JP7509852B2 - Transparent Conductive Film - Google Patents

Description

The present invention relates to a transparent conductive film.

Conventionally, transparent conductive films have been known that include a transparent resin substrate film and a transparent conductive layer (transparent conductive layer) in that order in the thickness direction. The transparent conductive layer is used as a conductive film for forming transparent electrodes in various devices such as liquid crystal displays, touch panels, and solar cells. The transparent conductive layer is formed, for example, by sputtering a conductive oxide onto a long substrate film in a roll-to-roll method (sputtering film formation process). The conductive oxide film is formed in a film formation chamber of a sputtering film formation device. Technology related to such transparent conductive films is described, for example, in Patent Document 1 below.

JP 2017-71850 A

The transparent conductive layer of a transparent conductive film is required to have low resistance. This requirement is particularly strong for transparent conductive films used in transparent electrodes. The transparent conductive layer of a transparent conductive film is also required to be resistant to cracking when the film is bent. This requirement is particularly strong for transparent conductive films used in flexible devices.

In addition, transparent conductive films may be exposed to relatively high-temperature heating processes during the manufacturing process of devices that include the film. The transparent conductive layer of such transparent conductive films is required to have little or no increase in resistance due to subsequent heating.

However, in a transparent conductive layer that contains a mixture of amorphous regions and crystalline grains, if the moisture content in the transparent conductive layer is too low, subsequent heating will significantly increase the resistance value. This is the finding of the inventors.

The present invention provides a transparent conductive film that is suitable for reducing the resistance of a transparent conductive layer while suppressing cracking when bent and an increase in resistance value due to heating.

The present invention [1] includes a transparent conductive film comprising a transparent substrate and a transparent conductive layer in this order in a thickness direction, the transparent conductive layer including amorphous regions and crystal grains, and the transparent conductive layer including 2.0× ¹⁰ cm ⁻³ or more of hydrogen atoms.

The present invention [2] includes the transparent conductive film according to the above [1], wherein the transparent conductive layer has a resistivity of 4.0×10 ⁻⁴ Ω·cm or more.

The present invention [3] includes the transparent conductive film described in [1] or [2] above, in which the transparent conductive layer contains amorphous regions and crystal grains after heating at 140°C for 30 minutes.

As described above, the transparent conductive film of the present invention has a transparent conductive layer that includes amorphous regions and crystal grains. The transparent conductive layer includes amorphous regions and crystal grains, which is suitable for achieving both low resistance and suppression of cracking during bending in the transparent conductive layer (amorphous transparent conductive layers have high resistance, while crystalline transparent conductive layers are prone to cracking). In addition, the transparent conductive film has a hydrogen atom content of 2.0×10 ²⁰ cm ⁻³ or more. Such a transparent conductive film is suitable for suppressing an increase in the resistance value of the transparent conductive layer due to subsequent heating. Therefore, the transparent conductive film is suitable for suppressing cracking during bending and an increase in the resistance value due to heating while reducing the resistance of the transparent conductive layer.

1 is a schematic cross-sectional view of one embodiment of a transparent conductive film of the present invention. This illustrates a case where the transparent conductive layer in the transparent conductive film shown in FIG. 1 is patterned. FIG. 2 is a schematic cross-sectional view of a modified example of the transparent conductive film of the present invention. 4 shows a bending test of the transparent conductive films of Examples and Comparative Examples.

The transparent conductive film X, which is one embodiment of the transparent conductive film of the present invention, comprises a transparent substrate 11 and a transparent conductive layer 12 in this order in the thickness direction H. The transparent conductive film X has a sheet shape that spreads in a direction (plane direction) perpendicular to the thickness direction H. The transparent conductive film X is an element that is provided in touch sensor devices, light control elements, photoelectric conversion elements, heat ray control members, antenna members, electromagnetic wave shielding members, heater members, lighting devices, image display devices, and the like.

The transparent substrate 11 is a substrate that ensures the strength of the transparent conductive film X. In this embodiment, the transparent substrate 11 is a transparent resin film having flexibility. Examples of the material of the transparent substrate 11 include polyester resin, polyolefin resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, polyimide resin, cellulose resin, and polystyrene resin. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer. Examples of the acrylic resin include polymethacrylate. As the material of the transparent substrate 11, for example, from the viewpoint of transparency and strength, polyester resin is preferably used, and more preferably PET is used.

The surface of the transparent substrate 11 facing the transparent conductive layer 12 may be subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

From the viewpoint of ensuring the strength of the transparent conductive film X, the thickness of the transparent substrate 11 is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and even more preferably 30 μm or more. From the viewpoint of ensuring the handleability of the transparent substrate 11 in the roll-to-roll method, the thickness of the transparent substrate 11 is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 100 μm or less, even more preferably 80 μm or less, and particularly preferably 75 μm or less.

The total light transmittance (JIS K 7375-2008) of the transparent substrate 11 is preferably 60% or more, more preferably 80% or more, and even more preferably 85% or more. Such a configuration is suitable for ensuring the transparency required of the transparent conductive film X when the transparent conductive film X is provided in a touch sensor device, a light control element, a photoelectric conversion element, a heat ray control member, an antenna member, an electromagnetic wave shielding member, a heater member, a lighting device, an image display device, and the like. The total light transmittance of the transparent substrate 11 is, for example, 100% or less.

The transparent conductive layer 12 is disposed on one side of the transparent substrate 11 in the thickness direction H. In this embodiment, the transparent conductive layer 12 contacts the transparent substrate 11. The transparent conductive layer 12 has both optical transparency and electrical conductivity.

Examples of materials for the transparent conductive layer 12 include conductive oxides. Examples of conductive oxides include indium-containing conductive oxides and antimony-containing conductive oxides. Examples of indium-containing conductive oxides include indium tin composite oxide (ITO), indium zinc composite oxide (IZO), indium gallium composite oxide (IGO), and indium gallium zinc composite oxide (IGZO). Examples of antimony-containing conductive oxides include antimony tin composite oxide (ATO). From the viewpoint of achieving high transparency and good electrical conductivity, indium-containing conductive oxides are preferably used as the conductive oxide, and ITO is more preferably used. This ITO may contain metals or semimetals other than In and Sn in amounts less than the respective contents of In and Sn.

When ITO is used as the conductive oxide, the tin oxide ratio in the transparent conductive layer 12 is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of reducing the resistivity of the transparent conductive layer 12. The tin oxide ratio is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, from the viewpoint of obtaining high reliability of the transparent conductive layer 12 in a humid environment (suppression of resistance value fluctuations such as resistance value increases).

The tin oxide ratio in ITO can be identified, for example, as follows. First, the abundance ratio of indium atoms (In) and tin atoms (Sn) in ITO as a measurement target is obtained by X-ray photoelectron spectroscopy. From the abundance ratios of In and Sn in ITO, the ratio of the number of Sn atoms to the number of In atoms in ITO is obtained. This gives the tin oxide ratio in ITO. The tin oxide ratio in ITO can also be determined from the tin oxide (SnO ₂ ) content of the ITO target used during sputtering film formation.

The transparent conductive layer 12 includes amorphous regions and crystal grains. When a conductive oxide is used as the material of the transparent conductive layer 12, the transparent conductive layer 12 includes amorphous regions and crystal grains of the conductive oxide. The crystal grains are crystal grains with a maximum length of 30 nm or more. The amorphous regions are regions other than the areas where crystal grains with a maximum length of 30 nm or more exist. The transparent conductive layer 12 including amorphous regions and crystal grains is suitable for achieving both low resistance and suppression of cracking when bent in the transparent conductive layer 12 (amorphous transparent conductive layers have high resistance, and crystalline transparent conductive layers are prone to cracking). In addition, the transparent conductive layer 12 preferably includes amorphous regions and crystal grains even after heating at 140°C for 30 minutes. The fact that the transparent conductive layer (the transparent conductive layer 12 on the transparent substrate 11 in the transparent conductive film X) includes amorphous regions and crystal grains can be determined, for example, by observing the transparent conductive layer with a field emission scanning electron microscope (FE-SEM). More specifically, this is described below in the examples.

From the viewpoint of reducing the resistance of the transparent conductive layer 12, the thickness of the transparent conductive layer 12 is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, particularly preferably 50 nm or more, even more preferably 80 nm or more, and particularly preferably 100 nm or more. In addition, from the viewpoint of suppressing cracking due to heating in the transparent conductive layer 12, the thickness of the transparent conductive layer 12 is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less.

The transparent conductive layer 12 contains hydrogen atoms at 2.0×10 ²⁰ cm ^-3 or more. The hydrogen atoms (H) in the transparent conductive layer 12 reflect the presence of water molecules (H ₂ O) in the transparent conductive layer 12. That is, the hydrogen atom content of the transparent conductive layer 12 reflects the water content of the transparent conductive layer 12. A hydrogen atom content of 2.0×10 ²⁰ cm ^-3 or more in the transparent conductive layer 12 is suitable for suppressing an increase in resistance value of the transparent conductive layer 12 due to subsequent heating. Specific examples are as shown in the examples and comparative examples described below. From the viewpoint of suppressing an increase in resistance value due to subsequent heating of the transparent conductive layer 12, the hydrogen atom content of the transparent conductive layer 12 is preferably 4.0×10 ²⁰ cm ^-3 or more, more preferably 7.0×10 ²⁰ cm ^-3 or more, even more preferably 10×10 ²⁰ cm ^-3 or more, and particularly preferably 13×10 ²⁰ cm ^-3 or more. From the viewpoint of obtaining high reliability of the transparent conductive layer 12 in a humid environment, the hydrogen atom content of the transparent conductive layer 12 is preferably 300×10 ²⁰ cm ^-3 or less, more preferably 100×10 ²⁰ cm ^-3 or less, even more preferably 30×10 ²⁰ cm ^-3 or less, especially preferably 20×10 ²⁰ cm ^-3 or less, and particularly preferably 15×10 ²⁰ cm ^-3 or less. The water content (hydrogen atom content) of the transparent conductive layer 12 can be adjusted, for example, by adjusting the water pressure in a sputtering deposition chamber in the transparent conductive layer forming step (sputtering deposition step) described below. The water content (hydrogen atom content) of the transparent conductive layer 12 can be measured, specifically, as described below in the examples.

From the viewpoint of reducing the resistance of the transparent conductive layer 12, the resistivity of the transparent conductive layer 12 is, for example, 6.5×10 ⁻⁴ Ω·cm or less, preferably 5.5×10 ⁻⁴ Ω·cm or less, more preferably 5.0×10 ⁻⁴ Ω·cm or less, and even more preferably 4.5×10 ⁻⁴ Ω·cm or less. From the viewpoint of suppressing cracks in the transparent conductive layer 12 when it is bent, the resistivity of the transparent conductive layer 12 is preferably 4.0×10 ⁻⁴ Ω·cm or more. The resistivity is calculated by multiplying the surface resistivity by the thickness. The resistivity of the transparent conductive layer 12 can be controlled, for example, by adjusting various conditions when the transparent conductive layer 12 is formed by sputtering (the same applies to the resistance values R1 and R2 described below). The conditions include, for example, the temperature of the base (transparent substrate 11 in this embodiment) on which the transparent conductive layer 12 is formed, the amount of oxygen introduced into the film formation chamber, the air pressure in the film formation chamber, and the horizontal magnetic field strength above the target.

From the viewpoint of reducing the resistance of the transparent conductive layer 12, the resistance value R1 of the transparent conductive layer 12 is, for example, 200 Ω/□ or less, preferably 100 Ω/□ or less, more preferably 70 Ω/□ or less, even more preferably 50 Ω/□ or less, even more preferably 45 Ω/□ or less, and particularly preferably 40 Ω/□ or less. The resistance value R1 is, for example, 1 Ω/□ or more. The resistance value R1 is the surface resistivity (the same applies to the resistance value R2 described below). The surface resistivity of the transparent conductive layer can be measured by a four-terminal method in accordance with JIS K7194 (1994). The measurement method of the resistance values R1 and R2 is specifically as described below in the examples.

The resistance value R2 of the transparent conductive layer 12 after heating at 140°C for 30 minutes is, from the viewpoint of reducing the resistance of the transparent conductive layer 12, for example, 200 Ω/□ or less, preferably 100 Ω/□ or less, more preferably 70 Ω/□ or less, even more preferably 50 Ω/□ or less, even more preferably 45 Ω/□ or less, and particularly preferably 40 Ω/□ or less. The resistance value R2 is, for example, 1 Ω/□ or more.

From the viewpoint of the resistance stability of the transparent conductive layer 12, the ratio of the resistance value R2 to the resistance value R1 (R2/R1) is, for example, 0.50 or more, preferably 0.70 or more, more preferably 0.80 or more, even more preferably 0.85 or more, particularly preferably 0.90 or more, and is preferably 1.0 or less.

From the viewpoint of the resistance stability of the transparent conductive layer 12, the difference |R1-R2| between the resistance value R1 and the resistance value R2 is, for example, 20 Ω/□ or less, preferably 10 Ω/□ or less, more preferably 7 Ω/□ or less, even more preferably 5 Ω/□ or less, even more preferably 3 Ω/□ or less, and particularly preferably 1 Ω/□ or less.

The total light transmittance (JIS K 7375-2008) of the transparent conductive film X is preferably 50% or more, more preferably 60% or more, even more preferably 80% or more, and even more preferably 85% or more. Such a configuration is suitable for ensuring the transparency required of the transparent conductive film X when the transparent conductive film X is provided in a touch sensor device, a light control element, a photoelectric conversion element, a heat ray control member, an antenna member, an electromagnetic wave shielding member, a heater member, a lighting device, an image display device, and the like. The total light transmittance of the transparent substrate 11 is, for example, 100% or less.

The transparent conductive film X is manufactured, for example, as follows.

First, a transparent substrate 11 is prepared. Next, a transparent conductive layer 12 is formed on the transparent substrate 11 (transparent conductive layer forming process). Specifically, a material is deposited on the transparent substrate 11 by a sputtering method to form the transparent conductive layer 12.

In the sputtering method, it is preferable to use a sputtering deposition apparatus capable of performing a film formation process by a roll-to-roll method. When using a roll-to-roll sputtering deposition apparatus in the manufacture of the transparent conductive film X, a material is deposited on the long transparent substrate 11 while the transparent substrate 11 is running from a pay-out roll to a take-up roll provided in the apparatus, to form the transparent conductive layer 12. In addition, in the sputtering method, a sputtering deposition apparatus having one deposition chamber may be used, or a sputtering deposition apparatus having multiple deposition chambers arranged in sequence along the running path of the transparent substrate 11 may be used.

Specifically, in the sputtering method, a sputtering gas (inert gas) is introduced under vacuum conditions into a deposition chamber equipped with a sputter deposition apparatus, while a negative voltage is applied to a target placed on a cathode in the deposition chamber. This generates a glow discharge to ionize gas atoms, and the gas ions collide with the target surface at high speed, ejecting the target material from the target surface, and depositing the ejected target material on the transparent substrate 11. For example, the sintered conductive oxide described above for the transparent conductive layer 12 is used as the target material. For example, argon and krypton are used as the sputtering gas.

The sputtering method is preferably a reactive sputtering method. In the reactive sputtering method, for example, oxygen is introduced into the deposition chamber as a reactive gas in addition to the sputtering gas. In the reactive sputtering method, the ratio of the amount of oxygen introduced to the total amount of sputtering gas and oxygen introduced into the deposition chamber is, for example, 0.01 flow rate% or more, and, for example, 15 flow rate% or less.

The air pressure in the film formation chamber during film formation by sputtering (sputter film formation) is, for example, 0.02 Pa or more, and, for example, 1 Pa or less. From the viewpoint of adjusting the water content of the transparent conductive layer 12, the water pressure in the film formation chamber is preferably 1.4×10 ⁻⁴ Pa or more, more preferably 1.5×10 ⁻⁴ Pa or more, even more preferably 1.6×10 ⁻⁴ Pa or more, particularly preferably 2.0×10 ⁻⁴ Pa or more, and is preferably 3.0×10 ⁻⁴ Pa or less, more preferably 2.7×10 ⁻⁴ Pa or less, and even more preferably 2.5×10 ⁻⁴ Pa or less. It is preferable that the water pressure in the film formation chamber is adjusted to be within such a range.

The temperature of the transparent substrate 11 during sputtering deposition is preferably 20°C or less, more preferably 10°C or less, even more preferably 5°C or less, even more preferably 0°C or less, and particularly preferably -2°C or less, from the viewpoint of suppressing outgassing from the transparent substrate 11 during sputtering deposition and appropriately forming the transparent conductive layer 12. The temperature is, for example, -50°C or more, -20°C or more, or -10°C or more.

Examples of power sources for applying voltage to the target include DC power sources, AC power sources, MF power sources, and RF power sources. A DC power source and an RF power source may be used in combination as the power source. The absolute value of the discharge voltage during sputtering deposition is, for example, 50 V or more, and, for example, 500 V or less.

Preferably, the series of processes from the transparent conductive layer formation process to the crystallization process described above is carried out on one continuous line while the work film is running in a roll-to-roll manner. More preferably, during the process on one continuous line, the work film is never exposed to the atmosphere.

In this manner, the transparent conductive film X can be manufactured. The long transparent conductive film X manufactured in this manner is provided, for example, as a roll-shaped transparent conductive film X (transparent conductive film roll). The length of such a transparent conductive film X is, for example, 10 m or more, preferably 50 m or more, more preferably 80 m or more, and preferably 5000 m or less, more preferably 3000 m or less. The width of the transparent conductive film X is, for example, 200 mm or more, preferably 500 mm or more, more preferably 1000 mm or more, and for example, 8000 mm or less, preferably 5000 mm or less, more preferably 3000 mm or less.

The transparent conductive layer 12 in the transparent conductive film X may be patterned as shown in FIG. 2. The transparent conductive layer 12 can be patterned by etching the transparent conductive layer 12 through a predetermined etching mask. The patterned transparent conductive layer 12 functions, for example, as a wiring pattern.

As described above, the transparent conductive film X has a transparent conductive layer 12 that includes amorphous regions and crystal grains. The transparent conductive layer 12 including amorphous regions and crystal grains is suitable for achieving both low resistance and suppression of cracking during bending in the transparent conductive layer 12 (amorphous transparent conductive layers 12 have high resistance, while crystalline transparent conductive layers 12 are prone to cracking). Furthermore, the transparent conductive film X has a hydrogen atom content of 2.0×10 ²⁰ cm ⁻³ or more in the transparent conductive layer 12. Such a transparent conductive film X is suitable for suppressing an increase in the resistance value of the transparent conductive layer 12 due to subsequent heating. Therefore, the transparent conductive film X is suitable for suppressing cracking during bending and an increase in the resistance value due to heating while reducing the resistance of the transparent conductive layer 12.

As shown in FIG. 3, the transparent conductive film X may further include a functional layer 13 between the transparent substrate 11 and the transparent conductive layer 12. The functional layer 13 is disposed, for example, on one surface of the transparent substrate 11 in the thickness direction H. The functional layer 13 is in contact with the transparent substrate 11. The functional layer 13 is also in contact with the transparent conductive layer 12. The functional layer 13 is, for example, a hard coat layer that makes it difficult for scratches to form on the exposed surface (the upper surface in FIG. 3) of the transparent conductive layer 12.

The hard coat layer is a cured product of a curable resin composition. The curable resin composition contains a curable resin. Examples of the curable resin include polyester resin, acrylic urethane resin, acrylic resin (excluding acrylic urethane resin), urethane resin (excluding acrylic urethane resin), amide resin, silicone resin, epoxy resin, and melamine resin. These curable resins may be used alone or in combination of two or more kinds. From the viewpoint of ensuring high hardness of the hard coat layer, at least one selected from the group consisting of acrylic urethane resin and acrylic resin is preferably used as the curable resin.

Examples of the curable resin include ultraviolet-curable resin and thermosetting resin. As the curable resin can be cured without high temperature heating, ultraviolet-curable resin is preferred from the viewpoint of improving the manufacturing efficiency of the transparent conductive film X.

The curable resin composition may contain particles. Examples of the particles include inorganic oxide particles and organic particles. Examples of materials for the inorganic oxide particles include silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide. Examples of materials for the organic particles include polymethyl methacrylate, polystyrene, polyurethane, acrylic-styrene copolymer, benzoguanamine, melamine, and polycarbonate.

The surface of the functional layer 13 facing the transparent conductive layer 12 may be subjected to a surface modification treatment. Examples of surface modification treatments include corona treatment, plasma treatment, ozone treatment, primer treatment, glow treatment, and coupling agent treatment.

The thickness of the functional layer 13 as a hard coat layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, from the viewpoint of providing sufficient scratch resistance in the transparent conductive layer 12. The thickness of the functional layer 13 as a hard coat layer is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less, from the viewpoint of ensuring the transparency of the functional layer 13.

The above-mentioned functional layer 13 as a hard coat layer can be formed by applying a curable resin composition to the transparent substrate 11 to form a coating film, and then curing the coating film. When the curable resin composition contains an ultraviolet-curable resin, the coating film is cured by ultraviolet irradiation. When the curable resin composition contains a thermosetting resin, the coating film is cured by heating.

The functional layer 13 may be an adhesion improving layer for realizing high adhesion of the transparent conductive layer 12 to the transparent substrate 11. The configuration in which the functional layer 13 is an adhesion improving layer is suitable for ensuring adhesion between the transparent substrate 11 and the transparent conductive layer 12.

The functional layer 13 may be an index-matching layer for adjusting the reflectance of the surface (one side in the thickness direction H) of the transparent substrate 11. The configuration in which the functional layer 13 is an index-matching layer is suitable for making the pattern shape of the transparent conductive layer 12 less visible when the transparent conductive layer 12 on the transparent substrate 11 is patterned.

The functional layer 13 may be a peelable functional layer that enables the transparent conductive layer 12 to be practically peeled off from the transparent substrate 11. A configuration in which the functional layer 13 is a peelable functional layer is suitable for peeling the transparent conductive layer 12 off from the transparent substrate 11 and transferring the transparent conductive layer 12 to another member.

The functional layer 13 may be a composite layer in which multiple layers are connected in the thickness direction H. The composite layer preferably includes two or more layers selected from the group consisting of a hard coat layer, an adhesion improving layer, a refractive index adjustment layer, and a release functional layer. Such a configuration is suitable for the functional layer 13 to exhibit the above-mentioned functions of each selected layer in a composite manner. In a preferred embodiment, the functional layer 13 includes an adhesion improving layer, a hard coat layer, and a refractive index adjustment layer on the transparent substrate 11, in this order toward one side of the thickness direction H. In another preferred embodiment, the functional layer 13 includes a release functional layer, a hard coat layer, and a refractive index adjustment layer on the transparent substrate 11, in this order toward one side of the thickness direction H.

The transparent conductive film X is used in a state where it is fixed to an article and the transparent conductive layer 12 is patterned as necessary. The transparent conductive film X is attached to the article, for example, via an adhesive functional layer.

Examples of the article include elements, members, and devices. That is, examples of the article with a transparent conductive film include an element with a transparent conductive film, a member with a transparent conductive film, and a device with a transparent conductive film.

The elements include, for example, dimming elements and photoelectric conversion elements. The dimming elements include, for example, current-driven dimming elements and electric field-driven dimming elements. The current-driven dimming elements include, for example, electrochromic (EC) dimming elements. The electric field-driven dimming elements include, for example, PDLC (polymer dispersed liquid crystal) dimming elements, PNLC (polymer network liquid crystal) dimming elements, and SPD (suspended particle device) dimming elements. The photoelectric conversion elements include, for example, solar cells. The solar cells include, for example, organic thin-film solar cells and dye-sensitized solar cells. The members include, for example, electromagnetic wave shielding members, heat ray control members, heater members, and antenna members. The devices include, for example, touch sensor devices, lighting devices, and image display devices.

The above-mentioned adhesive functional layer includes, for example, an adhesive layer and a bonding layer. The material of the adhesive functional layer is not particularly limited as long as it has transparency and exhibits an adhesive function. The adhesive functional layer is preferably formed from a resin. Examples of the resin include acrylic resin, silicone resin, polyester resin, polyurethane resin, polyamide resin, polyvinyl ether resin, vinyl acetate/vinyl chloride copolymer, modified polyolefin resin, epoxy resin, fluororesin, natural rubber, and synthetic rubber. The resin is preferably an acrylic resin because it exhibits adhesive properties such as cohesiveness, adhesion, and moderate wettability, is excellent in transparency, and has excellent weather resistance and heat resistance.

The adhesion functional layer (resin forming the adhesion functional layer) may contain a corrosion inhibitor to inhibit corrosion of the transparent conductive layer 12. The adhesion functional layer (resin forming the adhesion functional layer) may contain a migration inhibitor (e.g., a material disclosed in JP 2015-022397 A) to inhibit migration of the transparent conductive layer 12. The adhesion functional layer (resin forming the adhesion functional layer) may also contain an ultraviolet absorbing agent to inhibit deterioration during outdoor use of the article. Examples of ultraviolet absorbing agents include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalic acid anilide compounds, cyanoacrylate compounds, and triazine compounds.

In addition, when the transparent substrate 11 of the transparent conductive film X is fixed to an article via the adhesive functional layer, the transparent conductive layer 12 (including the transparent conductive layer 12 after patterning) is exposed in the transparent conductive film X. In such a case, a cover layer may be disposed on the exposed surface of the transparent conductive layer 12. The cover layer is a layer that covers the transparent conductive layer 12, and can improve the reliability of the transparent conductive layer 12 and suppress the deterioration of the function of the transparent conductive layer 12 due to damage. Such a cover layer is preferably formed from a dielectric material, and more preferably from a composite material of a resin and an inorganic material. Examples of the resin include the resins described above with respect to the adhesive functional layer. Examples of the inorganic material include inorganic oxides and fluorides. Examples of the inorganic oxide include silicon oxide, titanium oxide, niobium oxide, aluminum oxide, zirconium dioxide, and calcium oxide. Examples of the fluoride include magnesium fluoride. The cover layer (a mixture of resin and inorganic material) may also contain the above-mentioned corrosion inhibitors, migration inhibitors, and UV absorbers.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples. Furthermore, the specific numerical values of the compounding amounts (contents), physical property values, parameters, etc. described below can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than") of the corresponding compounding amounts (contents), physical property values, parameters, etc. described in the above-mentioned "Form for carrying out the invention."

Example 1
First, a roll of a long polyethylene terephthalate (PET) film (thickness 125 μm, manufactured by Mitsubishi Chemical Corporation) was prepared as a transparent substrate. The PET film had a width of 1500 mm and a predetermined length. Next, a transparent conductive layer having a thickness of 125 nm was formed on the PET film by reactive sputtering (sputtering film formation process). In this process, a roll-to-roll sputtering film formation device (DC magnetron sputtering film formation device) was used. The device is equipped with a film formation chamber that can perform a film formation process while running a work film by a roll-to-roll method. The conditions for sputtering film formation are as follows.

After the deposition chamber of the sputtering deposition apparatus was evacuated until the ultimate vacuum in the deposition chamber reached 0.9×10 ⁻⁴ Pa, argon as a sputtering gas and oxygen as a reactive gas were introduced into the deposition chamber, and the pressure in the deposition chamber was set to 0.2 Pa. The ratio of the amount of oxygen introduced to the total amount of argon and oxygen introduced into the deposition chamber was about 2.6 flow %. The average water pressure in the deposition chamber during sputtering deposition (average water pressure measured every 10 seconds) was 2.3×10 ⁻⁴ Pa. In addition, a sintered body of indium oxide and tin oxide (tin oxide concentration 12 mass %) was used as the target. A DC power supply was used as the power source for applying a voltage to the target. The horizontal magnetic field strength above the target was 30 mT. The deposition temperature (temperature of the transparent substrate on which the transparent conductive layer is laminated) was set to -3°C. The running speed of the PET film as the work film was 2.0 m/min.

In this manner, a roll of transparent conductive film (width 1500 mm, length 600 m) of Example 1 was produced.

Example 2
A roll-shaped transparent conductive film (width 1500 mm, length 600 m) of Example 2 was produced in the same manner as the transparent conductive film of Example 1, except that the average water pressure during sputtering was set to 2.0×10 ⁻⁴ Pa.

Example 3
A roll-shaped transparent conductive film (width 1500 mm, length 600 m) of Example 3 was produced in the same manner as the transparent conductive film of Example 1, except that the average water pressure during sputtering was 1.6×10 ⁻⁴ Pa.

Example 4
A roll-shaped transparent conductive film (width 1500 mm, length 600 m) of Example 4 was produced in the same manner as the transparent conductive film of Example 1, except that the average water pressure during sputtering was 1.4×10 ⁻⁴ Pa.

Comparative Example 1
A roll-shaped transparent conductive film (width 1500 mm, length 600 m) of Comparative Example 1 was produced in the same manner as the transparent conductive film of Example 1, except that the average water pressure during sputtering was 1.3×10 ⁻⁴ Pa.

Comparative Example 2
A transparent conductive film of Comparative Example 2 (width 1500 mm, length 600 m) was produced in the same manner as the transparent conductive film of Example 2, except that the oxygen introduction rate during sputtering deposition was set to about 1.1 flow %.

Comparative Example 3
A transparent conductive film of Comparative Example 3 was produced in the same manner as the transparent conductive film of Example 4, except for the following: The oxygen introduction rate during sputtering film formation was about 1.6 flow %. After the transparent conductive layer was formed by sputtering, the transparent conductive layer was heat-treated. In the heat treatment, the heating temperature was 140° C., and the heating time was 1 hour.

<Thickness of Transparent Conductive Layer>
The thickness of the transparent conductive layer of each of the transparent conductive films in Examples 1 to 4 and Comparative Examples 1 to 3 was measured by observation with a field emission transmission electron microscope (FE-TEM). Specifically, first, a cross-sectional observation sample of each of the transparent conductive layers in Examples 1 to 4 and Comparative Examples 1 to 3 was prepared by the FIB microsampling method. In the FIB microsampling method, an FIB device (product name "FB2200", manufactured by Hitachi) was used, and the acceleration voltage was set to 10 kV. Next, the cross-section of the transparent conductive layer in the cross-sectional observation sample was observed by FE-TEM, and the thickness of the transparent conductive layer was measured in the observed image. In the observation, an FE-TEM device (product name "JEM-2800", manufactured by JEOL) was used, and the acceleration voltage was set to 200 kV. The measurement results are shown in Table 1.

<Hydrogen content>
The hydrogen content of each transparent conductive layer in Examples 1 to 4 and Comparative Examples 1 to 3 was examined. Specifically, the hydrogen content was as follows.

First, nine sample collection films (films 1 to 9) were cut out from a long transparent conductive film. Each film had a size of 100 mm x 100 mm. The first film was cut out from a section at a position arbitrarily selected from within a region (tip region) 2 m from the tip in the length direction (flow direction) of the transparent conductive film, and from a position 100 mm away from one end to a position 200 mm away from one end in the film width direction. The second film was cut out from a section at a position 700 mm away from one end in the film width direction to a position 800 mm away in the tip region. The third film was cut out from a section at a position 1300 mm away from one end in the film width direction to a position 1400 mm away in the tip region. The fourth film was cut out from a section at a position arbitrarily selected from a region (middle region) 299 to 301 m from the tip in the length direction of the transparent conductive film, and from a position 100 mm away from one end in the film width direction to a position 200 mm away. The fifth film is cut out from a section in the intermediate region from a position 700 mm away from one end in the film width direction to a position 800 mm away from one end. The sixth film is cut out from a section in the intermediate region from a position 1300 mm away from one end in the film width direction to a position 1400 mm away from one end. The seventh film is cut out from a section at a position arbitrarily selected from within a region 2 m from the rear end (rear end region) in the length direction of the transparent conductive film, and from a position 100 mm away from one end in the film width direction to a position 200 mm away from one end. The eighth film is cut out from a section in the rear end region from a position 700 mm away from one end in the film width direction to a position 800 mm away from one end. The ninth film is cut out from a section in the rear end region from a position 1300 mm away from one end in the film width direction to a position 1400 mm away from one end in the film width direction.

Next, the hydrogen content of the transparent conductive layer in the sample film of a predetermined size cut out from the sample collection film was examined by dynamic SIMS. Specifically, a component analysis was performed in the thickness direction from the exposed surface of the transparent conductive layer to the surface on the transparent substrate side by time-of-flight secondary ion mass spectrometry (TOF-SIMS). A quadrupole secondary ion mass spectrometer (product name "PHI ADEPT-1010", manufactured by ULVAC-PHI, Inc.) was used for the analysis. In this analysis, cesium ions (Cs ⁺ ) were used as the primary ions irradiated as the ion beam, the acceleration voltage was set to 3.0 kV, and the detection area was set to the center of the ion beam irradiation area (78 μm x 78 μm). Then, from the result of the component analysis, the average value of the hydrogen atom content (number of hydrogen atoms per unit volume) in the area 10 to 115 nm deep from the exposed surface in the transparent conductive layer (thickness 125 nm) was calculated. For each transparent conductive layer, the minimum hydrogen atom content in the nine sample films derived from films 1 to 9 is shown as hydrogen content (cm ^-3 ) in Table 1. Hydrogen atoms (H) in the transparent conductive layer reflect the presence of water molecules (H ₂ O) in the transparent conductive layer. That is, the H content of the transparent conductive layer reflects the H ₂ O content of the transparent conductive layer.

<crystalline>
The crystallinity of each of the transparent conductive layers in Examples 1 to 4 and Comparative Examples 1 to 3 was examined. Specifically, the results are as follows.

First, a sample for observation was prepared. Specifically, from the sample collection film from which the sample film with the smallest hydrogen atom content was cut out of the nine sample films derived from the first to ninth films, a film of a predetermined size was cut out as a sample for observation. Then, the exposed surface of the transparent conductive layer of the sample for observation was observed with a field emission scanning electron microscope (product name "Regulus 8230", manufactured by Hitachi) (first observation). In this observation, the acceleration voltage was set to 0.8 kV. In addition, in this observation, the sample for observation was photographed in plan view at a magnification at which crystal grains with a maximum length of 30 nm or more could be clearly confirmed in the secondary electron image. Then, when crystal grains with a maximum length of 30 nm or more were confirmed, it was determined that the transparent conductive layer contained crystal grains (criterion for judgment). In each transparent conductive layer of Examples 1 to 4 and Comparative Example 1, both amorphous regions and a large number of crystal grains were confirmed. In the transparent conductive layer of Comparative Example 2, amorphous regions were confirmed, but no crystal grains with a maximum length of 30 nm or more were confirmed (areas other than those containing crystal grains with a maximum length of 30 nm or more were identified as amorphous regions). In the transparent conductive layer of Comparative Example 3, crystal grains with a maximum length of 30 nm or more were confirmed, but no amorphous regions were confirmed. The observation results are shown in Table 1.

After the above-mentioned first observation, the observation sample was heated in a hot air heating oven, and the exposed surface of the transparent conductive layer of the observation sample was observed with a field emission scanning electron microscope in the same manner as the first observation (second observation). In the heat treatment, the heating temperature was 140°C and the heating time was 30 minutes. The crystallinity in the transparent conductive layer after heating was judged using the same criteria as those described above. In each of the transparent conductive layers of Examples 1 to 4 and Comparative Examples 1 and 2, both amorphous regions and numerous crystal grains were confirmed. In the transparent conductive layer of Comparative Example 3, no amorphous regions were confirmed. The observation results are shown in Table 1.

<Resistance change due to heating>
The change in resistance value of the transparent conductive layer due to post-heating was examined for each of the transparent conductive films of Examples 1 to 4 and Comparative Examples 1 to 3. Specifically, the change is as follows.

First, a measurement sample was prepared. Specifically, from the sample collection film from which the sample film with the smallest hydrogen atom content was cut out of the nine sample films derived from films 1 to 9, a film measuring 100 mm x 50 mm was cut out as a measurement sample. Next, the resistance value R1 (surface resistivity before heat treatment) of the transparent conductive layer of the measurement sample was measured by the four-terminal method in accordance with JIS K 7194 (1994). Next, the measurement sample was heat-treated in a hot air heating oven. In the heat treatment, the heating temperature was 140°C and the heating time was 30 minutes. Next, the resistance value R2 (surface resistivity after heat treatment) of the transparent conductive layer of the measurement sample was measured by the four-terminal method in accordance with JIS K 7194 (1994). In addition, the ratio (R2/R1) of the resistance value R2 to the resistance value R1 was calculated. The resistance stability of the transparent conductive layer was evaluated as "good" when the ratio (R2/R1) was 0.6 or more and 1.0 or less, and as "poor" when the ratio (R2/R1) was less than 0.6 or more than 1.0. The results are shown in Table 1.

<Bending test>
A bending test was carried out on each of the transparent conductive films of Examples 1 to 4 and Comparative Examples 1 to 3. Specifically, the test was carried out as follows.

First, a test sample was prepared. Specifically, a film having a length of 100 mm and a width of 10 mm was cut out as a test sample from the sample collection film from which the sample film with the smallest hydrogen atom content was cut out of the nine sample films derived from the first to ninth films. Next, as shown in FIG. 4, the test sample 21 was set on a mandrel rod 22 having a diameter of 18 mm. The sample 21 was bent so that the transparent conductive layer was located on the outside of the bend. The ends 21a and 21b in the length direction of the sample 21 were fixed to a clip device 23. The distance between the ends 21a and 21b was substantially the same as the diameter of the mandrel rod 22. A weight 24 of 500 g was hung from the clip device 23. The sample 21 was left stationary for 10 seconds in the state shown in FIG. 4. Thereafter, the sample 21 was removed from the mandrel rod 22, and the clip device 23 was removed from the sample 21. The transparent conductive layer of the flattened sample 21 was then observed under an optical microscope to check for the presence or absence of cracks in the transparent conductive layer. Regarding the suppression of cracks in the transparent conductive layer, a case where no cracks were found in the transparent conductive layer by microscopic observation was evaluated as "good," and a case where cracks were found was evaluated as "poor." The evaluation results are shown in Table 1.

X: Transparent conductive film H: Thickness direction 11: Transparent substrate 12: Transparent conductive layer 13: Functional layer

Claims (2)

A transparent conductive film having a transparent substrate and a transparent conductive layer in this order in a thickness direction,
The transparent substrate is a resin film having a thickness of 1 μm or more and 500 μm or less,
the transparent conductive layer includes an amorphous region and crystal grains;
the transparent conductive layer is made of an indium tin composite oxide,
the transparent conductive layer contains 2.0×10 ²⁰ cm ⁻³ or more of hydrogen atoms,
A transparent conductive film, wherein the transparent conductive layer has a resistivity of 4.1×10 ⁻⁴ Ω·cm or more. 10. The transparent conductive film of claim 1, wherein the transparent conductive layer comprises amorphous regions and crystalline grains after heating at 140°C for 30 minutes.

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