JP7534374B2 - Method for producing transparent conductive film - Google Patents

Description

The present invention relates to a method for producing a transparent conductive film.

Conventionally, a transparent conductive film is known that includes 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 on a long substrate film by a roll-to-roll sputtering deposition apparatus (deposition process). In the deposition process, for example, after the deposition chamber of the sputtering deposition apparatus is depressurized, a conductive oxide film is formed by a reactive sputtering method on the substrate film passing through the deposition chamber. In the reactive sputtering method, a mixed gas of an inert gas and a reactive gas (oxygen, etc.) is introduced into the deposition chamber. Such a technology related to a transparent conductive film is described, for example, in Patent Document 1 below.

JP 2017-71850 A

Transparent conductive films may be exposed to a relatively high-temperature heating process during the manufacturing process of a device that includes the film. The transparent conductive layer of such transparent conductive films is required to have no or only a small increase in resistance due to subsequent heating. An increase in resistance of the transparent conductive layer of a transparent conductive film due to subsequent heating can cause poor characteristics of a device in which the transparent conductive film is incorporated.

Meanwhile, the present inventors have discovered the following about the manufacturing process of transparent conductive films. In the above-mentioned film formation process using the roll-to-roll method, the water pressure changes over time in the film formation chamber. The balance of the partial pressure of the reactive gas relative to the water pressure in the film formation chamber (corresponding to the quantitative balance between water and reactive gas in the film formation chamber) affects the presence and magnitude of an increase in the resistance value of the transparent conductive layer formed in the film formation chamber due to post-heating.

The present invention provides a method for producing a transparent conductive film that is suitable for suppressing an increase in the resistance value of a transparent conductive layer due to heating.

The present invention [1] is a method for producing a transparent conductive film having a long substrate film and a transparent conductive layer in order in the thickness direction, and includes a film-forming step of forming a transparent conductive layer on the substrate film under a reduced pressure atmosphere by a reactive sputtering method using a mixed gas containing an inert gas and a reactive gas, and the film-forming step includes decreasing the mixing ratio of the reactive gas to the inert gas after the water pressure in the reduced pressure atmosphere is decreased, and/or increasing the mixing ratio after the water pressure is increased.

The present invention [2] includes the method for producing a transparent conductive film described in [1] above, in which the transparent conductive layer has a thickness of 50 nm or more.

The present invention [3] includes the method for producing a transparent conductive film according to the above [1] or [2], in which the transparent conductive layer contains amorphous regions and crystal grains.

In the method for producing a transparent conductive film of the present invention, the film formation step includes, as described above, decreasing the mixing ratio of the reactive gas to the inert gas after the moisture pressure in the reduced pressure atmosphere is decreased, and/or increasing the mixing ratio after the moisture pressure is increased. Such a method for producing a transparent conductive film is suitable for ensuring a balance of the partial pressure of the reactive gas relative to the moisture pressure in the film formation chamber (corresponding to the quantitative balance between water and the reactive gas in the film formation chamber) in the film formation step. Therefore, the method for producing a transparent conductive film is suitable for suppressing an increase in the resistance value of the transparent conductive layer due to heating.

1A and 1B are process diagrams of one embodiment of a method for producing a transparent conductive film of the present invention, in which FIG. 1A shows a process of preparing a substrate film, and FIG. 1B shows a process of forming a transparent conductive layer on the substrate film. This illustrates a case where the transparent conductive layer in the transparent conductive film shown in FIG. 1B is patterned. FIG. 2 is a schematic cross-sectional view of a modified example of the transparent conductive film shown in FIG. 1B.

The method for producing a transparent conductive film according to one embodiment of the present invention includes a preparation step (FIG. 1A) and a film formation step (FIG. 1B). This method is a method for producing a transparent conductive film X shown in FIG. 1B. The transparent conductive film X includes a long substrate film 10 and a transparent conductive layer 20 in order in the thickness direction H. The transparent conductive film X extends in a direction (plane direction) perpendicular to the thickness direction H. The transparent conductive film X is an element included 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.

First, in the preparation step, a long base film 10 is prepared as shown in FIG. 1A. The length of the base film 10 is, for example, 50 m or more, and preferably 100 m or more. The length of the base film 10 is, for example, 20,000 m or less, and preferably 5,000 m or less. The width of the base film 10 is, for example, 200 mm or more, preferably 500 mm or more, and more preferably 1,000 mm or more. The width of the base film 10 is, for example, 3,000 mm or less, and preferably 2,000 mm or less.

The substrate film 10 is a substrate that ensures the strength of the transparent conductive film X. In this embodiment, the substrate film 10 is a transparent resin film having flexibility. Examples of the material of the substrate film 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 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 substrate film 10, for example, from the viewpoint of transparency and strength, polyester resin is preferably used, and more preferably PET is used.

The surface 10a of the substrate film 10 on which the transparent conductive layer 20 is formed 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 substrate film 10 is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 30 μm or more, from the viewpoint of ensuring the strength of the transparent conductive film X. The thickness of the substrate film 10 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, and particularly preferably 75 μm or less, from the viewpoint of ensuring the handleability of the substrate film 10 in the roll-to-roll method.

The total light transmittance (JIS K 7375-2008) of the substrate film 10 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 substrate film 10 is, for example, 100% or less.

Next, in the film formation process, as shown in FIG. 1B, a material is formed on the surface 10a (one side in the thickness direction H) of the base film 10 by a sputtering method to form a transparent conductive layer 20. In the sputtering method, a sputtering film formation device capable of performing the film formation process by a roll-to-roll method is used. The sputtering film formation device includes a pay-out roll for paying out the work film, a film formation chamber, and a take-up roll for winding up the work film, in this order in the flow direction of the work film. The inside of the film formation chamber can be reduced in pressure. In addition, the sputtering film formation device can measure the air pressure in the film formation chamber, and can measure the water pressure. In addition, a reactive sputtering method is performed as the sputtering method in this process. In the reactive sputtering method, a mixed gas containing an inert gas and a reactive gas is used as the sputtering gas.

Specifically, in the sputtering method of this process, the base film 10 is run as a work film from the pay-out roll to the take-up roll, while an inert gas and a reactive gas are introduced into the deposition chamber under a reduced pressure atmosphere, and 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 the ejected target material is deposited on the base film 10.

The air pressure inside the deposition chamber during deposition is, for example, 0.02 Pa or more, and, for example, 1 Pa or less.

Examples of the inert gas (sputtering gas) include argon and krypton. Examples of the reactive gas include oxygen and nitrogen monoxide. The reactive gas is selected according to the material forming the transparent conductive layer 20. When the material forming the transparent conductive layer 20 is a conductive oxide, oxygen is preferably used as the reactive gas. In addition, the ratio of the reactive gas to the inert gas (mixing ratio R) in the mixed gas at the start of film formation is, for example, 0.5 flow% or more, and, for example, 5 flow% or less (mixing ratio R is expressed as a percentage). The ratio of the reactive gas to the inert gas (mixing ratio R) is the ratio (F2/F1) of the introduction flow rate F2 (sccm) of the reactive gas (active gas) to the introduction flow rate F1 (sccm) of the inert gas, expressed as a percentage. The preferred range of the mixing ratio R varies depending on the water pressure Pw described below.

From the viewpoint of suppressing outgassing from the substrate film 10 during deposition and appropriately forming the transparent conductive layer 20, the temperature of the substrate film 10 during deposition is preferably 150°C or less, more preferably 70°C or less, even more preferably 40°C or less, even more preferably 10°C or less, and particularly preferably -5°C or less. 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 combination of DC power sources and RF power sources may be used as the power source. The absolute value of the discharge voltage during film formation is, for example, 50 V or more and, for example, 500 V or less. The horizontal magnetic field strength on the target is, for example, 10 mT or more and, for example, 100 mT or less.

From the viewpoint of the manufacturing efficiency of the transparent conductive film X, the running speed of the base film 10 is preferably 0.5 m/min or more, and more preferably 1 m/min or more. From the viewpoint of the appropriate formation of the transparent conductive layer 20, the running speed of the base film 10 is preferably 40 m/min or less, more preferably 10 m/min or less, even more preferably 5 m/min or less, and even more preferably 3 m/min or less.

Examples of the material (target material) for forming the transparent conductive layer 20 include conductive oxides. Examples of the conductive oxide include indium-containing conductive oxides and antimony-containing conductive oxides. Examples of the indium-containing conductive oxide 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 the antimony-containing conductive oxide include antimony tin composite oxide (ATO). From the viewpoint of achieving high transparency and good electrical conductivity, the conductive oxide is preferably an indium-containing conductive oxide, and more preferably ITO. This ITO may contain a metal or semimetal other than In and Sn in an amount 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 20 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 20. 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 suppressing the change in the resistance value of the transparent conductive layer 20 in a humid reliability test.

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 film formation.

In the film formation chamber during film formation, the water pressure changes over time. The causes of the change in water pressure include exhaust from the film formation chamber (cause of a decrease in water pressure) and water in the outgas from the work film (base film 10 in this embodiment) (cause of an increase in water pressure). From the viewpoint of adjusting the water content of the transparent conductive layer 20, the water pressure in the film formation chamber during film formation is preferably 0.1×10 ⁻⁴ Pa or more, more preferably 0.5×10 ⁻⁴ Pa or more, even more preferably 0.7×10 ⁻⁴ Pa or more, and even more preferably 0.9×10 ⁻⁴ Pa or more, and is preferably 5.0×10 ⁻² Pa or less, more preferably 5.0×10 ⁻³ Pa or less, even more preferably 3.0×10 ⁻⁴ Pa or less, even more preferably 2.7×10 ⁻⁴ Pa or less, and particularly preferably 2.5×10 ⁻⁴ Pa or less.

In this step, the water pressure Pw in the film formation chamber is measured. The measurement of the water pressure Pw includes the measurement of the water pressure _Pw0 at the start of film formation. The measurement of the water pressure Pw may be a continuous measurement or an intermittent measurement.

In the intermittent measurement, for example, the moisture pressure Pw in the film formation chamber is measured every time a predetermined length (length L ₁ ) of the substrate film 10 passes through the film formation chamber. The length L ₁ is preferably 1000 m or less, more preferably 800 m or less, and even more preferably 600 m or less, from the viewpoint of ensuring the monitoring accuracy of the moisture pressure Pw. The length L ₁ is, for example, 1 m or more, 10 m or more, or 100 m or more. The ratio (L ₁ /L ₀ ) of the length L ₁ to the total length (total length L ₀ ) of the transparent conductive film X is preferably 1/2 or less, more preferably 1/3 or less, and even more preferably 1/4 or less, from the viewpoint of ensuring the monitoring accuracy of the moisture pressure Pw. The ratio (L ₁ /L ₀ ) is, for example, 1/2000000 or more, 1/2000 or more, 1/500 or more, or 1/100 or more. In this process, the length L ₁ may be constant or may not be constant.

In the intermittent measurement, for example, the moisture pressure Pw in the film formation chamber through which the substrate film 10 passes continuously is measured at predetermined time intervals (time T). From the viewpoint of ensuring the monitoring accuracy of the moisture pressure Pw, the time T is preferably 30 minutes or less, more preferably 15 minutes or less, and even more preferably 5 minutes or less. The time T is, for example, 0.00001 minutes or more, 0.01 minutes or more, or 0.1 minutes or more. During this process, the time T may be constant or may not be constant.

The film formation process includes decreasing the reactive gas mixture ratio R (ratio of reactive gas to inert gas) after the water pressure Pw in the reduced pressure atmosphere is decreased, and/or increasing the mixture ratio R after the water pressure Pw is increased. This achieves a quantitative balance between the water and reactive gas in the film formation chamber (as described above, the quantitative balance between the water and reactive gas in the film formation chamber affects the presence and magnitude of an increase in resistance of the transparent conductive layer 20 formed in the film formation chamber due to post-heating). The first change (decrease or increase) of the mixture ratio R in the film formation process is performed as follows.

In the film formation chamber, a material is formed on the substrate film 10 by reactive sputtering under the condition of a mixture ratio _R0 (mixture ratio at the start of film formation) from the start of film formation in this process. Then, the water pressure _Pw1 measured by the first or multiple water pressure measurements after the start of film formation is compared with the water pressure _Pw0 at the start of film formation. When the water pressure _Pw1 is smaller than the water pressure _Pw0 (when the water pressure Pw has decreased), the mixture ratio R is decreased to a mixture ratio _R1 smaller than the mixture ratio _R0 . Alternatively, when the water pressure _Pw1 is larger than the water pressure Pw0 (when the water pressure Pw has increased), the mixture ratio R is increased to a mixture ratio _R1 larger _than the mixture ratio _R0 .

The first change (reduction or increase) of the mixing ratio R in the film formation process is implemented as described above based on the difference between the water pressure _Pw0 at the start of film formation and the water pressure _Pw1 measured at a predetermined timing. Similarly, the nth change (reduction or increase) of the mixing ratio R is implemented based on the difference between the water pressure Pwn _-1 measured at a predetermined timing and the water pressure _Pwn measured at a subsequent predetermined timing.

When oxygen is used as a reactive gas to form an ITO layer as the transparent conductive layer 20, the surface resistance of the transparent conductive layer 20 formed in the film formation process changes according to the change in the amount of oxygen introduced (oxygen partial pressure) into the film formation chamber (i.e., the surface resistance of the transparent conductive layer 20 shows dependency on the amount of oxygen introduced). Specifically, the surface resistance of the transparent conductive layer 20 shows a parabolic dependency with a minimum value with respect to the amount of oxygen introduced. The amount of oxygen introduced (oxygen partial pressure) at which the surface resistance of the transparent conductive layer 20 takes the minimum value tends to increase as the water pressure in the film formation chamber increases (it tends to decrease as the water pressure in the film formation chamber decreases). In such a film formation process, for example, the above mixture ratio R is increased or decreased according to the increase or decrease in the water pressure in the film formation chamber so that the surface resistance of the transparent conductive layer 20 takes the minimum value or a value close to it.

When the water pressure Pw decreases by 0.1×10 ^-4 Pa (Pw _n - Pw _n-1 = -0.1×10 ^-4 ), the mixing ratio R is decreased by, for example, 0.05 flow rate %, preferably by 0.1 flow rate %. When the water pressure Pw increases by 0.1×10 ^-4 Pa (Pw _n - Pw _n-1 = 0.1×10 ^-4 ), the mixing ratio R is increased by, for example, 0.05 flow rate %, preferably by 0.1 flow rate %.

When the water pressure Pw in the film formation chamber is 0.9×10 ⁻⁴ Pa, the mixture ratio R is preferably 1.8 flow% or more, more preferably 2.0 flow% or more, and also preferably 2.3 flow% or less, more preferably 2.1 flow% or less. When the water pressure Pw in the film formation chamber is 1.0×10 ⁻⁴ Pa, the mixture ratio R is preferably 1.9 flow% or more, more preferably more than 2.1 flow%, and also preferably 2.3 flow% or less, more preferably 2.2 flow% or less. When the water pressure Pw in the film formation chamber is 1.1×10 ⁻⁴ Pa or more and less than 1.4×10 ⁻⁴ Pa, the mixture ratio R is preferably 2.0 flow% or more, more preferably more than 2.2 flow%, and also preferably 2.5 flow% or less, more preferably 2.3 flow% or less. When the water pressure Pw in the deposition chamber is 1.4×10 ⁻⁴ Pa or more and 1.7×10 ⁻⁴ Pa or less, the mixture ratio R is preferably 2.1 flow % or more, more preferably more than 2.3 flow %, and is preferably 2.6 flow % or less, more preferably 2.5 flow % or less.

In the film formation process, the transparent conductive layer 20 is formed from the leading end region to the trailing end region of the substrate film 10 while controlling the mixture ratio R as described above. This allows the transparent conductive film X to be manufactured.

The transparent conductive layer 20 has both optical transparency and electrical conductivity. The transparent conductive layer 20 preferably contains amorphous regions and crystal grains. The crystal grains are crystal grains with a maximum length of 30 nm or more. The inclusion of amorphous regions and crystal grains in the transparent conductive layer 20 is suitable for achieving both low resistance and suppression of cracking when bent in the transparent conductive layer 20 (amorphous transparent conductive layers have high resistance, while crystalline transparent conductive layers are prone to cracking). The inclusion of amorphous regions and crystal grains in the transparent conductive layer (transparent conductive layer 20 on the substrate film 10 in the transparent conductive film X) can be determined, for example, by observing the transparent conductive layer with a field emission scanning electron microscope (FE-SEM).

From the viewpoint of reducing the resistance of the transparent conductive layer 20, the thickness of the transparent conductive layer 20 is preferably 50 nm or more, more preferably 70 nm or more, and even more preferably 80 nm or more. In addition, from the viewpoint of suppressing cracking due to heating in the transparent conductive layer 20, the thickness of the transparent conductive layer 20 is preferably 350 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less.

From the viewpoint of reducing the resistance of the transparent conductive layer 20, the resistance value R1 of the transparent conductive layer 20 is preferably 100 Ω/□ or less, more preferably 70 Ω/□ or less, even more preferably 50 Ω/□ or less, and even more preferably 45 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 specific method of measuring the resistance values R1 and R2 is as described below in the examples.

From the viewpoint of reducing the resistance of the transparent conductive layer 20, the resistance value R2 of the transparent conductive layer 20 after heating at 140°C for 30 minutes is 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, even more preferably 40 Ω/□ or less, and particularly preferably 38 Ω/□ or less. The resistance value R2 is, for example, 1 Ω/□ or more.

The difference R1-R2 between the resistance value R1 and the resistance value R2 is, for example, 30 Ω/□ or less, preferably 15 Ω/□ or less, more preferably 13 Ω/□ or less, and even more preferably 10 Ω/□ or less, from the viewpoint of suppressing an increase in the resistance value due to heating of the transparent conductive layer 20 (a negative value of the difference R1-R2 means that the resistance value has increased).

From the viewpoint of the resistance stability of the transparent conductive layer 20, the ratio of the resistance value R2 to the resistance value R1 (R2/R1) is, for example, 0.55 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.

The total light transmittance (JIS K 7375-2008) of the transparent conductive film X 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 substrate film 10 is, for example, 100% or less.

The transparent conductive layer 20 in the transparent conductive film X may be patterned as shown in FIG. 2. The transparent conductive layer 20 can be patterned by etching the transparent conductive layer 20 through a predetermined etching mask. The patterned transparent conductive layer 20 functions, for example, as a wiring pattern.

In the method for producing a transparent conductive film, the balance of the partial pressure of the reactive gas (oxygen in this embodiment) relative to the moisture pressure in the film formation chamber (corresponding to the quantitative balance between the water and the reactive gas in the film formation chamber) affects the presence and magnitude of the increase in the resistance value of the transparent conductive layer 20 formed in the film formation chamber due to post-heating. In the method for producing a transparent conductive film, the film formation process (FIG. 1B) includes, as described above, decreasing the mixture ratio R of the reactive gas to the inert gas after the moisture pressure Pw in the reduced pressure atmosphere is decreased, and/or increasing the mixture ratio R after the moisture pressure Pw is increased. Such a method for producing a transparent conductive film is suitable for ensuring the balance of the partial pressure of the inert gas relative to the moisture pressure Pw in the film formation process. Therefore, the method for producing a transparent conductive film is suitable for suppressing the increase in the resistance value of the transparent conductive layer 20 due to heating. Specifically, as shown in the examples and comparative examples described below.

As shown in FIG. 3, the base film 10 of the transparent conductive film X may include a resin film 11 and a functional layer 12. Examples of materials for the resin film 11 include the materials described above as the materials for the base film 10. The functional layer 12 is disposed on one side of the resin film 11 in the thickness direction H. The functional layer 12 is in contact with the resin film 11. The functional layer 12 is also in contact with the transparent conductive layer 20. The functional layer 12 is, for example, a hard coat layer that makes it difficult for scratches to form on the exposed surface (upper surface in FIG. 3) of the transparent conductive layer 20.

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 12 facing the transparent conductive layer 20 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 12 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 20. The thickness of the functional layer 12 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 12.

The functional layer 12 described above as a hard coat layer can be formed by applying a curable resin composition onto the resin film 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 12 may be an adhesion improving layer for realizing high adhesion of the transparent conductive layer 20 to the resin film 11. The configuration in which the functional layer 12 is an adhesion improving layer is suitable for ensuring adhesion between the resin film 11 and the transparent conductive layer 20.

The functional layer 12 may be an index-matching layer for adjusting the reflectance of the surface (one side in the thickness direction H) of the base film 10. The configuration in which the functional layer 12 is an index-matching layer is suitable for making the pattern shape of the transparent conductive layer 20 on the base film 10 less visible when the transparent conductive layer 20 is patterned.

The functional layer 12 may be a peelable functional layer that allows the transparent conductive layer 20 to be practically peeled off from the substrate film 10. A configuration in which the functional layer 12 is a peelable functional layer is suitable for peeling the transparent conductive layer 20 from the substrate film 10 and transferring the transparent conductive layer 20 to another member.

The functional layer 12 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 12 to exhibit the above-mentioned functions of each selected layer in a composite manner. In a preferred embodiment, the functional layer 12 includes an adhesion improving layer, a hard coat layer, and a refractive index adjustment layer on the resin film 11, in this order toward one side of the thickness direction H. In another preferred embodiment, the functional layer 12 includes a release functional layer, a hard coat layer, and a refractive index adjustment layer on the resin film 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 20 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 20. 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 20. 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 base film 10 of the transparent conductive film X is fixed to an article via the adhesive functional layer, the transparent conductive layer 20 (including the transparent conductive layer 20 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 20. The cover layer is a layer that covers the transparent conductive layer 20, and can improve the reliability of the transparent conductive layer 20 and suppress the deterioration of the function of the transparent conductive layer 20 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 polyethylene terephthalate (PET) film (thickness: 125 μm, manufactured by Mitsubishi Chemical Corporation) was prepared as a long substrate film. The PET film had a length of 2000 meters and a width of 1500 mm.

Next, a 125 nm thick transparent conductive layer was formed on the PET film by reactive sputtering (film formation process). In this process, a roll-to-roll sputtering film formation device (DC magnetron sputtering film formation device) was used. This device is equipped with a film formation chamber in which the film formation process can be carried out while the work film is running by the roll-to-roll method. The conditions for sputtering film formation are as follows:

The deposition chamber of the sputtering deposition apparatus was evacuated until the ultimate vacuum in the deposition chamber reached 0.9×10 ⁻⁴ Pa, and then a mixed gas of argon as a sputtering gas (inert gas) and oxygen as a reactive gas was introduced into the deposition chamber, and the pressure in the deposition chamber was set to 0.2 Pa. The mixture ratio R of oxygen to argon gas in the mixed gas (the ratio of the amount of oxygen introduced to the amount of argon introduced into the deposition chamber) was 2.4 flow rate % (12 sccm of oxygen to 500 sccm of argon). As the target, a sintered body of indium oxide and tin oxide (tin oxide concentration of 12 mass %) was used. As the power source for applying a voltage to the target, a DC power source was used. The horizontal magnetic field strength above the target was 30 mT. The deposition temperature (the temperature of the substrate film on which the transparent conductive layer is laminated) was set to −3° C. The running speed of the substrate film was set to 2.0 m/min. Under the above conditions, a PET film was run as a work film, while in the film formation chamber, a film of indium tin oxide (ITO) was formed on the PET film to continue forming a transparent conductive layer. During the film formation process, the water pressure Pw in the film formation chamber was measured every 10 seconds. The water pressure _Pw0 at the start of film formation was 1.5× ^10-4 Pa.

After the start of film formation, the water pressure in the film formation chamber gradually decreased, and the water pressure Pw during film formation at a point 600 m from the end of the PET film became 1.1×10 ⁻⁴ Pa (first time point). During film formation at a point 600 m from the end of the PET film (immediately after the first time point), the oxygen mixture ratio R was changed from 2.4 flow rate % to 2.3 flow rate % (first change).

After the first change in the oxygen mixing ratio R, the water pressure in the film formation chamber gradually decreased, and the water pressure Pw during film formation at a point 1200 meters from the front end of the PET film (second time point) became 1.0×10 ⁻⁴ Pa. During film formation at a point 1200 meters from the front end of the PET film (immediately after the second time point), the oxygen mixing ratio R was changed from 2.3 flow % to 2.2 flow % (second change).

After the second change in the oxygen mixing ratio R, the water pressure in the film formation chamber gradually decreased, and the water pressure Pw during film formation at a point 1700 meters from the front end of the PET film became 0.91×10 ⁻⁴ Pa (third time point). During film formation at a point 1700 meters from the front end of the PET film (immediately after the third time point), the oxygen mixing ratio R was changed from 2.2 flow rate % to 2.1 flow rate % (third change).

In this manner, a roll of transparent conductive film (length 2,000 meters, width 1,500 mm) of Example 1 was produced.

Comparative Example 1
A roll-shaped transparent conductive film of Comparative Example 1 (length 2000 meters, width 1500 mm) was produced in the same manner as the transparent conductive film of Example 1, except that the oxygen mixing ratio R in the film formation process was maintained at 2.4 flow rate %.

<Thickness of Transparent Conductive Layer>
The thickness of the transparent conductive layer of each transparent conductive film in Example 1 and Comparative Example 1 was measured by observation with a field emission transmission electron microscope (FE-TEM). Specifically, first, a cross-sectional observation sample of each transparent conductive layer in Example 1 and Comparative Example 1 was prepared by FIB microsampling. 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.

<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 Example 1 and Comparative Example 1. Specifically, the change is as follows.

First, 12 sample films (sample films 1 to 12) for measuring resistance were cut out from a long transparent conductive film. Each sample film had a size of 50 mm (lengthwise dimension of the transparent conductive film) x 100 mm (widthwise dimension of the transparent conductive film). The first sample film was cut out from a section within a region (tip region) 50 m from the tip of the transparent conductive film in the lengthwise direction, and from a position 200 mm away from one end (the right end of the film facing the film running direction) to a position 300 mm away in the widthwise direction of the transparent conductive film. The widthwise center position of the first sample film was a position 250 mm away from one end in the widthwise direction of the transparent conductive film (the same applies to the widthwise center positions of the fourth, seventh, and tenth sample films described below). The second sample film was cut out from a section within the tip region, from a position 700 mm away from one end in the widthwise direction of the transparent conductive film to a position 800 mm away. The width direction center position of the second sample film is a position 750 mm away from one end in the width direction of the transparent conductive film (the same applies to the width direction center positions of the fifth, eighth and eleventh sample films described below). The third sample film is cut out from a section in the tip region, from a position 1200 mm away from one end in the width direction of the transparent conductive film to a position 1300 mm away. The width direction center position of the third sample film is a position 1250 mm away from one end in the width direction of the transparent conductive film (the same applies to the width direction center positions of the sixth, ninth and twelfth sample films described below). The fourth sample film is cut out from a section in a region (first intermediate region) 600 to 650 m from the tip in the length direction of the transparent conductive film, from a position 200 mm away from one end in the width direction of the transparent conductive film to a position 300 mm away from one end in the width direction of the transparent conductive film. The fifth sample film was cut out from a section in the first intermediate region from a position 700 mm away from one end in the width direction of the transparent conductive film to a position 800 mm away from one end. The sixth sample film was cut out from a section in the first intermediate region from a position 1200 mm away from one end in the width direction of the transparent conductive film to a position 1300 mm away from one end. The seventh sample film was cut out from a section in a region (second intermediate region) 1200 to 1250 m from the tip in the length direction of the transparent conductive film, and from a position 200 mm away from one end in the width direction of the transparent conductive film to a position 300 mm away from one end. The eighth sample film was cut out from a section in the second intermediate region from a position 700 mm away from one end in the width direction of the transparent conductive film to a position 800 mm away from one end. The ninth sample film was cut out from a section in the second intermediate region from a position 1200 mm away from one end in the width direction of the transparent conductive film to a position 1300 mm away from one end in the width direction of the transparent conductive film. The tenth sample film was cut from a section within the third intermediate region, which is 1700 to 1750 m from the leading end of the transparent conductive film in the longitudinal direction, and from a section 200 mm to 300 mm away from one end in the width direction of the transparent conductive film. The eleventh sample film was cut from a section within the third intermediate region, which is 700 mm to 800 mm away from one end in the width direction of the transparent conductive film. The twelfth sample film was cut from a section within the third intermediate region, which is 1200 mm to 1300 mm away from one end in the width direction of the transparent conductive film.

Next, the resistance value R1 (surface resistivity before heat treatment) of the transparent conductive layer of the sample film was measured by the four-terminal method according to JIS K 7194 (1994). Next, the sample film 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 sample film was measured by the four-terminal method according to JIS K 7194 (1994). In addition, the difference R1-R2 between the resistance value R1 and the resistance value R2 was calculated. Then, regarding the suppression of the increase in the resistance value of the transparent conductive layer, if the difference R1-R2 was 0.0 or more (if the resistance value did not increase), it was evaluated as "good", and if the difference R1-R2 was less than 0.0 (if the resistance value increased), it was evaluated as "poor". These results are shown in Table 1. In addition, in Table 1, for each resistance value, the difference from the resistance value of the tip region at the same position in the film width direction (the amount of change in resistance value in the length direction of the transparent conductive film) is shown in brackets. At the resistance value R1 of the transparent conductive film of Example 1, the maximum amount of change in resistance value in the length direction was 6 Ω/□. At the resistance value R2 of the transparent conductive film of Example 1, the maximum amount of change in resistance value in the length direction was 3 Ω/□. At the resistance value R1 of the transparent conductive film of Comparative Example 1, the maximum amount of change in resistance value in the length direction was 10 Ω/□. At the resistance value R2 of the transparent conductive film of Comparative Example 1, the maximum amount of change in resistance value in the length direction was 20 Ω/□.

X: transparent conductive film H: thickness direction 10: substrate film 11: resin film 12: functional layer 20: transparent conductive layer

Claims (4)

A method for producing a transparent conductive film having a long substrate film and a transparent conductive layer in that order in a thickness direction, comprising:
The method includes a film-forming step of forming a transparent conductive layer on a substrate film under a reduced pressure atmosphere by a reactive sputtering method using a mixed gas containing an inert gas and a reactive gas,
The water pressure in the reduced pressure atmosphere is 1.5×10 ⁻⁴ Pa or less,
In the film forming process, a mixing ratio of the reactive gas to the inert gas is changed,
The method for producing a transparent conductive film, wherein the change in the mixing ratio includes decreasing the mixing ratio of the reactive gas to the inert gas after the water pressure in the reduced pressure atmosphere is reduced. The method for producing a transparent conductive film according to claim 1, wherein the width of the substrate film is 1000 mm or more. The method for producing a transparent conductive film according to claim 1, wherein the transparent conductive layer has a thickness of 50 nm or more. The method for producing a transparent conductive film according to claim 1 , wherein the transparent conductive layer comprises amorphous regions and crystal grains.

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