Transparent conductive film and method for manufacturing same

Abstract

The purpose of the present invention is to provide a transparent conductive film that is capable of achieving a low resistance value by maintaining a low resistivity even when the film thickness of a transparent electrode layer made of a conductive oxide is increased, and is not susceptible to cracks occurring during bending.　A transparent conductive film 1 in which a transparent electrode layer 40 mainly composed of indium oxide is formed on a flexible substrate 30, wherein: the transparent electrode layer 40 has a film thickness of 100 nm or more; the transparent electrode layer 40 is formed by laminating a plurality of regions; regions 40a, 40c having a nitrogen content of less than 0.6 at % are present above and below a region 40b having a nitrogen content of 0.6 at % or more; and the thickness of the region 40b having a nitrogen content of 0.6 at % or more is smaller than the total thickness of the regions 40a, 40c having a nitrogen content of less than 0.6 at %.

Description

Transparent conductive film and method for producing the same

[0001] The present invention relates to a transparent conductive film in which a transparent electrode layer is formed on a flexible substrate, and a method for producing the same.

[0002] Transparent conductive films have traditionally been widely used in touch panels, solar cells, light-control devices, and other devices. However, in recent years, there has been a demand for lower resistance due to the need for larger device areas and faster response times.

[0003] In response to such demands for lower resistance in transparent conductive films, attempts have been made to lower resistance by combining a transparent electrode material made of conductive oxide with a metal material such as a metal mesh of silver or copper, but the use of a metal material in combination with the film sometimes limits its applications due to the deterioration of reliability and durability.

[0004] International Publication No. 2016 / 163323

[0005] In light of the above, increasing the thickness of the transparent electrode layer made of conductive oxide was considered as a means of reducing the resistance of transparent conductive films without using metal materials. However, simply increasing the thickness of the transparent electrode layer resulted in an increase in resistivity, making it impossible to achieve the expected low resistance value. Furthermore, the transparent electrode layer of a transparent conductive film must be resistant to cracking when the film is bent. This requirement is particularly strong for transparent conductive films used in flexible devices, but increasing the thickness of the transparent electrode layer also posed a problem, as cracks tended to occur more easily.

[0006] The present invention aims to provide a transparent conductive film that can achieve a low resistance value by maintaining low resistivity even when the film thickness of a transparent electrode layer made of a conductive oxide is increased, and that is less likely to crack when bent.

[0007] Specific means for solving the above problems include the following embodiments. <1> A transparent conductive film comprising a transparent electrode layer containing indium oxide as a main component formed on a flexible substrate, wherein the transparent electrode layer has a film thickness of 100 nm or more, the transparent electrode layer is formed by laminating a plurality of regions, and regions having a nitrogen content of less than 0.6 at% exist above and below regions having a nitrogen content of 0.6 at% or more, and the thickness of the regions having a nitrogen content of 0.6 at% or more is smaller than the total thickness of the regions having a nitrogen content of less than 0.6 at%. <2> The transparent conductive film according to <1>, wherein the thickness of the regions having a nitrogen content of 0.6 at% or more is 40 nm or less. <3> The transparent conductive film according to <1> or <2>, wherein the transparent electrode layer has a structure in which a first transparent electrode layer a1, an intermediate layer b1, and a second transparent electrode layer c1 are laminated in this order; the first transparent electrode layer a1 is a region where the nitrogen content is 0.6 at% or less that is located closer to the substrate than the intermediate layer b1 and has a film thickness of 30 nm or more; and the intermediate layer b1 is a region where the nitrogen content is 0.6 at% or more. <4> The transparent conductive film according to <3>, wherein the intermediate layer b1 is an amorphous layer. <5> The method for producing the transparent conductive film according to <3>, wherein the intermediate layer b1 is formed by sputtering using a target mainly composed of indium oxide in an atmosphere having a volume ratio of a carrier gas to a nitrogen gas of 250:10 to 250:300. <6> The method for producing the transparent conductive film according to <5>, wherein film formation conditions are set so that the designed film thickness of the intermediate layer b1 is 25 nm or less. <7> The transparent conductive film according to <1>, wherein the transparent electrode layer has a structure in which a first transparent electrode layer a2, an intermediate layer b2, and a second transparent electrode layer c2 are laminated in this order, the first transparent electrode layer a2 is located closer to the substrate than the intermediate layer b2, is a region having a nitrogen content of ½ or less of the maximum nitrogen content in the transparent electrode layer, and has a film thickness of 30 nm or more, and the intermediate layer b2 is a region having a nitrogen content of ½ or more of the maximum nitrogen content in the transparent electrode layer, and has a film thickness of 40 nm or less.<8> The transparent conductive film according to <7>, wherein the intermediate layer b2 is an amorphous layer. <9> The method for producing a transparent conductive film according to <7>, wherein the intermediate layer b2 is formed by sputtering using a target containing indium oxide as a main component in an atmosphere having a volume ratio of a carrier gas to a nitrogen gas of 250:10 to 250:300. <10> The method for producing a transparent conductive film according to <9>, wherein film formation conditions are set so that a designed film thickness of the intermediate layer b2 is 25 nm or less.

[0008] According to the present invention, even when the film thickness of the transparent electrode layer made of a conductive oxide is increased, a low resistivity is maintained, thereby making it possible to provide a transparent conductive film that can achieve a low resistance value and is less likely to crack when bent.

[0009] 1 is a schematic cross-sectional view of one embodiment of the transparent conductive film of the present invention. 2 is a diagram showing the nitrogen content of the transparent electrode layer measured in an evaluation test.

[0010] Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0011] (Transparent Conductive Film 1) A transparent conductive film 1 as one embodiment of the transparent conductive film of the present invention is formed by laminating a transparent electrode layer 40 on a flexible substrate 30, as shown in FIG.

[0012] (Substrate 30) The substrate 30 has flexibility, and can be formed by laminating a functional layer 20 such as a hard coat layer or an optical adjustment layer on one or both surfaces of the transparent resin substrate 10, for example.

[0013] (Transparent Resin Substrate 10) The transparent resin substrate 10 is a substrate that ensures the strength of the transparent conductive film 1. The transparent resin substrate 10 can be a flexible, transparent resin film. Examples of materials for the transparent resin substrate 10 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 polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resins include polyethylene, polypropylene, and cycloolefin polymer. Examples of acrylic resins include polymethacrylate. As the material for the resin substrate, polyester resin is preferably used, and PET is more preferably used, from the viewpoints of transparency and strength, for example.

[0014] The surface of the transparent resin substrate 10 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.

[0015] The thickness of the transparent resin substrate 10 is preferably 10 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more, from the viewpoint of ensuring the strength of the transparent conductive film 1. The thickness of the transparent resin substrate 10 is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less, from the viewpoint of ensuring the handleability of the transparent resin substrate 10 in a roll-to-roll system.

[0016] (Functional Layer 20) The substrate 30 can have a functional layer 20 on one or both sides of the transparent resin substrate 10. The functional layer 20 may be a single layer or multiple layers. A layer that imparts a desired function to the transparent conductive film can be appropriately selected and used as the functional layer 20. Examples of layers that constitute the functional layer 20 include an optical adjustment layer, an anti-reflection layer, an anti-glare layer, an easy-adhesion layer, a stress buffer layer, a hard coat layer, an easy-slip layer, an antistatic layer, a crystallization promotion layer, a crystallization rate adjustment layer, and a coating layer.

[0017] An example of a case where the functional layer 20 is a multi-layer structure is a combination of a hard coat layer and an optical adjustment layer. The hard coat layer may be laminated on at least one side of the transparent resin substrate 10, and may be laminated on both sides as needed. The hard coat layer can impart good chemical resistance and contamination resistance. The optical adjustment layer is a layer that adjusts the optical properties of the transparent conductive film 1 to suppress the pattern visibility of the transparent electrode layer 40 and ensure excellent transparency in the transparent conductive film 1.

[0018] The hard coat layer can be formed, for example, by applying an ultraviolet-curable resin such as an acrylic resin to the surface of the transparent resin substrate 10 and curing it by ultraviolet irradiation. The optical adjustment layer can be formed, for example, by applying a diluted solution of the optical adjustment composition to the surface of the hard coat layer, drying it, and then curing the optical adjustment composition by ultraviolet irradiation.

[0019] (Transparent Electrode Layer 40) The transparent electrode layer 40 is a transparent layer that exhibits excellent conductivity. The transparent electrode layer 40 can be formed on the functional layer 20.

[0020] The transparent electrode layer 40 contains indium oxide as a main component. Examples of compounds containing indium oxide include indium-containing oxides such as indium tin composite oxide (ITO), indium gallium composite oxide (IGO), indium zinc composite oxide (IZO), and indium gallium zinc composite oxide (IGZO). These composite oxides can impart uniform conductivity to the entire surface of the transparent electrode layer 40 and are preferable from the standpoint of a balance between transparency and resistance. The main component refers to the component that is contained in the transparent electrode layer 40 at the highest ratio.

[0021] When the transparent electrode layer 40 contains ITO formed from indium oxide and tin oxide, the content of tin oxide in the ITO is preferably 8% by mass or more, and more preferably 10% by mass or more, relative to the total amount of tin oxide and indium oxide, from the viewpoint of low resistivity and stable film quality. To achieve low resistance through crystallization of the ITO, the content is preferably 20% by mass or less, and more preferably 15% by mass or less. Furthermore, from the viewpoint of improving crystallinity, a portion of the transparent electrode layer having a tin oxide content of 10% by mass or less or 8% by mass or less may be provided.

[0022] Materials other than those mentioned above may be combined for the transparent electrode layer 40. Materials to be combined with the transparent electrode layer 40 include, without particular limitation, inorganic materials containing oxides or nitrides of tin, zinc, titanium, aluminum, or the like as components, carbon-based materials such as graphene, carbon nanotubes, fullerene, and diamond-like carbon, and organic transparent conductive materials such as PEDOT, as long as they satisfy the required characteristics of the device.

[0023] The film thickness of the transparent electrode layer 40 is 100 nm or more, preferably 150 nm or more, and more preferably 200 nm or more, from the viewpoint of ensuring high conductivity. On the other hand, from the viewpoint of optical properties and crack resistance, it is preferably 500 nm or less, more preferably 350 nm or less, and particularly preferably 250 nm or less. Therefore, the film thickness of the transparent electrode layer 40 is preferably 100 nm or more and 500 nm or less, more preferably 150 nm or more and 350 nm or less, and particularly preferably 200 nm or more and 250 nm or less. The film thickness of the transparent electrode layer 40 can be measured by cross-sectional observation using, for example, a transmission electron microscope (TEM).

[0024] 1 , the transparent electrode layer 40 is formed by stacking a plurality of regions, with a region 40a having a nitrogen content of less than 0.6 at% above a region 40b having a nitrogen content of 0.6 at% or more, and a region 40c having a nitrogen content of less than 0.6 at% below the region 40b having a nitrogen content of 0.6 at% or more. By arranging the regions 40a and 40c having a nitrogen content of less than 0.6 at% above and below the region 40b having a nitrogen content of 0.6 at% or more, it is possible to maintain low resistivity even when the film thickness of the transparent electrode layer 40 is increased.

[0025] The nitrogen content in the region 40a where the nitrogen content is less than 0.6 at% is preferably 0.1 at% or less, more preferably 0.05 at% or less, and particularly preferably 0.02 at% or less.

[0026] The nitrogen content in the region 40b having a nitrogen content of 0.6 at% or more is preferably 1 at% or more and 15 at% or less, more preferably 1.5 at% or more and 10 at% or less, and particularly preferably 2 at% or more and 5 at% or less.

[0027] The nitrogen content in the region 40c having a nitrogen content of less than 0.6 at% is preferably 0.1 at% or less, more preferably 0.05 at% or less, and particularly preferably 0.02 at% or less.

[0028] The thickness of the region 40b having a nitrogen content of 0.6 at % or more is smaller than the total thickness of the regions 40a and 40c having a nitrogen content of less than 0.6 at %.

[0029] The thickness of the region 40b having a nitrogen content of 0.6 at% or more is preferably 40 nm or less, more preferably 2 nm or more and 40 nm or less, even more preferably 4 nm or more and 30 nm or less, and particularly preferably 5 nm or more and 20 nm or less. If nitrogen diffuses over a wide range in the film, the resistance values ​​of the first transparent electrode layer a1 and the second transparent electrode layer c1 may increase, so it is preferable that the nitrogen element is concentrated in a limited region near the intermediate layer b1.

[0030] The thickness of each region can be measured by secondary ion mass spectrometry (SIMS). Hereinafter, unless otherwise specified, the numerical values ​​of the thickness of each region and the film thickness of each layer in the transparent electrode layer represent the numerical values ​​measured by SIMS.

[0031] The thickness of the region 40a having a nitrogen content of less than 0.6 at % is preferably 30 nm or more and 200 nm or less, more preferably 40 nm or more and 150 nm or less, and particularly preferably 50 nm or more and 120 nm or less.

[0032] The thickness of the region 40c having a nitrogen content of less than 0.6 at % is preferably 30 nm or more and 200 nm or less, more preferably 40 nm or more and 150 nm or less, and particularly preferably 50 nm or more and 120 nm or less.

[0033] The total thickness of the regions 40a, 40c having a nitrogen content of less than 0.6 at % is preferably 100 nm or more and 400 nm or less, more preferably 100 nm or more and 300 nm or less, and particularly preferably 100 nm or more and 250 nm or less.

[0034] The transparent electrode layer 40 can be formed by laminating a first transparent electrode layer a, an intermediate layer b, and a second transparent electrode layer c in this order.

[0035] As will be described later, when forming each of the first transparent electrode layer a1, intermediate layer b1, and second transparent electrode layer c1, by adjusting the nitrogen content of each layer, it is possible to form a structure in which there are regions with a nitrogen content of less than 0.6 at% above and below regions with a nitrogen content of 0.6 at% or more.

[0036] The first transparent electrode layer a1 forms a region 40c that is located closer to the substrate than the intermediate layer b1 and has a nitrogen content of 0.6 at% or less. The first transparent electrode layer a1 preferably has a film thickness of 30 nm or more, more preferably 40 nm to 150 nm, and particularly preferably 50 nm to 120 nm. If the first transparent electrode layer a1 is too thin, the crystallinity of the film may deteriorate, making it difficult to achieve low resistance, while if the first transparent electrode layer a1 is too thick, the effects of the intermediate layer b1 may be difficult to achieve.

[0037] The intermediate layer b1 forms a region 40b having a nitrogen content of 0.6 at% or more. The thickness of the intermediate layer b1 is preferably 40 nm or less, more preferably 4 nm or more to 30 nm or less, and particularly preferably 5 nm or more to 20 nm or less. If the intermediate layer b1 is too thin, it becomes difficult to exhibit the effects of low resistance and crack resistance, and if the intermediate layer b1 is too thick, transparency may be impaired. Therefore, the thickness of the intermediate layer b1 is preferably within the above range.

[0038] If the intermediate layer b1 is an amorphous layer, it is preferable because it can reliably prevent cracks from occurring when the sheet is bent.

[0039] The second transparent electrode layer c1 forms a region 40a in which the nitrogen content is 0.6 at% or less. The second transparent electrode layer c1 preferably has a film thickness of 40 nm or more and 150 nm or less, and particularly preferably 50 nm or more and 120 nm or less. If the second transparent electrode layer c1 is too thin, the crystallinity of the film may deteriorate, making it difficult to achieve low resistance. If the second transparent electrode layer c1 is too thick, the effect of the intermediate layer b1 may be difficult to achieve. Furthermore, in order to maximize the effect of the intermediate layer b1, it is more preferable that the thicknesses of the first transparent electrode layer a1 and the second transparent electrode layer c1 are similar.

[0040] The first transparent electrode layer a2 is located closer to the substrate than the intermediate layer b2, and is a region where the nitrogen content is half or less of the maximum nitrogen content in the transparent electrode layer, and its film thickness is 30 nm or more. The intermediate layer b2 is a region where the nitrogen content is half or more of the maximum nitrogen content in the transparent electrode layer, and its film thickness is preferably 40 nm or less, more preferably 2 nm or more to 40 nm or less, even more preferably 4 nm or more to 30 nm or less, and particularly preferably 5 nm or more to 20 nm or less. If nitrogen diffuses over a wide range in the film, it may increase the resistance value of the first transparent electrode layer a2 and the second transparent electrode layer c2, so it is preferable that the nitrogen element is concentrated in a limited region near the intermediate layer b2.

[0041] Furthermore, if the intermediate layer b2 is an amorphous layer, it is possible to reliably prevent cracks from occurring when the sheet is bent, which is preferable.

[0042] By disposing a base transparent electrode layer on the substrate-side surface inside the first transparent electrode layer a, the transparent electrode layer can have a structure in which the first transparent electrode layer a including the base transparent electrode layer, the intermediate layer b, and the second transparent electrode layer c are stacked in this order.

[0043] The underlying transparent electrode layer preferably has a film thickness of 10 nm or less, more preferably 2 nm to 8 nm, and particularly preferably 3 nm to 6 nm. By providing the underlying transparent electrode layer, the influence of impurity gases from the substrate can be reduced, and a transparent electrode layer with low resistance as a whole can be obtained. If the underlying transparent electrode layer is too thin, it becomes difficult to reduce the influence of impurity gases, and if it is too thick, the transparency of the transparent electrode layer may be impaired.

[0044] The transparent electrode layer may be formed by further laminating the intermediate layer b, the first transparent electrode layer a, the second transparent electrode layer c, or the like on the second transparent electrode layer c as appropriate.

[0045] (Formation of Transparent Electrode Layer 40) The transparent electrode layer 40 is formed by sputtering using a target containing indium oxide as a main component.

[0046] When transparent electrode layer 40 is formed using ITO as a target, the sintered density of ITO is preferably 99% or more from the viewpoint of discharge stability.

[0047] The sputtering system used can be a batch system, a roll-to-roll system, or the like, without any particular limitation, but from the viewpoint of productivity, it is preferable to use a take-up sputtering system and perform the sputtering in a roll-to-roll system. The power source used for sputtering film formation is not particularly limited, and a DC power source, an MF power source, an RF power source, or the like can be used, but from the viewpoint of improving productivity, a DC power source or an MF power source is preferred, and a DC power source is particularly preferred.

[0048] It is known that water molecules are adsorbed in a chamber that is open to the atmosphere. The water molecules in the chamber are taken into the film during the formation of the transparent electrode layer, and can be a factor in increasing the resistance. Therefore, after the film substrate is placed in the sputtering deposition apparatus, it is preferable to evacuate the chamber and reduce the water pressure in the chamber before forming the transparent electrode layer. The water pressure in the chamber is 1×10 －３ Pa or less is preferable, and 1×10 －４ Pa or less is more preferable.

[0049] The substrate may be heated or cooled during sputtering depending on the purpose. If the thermal load on the substrate due to sputtering is large, the substrate may be cooled, or sputtering may be performed while heating the substrate in order to improve the film quality of the transparent electrode layer.

[0050] The transparent electrode layer 40 can be formed by laminating in this order the base transparent electrode layer, the portion of the first transparent electrode layer a excluding the base transparent electrode layer, the intermediate layer b, and the second transparent electrode layer c, and when forming multiple layers, sputtering may be performed by repeatedly discharging using the same target, or may be performed by using an apparatus comprising multiple targets and transporting them in a single operation. When an apparatus comprising multiple targets is used, the targets can be placed in separate deposition chambers, making it easier to control the pressure, etc.

[0051] Film formation by sputtering is carried out by introducing a carrier gas containing argon gas and oxygen gas, or argon gas only, into a film formation chamber, and further introducing nitrogen gas as a doping gas. The pressure in the film formation chamber can be adjusted by the amount of carrier gas and nitrogen gas introduced. The pressure (total pressure) in the film formation chamber is preferably 0.1 Pa to 1.0 Pa, more preferably 0.25 Pa to 0.80 Pa.

[0052] Nitrogen doping into the intermediate layer b can be efficiently carried out by introducing nitrogen gas into the deposition chamber. The nitrogen content of the intermediate layer b can be adjusted by the volume ratio of the carrier gas and nitrogen gas introduced into the deposition chamber. The volume ratio of the carrier gas and nitrogen gas can be controlled using a control device such as a pressure adjustment mechanism and / or a flow rate control mechanism.

[0053] In forming the underlying transparent electrode layer, it is preferable to use only a carrier gas. From the viewpoint of reducing damage to the substrate, it is preferable not to add oxygen gas. Furthermore, from the viewpoint of improving the crystallinity of the film, it is preferable not to add nitrogen gas.

[0054] In forming the first transparent electrode layer (a), it is preferable to use only a carrier gas and oxygen gas. Adding an appropriate amount of oxygen gas can improve crystallinity and reduce resistance. The volume ratio of the carrier gas to the oxygen gas is 500:1 to 250:25, preferably 250:1 to 250:20, more preferably 250:2 to 250:15, and particularly preferably 250:2 to 250:10.

[0055] In forming the intermediate layer (b), it is preferable to use only a carrier gas and nitrogen gas to make the intermediate layer (b) amorphous. The volume ratio of the carrier gas to the nitrogen gas is 250:10 to 250:300, preferably 250:30 to 250:250, more preferably 250:50 to 250:200, and particularly preferably 250:70 to 250:150. The designed film thickness of the intermediate layer (b) is preferably 25 nm or less.

[0056] Here, the designed film thickness is calculated from the discharge power during sputtering, the substrate transport speed, and the total film thickness of the transparent electrode layer when forming each layer in the transparent electrode layer. Therefore, except for the total designed film thickness, the designed film thickness of each layer does not necessarily match the value measured by TEM or SIMS.

[0057] In forming the second transparent electrode layer (c), it is preferable to use only a carrier gas and oxygen gas. Adding an appropriate amount of oxygen gas can improve crystallinity and reduce resistance. Furthermore, by using a higher pressure than the first transparent electrode layer (a), cracking of the transparent electrode layer can be suppressed. The volume ratio of the carrier gas to the oxygen gas is preferably 500:1 to 500:50, more preferably 500:1 to 500:40, even more preferably 500:1 to 500:30, and particularly preferably 500:2 to 500:20.

[0058] The transparent electrode layer 40 formed by sputtering is primarily an amorphous layer, but annealing is preferred because it increases the crystallinity, thereby reducing resistivity and improving transmittance. The annealing temperature is preferably 120 to 220°C, and more preferably 130 to 180°C. If the annealing temperature is too low, the time required for crystallization will be long, reducing productivity, while if it is too high, the temperature will exceed the heat resistance temperature of the substrate, making it impossible to maintain the shape of the film.

[0059] (Uses of Transparent Conductive Film) The transparent conductive film of the present invention can be used as a transparent electrode for displays, light-emitting devices, photoelectric conversion devices, and the like.

[0060] Example 1 A 125 μm thick optical PET film (Lumirror, manufactured by Toray Industries, Inc.) was used as a substrate, and a 2 μm thick hard coat layer was formed on both sides of the film using an ultraviolet curable resin (Lioduras TYAB, manufactured by Toyochem Co., Ltd.). The hard coat was formed by applying a UV curable resin coating solution diluted with methyl isobutyl ketone (MIBK) using a bar coater, drying in a hot air drying oven at 80°C for 1 minute, and then irradiating the film with 400 mJ / cm using a high-pressure mercury lamp. ２This step was carried out on both sides to obtain a film with a hard coat layer, in which a hard coat layer was formed on both sides of the substrate.

[0061] Subsequently, an optical adjustment layer was formed on one side of the PET film with the hard coat layer. A UV-curable resin coating liquid for the optical adjustment layer (Lioduras TYZ, manufactured by Toyochem Co., Ltd.) with a refractive index of 1.65 was diluted with MIBK and applied by bar coating. The coating was dried in a hot air drying oven at 80°C for 1 minute, and then irradiated with 600 mJ / cm using a high-pressure mercury lamp. ２ The coating film was cured by irradiation with ultraviolet light of 1000 kJ / cm. The optical adjustment layer thus obtained had a film thickness of 40 nm.

[0062] Subsequently, a transparent electrode layer made of ITO was formed on the optical adjustment layer of the film with the optical adjustment layer by sputtering. After the film with the optical adjustment layer was placed in a roll-to-roll sputtering device, it was transported at room temperature while the water pressure in the chamber was 1×10 －４ The chamber was then evacuated to a vacuum of 0.4 Pa. Next, using ITO (tin oxide content 10.0% by mass) as a target, only argon was introduced so that the pressure inside the chamber was 0.4 Pa, and pre-sputtering was performed for 15 minutes at a discharge power of 1.0 kW. After that, while the film was being transported so that the design film thickness of the underlying transparent electrode layer was 6 nm, sputtering was performed using a DC power supply at a discharge power of 0.2 kW, thereby forming an underlying transparent electrode layer.

[0063] Next, argon and oxygen were supplied at a ratio of 250:3, and under conditions of a chamber pressure of 0.3 Pa, the film was transported so that the design film thickness of the first transparent electrode layer a, excluding the underlying transparent electrode layer, was 100 nm, and sputtering was performed using a DC power supply with a discharge power of 1.0 kW to form the first transparent electrode layer a.

[0064] Subsequently, only argon and nitrogen were supplied so that the ratio of argon to nitrogen was 250:80, and the film was transported under conditions of a chamber pressure of 0.4 Pa so that the design film thickness of intermediate layer b was 6 nm. Intermediate layer b was then formed by sputtering using a DC power supply with a discharge power of 0.2 kW.

[0065] Next, oxygen was supplied to give a ratio of argon:oxygen of 500:3, and under conditions of a chamber pressure of 0.6 Pa, the film was transported so that the design film thickness of the second transparent electrode layer c was 100 nm, and sputtering was performed using a DC power supply with a discharge power of 1.0 kW to form the second transparent electrode layer c.

[0066] The obtained transparent conductive film was further annealed in a hot air drying oven at 140° C. for 90 minutes, and then subjected to various evaluations.

[0067] Example 2 A transparent conductive film was produced in the same manner as in Example 1, except that the flow rate of nitrogen was changed so that the ratio of argon to nitrogen was 250:50 when forming the intermediate layer b.

[0068] Example 3 A transparent conductive film was produced in the same manner as in Example 1, except that the flow rate of nitrogen was changed so that the ratio of argon to nitrogen was 250:30 when forming the intermediate layer b.

[0069] Example 4 A transparent conductive film was produced in the same manner as in Example 1, except that the flow rate of nitrogen was changed so that the ratio of argon to nitrogen was 250:10 when forming the intermediate layer b.

[0070] Example 5 A transparent conductive film was produced in the same manner as in Example 1, except that the design film thickness of each of the first transparent electrode layer a and the second transparent electrode layer c, excluding the underlying transparent electrode layer, was set to 73 nm.

[0071] Example 6 A transparent conductive film was produced in the same manner as in Example 1, except that the first transparent electrode layer a and the second transparent electrode layer c, excluding the underlying transparent electrode layer, had a designed film thickness of 50 nm each.

[0072] Comparative Example 1 A transparent conductive film was produced in the same manner as in Example 1, except that nitrogen was not introduced when the intermediate layer b was formed.

[0073] Comparative Example 2 A transparent conductive film was produced in the same manner as in Example 1, except that the flow rate of nitrogen was changed so that the ratio of argon to nitrogen was 250:4 when forming the intermediate layer b.

[0074] Comparative Example 3 A transparent conductive film was produced in the same manner as in Example 1, except that the intermediate layer b was not formed.

[0075] (Comparative Example 4) A transparent conductive film was produced in the same manner as in Example 1, except that the first transparent electrode layer a and the intermediate layer b, excluding the underlying transparent electrode layer, were not formed, and the design film thickness of the second transparent electrode layer c was set to 200 nm.

[0076] (Reference Example 1) A transparent conductive film was produced in the same manner as in Example 1, except that the first transparent electrode layer a and the intermediate layer b, excluding the base transparent electrode layer, were not formed, and the design film thickness of the second transparent electrode layer c was set to 146 nm.

[0077] (Reference Example 2) A transparent conductive film was produced in the same manner as in Example 1, except that the first transparent electrode layer a and the intermediate layer b, excluding the underlying transparent electrode layer, were not formed, and the design film thickness of the second transparent electrode layer c was set to 100 nm.

[0078] (Evaluation Methods) The transparent conductive films of Examples 1 to 6, Comparative Examples 1 to 4, and Reference Examples 1 and 2 were evaluated by the following evaluation methods.

[0079] The maximum nitrogen concentration in the transparent electrode layer was measured by dynamic SIMS using an ADEPT1010 manufactured by PHI Corporation under the conditions of primary ion species Cs+, primary ion energy 2 eV, and secondary ion polarity Negative, with N as the element of interest. Measurement values ​​were detected every 0.7 nm, and the detection sensitivity of N was converted based on the sensitivity in ZnO. The conversion to at% was performed using an ITO density of 7.12 g / cm. ３ The measurements were carried out under the assumption that the electron gun was used for charge compensation during the measurements.

[0080] The film thickness of the transparent electrode layer was measured by cross-sectional TEM analysis.

[0081] The design thickness of each layer in the transparent electrode layer was calculated by proportional allocation from the total film thickness, assuming that the film thickness is proportional to the discharge power during sputtering and inversely proportional to the substrate transport speed. Changes in film formation speed due to gas conditions were not taken into consideration. Note that, because the nitrogen contained in intermediate layer b diffuses into the upper and lower layers during the film formation and annealing processes, the thickness of the region where the nitrogen concentration is 0.6 at% or higher, the half-width of the nitrogen concentration, and the thickness of the amorphous region do not necessarily match the design film thickness of intermediate layer b.

[0082] The sheet resistance of the transparent conductive film was calculated in accordance with JIS K7194 using Loresta GP manufactured by Mitsubishi Chemical Corporation.

[0083] The total light transmittance of the transparent conductive film was measured in accordance with JIS K7361 using a turbidity meter NDH7000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0084] The bending resistance of the transparent conductive film was evaluated by cutting a transparent conductive film into a 50 mm x 10 mm strip with the MD direction as the long side, wrapping it around a pin gauge with the transparent electrode layer facing inward, and holding it for 30 seconds, then visually checking for the occurrence of cracks. If no cracks occurred, the same test was repeated with the thickness of the pin gauge wrapped around it reduced by 1 mm each time, and the diameter of the smallest pin gauge that did not cause cracks was recorded as the minimum bending diameter.

[0085]

[0086] As shown in Table 1, it was confirmed that Examples 1 to 6 exhibited good resistivity and were less likely to crack when bent.

[0087] Furthermore, as shown in FIG. 2 , it was confirmed that in Examples 1 and 3, regions in which the nitrogen content was less than 0.6 at% existed above and below the region in which the nitrogen content was 0.6 at% or more in the transparent electrode layer, whereas in Comparative Example 1, the presence of a region in which the nitrogen content was 0.6 at% or more could not be confirmed.

[0088] The transparent conductive film of the present invention can be suitably used in applications requiring low resistance, such as light control elements, touch sensors, liquid crystal elements, photoelectric conversion elements, heat ray control members, antennas, electromagnetic wave shielding members, and image display devices.

[0089] REFERENCE SIGNS LIST 1 transparent conductive film 10 transparent resin substrate 20 functional layer 30 substrate 40 transparent electrode layer 40a region with nitrogen content less than 0.6 at% 40b region with nitrogen content of 0.6 at% or more 40c region with nitrogen content less than 0.6 at%

Claims

1. A transparent conductive film in which a transparent electrode layer containing indium oxide as a main component is formed on a flexible substrate, the transparent electrode layer having a film thickness of 100 nm or more, the transparent electrode layer being formed by laminating a plurality of regions, with regions having a nitrogen content of less than 0.6 at% present above and below regions having a nitrogen content of 0.6 at% or more, and the thickness of the regions having a nitrogen content of 0.6 at% or more being smaller than the total thickness of the regions having a nitrogen content of less than 0.6 at%.

2. The transparent conductive film according to claim 1, wherein the thickness of the region having a nitrogen content of 0.6 at % or more is 40 nm or less.

3. The transparent conductive film according to claim 1, wherein the transparent electrode layer comprises a structure in which a first transparent electrode layer a1, an intermediate layer b1, and a second transparent electrode layer c1 are laminated in this order, the first transparent electrode layer a1 is a region that is located closer to the substrate than the intermediate layer b1 and has a nitrogen content of 0.6 at% or less and has a film thickness of 30 nm or more, and the intermediate layer b1 is a region that has a nitrogen content of 0.6 at% or more.

4. The transparent conductive film according to claim 3, wherein the intermediate layer b1 is an amorphous layer.

5. A method for producing a transparent conductive film according to claim 3, wherein the intermediate layer b1 is formed by sputtering using a target containing indium oxide as a main component in an atmosphere in which the volume ratio of carrier gas to nitrogen gas is 250:10 to 250:

300.

6. The method for producing a transparent conductive film according to claim 5, wherein the film-forming conditions are set so that the designed film thickness of the intermediate layer b1 is 25 nm or less.

7. The transparent conductive film according to claim 1, wherein the transparent electrode layer comprises a structure in which a first transparent electrode layer a2, an intermediate layer b2, and a second transparent electrode layer c2 are laminated in this order, the first transparent electrode layer a2 being located closer to the substrate than the intermediate layer b2, being a region having a nitrogen content of 1 / 2 or less of the maximum nitrogen content in the transparent electrode layer, and having a film thickness of 30 nm or more, and the intermediate layer b2 being a region having a nitrogen content of 1 / 2 or more of the maximum nitrogen content in the transparent electrode layer, and having a film thickness of 40 nm or less.

8. The transparent conductive film according to claim 7, wherein the intermediate layer b2 is an amorphous layer.

9. A method for producing a transparent conductive film according to claim 7, wherein the intermediate layer b2 is formed by sputtering using a target containing indium oxide as a main component in an atmosphere in which the volume ratio of carrier gas to nitrogen gas is 250:10 to 250:

300.

10. The method for producing a transparent conductive film according to claim 9, wherein the film-forming conditions are set so that the designed film thickness of the intermediate layer b2 is 25 nm or less.

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