JP7765078B2 - Anti-reflective film - Google Patents

Description

The present invention relates to an anti-reflection film, and more specifically to an anti-reflection film suitable for use on the surfaces of displays such as liquid crystal displays, organic EL displays, and touch panels for smartphones and the like.

Anti-reflective film is sometimes placed on the surface of displays such as LCD displays, organic EL displays, and touch panels on smartphones to prevent external light from being reflected on the screen.

Anti-reflection films known to have a hard coat layer and an anti-reflection layer (low refractive index layer) on a substrate film, in that order. For example, in Patent Document 1, filed by the applicant, the composition of the low refractive index layer formed on the surface of the hard coat layer is examined to improve the anti-reflection properties, scratch resistance, and stain resistance of the anti-reflection film.

International Publication No. 2021/020504

In order to improve the scratch resistance of an anti-reflective film, it is effective to devise a material for the anti-reflective layer formed on the surface of the hard coat layer, as in the embodiment of Patent Document 1. However, it is believed that devising a material for the hard coat layer can also be effective in improving the scratch resistance of the anti-reflective film. If the scratch resistance of the hard coat layer is improved in addition to the anti-reflective layer, the scratch resistance of the anti-reflective film as a whole may be even more effectively improved.

The problem that the present invention aims to solve is to provide an anti-reflection film that has excellent scratch resistance thanks to the contribution of a hard coat layer.

In order to solve the above problems, the antireflection film of the present invention comprises a substrate film, a hard coat layer formed on the surface of the substrate film, and an antireflection layer formed on the surface of the hard coat layer, wherein the hard coat layer is composed of a cured product of an ionizing radiation-curable composition containing a (meth)acrylate compound and a polyfunctional secondary thiol.

The ionizing radiation-curable composition preferably contains, as the (meth)acrylate compound, a polyfunctional urethane (meth)acrylate compound and a pentaerythritol (meth)acrylate compound having a hydroxyl value of 200 mgKOH/g or more and 350 mgKOH/g or less. In this case, the content of the pentaerythritol (meth)acrylate compound in the ionizing radiation-curable composition is preferably 15% by mass or more and 75% by mass or less, based on 100% by mass of the solids content. Furthermore, the polyfunctional secondary thiol is preferably trifunctional or higher. The content of the polyfunctional secondary thiol in the ionizing radiation-curable composition is preferably 3% by mass or more and 35% by mass or less, based on 100% by mass of the solids content.

The base film and the antireflection layer may be made of a material having a carbon-carbon double bond at least in the areas in contact with the hard coat layer. Furthermore, the antireflection layer may be made of a cured product of an ionizing radiation-curable material containing (meth)acrylate at least in the areas in contact with the hard coat layer.

The anti-reflection film according to the present invention comprises a substrate film, a hard coat layer formed on the surface of the substrate film, and an anti-reflection layer formed on the surface of the hard coat layer. The hard coat layer is composed of a cured product of an ionizing radiation-curable composition containing a (meth)acrylate compound and a polyfunctional secondary thiol, and therefore the hard coat layer contributes to providing excellent scratch resistance.

Here, when the ionizing radiation-curable composition contains, as the (meth)acrylate compound, a polyfunctional urethane (meth)acrylate compound and a pentaerythritol (meth)acrylate compound having a hydroxyl value of 200 mgKOH/g or more and 350 mgKOH/g or less, the scratch resistance of the anti-reflective film can be effectively improved. Furthermore, the anti-reflective film has an excellent effect of suppressing curling while maintaining high hardness. In this case, when the content of the pentaerythritol (meth)acrylate compound in the ionizing radiation-curable composition is 15% by mass or more and 75% by mass or less, relative to 100% by mass of the solids content, the above-mentioned effects are particularly enhanced.

Furthermore, when the polyfunctional secondary thiol is trifunctional or higher, the hardness of the anti-reflection film can be effectively increased. When the content of the polyfunctional secondary thiol in the ionizing radiation-curable composition is 3% by mass or more and 35% by mass or less, relative to 100% by mass of the solids content, the hardness can be ensured while achieving a significant effect of improving the scratch resistance of the anti-reflection film.

When the substrate film and antireflection layer, at least the portions in contact with the hard coat layer, are composed of a material containing a carbon-carbon double bond, chemical bonds are formed between the carbon-carbon double bonds contained in the substrate film and antireflection layer and the polyfunctional secondary thiol contained in the hard coat layer, thereby improving adhesion between the layers. Furthermore, when the antireflection layer, at least the portions in contact with the hard coat layer, are composed of a cured product of an ionizing radiation-curable material containing (meth)acrylate, adhesion between the hard coat layer and the antireflection layer is effectively improved.

1 is a cross-sectional view of an antireflection film according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view of an antireflection film according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view of an antireflection film according to a third embodiment of the present invention. FIG. 10 is a cross-sectional view of an anti-reflection film according to a fourth embodiment of the present invention.

The present invention is described in detail below.

<Anti-reflection film of first embodiment>
FIG. 1 is a cross-sectional view of an antireflection film according to a first embodiment of the present invention. As shown in FIG. 1, an antireflection film 10 according to the first embodiment of the present invention includes a substrate film 12, a hard coat layer 16 formed on the surface of the substrate film 12, and a low refractive index layer 14 serving as an antireflection layer formed on the surface of the hard coat layer 16. The antireflection film 10 includes the substrate film 12, the hard coat layer 16, and the low refractive index layer 14, in this order. Preferably, the substrate film 12 and the hard coat layer 16 are in direct contact without any other layer interposed therebetween. Also, preferably, the hard coat layer 16 and the low refractive index layer 14 (or a layer other than the low refractive index layer 14 that constitutes the antireflection layer) are in direct contact without any other layer interposed therebetween.

(Base film)
The substrate film 12 is not particularly limited as long as it is transparent. Examples of the substrate film 12 include transparent polymer films and glass films. Transparency refers to a total light transmittance of 50% or more in the visible light wavelength range, and more preferably a total light transmittance of 85% or more. The total light transmittance can be measured in accordance with JIS K7361-1 (1997). The thickness of the substrate film 12 is not particularly limited, but from the viewpoint of excellent handleability, it is preferably within the range of 2 to 500 μm, and more preferably within the range of 2 to 200 μm. Note that the term "film" generally refers to a film having a thickness of less than 0.25 mm, but even if the thickness is 0.25 mm or more, it is considered to be a "film" as long as it can be wound into a roll.

Polymer materials for the base film 12 include polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin; polycarbonate resin, poly(meth)acrylate resin, polystyrene resin, polyamide resin, polyimide resin, polyacrylonitrile resin, polypropylene resin, polyethylene resin, polyolefin resins such as polycycloolefin resin and cycloolefin copolymer resin; cellulose-based resins such as triacetyl cellulose resin and diacetyl cellulose resin; polyphenylene sulfide resin, polyvinyl chloride resin, polyvinylidene chloride resin, and polyvinyl alcohol resin. The polymer material for the base film 12 may be composed of only one of these materials, or a combination of two or more. Of these, polyethylene terephthalate resin, polyimide resin, polycarbonate resin, poly(meth)acrylate resin, polycycloolefin resin, cycloolefin copolymer resin, and triacetyl cellulose resin are more preferred from the standpoints of optical properties and durability.

The substrate film 12 may be composed of a single layer containing one or more of the above polymeric materials, or it may be composed of two or more layers, such as a layer containing one or more of the above polymeric materials and a layer containing one or more different polymeric materials.

It is preferable that at least the portion of the substrate film 12 that contacts the hard coat layer 16 be composed of a material containing a carbon-carbon double bond, preferably an ethylenic carbon-carbon double bond. This forms a bond between the thiol group of the polyfunctional secondary thiol contained in the hard coat layer 16 (described below) and the carbon-carbon double bond of the substrate film 12, improving adhesion between the substrate film 12 and the hard coat layer 16 and providing a high level of scratch resistance for the anti-reflection film 10. In this case, the film material that constitutes the substrate film 12 itself may contain a carbon-carbon double bond. Alternatively, if a coating layer is formed on the surface of the film material by primer treatment or the addition of a functional layer such as an antistatic layer, the constituent material of the coating layer may contain a carbon-carbon double bond.

(Hard Coat Layer)
The hard coat layer 16 contributes to improving the scratch resistance of the anti-reflection film 10. The hard coat layer is composed of a cured product of an ionizing radiation-curable composition containing a (meth)acrylate compound and a polyfunctional secondary thiol. Ionizing radiation refers to electromagnetic waves or charged particle beams that have an energy quantum capable of polymerizing or crosslinking molecules. Examples of ionizing radiation include electromagnetic waves such as ultraviolet (UV), X-rays, and gamma rays, and charged particle beams such as electron beams (EB), alpha rays, and ion beams. Of these, ultraviolet (UV) rays are particularly preferred from the viewpoint of productivity. Hereinafter, the ionizing radiation-curable composition may be simply referred to as a curable composition. Furthermore, in this specification, "(meth)acrylate" refers to "at least one of acrylate and methacrylate.""(meth)acryloyl" refers to "at least one of acryloyl and methacryloyl.""(meth)acrylic" refers to "at least one of acrylic and methacrylic." The "(meth)acrylate compound" is a compound having a (meth)acryloyl group, and examples thereof include a monomer, an oligomer, a prepolymer, etc. Hereinafter, the (meth)acrylate compound may be simply referred to as a (meth)acrylate.

The (meth)acrylate may be a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. Alternatively, it may be a combination of a monofunctional (meth)acrylate and a polyfunctional (meth)acrylate. From the viewpoint of improving curability, it is more preferable that the curable composition contains a polyfunctional (meth)acrylate as the (meth)acrylate.

(Meth)acrylates include urethane (meth)acrylate, silicone (meth)acrylate, alkyl (meth)acrylate, and aryl (meth)acrylate. Of these, urethane (meth)acrylate, particularly urethane (meth)acrylate oligomer, is preferred. Examples of urethane (meth)acrylates include those obtained by reacting a polyisocyanate compound with a hydroxyl group-containing (meth)acrylate compound and, if necessary, a polyol compound. Examples of polyisocyanate compounds include diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate, as well as nurate-modified, adduct-modified, and biuret-modified versions of these compounds. Examples of hydroxyl group-containing (meth)acrylate compounds include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, trimethylolpropane diacrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and polyoxyalkylene-modified and polylactone-modified versions thereof. Examples of polyol compounds include ethylene glycol, propylene glycol, butanediol, hexanediol, polyoxyethylene glycol, polyoxypropylene glycol, glycerin, trimethylolpropane, pentaerythritol, biphenol, and bisphenol. When the curable composition for forming the hard coat layer 16 contains urethane (meth)acrylate as the ionizing radiation-curable resin, the hard coat layer 16 has appropriate flexibility, thereby increasing the bending resistance of the antireflection film 10 and making it suitable for use in flexible displays that are repeatedly bent, such as foldable displays and rollable displays. Furthermore, even if the base film 12 is made of a material such as polycycloolefin or cycloolefin copolymer, which is relatively prone to cracking, cracking of the base film 12 is easily prevented.

It is preferable that the (meth)acrylate constituting the curable composition further contains a pentaerythritol (meth)acrylate compound. Specific examples of pentaerythritol (meth)acrylate compounds include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tetra(meth)acrylate, tripentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, and tripentaerythritol octa(meth)acrylate. It is particularly preferable that the curable composition contain pentaerythritol tri(meth)acrylate. Furthermore, the pentaerythritol (meth)acrylate compound preferably has a hydroxyl value of 200 mg KOH/g or more, or 350 mg KOH/g or more.

The pentaerythritol (meth)acrylate compound is a low-viscosity multifunctional (meth)acrylate. Its inclusion in the curable composition enhances the coatability of the curable composition, allowing it to be applied to the substrate film 12 with a reduced amount of solvent. This suppresses unevenness and other non-uniform structures that occur during the solvent drying process, resulting in an anti-reflective film 10 with high appearance quality. However, while using a low-viscosity (meth)acrylate may be prone to film curl due to cure shrinkage, the use of a pentaerythritol (meth)acrylate compound with the above-mentioned hydroxyl value minimizes cure shrinkage. This suppresses curling of the anti-reflective film 10 and further reduces coating unevenness while maintaining sufficient hardness. The content of the pentaerythritol (meth)acrylate compound in the curable composition is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, based on 100% by mass of the solids content of the (meth)acrylate compound contained in the curable composition. This effectively improves hardness and coatability. The content is preferably 75% by mass or less, more preferably 65% by mass or less, and even more preferably 55% by mass. This effectively suppresses curling.

As described above, the curable composition contains a polyfunctional secondary thiol in addition to a (meth)acrylate compound. The polyfunctional secondary thiol is a compound containing two or more secondary thiol groups (mercapto groups; -SH) in the molecule. The inclusion of the polyfunctional thiol in the curable composition improves the scratch resistance of the anti-reflection film 10. This is thought to be due to the polyfunctional thiol forming a bond with the (meth)acrylate compound in the hard coat layer 16, as well as improved adhesion between the hard coat layer 16 and the substrate film 12 and the low refractive index layer 14. In particular, when at least the portions of the substrate film 12 and the low refractive index layer 14 (anti-reflection layer) that contact the hard coat layer 16 are made of a material having a carbon-carbon double bond, the thiol group of the polyfunctional thiol reacts with the carbon-carbon double bond to form a bond (radical addition reaction), thereby particularly enhancing adhesion between the hard coat layer 16 and the substrate film 12 and the low refractive index layer 14 (anti-reflection layer).

In particular, when the polyfunctional thiol contained in the curable composition is a secondary thiol, gelation of the curable composition is suppressed compared to when it is a primary thiol. As a result, the storage stability of the uncured curable composition is improved. Furthermore, fisheye defects resulting from gelation products are less likely to occur in the formed hard coat layer 16, resulting in an anti-reflection film 10 having a highly uniform hard coat layer 16. Furthermore, secondary thiols have a weaker odor than primary thiols, and simpler equipment is required for exhaust and other processes during the manufacturing process of the anti-reflection film 10. Furthermore, from the perspective of increasing the hardness of the hard coat layer 16, it is preferable that the polyfunctional thiol be tri- or more functional. In particular, from the perspective of reducing material costs, it is preferable that the polyfunctional thiol be tri- or tetra-functional.

Examples of polyfunctional secondary thiols that can be suitably used in forming the hard coat layer 16 include pentaerythritol tetrakis(3-mercaptobutyrate), pentaerythritol tris(3-mercaptobutyrate), 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinane-2,4,6-trione, trimethylolpropane tris(3-mercaptobutyrate), trimethylolethane tris(3-mercaptobutyrate), and 1,4-bis(3-mercaptobutyryloxy)butane. The curable composition may contain only one type of these polyfunctional secondary thiols, or two or more types.

The content of polyfunctional secondary thiol in the hard coat layer 16 is preferably 3% by mass, more preferably 5% by mass or more, and even more preferably 7% by mass or more, based on the total solids content of the curable composition. This significantly improves scratch resistance. On the other hand, the content is preferably 35% by mass or less, more preferably 25% by mass or less, and even more preferably 15% by mass or less. This makes it easier to ensure the hardness of the hard coat layer 16.

The curable composition that forms the hard coat layer 16 may or may not contain a non-ionizing radiation curable resin in addition to the ionizing radiation curable resin. The curable composition that forms the hard coat layer 16 may also contain a photopolymerization initiator. If necessary, it may also contain additives that can be added to the curable composition. Examples of additives include dispersants, leveling agents, antifoaming agents, thixotropic agents, antifouling agents, antibacterial agents, flame retardants, slip agents, antistatic agents, inorganic particles, and resin particles. If necessary, it may also contain a solvent.

Non-ionizing radiation curable resins include thermoplastic resins and thermosetting resins. Thermoplastic resins include polyester resins, polyether resins, polyolefin resins, and polyamide resins. Thermosetting resins include unsaturated polyester resins, epoxy resins, alkyd resins, and phenolic resins.

Examples of photopolymerization initiators include alkylphenone-based, acylphosphine oxide-based, and oxime ester-based photopolymerization initiators. Examples of alkylphenone-based photopolymerization initiators include 2,2'-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one. Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and the like. Examples of oxime ester photopolymerization initiators include 1,2-octanedione, 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime), and ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime). These photopolymerization initiators may be used alone or in combination of two or more.

The content of the photopolymerization initiator is preferably in the range of 0.1% by mass to 10% by mass, based on the total solid content of the curable composition. It is more preferably in the range of 1% by mass to 5% by mass.

Inorganic particles and resin particles are added to the hard coat layer 16 for purposes such as preventing blocking of the hard coat layer 16 and adjusting the hard coat layer 16 to a high refractive index. The inorganic particles and resin particles create fine surface irregularities on the hard coat layer 16, which helps prevent blocking, which occurs when the hard coat film consisting of the substrate film 12 and the hard coat layer 16 is wound into a roll before the low refractive index layer 14 is formed. By increasing the refractive index of the hard coat layer 16, the anti-reflection function can be further enhanced when the low refractive index layer 14 is laminated thereon. A high refractive index refers to a refractive index of 1.50 or higher at a measurement wavelength of 589.3 nm, preferably in the range of 1.55 to 1.80, and more preferably in the range of 1.60 to 1.70.

Inorganic particles that can optically adjust the refractive index of the hard coat layer 16 to a high level include metal oxide particles made of oxides of metals such as titanium, zirconium, tin, zinc, silicon, niobium, aluminum, chromium, magnesium, germanium, gallium, antimony, and platinum. These may be used alone or in combination as optically adjustable inorganic particles. Of these, titanium oxide and zirconium oxide are particularly preferred from the standpoint of achieving both a high refractive index and transparency. Resin particles include, for example, resin particles made of resins such as (meth)acrylic resin, styrene resin, styrene-(meth)acrylic resin, urethane resin, polyamide resin, silicone resin, epoxy resin, phenolic resin, polyethylene resin, and cellulose. These may be used alone or in combination as resin particles.

The thickness of the hard coat layer 16 is not particularly limited, but from the viewpoint of having sufficient hardness, it is preferably 0.5 μm or more, and more preferably 0.75 μm or more. Furthermore, from the viewpoint of easily suppressing curling due to the difference in thermal shrinkage from the base film 12, it is preferably 20 μm or less, and more preferably 10 μm or less. The thickness of the hard coat layer 16 is the thickness of a relatively smooth portion in the thickness direction that is free of irregularities caused by inorganic particles or resin particles.

The arithmetic mean roughness Ra of the surface of the hard coat layer 16 on which the surface irregularities are formed is preferably within the range of 0.3 to 20 nm, from the viewpoint of preventing blocking, etc., and more preferably within the range of 0.5 to 10 nm.

Solvents used in the curable composition that forms the hard coat layer 16 include alcohol-based solvents such as ethanol, isopropyl alcohol (IPA), n-butyl alcohol (NBA), ethylene glycol monomethyl ether (EGM), ethylene glycol monoisopropyl ether (IPG), propylene glycol monomethyl ether (PGM), and diethylene glycol monobutyl ether; ketone-based solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone, and acetone; aromatic solvents such as toluene and xylene; ester-based solvents such as ethyl acetate (EtAc), propyl acetate, isopropyl acetate, and butyl acetate (BuAc); and amide-based solvents such as N-methylpyrrolidone, acetamide, and dimethylformamide. These solvents may be used alone or in combination.

The solids concentration of the curable composition (concentration of components other than the solvent) can be determined appropriately taking into consideration factors such as coatability and film thickness. For example, it may be 1 to 90% by mass, 1.5 to 80% by mass, or 2 to 70% by mass.

(Low refractive index layer)
In the anti-reflection film 10 according to this embodiment, a low refractive index layer 14 is provided on the surface of the hard coat layer 16 as an anti-reflection layer. The low refractive index layer 14 has a lower refractive index than the hard coat layer 16, and exhibits an anti-reflection effect due to a significant difference in refractive index between the low refractive index layer 14 and the hard coat layer 16. The refractive index of the low refractive index layer 14 is preferably in the range of 1.29 to 1.45, more preferably 1.32 to 1.43. The refractive index of the low refractive index layer 14 is measured at a wavelength of 589.3 nm. The composition of the low refractive index layer 14 is not particularly limited, but it is preferable that the low refractive index layer 14 contains inorganic oxide particles 18, hollow silica particles 22, a fluorine-containing compound, and a binder resin. The low refractive index layer 14 may be suitably formed from a material described in Patent Document 1.

It is preferable that at least the portion of the low refractive index layer 14 that contacts the hard coat layer 16 be composed of a material having a carbon-carbon double bond, preferably an ethylenic carbon-carbon double bond. This forms a bond between the thiol group of the polyfunctional secondary thiol contained in the hard coat layer 16 and the carbon-carbon double bond of the low refractive index layer 14, improving adhesion between the low refractive index layer 14 and the hard coat layer 16 and providing a significant improvement in the scratch resistance of the anti-reflection film 10. For example, the carbon-carbon double bond of a (meth)acrylate contained in the low refractive index layer 14 as a binder resin can fulfill this role.

As the binder resin, from the viewpoint of the scratch resistance of the low refractive index layer 14, a cured product of a thermosetting compound or a cured product of an ultraviolet-curable compound is preferred. Furthermore, from the viewpoint of productivity, a cured product of an ultraviolet-curable compound is more preferred.

Examples of UV-curable resins include monomers, oligomers, and prepolymers that have UV-reactive groups. Examples of UV-reactive groups include radical polymerization-type reactive groups with ethylenically unsaturated bonds, such as acryloyl, methacryloyl, allyl, and vinyl groups, and cationic polymerization-type reactive groups, such as oxetanyl groups. Among these, acryloyl, methacryloyl, and oxetanyl groups are more preferred, with acryloyl and methacryloyl groups being particularly preferred. In other words, (meth)acrylates are particularly preferred.

Examples of (meth)acrylates include urethane (meth)acrylate, silicone (meth)acrylate, alkyl (meth)acrylate, and aryl (meth)acrylate. The (meth)acrylate may consist solely of a monofunctional (meth)acrylate, a polyfunctional (meth)acrylate, or a combination of a monofunctional (meth)acrylate and a polyfunctional (meth)acrylate. It is more preferable that the (meth)acrylate contain a polyfunctional (meth)acrylate.

Monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, and decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, Cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, 2-naphthylmethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxy-2-methylethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate, 2-phenylphenoxyethyl (meth)acrylate, 4-phenylphenoxyethyl (meth)acrylate, 3-(2-phenylphenyl)-2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxyethylene glycol (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, etc.

Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and tetrafunctional (meth)acrylates. More specifically, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. Examples of such acrylates include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tetra(meth)acrylate, tripentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, and tripentaerythritol octa(meth)acrylate.

The UV-curable resin may be composed of one or more of the above-mentioned (meth)acrylates. From the perspective of improving scratch resistance, the UV-curable resin preferably contains a pentafunctional or higher polyfunctional (meth)acrylate, and it is also preferable to increase the content of the pentafunctional or higher polyfunctional (meth)acrylate.

The polyfunctional (meth)acrylate preferably contains a dimer. Dimers of polyfunctional (meth)acrylates have an excellent curing rate and can easily increase the curing rate of the curable composition, thereby further improving scratch resistance. Among these, it is preferable to contain at least one selected from the group consisting of dimers of pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, and it is even more preferable to contain at least one selected from the group consisting of dimers of pentaerythritol triacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

From the viewpoints of scratch resistance, transparency, and solubility in solvents, the content of the above dimer is preferably in the range of 25 to 50 mass% based on the total solid content of the polyfunctional (meth)acrylate. It is more preferably in the range of 30 to 40 mass%.

The inorganic oxide particles 18, when contained in the low refractive index layer 14, form convex portions on the surface of the low refractive index layer 14. The formation of convex portions on the surface of the low refractive index layer 14 by the inorganic oxide particles 18 allows the low refractive index layer 14 to have good scratch resistance.

The inorganic oxide particles 18 may be solid or hollow. Solid particles are preferred. Solid particles are particles that are substantially free of voids, with the void ratio being less than 5% of the solid particle volume. Hollow particles are particles that have voids, with the void ratio being 5% or more of the hollow particle volume. Solid inorganic oxide particles 18 improve the scratch resistance of the low refractive index layer 14 and the anti-reflection film 10. Hollow inorganic oxide particles 18 lower the refractive index of the low refractive index layer 14 and reduce light reflection. The void ratio in hollow particles is preferably 10 to 80% of the hollow particle volume, more preferably 20 to 60%, and even more preferably 30 to 60%. A void ratio of 10% or more lowers the refractive index and reduces light reflection. When the proportion of voids is 80% or less, a decrease in the dispersibility of the inorganic oxide particles 18 can be suppressed.

Examples of inorganic oxide particles 18 include metal oxide particles made of oxides of metals such as titanium, zirconium, silicon, aluminum, and calcium. These may be used alone or in combination as inorganic oxide particles 18. Of these, silica particles and alumina particles are preferred, with alumina particles being particularly preferred, from the standpoints of their low refractive index, excellent transparency, and high hardness.

The shape of the inorganic oxide particles 18 is not particularly limited and may be spherical, needle-like, scale-like, rod-like, fibrous, irregular, etc. Of these, spherical shapes are preferred.

The inorganic oxide particles 18 form convex portions on the surface of the low refractive index layer 14, and in order to obtain good scratch resistance, the difference (r - d) between the average particle diameter r of the inorganic oxide particles 18 and the average thickness d of the low refractive index layer 14 is preferably 10 nm or more. The difference (r - d) is more preferably 15 nm or more, and even more preferably 18 nm or more. On the other hand, from the perspective of suppressing the height of the formed convex portions and maintaining transparency, the difference (r - d) is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less.

The average particle diameter r of the inorganic oxide particles 18 depends on the average thickness d of the low refractive index layer 14, but is preferably in the range of 60 to 400 nm. It is more preferably in the range of 70 to 300 nm, and even more preferably in the range of 90 to 200 nm. The average particle diameter r of the inorganic oxide particles 18 is a volume-based average arithmetic value obtained by a laser diffraction/scattering method in accordance with JIS Z8825, and includes not only the primary particle diameter but also the secondary particle diameter, which is agglomeration of particles.

The content of inorganic oxide particles 18 in the low refractive index layer 14 is preferably 0.1% by mass or more and 4.0% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14. When the content of inorganic oxide particles 18 in the low refractive index layer 14 is 0.1% by mass or more, based on 100% by mass of the solid content of the low refractive index layer 14, excellent scratch resistance can be obtained. From this perspective, the content of inorganic oxide particles 18 in the low refractive index layer 14 is preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more, based on 100% by mass of the solid content of the low refractive index layer 14. When the content of inorganic oxide particles 18 in the low refractive index layer 14 is 4.0% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14, high transparency can be obtained. From this perspective, the content of inorganic oxide particles 18 in the low refractive index layer 14 is preferably 3.5% by mass or less, and even more preferably 3.2% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14. The solid content of the low refractive index layer 14 referred to here refers to components that are not fixed in the binder resin in the low refractive index layer 14 and are liquid at room temperature. The solid content of the low refractive index layer 14 includes inorganic oxide particles 18, hollow silica particles 22, binder resin, and fluorine-containing compounds fixed in the binder resin. It does not include oil components used as additives or surfactants that are not fixed in the binder resin.

The hollow silica particles 22 have an average particle diameter smaller than the average thickness of the low-refractive-index layer 14. The hollow silica particles 22 preferably have an average particle diameter smaller than the inorganic oxide particles 18 that form the convex portions on the surface of the low-refractive-index layer 14. The hollow silica particles 22 do not substantially contribute to the formation of the surface irregularities of the low-refractive-index layer 14. The hollow silica particles 22 are particles that have cavities inside them, with the cavities accounting for 5% or more of their volume. Hollow refers to particles with a core-shell structure consisting of an outer shell and an internal cavity, or particles with a porous structure containing numerous cavities. The hollow structure of the hollow silica particles 22 lowers the refractive index of the low-refractive-index layer 14 and reduces light reflection. The shape of the hollow silica particles 22 is not particularly limited, but spherical, spindle-shaped, ovoid, tabular, cubic, irregular, etc. are preferred. Of these, spherical, tabular, and cubic shapes are particularly preferred.

In the hollow silica particles 22, the proportion of voids is preferably 10 to 80% by volume. More preferably, it is 20 to 60% by volume, and even more preferably, it is 30 to 60% by volume. If the proportion of voids is 10% or more by volume, the refractive index can be lowered and light reflection can be reduced. If the proportion of voids is 80% or less by volume, a decrease in the dispersibility of the hollow silica particles 22 can be suppressed.

The average particle diameter of the hollow silica particles 22 depends on the average thickness of the low refractive index layer 14, but is preferably 5 nm or more and 100 nm or less. It is more preferably 20 nm or more and 80 nm or less, and even more preferably 40 nm or more and 70 nm or less. When the average particle diameter of the hollow silica particles 22 is within these preferred ranges, the low refractive index layer 14 can achieve excellent anti-reflection properties and transparency. The average particle diameter is a volume-based average arithmetic value obtained by a laser diffraction/scattering method in accordance with JIS Z8825. It includes not only the primary particle diameter but also the secondary particle diameter, which is agglomeration of particles.

The refractive index of the hollow silica particles 22 is preferably in the range of 1.01 to 1.45. It is more preferably in the range of 1.15 to 1.38, and even more preferably in the range of 1.15 to 1.35. Within this range, excellent anti-reflection effects are obtained.

The content of hollow silica particles 22 in the low refractive index layer 14 is preferably 6.0% by mass or more and 49.9% by mass or less, relative to 100% by mass of the solid content of the low refractive index layer 14. When the content of hollow silica particles 22 in the low refractive index layer 14 is 6.0% by mass, relative to 100% by mass of the solid content of the low refractive index layer 14, excellent anti-reflection properties can be obtained. From this perspective, the content of hollow silica particles 22 in the low refractive index layer 14 is more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 30% by mass or more, relative to 100% by mass of the solid content of the low refractive index layer 14. Furthermore, when the content of hollow silica particles 22 in the low refractive index layer 14 is 49.9% by mass or less, relative to 100% by mass of the solid content of the low refractive index layer 14, deterioration in scratch resistance is suppressed. From this perspective, the content of hollow silica particles 22 in the low refractive index layer 14 is more preferably 45% by mass or less, and even more preferably 40% by mass or less, relative to 100% by mass of the solid content of the low refractive index layer 14.

The total amount of inorganic oxide particles 18 and hollow silica particles 22 in the low refractive index layer 14 is preferably 10% by mass or more and 50% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14. When the total amount of inorganic oxide particles 18 and hollow silica particles 22 in the low refractive index layer 14 is 10% by mass or more, based on 100% by mass of the solid content of the low refractive index layer 14, excellent scratch resistance can be obtained. From this perspective, the total amount of inorganic oxide particles 18 and hollow silica particles 22 in the low refractive index layer 14 is more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the solid content of the low refractive index layer 14. On the other hand, when the total amount of inorganic oxide particles 18 and hollow silica particles 22 in the low refractive index layer 14 is 50% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14, the inorganic oxide particles 18 and hollow silica particles 22 can be sufficiently retained in the low refractive index layer 14, resulting in excellent scratch resistance. From this perspective, the total amount of inorganic oxide particles 18 and hollow silica particles 22 in the low refractive index layer 14 is more preferably 48% by mass or less, even more preferably 46% by mass or less, and particularly preferably 43% by mass or less, relative to 100% by mass of the solid content of the low refractive index layer 14.

Fluorine-containing compounds can function as antifouling agents. They also improve the surface slipperiness of the low refractive index layer 14, thereby contributing to improved scratch resistance. Examples of fluorine-containing compounds include (meth)acrylates containing perfluoroalkyl groups. Examples of such compounds include "KY-1203" manufactured by Shin-Etsu Chemical Co., Ltd., "Megafac RS-75" manufactured by DIC, "Optoo DAC-HP" manufactured by Daikin Industries, Ltd., and "Ftergent 601AD" manufactured by Neos. These fluorine-containing compounds can prevent the adhesion of dirt and fingerprints and make them easier to remove.

The content of the fluorine-containing compound in the low refractive index layer 14 is preferably 1.0% by mass or more and 15.0% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14. When the content of the fluorine-containing compound in the low refractive index layer 14 is 1.0% by mass or more, based on 100% by mass of the solid content of the low refractive index layer 14, the surface slipperiness of the low refractive index layer 14 is improved, and scratch resistance is also improved. Furthermore, antifouling properties are improved. From this perspective, the content of the fluorine-containing compound in the low refractive index layer 14 is more preferably 2.0% by mass or more, and even more preferably 3.0% by mass or more, based on 100% by mass of the solid content of the low refractive index layer 14. When the content of the fluorine-containing compound in the low refractive index layer 14 is 15.0% by mass or less, based on 100% by mass of the solid content of the low refractive index layer 14, deterioration in scratch resistance is suppressed. From this viewpoint, the content of the fluorine-containing compound in the low refractive index layer 14 is more preferably 13.0% by mass or less, even more preferably 10.0% by mass or less, and particularly preferably 5.0% by mass or less, relative to 100% by mass of the solid content of the low refractive index layer 14.

The average thickness d of the low refractive index layer 14 is preferably in the range of 60 to 160 nm, more preferably in the range of 70 to 140 nm, and even more preferably in the range of 80 to 120 nm. Within this range, good luminous reflectance can be obtained and light reflection can be reduced. The average thickness of the low refractive index layer 14 is the thickness of the relatively smooth portion in the thickness direction where inorganic oxide particles 18 are not present.

The low refractive index layer 14 may contain additives as needed. Such additives include antifouling agents, dispersants, leveling agents, defoaming agents, thixotropic agents, antibacterial agents, flame retardants, slip agents, and refractive index adjusters.

The low refractive index layer 14 can be formed using a composition containing inorganic oxide particles 18, hollow silica particles 22, a fluorine-containing compound, and a binder resin. The fluorine-containing compound and binder resin preferably have a UV-reactive group. Examples of the UV-reactive group include a (meth)acryloyl group. When the fluorine-containing compound and binder resin have a UV-reactive group, the scratch resistance of the low refractive index layer 14 and the scratch resistance of the anti-reflection film 10 are improved. When the binder resin has a UV-reactive group (UV-curable resin), the composition for forming the low refractive index layer 14 preferably contains a photopolymerization initiator. The composition for forming the low refractive index layer 14 may contain a solvent, if necessary. The binder resin of the low refractive index layer 14 may be a UV-curable resin, a non-UV-curable resin, or a combination of a UV-curable resin and a non-UV-curable resin.

Non-UV curable resins include thermoplastic resins and thermosetting resins. Thermoplastic resins include polyester resins, polyether resins, polyolefin resins, and polyamide resins. Thermosetting resins include unsaturated polyester resins, epoxy resins, alkyd resins, and phenolic resins.

Examples of photopolymerization initiators include alkylphenone-based, acylphosphine oxide-based, and oxime ester-based photopolymerization initiators. Examples of alkylphenone-based photopolymerization initiators include 2,2'-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one. Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and the like. Examples of oxime ester photopolymerization initiators include 1,2-octanedione, 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime), and ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime). These photopolymerization initiators may be used alone or in combination of two or more.

The content of the photopolymerization initiator is preferably in the range of 0.1 to 10% by mass, based on the total solid content of the composition for forming the low refractive index layer 14. It is more preferably in the range of 1 to 5% by mass.

Solvents used in the composition for forming the low refractive index layer 14 include alcohol-based solvents such as ethylene glycol monomethyl ether (EGM), propylene glycol monomethyl ether (PGM), and diethylene glycol monobutyl ether; ketone-based solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone, and acetone; aromatic solvents such as toluene and xylene; and amide-based solvents such as N-methylpyrrolidone, acetamide, and dimethylformamide. These solvents may be used alone or in combination.

(Method for manufacturing anti-reflection film)
The antireflection film 10 can be produced by applying a composition for forming a hard coat layer 16 onto the surface of the substrate film 12, drying the composition as necessary, and curing the composition by irradiation with energy rays such as ultraviolet light to form the hard coat layer 16 on the surface of the substrate film 12, and then applying a composition for forming a low refractive index layer 14 onto the surface of the hard coat layer 16, drying the composition as necessary, and curing the composition by irradiation with energy rays such as ultraviolet light to form the low refractive index layer 14 on the surface of the hard coat layer 16. In this case, the surface of the substrate film 12 may be subjected to a surface treatment before coating in order to improve the adhesion between the substrate film 12 and the hard coat layer 16. Examples of surface treatments include corona treatment, plasma treatment, hot air treatment, ozone treatment, and ultraviolet treatment.

The composition that forms the hard coat layer 16 and the composition that forms the low refractive index layer 14 can be applied using various coating methods, such as reverse gravure coating, direct gravure coating, die coating, bar coating, wire bar coating, roll coating, spin coating, dip coating, spray coating, knife coating, and kiss coating, or various printing methods, such as inkjet printing, offset printing, screen printing, and flexographic printing.

The drying process is not particularly limited as long as it can remove the solvents used in the coating liquid, but it is preferably carried out at a temperature of 50 to 150°C for approximately 10 to 180 seconds. A drying temperature of 50 to 120°C is particularly preferred.

For ultraviolet irradiation, a high-pressure mercury lamp, an electrodeless (microwave type) lamp, a xenon lamp, a metal halide lamp, or any other ultraviolet irradiation device can be used. If necessary, ultraviolet irradiation may be carried out in an inert gas atmosphere such as nitrogen. The ultraviolet irradiation dose is not particularly limited, but is preferably 50 to 800 mJ/ ^cm² , and more preferably 100 to 300 mJ/ ^cm² .

From the viewpoint of good finger sliding properties and scratch resistance, the arithmetic mean roughness Sa of the surface of the low refractive index layer 14 is preferably 1.0 to 20 nm, more preferably 3.0 to 15 nm, and even more preferably 5.0 to 10 nm.

From the viewpoint of good visibility, the haze of the anti-reflection film 10 is preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less.

The lower the luminous reflectance of the anti-reflection film 10, the better, more preferably 2.0% or less, and even more preferably 1.0% or less.

The anti-reflection film 10 configured as described above comprises a substrate film 12, a hard coat layer 16 formed on the surface of the substrate film 12, and a low refractive index layer 14 (anti-reflection layer) formed on the surface of the hard coat layer 16. The hard coat layer 16 is composed of a cured product of an ionizing radiation-curable composition containing a (meth)acrylate compound and a polyfunctional secondary thiol. Thanks to the contribution of this hard coat layer 16, the anti-reflection film 10 has excellent scratch resistance.

<Other forms of anti-reflection film>
The antireflection film according to the present invention is not limited to the configuration of the antireflection film 10 according to the first embodiment. Other embodiments of the antireflection film according to the present invention will be described below.

Second Embodiment
2 shows an antireflection film 20 according to a second embodiment. The antireflection film 20 according to the second embodiment has a substrate film 12, a hard coat layer 16 formed on the surface of the substrate film 12, a high refractive index layer 17 formed on the surface of the hard coat layer 16, and a low refractive index layer 14 formed on the surface of the high refractive index layer 17. The antireflection film 20 has, in order from the substrate film 12 side, the substrate film 12, the hard coat layer 16, the high refractive index layer 17, and the low refractive index layer 14. In this structure, the low refractive index layer 14 and the high refractive index layer 17 serve as antireflection layers.

The anti-reflection film 20 according to the second embodiment differs from the anti-reflection film 10 according to the first embodiment in that it has a high-refractive index layer 17 between the hard coat layer 16 and the low-refractive index layer 14. Other than this, it is similar to the anti-reflection film 10 according to the first embodiment, and a description of the similar configuration will be omitted.

The high refractive index layer 17 can be formed by appropriately selecting from the materials described for the hard coat layer 16. The refractive index of the high refractive index layer 17 is preferably in the range of 1.55 to 1.80, and more preferably in the range of 1.60 to 1.70. The refractive index of the high refractive index layer 17 is measured at a wavelength of 589.3 nm. The refractive index of the high refractive index layer 17 can be adjusted by the selection and amount of binder resin, inorganic particles, and resin particles, etc.

The average thickness of the high refractive index layer 17 varies depending on the refractive index setting, but by making it, for example, between 50 nm and 200 nm, the anti-reflection function can be further enhanced.

In the anti-reflection film 10 according to the first embodiment described above, the low-refractive index layer 14 formed on the surface of the hard coat layer 16 constitutes the anti-reflection layer. In the anti-reflection film 20 according to the second embodiment described here, the high-refractive index layer 17 and the low-refractive index layer 14 are laminated in this order on the surface of the hard coat layer 16 to constitute the anti-reflection layer. However, the configuration of the anti-reflection layer is not particularly limited as long as it is a layer that can reduce reflection. For example, a medium-refractive index layer may be further provided between the hard coat layer 16 and the high-refractive index layer 17 of the anti-reflection film 20 according to the second embodiment, resulting in a three-layer anti-reflection layer. The medium-refractive index layer has a refractive index between that of the low-refractive index layer 14 and the high-refractive index layer 17, and providing the medium-refractive index layer further enhances anti-reflection properties. Furthermore, an anti-fouling layer may be formed on the surface of the anti-reflection layer.

Regardless of the anti-reflection layer's configuration, it is preferable that at least the portion of the anti-reflection layer that contacts the hard coat layer 16 be composed of a material having a carbon-carbon double bond, preferably an ethylenic carbon-carbon double bond. This forms a bond between the thiol group of the polyfunctional secondary thiol contained in the hard coat layer 16 and the carbon-carbon double bond of the substrate film 12, improving adhesion between the anti-reflection layer and the hard coat layer 16 and providing a significant improvement in the scratch resistance of the anti-reflection film. For example, if the layer of the anti-reflection layer that contacts the hard coat layer 16 is composed of a cured product of an ionizing radiation-curable material containing (meth)acrylate, the carbon-carbon double bond of the (meth)acrylate can fulfill this role.

(Third embodiment)
3 shows an anti-reflection film 30 according to a third embodiment. The anti-reflection film 30 according to the third embodiment includes a substrate film 12, a hard coat layer 16 formed on one surface of the substrate film 12, and a low refractive index layer 14 formed on the surface of the hard coat layer 16. The substrate film 12 also includes a transparent adhesive layer 24 on the other surface thereof. A release film 26 is disposed on the surface of the transparent adhesive layer 24, as necessary. The release film 26 functions as a protective layer for the transparent adhesive layer 24 before use and is peeled off from the transparent adhesive layer 24 when in use.

The anti-reflection film 30 according to the third embodiment differs from the anti-reflection film 10 according to the first embodiment in that it has a transparent adhesive layer 24 on the other side of the substrate film 12. Other than this, it is the same as the anti-reflection film 10 according to the first embodiment, and a description of the similar configuration will be omitted.

The transparent adhesive layer 24 is used to attach the anti-reflection film 30 to the surface of a display or the like with good adhesion. Furthermore, by virtue of having the transparent adhesive layer 24, the anti-reflection film 30 has the effect of preventing the glass of a display or the like from shattering. In other words, the anti-reflection film 30 also functions as a shatterproof film.

The adhesive composition forming the transparent adhesive layer 24 can contain known adhesive resins such as acrylic adhesives, silicone adhesives, and urethane adhesives. Among these, acrylic adhesives are preferred from the standpoints of optical transparency and heat resistance. The adhesive composition preferably contains a crosslinking agent to increase the cohesive strength of the transparent adhesive layer 24. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and chelate-based crosslinking agents.

The pressure-sensitive adhesive composition may contain additives as needed. Examples of additives include known additives such as plasticizers, silane coupling agents, surfactants, antioxidants, fillers, cure accelerators, and cure retarders. Furthermore, from the standpoint of productivity, the composition may be diluted with an organic solvent.

The thickness of the transparent adhesive layer 24 is not particularly limited, but is preferably in the range of 5 to 100 μm, and more preferably in the range of 10 to 50 μm.

The transparent adhesive layer 24 can be formed by a method in which the adhesive composition is directly applied to the other surface of the base film 12; a method in which the adhesive composition is applied to the surface of the release film 26 and then transferred to the other surface of the base film 12; or a method in which the adhesive composition is applied to the surface of a first release film and then a second release film is attached, and one of the release films is peeled off and then transferred to the other surface of the base film 12.

From the perspective of preventing glass from shattering, the transparent adhesive layer 24 preferably has an adhesive strength to glass of 4 N/25 mm or more. It is more preferably 6 N/25 mm or more, and even more preferably 10 N/25 mm or more.

(Fourth embodiment)
4 shows an anti-reflection film 40 according to a fourth embodiment. The anti-reflection film 40 according to the fourth embodiment includes a substrate film 12, a hard coat layer 16 formed on one surface of the substrate film 12, a low refractive index layer 14 formed on the surface of the hard coat layer 16, and a protective film 32 disposed on the surface of the low refractive index layer 14 via an adhesive layer 28. The other surface of the substrate film 12 also includes a transparent adhesive layer 24. A release film 26 is disposed on the surface of the transparent adhesive layer 24, if necessary.

The anti-reflection film 40 according to the fourth embodiment differs from the anti-reflection film 30 according to the third embodiment in that it has a protective film 32 on the surface of the low refractive index layer 14 via an adhesive layer 28. Other than this, it is similar to the anti-reflection film 30 according to the third embodiment, and a description of the similar configuration will be omitted.

The protective film 32 prevents scratches on the surface of the low refractive index layer 14 during handling, such as continuous processing by a roll process or bonding to a display. The protective film 32 is attached to the surface of the low refractive index layer 14 via the adhesive layer 28. After processing, the protective film 32 is peeled off from the surface of the low refractive index layer 14 together with the adhesive layer 28. For this reason, the adhesive layer 28 is adjusted so that the adhesive strength between the protective film 32 and the adhesive layer 28 is stronger than the adhesive strength between the low refractive index layer 14 and the adhesive layer 28, allowing for interfacial peeling between the low refractive index layer 14 and the adhesive layer 28.

The material constituting the protective film 32 can be selected as appropriate from among the materials exemplified for constituting the base film 12. The thickness of the protective film 32 is not particularly limited, but can be in the range of 2 to 500 μm, or 2 to 200 μm.

The adhesive that forms the adhesive layer 28 is not particularly limited, and suitable materials include acrylic adhesives, silicone adhesives, and urethane adhesives. Acrylic adhesives are particularly suitable due to their excellent transparency and heat resistance. The acrylic adhesive is preferably formed from an adhesive composition containing a (meth)acrylic polymer and a crosslinking agent.

(Meth)acrylic polymers are homopolymers or copolymers of (meth)acrylic monomers. Examples of (meth)acrylic monomers include alkyl group-containing (meth)acrylic monomers, carboxyl group-containing (meth)acrylic monomers, and hydroxyl group-containing (meth)acrylic monomers.

Examples of alkyl group-containing (meth)acrylic monomers include (meth)acrylic monomers having an alkyl group containing 2 to 30 carbon atoms. The alkyl group containing 2 to 30 carbon atoms may be linear, branched, or cyclic. Specific examples of alkyl group-containing (meth)acrylic monomers include isostearyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, decyl (meth)acrylate, isononyl (meth)acrylate, nonyl (meth)acrylate, isooctyl (meth)acrylate, octyl (meth)acrylate, isobutyl (meth)acrylate, n-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, propyl (meth)acrylate, ethyl (meth)acrylate, and methyl (meth)acrylate.

Carboxyl group-containing (meth)acrylic monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate. The carboxyl group may be located at the end of the alkyl chain or in the middle of the alkyl chain.

Examples of hydroxyl group-containing (meth)acrylic monomers include hydroxylauryl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxyethyl (meth)acrylate. The hydroxyl group may be located at the end or in the middle of the alkyl chain.

The (meth)acrylic monomer that forms the (meth)acrylic polymer may be any one of the above, or a combination of two or more.

Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, metal alkoxide-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents. These crosslinking agents may be used alone or in combination of two or more.

In addition to the (meth)acrylic polymer and crosslinking agent, the adhesive composition may contain other additives. Examples of other additives include crosslinking accelerators, crosslinking retarders, tackifiers, antistatic agents, silane coupling agents, plasticizers, release aids, pigments, dyes, wetting agents, thickeners, UV absorbers, preservatives, antioxidants, metal deactivators, alkylating agents, and flame retardants. These are selected and used appropriately depending on the application and purpose of the adhesive.

The thickness of the adhesive layer 28 is not particularly limited, but is preferably in the range of 1 to 10 μm, and more preferably in the range of 2 to 7 μm.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the spirit of the present invention.

For example, in the above embodiment, it is described that the surface of the base film 12 may be subjected to a surface treatment, but instead of the surface treatment, an easy-adhesion layer may be provided on the surface of the base film 12.

As shown in Figure 4, the protective film 32 is shown as being added to the anti-reflection film 30 of the third embodiment shown in Figure 3, but it may also be added to the anti-reflection film 10 of the first embodiment shown in Figure 1 or the anti-reflection film 20 of the second embodiment shown in Figure 2.

Furthermore, various functional layers such as a gas barrier improving layer, an antistatic layer, and an oligomer block layer may be provided on the surface of the base film 12 before each layer is formed.

An antistatic layer is provided for purposes such as reducing adhesion of surrounding dust and other particles due to peeling electrification and frictional electrification. The antistatic layer is preferably a layer made of an antistatic layer-forming composition containing an antistatic agent.

Examples of antistatic agents include cationic antistatic agents such as quaternary ammonium salts and pyridinium salts; anionic antistatic agents such as alkali metal salts of sulfonic acid, phosphoric acid, and carboxylic acid; amphoteric antistatic agents such as amino acid-based and amino acid sulfate-based; nonionic antistatic agents such as amino alcohol-based, glycerin-based, and polyethylene glycol-based; ionic compounds; conductive polymers such as polyacetylene and polythiophene-based; conductive particles such as metal oxide particles and carbon nanotubes; and conductive fibers. Among these, antistatic agents that combine dopants with conductive polymers such as polyacetylene and polythiophene, as well as metal particles and metal oxide particles, are preferred from the standpoints of low humidity dependency and prevention of bleed-out from the antistatic layer.

Specific examples of antistatic agents made from the above-mentioned conductive polymers include conductive polymers such as polyacetylene, polyaniline, polythiophene, polypyrrole, polyphenylene sulfide, poly(1,6-heptadiyne), polybiphenylene (polyparaphenylene), polyparaphenylene sulfide, polyphenylacetylene, poly(2,5-thienylene), and derivatives thereof, with polythiophene-based conductive organic polymers (e.g., 3,4-ethylenedioxythiophene (PEDOT)) being preferred. These may be used alone as antistatic agents, or in combinations of two or more.

The content of the antistatic agent is preferably in the range of 1 to 50% by mass, based on the total solid content of the antistatic layer-forming composition. It is more preferably in the range of 5 to 40% by mass, and even more preferably in the range of 10 to 20% by mass. A content of 1% by mass or more can impart good antistatic properties, while a content of 50% by mass or less can produce a highly transparent film with good total light transmittance.

The antistatic layer may contain a binder resin. There are no particular restrictions on the binder resin, as long as it is compatible with or can be mixed and dispersed in the antistatic agent, and it may be a curable resin or a thermoplastic resin.

Examples of thermoplastic resins include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyimide resins such as polyimide and polyamideimide; polyamide resins such as polyamide 6, polyamide 6,6, polyamide 12, and polyamide 11; polyvinylidene fluoride; acrylic resins; vinyl resins such as polyvinyl alcohol; and urethane resins.
As the curable resin, the same material as that used to form the hard coat layer 16 can be used.

From the viewpoint of preventing static buildup, the thickness of the antistatic layer is preferably 1 nm to 5 μm, more preferably 10 nm to 1 μm, and even more preferably 30 nm to 300 nm.

The present invention will be explained in detail below using examples and comparative examples.

<Preparation of hard coat layer-forming composition>
Each component was blended to obtain the composition shown in Table 1 (mass % of the total solid content), and ethyl acetate was added to obtain the solid content concentration shown in Table 1 to prepare a composition for forming a hard coat layer.

The materials used as components of the composition for forming a hard coat layer are as follows.
UV-curable resin 1 - DIC "Luxidia ESS-620", urethane acrylate resin, solvent: ethyl acetate, solid content: 79% by mass
UV-curable resin 2—“Aronix M-933” manufactured by Toagosei Co., Ltd., an acrylate reaction product of pentaerythritol, mainly composed of pentaerythritol triacrylate, hydroxyl value: 250 to 300 mg KOH/g, solid content: 100% by mass
Multifunctional secondary thiol - "Karenz MT PE1" manufactured by Showa Denko, a mixture of pentaerythritol tetrakis(3-mercaptobutyrate) and pentaerythritol tris(3-mercaptobutyrate), solid content: 100% by mass
Leveling agent - "Ftergent 602A" manufactured by Neos, fluorine-based leveling agent, solvent: ethyl acetate, solid content: 50% by mass
Photopolymerization initiator—"Omnirad 127" manufactured by IGM Resins B.V., 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one

<Preparation of composition for forming low refractive index layer>
The components were blended so that, in terms of mass % relative to the total solid content, the ultraviolet curable resin was 55 mass %, the alumina sol was 3.8 mass %, the fluorine-containing compound was 8 mass %, the hollow silica particles were 30 mass %, and the photopolymerization initiator was 3 mass %, and the solid content concentration was adjusted to 3 mass % using a solvent (MEK/PGM = 1/3), thereby preparing a composition for forming a low refractive index layer.

The materials used as components of the composition for forming the low refractive index layer are as follows.
・UV curable resin - "Aronix MT-3041" manufactured by Toagosei Co., Ltd., polyfunctional acrylate, solid content concentration: 100% by mass
Alumina sol - Toyochem's "Lioduras KT-110AL", 25% by mass of alumina particles (average particle size: 110 nm), 15% by mass of photosensitive monomer and resin, solvent (MEK, cyclohexanone, aliphatic solvent)
Fluorine-containing compound - "KY-1203" manufactured by Shin-Etsu Chemical Co., Ltd., perfluoroalkyl group-containing (meth)acrylate, solvent: MIBK, solid content: 20% by mass
Hollow silica particles - "Sururia 4320" manufactured by JGC Catalysts and Chemicals, average particle size: 60 nm, solvent: MIBK, solid content: 20% by mass
Photopolymerization initiator - the above "Omnirad 127"

<Preparation of Composition for Forming High Refractive Index Layer>
A solvent (MEK/PGM=1/1) was added to an ultraviolet-curable resin composition "Lioduras TYZ65-01" (manufactured by Toyochem, acrylic resin, containing zirconium oxide (average particle size 80 nm), photopolymerization initiator, solvent (cyclohexanone, methyl isobutyl ketone, propylene glycol monomethyl ether), solids concentration 35% by mass) so that the solids concentration was 8.5% by mass (concentration relative to the entire composition for forming a high refractive index layer), to prepare a composition for forming a high refractive index layer.

<Preparation of Hard Coat Layer>
For each of Examples 1 to 5 and Comparative Example 1, a hard coat layer-forming composition was applied to a substrate film (Toray's "Lumirror #50-U403," a polyethylene terephthalate film, 50 μm thick) using a #4 wire bar. After drying at 80°C for 3 minutes, the composition was irradiated with ultraviolet light at a light intensity of 80 mJ/ ^cm2 using an electrodeless (microwave) lamp to form a hard coat layer.

<Preparation of high refractive index layer>
In Example 5, a composition for forming a high refractive index layer was applied onto the surface of the hard coat layer using a #4 wire bar, and after drying at 80°C for 3 minutes, a high refractive index layer was formed by irradiating the composition with ultraviolet light at a light intensity of 150 mJ/ ^cm2 using an electrodeless (microwave) lamp.

<Preparation of low refractive index layer>
A low refractive index layer was formed on the surface of the hard coat layer in Examples 1 to 4 and Comparative Example 1, and on the surface of the high refractive index layer in Example 5. In this case, the composition for forming the low refractive index layer was applied using a #4 wire bar and dried at 80°C for 60 seconds, and then irradiated with ultraviolet light at a light intensity of 150 mJ/ ^cm2 using an electrodeless (microwave) lamp in a nitrogen atmosphere to form a low refractive index layer.

An anti-reflection film was produced in this manner. The thicknesses of the hard coat layer, high refractive index layer, and low refractive index layer were measured by spectral interferometry using a Filmetrics F20 Film Thickness Measurement System, and the results are shown in Table 1.

<Evaluation method>
(Scratch resistance)
Using a flat abrasion tester (Daiei Scientific Instruments Manufacturing Co., Ltd. "DAS-400"), steel wool #0000 (manufactured by Japan Steel Wool Co., Ltd.) fixed to a 20 mm x 20 mm flat abrader was placed on the surface of the low refractive index layer of the anti-reflective film and reciprocated. The stroke length of the test stand was 50 mm, the test stand reciprocation speed was 60 reciprocations/min, and the anti-reflective film was reciprocated 1,500 times with a load of 1.0 kg. After the test, anti-reflective films with scratches of 10 mm or more in length were evaluated as having low scratch resistance (×). Furthermore, films with scratches less than 10 mm in length but no scratches of 10 mm or more in length were evaluated as having high scratch resistance (◯). Scratches of this magnitude are not a practical problem. Furthermore, films with no scratches were evaluated as having very high scratch resistance (◎).

(Pencil hardness)
The pencil hardness of each sample surface was measured using a pencil hardness tester (manufactured by Tester Sangyo Co., Ltd.) according to the method specified in JIS K 5600-5-4. The test was repeated with a test load of 1 kg and varying the hardness of the pencil. The maximum hardness at which scratches or dents occurred with the same pencil within one out of five times was taken as the evaluation value.

(Visibility reflectance)
The back surface of the prepared antireflection film (the surface opposite to the low refractive index layer) was roughened with #400 sandpaper and painted over with black paint. The 5° specular reflectance of the surface of the low refractive index layer was measured using an ultraviolet-visible-near-infrared spectrophotometer (Shimadzu Corporation, "UV-3600"), and the luminous reflectance was calculated by multiplying this measurement value by the relative luminous efficiency value.

(Haze (Hz), Total Light Transmittance (Tt))
The haze (Hz) and total light transmittance (Tt) of the entire anti-reflection film were measured using a "Haze Meter NDH7000" manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with the method of JIS-K7136.

<Evaluation results>
Table 1 below shows the component compositions of the hard coat layers and the thicknesses of each layer, as well as the evaluation results for Examples 1 to 5 and Comparative Example 1.

In Comparative Example 1, in which the curable composition constituting the hard coat layer did not contain a polyfunctional secondary thiol, the evaluation results for scratch resistance were poor. In contrast, in Examples 1 to 5, in which the curable composition constituting the hard coat layer contained a polyfunctional secondary thiol, high scratch resistance was obtained. This demonstrates that the inclusion of a polyfunctional secondary thiol in the curable composition constituting the hard coat layer improves the scratch resistance of the anti-reflective film. In particular, Examples 1, 3, and 5, in which the content of the polyfunctional secondary thiol exceeded 5% by mass, achieved extremely high scratch resistance. Furthermore, all of Examples 1 to 5 achieved a pencil hardness of H or higher, a luminous reflectance of 2.0% or less, a haze of 1.5 or less, and a total light transmittance of 90% or more, which are sufficiently high performances for an anti-reflective film. Note that the scratch resistance evaluation test was conducted under stricter conditions than those in Patent Document 1, and the sample in Comparative Example 1 is also considered to have sufficient scratch resistance according to the standards of Patent Document 1.

As described above, in an anti-reflection film having a substrate film, a hard coat layer formed on the surface of the substrate film, and an anti-reflection layer formed on the surface of the hard coat layer, the hard coat layer is composed of a cured product of an ionizing radiation-curable composition containing a (meth)acrylate compound and a polyfunctional secondary thiol, and the hard coat layer contributes to the anti-reflection film having excellent scratch resistance.

The above describes an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the spirit of the present invention.

10, 20, 30, 40 Anti-reflection film 12 Base film 14 Low refractive index layer 16 Hard coat layer 17 High refractive index layer 18 Inorganic oxide particles 22 Hollow silica particles 24 Transparent adhesive layer 26 Release film 28 Adhesive layer 32 Protective film

Claims (7)

a substrate film, a hard coat layer formed on a surface of the substrate film, and an anti-reflection layer formed on the surface of the hard coat layer;
The hard coat layer is
a (meth)acrylate compound;
A polyfunctional secondary thiol,
The composition is composed of a cured product of an ionizing radiation-curable composition comprising
the substrate film and the antireflection layer are each in direct contact with the hard coat layer without any other layer therebetween ;
the base film and the antireflection layer are made of a material having a carbon-carbon double bond at least at the portions in contact with the hard coat layer ,
An antireflection film, wherein the antireflection layer is made of a cured product of an ionizing radiation-curable material containing (meth)acrylate at least in a portion in contact with the hard coat layer. The ionizing radiation-curable composition contains, as the (meth)acrylate compound:
a polyfunctional urethane (meth)acrylate compound;
a pentaerythritol (meth)acrylate compound having a hydroxyl value of 200 mgKOH/g or more and 350 mgKOH/g or less;
The anti-reflection film according to claim 1 , comprising: The anti-reflection film according to claim 2, wherein the content of the pentaerythritol (meth)acrylate compound in the ionizing radiation-curable composition is 15% by mass or more and 75% by mass or less, relative to 100% by mass of the solids content of the (meth)acrylate compound. The anti-reflection film according to any one of claims 1 to 3, wherein the polyfunctional secondary thiol is trifunctional or higher. The antireflection film according to any one of claims 1 to 4, wherein the content of the polyfunctional secondary thiol in the ionizing radiation-curable composition is 3% by mass or more and 35% by mass or less, based on 100% by mass of the solids content. The antireflection film according to claim 5 , wherein the content of the polyfunctional secondary thiol in the ionizing radiation curable composition is 7% by mass or more and 15% by mass or less, relative to 100% by mass of the solid content. 7. The antireflection film according to claim 1, wherein at least a portion of the substrate film that is in contact with the hard coat layer is made of a material having an ethylenic carbon-carbon double bond as the carbon-carbon double bond.