Antireflection film and method for producing the same, and image display device

Abstract

To provide an antireflection film in which a crack hardly occurs in an antireflection layer and which exhibits excellent flex resistance even when stored in a bent state under high-temperature or high-temperature / high-humidity conditions, a method for producing the same and an image display device using the antireflection film.SOLUTION: An antireflection film (10) has a transparent film base material (11), a hard coat layer (12), and an antireflection layer (13) in this order. The dimension change ratio in a first direction from before to after a heat resistance test of the antireflection film (10) is preferably -0.10% to 0.10%. The dimension change ratio in the first direction from before to after a moist heat resistance test of the antireflection film (10) is preferably 0.01% to 0.20%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an antireflection film, a method for manufacturing the same, and an image display device.

Background Art

[0002] On the viewing side of an image display device such as a liquid crystal display or an organic EL display, an antireflection film is disposed for the purpose of preventing image quality degradation due to reflection of external light, improving contrast, and the like. The antireflection film includes an antireflection layer formed of a laminate of a plurality of thin films having different refractive indexes on a transparent film substrate.

[0003] For example, Patent Document 1 discloses an antireflection film including a SiO primer layer on a hard coat film, and an antireflection layer formed of an alternating laminate of a niobium oxide (Nb 2 O 5 ) layer as a high refractive index layer and a silicon oxide (SiO 2 ) layer as a low refractive index layer on the SiO primer layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, a foldable image display device (foldable display) including an organic EL panel using a foldable substrate (flexible substrate) such as a resin film has been put into practical use. As a cover window of the foldable display, for example, an antireflection film having an antireflection layer provided on a flexible substrate is used.

[0006] A foldable display is generally stored in a folded state. In the folded state, compressive stress is applied inside the folding location (bending location), and tensile stress is applied outside the bending location. When the display is folded with the display surface on the inside, the antireflection film is in a folded state (bent state) with the formation surface of the antireflection layer on the inside. When the display is stored in a bent state under high temperature or high temperature and high humidity conditions, fine cracks may occur in the antireflection layer, which causes a decrease in the visibility of the display.

[0007] In view of the above, an object of the present invention is to provide an antireflection film that is less likely to crack in the antireflection layer even when stored in a bent state under high temperature or high temperature and high humidity conditions, has excellent bend resistance, a method for manufacturing the same, and an image display device using the antireflection film. [Means for Solving the Problems]

[0008] [Aspects of the Present Invention] The present invention includes the following aspects.

[0009] [1] An antireflection film having a transparent film substrate, a hard coat layer, and an antireflection layer in this order, When a heat resistance test is performed by holding in an environment at a temperature of 85°C for 48 hours, the dimensional change rate in the direction of any one side before and after the heat resistance test is -0.10% or more and 0.10% or less. The antireflection film.

[0010] [2] The antireflection film according to [1] above, wherein the dimensional change rate in the direction orthogonal to the direction of the side before and after the heat resistance test is -0.10% or more and 0.10% or less.

[0011] [3] An antireflection film having a transparent film substrate, a hard coat layer, and an antireflection layer in this order, When a damp heat resistance test is performed by holding in an environment at a temperature of 60°C and a relative humidity of 95% for 48 hours, the dimensional change rate in the direction of any one side before and after the damp heat resistance test is 0.01% or more and 0.20% or less. The antireflection film.

[0012] [4] The dimensional change rate in the direction orthogonal to the direction of the side before and after the damp heat resistance test is 0.01% or more and 0.20% or less, the antireflection film according to [3] above.

[0013] [5] The transparent film substrate is a polyethylene terephthalate film, the antireflection film according to any one of [1] to [4] above.

[0014] [6] The thickness of the antireflection layer is 150 nm or more and 280 nm or less, the antireflection film according to any one of [1] to [5] above.

[0015] [7] Further comprising a primer layer disposed between the hard coat layer and the antireflection layer, the antireflection film according to any one of [1] to [6] above.

[0016] [8] Further comprising an antifouling layer disposed on the side of the antireflection layer opposite to the hard coat layer side, the antireflection film according to any one of [1] to [7] above.

[0017] [9] Further comprising an adhesive layer disposed on the side of the transparent film substrate opposite to the hard coat layer side, the antireflection film according to any one of [1] to [8] above.

[0018]

[10] An image display device comprising an image display panel and the antireflection film according to any one of [1] to [9] above disposed on the viewing side of the image display panel.

[0019]

[11] A method for manufacturing the antireflection film according to any one of [1] to [9] above, A step Sa of forming the antireflection layer on the side of the hard coat layer opposite to the transparent film substrate side by a roll-to-roll sputtering film forming apparatus, After the step Sa, a step Sb of heating the laminate on which the antireflection layer is formed, the method for manufacturing an antireflection film.

[0020]

[12] The method for manufacturing an antireflection film according to

[11] , wherein in the step Sb, the laminate is heated under the condition of a temperature of 110°C or higher.

Effects of the Invention

[0021] According to the present invention, it is possible to provide an antireflection film that is less likely to crack in the antireflection layer and has excellent bending resistance even when stored in a bent state under high temperature or high temperature and high humidity, a method for manufacturing the same, and an image display device using the antireflection film.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0023] Hereinafter, preferred embodiments of the present invention will be described. First, the terms used in this specification will be explained. The "refractive index" is the refractive index with respect to light having a wavelength of 550 nm in an atmosphere at a temperature of 23°C. The "main surface" of a layer-like object (more specifically, a transparent film substrate, a hard coat layer, an adhesive layer, etc.) refers to a plane orthogonal to the thickness direction of the layer-like object. The numerical value of the thickness (film thickness) of each layer constituting the antireflection film is the arithmetic mean value of 10 measurement values obtained by randomly selecting 10 measurement locations from an image of a cross-section obtained by cutting the layer in the thickness direction and measuring the thicknesses of the selected 10 measurement locations.

[0024] "The direction of any one side" means a direction parallel to any one of the four sides of the antireflection film of a rectangle or a square. Hereinafter, the direction of any one side of the antireflection film may be referred to as the "first direction". Also, the direction orthogonal to the first direction (specifically, the direction parallel to the side orthogonal to the first direction among the above four sides) may be referred to as the "second direction". The first direction is, for example, the conveyance direction of the film (hereinafter may be referred to as the "MD direction") when forming the antireflection layer by the roll-to-roll sputtering method described later. The second direction is, for example, the direction orthogonal to the conveyance direction of the film (hereinafter may be referred to as the "TD direction") when forming the antireflection layer by the roll-to-roll sputtering method described later.

[0025] Hereinafter, when comprehensively referring to a compound and its derivatives by attaching "system" after the compound name, it may be the case. Also, when representing a polymer name by attaching "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. The components, functional groups, etc. exemplified in this specification may be used alone or in combination of two or more unless otherwise specified.

[0026] In the drawings referred to in the following description, for easy understanding, each component is schematically shown mainly. The size, number, shape, etc. of each illustrated component may be different from the actual situation for convenience of drawing preparation. Also, for convenience of explanation, in the drawings described later, the same reference numerals may be given to the same components as those in the previously described drawings, and the description thereof may be omitted.

[0027] <First Embodiment: Antireflection Film> Hereinafter, as specific examples of the antireflection film according to the first embodiment of the present invention, the antireflection film ARF1 and the antireflection film ARF2 will be described. Both the antireflection film ARF1 and the antireflection film ARF2 are antireflection films (laminates) having a transparent film substrate, a hard coat layer, and an antireflection layer in this order. When the antireflection film ARF1 is subjected to a heat resistance test of being held in an environment at a temperature of 85°C for 48 hours, the dimensional change rate in the first direction before and after the heat resistance test is -0.10% or more and 0.10% or less. When the antireflection film ARF2 is subjected to a damp heat resistance test of being held in an environment at a temperature of 60°C and a relative humidity of 95% for 48 hours, the dimensional change rate in the first direction before and after the damp heat resistance test is 0.01% or more and 0.20% or less.

[0028] Since the shrinkage in the first direction of the antireflection film ARF1 is suppressed at high temperatures, even when stored in a bent state at high temperatures, cracks are less likely to occur in the antireflection layer, and it has excellent bend resistance. Also, since the shrinkage in the first direction of the antireflection film ARF2 is suppressed under high temperature and high humidity, even when stored in a bent state under high temperature and high humidity, cracks are less likely to occur in the antireflection layer, and it has excellent bend resistance. Hereinafter, when there is no need to distinguish, each of the antireflection film ARF1 and the antireflection film ARF2 will be referred to as the "antireflection film ARF". Also, the property that cracks are less likely to occur in the antireflection layer even when stored in a bent state at high temperatures may be simply referred to as "bend resistance at high temperatures". Also, the property that cracks are less likely to occur in the antireflection layer even when stored in a bent state under high temperature and high humidity may be simply referred to as "bend resistance under high temperature and high humidity".

[0029] Hereinafter, the high-temperature or high-temperature and high-humidity environment may be described as the "severe environment". Also, the property that cracks are unlikely to occur in the antireflection layer even when stored in a bent state under a severe environment may be simply described as the "flexure resistance under a severe environment". Further, the heat resistance test of holding the antireflection film for 48 hours in an environment at a temperature of 85°C may be simply described as the "heat resistance test". Also, the damp heat resistance test of holding the antireflection film for 48 hours in an environment at a temperature of 60°C and a relative humidity of 95% may be simply described as the "damp heat resistance test". Further, the heat resistance test or the damp heat resistance test may be described as the "severe environment test". Hereinafter, unless otherwise specified, the "severe environment test" is a test for the antireflection film.

[0030] Note that the relative humidity in the atmosphere of the heat resistance test is, for example, 1% or less, and may be 0.5% or less or 0.1% or less.

[0031] The dimensional change rate (unit: %) in the first direction or the second direction before and after the severe environment test is calculated according to the formula "dimensional change rate = 100×(L2 - L1) / L1", where L1 (unit: mm) is the length in the first direction or the second direction before the severe environment test, and L2 (unit: mm) is the length in the first direction or the second direction after the severe environment test. When the dimensional change rate in the first direction or the second direction < 0%, it means that the length in the first direction or the second direction becomes smaller due to the severe environment test. On the other hand, when the dimensional change rate in the first direction or the second direction > 0%, it means that the length in the first direction or the second direction becomes larger due to the severe environment test. The measurement method of the dimensional change rate is the same as or similar to the method described in the examples below.

[0032] In order to obtain the antireflection film ARF1 with excellent flexure resistance at high temperature, it is preferable that the dimensional change rate in the second direction before and after the heat resistance test is -0.10% or more and 0.10% or less.

[0033] In order to obtain the antireflection film ARF1 with excellent flexural resistance at high temperatures, it is preferable that the dimensional change rates in the first direction and the second direction before and after the heat resistance test are both -0.09% or more, more preferably -0.08% or more, and may also be -0.07% or more, -0.06% or more, or -0.05% or more. Also, in order to obtain the antireflection film ARF1 with excellent flexural resistance at high temperatures, it is preferable that the dimensional change rates in the first direction and the second direction before and after the heat resistance test are both 0.09% or less, more preferably 0.05% or less, and may also be 0.04% or less, 0.03% or less, 0.02% or less, or 0.01% or less. In order to obtain the antireflection film ARF1 with even more excellent flexural resistance at high temperatures, it is preferable that at least one of the dimensional change rates in the first direction and the second direction before and after the heat resistance test is 0.00% or more and 0.10% or less, more preferably 0.00% or more and 0.04% or less, even more preferably 0.00% or more and 0.03% or less, even more preferably 0.00% or more and 0.02% or less, and particularly preferably 0.00% or more and 0.01% or less.

[0034] In order to obtain the antireflection film ARF1 that is particularly excellent in flexural resistance at high temperatures, it is preferable that the dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0.10% or less, and the dimensional change rate in the second direction before and after the heat resistance test is -0.07% or more and 0.00% or less. It is more preferable that the dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0.04% or less, and the dimensional change rate in the second direction before and after the heat resistance test is -0.07% or more and 0.00% or less. It is still more preferable that the dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0.03% or less, and the dimensional change rate in the second direction before and after the heat resistance test is -0.06% or more and 0.00% or less. It is even more preferable that the dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0.02% or less, and the dimensional change rate in the second direction before and after the heat resistance test is -0.05% or more and 0.00% or less. It is particularly preferable that the dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0.01% or less, and the dimensional change rate in the second direction before and after the heat resistance test is -0.05% or more and 0.00% or less. When the dimensional change rates in the first direction and the second direction before and after the heat resistance test are within the above ranges, in order to further suppress the occurrence of cracks in the antireflection layer in a bent state at high temperatures, it is preferable to store the antireflection film ARF1 in a bent state in the first direction.

[0035] In order to obtain the antireflection film ARF2 that is even more excellent in flexural resistance under high temperature and high humidity, it is preferable that the dimensional change rate in the second direction before and after the damp heat resistance test is 0.01% or more and 0.20% or less.

[0036] In order to obtain the antireflection film ARF2 with excellent flex resistance under high temperature and high humidity, the dimensional change rates in the first direction and the second direction before and after the damp heat resistance test are preferably both 0.02% or more, more preferably 0.03% or more, and may be 0.04% or more, 0.05% or more, 0.06% or more, 0.07% or more, 0.08% or more, or 0.09% or more. Also, in order to obtain the antireflection film ARF2 with excellent flex resistance under high temperature and high humidity, the dimensional change rates in the first direction and the second direction before and after the damp heat resistance test are preferably both 0.15% or less, more preferably 0.14% or less, and still more preferably 0.13% or less. In order to obtain the antireflection film ARF2 with even more excellent flex resistance under high temperature and high humidity, the dimensional change rates in the first direction and the second direction before and after the damp heat resistance test are preferably both 0.05% or more and 0.13% or less, more preferably 0.06% or more and 0.13% or less, still more preferably 0.07% or more and 0.13% or less, even more preferably 0.08% or more and 0.13% or less, and particularly preferably 0.09% or more and 0.13% or less.

[0037] In order to obtain the antireflection film ARF2 which is particularly excellent in flexural resistance under high temperature and high humidity, it is preferable that the dimensional change rate in the first direction before and after the damp heat resistance test is 0.05% or more and 0.11% or less, and the dimensional change rate in the second direction before and after the damp heat resistance test is 0.10% or more and 0.13% or less. More preferably, the dimensional change rate in the first direction before and after the damp heat resistance test is 0.06% or more and 0.11% or less, and the dimensional change rate in the second direction before and after the damp heat resistance test is 0.11% or more and 0.13% or less. Even more preferably, the dimensional change rate in the first direction before and after the damp heat resistance test is 0.07% or more and 0.11% or less, and the dimensional change rate in the second direction before and after the damp heat resistance test is 0.11% or more and 0.13% or less. Even more preferably, the dimensional change rate in the first direction before and after the damp heat resistance test is 0.08% or more and 0.11% or less, and the dimensional change rate in the second direction before and after the damp heat resistance test is 0.11% or more and 0.13% or less. Particularly preferably, the dimensional change rate in the first direction before and after the damp heat resistance test is 0.09% or more and 0.11% or less, and the dimensional change rate in the second direction before and after the damp heat resistance test is 0.12% or more and 0.13% or less. When the dimensional change rates in the first direction and the second direction before and after the damp heat resistance test are within the above ranges, in order to further suppress the occurrence of cracks in the antireflection layer in a bent state under high temperature and high humidity, it is preferable to store the antireflection film ARF2 in a state of being bent in the first direction.

[0038] Hereinafter, the configuration of the antireflection film ARF will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the antireflection film ARF. The antireflection film 10 shown in FIG. 1 has a transparent film substrate 11, a hard coat layer 12, and an antireflection layer 13 in this order. When the antireflection film 10 is the antireflection film ARF1, the dimensional change rate in the first direction before and after the heat resistance test of the antireflection film 10 is -0.10% or more and 0.10% or less. When the antireflection film 10 is the antireflection film ARF2, the dimensional change rate in the first direction before and after the damp heat resistance test of the antireflection film 10 is 0.01% or more and 0.20% or less.

[0039] Further, the antireflection film 10 further includes a primer layer 18 disposed between the hard coat layer 12 and the antireflection layer 13, and an antifouling layer 19 disposed on the side of the antireflection layer 13 opposite to the hard coat layer 12 side. That is, the antireflection film 10 has a transparent film substrate 11, a hard coat layer 12, a primer layer 18, an antireflection layer 13, and an antifouling layer 19 in this order.

[0040] The antireflection layer 13 has four layers, i.e., a high refractive index layer 14, a low refractive index layer 15, a high refractive index layer 16, and a low refractive index layer 17, in this order from the hard coat layer 12 side (primer layer 18 side). Details of the high refractive index layer and the low refractive index layer will be described later. Note that the antireflection layer of the antireflection film ARF is not limited to a four-layer structure such as the antireflection layer 13, and may be a two-layer structure, a three-layer structure, a five-layer structure, or a laminated structure of six or more layers. The antireflection layer of the antireflection film ARF 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 antireflection layer of the antireflection film ARF is a low refractive index layer.

[0041] The antireflection film ARF may have a layer structure different from that of the antireflection film 10 shown in FIG. 1. For example, as shown in FIG. 2, the antireflection film ARF may be an antireflection film 20 further including an adhesive layer 21 disposed on the side of the transparent film substrate 11 opposite to the hard coat layer 12 side.

[0042] The adhesive constituting the adhesive layer 21 is not particularly limited, and for example, a transparent adhesive based on a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyvinyl ether, a vinyl acetate-vinyl chloride copolymer, a modified polyolefin, an epoxy resin, a fluororesin, a natural rubber, or a synthetic rubber can be appropriately selected and used. The thickness of the adhesive layer 21 is not particularly limited, but is preferably 5 μm or more and 100 μm or less from the viewpoint of achieving both thin layer properties and adhesiveness.

[0043] On the main surface of the pressure-sensitive adhesive layer 21 on the side opposite to the transparent film base material 11 side, a release liner (not shown) may be temporarily attached. The release liner protects the surface of the pressure-sensitive adhesive layer 21 until, for example, the antireflection film 20 is bonded to the image display panel 101 (see FIG. 3) described later. As a constituent material of the release liner, a plastic film formed from acrylic, polyolefin, cyclic polyolefin, polyester, or the like is preferably used. The thickness of the release liner is, for example, 5 μm or more and 200 μm or less. It is preferable that the surface of the release liner is subjected to a release treatment. Examples of the material of the release agent used for the release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, fatty acid amide-based materials, and the like.

[0044] As described above, the configuration of the antireflection film according to the first embodiment has been described with reference to the drawings. However, the antireflection film according to the present invention is not limited to the above-described configuration.

[0045] For example, the antireflection film according to the present invention may have a dimensional change rate in the first direction before and after the heat resistance test of -0.10% or more and 0.10% or less, and a dimensional change rate in the first direction before and after the heat and humidity resistance test of 0.01% or more and 0.20% or less. In this case, an antireflection film excellent in bending resistance at high temperature and excellent in bending resistance at high temperature and high humidity can be obtained.

[0046] Further, the antireflection film according to the present invention may be an antireflection film that does not include a primer layer and an antifouling layer. Further, the antireflection film according to the present invention may include an optical functional layer different from the layers (transparent film base material, hard coat layer, primer layer, antireflection layer, and antifouling layer) included in the above-described configuration.

[0047] Next, the elements of the antireflection film (more specifically, the antireflection film ARF) according to the first embodiment will be described.

[0048] [Transparent Film Base Material] The transparent film substrate is, for example, a flexible transparent resin film. Examples of the material 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 the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of the cellulose resin include triacetyl cellulose (TAC). These materials may be used alone or in combination of two or more. From the viewpoints of transparency and strength, one kind selected from the group consisting of polyester resin, polyolefin resin, and cellulose resin is preferable as the material of the transparent film substrate, one kind selected from the group consisting of PET, COP, and TAC is more preferable, and PET is even more preferable. That is, as the transparent film substrate, one kind of film selected from the group consisting of polyester resin film, polyolefin resin film, and cellulose resin film is preferable, one kind of film selected from the group consisting of PET film, COP film, and TAC film is more preferable, and PET film is even more preferable.

[0049] 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, more preferably 200 μm or less.

[0050] One main surface or both main surfaces of the transparent film substrate may be surface-modified. Examples of the surface modification treatment include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

[0051] The total light transmittance (JIS K 7375-2008) of the transparent film substrate is preferably 80% or more, more preferably 90% or more, still more preferably 95% or more and 100% or less from the viewpoint of improving the transparency of the antireflection film.

[0052] [Hard coat layer] The hard coat layer is a layer that enhances mechanical properties such as the hardness and elastic modulus of the antireflection film. The hard coat layer is composed of, for example, a cured product of a curable resin composition (composition for forming the hard coat layer). Examples of the curable resin contained in the curable resin composition include polyester resin, acrylic resin, urethane resin, acrylic urethane resin, amide resin, silicone resin, epoxy resin, and melamine resin. These curable resins may be used alone or in combination of two or more. From the viewpoint of enhancing the hardness of the hard coat layer, the curable resin is preferably at least one selected from the group consisting of acrylic resin and acrylic urethane resin, and more preferably acrylic resin.

[0053] 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 antireflection film, the curable resin composition is preferably an ultraviolet-curable resin composition. The ultraviolet-curable resin composition contains at least one selected from the group consisting of an ultraviolet-curable monomer, an ultraviolet-curable oligomer, and an ultraviolet-curable polymer. Specific examples of the ultraviolet-curable resin composition include the composition for forming a hard coat layer described in JP-A-2016-179686.

[0054] Further, the curable resin composition may contain fine particles. By blending fine particles into the curable resin composition, it becomes possible to adjust the hardness, surface roughness, refractive index, and antiglare property in the hard coat layer. Examples of the fine particles include metal oxide particles, glass particles, and organic particles. Examples of the material of the metal oxide particles include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Examples of the material of the organic particles include polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate.

[0055] From the viewpoint of increasing the hardness of the hard coat layer, the thickness of the hard coat layer is preferably 1 μm or more, more preferably 2 μm or more. From the viewpoint of ensuring the flexibility of the antireflection film, the thickness of the hard coat layer is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and even more preferably 30 μm or less.

[0056] The main surface of the hard coat layer on the side opposite to the transparent film base material side may be surface-modified. Examples of the surface modification treatment include plasma treatment, corona treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment. In order to enhance the adhesion between the layer provided on the side opposite to the transparent film base material side of the hard coat layer (for example, the primer layer described later) and the hard coat layer, the main surface of the hard coat layer on the side opposite to the transparent film base material side is preferably plasma-treated.

[0057] [Primer layer] In order to enhance the adhesion between the hard coat layer and the antireflection layer, it is preferable to provide a primer layer between the hard coat layer and the antireflection layer. Examples of the material for the primer layer include metals (or metalloids) such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, indium, tungsten, aluminum, zirconium, palladium, etc.; alloys of these metals (or metalloids); oxides, fluorides, sulfides, nitrides, etc. of these metals (or metalloids). The oxide constituting the primer layer may be a composite oxide such as indium tin oxide (ITO). Among them, inorganic oxides are preferable as the material for the primer layer, and silicon oxide, indium oxide, or ITO is particularly preferable.

[0058] In order to ensure the light transmittance of the primer layer while enhancing the adhesion between the hard coat layer and the antireflection 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.

[0059] [Antireflection layer] The antireflection layer is composed of two or more thin films with different refractive indices. Generally, the optical film thickness (the product of the refractive index and the thickness) of the thin film is adjusted so that the phases of the incident light and the reflected light that are reversed cancel each other out. By forming the antireflection layer as a multilayer laminate of two or more thin films with different refractive indices, the reflectance can be reduced in a wide wavelength range of visible light.

[0060] Examples of the material for the thin film constituting the antireflection layer include oxides, nitrides, fluorides, etc. of metals (or metalloids). The antireflection layer is preferably an alternating laminate of a high refractive index layer and a low refractive index layer.

[0061] The high refractive index layer has a refractive index of, for example, 1.9 or more, preferably 2.0 or more. Examples of the material for the high refractive index layer include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, ITO, antimony-doped tin oxide (ATO), and the like. Among them, one or more selected from the group consisting of titanium oxide and niobium oxide are preferable. The low refractive index layer has a refractive index of, for example, 1.6 or less, preferably 1.5 or less. Examples of the material for the low refractive index layer include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, lanthanum fluoride, and the like. Among them, silicon oxide is preferable. In particular, it is preferable to alternately stack a niobium oxide (Nb 2 O 5 ) thin film as the high refractive index layer and a silicon oxide (SiO 2 ) thin film as the low refractive index layer. In addition to the low refractive index layer and the high refractive index layer, an intermediate refractive index layer with a refractive index greater than 1.6 and less than 1.9 may be provided.

[0062] The film thicknesses of the high refractive index layer and the low refractive index layer are each preferably 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. Depending on the refractive index, the stacking structure, etc., the film thickness of each layer may be designed so that the reflectance of visible light is reduced. For example, as the stacking structure of the high refractive index layer and the low refractive index layer, from the hard coat layer side, there is a four-layer structure composed of a high refractive index layer with an optical film thickness of 20 nm or more and 55 nm or less, a low refractive index layer with an optical film thickness of 35 nm or more and 55 nm or less, a high refractive index layer with an optical film thickness of 80 nm or more and 250 nm or less, and a low refractive index layer with an optical film thickness of 100 nm or more and 150 nm or less.

[0063] The antireflection layer is a niobium oxide (Nb 2 O 5 ) thin film as the high refractive index layer and a silicon oxide (SiO 2)In the case of a four-layer alternating laminate in which a film is alternately laminated, as the configuration of the antireflection layer, from the hard coat layer side, a niobium oxide thin film with a thickness of 5 nm or more and 20 nm or less, a silicon oxide thin film with a thickness of 20 nm or more and 40 nm or less, a niobium oxide thin film with a thickness of 65 nm or more and 120 nm or less, and a silicon oxide thin film with a thickness of 60 nm or more and 100 nm or less are provided in this order.

[0064] In order to obtain an antireflection film with excellent flex resistance in a harsh environment, the thickness of the antireflection layer is preferably 150 nm or more and 280 nm or less, more preferably 180 nm or more and 280 nm or less, still more preferably 190 nm or more and 260 nm or less, and even more preferably 200 nm or more and 250 nm or less. In this specification, the "thickness of the antireflection layer" is the total thickness (total thickness) of each layer constituting the antireflection layer.

[0065] [Antifouling layer] The antireflection film preferably has an antifouling layer on the side opposite to the hard coat layer side of the antireflection layer, and more preferably has an antifouling layer as the outermost layer of the antireflection film. By providing the antifouling layer, for example, the influence of contamination from the external environment (fingerprints, dirt, dust, etc.) can be reduced, and it becomes easy to remove the contaminants adhering to the surface of the antireflection film.

[0066] In order to suppress the deterioration of the antireflection performance of the antireflection layer, it is preferable that the refractive index difference between the antifouling layer and the outermost layer (for example, the low refractive index layer) of the antireflection layer is small. The refractive index of the antifouling layer is preferably 1.6 or less, and more preferably 1.55 or less.

[0067] As the material of the antifouling layer, a fluorine-containing compound is preferred. The fluorine-containing compound is excellent in antifouling property and can contribute to reducing the refractive index. Among them, an alkoxysilane compound containing a perfluoropolyether skeleton is preferred because it has excellent water repellency and can exhibit high antifouling property. Examples of the alkoxysilane compound containing a perfluoropolyether skeleton include alkoxysilane compounds having a plurality of linear or branched perfluoroalkylene oxide units having 1 to 4 carbon atoms. Examples of the linear or branched perfluoroalkylene oxide unit having 1 to 4 carbon atoms include 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.

[0068] The thickness of the antifouling layer is, for example, 2 nm or more and 50 nm or less. Generally, the greater the thickness of the antifouling layer, the more likely the antifouling property is to improve. The thickness of the antifouling layer is preferably 5 nm or more, more preferably 7 nm or more, and still more preferably 8 nm or more. On the other hand, from the viewpoint of enhancing the antiglare property, the thickness of the antifouling layer is preferably 30 nm or less, and more preferably 20 nm or less.

[0069] [Preferred embodiments of the antireflection film] In order to obtain an antireflection film that is particularly excellent in flexural resistance at high temperatures, the antireflection film according to the first embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, still more preferably satisfies the following condition 3, and still more preferably satisfies the following condition 4. Condition 1: At least one of the dimensional change rates in the first direction and the second direction before and after the heat resistance test is 0.00% or more and 0.04% or less. Condition 2: Satisfy the above Condition 1, and the thickness of the antireflection layer is 150 nm or more and 280 nm or less. Condition 3: The dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0.04% or less, and the dimensional change rate in the second direction before and after the heat resistance test is -0.07% or more and 0.00% or less. Condition 4: Satisfy the above Condition 3, and the thickness of the antireflection layer is 150 nm or more and 280 nm or less.

[0070] In addition, in order to obtain an antireflection film that is particularly excellent in flex resistance under high temperature and high humidity, the antireflection film according to the first embodiment preferably satisfies the following Condition i, more preferably satisfies the following Condition ii, still more preferably satisfies the following Condition iii, and even more preferably satisfies the following Condition iv. Condition i: The dimensional change rates in the first direction and the second direction before and after the damp heat resistance test are both 0.05% or more and 0.13% or less. Condition ii: Satisfy the above Condition i, and the thickness of the antireflection layer is 150 nm or more and 280 nm or less. Condition iii: The dimensional change rate in the first direction before and after the damp heat resistance test is 0.05% or more and 0.11% or less, and the dimensional change rate in the second direction before and after the damp heat resistance test is 0.10% or more and 0.13% or less. Condition iv: Satisfy the above Condition iii, and the thickness of the antireflection layer is 150 nm or more and 280 nm or less.

[0071] In addition, in order to obtain an antireflection film that is particularly excellent in flex resistance at high temperature and particularly excellent in flex resistance under high temperature and high humidity, the antireflection film according to the first embodiment preferably satisfies the above Conditions 1 and i, more preferably satisfies the above Conditions 2 and ii, still more preferably satisfies the above Conditions 3 and iii, and even more preferably satisfies the above Conditions 4 and iv.

[0072] <Second Embodiment: Image Display Device> Next, an image display device according to the second embodiment of the present invention will be described. The image display device according to the second embodiment includes an image display panel and an antireflection film according to the first embodiment disposed on the viewing side of the image display panel. Hereinafter, descriptions of the contents overlapping with the first embodiment will be omitted.

[0073] 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 antireflection film 10, which is an example of the antireflection film according to the first embodiment, disposed on the viewing side (the upper side in FIG. 3) of the image display panel 101. In the image display device 100, the transparent film base material 11 of the antireflection film 10 and the image display panel 101 are bonded via an adhesive layer 21.

[0074] Examples of the image display panel 101 include an image display panel including an image display cell such as a liquid crystal cell or an organic EL cell.

[0075] In the image display device according to the second embodiment, since the antireflection film is disposed on the viewing side of the image display panel, reflection of external light is reduced and the visibility is excellent. Further, since the image display device according to the second embodiment includes the antireflection film according to the first embodiment (an antireflection film excellent in flexural resistance in a harsh environment), even when stored in a state where the side where the antireflection layer is formed is bent inward, cracks in the antireflection layer at the bent portion are unlikely to occur. Therefore, the image display device according to the second embodiment can also be used, for example, as a foldable display. In order to obtain a foldable display that can further suppress the occurrence of cracks in the antireflection layer in a harsh environment, it is preferable that the bent portion of the foldable display is a bent portion where the antireflection film can be bent in a first direction.

[0076] <Third Embodiment: Manufacturing Method of Antireflection Film> Next, a method for manufacturing an antireflection film according to the third embodiment of the present invention will be described. The method for manufacturing an antireflection film according to the third embodiment is a preferred method for manufacturing the antireflection film according to the first embodiment. Hereinafter, descriptions of the contents overlapping with the first embodiment will be omitted.

[0077] The method for manufacturing an antireflection film according to the third embodiment includes a step Sa of forming an antireflection layer on the side opposite to the transparent film base material side of the hard coat layer by a roll-to-roll sputtering film forming apparatus, and a step Sb of heating the laminate on which the antireflection layer is formed after the step Sa. Since the method for manufacturing an antireflection film according to the third embodiment includes the step Sa and the step Sb, the antireflection film according to the first embodiment can be easily manufactured. Hereinafter, the step Sa will be described as the "antireflection layer forming step". Also, the step Sb will be described as the "antireflection layer heating step".

[0078] The method for manufacturing an antireflection film according to the third embodiment may include steps other than the antireflection layer forming step and the antireflection layer heating step (other steps). Examples of the other steps include a hard coat layer forming step, a surface treatment step of the hard coat layer, a hard coat layer heating step, a primer layer forming step, and an antifouling layer forming step, which will be described later.

[0079] Hereinafter, each step included in an example of the method for manufacturing an antireflection film according to the third embodiment will be described.

[0080] [Hard Coat Layer Forming Step] The hard coat layer forming step is a step of forming a hard coat layer on a transparent film base material. For example, a curable resin composition (composition for forming a hard coat layer) is applied onto the transparent film base material, and the solvent is removed and the resin is cured as necessary, thereby forming a hard coat layer. The composition for forming a hard coat layer contains, for example, the above-described curable resin and a polymerization initiator (for example, a photoinitiator), and optionally contains a solvent capable of dissolving or dispersing these components.

[0081] In addition to the above components, the composition for forming a hard coat layer may contain additives such as fine particles, leveling agents, viscosity modifiers (thixotropic agents, thickeners, etc.), antistatic agents, antiblocking agents, dispersants, dispersion stabilizers, antioxidants, ultraviolet absorbers, defoaming agents, surfactants, and lubricants.

[0082] As a coating method for the composition for forming a hard coat layer, any appropriate 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, or a comma coating method can be adopted. The drying temperature of the coating film after coating may be set to an appropriate temperature according to the composition of the composition for forming a hard coat layer, etc. For example, it is 50°C or higher and 150°C or lower. 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 active energy rays such as ultraviolet rays. The integrated light amount of the irradiated light is preferably 100 mJ / cm 2 or more and 500 mJ / cm 2 or less.

[0083] [Surface treatment step of hard coat layer] In the surface treatment step of the hard coat layer, the main surface on the side opposite to the transparent film substrate side of the hard coat layer 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. Also, the discharge power in the plasma treatment is, for example, 10 W or more and 10000 W or less.

[0084] [Hard coat layer heating step] The hard coat layer heating step is a step of heating a laminate including a hard coat layer (for example, a film-like laminate having a transparent film substrate and a hard coat layer) before providing another layer (for example, a primer layer, an antireflection layer, etc.) on the hard coat layer. By providing the hard coat layer heating step, for example, dimensional changes of the antireflection film due to thermal shrinkage of the transparent film substrate can be suppressed.

[0085] In the third embodiment, since a roll-to-roll type sputtering film forming apparatus is used in the antireflection layer forming step, from the viewpoint of enhancing productivity, in the hard coat layer heating step, it is preferable to heat the laminate while conveying it in a roll-to-roll manner. Examples of the heating device for heating include a hot air oven, an infrared heater, and the like.

[0086] The heating temperature of the laminate in the hard coat layer heating step is, for example, 100°C or higher and 200°C or lower. The heating time of the laminate in the hard coat layer heating step is, for example, 30 seconds or longer and 30 minutes or shorter. In addition, when providing the surface treatment step of the hard coat layer and the hard coat layer heating step, the hard coat layer heating step may be carried out before or after the surface treatment step of the hard coat layer.

[0087] [Primer layer forming step] The primer layer forming step is a step of forming (film-forming) a primer layer on the hard coat layer. The film-forming method of the primer layer is not particularly limited, and either a wet coating method or a dry coating method may be used. Since a thin film with a uniform film thickness can be formed, dry coating methods such as vacuum evaporation, CVD, and sputtering are preferable. Also, in the third embodiment, since a roll-to-roll type sputtering film forming apparatus is used in the antireflection layer forming step, from the viewpoint of enhancing productivity, as the film-forming method of the primer layer, a method of film-forming using a roll-to-roll type sputtering film forming apparatus (roll-to-roll type sputtering method) is preferable.

[0088] In the roll-to-roll sputtering method, while a long film (for example, a transparent film substrate with a hard coat layer formed thereon) is being conveyed in the longitudinal direction (MD direction), for example, a primer layer and an antireflection layer can be continuously formed. In the sputtering method, film formation is carried out 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 oxide layer as the primer layer, the film formation of the oxide layer by the sputtering method can be carried out by either a method using an oxide target or reactive sputtering using a metal (or metalloid) target.

[0089] Examples of the power source for carrying out the sputtering method include a DC power source, an AC power source, an RF power source, and an MFAC power source (an AC power source with a frequency band of several kHz to several MHz). The discharge power in the sputtering method is, for example, 1 kW or more and 100 kW or less, preferably 1 kW or more and 50 kW or less. The surface temperature of the film formation roll when carrying out the sputtering method is, for example, -25°C or more and 25°C or less, preferably -20°C or more and 0°C or less. The pressure in the film formation chamber when carrying out the sputtering method is preferably 0.01 Pa or more and 10 Pa or less, more preferably 0.05 Pa or more and 5 Pa or less, and even more preferably 0.1 Pa or more and 1 Pa or less.

[0090] [Antireflection Layer Formation Step] In the antireflection layer formation step, an antireflection layer is formed on the side opposite to the transparent film substrate side of the hard coat layer (for example, the surface of the hard coat layer or the surface of the primer layer) by a roll-to-roll sputtering film formation apparatus. That is, in the third embodiment, each layer of the antireflection layer is formed by the roll-to-roll sputtering method. When carrying out the sputtering method in the antireflection layer formation step, for example, the film formation conditions can be appropriately set among the conditions described in the above [Primer Layer Formation Step].

[0091] When each layer of the antireflection layer is formed by a roll-to-roll sputtering method, it has been found by the inventors' study that the antireflection film is likely to shrink under harsh environments. In particular, when a stretched film such as a PET film is used as the transparent film substrate, the shrinkage of the antireflection film becomes remarkable. When a laminate for forming the antireflection layer (for example, a film-like laminate having at least a transparent film substrate and a hard coat layer) is conveyed by a roll-to-roll method, a tension is applied to the laminate in the conveying direction. Therefore, residual stress is generated in the laminate, and it is presumed that the antireflection film is likely to shrink under harsh environments.

[0092] [Antifouling layer forming step] The antifouling layer forming step is a step of forming an antifouling layer on the side opposite to the hard coat layer side of the antireflection layer. In the antifouling layer forming step, for example, a fluorine-containing compound is used as a material, and the antifouling layer is formed by a dry coating method. Examples of the dry coating method include a vacuum evaporation method, a sputtering method, and a CVD method, and the vacuum evaporation method is preferable.

[0093] [Antireflection layer heating step] The antireflection layer heating step is a step of heating a laminate on which the antireflection layer is formed (hereinafter, may be referred to as an "antireflection layer-attached film"). By heating the antireflection layer-attached film, for example, at least a part of the residual stress of the antireflection layer-attached film is removed, and the shrinkage of the antireflection film under harsh environments is suppressed. As a result, an antireflection film excellent in bending resistance under harsh environments can be obtained. When the antifouling layer forming step is provided, the antireflection layer heating step may be carried out before or after the antifouling layer forming step. When the antifouling layer forming step is provided, in order to obtain an antireflection film having more excellent bending resistance under harsh environments, it is preferable that the antireflection layer heating step is carried out after the antifouling layer forming step.

[0094] In the third embodiment, since a roll-to-roll sputtering film forming apparatus is used in the antireflection layer forming step, from the viewpoint of improving productivity, in the antireflection layer heating step, it is preferable to heat while conveying the film with the antireflection layer in a roll-to-roll manner. Examples of the heating device for heating include a hot air oven, an infrared heater, and the like.

[0095] In order to obtain an antireflection film having excellent flexural resistance in a harsh environment, the heating temperature of the film with the antireflection layer in the antireflection layer heating step is preferably 110 ° C or higher, more preferably 115 ° C or higher, still more preferably 120 ° C or higher, and may be 130 ° C or higher, 140 ° C or higher, 150 ° C or higher, 160 ° C or higher, 170 ° C or higher, or 180 ° C or higher. Further, in order to obtain an antireflection film having excellent flexural resistance in a harsh environment, the heating time of the film with the antireflection layer in the antireflection layer heating step is preferably 30 seconds or longer, more preferably 1 minute or longer, still more preferably 2 minutes or longer, and may be 5 minutes or longer, 10 minutes or longer, or 15 minutes or longer.

[0096] In order to suppress a decrease in the transparency of the antireflection film, the heating temperature of the film with the antireflection layer in the antireflection layer heating step is preferably 200 ° C or lower, more preferably 190 ° C or lower. Further, in order to suppress a decrease in the transparency of the antireflection film, the heating time of the film with the antireflection layer in the antireflection layer heating step is preferably 30 minutes or shorter, more preferably 20 minutes or shorter.

[0097] The dimensional change rates in the first direction and the second direction before and after the heat resistance test, and the dimensional change rates in the first direction and the second direction before and after the damp heat resistance test can all be adjusted by changing the heating conditions (specifically, heating temperature, heating time, etc.) in the antireflection layer heating step.

Examples

[0098] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0099] <Fabrication of the Antireflection Film of Example 1> [Hard Coat Layer Formation Step] 100 parts by weight of an ultraviolet-curable polyfunctional acrylic resin composition (「Z-850-50H-D」manufactured by Aica Kogyo Co., Ltd., solid content concentration: 44% by weight) in terms of solid content, 4 parts by weight of a photoinitiator (「Omnirad2959」manufactured by IGM Resins), and 0.05 parts by weight of a leveling agent (「LE-303」manufactured by Kyoeisha Chemical Co., Ltd.) were mixed to obtain a mixed solution. Next, methyl isobutyl ketone was added to the obtained mixed solution to obtain a composition for forming a hard coat layer with a solid content concentration of 40% by weight. Next, the composition for forming a hard coat layer was applied to one main surface of a PET film (「50U48」manufactured by Toray Industries, Inc., thickness: 50 μm) as a transparent film substrate to form a coating film. Next, this coating film was dried by heating at 80 °C for 60 seconds and then cured by ultraviolet irradiation. When performing ultraviolet irradiation, a high-pressure mercury lamp was used as a light source, ultraviolet rays with a wavelength of 365 nm were used, and the integrated light quantity was 300 mJ / cm 2 was used. Thereby, a hard coat layer with a thickness of 3 μm was formed on the PET film.

[0100] [Surface Treatment Step of the Hard Coat Layer] Next, while transporting the PET film on which the hard coat layer was formed in a vacuum atmosphere of 1.0 Pa by a roll-to-roll type plasma treatment apparatus, the surface of the hard coat layer was plasma-treated. When performing plasma treatment, argon gas was used as an inert gas, and the discharge power was set to 150 W. Thereby, a laminate (hereinafter, sometimes referred to as "optical film F1") including the PET film and the plasma-treated hard coat layer was obtained.

[0101] [Hard Coat Layer Heating Step] Next, while transporting the optical film F1 by a roll-to-roll type transport apparatus, it was heated at 140 °C for 2 minutes using a hot air oven.

[0102] [Primer Layer Formation Step] Next, the heated optical film F1 was introduced into a roll-to-roll sputtering film forming apparatus, and the pressure in the film forming chamber was reduced to 1×10 -4 Pa. Next, while transporting the optical film F1, argon gas and oxygen gas were introduced at a volume ratio of 100:10, the surface temperature of the film forming roll was set to -8°C, and an ITO layer (primer layer) with a thickness of 1.5 nm was formed on the hard coat layer by sputtering. For the formation of the primer layer, an ITO target containing indium oxide and tin oxide at a weight ratio of 90:10 was used as the target material. Also, when forming the film by sputtering, an MFAC power supply was used, the discharge power was set to 2.5 kW, and the pressure in the film forming chamber was set to 0.2 Pa.

[0103] [Anti-reflection layer formation step] Following the formation of the primer layer, while transporting the optical film F1 after primer layer formation using a roll-to-roll sputtering film forming apparatus, by sputtering, on the primer layer, the first layer: a Nb layer with a thickness of 12 nm 2 O 5 layer (refractive index: 2.33), the second layer: a SiO layer with a thickness of 28 nm 2 layer (refractive index: 1.46), the third layer: a Nb layer with a thickness of 100 nm 2 O 5 layer, and the fourth layer: a SiO layer with a thickness of 85 nm 2 layer were formed in this order. Thereby, an anti-reflection layer having a four-layer structure (a four-layer structure composed of the first layer, the second layer, the third layer, and the fourth layer) was formed on the primer layer. In the film formation of each of the first layer to the fourth layer, in each case, the surface temperature of the film forming roll was set to -8°C, the power supply was an MFAC power supply, and the pressure in the film forming chamber was set to 0.7 Pa. Also, in the film formation of the first layer, a Nb target was used, argon gas and oxygen gas were introduced at a volume ratio of 100:5, and the discharge power was set to 10.5 kW. In the film formation of the second layer, a Si target was used, argon gas and oxygen gas were introduced at a volume ratio of 100:30, and the discharge power was set to 14 kW. In the film formation of the third layer, a Nb target was used, argon gas and oxygen gas were introduced at a volume ratio of 100:13, and the discharge power was set to 22 kW. In the film formation of the fourth layer, a Si target was used, argon gas and oxygen gas were introduced at a volume ratio of 100:30, and the discharge power was set to 12 kW.

[0104] [Antifouling layer formation process] A coating agent (manufactured by Shin-Etsu Chemical Co., Ltd., "SHIN-ETSU SUBELYN KY1903-1", active ingredient: an alkoxysilane compound containing a perfluoropolyether backbone) that has been dried and solidified is used as a vapor deposition source. The heating temperature of the vapor deposition source is set to 260 °C, and an antifouling layer with a thickness of 12 nm is formed on the antireflection layer by physical vapor deposition. As a result, a laminate comprising a PET film, a hard coat layer, a primer layer, an antireflection layer, and an antifouling layer (hereinafter sometimes referred to as "optical film F2") was obtained.

[0105] [Antireflection layer heating process] Next, while transporting the optical film F2 by a roll-to-roll type transport device, it was heated at 120 °C for 2 minutes using a hot air oven. As a result, the antireflection film of Example 1 was obtained.

[0106] [Production of antireflection films of Examples 2 to 9 and Comparative Examples 1 to 5] The antireflection films of Examples 2 to 9 and Comparative Examples 1 to 5 were obtained by the same production method as in Example 1, except that the heating conditions of the optical film F1 in the hard coat layer heating process and the heating conditions of the optical film F2 in the antireflection layer heating process were changed to the conditions shown in Table 1. In the production of the antireflection films of Examples 6 to 9 and Comparative Example 4, the hard coat layer heating process was not performed. Also, in the production of the antireflection films of Comparative Examples 4 and 5, the antireflection layer heating process was not performed.

[0107]

Table 1

[0108] [Measurement method of dimensional change rate] [Measurement method of dimensional change rate before and after heat resistance test] As test pieces for measuring the dimensional change rate before and after the heat resistance test, test pieces with a size of 100 mm × 100 mm (length in the MD direction: 100 mm, length in the TD direction: 100 mm) were cut out from each anti-reflection film using a laser processing machine ("LaserPro Spirit GLS" manufactured by GCC). The ambient temperature and relative humidity when cutting out the test pieces were 20°C and 50% respectively. Next, after conducting a heat resistance test in which each test piece was left standing in a drying oven ("PH-202" manufactured by Espec) at a temperature of 85°C and a relative humidity of 1% or less for 48 hours, it was left standing in an atmosphere at a temperature of 20°C and a relative humidity of 50% for 24 hours, and the dimensional change rate before and after the heat resistance test was determined. That is, the dimensional change rate in each direction (MD direction and TD direction) of each test piece was calculated from the length L1 (100 mm) in each direction at a temperature of 20°C and a relative humidity of 50% before the heat resistance test and the length L2 in each direction measured after leaving it standing in an atmosphere at a temperature of 20°C and a relative humidity of 50% for 24 hours after the heat resistance test, using the formula described above.

[0109] [Method for Measuring Dimensional Change Rate Before and After Damp Heat Resistance Test] As test pieces for measuring the dimensional change rate before and after the damp heat resistance test, test pieces with a size of 100 mm × 100 mm (length in the MD direction: 100 mm, length in the TD direction: 100 mm) were cut out from each anti-reflection film using a laser processing machine ("LaserPro Spirit GLS" manufactured by GCC). The ambient temperature and relative humidity when cutting out the test pieces were 20°C and 50% respectively. Next, after conducting a damp heat resistance test in which each test piece was left standing in a thermo-hygrostat ("PL-2J" manufactured by Espec) at a temperature of 60°C and a relative humidity of 95% for 48 hours, it was left standing in an atmosphere at a temperature of 20°C and a relative humidity of 50% for 24 hours, and the dimensional change rate before and after the damp heat resistance test was determined. That is, the dimensional change rate in each direction (MD direction and TD direction) of each test piece was calculated from the length L1 (100 mm) in each direction at a temperature of 20°C and a relative humidity of 50% before the damp heat resistance test and the length L2 in each direction measured after leaving it standing in an atmosphere at a temperature of 20°C and a relative humidity of 50% for 24 hours after the damp heat resistance test, using the formula described above.

[0110] <Flexural Resistance Evaluation> [Flexural Resistance Evaluation at High Temperatures] As test specimens for evaluating the flexural resistance at high temperatures, 200 test specimens with a size of 10 mm in width × 100 mm in length (length direction: MD direction, width direction: TD direction) were cut out from each antireflection film using a laser processing machine ("LaserPro Spirit GLS" manufactured by GCC). Next, as shown in Fig. 4, with the surface on the antireflection layer (not shown) side of the test specimen 200 facing inward, both ends in the MD direction were bonded to spacers 300 with a thickness D (D: 4.0 mm or 3.8 mm) in a state of being bent in the MD direction (X direction in Fig. 4). In the state of Fig. 4, the bending radius of the bent portion of the test specimen 200 was D / 2. Then, the test specimen 200 in the state of Fig. 4 was taken out after being left standing in a drying oven ("PH-202" manufactured by Espec) at a temperature of 85°C and a relative humidity of 1% or less for 48 hours, and the presence or absence of cracks (cloudiness of the antireflection layer) in the bent portion was confirmed with an optical microscope. And when no cracks were confirmed, it was judged as A. On the other hand, when cracks were confirmed, it was judged as B. When the judgment result was A when using the spacer with a thickness of 4.0 mm, it was evaluated as "excellent in flexural resistance at high temperatures", and when the judgment result was B when using the spacer with a thickness of 4.0 mm, it was evaluated as "not excellent in flexural resistance at high temperatures".

[0111] [Flexural Resistance Evaluation at High Temperature and High Humidity] As test pieces for evaluating the flex resistance under high temperature and high humidity, 200 test pieces with a size of 10 mm in width × 100 mm in length (length direction: MD direction, width direction: TD direction) were cut out from each antireflection film using a laser processing machine ("LaserPro Spirit GLS" manufactured by GCC). Next, as shown in Fig. 4, with the surface on the antireflection layer (not shown) side of the test piece 200 facing inward, both ends in the MD direction were bonded to spacers 300 with a thickness D (D: 4.0 mm or 3.8 mm) in a state of being bent in the MD direction (X direction in Fig. 4). In the state of Fig. 4, the bending radius of the bent portion of the test piece 200 was D / 2. Next, the test piece 200 in the state of Fig. 4 was taken out after being left stationary in a thermo-hygrostat ("PL-2J" manufactured by Espec) at a temperature of 60°C and a relative humidity of 95% for 48 hours, and the presence or absence of cracks (cloudiness of the antireflection layer) in the bent portion was confirmed with an optical microscope. And when no crack was confirmed, it was judged as A. On the other hand, when a crack was confirmed, it was judged as B. When the judgment result was A when using a spacer with a thickness of 4.0 mm, it was evaluated as "excellent in flex resistance under high temperature and high humidity", and when the judgment result was B when using a spacer with a thickness of 4.0 mm, it was evaluated as "not excellent in flex resistance under high temperature and high humidity".

[0112] <Evaluation Results> For Examples 1 to 9 and Comparative Examples 1 to 5, the dimensional change rates before and after the heat resistance test, the dimensional change rates before and after the damp heat resistance test, and the judgment results of the flex resistance are shown in Table 2. In Table 2, "4.0 mm" and "3.8 mm" both mean the thickness of the spacers used in the flex resistance evaluation.

[0113]

Table 2

[0114] As shown in Table 2, in Examples 1 to 9, the dimensional change rate in the MD direction before and after the heat resistance test was -0.10% or more and 0.10% or less. In Examples 1 to 9, the dimensional change rate in the MD direction before and after the damp heat resistance test was 0.01% or more and 0.20% or less.

[0115] As shown in Table 2, in Examples 1 to 9, the determination results of the bending resistance at high temperatures when using a spacer with a thickness of 4.0 mm were A. Therefore, the antireflection films of Examples 1 to 9 were excellent in bending resistance at high temperatures. In Examples 1 to 9, the determination results of the bending resistance under high temperature and high humidity when using a spacer with a thickness of 4.0 mm were A. Therefore, the antireflection films of Examples 1 to 9 were excellent in bending resistance under high temperature and high humidity.

[0116] As shown in Table 2, in Comparative Examples 1 to 5, the dimensional change rates before and after the heat resistance test were less than -0.10% in both the TD direction and the MD direction. In Comparative Examples 1 to 5, the dimensional change rates before and after the damp heat resistance test were less than 0.01% in both the TD direction and the MD direction.

[0117] As shown in Table 2, in Comparative Examples 1 to 5, the determination results of the bending resistance at high temperatures when using a spacer with a thickness of 4.0 mm were B. Therefore, the antireflection films of Comparative Examples 1 to 5 were not excellent in bending resistance at high temperatures. In Comparative Examples 1 to 5, the determination results of the bending resistance under high temperature and high humidity when using a spacer with a thickness of 4.0 mm were B. Therefore, the antireflection films of Comparative Examples 1 to 5 were not excellent in bending resistance under high temperature and high humidity.

[0118] From the above results, it was shown that according to the present invention, an antireflection film excellent in bending resistance under harsh environments can be provided.

Explanation of Signs

[0119] 10, 20 Antireflection film 11 Transparent film substrate 12 Hard coat layer 13 Antireflection layer 18 Primer layer 19 Antifouling layer 21 Adhesive layer 100 Image display device 101 Image display panel

Claims

1. An antireflection film having a transparent film substrate, a hard coat layer, a primer layer, and an antireflection layer in this order, When a heat resistance test is performed in which the sample is held in an environment at a temperature of 85° C. for 48 hours, the dimensional change rate in the direction of any one of the sides before and after the heat resistance test is −0.10% or more and 0.10% or less, the antireflection layer is an alternating laminate of a niobium oxide thin film and a silicon oxide thin film, The antireflection film, wherein the antireflection layer has a thickness of 150 nm or more and 260 nm or less.

2. 2. The anti-reflection film according to claim 1, wherein a dimensional change rate in a direction perpendicular to the direction of the side before and after the heat resistance test is −0.10% or more and 0.10% or less.

3. An antireflection film having a transparent film substrate, a hard coat layer, a primer layer, and an antireflection layer in this order, When a moisture and heat resistance test is performed in an environment of a temperature of 60° C. and a relative humidity of 95% for 48 hours, the dimensional change rate in the direction of any one of the sides before and after the moisture and heat resistance test is 0.01% or more and 0.20% or less, the antireflection layer is an alternating laminate of a niobium oxide thin film and a silicon oxide thin film, The antireflection film, wherein the antireflection layer has a thickness of 150 nm or more and 260 nm or less.

4. The antireflection film according to claim 3 , wherein a dimensional change rate in a direction perpendicular to the direction of the sides before and after the moist heat resistance test is 0.01% or more and 0.20% or less.

5. The anti-reflection film according to claim 1 or 3, wherein the transparent film substrate is a polyethylene terephthalate film.

6. The antireflection film according to claim 1 , further comprising an antifouling layer disposed on the antireflection layer opposite to the hard coat layer side.

7. The anti-reflection film according to claim 1 , further comprising a pressure-sensitive adhesive layer disposed on the opposite side of the transparent film substrate to the hard coat layer.

8. An image display device comprising: an image display panel; and the anti-reflection film according to claim 1 or 3, disposed on a viewing side of the image display panel.

9. A method for producing the anti-reflection film according to claim 1 or 3, a step Sa of forming the antireflection layer on the opposite side of the hard coat layer from the transparent film substrate by a roll-to-roll sputtering deposition apparatus; The method for producing an antireflection film includes, after the step Sa, a step Sb of heating the laminate on which the antireflection layer is formed.

10. The method for producing an antireflection film according to claim 9 , wherein in the step Sb, the laminate is heated at a temperature of 110° C. or higher.

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