WO2024070686A1

WO2024070686A1 - Anti-reflection film and image display device

Info

Publication number: WO2024070686A1
Application number: PCT/JP2023/033344
Authority: WO
Inventors: 一生田中; 遼太郎横井; 達也大井; 翔橋本; 翔太長命; 幸大宮本; 豊角田
Original assignee: 日東電工株式会社
Priority date: 2022-09-28
Filing date: 2023-09-13
Publication date: 2024-04-04
Also published as: TW202422116A

Abstract

An anti-reflection film (10) comprises a transparent film base (11), a hard coat layer (12), a primer layer (13), and an anti-reflection layer (14), in the stated order. The anti-reflection layer (14) is a laminate of a plurality of thin films having different refractive indices. The primer layer (13) is a thin film containing indium tin oxide as the main component. In the primer layer (13), the amount of tin oxide is at least 15 wt% with respect to the total amount of indium oxide and tin oxide.

Description

Anti-reflection film and image display device

The present invention relates to an anti-reflection film and an image display device.

Anti-reflection films are placed on the viewing side of image display devices such as liquid crystal displays and organic EL displays to prevent degradation of image quality due to reflection of external light and to improve contrast. Anti-reflection films have an anti-reflection layer made of a laminate of multiple thin films with different refractive indices on a transparent film substrate.

For example, Patent Document 1 discloses an anti-reflective film in which a primer layer containing indium tin oxide (ITO) is provided on a hard coat layer, and an anti-reflective layer made of multiple thin films is formed on top of the primer layer.

JP 2005-266665 A

The inventors have found through their research that when an anti-reflective film having a typical ITO film as a primer layer is brought into contact with an acid such as sulfuric acid, delamination (for example, delamination between the anti-reflective layer and the hard coat layer) is likely to occur. For this reason, it may be difficult to apply an anti-reflective film having a typical ITO film as a primer layer to applications requiring acid resistance (resistance to corrosion caused by acid). Examples of applications requiring acid resistance include automotive applications (on-board applications) in which sulfuric acid is used in the battery fluid.

In view of the above, the present invention aims to provide an anti-reflection film with excellent acid resistance, and an image display device using the anti-reflection film.

<Aspects of the present invention>
The present invention includes the following aspects.

[1] An antireflection film having a transparent film substrate, a hard coat layer, a primer layer, and an antireflection layer in this order,
the antireflection layer is a laminate of a plurality of thin films having different refractive indices,
The primer layer is a thin film containing indium tin oxide as a main component, and the amount of tin oxide relative to the total amount of indium oxide and tin oxide is 15% by weight or more.

[2] The anti-reflection film described in [1], wherein the primer layer contains tin oxide in an amount of 60% by weight or less relative to the total amount of indium oxide and tin oxide.

[3] The anti-reflection film according to [1] or [2], wherein the thickness of the primer layer is 0.5 nm or more and 20 nm or less.

[4] The anti-reflection film according to any one of [1] to [3], further comprising an antifouling layer disposed on the side of the anti-reflection layer opposite the primer layer.

[5] The anti-reflection film according to any one of [1] to [4], wherein the hard coat layer contains particles having a number average primary particle diameter of less than 1.0 μm.

[6] The anti-reflection film according to any one of [1] to [5], further comprising a pressure-sensitive adhesive layer disposed on the opposite side of the transparent film substrate from the hard coat layer.

[7] An image display device comprising an image display panel and an anti-reflection film according to any one of [1] to [6] above, arranged on the viewing side of the image display panel.

The present invention provides an anti-reflection film with excellent acid resistance, and an image display device using the anti-reflection film.

1 is a cross-sectional view showing an example of an anti-reflection film according to the present invention. FIG. 2 is a cross-sectional view showing another example of the antireflection film according to the present invention. 1 is a cross-sectional view showing an example of an image display device according to the present invention.

The following provides a detailed description of preferred embodiments of the present invention, but the present invention is not limited to these. In addition, all academic and patent literature described in this specification is incorporated herein by reference.

First, the terms used in this specification are explained. "Refractive index" refers to the refractive index for light with a wavelength of 550 nm in an atmosphere at a temperature of 23°C. The "principal surface" of a layered material (more specifically, a transparent film substrate, a hard coat layer, a primer layer, an anti-reflective layer, an antifouling layer, an adhesive layer, etc.) refers to a surface perpendicular to the thickness direction of the layered material. Unless otherwise specified, the numerical value of the thickness (film thickness) of each layer constituting the anti-reflective film is the arithmetic average value of 10 measured values obtained by randomly selecting 10 measurement points from an image of a cross section cut in the thickness direction of the layer and measuring the thickness of the selected 10 measurement points.

Unless otherwise specified, the "major component" of a thin film (layer) means the component that is contained in the largest amount in the thin film by weight. "Solids" refers to the non-volatile components in the composition, e.g., components other than the solvent.

Unless otherwise specified, the number-average primary particle size of particles is the number-average circle-equivalent diameter (Heywood diameter: diameter of a circle having the same area as the projected area of a primary particle) of 100 primary particles measured using a scanning electron microscope and image processing software (e.g., "ImageJ" manufactured by the National Institutes of Health, USA).

Hereinafter, the compound and its derivatives may be collectively referred to by adding "system" after the compound name. In addition, when the compound name is followed by "system" to represent the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative, unless otherwise specified. Unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more types.

The drawings referred to in the following explanation mainly show each component in a schematic manner for ease of understanding, and the size, number, shape, etc. of each component shown may differ from the actual size due to the convenience of creating the drawings. Also, for the convenience of explanation, in drawings explained later, the same components as those in previously explained drawings may be given the same reference numerals and their explanation may be omitted.

First embodiment: anti-reflection film
The anti-reflection film according to the first embodiment of the present invention is an anti-reflection film (laminate) having a transparent film substrate, a hard coat layer, a primer layer, and an anti-reflection layer in this order. The anti-reflection layer is a laminate of multiple thin films having different refractive indices. The primer layer is a thin film mainly composed of indium tin oxide, and the amount of tin oxide relative to the total of indium oxide and tin oxide is 15% by weight or more.

Hereinafter, the amount of tin oxide (unit: weight %) relative to the total of indium oxide and tin oxide in the primer layer (100 weight %) may be referred to simply as "the amount of tin oxide in the primer layer" or "the amount of tin oxide."

The anti-reflection film according to the first embodiment has the above-mentioned configuration and therefore has excellent acid resistance. The reason for this is presumed to be as follows.

In the anti-reflective film according to the first embodiment, a thin film containing indium tin oxide as a main component is provided as a primer layer for improving adhesion between the hard coat layer and the anti-reflective layer. Furthermore, the primer layer of the anti-reflective film according to the first embodiment contains 15% by weight or more of tin oxide. Therefore, in the anti-reflective film according to the first embodiment, the primer layer tends to be less susceptible to corrosion by acid. Therefore, the anti-reflective film according to the first embodiment has excellent acid resistance because adhesion between the hard coat layer and the anti-reflective layer is ensured even when it comes into contact with acid.

In addition, since the anti-reflection film according to the first embodiment has the above-mentioned configuration, it is possible to ensure adhesion between layers when irradiated with ultraviolet rays. Hereinafter, the property of ensuring adhesion between layers when irradiated with ultraviolet rays may be referred to as "weather resistance."

In the first embodiment, in order to obtain an anti-reflection film with superior acid resistance, the amount of tin oxide in the primer layer is preferably 18% by weight or more, more preferably 20% by weight or more, even more preferably 22% by weight or more, even more preferably 24% by weight or more, and may be 25% by weight or more, 30% by weight or more, 35% by weight or more, or 40% by weight or more.

In the first embodiment, in order to obtain an anti-reflective film with excellent transparency, the amount of tin oxide in the primer layer is preferably 60% by weight or less, more preferably 55% by weight or less, even more preferably 50% by weight or less, and may be 45% by weight or less.

The configuration of the anti-reflection film according to the first embodiment will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of an anti-reflection film according to the first embodiment. The anti-reflection film 10 shown in FIG. 1 has a transparent film substrate 11, a hard coat layer 12, a primer layer 13, and an anti-reflection layer 14, in this order. The primer layer 13 is in contact with both the hard coat layer 12 and the anti-reflection layer 14. The primer layer 13 is a thin film containing indium tin oxide as a main component, and the amount of tin oxide relative to the total of indium oxide and tin oxide is 15% by weight or more.

The anti-reflection film 10 further includes an anti-fouling layer 19 disposed on the side of the anti-reflection layer 14 opposite the primer layer 13 side. In other words, the anti-reflection film 10 includes a transparent film substrate 11, a hard coat layer 12, a primer layer 13, an anti-reflection layer 14, and an anti-fouling layer 19 in this order.

The anti-reflection layer 14 has four layers, namely, a high refractive index layer 15, a low refractive index layer 16, a high refractive index layer 17, and a low refractive index layer 18, in this order from the primer layer 13 side. Details of the high refractive index layer and the low refractive index layer will be described later. The anti-reflection layer of the anti-reflection film is not limited to a four-layer structure like the anti-reflection layer 14, and may be a two-layer structure, a three-layer structure, a five-layer structure, or a stacked structure of six or more layers. The anti-reflection layer of the anti-reflection film is preferably an alternating laminate of two or more high refractive index layers and two or more low refractive index layers. In order to reduce reflection at the air interface, it is preferable that the outermost layer (the layer farthest from the hard coat layer 12) of the anti-reflection layer of the anti-reflection film is a low refractive index layer.

The anti-reflection film according to the first embodiment may have a layer structure different from that of the anti-reflection film 10 shown in FIG. 1. For example, the anti-reflection film according to the first embodiment may be an anti-reflection film 20 further including an adhesive layer 21 arranged on the side opposite the hard coat layer 12 of the transparent film substrate 11, as shown in FIG. 2.

The adhesive constituting the adhesive layer 21 is not particularly limited, and can be appropriately selected and used, for example, a transparent adhesive having a base polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate-vinyl chloride copolymer, modified polyolefin, epoxy resin, fluororesin, natural rubber, synthetic rubber, etc. The thickness of the adhesive layer 21 is not particularly limited, but from the viewpoint of achieving both a thin layer property and adhesiveness, it is preferably 5 μm or more and 100 μm or less.

A release liner (not shown) may be temporarily attached to the main surface of the adhesive layer 21 opposite the transparent film substrate 11. The release liner protects the surface of the adhesive layer 21, for example, until the anti-reflection film 20 is bonded to an image display panel 101 (see FIG. 3) described below. The release liner is preferably made of a plastic film made of acrylic, polyolefin, cyclic polyolefin, polyester, or the like. The release liner has a thickness of, for example, 5 μm or more and 200 μm or less. The surface of the release liner is preferably subjected to a release treatment. Examples of the material of the release agent used in the release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty acid amide-based materials.

The configuration of the anti-reflection film according to the first embodiment has been described above with reference to the drawings, but the anti-reflection film according to the present invention is not limited to the above-mentioned configuration.

For example, the anti-reflection film according to the present invention may be an anti-reflection film that does not have an anti-fouling layer. In addition, the anti-reflection film according to the present invention may have an optically functional layer that is different from the layers included in the above-mentioned configuration (transparent film substrate, hard coat layer, primer layer, anti-reflection layer, and anti-fouling layer).

Next, we will explain the elements of the anti-reflection film according to the first embodiment.

[Transparent film substrate]
The transparent film substrate is, for example, a transparent resin film having flexibility. Examples of materials constituting the transparent film substrate include polyester resin, polyolefin resin, polystyrene resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, cellulose resin, norbornene resin, polyarylate resin, and polyvinyl alcohol resin. Examples of polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of cellulose resin include triacetyl cellulose (TAC). These materials may be used alone or in combination of two or more. As the material of the transparent film substrate, from the viewpoint of transparency and strength, one selected from the group consisting of polyester resin, polyolefin resin, and cellulose resin is preferable, one selected from the group consisting of PET, COP, and TAC is more preferable, and TAC is even more preferable. In other words, as the transparent film substrate, a type of film selected from the group consisting of polyester resin film, polyolefin resin film, and cellulose resin film is preferable, a type of film selected from the group consisting of PET film, COP film, and TAC film is more preferable, and a TAC film is even more preferable.

From the viewpoint of strength, the thickness of the transparent film substrate is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. From the viewpoint of handleability, the thickness of the transparent film substrate is preferably 300 μm or less, and more preferably 200 μm or less.

One or both main surfaces of the transparent film substrate may be subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

The total light transmittance (JIS K 7375-2008) of the transparent film substrate is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more and 100% or less, from the viewpoint of improving the transparency of the anti-reflection film.

[Hard coat layer]
The hard coat layer is a layer that enhances mechanical properties such as hardness and elastic modulus of the anti-reflection film. The hard coat layer is, for example, made of a cured product of a curable resin composition (composition for forming a hard coat layer). Examples of the curable resin contained in the curable resin composition include polyester resin, acrylic resin, urethane resin, urethane acrylate resin, amide resin, silicone resin, epoxy resin, and melamine resin. These curable resins may be used alone or in combination of two or more kinds. From the viewpoint of increasing the hardness of the hard coat layer, the curable resin is preferably one or more selected from the group consisting of acrylic resin and urethane acrylate resin, and more preferably urethane acrylate resin.

In addition, examples of the curable resin composition include an ultraviolet-curable resin composition and a thermosetting resin composition. From the viewpoint of improving the productivity of the anti-reflection film, the curable resin composition is preferably an ultraviolet-curable resin composition. The ultraviolet-curable resin composition includes one or more selected from the group consisting of an ultraviolet-curable monomer, an ultraviolet-curable oligomer, and an ultraviolet-curable polymer. A specific example of the ultraviolet-curable resin composition is the composition for forming a hard coat layer described in JP 2016-179686 A.

The curable resin composition may also contain fine particles. By blending fine particles in the curable resin composition, it is possible to adjust the hardness, surface roughness, refractive index, and anti-glare properties of the hard coat layer. Examples of fine particles include metal (or semi-metal) oxide particles, glass particles, and organic particles. Examples of materials for metal (or semi-metal) oxide particles include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Examples of materials for organic particles include polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate.

The curable resin composition may also contain particles having a number average primary particle diameter of less than 1.0 μm (hereinafter, sometimes referred to as "nanoparticles") as the fine particles. In other words, the hard coat layer may contain nanoparticles. When the hard coat layer is made of a cured product of a curable resin composition containing nanoparticles, fine irregularities are formed on the surface of the hard coat layer, which tends to improve adhesion between the hard coat layer and a layer (e.g., a primer layer) formed thereon.

From the viewpoint of forming a fine uneven shape that contributes to improved adhesion, the number average primary particle diameter of the nanoparticles is preferably 20 nm or more and 80 nm or less, more preferably 25 nm or more and 70 nm or less, and even more preferably 30 nm or more and 60 nm or less.

Inorganic oxides are preferred as nanoparticle materials. Examples of inorganic oxides include oxides of metals (or semi-metals), such as silicon oxide (silica), titanium oxide, aluminum oxide, zirconium oxide, niobium oxide, zinc oxide, tin oxide, cerium oxide, and magnesium oxide. The inorganic oxide may be a composite oxide of multiple (semi-)metals. Among the inorganic oxides listed above, silicon oxide is preferred because of its high adhesion-improving effect. In other words, silicon oxide particles (silica particles) are preferred as nanoparticles. Functional groups such as acrylic groups and epoxy groups may be introduced onto the surface of inorganic oxide particles as nanoparticles in order to improve adhesion and affinity with resins.

The amount of nanoparticles in the hard coat layer is preferably 5 parts by weight or more, and may be 10 parts by weight or more, 20 parts by weight or more, or 30 parts by weight or more, based on 100 parts by weight of the curable resin. If the amount of nanoparticles is 5 parts by weight or more, the adhesion to the layer formed on the hard coat layer can be further improved. The upper limit of the amount of nanoparticles in the hard coat layer is, for example, 90 parts by weight, preferably 80 parts by weight, and may be 70 parts by weight, based on 100 parts by weight of the curable resin.

The thickness of the hard coat layer is preferably 1 μm or more, more preferably 2 μm or more, from the viewpoint of increasing the hardness of the hard coat layer. The thickness of the hard coat layer is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 35 μm or less, and even more preferably 30 μm or less, from the viewpoint of ensuring the flexibility of the anti-reflection film.

The main surface of the hard coat layer opposite the transparent film substrate side may be subjected to a surface modification treatment. Examples of surface modification treatments include plasma treatment, corona treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment. In order to increase the adhesion between the hard coat layer and a layer (e.g., a primer layer described below) provided on the side opposite the transparent film substrate side of the hard coat layer, it is preferable that the main surface of the hard coat layer opposite the transparent film substrate side is subjected to a plasma treatment.

[Primer layer]
The primer layer is a layer for enhancing adhesion between the hard coat layer and the anti-reflection layer. In this embodiment, the primer layer is a thin film mainly composed of indium tin oxide (ITO). By containing ITO as a main component of the primer layer, a primer layer having excellent transparency can be obtained while enhancing adhesion between the hard coat layer and the anti-reflection layer. In addition, by containing ITO as a main component of the primer layer, the anti-reflection film can have an appropriate antistatic property.

The primer layer may contain oxides other than indium oxide and tin oxide, but in order to further improve adhesion between the hard coat layer and the anti-reflective layer, the content of ITO in the primer layer is preferably 90% by weight or more, and more preferably 99% by weight or more, based on the total amount of the primer layer. Hereinafter, a thin film containing ITO as the main component may be referred to as an "ITO layer."

In order to ensure the transparency of the primer layer while improving the adhesion between the hard coat layer and the anti-reflection layer, the thickness of the primer layer is preferably 0.5 nm or more and 20 nm or less, more preferably 0.5 nm or more and 10 nm or less, and even more preferably 1.0 nm or more and 10 nm or less.

[Anti-reflection layer]
The antireflection layer is made of two or more thin layers with different refractive indexes. In general, the optical film thickness (product of refractive index and thickness) of the thin film is adjusted so that the inverted phases of incident light and reflected light cancel each other out. By making the antireflection layer a multilayer laminate of two or more thin films with different refractive indexes, the reflectance can be reduced in a wide wavelength range of visible light.

The thin film material constituting the anti-reflection layer may be a metal (or semi-metal) oxide, nitride, fluoride, etc. The anti-reflection layer is preferably an alternating laminate of high refractive index layers and low refractive index layers.

The high refractive index layer has a refractive index of, for example, 1.9 or more, preferably 2.0 or more. Examples of materials for the high refractive index layer include titanium oxide, niobium oxide (Nb ₂ O ₅ , etc.), zirconium oxide, tantalum oxide, zinc oxide, indium oxide, and antimony-doped tin oxide (ATO). Among these, at least one selected from the group consisting of titanium oxide and niobium oxide is preferred. The low refractive index layer has a refractive index of, for example, 1.6 or less, preferably 1.5 or less. Examples of materials for the low refractive index layer include silicon oxide (SiO ₂ , etc.), titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, and lanthanum fluoride. Among these, silicon oxide is preferred. In particular, it is preferred to alternately stack a niobium oxide thin film as the high refractive index layer and a silicon oxide thin film as the low refractive index layer. In addition to the low refractive index layer and the high refractive index layer, a medium refractive index layer having a refractive index of more than 1.6 and less than 1.9 may be provided.

The thickness of each of the high and low refractive index layers is preferably 5 nm to 200 nm, and more preferably 10 nm to 150 nm. The thickness of each layer can be designed so that the reflectance of visible light is small, depending on the refractive index and layer structure. For example, the layer structure of the high and low refractive index layers can be a four-layer structure consisting of, from the hard coat layer side, a high refractive index layer with an optical thickness of 20 nm to 55 nm, a low refractive index layer with an optical thickness of 25 nm to 55 nm, a high refractive index layer with an optical thickness of 80 nm to 270 nm, and a low refractive index layer with an optical thickness of 100 nm to 150 nm.

When the anti-reflection layer is a four-layer alternating laminate consisting of niobium oxide thin films as high refractive index layers and silicon oxide thin films as low refractive index layers, the anti-reflection layer may be configured to have, in this order from the hard coat layer side, a niobium oxide thin film with a thickness of 5 nm to 20 nm, a silicon oxide thin film with a thickness of 10 nm to 40 nm, a niobium oxide thin film with a thickness of 65 nm to 120 nm, and a silicon oxide thin film with a thickness of 60 nm to 100 nm.

In order to obtain an anti-reflective film with excellent bending resistance, the thickness of the anti-reflective layer is preferably 140 nm or more and 280 nm or less, more preferably 170 nm or more and 280 nm or less, even more preferably 180 nm or more and 260 nm or less, and even more preferably 190 nm or more and 250 nm or less. In this specification, the "thickness of the anti-reflective layer" refers to the sum of the thicknesses of the layers that make up the anti-reflective layer (total thickness).

[Anti-stain layer]
The anti-reflection film preferably has an anti-soiling layer on the side opposite to the primer layer of the anti-reflection layer, and more preferably has an anti-soiling layer as the outermost layer of the anti-reflection film. By providing the anti-soiling layer, for example, the influence of contamination from the external environment (fingerprints, hand dirt, dust, etc.) can be reduced, and contaminants attached to the surface of the anti-reflection film can be easily removed.

In order to prevent a decrease in the anti-reflection performance of the anti-reflection layer, it is preferable that the anti-smudge layer has a small difference in refractive index from the outermost layer of the anti-reflection layer (e.g., a low refractive index layer). The refractive index of the anti-smudge layer is preferably 1.6 or less, and more preferably 1.55 or less.

As the material of the antifouling layer, a fluorine-containing compound is preferred. The fluorine-containing compound can contribute to lowering the refractive index while having excellent antifouling properties. Among them, an alkoxysilane compound containing a perfluoropolyether skeleton is preferred because it has excellent water repellency and can exhibit high antifouling properties. As an alkoxysilane compound containing a perfluoropolyether skeleton, for example, an alkoxysilane compound having a plurality of linear or branched perfluoroalkylene oxide units having 1 to 4 carbon atoms can be mentioned. As an example of the linear or branched perfluoroalkylene oxide unit having 1 to 4 carbon atoms, for example, a perfluoromethylene oxide unit (-CF ₂ O-), a perfluoroethylene oxide unit (-CF ₂ CF ₂ O-), a perfluoropropylene oxide unit (-CF ₂ CF ₂ CF ₂ O-), a perfluoroisopropylene oxide unit (-CF(CF ₃ )CF ₂ O-), and the like can be mentioned.

The thickness of the antifouling layer is, for example, 2 nm or more and 20 nm or less. The thicker the antifouling layer, the more improved the antifouling properties tend to be. The thickness of the antifouling layer is preferably 5 nm or more, and more preferably 6 nm or more. On the other hand, from the viewpoint of improving antiglare properties, the thickness of the antifouling layer is preferably 15 nm or less.

[Preferred embodiment of anti-reflection film]
In order to obtain an antireflection film having excellent acid resistance while ensuring weather resistance and transparency, the antireflection film according to the first embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, and even more preferably satisfies the following condition 3.
Condition 1: The amount of tin oxide in the primer layer is 15% by weight or more and 60% by weight or less.
Condition 2: The above condition 1 is satisfied, and the thickness of the primer layer is 0.5 nm or more and 20 nm or less.
Condition 3: The above condition 2 is satisfied, and the hard coat layer contains particles having a number average primary particle diameter of less than 1.0 μm.

[Method of manufacturing anti-reflection film]
Next, a description will be given of a preferred method for producing the anti-reflection film according to the first embodiment. Hereinafter, the preferred method for producing the anti-reflection film according to the first embodiment may be referred to as production method M.

Manufacturing method M includes, for example, a primer layer forming step and an anti-reflective layer forming step. Manufacturing method M may include steps (other steps) other than the primer layer forming step and the anti-reflective layer forming step. Examples of the other steps include a hard coat layer forming step, a surface treatment step of the hard coat layer, and an anti-fouling layer forming step, which will be described later.

The following describes each step in one example of manufacturing method M.

(Hard Coat Layer Forming Process)
The hard coat layer forming process is a process of forming a hard coat layer on one main surface of a transparent film substrate. For example, a curable resin composition (composition for forming a hard coat layer) is applied to one main surface of a transparent film substrate, and the hard coat layer is formed by removing the solvent and curing the resin as necessary. The composition for forming a hard coat layer includes, for example, the above-mentioned curable resin and a polymerization initiator (e.g., a photopolymerization initiator), and includes a solvent capable of dissolving or dispersing these components as necessary.

In addition to the above components, the composition for forming the hard coat layer may contain additives such as nanoparticles, particles with a number-average primary particle size of 1.0 μm or more, leveling agents, viscosity adjusters (thixotropic agents, thickeners, etc.), antistatic agents, antiblocking agents, dispersants, dispersion stabilizers, antioxidants, UV absorbers, defoamers, surfactants, and lubricants.

As the coating method of the composition for forming a hard coat layer, any suitable method such as a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, a fountain coating method, a comma coating method, etc. may be adopted. The drying temperature of the coating film after coating may be set to an appropriate temperature depending on the composition of the composition for forming a hard coat layer, for example, 50°C or more and 150°C or less. When the resin component in the composition for forming a hard coat layer is a thermosetting resin, the coating film is cured by heating. When the resin component in the composition for forming a hard coat layer is a photocurable resin, the coating film is cured by irradiating it with active energy rays such as ultraviolet rays. The integrated light amount of the irradiation light is preferably 100 mJ/ ^cm2 or more and 500 mJ/ ^cm2 or less.

(Surface treatment process of hard coat layer)
In the surface treatment process of the hard coat layer, the main surface of the hard coat layer opposite to the transparent film substrate side is surface modified. Examples of the surface modification treatment include plasma treatment, corona treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment. When the surface modification treatment is plasma treatment, for example, argon gas is used as the inert gas. The discharge power in the plasma treatment is, for example, 50 W or more and 300 W or less. The pressure condition in the plasma treatment is, for example, 0.1 Pa or more and 2.5 Pa or less.

(Primer layer forming step)
The primer layer forming step is a step of forming (forming) a primer layer on the hard coat layer. The method of forming the primer layer is not particularly limited, and may be either a wet coating method or a dry coating method. Dry coating methods such as vacuum deposition, CVD, and sputtering are preferred because they can form a thin film with a uniform thickness. From the viewpoint of increasing productivity, the method of forming the primer layer is preferably a method of forming a film using a roll-to-roll sputtering film forming device (roll-to-roll sputtering method).

In the roll-to-roll sputtering method, for example, a primer layer and an anti-reflection layer can be continuously formed while a long film (for example, a transparent film substrate on which a hard coat layer has been formed) is transported in the longitudinal direction (MD direction). In the sputtering method, film formation is performed while introducing an inert gas such as argon, and if necessary, a reactive gas such as oxygen, into the film formation chamber. When forming an ITO layer as a primer layer, the ITO layer can be formed by sputtering using either an oxide target or reactive sputtering using a metal (or semi-metal) target.

Power sources for carrying out the sputtering method include, for example, DC power sources, AC power sources, RF power sources, and MFAC power sources (AC power sources with a frequency band of several kHz to several MHz). The discharge power in the sputtering method is, for example, 1 kW to 100 kW, and preferably 1 kW to 50 kW. The surface temperature of the film-forming roll when carrying out the sputtering method is, for example, -25°C to 25°C, and preferably -20°C to 0°C. The pressure in the film-forming chamber when carrying out the sputtering method is preferably 0.01 Pa to 10 Pa, more preferably 0.05 Pa to 5 Pa, and even more preferably 0.1 Pa to 1 Pa.

(Anti-reflection layer forming process)
The anti-reflective layer forming step is a step of forming an anti-reflective layer on the primer layer. The method of forming the anti-reflective layer is not particularly limited, and may be either a wet coating method or a dry coating method. Since a thin film with a uniform thickness can be formed, a dry coating method such as a vacuum deposition method, a CVD method, or a sputtering method is preferable. From the viewpoint of increasing productivity, the method of forming the anti-reflective layer is preferably a method of forming a film using a roll-to-roll sputtering film forming device (roll-to-roll sputtering method). When performing the sputtering method in the anti-reflective layer forming step, the film forming conditions can be appropriately set, for example, among the conditions described above (primer layer forming step).

(Anti-stain layer forming process)
The antifouling layer forming step is a step of forming an antifouling layer on the side opposite to the primer layer side of the antireflection layer. In the antifouling layer forming step, for example, a fluorine-containing compound is used as a material to form the antifouling layer by a dry coating method. Examples of the dry coating method include a vacuum deposition method, a sputtering method, and a CVD method, and the vacuum deposition method is preferred.

Second embodiment: Image display device
Next, an image display device according to a second embodiment of the present invention will be described. The image display device according to the second embodiment includes an image display panel and the anti-reflection film according to the first embodiment, which is disposed on the viewing side of the image display panel. Hereinafter, the description of the contents that overlap with the first embodiment will be omitted.

FIG. 3 is a cross-sectional view showing an example of an image display device according to the second embodiment. The image display device 100 shown in FIG. 3 includes an image display panel 101 and an anti-reflection film 10, which is an example of the anti-reflection film according to the first embodiment, arranged on the viewing side (upper side in FIG. 3) of the image display panel 101. In the image display device 100, a transparent film substrate 11 of the anti-reflection film 10 and the image display panel 101 are bonded together via an adhesive layer 21.

Examples of the image display panel 101 include image display panels that include image display cells such as liquid crystal cells and organic EL cells.

The image display device according to the second embodiment has an anti-reflection film disposed on the viewing side of the image display panel, which reduces reflection of external light and provides excellent visibility. In addition, the image display device according to the second embodiment has excellent acid resistance because it includes the anti-reflection film according to the first embodiment.

The following describes examples of the present invention, but the present invention is not limited to the following examples.

<Preparation of Antireflection Film of Example 1>
[Hard coat layer forming process]
A urethane acrylate-based ultraviolet-curing resin composition containing silica particles having a number-average primary particle size of 50 nm ("Beamset 577" manufactured by Arakawa Chemical Industries Co., Ltd.), 0.1 parts by weight of silicone resin particles ("Tospearl 130" manufactured by Momentive Performance Materials Japan, Inc., average particle size: 3.0 μm, refractive index: 1.43, true specific gravity: 1.32), 4.0 parts by weight of crosslinked polymethyl methacrylate (PMMA) particles ("Techpolymer SSX-103" manufactured by Sekisui Chemical Co., Ltd., average particle size: 3.0 μm, refractive index: 1.50, true specific gravity: 1.20), 2.0 parts by weight of a thixotropic agent ("Sumecton SAN" manufactured by Kunimine Kogyo Co., Ltd., a synthetic smectite which is an organic clay), and a photopolymerization initiator (IGM Resins Co., Ltd. "Omnirad 127") 3.0 parts by weight and a silicone-based leveling agent (Kyoeisha Chemical Co., Ltd. "Polyflow LE303") 0.15 parts by weight were mixed and diluted with butyl acetate to obtain a hard coat layer forming composition HC1 having a solid content concentration of 40% by weight. Next, the hard coat layer forming composition HC1 obtained by the above procedure was applied to one main surface of a TAC film (FUJITAC TG60UL manufactured by FUJIFILM Corporation, thickness: 60 μm) as a transparent film substrate to form a coating film. Next, this coating film was dried by heating at a temperature of 60 ° C. for 60 seconds, and then cured by ultraviolet irradiation. When irradiating ultraviolet rays, a high-pressure mercury lamp was used as a light source, ultraviolet rays with a wavelength of 365 nm were used, and the accumulated light amount was set to 300 mJ / cm ^2. As a result, a hard coat layer with a thickness of 6 μm was formed on the TAC film.

[Surface treatment process of hard coat layer]
Next, the surface of the hard coat layer was plasma-treated by a roll-to-roll type plasma treatment device while conveying the TAC film on which the hard coat layer was formed under a vacuum atmosphere of 1.0 Pa. During the plasma treatment, argon gas was used as an inert gas, and the discharge power was set to 100 W. As a result, a laminate (hereinafter, sometimes referred to as "optical film F1") including the TAC film and the plasma-treated hard coat layer was obtained.

[Primer layer forming step]
Next, the optical film F1 was introduced into a roll-to-roll sputtering deposition apparatus, and the pressure in the deposition chamber was reduced to 1×10 ⁻⁴ Pa. Next, while conveying the optical film F1, argon gas and oxygen gas were introduced in a volume ratio of 100:13, the surface temperature of the deposition roll was set to −8° C., and an ITO layer (primer layer) having a thickness of 1.5 nm was formed on the hard coat layer by a sputtering method. For the formation of the primer layer, an ITO target containing indium oxide and tin oxide in a weight ratio of 85:15 was used as the target material. In addition, when forming the film by the sputtering method, the power source was an MFAC power source, the discharge power was 4.5 kW, and the pressure in the deposition chamber was 0.2 Pa.

[Anti-reflection layer forming process]
Following the formation of the primer layer, while conveying the optical film F1 after the formation of the primer layer using a roll-to-roll sputtering deposition apparatus, the following layers were deposited on the primer layer in this order by sputtering: 1st layer: 12 nm thick Nb ₂ O _5- layer (refractive index: 2.33), 2nd layer: 27 nm thick SiO _2- layer (refractive index: 1.46), 3rd layer: 108 nm thick Nb ₂ O _5- layer, and 4th layer: 86 nm thick SiO _2- layer. This resulted in a 4-layer structure (4-layer structure consisting of the 1st layer, the 2nd layer, the 3rd layer, and the 4th layer) antireflection layer formed on the primer layer. In the deposition of each of the 1st to 4th layers, the surface temperature of the deposition roll was set to -8°C, the power source was an MFAC power source, and the pressure in the deposition chamber was set to 0.7 Pa. In addition, in the deposition of the first layer, a Nb target was used, argon gas and oxygen gas were introduced in a volume ratio of 100:5, and the discharge power was set to 13.0 kW. In the deposition of the second layer, a Si target was used, argon gas and oxygen gas were introduced in a volume ratio of 100:33, and the discharge power was set to 25.5 kW. In the deposition of the third layer, a Nb target was used, argon gas and oxygen gas were introduced in a volume ratio of 100:13, and the discharge power was set to 27.5 kW. In the deposition of the fourth layer, a Si target was used, argon gas and oxygen gas were introduced in a volume ratio of 100:30, and the discharge power was set to 20.5 kW.

[Anti-stain layer forming process]
A coating agent ("SHIN-ETSU SUBELYN KY1903-1" manufactured by Shin-Etsu Chemical Co., Ltd., active ingredient: an alkoxysilane compound containing a perfluoropolyether skeleton) was dried and solidified and used as a deposition source, and an antifouling layer having a thickness of 8 nm was formed on the antireflection layer by a vacuum deposition method at a heating temperature of the deposition source of 260° C. In this way, an antireflection film (antireflection film of Example 1) including a TAC film, a hard coat layer, a primer layer, an antireflection layer, and an antifouling layer in this order was obtained.

<Preparation of anti-reflection film of Example 2>
An anti-reflection film of Example 2 was obtained by the same preparation method as in Example 1, except that in the primer layer formation step, an ITO target containing indium oxide and tin oxide in a weight ratio of 80:20 was used as the target material.

<Preparation of anti-reflection film of Example 3>
An anti-reflection film of Example 3 was obtained by the same preparation method as in Example 1, except that in the primer layer formation step, an ITO target containing indium oxide and tin oxide in a weight ratio of 75:25 was used as the target material.

<Preparation of anti-reflection film of Example 4>
An anti-reflection film of Example 4 was obtained by the same preparation method as in Example 1, except that in the primer layer formation step, an ITO target containing indium oxide and tin oxide in a weight ratio of 70:30 was used as the target material.

<Preparation of anti-reflection film of Example 5>
An anti-reflection film of Example 5 was obtained by the same preparation method as in Example 1, except that in the primer layer formation step, an ITO target containing indium oxide and tin oxide in a weight ratio of 60:40 was used as the target material.

<Preparation of anti-reflection film of Comparative Example 1>
An anti-reflection film of Comparative Example 1 was obtained by the same preparation method as in Example 1, except that in the primer layer formation step, an ITO target containing indium oxide and tin oxide in a weight ratio of 90:10 was used as the target material.

<Preparation of Antireflection Film of Reference Example 1>
An antireflection film of Reference Example 1 was obtained by the same production method as in Example 1, except that the primer layer formation step was changed to the following procedure.

[Primer layer forming step of Reference Example 1]
The optical film F1 was introduced into a roll-to-roll sputtering deposition apparatus, and the pressure in the deposition chamber was reduced to 1×10 ⁻⁴ Pa. Next, while conveying the optical film F1, argon gas and oxygen gas were introduced in a volume ratio of 100:9, the surface temperature of the deposition roll was set to −8° C., and a SiOx layer (x<2) having a thickness of 3.0 nm was formed on the hard coat layer by a sputtering method. A Si target was used as a target material for forming the primer layer (SiOx layer). In addition, when forming the film by the sputtering method, the power source was an MFAC power source, the discharge power was 4.5 kW, and the pressure in the deposition chamber was 0.7 Pa.

<Preparation of anti-reflection film of Reference Example 2>
An antireflection film of Reference Example 2 was obtained by the same production method as in Example 1, except that the primer layer formation step was changed to the following procedure.

[Primer layer forming step of Reference Example 2]
The optical film F1 was introduced into a roll-to-roll sputtering deposition apparatus, and the pressure in the deposition chamber was reduced to 1×10 ⁻⁴ Pa. Next, while conveying the optical film F1, argon gas and oxygen gas were introduced in a volume ratio of 100:10, the surface temperature of the deposition roll was set to −8° C., and a TiOx layer (x<2) having a thickness of 1.5 nm was formed on the hard coat layer by sputtering. A Ti target was used as a target material for forming the primer layer (TiOx layer). In addition, when forming the film by sputtering, the power source was set to an MFAC power source, the discharge power was set to 4.5 kW, and the pressure in the deposition chamber was set to 0.7 Pa.

<Measurement and evaluation methods>
[Method for measuring the amount of tin oxide]
The amount of tin oxide in the primer layer of the antireflection film to be measured (specifically, any of the antireflection films of Examples 1 to 5 and Comparative Example 1) was measured by the following procedure. First, a primer layer having a thickness of 1.5 nm was formed on the hard coat layer of the optical film F1 under the same conditions as those for forming the primer layer of the antireflection film to be measured. Next, the elemental composition of the obtained primer layer was measured using a scanning X-ray fluorescence analyzer ("ZSX Primus II" manufactured by Rigaku Corporation). Then, the amount of tin oxide relative to the total amount of indium oxide and tin oxide (unit: weight %) was calculated.

[Method for evaluating acid resistance]
On the surface of the antifouling layer of the antireflection film to be evaluated (specifically, any of the antireflection films of Examples 1 to 5, Comparative Example 1, and Reference Examples 1 and 2), one drop of an aqueous sulfuric acid solution ("37% (1+3)-sulfuric acid" manufactured by Kishida Chemical Co., Ltd., sulfuric acid concentration: 37% by weight, water concentration: 63% by weight) was dropped with a dropper, and the film was allowed to stand for 22 hours in an atmosphere of a temperature of 23°C and a relative humidity of 50%. Next, the surface of the antifouling layer was washed with water, and the presence or absence of delamination in the antireflection film was visually confirmed. When no delamination was observed, the film was rated as A (excellent acid resistance). On the other hand, when delamination was observed, the film was rated as B (not excellent acid resistance).

[Weather resistance evaluation method]
First, a 5 mm thick glass plate was attached to the main surface of the TAC film side of the antireflection film to be evaluated (specifically, any of the antireflection films of Examples 1 to 5, Comparative Example 1, and Reference Examples 1 and 2) via an adhesive to obtain an evaluation sample. Next, the evaluation sample was placed in a weather resistance evaluation device (Iwasaki Electric Co., Ltd.'s "Eyesuper SUV-W161") and irradiated with ultraviolet light from the antifouling layer side under the following conditions.

(Ultraviolet light irradiation conditions)
Black Panel Temperature (BPT): 85°C
Relative humidity: 45%
UV intensity: 150mW/ ^cm2
Irradiation time: 32.5 hours

Next, 100 squares were formed on the antifouling layer side of the antireflection film after UV irradiation, and a cross-cut peel test was performed according to JIS K5400 (cross-cut test method). The number of peeled squares was counted, and the weather resistance was evaluated according to the following criteria. "Peeling" means that peeling occurred over 1/4 or more of the area of one square.
A: The number of peeled squares was 9 or less.
B: The number of peeled squares was 10 or more.

If the result was A, it was evaluated as having "excellent weather resistance." On the other hand, if the result was B, it was evaluated as having "not excellent weather resistance."

<Results>
Table 1 shows the type of oxide constituting the primer layer, the amount of tin oxide, the evaluation results of acid resistance, and the evaluation results of weather resistance for Examples 1 to 5, Comparative Example 1, and Reference Examples 1 and 2. In Table 1, "-" means that no measurement was performed.

As shown in Table 1, in Examples 1 to 5, the amount of tin oxide in the primer layer was 15% by weight or more. In Examples 1 to 5, the evaluation result for acid resistance was A. Therefore, the anti-reflection films of Examples 1 to 5 had excellent acid resistance.

As shown in Table 1, in Comparative Example 1, the amount of tin oxide in the primer layer was less than 15% by weight. In Comparative Example 1, the evaluation result for acid resistance was B. Therefore, the anti-reflection film of Comparative Example 1 did not have excellent acid resistance.

In terms of weather resistance, all were rated A (excellent weather resistance) except for Reference Example 2, which had a TiOx layer as the primer layer.

These results demonstrate that the present invention can provide an anti-reflection film with excellent acid resistance.

Reference Signs List

10, 20 Anti-reflection film 11 Transparent film substrate 12 Hard coat layer 13 Primer layer 14 Anti-reflection layer 19 Antifouling layer 21 Pressure-sensitive adhesive layer 100 Image display device 101 Image display panel

Claims

An antireflection film having a transparent film substrate, a hard coat layer, a primer layer, and an antireflection layer in this order,
the antireflection layer is a laminate of a plurality of thin films having different refractive indices,
The primer layer is a thin film containing indium tin oxide as a main component, and the amount of tin oxide relative to the total amount of indium oxide and tin oxide is 15% by weight or more.
The anti-reflection film according to claim 1, wherein the primer layer contains tin oxide in an amount of 60% by weight or less relative to the total amount of indium oxide and tin oxide.
The anti-reflection film according to claim 1, wherein the thickness of the primer layer is 0.5 nm or more and 20 nm or less.
The anti-reflection film according to claim 1, further comprising an anti-fouling layer disposed on the side of the anti-reflection layer opposite the primer layer.
The anti-reflection film according to claim 1, wherein the hard coat layer contains particles having a number-average primary particle diameter of less than 1.0 μm.
The anti-reflection film according to claim 1, further comprising an adhesive layer disposed on the opposite side of the transparent film substrate from the hard coat layer.
An image display device comprising: an image display panel; and the anti-reflection film according to claim 1 disposed on a viewing side of the image display panel.