adhesion adhesive layer (third adhesive layer)
10: Laminate 11: First PET film 12: First adhesive layer 13: Second PET film 14: Second adhesive layer 15: Third PET film 20: Release liner

Claims (5)

The present invention comprises a laminate in which a plurality of films made of a material containing polyethylene terephthalate are laminated via pressure-sensitive adhesive layers, a hard coat layer made of a material containing a (meth)acrylate resin and disposed on one side of the laminate, and an adhesive layer for adhering to an adherend, disposed on the side of the laminate opposite to the side on which the hard coat layer is disposed,
The (meth)acrylate resin has, as constituent components , a urethane (meth)acrylate as an oligomer and a hexafunctional (meth)acrylate as a monomer ,
a proportion of the hexafunctional (meth)acrylate in the (meth)acrylate resin is 15% by mass or more and 40% by mass or less;
A security window film, characterized in that the proportion of the urethane (meth)acrylate in the (meth)acrylate resin is 60% by mass or more and 85% by mass or less . The security window film of claim 1, wherein the laminate comprises three or more layers of the film. The security window film according to claim 1 or 2, wherein the thickness of each film is 80 μm or more and 120 μm or less. The security window film according to any one of claims 1 to 3, having an overall thickness of 350 μm or more and 500 μm or less. The security window film according to any one of claims 1 to 4, wherein the thickness of the hard coat layer is 0.1 μm or more and 20 μm or less.