JP2024048953A - Anti-reflection film, its manufacturing method, and image display device - Google Patents

Abstract

[Problem] To provide an anti-reflection film that, when applied to an image display device equipped with a touch sensor, is less likely to cause detection anomalies in the touch sensor. [Solution] An anti-reflection film (101) comprises a primer layer (3) and an anti-reflection layer (5) on one main surface of a transparent film substrate (1). The anti-reflection layer is a laminate of multiple thin films with different refractive indices. The primer layer is a conductive metal oxide layer. It is preferable that the primer layer has a small change in resistance due to ultraviolet light irradiation. It is preferable that the carrier mobility of the primer layer is 13.5 cm2/V.s or less. [Selected Figure] Figure 1

Description

The present invention relates to an anti-reflection film and a manufacturing method thereof. Furthermore, the present invention relates to an image display device including an anti-reflection film.

Anti-reflection films are sometimes provided on the surfaces of image display devices such as liquid crystal displays and organic EL displays in order to improve the visibility of displayed images. Anti-reflection films have an anti-reflection layer made up of multiple thin films with different refractive indices on a film substrate. Anti-reflection films that use inorganic thin films such as inorganic oxides as the thin films that make up the anti-reflection layer can easily adjust the refractive index and film thickness, thereby achieving high anti-reflection properties.

An anti-reflective film has an anti-reflective layer made of an inorganic thin film on a resin film or on a hard coat layer provided on the surface of the resin film, but organic materials such as the resin film and hard coat layer have low interlayer adhesion with the inorganic thin film. Therefore, in order to increase the adhesion of the anti-reflective layer to the film substrate, it has been proposed to provide an inorganic oxide primer layer on the surface of the film substrate and then form the anti-reflective layer on top of that.

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

International Publication No. 2021/106788

Indium oxide-based materials such as ITO are conductive. By using a conductive material as the primer layer, the anti-reflection film has antistatic properties, making it possible to suppress malfunctions of the touch sensor caused by static electricity. However, in an image display device in which an anti-reflection film is arranged on the viewing side surface of an image display panel equipped with a touch sensor, if the primer layer of the anti-reflection film is made of a conductive material, abnormalities may occur in detection by the touch sensor when used outdoors, making touch operation difficult or impossible.

In view of the above, the present invention aims to provide an anti-reflection film that is less likely to cause touch detection abnormalities when applied to an image display device equipped with a touch sensor.

The inventors of the present invention have investigated the causes of touch sensor detection abnormalities when an image display device is used outdoors, and have found that ultraviolet light irradiation causes a temporary change in the resistance of the primer layer of the anti-reflection film, which they have hypothesized is one of the causes of the touch detection abnormalities. As a result of further investigation based on this assumption, they have found that by providing an anti-reflection film with a specific primer layer, it is possible to suppress touch sensor detection abnormalities under ultraviolet light.

One embodiment of the present invention relates to an anti-reflective film having a primer layer and an anti-reflective layer on one main surface of a transparent film substrate. The anti-reflective layer is a laminate of multiple thin films with different refractive indices. The anti-reflective film may have an anti-glare layer on the anti-reflective layer.

The primer layer is a conductive metal oxide layer. The thickness of the primer layer is preferably 0.5 to 10 nm. The surface resistance _R0 of the primer layer is preferably 1×10 ⁸ to 5×10 ¹¹ Ω/sq. The ratio _R0 / _R1 of the surface resistance _R1 of the primer layer after irradiation with ultraviolet light at a radiation intensity of 1.6 W/ ^m2 for 1 minute to the surface resistance _R0 of the primer layer before irradiation with ultraviolet light is preferably 100 or less.

The carrier mobility of the primer layer is preferably 13.5 cm ² /V·s or less. When the carrier mobility of the primer layer is small, the rate of change in resistance R ₀ /R ₁ due to ultraviolet light irradiation tends to be small.

The conductive oxide constituting the primer layer is preferably an indium oxide-based material. In one embodiment, the conductive oxide is indium tin oxide (ITO). In the ITO primer layer, the amount of tin oxide relative to the total of indium oxide and tin oxide is preferably 3 to 60% by weight. The ITO primer layer may have a peak intensity at 532 eV in an X-ray photoelectron spectroscopy spectrum that is 0.93 times or less than the peak intensity at 530 eV.

The transparent film substrate of the anti-reflection film may be a hard-coated film having a hard-coated layer on one main surface of a transparent resin film. The hard-coated layer contains a cured product of a curable resin. The hard-coated layer may further contain fine particles. When the transparent film substrate is a hard-coated film, it is preferable that a primer layer is provided in contact with the hard-coat layer.

The primer layer is formed, for example, by a sputtering method using an oxide target. The anti-reflective layer is formed, for example, by a sputtering method. The anti-reflective layer can also be formed by reactive sputtering.

Anti-reflection films are suitable for use as components of image display devices, and are placed, for example, on the viewing side surface of an image display device equipped with a touch sensor.

The anti-reflection film of the present invention has a primer layer between the transparent film substrate and the anti-reflection layer, so that the anti-reflection layer has excellent adhesion, and the primer layer is conductive and has antistatic properties, so that malfunction of the touch sensor caused by static electricity can be suppressed. In addition, since the resistance change of the primer layer due to ultraviolet irradiation is small, even when the touch sensor is irradiated with ultraviolet rays during use of an image display device outdoors, it is unlikely to malfunction.

FIG. 1 is a cross-sectional view of an anti-reflection film according to an embodiment. 1 is a cross-sectional view of an image display device according to an embodiment.

Figure 1 is a cross-sectional view showing an example of a laminated structure of an anti-reflection film. The anti-reflection film 101 has a primer layer 3 on a transparent film substrate 1, and an anti-reflection layer 5 on the primer layer 3. The anti-reflection layer 5 is a laminate of two or more inorganic thin layers with different refractive indices. In the anti-reflection film 101 shown in Figure 1, the anti-reflection layer 5 has a structure in which high refractive index layers 51, 53 and low refractive index layers 52, 54 are alternately laminated. An anti-fouling layer 7 may be provided on the anti-reflection layer 5.

Figure 2 is a cross-sectional view showing a schematic configuration of an image display device having an anti-reflection film 101 on the viewing side surface of an image display panel 8. In the image display device 201, the anti-reflection film 101 is attached to the viewing side surface of the image display panel 8 via an appropriate adhesive layer 2. The image display panel 8 has a touch sensor function, and is provided with a touch sensor unit 85 for position detection on the viewing side surface of the image display unit 81.

The touch sensor unit 85 is equipped with an electrode (not shown) for position detection. When a finger or a touch pen touches the viewing side surface (the antifouling layer 7 of the antireflection film 101) of the image display device 201, the capacitance of the electrode changes. The touch position is detected by detecting this change in capacitance.

[Anti-reflection film]
<Transparent film substrate>
A transparent resin film is used as the transparent film substrate 1. The transparent film substrate 1 may be a transparent resin film 10 having a hard coat layer 11 on one side thereof. The total light transmittance of the transparent film substrate 1 is preferably 80% or more, more preferably 90% or more. The thickness of the transparent film substrate 1 is not particularly limited, but from the viewpoints of workability such as strength and handleability, thin layer property, etc., it is preferably about 5 to 300 μm, more preferably 10 to 250 μm, and even more preferably 20 to 200 μm.

(Transparent resin film)
Resin materials excellent in transparency, mechanical strength, and thermal stability are preferable as the resin material constituting the transparent resin film 10. Specific examples of the resin material include cellulose-based resins such as triacetyl cellulose, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof.

(Hard Coat Layer)
By providing the hard coat layer 11 on the antireflection layer-forming surface of the transparent resin film 10, the mechanical properties such as surface hardness and scratch resistance of the antireflection film can be improved. A hard coat layer (not shown) may also be provided on the back surface of the transparent resin film 10.

Examples of the curable resin constituting the hard coat layer 11 include thermosetting resins, photocurable resins, and electron beam curable resins. Types of curable resins include polyester, acrylic, urethane, acryl urethane, amide, silicone, silicate, epoxy, melamine, oxetane, and acryl urethane. Among these, acrylic resins, acryl urethane resins, and epoxy resins are preferred because of their high hardness and the ability to be photocured, and acryl urethane resins are particularly preferred.

The photocurable resin composition contains a polyfunctional compound having two or more photopolymerizable (preferably ultraviolet-polymerizable) functional groups. The polyfunctional compound may be a monomer or an oligomer. As the photopolymerizable polyfunctional compound, a compound containing two or more (meth)acryloyl groups in one molecule (polyfunctional (meth)acrylate) is preferably used.

The hard coat layer 11 may contain fine particles. By containing fine particles in the hard coat layer, it is possible to adjust the surface shape, impart optical properties such as anti-glare properties, and improve the adhesion of the anti-reflection layer.

As the fine particles, inorganic oxide fine particles such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide, glass fine particles, crosslinked or uncrosslinked organic fine particles made of transparent polymers such as polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate, silicone fine particles, etc. can be used without any particular restrictions.

The average particle size (average primary particle size) of the microparticles is preferably about 10 nm to 10 μm. Depending on the particle size, the microparticles can be broadly classified into microparticles having an average particle size of about 0.5 μm to 10 μm, which is submicron or on the μm order (hereinafter sometimes referred to as "microparticles"), microparticles having an average particle size of about 10 nm to 100 nm (hereinafter sometimes referred to as "nanoparticles"), and microparticles having a particle size intermediate between microparticles and nanoparticles.

When the hard coat layer 11 contains nanoparticles, fine irregularities are formed on the surface, which tends to improve the adhesion between the hard coat layer 11 and the primer layer 3 and the anti-reflection layer 5. As the nanoparticles, inorganic fine particles are preferred, and inorganic oxide fine particles are particularly preferred. Among these, silica particles are preferred because they have a low refractive index and can reduce the difference in refractive index with the binder resin.

From the viewpoint of forming an uneven shape on the surface of the hard coat layer 11 that has excellent adhesion to an inorganic thin film such as the primer layer 3, the average primary particle diameter of the nanoparticles is preferably 20 to 80 nm, more preferably 25 to 70 nm, and even more preferably 30 to 60 nm. Furthermore, from the viewpoint of suppressing coloring of reflected light on the surface of the hard coat layer, the average primary particle diameter of the nanoparticles is preferably 55 nm or less, more preferably 50 nm or less, and even more preferably 45 nm or less. The average primary particle diameter is the weight average particle diameter measured by the Coulter count method.

The amount of nanoparticles in the hard coat layer 11 may be about 1 to 150 parts by weight per 100 parts by weight of the binder resin. From the viewpoint of forming a surface shape on the surface of the hard coat layer 11 that has excellent adhesion to the inorganic thin film, the content of nanoparticles in the hard coat layer 11 is preferably 20 to 100 parts by weight, more preferably 25 to 90 parts by weight, and even more preferably 30 to 80 parts by weight per 100 parts by weight of the binder resin.

By including microparticles in the hard coat layer 11, protrusions with diameters on the order of submicrons or μm are formed on the surface of the hard coat layer 11 and on the surface of the thin film formed thereon, imparting anti-glare properties. It is preferable that the microparticles have a small difference in refractive index from the binder resin of the hard coat layer, and low refractive index inorganic oxide particles such as silica, or polymer fine particles are preferred.

From the viewpoint of forming a surface shape suitable for imparting anti-glare properties, the average primary particle diameter of the microparticles is preferably 1 to 8 μm, and more preferably 2 to 5 μm. If the particle diameter is small, the anti-glare properties tend to be insufficient, and if the particle diameter is large, the clarity of the image tends to decrease. The content of the microparticles in the hard coat layer 11 is not particularly limited, but is preferably 1 to 15 parts by weight, more preferably 2 to 10 parts by weight, and even more preferably 3 to 8 parts by weight, relative to 100 parts by weight of the binder resin.

The hard coat layer 11 may contain either nanoparticles or microparticles, or may contain both. It may also contain fine particles having a particle size intermediate between nanoparticles and microparticles.

The composition for forming a hard coat layer includes a curable resin, and may include a solvent capable of dissolving the curable resin, if necessary. As described above, the composition for forming a hard coat layer may include fine particles. When the curable resin is a photocurable resin, it is preferable that a photopolymerization initiator is included in the composition. In addition to the above, the composition for forming a hard coat layer may include additives such as a leveling agent, a thixotropic agent, an antistatic agent, an antiblocking agent, a dispersant, a dispersion stabilizer, an antioxidant, an ultraviolet absorber, an antifoaming agent, a thickener, a surfactant, and a lubricant.

A hard coat layer is formed by applying a composition for forming a hard coat layer on a film substrate, and removing the solvent and curing the resin as necessary. Any suitable method such as a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, a fountain coating method, and a comma coating method can be adopted as a method for applying the composition for forming a hard coat layer. The heating temperature after application may be set to an appropriate temperature depending on the composition of the composition for forming a hard coat layer, and is, for example, about 50°C to 150°C. When the binder resin component is a photocurable resin, photocuring is performed by irradiating it with active energy rays such as ultraviolet rays. The integrated light amount of the irradiated light is preferably about 100 to 500 mJ/ ^cm2 .

The thickness of the hard coat layer 11 is not particularly limited, but from the viewpoint of achieving high hardness and appropriately controlling the surface shape, it is preferably about 1 to 30 μm, and may be 2 to 20 μm or 3 to 10 μm.

<Primer layer>
A primer layer 3 is formed on the transparent film substrate 1 (on the hard coat layer 11), and an antireflection layer 5 is formed thereon. The primer layer 3 is a conductive oxide layer. By providing the primer layer 3 in contact with the hard coat layer 11 and providing the antireflection layer 5 in contact with the primer layer 3, the adhesion between the layers is increased, and an antireflection film in which the antireflection layer is less likely to peel off is obtained. In addition, since the primer layer 3 is a conductive oxide, antistatic properties are imparted to the antireflection film.

From the viewpoints of imparting appropriate antistatic properties to the antireflection film and enabling appropriate detection by the touch sensor of the image display device, the surface resistance R ₀ of the primer layer 3 is preferably 1×10 ⁸ to 5×10 ¹¹ Ω/sq, more preferably 1×10 ⁹ to 1×10 ¹¹ Ω/sq, and even more preferably 5×10 ⁹ to 8×10 ¹⁰ Ω/sq.

Conductive oxides constituting the primer layer 3 include indium oxide, tin oxide, zinc oxide, etc. The metal oxide layer may be a composite oxide. The primer layer preferably contains an oxide of one or more metals selected from the group consisting of In and Sn, as it has high transparency, and preferably contains indium oxide, as it has high transparency and excellent optical stability.

Conductive oxides containing indium oxide include indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO). Of these, ITO is preferred because it is highly transparent and has excellent adhesion and conductivity. The amount of indium oxide in ITO is preferably 40 to 97% by weight, and the amount of tin oxide is preferably 3 to 60% by weight.

The thickness of the primer layer 3 is, for example, about 0.5 to 10 nm, and preferably 1 to 8 nm. The thickness of the primer layer may be 6 nm or less, 5 nm or less, or 4 nm or less. If the thickness of the primer layer is within the above range, it is possible to improve the adhesion between the transparent film substrate 1 and the anti-reflection layer 5, and it is also possible to control the surface resistance within an appropriate range.

It is preferable that the primer layer 3 has a small change in resistance due to ultraviolet light irradiation. When a conductive primer layer such as ITO is irradiated with ultraviolet light, the resistance may decrease (the conductivity may increase). If the resistance of the primer layer of the anti-reflection film decreases, detection abnormalities may occur in the touch sensor section.

The surface resistance _R1 of the primer layer 3 after the antireflection film is irradiated with ultraviolet light at a radiation intensity of 1.6 W/ ^m2 from the side on which the antireflection layer 5 is formed for 1 minute is preferably 0.01 times or more the surface resistance _R0 of the primer layer 3 before the ultraviolet light irradiation. In other words, it is preferable that _R0 / _R1 is 100 or less.

R ₀ /R ₁ is preferably 50 or less, and may be 30 or less, 10 or less, 7 or less, or 5 or less. When R ₀ /R ₁ is small and close to 1, detection abnormalities in the touch sensor under external light (under ultraviolet light such as sunlight) are suppressed. The lower limit of R ₀ /R ₁ is not particularly limited, but is generally 0.1 or more, and may be 0.5 or more, 1 or more, 1.5 or more, or 2 or more.

The surface resistance _R1 of the primer layer 3 after the antireflection film is irradiated with ultraviolet light at a radiation intensity of 1.6 W/ ^m2 from the side on which the antireflection layer 5 is formed for 1 minute is preferably 7× ¹⁰⁷ Ω/sq or more, more preferably 1× ¹⁰⁸ Ω/sq or more, and may be 5× ¹⁰⁸ Ω/sq or more or 1× ¹⁰⁹ Ω/sq or more. _R1 is preferably 5× ¹⁰¹¹ Ω/sq or less, more preferably 1× ¹⁰¹¹ Ω/sq or less, even more preferably 8× ¹⁰¹⁰ Ω/sq or less, and may be 5× ¹⁰¹⁰ Ω/sq or less or 1× ¹⁰¹⁰ Ω/sq or less.

The carrier mobility of the primer layer 3 is preferably 13.5 cm ² /V·s or less, more preferably 13 cm ² /V·s or less, further preferably 12.5 cm ² /V·s or less, and may be 12 cm ² /V·s or less, 11.5 cm ² /V·s or less, 11 cm ² /V·s or less, 10.5 cm ² /V·s or less, or 10 cm ² /V·s or less.

Carrier mobility is measured by the Van der Pauw method using a sample in which a primer layer is formed on a transparent film substrate. Note that, since it is difficult to accurately measure carrier mobility when the thickness of the primer layer is 5 nm or less, carrier mobility is measured by the Van der Pauw method using a sample in which a conductive oxide layer with a thickness of more than 5 nm is formed under the same conditions as for forming the primer layer.

The smaller the carrier mobility of the primer layer 3, the smaller the resistance change rate _R0 / _R1 upon ultraviolet irradiation, and the more likely it is that detection anomalies in the touch sensor section are suppressed. One of the presumed factors that may explain why the resistance change rate upon ultraviolet irradiation is smaller as the carrier mobility is lower is that the effect of carrier excitation due to ultraviolet irradiation is less likely to occur.

The conductivity of a material (the inverse of resistivity) is proportional to the product of the carrier density and carrier mobility in the material; the greater the carrier density and carrier mobility, the smaller the resistance. It is believed that the decrease in resistance is caused by ultraviolet irradiation exciting the carriers in the conductive oxide that makes up the primer layer, increasing the carrier density and carrier mobility. When the carrier mobility of the primer layer is small, carrier scattering is likely to occur, so carriers excited by ultraviolet rays are likely to disappear, and changes (increases) in the effective carrier density and carrier mobility are unlikely to occur, and therefore the rate of resistance change when exposed to ultraviolet rays is small (resistance is unlikely to decrease).

When the primer layer 3 is an indium tin oxide (ITO) layer, the higher the ratio of tin oxide, the lower the carrier mobility tends to be. In ITO, carriers are generated by replacing In in indium oxide with Sn, but excess Sn does not act as an effective conductive carrier and causes carrier scattering. Therefore, it is thought that the higher the ratio of Sn, the lower the carrier mobility.

From the viewpoint of reducing carrier mobility, the amount of tin oxide relative to the total of indium oxide and tin oxide is preferably 3% by weight or more, more preferably 5% by weight or more, even more preferably 10% by weight or more, and may be 15% by weight or more or 20% by weight or more. On the other hand, from the viewpoint of imparting appropriate conductivity to the primer layer and ensuring transparency, the amount of tin oxide relative to the total of indium oxide and tin oxide is preferably 60% by weight or less, more preferably 50% by weight or less, and may be 40% by weight or less or 30% by weight or less.

Carrier mobility is affected not only by the composition of the metal oxide but also by its oxidation state, and excess oxygen tends to increase carrier mobility. The presence of excess oxygen in a metal oxide can be confirmed by X-ray photoelectron spectroscopy (XPS) spectra.

In the case of indium oxide-based metal oxides such as ITO, the peak top of a normal complete oxide (In ₂ O ₃ and SnO ₂ ) appears at about 530 eV in the XPS C1s spectrum. Note that the bond energy here is a value corrected by shifting the position of the peak top derived from the C-C bond in the C1s spectrum to 285 eV.

In a normal complete oxide, the peak intensity I ₅₃₂ at 532 eV in the C1s spectrum is in the range of 0.80 to 0.90 times the peak intensity I ₅₃₀ at 530 eV (peak top). If the amount of oxygen is increased when forming an ITO film, a shoulder appears in the vicinity of 531 to 533 eV, and the ratio I ₅₃₂ /I ₅₃₀ of the peak intensity I ₅₃₂ at 532 eV to the peak intensity I 530 at ₅₃₀ eV increases.

When the primer layer 3 is an ITO layer, the peak intensity I ₅₃₂ at 532 eV in the C1s spectrum is preferably 0.93 times or less the peak intensity I ₅₃₀ at 530 eV. I ₅₃₂ /I ₅₃₀ is more preferably 0.92 or less, further preferably 0.91 or less, and may be 0.90 or less.

<Anti-reflection layer>
The antireflection layer 5 is a laminate of multiple thin films with different refractive indices. In general, the optical film thickness (product of refractive index and thickness) of the thin films of the antireflection layer is adjusted so that the inverted phases of incident light and reflected light cancel each other out. The multi-layer laminate of multiple thin films with different refractive indices can reduce the reflectance in a wide wavelength range of visible light. The thin films constituting the antireflection layer 5 are preferably made of inorganic materials, and ceramic materials made of metal or semimetal oxides, nitrides, fluorides, etc. are preferred, and among them, metal or semimetal oxides (inorganic oxides) are preferred.

The anti-reflection layer 5 is preferably an alternating laminate of high-refractive index layers and low-refractive index layers. In order to reduce reflection at the air interface, the thin film 54 provided as the outermost layer of the anti-reflection layer 5 (the layer farthest from the transparent film substrate 1) is preferably a low-refractive index layer.

The high refractive index layers 51 and 53 have a refractive index of, for example, 1.9 or more, preferably 2.0 or more. Examples of high refractive index materials include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, indium tin oxide (ITO), antimony-doped tin oxide (ATO), and the like. Among these, titanium oxide or niobium oxide is preferred. The low refractive index layers 52 and 54 have a refractive index of, for example, 1.6 or less, preferably 1.5 or less. Examples of low refractive index materials include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, lanthanum fluoride, and the like. Among these, silicon oxide is preferred. In particular, it is preferred to alternately stack niobium oxide (Nb ₂ O ₅ ) thin films 51 and 53 as high refractive index layers and silicon oxide (SiO ₂ ) thin films 52 and 54 as low refractive index layers. In addition to the low refractive index layer and the high refractive index layer, a medium refractive index layer having a refractive index of about 1.6 to 1.9 may be provided.

The thickness of each of the high and low refractive index layers is about 5 to 200 nm, and preferably about 15 to 150 nm. The thickness of each layer may be designed so that the reflectance of visible light is small, depending on the refractive index and the layered structure. For example, the layered structure of the high and low refractive index layers may be a four-layer structure consisting of a high refractive index layer 51 with an optical thickness of about 25 to 55 nm, a low refractive index layer 52 with an optical thickness of about 35 to 55 nm, a high refractive index layer 53 with an optical thickness of about 80 to 240 nm, and a low refractive index layer 54 with an optical thickness of about 120 to 150 nm, from the transparent film substrate 1 side. The anti-reflection layer is not limited to a four-layer structure, and may be a two-layer structure, a three-layer structure, a five-layer structure, or a six-layer or more layer structure.

<Formation of primer layer and anti-reflection layer>
An anti-reflection film is formed by forming a primer layer 3 and an anti-reflection layer 5 on a transparent film substrate 1. When the transparent film substrate 1 is a hard coat film having a hard coat layer 11 on the surface of a transparent resin film 10, the primer layer 3 and the anti-reflection layer 5 are formed in this order on the hard coat layer 11.

Before forming the primer layer and the anti-reflection layer, the film substrate 1 may be subjected to a surface treatment. Examples of the surface treatment include surface modification treatments such as corona treatment, plasma treatment, frame treatment, ozone treatment, primer treatment, glow treatment, alkali treatment, acid treatment, and treatment with a coupling agent. Vacuum plasma treatment may be performed as the surface treatment. The surface roughness of the hard coat layer can also be adjusted by the surface treatment. For example, when forming a primer layer 3 on a hard coat layer 11 containing fine particles, if a plasma treatment is performed on the surface of the hard coat layer 11 with high discharge power, the resin component is etched and the fine particles are exposed to the surface, which tends to increase the surface unevenness of the hard coat layer surface and improve adhesion to the thin film.

The method of forming the thin films constituting the primer layer 3 and the anti-reflection layer 5 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, sputtering, and electron beam vapor deposition are preferred because they can form thin films with a uniform thickness. Among these, sputtering is preferred because it has excellent uniformity in thickness and is easy to form dense films.

In the sputtering method, a thin film can be continuously formed while the film substrate is transported in one direction (longitudinal direction) using a roll-to-roll method. This improves the productivity of anti-reflective films that have a primer layer 3 and an anti-reflective layer 5 made of multiple thin films on a transparent film substrate 1.

In the sputtering method, deposition is performed while introducing an inert gas such as argon, and if necessary, a reactive gas such as oxygen, into the chamber. Deposition of an oxide layer by sputtering can be performed either by using an oxide target or by reactive sputtering using a (semi)metallic target.

The thin film constituting the anti-reflection layer 5 is preferably formed by reactive sputtering using a metal or semi-metal target, since it allows for the deposition of an inorganic oxide film at a high rate. The sputtering power source used for reactive sputtering is preferably DC or MF-AC.

In reactive sputtering, deposition is performed while introducing an inert gas such as argon and a reactive gas such as oxygen into the chamber. In reactive sputtering, it is preferable to adjust the amount of oxygen so that the transition region is between the metal region and the oxide region. By adjusting the amount of oxygen so that the sputter deposition is in the transition region, an oxide film can be deposited at a high rate.

It is preferable to use an oxide target for depositing the primer layer. Reactive sputtering using a metal target has the advantage of high deposition speed, but slight changes in deposition conditions (deposition environment) can cause significant changes in film quality. On the other hand, the use of an oxide target stabilizes the film quality of the primer layer. When depositing an ITO layer as the primer layer 3, it is preferable to use a mixed oxide target containing indium oxide and tin oxide.

The substrate temperature when sputtering the primer layer is about -30 to 150°C, and is not particularly limited as long as the transparent film substrate is durable. The pressure and power density when sputtering the primer layer can be set appropriately depending on the type of target and the thickness of the primer layer.

When forming a primer layer by sputtering using an oxide target, an oxidizing gas such as oxygen may be introduced in addition to an inert gas such as argon. By introducing oxygen, the oxygen that is desorbed from the target during sputtering is compensated for, making it easier to form a conductive oxide with a stoichiometric composition, which tends to improve transparency.

On the other hand, if the amount of oxygen introduced during sputtering is excessively large, the presence of excess oxygen increases the carrier mobility of the primer layer, and the resistance change rate during ultraviolet irradiation tends to increase. The amount of oxygen introduced during sputtering is preferably 5 parts by volume or less, more preferably 3 parts by volume or less, more preferably 2 parts by volume or less, and even more preferably 1 part by volume or less, and may be 0.5 parts by volume or less, 0.3 parts by volume or less, or 0.1 parts by volume or less, relative to 100 parts by volume of inert gas. The primer layer may be formed while introducing only inert gas without introducing oxygen. If an oxide target is used, there is only a small amount of oxygen deficiency even when no oxygen is introduced at all, and a significant decrease in transparency can be avoided.

The smaller the amount of oxygen introduced during sputtering deposition, the smaller the carrier mobility of the primer layer 3 tends to be. Furthermore, when the primer layer 3 is an ITO layer, the smaller the amount of oxygen introduced during sputtering deposition, the smaller the ratio I ₅₃₂ /I ₅₃₀ of the peak intensity I ₅₃₂ eV to the peak intensity I 530 at _{530 eV} tends to be.

As mentioned above, when the primer layer 3 is an ITO layer, the higher the ratio of tin oxide, the smaller the carrier mobility tends to be. The higher the ratio of tin oxide in the target used to form the ITO layer and the smaller the amount of oxygen introduced during film formation, the smaller the carrier mobility of the ITO primer layer and the smaller the change in resistivity when irradiated with ultraviolet light tends to be.

<Anti-stain layer>
The antireflection film may have an additional functional layer on the antireflection layer 5. When the antireflection film is disposed on the outermost surface of an image display device equipped with a touch sensor, it is preferable to provide an antifouling layer 7 on the antireflection layer 5 for the purposes of preventing adhesion of contaminants such as fingerprints and dirt caused by touch operations and facilitating removal of the adhered contaminants.

When the anti-smudge layer 7 is provided on the surface of the anti-reflection film, it is preferable that the difference in refractive index between the low refractive index layer 54 on the outermost surface of the anti-reflection layer 5 and the anti-smudge layer 7 is small from the viewpoint of reducing reflection at the interface. The refractive index of the anti-smudge layer is preferably 1.6 or less, more preferably 1.55 or less. As the material for the anti-smudge layer, a fluorine group-containing silane-based compound, a fluorine group-containing organic compound, or the like is preferable. The anti-smudge layer can be formed by a wet method such as a reverse coating method, a die coating method, or a gravure coating method, or a dry method such as a vacuum deposition method or a CVD method. The thickness of the anti-smudge layer is usually about 1 to 100 nm, preferably 2 to 50 nm, and more preferably 3 to 30 nm.

[Image display device]
The anti-reflection film is used by being disposed on the surface of an image display device. By disposing the anti-reflection film on the viewing side surface of an image display panel including an image display medium (image display section), the reflection of external light can be reduced and the visibility of the image display device can be improved.

In the image display device 201 shown in FIG. 2, an anti-reflection film 101 is attached to the viewing side surface of an image display panel 8 having a touch sensor unit 85 on an image display unit 81 via an adhesive layer 2.

The adhesive layer 2 is composed of, for example, an acrylic adhesive, a rubber adhesive, a silicone adhesive, or the like. The thickness of the adhesive layer 2 is not particularly limited, and is, for example, about 1 to 100 μm. The image display panel 8 and the anti-reflection film 101 may be bonded together via a curing adhesive. The anti-reflection film 101 does not necessarily have to be bonded to the image display panel 8, and the anti-reflection film may be disposed on the image display panel with a space therebetween.

The image display unit 8 is an image display cell such as a liquid crystal cell or an organic EL cell. The image display unit 8 may include an optical film such as a polarizing plate on the surface of the image display cell.

The touch sensor unit 85 is, for example, a capacitive touch panel, and is equipped with electrodes for position detection. A capacitive touch panel detects the touch position by detecting a change in the capacitance of the electrodes when a finger or a touch pen touches the touch surface (the visible surface of the image display device 201).

In FIG. 2, an on-cell type touch panel is shown in which the touch sensor unit 85 is disposed on the viewing side surface of the image display unit 81, but the touch panel may be an in-cell type in which the touch sensor is provided inside the image display cell. Also, the touch panel may be disposed separately from the image display cell.

In the image display device 201, the antireflection film 101 arranged on the viewing side surface of the touch sensor unit 85 has a conductive primer layer 3, and therefore has antistatic properties and can prevent malfunction of the touch sensor caused by static electricity. In addition, since the primer layer 3 has a small resistance change rate _R0 / _R1 when irradiated with ultraviolet light, even when the image display device is used outdoors, the resistance change of the primer layer is small and detection abnormalities are unlikely to occur.

The anti-reflection film 101 is flexible and bendable because a transparent resin film is used as the substrate material for forming the primer layer 3 and the anti-reflection layer 5. Therefore, the anti-reflection film can also be used as a surface plate (cover window) of an image display device having a curved display or a foldable display.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following specific examples.

[Comparative Example 1]
(Preparation of hard coat film)
A hard coat composition having a solid content of 40% by weight was prepared by mixing 100 parts by weight of an ultraviolet-curable acrylic hard coat agent containing silica particles having an average particle size of 50 nm or less (Aica Industrial Co., Ltd. "Aica Itron Z-850-50H-D", solid content concentration 44% by weight), 4 parts by weight of a photopolymerization initiator (BASF "OMNIRAD 2959"), and 0.05 parts by weight of a leveling agent (Kyoeisha Chemical Co., Ltd. "LE-303") and diluting with methyl isobutyl ketone. The above hard coat composition was applied to one side of a 50 μm-thick PET film (Toray Co., Ltd. "Lumirror U48") so that the thickness after drying was 5 μm, and the coating was dried by heating at 80° C. for 1 minute. Thereafter, the composition was cured by irradiating it with ultraviolet light using a high-pressure mercury lamp so that the integrated light amount at a wavelength of 365 nm was 300 mJ/cm ² , thereby producing a hard coat film having a hard coat layer on the PET foil.

(Plasma Treatment)
While the hard coat film was being transported in a roll-to-roll type plasma treatment device, the surface of the hard coat layer was subjected to argon plasma treatment under a vacuum atmosphere of 1.0 Pa with a discharge power of 150 W.

(Formation of primer layer and anti-reflection layer)
The hard coat film after the plasma treatment was introduced into a roll-to-roll sputtering deposition apparatus, and the pressure inside the chamber was reduced to 1×10 ⁻⁴ Pa. While the film was being run, a 1.5 nm ITO primer layer, a 12 nm Nb ₂ O _5- layer (first high refractive index layer), a 28 nm SiO _2- layer (first low refractive index layer), a 100 nm Nb ₂ O _5- layer (second high refractive index layer) and an 85 nm SiO _2- layer (second low refractive index layer) were sequentially deposited on the hard coat layer-forming surface at a substrate temperature of −8° C.

To form the ITO primer layer, an oxide target containing indium oxide and tin oxide in a weight ratio of 96.7:3.3 was used, and MF-AC sputtering was performed under conditions of a pressure of 0.2 Pa and a discharge voltage of 400 V while introducing 0.4 parts by volume of oxygen per 100 parts by volume of argon.

An Nb target was used to form the Nb ₂ O ₅ layer (high refractive index layer), and an Si target was used to form the SiO ₂ layer (low refractive index layer), and MF-AC sputtering was performed at a pressure of 0.7 Pa. In the formation of the first high refractive index layer, 5 parts by volume of oxygen was introduced to 100 parts by volume of argon, and the discharge voltage was set to 415 V. In the formation of the first low refractive index layer, 30 parts by volume of oxygen was introduced to 100 parts by volume of argon, and the discharge voltage was set to 350 V. In the formation of the second high refractive index layer, 13 parts by volume of oxygen was introduced to 100 parts by volume of argon, and the discharge voltage was set to 460 V. In the formation of the second low refractive index layer, 30 parts by volume of oxygen was introduced to 100 parts by volume of argon, and the discharge voltage was set to 340 V.

(Formation of antifouling layer)
A fluorine-based antifouling coating agent (KY1903-1 manufactured by Shin-Etsu Chemical Co., Ltd.) was dried and solidified and used as a deposition source to form an antifouling layer having a thickness of 12 nm on the antireflection layer by vacuum deposition.

As a result of the above, an anti-reflection film was obtained that had, in order, a 1.5 nm thick ITO primer layer, an anti-reflection layer consisting of a total of four layers, and an anti-fouling layer with a thickness of 12 nm on the hard coat layer of the hard coat film.

[Reference Example 1]
In Comparative Example 1, the process was carried out up to the formation of the ITO primer layer, and a film was produced having an ITO primer layer having a thickness of 1.5 nm on the hard coat layer of the hard coat film without forming an antireflection layer and an antifouling layer.

[Examples 1 and 2]
The target used to form the ITO primer layer in Comparative Example 1 was changed, and a target with a tin oxide content of 10% by weight was used in Example 1, and a target with a tin oxide content of 30% by weight was used in Example 2. Otherwise, in the same manner as in Comparative Example 1, an antireflection film was produced which was provided, in order, on the hard coat layer of the hard coat film, with a 1.5 nm-thick ITO primer layer, an antireflection layer consisting of a total of four layers, and an antifouling layer with a thickness of 12 nm.

[Reference Examples 2 to 10]
In the formation of the ITO primer layer in Reference Example 1, the target composition (tin oxide content) and the amount of oxygen introduced during sputtering were changed as shown in Table 2. Otherwise, a film having an ITO layer having a thickness of 1.5 nm on the hard coat layer of the hard coat film was produced in the same manner as in Reference Example 1.

[Reference Examples 1a, 2a, 4a, 5a, 7a, 8a, 9a, 10a]
A film (sample for measuring carrier mobility) having an ITO layer on the hard coat layer of the hard coat film was prepared in the same manner as in Reference Examples 1, 2, 4, 5, 7, 8, 9, and 10, except that the thickness of the ITO primer layer was changed as shown in Table 1. The deposition conditions of the ITO layer (tin content of the target, oxygen flow rate per 100 parts by volume of argon) and the thickness of the ITO layer in these Reference Examples are shown in Table 1.

[evaluation]
<XPS analysis of ITO primer layer>
The samples of Reference Examples 1, 2, 4 to 6, and 8 to 10 were cut into a size of 1 cm x 1 cm and fixed on the sample stage of a scanning X-ray photoelectron spectroscopy (XPS) device (ULVAC-PHI's "Quantera SXM"). Etching was performed with Ar gas cluster ions (Ar _n ⁺ ) at an acceleration voltage of 10 kV (etching area: 2 mm x 2 mm) to clean the surface. Then, XPS measurement (narrow scan) of the ITO primer layer was performed under the following conditions.
X-ray source: Monochrome AlKα
X-ray beam diameter: 100 μmφ
X-ray output: 25W (15kV)
Photoelectron take-off angle: 5° to the sample surface
Neutralization conditions: Use of neutralization gun and Ar ion gun (neutralization mode)

In the narrow-scan C1s spectrum, the spectral intensity I ₅₃₀ at 530 eV and the spectral intensity I ₅₃₂ at 532 eV were read, and the intensity ratio I ₅₃₂ /I ₅₃₀ between them was calculated. The bond energy was corrected by shifting the position of the peak top derived from the C-C bond in the C1s spectrum to 285 eV.

<Carrier Density and Carrier Mobility of ITO Layer>
Using a Hall effect measurement system (Toyo Corporation's "ResiTest 8308", AC power supply), the carrier density n and carrier mobility μ of the ITO layer of the samples prepared in Reference Examples 1a, 2a, 4a, 5a, 7a, 8a, 9a, and 10a were measured by the Van der Pauw method.

<Surface resistance>
Using a resistivity meter (TREK's "152-1"), the surface resistance _R0 of the antifouling layer surface of the antireflection films of Examples 1 and 2 and Comparative Example 1, and the surface of the ITO layer surface of the films of Reference Examples 1 to 10 were measured. Then, using a xenon weather meter (ATLAS's "Ci4000"), ultraviolet rays were irradiated for 1 minute at a radiation intensity of 1.6 W/ ^m2 in an environment of a temperature of 25°C and a relative humidity of 25%. Within 30 seconds after the ultraviolet irradiation, the surface resistance was measured again and recorded as the surface resistance _R1 after the ultraviolet irradiation.

<Touch operability after UV irradiation>
The PET film side of the anti-reflection films of the Examples and Comparative Examples and the ITO-attached film of the Reference Example were attached to the screen of an Apple iPad Air via an adhesive layer. The samples were irradiated with ultraviolet light for 1 minute using a handheld black light (SV003, manufactured by Alonefire, radiation intensity 10 W, wavelength 365 nm), and then the surface of the film was touched to evaluate the touch operability according to the following criteria.
◯: Touch operations can be performed smoothly, just as before UV irradiation △: Touch operations are detected, but cannot be performed smoothly ×: Touch operations are not detected and operations cannot be performed

The deposition conditions (tin content of the target, oxygen flow rate per 100 parts by volume of argon) and the evaluation results of the primer layers in the Examples, Comparative Examples, and Reference Examples are shown in Table 2. Note that the surface resistances Ro and _R1 in Comparative Example 1, Example 1, and Example 2 are the surface resistances of antireflection films having an antireflection layer and an antifouling layer on a primer layer, and are listed as reference values since they are not directly measured surface resistances of the primer layer.

The film of Reference Example 1, in which the carrier mobility of the ITO primer layer was 13.7 cm ² /V·s, had an R ₀ /R ₁ of 1000, and the surface resistance was reduced to 1/1000 by ultraviolet irradiation. After the film of Reference Example 1 was placed on the surface of a touch panel and irradiated with ultraviolet light, a detection abnormality occurred and touch operation was not possible.

In Reference Examples 4 and 7, in which the carrier mobility of the ITO primer layer was higher than that of Reference Example 1, detection abnormalities of the touch sensor occurred after ultraviolet light irradiation, similar to Reference Example 1. In Reference Examples 4 and 7, _R0 / _R1 was larger than that of Reference Example 1 (the rate of change in surface resistance due to ultraviolet light irradiation was larger), and there was a tendency that the larger the carrier mobility, the larger _R0 / _R1 became.

The anti-reflective film of Comparative Example 1, which had an anti-reflective layer and an anti-fouling layer on the ITO primer layer of the film of Reference Example 1, showed detection abnormalities in the touch sensor after irradiation with ultraviolet light, similar to Reference Example 1.

The film of Reference Example 5, in which the carrier mobility of the ITO primer layer was 12.0 cm ² /V·s, had an R ₀ /R ₁ of 50, and was able to be touched normally even after being irradiated with ultraviolet light while placed on the surface of a touch panel. The antireflection film of Example 1, in which an antireflection layer and an antifouling layer were provided on the ITO primer layer of the film of Reference Example 5, was able to be touched normally even after being irradiated with ultraviolet light, similar to Reference Example 5.

The film of Reference Example 8, in which the carrier mobility of the ITO primer layer was 10.3 cm ² /V·s, and the antireflection film of Example 2, in which an antireflection layer and an antifouling layer were provided on the ITO layer, were able to be touched normally even after exposure to ultraviolet light, as in Reference Examples 5 and 1.

In Reference Examples 6, 9, and 10, in which R ₀ /R ₁ was small (the rate of change in surface resistance due to ultraviolet irradiation was small), normal touch operation was possible even after ultraviolet irradiation, similar to Reference Examples 5 and 8.

These results show that, regardless of the presence or absence of an anti-reflection layer (and an anti-fouling layer), the decrease in resistance of the ITO primer layer due to UV irradiation is the cause of the touch sensor detection abnormality, and that when the carrier mobility of the ITO primer layer is small, the change in resistance of the ITO primer layer due to UV irradiation is small and no detection abnormality occurs in the touch sensor.

A comparison between Reference Example 2 and Reference Example 6, and a comparison between Reference Example 3 and Reference Example 7 shows that the greater the tin oxide content in the ITO primer layer (the tin oxide content in the target used for film formation), the smaller the R ₀ /R ₁ tends to be. Also, a comparison between Reference Examples 1, 5, and 8 to 10 shows that the greater the tin oxide content in the ITO primer layer, the smaller the carrier mobility of the ITO primer layer and the smaller the R ₀ /R ₁ tends to be.

Comparisons between Reference Example 1 and Reference Example 2, between Reference Examples 3 to 6, and between Reference Example 7 and Reference Example 8 showed that the smaller the amount of oxygen introduced during the formation of the ITO primer layer, the smaller the carrier mobility and the smaller the _R0 / _R1 tended to be. Comparisons between Reference Examples 1, 3, 5, 6, and 8 showed that the larger the tin oxide content of the ITO primer layer and the smaller the amount of oxygen introduced during the formation of the ITO primer layer, the smaller the peak intensity ratio _I532 / _I530 in the XPS C1s spectrum and the smaller the _R0 / _R1 tended to be.

These results show that increasing the tin oxide content in the ITO primer layer and/or increasing the amount of oxygen introduced during deposition of the ITO primer layer tends to reduce carrier mobility, and that when the carrier mobility in the primer layer is low, the rate of change in resistance of the primer layer due to exposure to ultraviolet light is small, making it possible to prevent detection abnormalities in the touch sensor.

In Comparative Example 1 and Reference Examples 1, 4, and 7, detection abnormalities occurred in the touch sensor immediately after ultraviolet light irradiation, but normal touch operation was possible when a touch operation was performed one hour after ultraviolet light irradiation. It is believed that the resistance change due to ultraviolet light irradiation and the resulting detection abnormality in the touch sensor occur temporarily immediately after ultraviolet light irradiation.

1. Transparent film substrate (hard coat film)
REFERENCE SIGNS LIST 10 Transparent resin film 11 Hard coat layer 3 Primer layer 5 Anti-reflection layer 51, 53 High refractive index layer 52, 54 Low refractive index layer 7 Anti-soiling layer 101 Anti-reflection film 2 Pressure-sensitive adhesive layer 81 Image display section 85 Touch sensor section 8 Image display panel 201 Image display device

Claims (13)

An antireflection film comprising a primer layer and an antireflection layer on one main surface of a transparent film substrate,
the antireflection layer is a laminate of a plurality of thin films having different refractive indices;
the primer layer is a conductive metal oxide layer having a thickness of 0.5 to 10 nm and a carrier mobility of 13.5 cm ² /V·s or less;
Anti-reflective film. 2. The anti-reflection film according to claim 1, wherein the surface resistance R ₀ of the primer layer is 1×10 ⁸ to 5×10 ¹¹ Ω/sq. 3. The anti-reflection film according to claim 2, wherein the ratio R ₀ /R ₁ of the surface resistance R ₁ of the primer layer after being irradiated with ultraviolet light at a radiation intensity of 1.6 W/m ² for 1 minute to the surface resistance R ₀ of the primer layer before being irradiated with ultraviolet light is 100 or less. An antireflection film comprising a primer layer and an antireflection layer on one main surface of a transparent film substrate,
the antireflection layer is a laminate of a plurality of thin films having different refractive indices;
the primer layer is a conductive metal oxide layer, has a thickness of 0.5 to 10 nm, and has a surface resistance R ₀ of 1×10 ⁸ to 5×10 ¹¹ Ω/sq;
An antireflection film, wherein the ratio R ₀ /R ₁ of the surface resistance R ₁ of the primer layer after being irradiated with ultraviolet light at a radiation intensity of 1.6 W/m ² for 1 minute to the surface resistance R ₀ of the primer layer before being irradiated with ultraviolet light is 100 or less. The anti-reflection film according to any one of claims 1 to 4, wherein the primer layer is an indium tin oxide layer. The anti-reflection film according to claim 5, wherein the primer layer contains 3 to 60% by weight of tin oxide relative to the total of indium oxide and tin oxide. The anti-reflection film according to claim 5, wherein the primer layer has a peak intensity at 532 eV of 0.93 times or less than the peak intensity at 530 eV in the C1s spectrum of X-ray photoelectron spectroscopy. The anti-reflection film according to any one of claims 1 to 4, further comprising an anti-glare layer on the anti-reflection layer. The transparent film substrate has a hard coat layer on one main surface of a transparent resin film,
The antireflection film according to any one of claims 1 to 4, wherein the hard coat layer and the primer layer are in contact with each other. The anti-reflection film according to claim 9, wherein the hard coat layer contains a cured product of a curable resin and fine particles. An image display device comprising an image display unit, a touch sensor unit, and an anti-reflection film disposed on a viewing side surface of the touch sensor unit, the image display device being capable of detecting a position by the touch sensor,
The anti-reflection film is the anti-reflection film according to any one of claims 1 to 4.
Image display device. A method for producing the anti-reflection film according to any one of claims 1 to 4, comprising the steps of:
A method for producing an anti-reflective film, comprising forming a primer layer on one main surface of a transparent film substrate by sputtering using an oxide target. The method for producing an antireflection film according to claim 12, wherein an antireflection layer is formed on the primer layer by reactive sputtering.

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