Anti-reflective film, method for manufacturing the same, and image display device

Abstract

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%. The transparent film base material (11) is preferably a polyethylene terephthalate film.

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 deterioration of image quality 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 (Nb2O5) layer as a high refractive index layer and a silicon oxide (SiO2) layer as a low refractive index layer thereon.

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 provided with an antireflection layer on a flexible substrate is used.

[0006] Foldable displays are generally stored in a folded state. In the folded state, compressive stress is applied to the inside of the fold (bend) and tensile stress is applied to the outside of the bend. When the display is folded with the display surface facing inward, the anti-reflective film is folded (bent) with the surface forming the anti-reflective layer facing inward. Storing the display in a bent state at high temperatures or high temperature and humidity can cause microscopic cracks to develop in the anti-reflective layer, leading to a decrease in the display's visibility.

[0007] In view of the above, the present invention aims to provide an anti-reflective film that is less prone to cracking in the anti-reflective layer and has excellent flexibility even when stored in a bent state at high temperature or high temperature and humidity, a method for manufacturing the same, and an image display device using the anti-reflective film. [Means for solving the problem]

[0008] <Aspects of the Invention> The present invention includes the following embodiments.

[0009] [1] An anti-reflective film having a transparent film substrate, a hard coat layer and an anti-reflective layer in this order, An anti-reflective film in which, when subjected to a heat resistance test in an environment 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.

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

[0011] [3] An anti-reflective film having a transparent film substrate, a hard coat layer and an anti-reflective layer in this order, An anti-reflective film in which, when subjected to a heat and humidity resistance test held for 48 hours in an environment of 60°C and 95% relative humidity, the dimensional change rate in the direction of any one side before and after the heat and humidity resistance test is 0.01% or more and 0.20% or less.

[0012] [4] The anti-reflective film according to [3], wherein the dimensional change rate in the direction perpendicular to the direction of the edge before and after the humid heat resistance test is 0.01% or more and 0.20% or less.

[0013] [5] The anti-reflective film according to any one of [1] to [4], wherein the transparent film substrate is a polyethylene terephthalate film.

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

[0015] [7] The anti-reflective film according to any one of [1] to [6], further comprising a primer layer disposed between the hard coat layer and the anti-reflective layer.

[0016] [8] The anti-reflective film according to any one of [1] to [7], further comprising an anti-fouling layer disposed on the opposite side of the anti-reflective layer from the hard coat layer.

[0017] [9] The anti-reflective film according to any one of [1] to [8], further comprising an adhesive layer disposed on the opposite side of the transparent film substrate from the hard coat layer side.

[0018]

[10] An image display device comprising an image display panel and an anti-reflective film according to any one of [1] to [9] arranged on the viewing side of the image display panel.

[0019]

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

[0020]

[12] In the step Sb, the method for manufacturing an antireflection film according to

[11] , wherein 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 excellent in bending resistance and difficult to crack in the antireflection layer 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] It is a cross-sectional view showing an example of the antireflection film according to the present invention. [Figure 2] It is a cross-sectional view showing another example of the antireflection film according to the present invention. [Figure 3] It is a cross-sectional view showing an example of the image display device according to the present invention. [Figure 4] It is a cross-sectional view showing the bent state of a test piece when evaluating the bending resistance of the antireflection film.

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 surface 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" refers to the direction parallel to any one of the four sides of a rectangular or square anti-reflective film. Hereafter, the direction of any one side of the anti-reflective film may be referred to as the "first direction." The direction perpendicular to the first direction (more specifically, the direction parallel to the side perpendicular to the first direction among the four sides mentioned above) may be referred to as the "second direction." The first direction is, for example, the direction of film transport when forming the anti-reflective layer using the roll-to-roll sputtering method described later (hereinafter sometimes referred to as the "MD direction"). The second direction is, for example, the direction perpendicular to the direction of film transport when forming the anti-reflective layer using the roll-to-roll sputtering method described later (hereinafter sometimes referred to as the "TD direction").

[0025] Hereinafter, the compound name may be followed by "system" to refer to the compound and its derivatives collectively. Furthermore, when "system" is followed by a compound name to represent a polymer name, it means that the repeating units of the polymer originate from the compound or its derivative. Unless otherwise specified, the components and functional groups exemplified herein may be used individually or in combination of two or more.

[0026] The diagrams referenced in the following explanation are schematic representations of each component for ease of understanding, and the size, number, shape, etc., of each component shown may differ from the actual dimensions due to the limitations of drawing creation. Furthermore, for the sake of explanation, components identical to those described earlier may be denoted by the same reference numerals in later diagrams, and their explanations may be omitted.

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

[0028] Anti-reflective film ARF1 exhibits excellent flexibility, as shrinkage in the first direction is suppressed at high temperatures, making it less prone to cracking in the anti-reflective layer even when stored in a bent state at high temperatures. Similarly, anti-reflective film ARF2 exhibits excellent flexibility, as shrinkage in the first direction is suppressed at high temperatures and high humidity, making it less prone to cracking in the anti-reflective layer even when stored in a bent state at high temperatures and high humidity. In the following, unless otherwise necessary, anti-reflective film ARF1 and anti-reflective film ARF2 will be referred to simply as "anti-reflective film ARF." The property of being less prone to cracking in the anti-reflective layer even when stored in a bent state at high temperatures may be simply referred to as "flexibility at high temperatures."

[0029] Hereafter, high temperature or high temperature and high humidity conditions may be referred to as "harsh environment conditions." Furthermore, the property of the anti-reflective layer being resistant to cracking even when stored in a bent state under harsh environment conditions may simply be referred to as "harsh environment bending resistance." Also, a heat resistance test in which the anti-reflective film is held at 85°C for 48 hours may simply be referred to as a "heat resistance test." Furthermore, a humidity and heat resistance test in which the anti-reflective film is held at 60°C and 95% relative humidity for 48 hours may simply be referred to as a "humidity and heat resistance test." Additionally, a heat resistance test or humidity and heat resistance test may be referred to as a "harsh environment test." Hereafter, unless otherwise specified, "harsh environment test" refers to a test applied to anti-reflective film.

[0030] The relative humidity of the atmosphere used in the heat resistance test is, for example, 1% or less, but may also be 0.5% or less or 0.1% or less.

[0031] The dimensional change rate (in %) in the first or second direction before and after the harsh environment test is calculated according to the formula "Dimensional change rate = 100 × (L2 - L1) / L1", where L1 (in mm) is the length in the first or second direction before the harsh environment test and L2 (in mm) is the length in the first or second direction after the harsh environment test. If the dimensional change rate in the first or second direction is <0%, it means that the length in the first or second direction decreases due to the harsh environment test. On the other hand, if the dimensional change rate in the first or second direction is >0%, it means that the length in the first or second direction increases due to the harsh environment test. The method for measuring the dimensional change rate is the same as or similar to the method used in the examples described later.

[0032] To obtain an anti-reflective film ARF1 with superior bending resistance at high temperatures, it is preferable that the dimensional change rate in the second direction before and after the heat resistance test is between -0.10% and 0.10%.

[0033] To obtain an anti-reflective film ARF1 with superior bending resistance at high temperatures, it is preferable that the dimensional change rates in the first and second directions 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. Furthermore, to obtain an anti-reflective film ARF1 with superior bending resistance at high temperatures, it is preferable that the dimensional change rates in the first and second directions 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. To obtain an anti-reflective film ARF1 with even better bending resistance at high temperatures, it is preferable that at least one of the dimensional change rates in the first and second directions 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] To obtain an anti-reflective film ARF1 with particularly excellent bending 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, more preferably 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, and the dimensional change rate in the first direction before and after the heat resistance test is 0.00% or more and 0. It is more preferable that 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 it is even more preferable that 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, and 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 it is particularly preferable that 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. If the dimensional change rates in the first and second directions before and after the heat resistance test are within the above ranges, it is preferable to store the anti-reflective film ARF1 in a bent state in the first direction in order to further suppress the occurrence of cracks in the anti-reflective layer under high temperature and in a bent state.

[0035] To obtain an anti-reflective film ARF2 with superior bending resistance under high temperature and high humidity conditions, it is preferable that the dimensional change rate in the second direction before and after the humid heat resistance test is 0.01% or more and 0.20% or less.

[0036] To obtain an anti-reflective film ARF2 with superior bending resistance under high temperature and high humidity, it is preferable that the dimensional change rates in the first and second directions before and after the humidity and heat resistance test are both 0.02% or more, more preferably 0.03% or more, and may also 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. Furthermore, to obtain an anti-reflective film ARF2 with superior bending resistance under high temperature and high humidity, it is preferable that the dimensional change rates in the first and second directions before and after the humidity and heat resistance test are both 0.15% or less, more preferably 0.14% or less, and even more preferably 0.13% or less. To obtain an anti-reflective film ARF2 with even better bending resistance under high temperature and high humidity, it is preferable that the dimensional change rates in the first and second directions before and after the humidity and heat resistance test are both 0.05% or more and 0.13% or less, more preferably 0.06% or more and 0.13% or less, even 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] To obtain an anti-reflective film ARF2 that exhibits particularly excellent bending resistance under high temperature and high humidity, it is preferable that the dimensional change rate in the first direction before and after the humidity and heat resistance test is 0.05% to 0.11%, and the dimensional change rate in the second direction before and after the humidity and heat resistance test is 0.10% to 0.13%, more preferably that the dimensional change rate in the first direction before and after the humidity and heat resistance test is 0.06% to 0.11%, and the dimensional change rate in the second direction before and after the humidity and heat resistance test is 0.11% to 0.13%, and the dimensional change rate in the first direction before and after the humidity and heat resistance test is 0.07% or more. It is preferable that the dimensional change rate in the second direction before and after the humidity and heat resistance test is 0.11% or less, and more preferably that the dimensional change rate in the first direction before and after the humidity and heat resistance test is 0.08% or more and 0.11%, and more preferably that the dimensional change rate in the second direction before and after the humidity and heat resistance test is 0.11% or more and 0.13%, and particularly preferably that the dimensional change rate in the first direction before and after the humidity and heat resistance test is 0.09% or more and 0.11%, and the dimensional change rate in the second direction before and after the humidity and heat resistance test is 0.12% or more and 0.13%. If the dimensional change rates in the first and second directions before and after the humidity and heat resistance test are within the above ranges, it is preferable to store the anti-reflective film ARF2 in a bent state in the first direction in order to further suppress the occurrence of cracks in the anti-reflective layer under high temperature and high humidity conditions.

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

[0039] Furthermore, the anti-reflective film 10 includes a primer layer 18 positioned between the hard coat layer 12 and the anti-reflective layer 13, and an anti-fouling layer 19 positioned on the opposite side of the anti-reflective layer 13 from the hard coat layer 12. In other words, the anti-reflective film 10 has a transparent film substrate 11, a hard coat layer 12, a primer layer 18, an anti-reflective layer 13, and an anti-fouling layer 19 in this order.

[0040] The anti-reflective layer 13 has four layers in this order from the hard coat layer 12 side (primer layer 18 side): 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. Details of the high refractive index layer and the low refractive index layer will be described later. Note that the anti-reflective layer of the anti-reflective film ARF is not limited to a four-layer configuration like the anti-reflective layer 13, but may be a two-layer, three-layer, five-layer, or six-layer or more laminated configuration. Preferably, the anti-reflective layer of the anti-reflective film ARF is 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 furthest from the hard coat layer 12) of the anti-reflective layer of the anti-reflective film ARF is a low refractive index layer.

[0041] The anti-reflective film ARF may have a different layer configuration than the anti-reflective film 10 shown in Figure 1. For example, the anti-reflective film ARF may be an anti-reflective film 20, further comprising an adhesive layer 21 located on the opposite side of the transparent film substrate 11 from the hard coat layer 12, as shown in Figure 2.

[0042] The adhesive constituting the adhesive layer 21 is not particularly limited, and transparent adhesives based on polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate-vinyl chloride copolymers, modified polyolefins, epoxy resins, fluororesins, natural rubbers, and synthetic rubbers can be appropriately selected and used. The thickness of the adhesive layer 21 is not particularly limited, but from the viewpoint of achieving both thinness and adhesion, it is preferably 5 μm to 100 μm.

[0043] A release liner (not shown) may be temporarily attached to the main surface of the adhesive layer 21 opposite to the transparent film substrate 11. The release liner protects the surface of the adhesive layer 21 until, for example, the anti-reflective film 20 is bonded to the image display panel 101 (see Figure 3), which will be described later. A plastic film made from acrylic, polyolefin, cyclic polyolefin, polyester, etc., is preferably used as the material for the release liner. The thickness of the release liner is, for example, 5 μm to 200 μm. It is preferable that the surface of the release liner is treated with a release agent. Examples of release agents used in the release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty acid amide-based materials.

[0044] The configuration of the anti-reflective film according to the first embodiment has been described above with reference to the drawings, but the anti-reflective film according to the present invention is not limited to the configuration described above.

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

[0046] Furthermore, the anti-reflective film according to the present invention may be an anti-reflective film that does not include a primer layer and an anti-fouling layer. Also, the anti-reflective film according to the present invention may include an optical functional layer different from the layers included in the above-described configuration (transparent film substrate, hard coat layer, primer layer, anti-reflective layer, and anti-fouling layer).

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

[0048] [Transparent film substrate] The transparent film substrate is, for example, a flexible transparent resin film. 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 resins include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resins include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of cellulose resins include triacetylcellulose (TAC). These materials may be used individually or in combination of two or more. From the viewpoint of transparency and strength, the material for the transparent film substrate is preferably one selected from the group consisting of polyester resin, polyolefin resin, and cellulose resin, more preferably one selected from the group consisting of PET, COP, and TAC, and even more preferably PET. In other words, the transparent film substrate is preferably a film selected from the group consisting of polyester resin film, polyolefin resin film, and cellulose resin film, more preferably a film selected from the group consisting of PET film, COP film, and TAC film, and even more preferably a PET film.

[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 ease of handling, the thickness of the transparent film substrate is preferably 300 μm or less, more preferably 200 μm or less.

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

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

[0052] [Hard coat layer] The hard coat layer is a layer that enhances the mechanical properties of the anti-reflective film, such as its hardness and elastic modulus. The hard coat layer is made of, for example, a cured product of a curable resin composition (composition for forming a hard coat layer). Examples of curable resins included 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 individually or in combination of two or more types. From the viewpoint of increasing the hardness of the hard coat layer, it is preferable that the curable resin be one or more selected from the group consisting of acrylic resin and acrylic urethane resin, and more preferably acrylic resin.

[0053] Furthermore, examples of curable resin compositions include ultraviolet-curable resin compositions and thermosetting resin compositions. From the viewpoint of improving the productivity of anti-reflective films, ultraviolet-curable resin compositions are preferred as curable resin compositions. An ultraviolet-curable resin composition includes one or more selected from the group consisting of ultraviolet-curable monomers, ultraviolet-curable oligomers, and ultraviolet-curable polymers. A specific example of an ultraviolet-curable resin composition is the hard coat layer forming composition described in Japanese Patent Application Publication No. 2016-179686.

[0054] Furthermore, the curable resin composition may contain fine particles. By incorporating fine particles into the curable resin composition, it becomes possible to adjust the hardness, surface roughness, refractive index, and anti-glare properties of the hard coat layer. Examples of fine particles include metal oxide particles, glass particles, and organic particles. Examples of materials for 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.

[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 anti-reflective film, 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.

[0056] The main surface of the hard coat layer opposite to the transparent film substrate may be surface modified. Examples of surface modification treatments include plasma treatment, corona treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment. In order to improve the adhesion between the hard coat layer and the layer provided on the opposite side of the hard coat layer from the transparent film substrate (for example, the primer layer described later), it is preferable that the main surface of the hard coat layer opposite to the transparent film substrate is plasma treated.

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

[0058] In order to improve adhesion between the hard coat layer and the anti-reflective layer while ensuring light transmittance of the primer layer, the thickness of the primer layer is preferably 0.5 nm to 20 nm, more preferably 0.5 nm to 10 nm, and even more preferably 1.0 nm to 10 nm.

[0059] [Anti-reflection layer] An anti-reflective layer consists of two or more thin films with different refractive indices. Generally, the optical thickness (product of refractive index and thickness) of the anti-reflective layer is adjusted so that the reversed phases of the incident and reflected light cancel each other out. By making the anti-reflective layer a multilayer laminate of two or more thin films with different refractive indices, the reflectance can be reduced over a broad wavelength range of visible light.

[0060] Examples of materials for the thin film constituting the anti-reflective layer include metal (or metalloid) oxides, nitrides, fluorides, etc. Preferably, the anti-reflective layer is an alternating laminate of high refractive index layers and low refractive index layers.

[0061] The high refractive index layer has a refractive index of, for example, 1.9 or higher, preferably 2.0 or higher. Examples of materials for the high refractive index layer include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, ITO, and antimond-doped tin oxide (ATO). Among these, one or more selected from the group consisting of titanium oxide and niobium oxide are preferred. The low refractive index layer has a refractive index of, for example, 1.6 or lower, preferably 1.5 or lower. Examples of materials for the low refractive index layer include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, and lanthanum fluoride. Among these, silicon oxide is preferred. In particular, it is preferable to alternately laminate a thin film of niobium oxide (Nb2O5) as the high refractive index layer and a thin film of silicon oxide (SiO2) 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 with a refractive index greater than 1.6 and less than 1.9 may be provided.

[0062] The film thickness of the high refractive index layer and the low refractive index layer is preferably 5 nm to 200 nm, and more preferably 10 nm to 150 nm. Depending on the refractive index and the lamination configuration, the film thickness of each layer should be designed to reduce the reflectivity of visible light. For example, a lamination configuration of high refractive index and low refractive index layers may consist of four layers from the hard coat layer side: a high refractive index layer with an optical film thickness of 20 nm to 55 nm, a low refractive index layer with an optical film thickness of 35 nm to 55 nm, a high refractive index layer with an optical film thickness of 80 nm to 250 nm, and a low refractive index layer with an optical film thickness of 100 nm to 150 nm.

[0063] When the anti-reflective layer is a four-layer alternating laminate in which a niobium oxide (Nb2O5) thin film as a high refractive index layer and a silicon oxide (SiO2) thin film as a low refractive index layer are alternately laminated, the configuration of the anti-reflective layer can be such that, from the hard coat layer side, it comprises a niobium oxide thin film with a thickness of 5 nm to 20 nm, a silicon oxide thin film with a thickness of 20 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 this order.

[0064] To obtain an anti-reflective film with superior flexibility under harsh environments, the thickness of the anti-reflective layer is preferably 150 nm to 280 nm, more preferably 180 nm to 280 nm, even more preferably 190 nm to 260 nm, and even more preferably 200 nm to 250 nm. In this specification, "thickness of the anti-reflective layer" refers to the sum of the thicknesses of each layer constituting the anti-reflective layer (total thickness).

[0065] [Stain-resistant layer] The anti-reflective film preferably has an anti-fouling layer on the side opposite to the hard coat layer of the anti-reflective layer, and more preferably has the anti-fouling layer as the outermost layer of the anti-reflective film. By providing an anti-fouling layer, for example, the effects of contamination from the external environment (fingerprints, smudges, dust, etc.) can be reduced, and contaminants adhering to the surface of the anti-reflective film can be easily removed.

[0066] To suppress the deterioration of the anti-reflective performance of the anti-reflective layer, it is preferable that the difference in refractive index between the anti-fouling layer and the outermost layer of the anti-reflective layer (e.g., the low refractive index layer) is small. The refractive index of the anti-fouling layer is preferably 1.6 or less, and more preferably 1.55 or less.

[0067] As a material for the antifouling layer, fluorine-containing compounds are preferred. Fluorine-containing compounds offer excellent antifouling properties while also contributing to a lower refractive index. Among these, alkoxysilane compounds containing a perfluoropolyether skeleton are preferred because they offer excellent water repellency and high antifouling properties. Examples of alkoxysilane compounds containing a perfluoropolyether skeleton include alkoxysilane compounds having multiple linear or branched perfluoroalkylene oxide units with 1 to 4 carbon atoms. Examples of linear or branched perfluoroalkylene oxide units with 1 to 4 carbon atoms include perfluoromethylene oxide units (-CF2O-), perfluoroethylene oxide units (-CF2CF2O-), perfluoropropylene oxide units (-CF2CF2CF2O-), and perfluoroisopropylene oxide units (-CF(CF3)CF2O-).

[0068] The thickness of the antifouling layer is, for example, 2 nm to 50 nm. The greater the thickness of the antifouling layer, the better the antifouling performance tends to be. The thickness of the antifouling layer is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 8 nm or more. On the other hand, from the viewpoint of improving anti-glare performance, the thickness of the antifouling layer is preferably 30 nm or less, and more preferably 20 nm or less.

[0069] [Preferred embodiment of anti-reflective film] In order to obtain an anti-reflective film with particularly excellent bending resistance at high temperatures, the anti-reflective film according to the first embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, even more preferably satisfies the following condition 3, and even more preferably satisfies the following condition 4. Condition 1: At least one of the dimensional change rates in the first and second directions before and after the heat resistance test is 0.00% or more and 0.04% or less. Condition 2: The above condition 1 is met, and the thickness of the anti-reflective layer is between 150 nm and 280 nm. 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: The above condition 3 is met, and the thickness of the anti-reflective layer is between 150 nm and 280 nm.

[0070] Furthermore, in order to obtain an anti-reflective film that is particularly excellent in bending resistance under high temperature and high humidity, the anti-reflective film according to the first embodiment preferably satisfies the following condition i, more preferably satisfies the following condition ii, even 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 and second directions before and after the humidity and heat resistance test are both between 0.05% and 0.13%. Condition ii: The above condition i is met, and the thickness of the anti-reflective 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 humidity and 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 humidity and heat resistance test is 0.10% or more and 0.13% or less. Condition iv: The above condition iii is met, and the thickness of the anti-reflective layer is 150 nm or more and 280 nm or less.

[0071] Furthermore, in order to obtain an anti-reflective film that is particularly excellent in bending resistance at high temperatures and particularly excellent in bending resistance at high temperatures and high humidity, the anti-reflective film according to the first embodiment preferably satisfies conditions 1 and i, more preferably satisfies conditions 2 and ii, even more preferably satisfies conditions 3 and iii, and even more preferably satisfies 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 comprises an image display panel and an anti-reflective film according to the first embodiment, which is arranged on the viewing side of the image display panel. Details that overlap with the first embodiment will be omitted from the description below.

[0073] Figure 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 Figure 3 comprises an image display panel 101 and an anti-reflective film 10, which is an example of an anti-reflective film according to the first embodiment, arranged on the viewing side (upper side in Figure 3) of the image display panel 101. In the image display device 100, the transparent film substrate 11 of the anti-reflective film 10 and the image display panel 101 are bonded together via an adhesive layer 21.

[0074] An example of the image display panel 101 is an image display panel that includes image display cells such as liquid crystal cells and organic EL cells.

[0075] The image display device according to the second embodiment has an anti-reflective film placed on the viewing side of the image display panel, thereby reducing the reflection of ambient light and providing excellent visibility. Furthermore, since the image display device according to the second embodiment is equipped with the anti-reflective film according to the first embodiment (an anti-reflective film with excellent bending resistance in harsh environments), even when stored in a bent state with the anti-reflective layer forming surface facing inward, cracks in the anti-reflective layer are less likely to occur at the bending points. For this reason, the image display device according to the second embodiment can also be used as, for example, a foldable display. In order to obtain a foldable display that can further suppress the occurrence of cracks in the anti-reflective layer in harsh environments, it is preferable that the bending points of the foldable display are bending points where the anti-reflective film can be bent in a first direction.

[0076] <Third Embodiment: Method for Manufacturing Anti-Reflective Film> Next, a method for manufacturing an anti-reflective film according to the third embodiment of the present invention will be described. The method for manufacturing an anti-reflective film according to the third embodiment is a preferred method for manufacturing an anti-reflective film according to the first embodiment. Details that overlap with the first embodiment will be omitted from the description below.

[0077] The method for manufacturing an anti-reflective film according to the third embodiment comprises a step Sa of forming an anti-reflective layer on the side of the hard coat layer opposite to the transparent film substrate side using a roll-to-roll sputtering apparatus, and a step Sb of heating the laminate on which the anti-reflective layer has been formed after step Sa. Since the method for manufacturing an anti-reflective film according to the third embodiment comprises steps Sa and Sb, the anti-reflective film according to the first embodiment can be easily manufactured. Hereinafter, step Sa will be referred to as the "anti-reflective layer formation step," and step Sb will be referred to as the "anti-reflective layer heating step."

[0078] The method for manufacturing an anti-reflective film according to the third embodiment may include steps other than the anti-reflective layer formation step and the anti-reflective layer heating step. Examples of these other steps include the hard coat layer formation step, the hard coat layer surface treatment step, the hard coat layer heating step, the primer layer formation step, and the anti-fouling layer formation step, which will be described later.

[0079] The following describes each step of an example of a method for manufacturing an anti-reflective film according to the third embodiment.

[0080] [Hard coat layer formation process] The hard coat layer formation process is a process of forming a hard coat layer on a transparent film substrate. For example, a hard coat layer is formed by applying a curable resin composition (hard coat layer formation composition) to a transparent film substrate, and removing the solvent and curing the resin as needed. The hard coat layer formation composition includes, for example, the curable resin described above and a polymerization initiator (e.g., a photopolymerization initiator), and optionally includes a solvent capable of dissolving or dispersing these components.

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

[0082] Any suitable method can be used to apply the hard coat layer formation composition, such as the bar coating method, roll coating method, gravure coating method, rod coating method, slot orifice coating method, curtain coating method, fountain coating method, or comma coating method. The drying temperature of the coating film after application should be set to an appropriate temperature depending on the composition of the hard coat layer formation composition, for example, 50°C to 150°C. If the resin component in the hard coat layer formation composition is a thermosetting resin, the coating film is cured by heating. If the resin component in the hard coat layer formation composition is a photocurable resin, the coating film is cured by irradiation with active energy rays such as ultraviolet light. The integrated amount of the irradiated light is preferably 100 mJ / cm². 2 More than 500mJ / cm 2 The following applies:

[0083] [Surface treatment process for the hard coat layer] In the surface treatment process for the hard coat layer, the main surface of the hard coat layer opposite to the transparent film substrate side is subjected to surface modification treatment. Examples of surface modification treatments 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 plasma treatment is, for example, between 10W and 10,000W.

[0084] [Hard coat layer heating process] 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 applying other layers (for example, a primer layer, an anti-reflective layer, etc.) on top of the hard coat layer. By providing a hard coat layer heating step, for example, dimensional changes of the anti-reflective film due to thermal shrinkage of the transparent film substrate can be suppressed.

[0085] In the third embodiment, since a roll-to-roll sputtering apparatus is used in the anti-reflective layer formation process, it is preferable to heat the laminate while conveying it in a roll-to-roll manner during the hard coat layer heating process, from the viewpoint of increasing productivity. Examples of heating devices include a hot air oven and an infrared heater.

[0086] The heating temperature of the laminate in the hard coat layer heating step is, for example, 100°C to 200°C. The heating time of the laminate in the hard coat layer heating step is, for example, 30 seconds to 30 minutes. When a hard coat layer surface treatment step and a hard coat layer heating step are provided, the hard coat layer heating step may be performed before or after the hard coat layer surface treatment step.

[0087] [Primer layer formation process] The primer layer formation step is a step of forming (depositing) a primer layer on the hard coat layer. The method of depositing 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 uniform thickness. Furthermore, in the third embodiment, since a roll-to-roll sputtering deposition apparatus is used in the anti-reflective layer formation step, from the viewpoint of increasing productivity, a method of depositing the primer layer using a roll-to-roll sputtering deposition apparatus (roll-to-roll sputtering method) is preferred.

[0088] In the roll-to-roll sputtering method, a long film (for example, a transparent film substrate with a hard coat layer formed on it) can be transported in the longitudinal direction (MD direction) while continuously depositing, for example, a primer layer and an anti-reflective layer. In sputtering, film deposition is carried out while introducing an inert gas such as argon, and a reactive gas such as oxygen as needed, into the deposition chamber. When depositing an oxide layer as a primer layer, the deposition of the oxide layer by sputtering can be carried out using either an oxide target or reactive sputtering using a metal (or semimetallic) target.

[0089] Examples of power sources for performing the sputtering method include DC power supplies, AC power supplies, RF power supplies, and MFAC power supplies (AC power supplies 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, preferably 1 kW to 50 kW. The surface temperature of the film deposition roll when performing the sputtering method is, for example, -25°C to 25°C, preferably -20°C to 0°C. The pressure inside the film deposition chamber when performing 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.

[0090] [Anti-reflection layer formation process] In the anti-reflective layer formation process, the anti-reflective layer is formed on the side of the hard coat layer opposite to the transparent film substrate side (for example, the surface of the hard coat layer or the surface of the primer layer) using a roll-to-roll sputtering apparatus. In other words, in the third embodiment, each layer of the anti-reflective layer is formed by the roll-to-roll sputtering method. When performing the sputtering method in the anti-reflective layer formation process, the film formation conditions can be appropriately set from among the conditions described in the [primer layer formation process] above.

[0091] Our studies have revealed that when each layer of an anti-reflective layer is formed by a roll-to-roll sputtering method, the anti-reflective film is prone to shrinkage under harsh conditions. In particular, when a stretched film such as PET film is used as the transparent film substrate, the shrinkage of the anti-reflective film becomes significant. When the laminate forming the anti-reflective layer (for example, a film-like laminate having at least a transparent film substrate and a hard coat layer) is transported by a roll-to-roll method, tension is applied to the laminate in the transport direction, which is presumed to generate residual stress in the laminate, making the anti-reflective film prone to shrinkage under harsh conditions.

[0092] [Anti-fouling layer formation process] The antifouling layer formation process involves forming an antifouling layer on the side of the anti-reflective layer opposite to the hard coat layer. In the antifouling layer formation process, for example, a fluorine-containing compound is used as the material, and the antifouling layer is formed by a dry coating method. Examples of dry coating methods include vacuum deposition, sputtering, and CVD, with vacuum deposition being preferred.

[0093] [Anti-reflection layer heating process] The anti-reflective layer heating step is a step of heating a laminate on which an anti-reflective layer has been formed (hereinafter sometimes referred to as "film with anti-reflective layer"). By heating the film with anti-reflective layer, at least a portion of the residual stress in the film is removed, for example, and shrinkage of the anti-reflective layer under harsh conditions is suppressed. As a result, an anti-reflective film with excellent bending resistance under harsh conditions can be obtained. If an anti-fouling layer formation step is provided, the anti-reflective layer heating step may be performed before or after the anti-fouling layer formation step. If an anti-fouling layer formation step is provided, it is preferable to perform the anti-reflective layer heating step after the anti-fouling layer formation step in order to obtain an anti-reflective film with even better bending resistance under harsh conditions.

[0094] In the third embodiment, since a roll-to-roll sputtering apparatus is used in the anti-reflective layer formation process, it is preferable to heat the anti-reflective layer while conveying the film with the anti-reflective layer in a roll-to-roll manner during the anti-reflective layer heating process, from the viewpoint of increasing productivity. Examples of heating devices include a hot air oven and an infrared heater.

[0095] To obtain an anti-reflective film with superior bending resistance in harsh environments, the heating temperature of the film with the anti-reflective layer in the anti-reflective layer heating step is preferably 110°C or higher, more preferably 115°C or higher, even 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. Furthermore, to obtain an anti-reflective film with superior bending resistance in harsh environments, the heating time of the film with the anti-reflective layer in the anti-reflective layer heating step is preferably 30 seconds or higher, more preferably 1 minute or higher, even more preferably 2 minutes or higher, and may be 5 minutes or higher, 10 minutes or higher, or 15 minutes or higher.

[0096] To suppress the decrease in transparency of the anti-reflective film, the heating temperature of the film with the anti-reflective layer in the anti-reflective layer heating process is preferably 200°C or lower, and more preferably 190°C or lower. Furthermore, to suppress the decrease in transparency of the anti-reflective film, the heating time of the film with the anti-reflective layer in the anti-reflective layer heating process is preferably 30 minutes or lower, and more preferably 20 minutes or lower.

[0097] The dimensional change rates in the first and second directions before and after the above heat resistance test, as well as the dimensional change rates in the first and second directions before and after the above moisture and heat resistance test, can all be adjusted by changing the heating conditions (specifically, heating temperature, heating time, etc.) in the anti-reflective layer heating process. [Examples]

[0098] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0099] <Fabrication of anti-reflective film in Example 1> [Hard coat layer formation process] A mixture was prepared by mixing 100 parts by weight of an ultraviolet-curable polyfunctional acrylic resin composition (Aica Kogyo Co., Ltd. "Z-850-50H-D", solids concentration: 44% by weight) on a solids basis, 4 parts by weight of a photopolymerization initiator (IGM Resins "Omnirad2959"), and 0.05 parts by weight of a leveling agent (Kyoeisha Chemical Co., Ltd. "LE-303"). Methyl isobutyl ketone was then added to the mixture to obtain a hard coat layer forming composition with a solids concentration of 40% by weight. Next, the hard coat layer forming composition was applied to one main surface of a PET film (Toray Industries, Inc. "50U48", thickness: 50 μm) as a transparent film substrate to form a coating film. This coating film was then dried by heating at 80°C for 60 seconds and then cured by ultraviolet irradiation. When irradiating with ultraviolet light, a high-pressure mercury lamp is used as the light source, with ultraviolet light at a wavelength of 365 nm and an integrated light intensity of 300 mJ / cm². 2 This resulted in the formation of a 3 μm thick hard coat layer on the PET film.

[0100] [Surface treatment process for the hard coat layer] Next, using a roll-to-roll plasma processing apparatus, the surface of the hard coat layer was plasma-treated while the PET film with the hard coat layer formed on it was being transported under a vacuum atmosphere of 1.0 Pa. During the plasma treatment, argon gas was used as the inert gas, and the discharge power was set to 150 W. As a result, a laminate comprising the PET film and the plasma-treated hard coat layer (hereinafter sometimes referred to as "optical film F1") was obtained.

[0101] [Hard coat layer heating process] Next, the optical film F1 was heated in a hot air oven at 140°C for 2 minutes while being transported by a roll-to-roll conveying device.

[0102] [Primer layer formation process] Next, the heated optical film F1 is introduced into a roll-to-roll sputtering deposition apparatus, and the deposition chamber is filled to 1 × 10 -4The pressure was reduced to Pa. Next, while transporting the optical film F1, argon gas and oxygen gas were introduced in a volume ratio of 100:10 to set the surface temperature of the deposition roll to -8°C, and a 1.5 nm thick ITO layer (primer layer) 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 in a weight ratio of 90:10 was used as the target material. When depositing the film by sputtering, an MFAC power supply was used, the discharge power was set to 2.5 kW, and the pressure inside the deposition chamber was set to 0.2 Pa.

[0103] [Anti-reflection layer formation process] Following the formation of the primer layer, the optical film F1 after the primer layer formation was transported using a roll-to-roll sputtering deposition apparatus, and the following layers were deposited on the primer layer by sputtering: the first layer: a 12 nm thick Nb2O5 layer (refractive index: 2.33), the second layer: a 28 nm thick SiO2 layer (refractive index: 1.46), the third layer: a 100 nm thick Nb2O5 layer, and the fourth layer: an 85 nm thick SiO2 layer. This formed a four-layer anti-reflective layer (consisting of the first, second, third, and fourth layers) on the primer layer. For the deposition of each of the first to fourth layers, the surface temperature of the deposition roll was set to -8°C, the power supply was an MFAC power supply, and the pressure inside the deposition chamber was set to 0.7 Pa. In addition, for the deposition of the first layer, an 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 10.5 kW. For the deposition of the second layer, a Si target was used, and argon gas and oxygen gas were introduced in a volume ratio of 100:30, with a discharge power of 14 kW. For the deposition of the third layer, an Nb target was used, and argon gas and oxygen gas were introduced in a volume ratio of 100:13, with a discharge power of 22 kW. For the deposition of the fourth layer, a Si target was used, and argon gas and oxygen gas were introduced in a volume ratio of 100:30, with a discharge power of 12 kW.

[0104] [Anti-fouling layer formation process] A coating agent (SHIN-ETSU SUBELYN KY1903-1, manufactured by Shin-Etsu Chemical Co., Ltd., with the active ingredient being an alkoxysilane compound containing a perfluoropolyether skeleton) was dried and solidified and used as a deposition source. The deposition source was heated to 260°C, and a 12 nm thick antifouling layer was formed on the anti-reflective layer by vacuum deposition. This resulted in a laminate comprising a PET film, a hard coat layer, a primer layer, an anti-reflective layer, and an antifouling layer (hereinafter sometimes referred to as "optical film F2").

[0105] [Anti-reflection layer heating process] Next, the optical film F2 was heated in a hot air oven at 120°C for 2 minutes while being transported by a roll-to-roll conveying device. This yielded the anti-reflective film of Example 1.

[0106] <Preparation of anti-reflective films for Examples 2-9 and Comparative Examples 1-5> Except for changing the heating conditions of optical film F1 in the hard coat layer heating step and the heating conditions of optical film F2 in the anti-reflective layer heating step to the conditions shown in Table 1, the anti-reflective films of Examples 2-9 and Comparative Examples 1-5 were obtained using the same manufacturing method as in Example 1. In the production of the anti-reflective films of Examples 6-9 and Comparative Example 4, the hard coat layer heating step was not performed. In addition, in the production of the anti-reflective films of Comparative Examples 4 and 5, the anti-reflective layer heating step was not performed.

[0107] [Table 1]

[0108] <Method for measuring dimensional change rate> [Method for measuring dimensional change rate before and after heat resistance testing] To measure the dimensional change rate before and after the heat resistance test, test pieces measuring 100mm x 100mm (length in the MD direction: 100mm, length in the TD direction: 100mm) were cut from each anti-reflective film using a laser cutting machine (GCC's "LaserPro Spirit GLS"). The ambient temperature and relative humidity when cutting the test pieces were 20°C and 50%, respectively. Next, each test piece was subjected to a heat resistance test by being left to stand for 48 hours in a drying oven (ESPEC's "PH-202") at a temperature of 85°C and a relative humidity of 1% or less. After that, it was left to stand for 24 hours in an atmosphere of 20°C and a relative humidity of 50%, and the dimensional change rate before and after the heat resistance test was determined. Specifically, the dimensional change rate in each direction (MD direction and TD direction) of each test specimen was calculated using the above formula, based on the length L1 (100 mm) in each direction at a temperature of 20°C and relative humidity of 50% before the heat resistance test, and the length L2 in each direction measured after standing for 24 hours in an atmosphere of 20°C and relative humidity after the heat resistance test.

[0109] [Method for measuring dimensional change rate before and after humidity and heat resistance testing] To measure the dimensional change rate before and after the humidity and heat resistance test, test pieces measuring 100mm x 100mm (length in the MD direction: 100mm, length in the TD direction: 100mm) were cut from each anti-reflective film using a laser cutting machine (GCC's "LaserPro Spirit GLS"). The ambient temperature and relative humidity when cutting the test pieces were 20°C and 50%, respectively. Next, each test piece was subjected to a humidity and heat resistance test by being left to stand for 48 hours in a constant temperature and humidity testing chamber (ESPEC's "PL-2J") at a temperature of 60°C and a relative humidity of 95%, and then left to stand for 24 hours in an atmosphere of 20°C and a relative humidity of 50%, and the dimensional change rate before and after the humidity and heat resistance test was determined. Specifically, the dimensional change rate in each direction (MD direction and TD direction) of each test specimen was calculated using the above formula, based on the length L1 (100 mm) in each direction at a temperature of 20°C and relative humidity of 50% before the humid and heat resistance test, and the length L2 in each direction measured after standing for 24 hours in an atmosphere of 20°C and relative humidity of 50% following the humid and heat resistance test.

[0110] <Bending resistance evaluation> [Evaluation of bending resistance under high temperature conditions] To evaluate the bending resistance at high temperatures, test specimens 200 measuring 10 mm wide x 100 mm long (length direction: MD direction, width direction: TD direction) were cut from each anti-reflective film using a laser processing machine (GCC's "LaserPro Spirit GLS"). Next, as shown in Figure 4, the test specimen 200 was bent in the MD direction (X direction in Figure 4) with the anti-reflective layer (not shown) side facing inward, and both ends in the MD direction were attached to spacers 300 with a thickness D (D: 4.0 mm or 3.8 mm). In the state shown in Figure 4, the bending radius of the bent portion of the test specimen 200 was D / 2. Next, the test specimen 200 in the state shown in Figure 4 was left to stand for 48 hours in a drying oven (ESPEC's "PH-202") at a temperature of 85°C and a relative humidity of 1% or less, and then removed. The presence or absence of cracks (whitening of the anti-reflective layer) in the bent portion was checked using an optical microscope. If no cracks were found, it was judged as A. On the other hand, if cracks were found, the rating was B. When using a 4.0 mm thick spacer, a rating of A was given, indicating "excellent bending resistance at high temperatures," while a rating of B was given, indicating "poor bending resistance at high temperatures."

[0111] [Evaluation of bending resistance under high temperature and high humidity conditions] To evaluate the bending resistance under high temperature and high humidity conditions, test specimens 200 measuring 10 mm wide x 100 mm long (length direction: MD direction, width direction: TD direction) were cut from each anti-reflective film using a laser processing machine (GCC's "LaserPro Spirit GLS"). Next, as shown in Figure 4, the test specimen 200 was bent in the MD direction (X direction in Figure 4) with the anti-reflective layer (not shown) side facing inward, and both ends in the MD direction were attached to spacers 300 with a thickness D (D: 4.0 mm or 3.8 mm). In the state shown in Figure 4, the bending radius of the bent portion of the test specimen 200 was D / 2. Next, the test specimen 200 in the state shown in Figure 4 was left to stand for 48 hours in a constant temperature and humidity test chamber (ESPEC's "PL-2J") at a temperature of 60°C and relative humidity of 95%, and then removed. The presence or absence of cracks (whitening of the anti-reflective layer) in the bent portion was checked using an optical microscope. If no cracks were found, it was judged as A. On the other hand, if cracks were found, the result was judged as B. If the result was A when using a 4.0 mm thick spacer, it was evaluated as having "excellent bending resistance under high temperature and high humidity conditions," and if the result was B when using a 4.0 mm thick spacer, it was evaluated as having "poor bending resistance under high temperature and high humidity conditions."

[0112] <Evaluation Results> Table 2 shows the dimensional change rates before and after the heat resistance test, the dimensional change rates before and after the humid heat resistance test, and the results of the bending resistance evaluation for Examples 1 to 9 and Comparative Examples 1 to 5. In Table 2, "4.0 mm" and "3.8 mm" both refer to the thickness of the spacer used in the bending 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 between -0.10% and 0.10%. In Examples 1 to 9, the dimensional change rate in the MD direction before and after the humid heat resistance test was between 0.01% and 0.20%.

[0115] As shown in Table 2, in Examples 1 to 9, the evaluation result for bending resistance at high temperatures when using a 4.0 mm thick spacer was A. Therefore, the anti-reflective films of Examples 1 to 9 had excellent bending resistance at high temperatures. In Examples 1 to 9, the evaluation result for bending resistance at high temperature and high humidity when using a 4.0 mm thick spacer was A. Therefore, the anti-reflective films of Examples 1 to 9 had excellent bending resistance at high temperature and high humidity.

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

[0117] As shown in Table 2, in Comparative Examples 1 to 5, the evaluation result for bending resistance at high temperatures when using a 4.0 mm thick spacer was B. Therefore, the anti-reflective films of Comparative Examples 1 to 5 did not have excellent bending resistance at high temperatures. In Comparative Examples 1 to 5, the evaluation result for bending resistance at high temperature and high humidity when using a 4.0 mm thick spacer was B. Therefore, the anti-reflective films of Comparative Examples 1 to 5 did not have excellent bending resistance at high temperature and high humidity.

[0118] The results above demonstrate that the present invention can provide an anti-reflective film with excellent flexibility under harsh environments. [Explanation of Symbols]

[0119] 10, 20 Anti-reflective film 11 Transparent film substrate 12 Hard Court Layers 13 Anti-reflection layer 18. Primer layer 19. Anti-fouling layer 21 Adhesive layer 100 Image Display Devices 101 Image display panel

Claims

1. An anti-reflective film having a transparent film substrate, a hard coat layer, a primer layer, and an anti-reflective layer in this order, When a heat resistance test was conducted by holding the material 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 was -0.10% or more and 0.10% or less. The anti-reflective layer is an alternating laminate of a niobium oxide thin film and a silicon oxide thin film. An anti-reflective film having an anti-reflective layer thickness of 150 nm or more and 260 nm or less.

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

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

4. The anti-reflective film according to claim 3, wherein the dimensional change rate in the direction perpendicular to the direction of the edge before and after the aforementioned heat and humidity resistance test is 0.01% or more and 0.20% or less.

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

6. The anti-reflective film according to claim 1 or 3, further comprising an anti-fouling layer disposed on the opposite side of the anti-reflective layer from the hard coat layer side.

7. The anti-reflective film according to claim 1 or 3, further comprising an adhesive layer disposed on the side of the transparent film substrate opposite to the hard coat layer.

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

9. A method for manufacturing an anti-reflective film according to claim 1 or 3, Step Sa of forming the anti-reflective layer on the side of the hard coat layer opposite to the transparent film substrate side using a roll-to-roll sputtering deposition apparatus, A method for manufacturing an anti-reflective film, comprising the step Sa followed by a step Sb of heating the laminate on which the anti-reflective layer is formed.

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

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